path: root/src/nxt_router.c

/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Valentin V. Bartenev
 * Copyright (C) NGINX, Inc.
 */

#include <nxt_router.h>
#include <nxt_conf.h>
#if (NXT_TLS)
#include <nxt_cert.h>
#endif
#include <nxt_http.h>
#include <nxt_port_memory_int.h>
#include <nxt_unit_request.h>
#include <nxt_unit_response.h>
#include <nxt_router_request.h>

typedef struct {
    nxt_str_t         type;
    uint32_t          processes;
    uint32_t          max_processes;
    uint32_t          spare_processes;
    nxt_msec_t        timeout;
    nxt_msec_t        res_timeout;
    nxt_msec_t        idle_timeout;
    uint32_t          requests;
    nxt_conf_value_t  *limits_value;
    nxt_conf_value_t  *processes_value;
    nxt_conf_value_t  *targets_value;
} nxt_router_app_conf_t;


typedef struct {
    nxt_str_t         pass;
    nxt_str_t         application;
} nxt_router_listener_conf_t;


#if (NXT_TLS)

typedef struct {
    nxt_str_t          name;
    nxt_socket_conf_t  *conf;

    nxt_queue_link_t   link;  /* for nxt_socket_conf_t.tls */
} nxt_router_tlssock_t;

#endif


typedef struct {
    nxt_socket_conf_t       *socket_conf;
    nxt_router_temp_conf_t  *temp_conf;
} nxt_socket_rpc_t;


typedef struct {
    nxt_app_t               *app;
    nxt_router_temp_conf_t  *temp_conf;
} nxt_app_rpc_t;


struct nxt_port_select_state_s {
    nxt_app_t               *app;
    nxt_request_app_link_t  *req_app_link;

    nxt_port_t              *failed_port;
    int                     failed_port_use_delta;

    uint8_t                 start_process;    /* 1 bit */
    nxt_request_app_link_t  *shared_ra;
    nxt_port_t              *port;
};

typedef struct nxt_port_select_state_s nxt_port_select_state_t;

static nxt_int_t nxt_router_prefork(nxt_task_t *task, nxt_process_t *process,
    nxt_mp_t *mp);
static nxt_int_t nxt_router_start(nxt_task_t *task, nxt_process_data_t *data);
static void nxt_router_greet_controller(nxt_task_t *task,
    nxt_port_t *controller_port);

static void nxt_router_port_select(nxt_task_t *task,
    nxt_port_select_state_t *state);

static nxt_int_t nxt_router_port_post_select(nxt_task_t *task,
    nxt_port_select_state_t *state);

static nxt_int_t nxt_router_start_app_process(nxt_task_t *task, nxt_app_t *app);
static void nxt_request_app_link_update_peer(nxt_task_t *task,
    nxt_request_app_link_t *req_app_link);


nxt_inline void
nxt_request_app_link_inc_use(nxt_request_app_link_t *req_app_link)
{
    nxt_atomic_fetch_add(&req_app_link->use_count, 1);
}

nxt_inline void
nxt_request_app_link_chk_use(nxt_request_app_link_t *req_app_link, int i)
{
#if (NXT_DEBUG)
    int  c;

    c = nxt_atomic_fetch_add(&req_app_link->use_count, i);

    nxt_assert((c + i) > 0);
#else
    (void) nxt_atomic_fetch_add(&req_app_link->use_count, i);
#endif
}

static void nxt_request_app_link_use(nxt_task_t *task,
    nxt_request_app_link_t *req_app_link, int i);

static nxt_router_temp_conf_t *nxt_router_temp_conf(nxt_task_t *task);
static void nxt_router_conf_apply(nxt_task_t *task, void *obj, void *data);
static void nxt_router_conf_ready(nxt_task_t *task,
    nxt_router_temp_conf_t *tmcf);
static void nxt_router_conf_error(nxt_task_t *task,
    nxt_router_temp_conf_t *tmcf);
static void nxt_router_conf_send(nxt_task_t *task,
    nxt_router_temp_conf_t *tmcf, nxt_port_msg_type_t type);

static nxt_int_t nxt_router_conf_create(nxt_task_t *task,
    nxt_router_temp_conf_t *tmcf, u_char *start, u_char *end);
static nxt_int_t nxt_router_conf_process_static(nxt_task_t *task,
    nxt_router_conf_t *rtcf, nxt_conf_value_t *conf);
static nxt_app_t *nxt_router_app_find(nxt_queue_t *queue, nxt_str_t *name);
static void nxt_router_listen_socket_rpc_create(nxt_task_t *task,
    nxt_router_temp_conf_t *tmcf, nxt_socket_conf_t *skcf);
static void nxt_router_listen_socket_ready(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);
static void nxt_router_listen_socket_error(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);
#if (NXT_TLS)
static void nxt_router_tls_rpc_create(nxt_task_t *task,
    nxt_router_temp_conf_t *tmcf, nxt_router_tlssock_t *tls);
static void nxt_router_tls_rpc_handler(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);
#endif
static void nxt_router_app_rpc_create(nxt_task_t *task,
    nxt_router_temp_conf_t *tmcf, nxt_app_t *app);
static void nxt_router_app_prefork_ready(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);
static void nxt_router_app_prefork_error(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);
static nxt_socket_conf_t *nxt_router_socket_conf(nxt_task_t *task,
    nxt_router_temp_conf_t *tmcf, nxt_str_t *name);
static nxt_int_t nxt_router_listen_socket_find(nxt_router_temp_conf_t *tmcf,
    nxt_socket_conf_t *nskcf, nxt_sockaddr_t *sa);

static nxt_int_t nxt_router_engines_create(nxt_task_t *task,
    nxt_router_t *router, nxt_router_temp_conf_t *tmcf,
    const nxt_event_interface_t *interface);
static nxt_int_t nxt_router_engine_conf_create(nxt_router_temp_conf_t *tmcf,
    nxt_router_engine_conf_t *recf);
static nxt_int_t nxt_router_engine_conf_update(nxt_router_temp_conf_t *tmcf,
    nxt_router_engine_conf_t *recf);
static nxt_int_t nxt_router_engine_conf_delete(nxt_router_temp_conf_t *tmcf,
    nxt_router_engine_conf_t *recf);
static nxt_int_t nxt_router_engine_joints_create(nxt_router_temp_conf_t *tmcf,
    nxt_router_engine_conf_t *recf, nxt_queue_t *sockets,
    nxt_work_handler_t handler);
static nxt_int_t nxt_router_engine_quit(nxt_router_temp_conf_t *tmcf,
    nxt_router_engine_conf_t *recf);
static nxt_int_t nxt_router_engine_joints_delete(nxt_router_temp_conf_t *tmcf,
    nxt_router_engine_conf_t *recf, nxt_queue_t *sockets);

static nxt_int_t nxt_router_threads_create(nxt_task_t *task, nxt_runtime_t *rt,
    nxt_router_temp_conf_t *tmcf);
static nxt_int_t nxt_router_thread_create(nxt_task_t *task, nxt_runtime_t *rt,
    nxt_event_engine_t *engine);
static void nxt_router_apps_sort(nxt_task_t *task, nxt_router_t *router,
    nxt_router_temp_conf_t *tmcf);

static void nxt_router_engines_post(nxt_router_t *router,
    nxt_router_temp_conf_t *tmcf);
static void nxt_router_engine_post(nxt_event_engine_t *engine,
    nxt_work_t *jobs);

static void nxt_router_thread_start(void *data);
static void nxt_router_listen_socket_create(nxt_task_t *task, void *obj,
    void *data);
static void nxt_router_listen_socket_update(nxt_task_t *task, void *obj,
    void *data);
static void nxt_router_listen_socket_delete(nxt_task_t *task, void *obj,
    void *data);
static void nxt_router_worker_thread_quit(nxt_task_t *task, void *obj,
    void *data);
static void nxt_router_listen_socket_close(nxt_task_t *task, void *obj,
    void *data);
static void nxt_router_thread_exit_handler(nxt_task_t *task, void *obj,
    void *data);
static void nxt_router_listen_socket_release(nxt_task_t *task,
    nxt_socket_conf_t *skcf);

static void nxt_router_access_log_writer(nxt_task_t *task,
    nxt_http_request_t *r, nxt_router_access_log_t *access_log);
static u_char *nxt_router_access_log_date(u_char *buf, nxt_realtime_t *now,
    struct tm *tm, size_t size, const char *format);
static void nxt_router_access_log_open(nxt_task_t *task,
    nxt_router_temp_conf_t *tmcf);
static void nxt_router_access_log_ready(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);
static void nxt_router_access_log_error(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);
static void nxt_router_access_log_release(nxt_task_t *task,
    nxt_thread_spinlock_t *lock, nxt_router_access_log_t *access_log);
static void nxt_router_access_log_reopen_completion(nxt_task_t *task, void *obj,
    void *data);
static void nxt_router_access_log_reopen_ready(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);
static void nxt_router_access_log_reopen_error(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);

static void nxt_router_app_port_ready(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);
static void nxt_router_app_port_error(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);

static void nxt_router_app_unlink(nxt_task_t *task, nxt_app_t *app);

static void nxt_router_app_port_release(nxt_task_t *task, nxt_port_t *port,
    nxt_apr_action_t action);
static nxt_int_t nxt_router_app_port(nxt_task_t *task, nxt_app_t *app,
    nxt_request_app_link_t *req_app_link);

static void nxt_router_app_prepare_request(nxt_task_t *task,
    nxt_request_app_link_t *req_app_link);
static nxt_buf_t *nxt_router_prepare_msg(nxt_task_t *task,
    nxt_http_request_t *r, nxt_port_t *port, const nxt_str_t *prefix);

static void nxt_router_app_timeout(nxt_task_t *task, void *obj, void *data);
static void nxt_router_adjust_idle_timer(nxt_task_t *task, void *obj,
    void *data);
static void nxt_router_app_idle_timeout(nxt_task_t *task, void *obj,
    void *data);
static void nxt_router_app_joint_release_handler(nxt_task_t *task, void *obj,
    void *data);
static void nxt_router_free_app(nxt_task_t *task, void *obj, void *data);

static const nxt_http_request_state_t  nxt_http_request_send_state;
static void nxt_http_request_send_body(nxt_task_t *task, void *obj, void *data);

static void nxt_router_app_joint_use(nxt_task_t *task,
    nxt_app_joint_t *app_joint, int i);

static nxt_int_t nxt_router_http_request_done(nxt_task_t *task,
    nxt_http_request_t *r);
static void nxt_router_http_request_release(nxt_task_t *task, void *obj,
    void *data);
static void nxt_router_oosm_handler(nxt_task_t *task, nxt_port_recv_msg_t *msg);

extern const nxt_http_request_state_t  nxt_http_websocket;

static nxt_router_t  *nxt_router;

static const nxt_str_t http_prefix = nxt_string("HTTP_");
static const nxt_str_t empty_prefix = nxt_string("");

static const nxt_str_t  *nxt_app_msg_prefix[] = {
    &empty_prefix,
    &http_prefix,
    &http_prefix,
    &http_prefix,
    &http_prefix,
    &empty_prefix,
};


static const nxt_port_handlers_t  nxt_router_process_port_handlers = {
    .quit         = nxt_signal_quit_handler,
    .new_port     = nxt_router_new_port_handler,
    .change_file  = nxt_port_change_log_file_handler,
    .mmap         = nxt_port_mmap_handler,
    .data         = nxt_router_conf_data_handler,
    .remove_pid   = nxt_router_remove_pid_handler,
    .access_log   = nxt_router_access_log_reopen_handler,
    .rpc_ready    = nxt_port_rpc_handler,
    .rpc_error    = nxt_port_rpc_handler,
    .oosm         = nxt_router_oosm_handler,
};


const nxt_process_init_t  nxt_router_process = {
    .name           = "router",
    .type           = NXT_PROCESS_ROUTER,
    .prefork        = nxt_router_prefork,
    .restart        = 1,
    .setup          = nxt_process_core_setup,
    .start          = nxt_router_start,
    .port_handlers  = &nxt_router_process_port_handlers,
    .signals        = nxt_process_signals,
};


/* Queues of nxt_socket_conf_t */
nxt_queue_t  creating_sockets;
nxt_queue_t  pending_sockets;
nxt_queue_t  updating_sockets;
nxt_queue_t  keeping_sockets;
nxt_queue_t  deleting_sockets;


static nxt_int_t
nxt_router_prefork(nxt_task_t *task, nxt_process_t *process, nxt_mp_t *mp)
{
    nxt_runtime_stop_app_processes(task, task->thread->runtime);

    return NXT_OK;
}


static nxt_int_t
nxt_router_start(nxt_task_t *task, nxt_process_data_t *data)
{
    nxt_int_t      ret;
    nxt_port_t     *controller_port;
    nxt_router_t   *router;
    nxt_runtime_t  *rt;

    rt = task->thread->runtime;

    nxt_log(task, NXT_LOG_INFO, "router started");

#if (NXT_TLS)
    rt->tls = nxt_service_get(rt->services, "SSL/TLS", "OpenSSL");
    if (nxt_slow_path(rt->tls == NULL)) {
        return NXT_ERROR;
    }

    ret = rt->tls->library_init(task);
    if (nxt_slow_path(ret != NXT_OK)) {
        return ret;
    }
#endif

    ret = nxt_http_init(task);
    if (nxt_slow_path(ret != NXT_OK)) {
        return ret;
    }

    router = nxt_zalloc(sizeof(nxt_router_t));
    if (nxt_slow_path(router == NULL)) {
        return NXT_ERROR;
    }

    nxt_queue_init(&router->engines);
    nxt_queue_init(&router->sockets);
    nxt_queue_init(&router->apps);

    nxt_router = router;

    controller_port = rt->port_by_type[NXT_PROCESS_CONTROLLER];
    if (controller_port != NULL) {
        nxt_router_greet_controller(task, controller_port);
    }

    return NXT_OK;
}


static void
nxt_router_greet_controller(nxt_task_t *task, nxt_port_t *controller_port)
{
    nxt_port_socket_write(task, controller_port, NXT_PORT_MSG_PROCESS_READY,
                          -1, 0, 0, NULL);
}


static void
nxt_router_start_app_process_handler(nxt_task_t *task, nxt_port_t *port,
    void *data)
{
    size_t         size;
    uint32_t       stream;
    nxt_mp_t       *mp;
    nxt_int_t      ret;
    nxt_app_t      *app;
    nxt_buf_t      *b;
    nxt_port_t     *main_port;
    nxt_runtime_t  *rt;

    app = data;

    rt = task->thread->runtime;
    main_port = rt->port_by_type[NXT_PROCESS_MAIN];

    nxt_debug(task, "app '%V' %p start process", &app->name, app);

    size = app->name.length + 1 + app->conf.length;

    b = nxt_buf_mem_ts_alloc(task, task->thread->engine->mem_pool, size);

    if (nxt_slow_path(b == NULL)) {
        goto failed;
    }

    nxt_buf_cpystr(b, &app->name);
    *b->mem.free++ = '\0';
    nxt_buf_cpystr(b, &app->conf);

    nxt_router_app_joint_use(task, app->joint, 1);

    stream = nxt_port_rpc_register_handler(task, port,
                                           nxt_router_app_port_ready,
                                           nxt_router_app_port_error,
                                           -1, app->joint);

    if (nxt_slow_path(stream == 0)) {
        nxt_router_app_joint_use(task, app->joint, -1);

        goto failed;
    }

    ret = nxt_port_socket_write(task, main_port, NXT_PORT_MSG_START_PROCESS,
                                -1, stream, port->id, b);

    if (nxt_slow_path(ret != NXT_OK)) {
        nxt_port_rpc_cancel(task, port, stream);

        nxt_router_app_joint_use(task, app->joint, -1);

        goto failed;
    }

    nxt_router_app_use(task, app, -1);

    return;

failed:

    if (b != NULL) {
        mp = b->data;
        nxt_mp_free(mp, b);
        nxt_mp_release(mp);
    }

    nxt_thread_mutex_lock(&app->mutex);

    app->pending_processes--;

    nxt_thread_mutex_unlock(&app->mutex);

    nxt_router_app_use(task, app, -1);
}


static void
nxt_router_app_joint_use(nxt_task_t *task, nxt_app_joint_t *app_joint, int i)
{
    app_joint->use_count += i;

    if (app_joint->use_count == 0) {
        nxt_assert(app_joint->app == NULL);

        nxt_free(app_joint);
    }
}


static nxt_int_t
nxt_router_start_app_process(nxt_task_t *task, nxt_app_t *app)
{
    nxt_int_t      res;
    nxt_port_t     *router_port;
    nxt_runtime_t  *rt;

    rt = task->thread->runtime;
    router_port = rt->port_by_type[NXT_PROCESS_ROUTER];

    nxt_router_app_use(task, app, 1);

    res = nxt_port_post(task, router_port, nxt_router_start_app_process_handler,
                        app);

    if (res == NXT_OK) {
        return res;
    }

    nxt_thread_mutex_lock(&app->mutex);

    app->pending_processes--;

    nxt_thread_mutex_unlock(&app->mutex);

    nxt_router_app_use(task, app, -1);

    return NXT_ERROR;
}


nxt_inline void
nxt_request_app_link_init(nxt_task_t *task,
    nxt_request_app_link_t *req_app_link, nxt_request_rpc_data_t *req_rpc_data)
{
    nxt_buf_t           *body;
    nxt_event_engine_t  *engine;

    engine = task->thread->engine;

    nxt_memzero(req_app_link, sizeof(nxt_request_app_link_t));

    req_app_link->stream = req_rpc_data->stream;
    req_app_link->use_count = 1;
    req_app_link->req_rpc_data = req_rpc_data;
    req_rpc_data->req_app_link = req_app_link;
    req_app_link->reply_port = engine->port;
    req_app_link->request = req_rpc_data->request;
    req_app_link->apr_action = NXT_APR_GOT_RESPONSE;

    req_app_link->work.handler = NULL;
    req_app_link->work.task = &engine->task;
    req_app_link->work.obj = req_app_link;
    req_app_link->work.data = engine;

    body = req_rpc_data->request->body;

    if (body != NULL && nxt_buf_is_file(body)) {
        req_app_link->body_fd = body->file->fd;

        body->file->fd = -1;

    } else {
        req_app_link->body_fd = -1;
    }
}


nxt_inline nxt_request_app_link_t *
nxt_request_app_link_alloc(nxt_task_t *task,
    nxt_request_app_link_t *ra_src, nxt_request_rpc_data_t *req_rpc_data)
{
    nxt_mp_t                *mp;
    nxt_request_app_link_t  *req_app_link;

    if (ra_src != NULL && ra_src->mem_pool != NULL) {
        return ra_src;
    }

    mp = req_rpc_data->request->mem_pool;

    req_app_link = nxt_mp_alloc(mp, sizeof(nxt_request_app_link_t));

    if (nxt_slow_path(req_app_link == NULL)) {

        req_rpc_data->req_app_link = NULL;

        if (ra_src != NULL) {
            ra_src->req_rpc_data = NULL;
        }

        return NULL;
    }

    nxt_mp_retain(mp);

    nxt_request_app_link_init(task, req_app_link, req_rpc_data);

    if (ra_src != NULL) {
        req_app_link->body_fd = ra_src->body_fd;
    }

    req_app_link->mem_pool = mp;

    return req_app_link;
}


nxt_inline nxt_bool_t
nxt_router_msg_cancel(nxt_task_t *task, nxt_msg_info_t *msg_info,
    uint32_t stream)
{
    nxt_buf_t   *b, *next;
    nxt_bool_t  cancelled;

    if (msg_info->buf == NULL) {
        return 0;
    }

    cancelled = nxt_port_mmap_tracking_cancel(task, &msg_info->tracking,
                                              stream);

    if (cancelled) {
        nxt_debug(task, "stream #%uD: cancelled by router", stream);
    }

    for (b = msg_info->buf; b != NULL; b = next) {
        next = b->next;
        b->next = NULL;

        b->completion_handler = msg_info->completion_handler;

        if (b->is_port_mmap_sent) {
            b->is_port_mmap_sent = cancelled == 0;
            b->completion_handler(task, b, b->parent);
        }
    }

    msg_info->buf = NULL;

    return cancelled;
}


static void
nxt_request_app_link_update_peer_handler(nxt_task_t *task, void *obj,
    void *data)
{
    nxt_request_app_link_t  *req_app_link;

    req_app_link = obj;

    nxt_request_app_link_update_peer(task, req_app_link);

    nxt_request_app_link_use(task, req_app_link, -1);
}


static void
nxt_request_app_link_update_peer(nxt_task_t *task,
    nxt_request_app_link_t *req_app_link)
{
    nxt_event_engine_t      *engine;
    nxt_request_rpc_data_t  *req_rpc_data;

    engine = req_app_link->work.data;

    if (task->thread->engine != engine) {
        nxt_request_app_link_inc_use(req_app_link);

        req_app_link->work.handler = nxt_request_app_link_update_peer_handler;
        req_app_link->work.task = &engine->task;
        req_app_link->work.next = NULL;

        nxt_debug(task, "req_app_link stream #%uD post update peer to %p",
                  req_app_link->stream, engine);

        nxt_event_engine_post(engine, &req_app_link->work);

        return;
    }

    nxt_debug(task, "req_app_link stream #%uD update peer",
              req_app_link->stream);

    req_rpc_data = req_app_link->req_rpc_data;

    if (req_rpc_data != NULL && req_app_link->app_port != NULL) {
        nxt_port_rpc_ex_set_peer(task, engine->port, req_rpc_data,
                                 req_app_link->app_port->pid);
    }
}


static void
nxt_request_app_link_release(nxt_task_t *task,
    nxt_request_app_link_t *req_app_link)
{
    nxt_mp_t                *mp;
    nxt_http_request_t      *r;
    nxt_request_rpc_data_t  *req_rpc_data;

    nxt_assert(task->thread->engine == req_app_link->work.data);
    nxt_assert(req_app_link->use_count == 0);

    nxt_debug(task, "req_app_link stream #%uD release", req_app_link->stream);

    req_rpc_data = req_app_link->req_rpc_data;

    if (req_rpc_data != NULL) {
        if (nxt_slow_path(req_app_link->err_code != 0)) {
            nxt_http_request_error(task, req_rpc_data->request,
                                   req_app_link->err_code);

        } else {
            req_rpc_data->app_port = req_app_link->app_port;
            req_rpc_data->apr_action = req_app_link->apr_action;
            req_rpc_data->msg_info = req_app_link->msg_info;

            if (req_rpc_data->app->timeout != 0) {
                r = req_rpc_data->request;

                r->timer.handler = nxt_router_app_timeout;
                r->timer_data = req_rpc_data;
                nxt_timer_add(task->thread->engine, &r->timer,
                              req_rpc_data->app->timeout);
            }

            req_app_link->app_port = NULL;
            req_app_link->msg_info.buf = NULL;
        }

        req_rpc_data->req_app_link = NULL;
        req_app_link->req_rpc_data = NULL;
    }

    if (req_app_link->app_port != NULL) {
        nxt_router_app_port_release(task, req_app_link->app_port,
                                    req_app_link->apr_action);

        req_app_link->app_port = NULL;
    }

    if (req_app_link->body_fd != -1) {
        nxt_fd_close(req_app_link->body_fd);

        req_app_link->body_fd = -1;
    }

    nxt_router_msg_cancel(task, &req_app_link->msg_info, req_app_link->stream);

    mp = req_app_link->mem_pool;

    if (mp != NULL) {
        nxt_mp_free(mp, req_app_link);
        nxt_mp_release(mp);
    }
}


static void
nxt_request_app_link_release_handler(nxt_task_t *task, void *obj, void *data)
{
    nxt_request_app_link_t  *req_app_link;

    req_app_link = obj;

    nxt_assert(req_app_link->work.data == data);

    nxt_request_app_link_use(task, req_app_link, -1);
}


static void
nxt_request_app_link_use(nxt_task_t *task, nxt_request_app_link_t *req_app_link,
    int i)
{
    int                 c;
    nxt_event_engine_t  *engine;

    c = nxt_atomic_fetch_add(&req_app_link->use_count, i);

    if (i < 0 && c == -i) {
        engine = req_app_link->work.data;

        if (task->thread->engine == engine) {
            nxt_request_app_link_release(task, req_app_link);

            return;
        }

        nxt_request_app_link_inc_use(req_app_link);

        req_app_link->work.handler = nxt_request_app_link_release_handler;
        req_app_link->work.task = &engine->task;
        req_app_link->work.next = NULL;

        nxt_debug(task, "req_app_link stream #%uD post release to %p",
                  req_app_link->stream, engine);

        nxt_event_engine_post(engine, &req_app_link->work);
    }
}


nxt_inline void
nxt_request_app_link_error(nxt_task_t *task, nxt_app_t *app,
    nxt_request_app_link_t *req_app_link, const char *str)
{
    req_app_link->app_port = NULL;
    req_app_link->err_code = 500;
    req_app_link->err_str = str;

    nxt_alert(task, "app \"%V\" internal error: %s on #%uD",
              &app->name, str, req_app_link->stream);
}


nxt_inline void
nxt_request_app_link_pending(nxt_task_t *task, nxt_app_t *app,
    nxt_request_app_link_t *req_app_link)
{
    nxt_queue_insert_tail(&req_app_link->app_port->pending_requests,
                          &req_app_link->link_port_pending);
    nxt_queue_insert_tail(&app->pending, &req_app_link->link_app_pending);

    nxt_request_app_link_inc_use(req_app_link);

    req_app_link->res_time = nxt_thread_monotonic_time(task->thread)
                             + app->res_timeout;

    nxt_debug(task, "req_app_link stream #%uD enqueue to pending_requests",
              req_app_link->stream);
}


nxt_inline nxt_bool_t
nxt_queue_chk_remove(nxt_queue_link_t *lnk)
{
    if (lnk->next != NULL) {
        nxt_queue_remove(lnk);

        lnk->next = NULL;

        return 1;
    }

    return 0;
}


nxt_inline void
nxt_request_rpc_data_unlink(nxt_task_t *task,
    nxt_request_rpc_data_t *req_rpc_data)
{
    int                     ra_use_delta;
    nxt_request_app_link_t  *req_app_link;

    if (req_rpc_data->app_port != NULL) {
        nxt_router_app_port_release(task, req_rpc_data->app_port,
                                    req_rpc_data->apr_action);

        req_rpc_data->app_port = NULL;
    }

    nxt_router_msg_cancel(task, &req_rpc_data->msg_info, req_rpc_data->stream);

    req_app_link = req_rpc_data->req_app_link;
    if (req_app_link != NULL) {
        req_rpc_data->req_app_link = NULL;
        req_app_link->req_rpc_data = NULL;

        ra_use_delta = 0;

        nxt_thread_mutex_lock(&req_rpc_data->app->mutex);

        if (req_app_link->link_app_requests.next == NULL
            && req_app_link->link_port_pending.next == NULL
            && req_app_link->link_app_pending.next == NULL
            && req_app_link->link_port_websockets.next == NULL)
        {
            req_app_link = NULL;

        } else {
            ra_use_delta -=
                nxt_queue_chk_remove(&req_app_link->link_app_requests)
                + nxt_queue_chk_remove(&req_app_link->link_port_pending)
                + nxt_queue_chk_remove(&req_app_link->link_port_websockets);

            nxt_queue_chk_remove(&req_app_link->link_app_pending);
        }

        nxt_thread_mutex_unlock(&req_rpc_data->app->mutex);

        if (req_app_link != NULL) {
            nxt_request_app_link_use(task, req_app_link, ra_use_delta);
        }
    }

    if (req_rpc_data->app != NULL) {
        nxt_router_app_use(task, req_rpc_data->app, -1);

        req_rpc_data->app = NULL;
    }

    if (req_rpc_data->request != NULL) {
        req_rpc_data->request->timer_data = NULL;

        nxt_router_http_request_done(task, req_rpc_data->request);

        req_rpc_data->request->req_rpc_data = NULL;
        req_rpc_data->request = NULL;
    }
}


void
nxt_router_new_port_handler(nxt_task_t *task, nxt_port_recv_msg_t *msg)
{
    nxt_port_new_port_handler(task, msg);

    if (msg->u.new_port != NULL
        && msg->u.new_port->type == NXT_PROCESS_CONTROLLER)
    {
        nxt_router_greet_controller(task, msg->u.new_port);
    }

    if (msg->port_msg.stream == 0) {
        return;
    }

    if (msg->u.new_port == NULL
        || msg->u.new_port->type != NXT_PROCESS_APP)
    {
        msg->port_msg.type = _NXT_PORT_MSG_RPC_ERROR;
    }

    nxt_port_rpc_handler(task, msg);
}


void
nxt_router_conf_data_handler(nxt_task_t *task, nxt_port_recv_msg_t *msg)
{
    void                    *p;
    size_t                  size;
    nxt_int_t               ret;
    nxt_router_temp_conf_t  *tmcf;

    tmcf = nxt_router_temp_conf(task);
    if (nxt_slow_path(tmcf == NULL)) {
        return;
    }

    if (nxt_slow_path(msg->fd == -1)) {
        nxt_alert(task, "conf_data_handler: invalid file shm fd");
        return;
    }

    if (nxt_buf_mem_used_size(&msg->buf->mem) != sizeof(size_t)) {
        nxt_alert(task, "conf_data_handler: unexpected buffer size (%d)",
                  (int) nxt_buf_mem_used_size(&msg->buf->mem));

        nxt_fd_close(msg->fd);
        msg->fd = -1;

        return;
    }

    nxt_memcpy(&size, msg->buf->mem.pos, sizeof(size_t));

    p = nxt_mem_mmap(NULL, size, PROT_READ, MAP_SHARED, msg->fd, 0);

    nxt_fd_close(msg->fd);
    msg->fd = -1;

    if (nxt_slow_path(p == MAP_FAILED)) {
        return;
    }

    nxt_debug(task, "conf_data_handler(%uz): %*s", size, size, p);

    tmcf->router_conf->router = nxt_router;
    tmcf->stream = msg->port_msg.stream;
    tmcf->port = nxt_runtime_port_find(task->thread->runtime,
                                       msg->port_msg.pid,
                                       msg->port_msg.reply_port);

    if (nxt_slow_path(tmcf->port == NULL)) {
        nxt_alert(task, "reply port not found");

        goto fail;
    }

    nxt_port_use(task, tmcf->port, 1);

    ret = nxt_router_conf_create(task, tmcf, p, nxt_pointer_to(p, size));

    if (nxt_fast_path(ret == NXT_OK)) {
        nxt_router_conf_apply(task, tmcf, NULL);

    } else {
        nxt_router_conf_error(task, tmcf);
    }

fail:

    nxt_mem_munmap(p, size);
}


static void
nxt_router_app_process_remove_pid(nxt_task_t *task, nxt_port_t *port,
    void *data)
{
    union {
        nxt_pid_t  removed_pid;
        void       *data;
    } u;

    u.data = data;

    nxt_port_rpc_remove_peer(task, port, u.removed_pid);
}


void
nxt_router_remove_pid_handler(nxt_task_t *task, nxt_port_recv_msg_t *msg)
{
    nxt_event_engine_t  *engine;

    nxt_port_remove_pid_handler(task, msg);

    nxt_queue_each(engine, &nxt_router->engines, nxt_event_engine_t, link0)
    {
        if (nxt_fast_path(engine->port != NULL)) {
            nxt_port_post(task, engine->port, nxt_router_app_process_remove_pid,
                          msg->u.data);
        }
    }
    nxt_queue_loop;

    if (msg->port_msg.stream == 0) {
        return;
    }

    msg->port_msg.type = _NXT_PORT_MSG_RPC_ERROR;

    nxt_port_rpc_handler(task, msg);
}


static nxt_router_temp_conf_t *
nxt_router_temp_conf(nxt_task_t *task)
{
    nxt_mp_t                *mp, *tmp;
    nxt_router_conf_t       *rtcf;
    nxt_router_temp_conf_t  *tmcf;

    mp = nxt_mp_create(1024, 128, 256, 32);
    if (nxt_slow_path(mp == NULL)) {
        return NULL;
    }

    rtcf = nxt_mp_zget(mp, sizeof(nxt_router_conf_t));
    if (nxt_slow_path(rtcf == NULL)) {
        goto fail;
    }

    rtcf->mem_pool = mp;

    tmp = nxt_mp_create(1024, 128, 256, 32);
    if (nxt_slow_path(tmp == NULL)) {
        goto fail;
    }

    tmcf = nxt_mp_zget(tmp, sizeof(nxt_router_temp_conf_t));
    if (nxt_slow_path(tmcf == NULL)) {
        goto temp_fail;
    }

    tmcf->mem_pool = tmp;
    tmcf->router_conf = rtcf;
    tmcf->count = 1;
    tmcf->engine = task->thread->engine;

    tmcf->engines = nxt_array_create(tmcf->mem_pool, 4,
                                     sizeof(nxt_router_engine_conf_t));
    if (nxt_slow_path(tmcf->engines == NULL)) {
        goto temp_fail;
    }

    nxt_queue_init(&creating_sockets);
    nxt_queue_init(&pending_sockets);
    nxt_queue_init(&updating_sockets);
    nxt_queue_init(&keeping_sockets);
    nxt_queue_init(&deleting_sockets);

#if (NXT_TLS)
    nxt_queue_init(&tmcf->tls);
#endif

    nxt_queue_init(&tmcf->apps);
    nxt_queue_init(&tmcf->previous);

    return tmcf;

temp_fail:

    nxt_mp_destroy(tmp);

fail:

    nxt_mp_destroy(mp);

    return NULL;
}


nxt_inline nxt_bool_t
nxt_router_app_can_start(nxt_app_t *app)
{
    return app->processes + app->pending_processes < app->max_processes
            && app->pending_processes < app->max_pending_processes;
}


nxt_inline nxt_bool_t
nxt_router_app_need_start(nxt_app_t *app)
{
    return app->idle_processes + app->pending_processes
            < app->spare_processes;
}


static void
nxt_router_conf_apply(nxt_task_t *task, void *obj, void *data)
{
    nxt_int_t                    ret;
    nxt_app_t                    *app;
    nxt_router_t                 *router;
    nxt_runtime_t                *rt;
    nxt_queue_link_t             *qlk;
    nxt_socket_conf_t            *skcf;
    nxt_router_conf_t            *rtcf;
    nxt_router_temp_conf_t       *tmcf;
    const nxt_event_interface_t  *interface;
#if (NXT_TLS)
    nxt_router_tlssock_t         *tls;
#endif

    tmcf = obj;

    qlk = nxt_queue_first(&pending_sockets);

    if (qlk != nxt_queue_tail(&pending_sockets)) {
        nxt_queue_remove(qlk);
        nxt_queue_insert_tail(&creating_sockets, qlk);

        skcf = nxt_queue_link_data(qlk, nxt_socket_conf_t, link);

        nxt_router_listen_socket_rpc_create(task, tmcf, skcf);

        return;
    }

#if (NXT_TLS)
    qlk = nxt_queue_first(&tmcf->tls);

    if (qlk != nxt_queue_tail(&tmcf->tls)) {
        nxt_queue_remove(qlk);

        tls = nxt_queue_link_data(qlk, nxt_router_tlssock_t, link);

        nxt_router_tls_rpc_create(task, tmcf, tls);
        return;
    }
#endif

    nxt_queue_each(app, &tmcf->apps, nxt_app_t, link) {

        if (nxt_router_app_need_start(app)) {
            nxt_router_app_rpc_create(task, tmcf, app);
            return;
        }

    } nxt_queue_loop;

    rtcf = tmcf->router_conf;

    if (rtcf->access_log != NULL && rtcf->access_log->fd == -1) {
        nxt_router_access_log_open(task, tmcf);
        return;
    }

    rt = task->thread->runtime;

    interface = nxt_service_get(rt->services, "engine", NULL);

    router = rtcf->router;

    ret = nxt_router_engines_create(task, router, tmcf, interface);
    if (nxt_slow_path(ret != NXT_OK)) {
        goto fail;
    }

    ret = nxt_router_threads_create(task, rt, tmcf);
    if (nxt_slow_path(ret != NXT_OK)) {
        goto fail;
    }

    nxt_router_apps_sort(task, router, tmcf);

    nxt_router_engines_post(router, tmcf);

    nxt_queue_add(&router->sockets, &updating_sockets);
    nxt_queue_add(&router->sockets, &creating_sockets);

    router->access_log = rtcf->access_log;

    nxt_router_conf_ready(task, tmcf);

    return;

fail:

    nxt_router_conf_error(task, tmcf);

    return;
}


static void
nxt_router_conf_wait(nxt_task_t *task, void *obj, void *data)
{
    nxt_joint_job_t  *job;

    job = obj;

    nxt_router_conf_ready(task, job->tmcf);
}


static void
nxt_router_conf_ready(nxt_task_t *task, nxt_router_temp_conf_t *tmcf)
{
    nxt_debug(task, "temp conf count:%D", tmcf->count);

    if (--tmcf->count == 0) {
        nxt_router_conf_send(task, tmcf, NXT_PORT_MSG_RPC_READY_LAST);

        nxt_mp_destroy(tmcf->mem_pool);
    }
}


static void
nxt_router_conf_error(nxt_task_t *task, nxt_router_temp_conf_t *tmcf)
{
    nxt_app_t          *app;
    nxt_queue_t        new_socket_confs;
    nxt_socket_t       s;
    nxt_router_t       *router;
    nxt_queue_link_t   *qlk;
    nxt_socket_conf_t  *skcf;
    nxt_router_conf_t  *rtcf;

    nxt_alert(task, "failed to apply new conf");

    for (qlk = nxt_queue_first(&creating_sockets);
         qlk != nxt_queue_tail(&creating_sockets);
         qlk = nxt_queue_next(qlk))
    {
        skcf = nxt_queue_link_data(qlk, nxt_socket_conf_t, link);
        s = skcf->listen->socket;

        if (s != -1) {
            nxt_socket_close(task, s);
        }

        nxt_free(skcf->listen);
    }

    nxt_queue_init(&new_socket_confs);
    nxt_queue_add(&new_socket_confs, &updating_sockets);
    nxt_queue_add(&new_socket_confs, &pending_sockets);
    nxt_queue_add(&new_socket_confs, &creating_sockets);

    rtcf = tmcf->router_conf;

    nxt_http_routes_cleanup(task, rtcf->routes);

    nxt_queue_each(skcf, &new_socket_confs, nxt_socket_conf_t, link) {

        if (skcf->action != NULL) {
            nxt_http_action_cleanup(task, skcf->action);
        }

    } nxt_queue_loop;

    nxt_queue_each(app, &tmcf->apps, nxt_app_t, link) {

        nxt_router_app_unlink(task, app);

    } nxt_queue_loop;

    router = rtcf->router;

    nxt_queue_add(&router->sockets, &keeping_sockets);
    nxt_queue_add(&router->sockets, &deleting_sockets);

    nxt_queue_add(&router->apps, &tmcf->previous);

    // TODO: new engines and threads

    nxt_router_access_log_release(task, &router->lock, rtcf->access_log);

    nxt_mp_destroy(rtcf->mem_pool);

    nxt_router_conf_send(task, tmcf, NXT_PORT_MSG_RPC_ERROR);

    nxt_mp_destroy(tmcf->mem_pool);
}


static void
nxt_router_conf_send(nxt_task_t *task, nxt_router_temp_conf_t *tmcf,
    nxt_port_msg_type_t type)
{
    nxt_port_socket_write(task, tmcf->port, type, -1, tmcf->stream, 0, NULL);

    nxt_port_use(task, tmcf->port, -1);

    tmcf->port = NULL;
}


static nxt_conf_map_t  nxt_router_conf[] = {
    {
        nxt_string("listeners_threads"),
        NXT_CONF_MAP_INT32,
        offsetof(nxt_router_conf_t, threads),
    },
};


static nxt_conf_map_t  nxt_router_app_conf[] = {
    {
        nxt_string("type"),
        NXT_CONF_MAP_STR,
        offsetof(nxt_router_app_conf_t, type),
    },

    {
        nxt_string("limits"),
        NXT_CONF_MAP_PTR,
        offsetof(nxt_router_app_conf_t, limits_value),
    },

    {
        nxt_string("processes"),
        NXT_CONF_MAP_INT32,
        offsetof(nxt_router_app_conf_t, processes),
    },

    {
        nxt_string("processes"),
        NXT_CONF_MAP_PTR,
        offsetof(nxt_router_app_conf_t, processes_value),
    },

    {
        nxt_string("targets"),
        NXT_CONF_MAP_PTR,
        offsetof(nxt_router_app_conf_t, targets_value),
    },
};


static nxt_conf_map_t  nxt_router_app_limits_conf[] = {
    {
        nxt_string("timeout"),
        NXT_CONF_MAP_MSEC,
        offsetof(nxt_router_app_conf_t, timeout),
    },

    {
        nxt_string("reschedule_timeout"),
        NXT_CONF_MAP_MSEC,
        offsetof(nxt_router_app_conf_t, res_timeout),
    },

    {
        nxt_string("requests"),
        NXT_CONF_MAP_INT32,
        offsetof(nxt_router_app_conf_t, requests),
    },
};


static nxt_conf_map_t  nxt_router_app_processes_conf[] = {
    {
        nxt_string("spare"),
        NXT_CONF_MAP_INT32,
        offsetof(nxt_router_app_conf_t, spare_processes),
    },

    {
        nxt_string("max"),
        NXT_CONF_MAP_INT32,
        offsetof(nxt_router_app_conf_t, max_processes),
    },

    {
        nxt_string("idle_timeout"),
        NXT_CONF_MAP_MSEC,
        offsetof(nxt_router_app_conf_t, idle_timeout),
    },
};


static nxt_conf_map_t  nxt_router_listener_conf[] = {
    {
        nxt_string("pass"),
        NXT_CONF_MAP_STR_COPY,
        offsetof(nxt_router_listener_conf_t, pass),
    },

    {
        nxt_string("application"),
        NXT_CONF_MAP_STR_COPY,
        offsetof(nxt_router_listener_conf_t, application),
    },
};


static nxt_conf_map_t  nxt_router_http_conf[] = {
    {
        nxt_string("header_buffer_size"),
        NXT_CONF_MAP_SIZE,
        offsetof(nxt_socket_conf_t, header_buffer_size),
    },

    {
        nxt_string("large_header_buffer_size"),
        NXT_CONF_MAP_SIZE,
        offsetof(nxt_socket_conf_t, large_header_buffer_size),
    },

    {
        nxt_string("large_header_buffers"),
        NXT_CONF_MAP_SIZE,
        offsetof(nxt_socket_conf_t, large_header_buffers),
    },

    {
        nxt_string("body_buffer_size"),
        NXT_CONF_MAP_SIZE,
        offsetof(nxt_socket_conf_t, body_buffer_size),
    },

    {
        nxt_string("max_body_size"),
        NXT_CONF_MAP_SIZE,
        offsetof(nxt_socket_conf_t, max_body_size),
    },

    {
        nxt_string("idle_timeout"),
        NXT_CONF_MAP_MSEC,
        offsetof(nxt_socket_conf_t, idle_timeout),
    },

    {
        nxt_string("header_read_timeout"),
        NXT_CONF_MAP_MSEC,
        offsetof(nxt_socket_conf_t, header_read_timeout),
    },

    {
        nxt_string("body_read_timeout"),
        NXT_CONF_MAP_MSEC,
        offsetof(nxt_socket_conf_t, body_read_timeout),
    },

    {
        nxt_string("send_timeout"),
        NXT_CONF_MAP_MSEC,
        offsetof(nxt_socket_conf_t, send_timeout),
    },

    {
        nxt_string("body_temp_path"),
        NXT_CONF_MAP_STR,
        offsetof(nxt_socket_conf_t, body_temp_path),
    },
};


static nxt_conf_map_t  nxt_router_websocket_conf[] = {
    {
        nxt_string("max_frame_size"),
        NXT_CONF_MAP_SIZE,
        offsetof(nxt_websocket_conf_t, max_frame_size),
    },

    {
        nxt_string("read_timeout"),
        NXT_CONF_MAP_MSEC,
        offsetof(nxt_websocket_conf_t, read_timeout),
    },

    {
        nxt_string("keepalive_interval"),
        NXT_CONF_MAP_MSEC,
        offsetof(nxt_websocket_conf_t, keepalive_interval),
    },

};


static nxt_int_t
nxt_router_conf_create(nxt_task_t *task, nxt_router_temp_conf_t *tmcf,
    u_char *start, u_char *end)
{
    u_char                      *p;
    size_t                      size;
    nxt_mp_t                    *mp, *app_mp;
    uint32_t                    next, next_target;
    nxt_int_t                   ret;
    nxt_str_t                   name, path, target;
    nxt_app_t                   *app, *prev;
    nxt_str_t                   *t, *s, *targets;
    nxt_uint_t                  n, i;
    nxt_router_t                *router;
    nxt_app_joint_t             *app_joint;
    nxt_conf_value_t            *conf, *http, *value, *websocket;
    nxt_conf_value_t            *applications, *application;
    nxt_conf_value_t            *listeners, *listener;
    nxt_conf_value_t            *routes_conf, *static_conf;
    nxt_socket_conf_t           *skcf;
    nxt_http_routes_t           *routes;
    nxt_event_engine_t          *engine;
    nxt_app_lang_module_t       *lang;
    nxt_router_app_conf_t       apcf;
    nxt_router_access_log_t     *access_log;
    nxt_router_listener_conf_t  lscf;
#if (NXT_TLS)
    nxt_router_tlssock_t        *tls;
#endif

    static nxt_str_t  http_path = nxt_string("/settings/http");
    static nxt_str_t  applications_path = nxt_string("/applications");
    static nxt_str_t  listeners_path = nxt_string("/listeners");
    static nxt_str_t  routes_path = nxt_string("/routes");
    static nxt_str_t  access_log_path = nxt_string("/access_log");
#if (NXT_TLS)
    static nxt_str_t  certificate_path = nxt_string("/tls/certificate");
#endif
    static nxt_str_t  static_path = nxt_string("/settings/http/static");
    static nxt_str_t  websocket_path = nxt_string("/settings/http/websocket");

    conf = nxt_conf_json_parse(tmcf->mem_pool, start, end, NULL);
    if (conf == NULL) {
        nxt_alert(task, "configuration parsing error");
        return NXT_ERROR;
    }

    mp = tmcf->router_conf->mem_pool;

    ret = nxt_conf_map_object(mp, conf, nxt_router_conf,
                              nxt_nitems(nxt_router_conf), tmcf->router_conf);
    if (ret != NXT_OK) {
        nxt_alert(task, "root map error");
        return NXT_ERROR;
    }

    if (tmcf->router_conf->threads == 0) {
        tmcf->router_conf->threads = nxt_ncpu;
    }

    static_conf = nxt_conf_get_path(conf, &static_path);

    ret = nxt_router_conf_process_static(task, tmcf->router_conf, static_conf);
    if (nxt_slow_path(ret != NXT_OK)) {
        return NXT_ERROR;
    }

    router = tmcf->router_conf->router;

    applications = nxt_conf_get_path(conf, &applications_path);

    if (applications != NULL) {
        next = 0;

        for ( ;; ) {
            application = nxt_conf_next_object_member(applications,
                                                      &name, &next);
            if (application == NULL) {
                break;
            }

            nxt_debug(task, "application \"%V\"", &name);

            size = nxt_conf_json_length(application, NULL);

            app_mp = nxt_mp_create(4096, 128, 1024, 64);
            if (nxt_slow_path(app_mp == NULL)) {
                goto fail;
            }

            app = nxt_mp_get(app_mp, sizeof(nxt_app_t) + name.length + size);
            if (app == NULL) {
                goto app_fail;
            }

            nxt_memzero(app, sizeof(nxt_app_t));

            app->mem_pool = app_mp;

            app->name.start = nxt_pointer_to(app, sizeof(nxt_app_t));
            app->conf.start = nxt_pointer_to(app, sizeof(nxt_app_t)
                                                  + name.length);

            p = nxt_conf_json_print(app->conf.start, application, NULL);
            app->conf.length = p - app->conf.start;

            nxt_assert(app->conf.length <= size);

            nxt_debug(task, "application conf \"%V\"", &app->conf);

            prev = nxt_router_app_find(&router->apps, &name);

            if (prev != NULL && nxt_strstr_eq(&app->conf, &prev->conf)) {
                nxt_mp_destroy(app_mp);

                nxt_queue_remove(&prev->link);
                nxt_queue_insert_tail(&tmcf->previous, &prev->link);
                continue;
            }

            apcf.processes = 1;
            apcf.max_processes = 1;
            apcf.spare_processes = 0;
            apcf.timeout = 0;
            apcf.res_timeout = 1000;
            apcf.idle_timeout = 15000;
            apcf.requests = 0;
            apcf.limits_value = NULL;
            apcf.processes_value = NULL;
            apcf.targets_value = NULL;

            app_joint = nxt_malloc(sizeof(nxt_app_joint_t));
            if (nxt_slow_path(app_joint == NULL)) {
                goto app_fail;
            }

            nxt_memzero(app_joint, sizeof(nxt_app_joint_t));

            ret = nxt_conf_map_object(mp, application, nxt_router_app_conf,
                                      nxt_nitems(nxt_router_app_conf), &apcf);
            if (ret != NXT_OK) {
                nxt_alert(task, "application map error");
                goto app_fail;
            }

            if (apcf.limits_value != NULL) {

                if (nxt_conf_type(apcf.limits_value) != NXT_CONF_OBJECT) {
                    nxt_alert(task, "application limits is not object");
                    goto app_fail;
                }

                ret = nxt_conf_map_object(mp, apcf.limits_value,
                                        nxt_router_app_limits_conf,
                                        nxt_nitems(nxt_router_app_limits_conf),
                                        &apcf);
                if (ret != NXT_OK) {
                    nxt_alert(task, "application limits map error");
                    goto app_fail;
                }
            }

            if (apcf.processes_value != NULL
                && nxt_conf_type(apcf.processes_value) == NXT_CONF_OBJECT)
            {
                ret = nxt_conf_map_object(mp, apcf.processes_value,
                                     nxt_router_app_processes_conf,
                                     nxt_nitems(nxt_router_app_processes_conf),
                                     &apcf);
                if (ret != NXT_OK) {
                    nxt_alert(task, "application processes map error");
                    goto app_fail;
                }

            } else {
                apcf.max_processes = apcf.processes;
                apcf.spare_processes = apcf.processes;
            }

            if (apcf.targets_value != NULL) {
                n = nxt_conf_object_members_count(apcf.targets_value);

                targets = nxt_mp_get(app_mp, sizeof(nxt_str_t) * n);
                if (nxt_slow_path(targets == NULL)) {
                    goto app_fail;
                }

                next_target = 0;

                for (i = 0; i < n; i++) {
                    (void) nxt_conf_next_object_member(apcf.targets_value,
                                                       &target, &next_target);

                    s = nxt_str_dup(app_mp, &targets[i], &target);
                    if (nxt_slow_path(s == NULL)) {
                        goto app_fail;
                    }
                }

            } else {
                targets = NULL;
            }

            nxt_debug(task, "application type: %V", &apcf.type);
            nxt_debug(task, "application processes: %D", apcf.processes);
            nxt_debug(task, "application request timeout: %M", apcf.timeout);
            nxt_debug(task, "application reschedule timeout: %M",
                      apcf.res_timeout);
            nxt_debug(task, "application requests: %D", apcf.requests);

            lang = nxt_app_lang_module(task->thread->runtime, &apcf.type);

            if (lang == NULL) {
                nxt_alert(task, "unknown application type: \"%V\"", &apcf.type);
                goto app_fail;
            }

            nxt_debug(task, "application language module: \"%s\"", lang->file);

            ret = nxt_thread_mutex_create(&app->mutex);
            if (ret != NXT_OK) {
                goto app_fail;
            }

            nxt_queue_init(&app->ports);
            nxt_queue_init(&app->spare_ports);
            nxt_queue_init(&app->idle_ports);
            nxt_queue_init(&app->requests);
            nxt_queue_init(&app->pending);

            app->name.length = name.length;
            nxt_memcpy(app->name.start, name.start, name.length);

            app->type = lang->type;
            app->max_processes = apcf.max_processes;
            app->spare_processes = apcf.spare_processes;
            app->max_pending_processes = apcf.spare_processes
                                         ? apcf.spare_processes : 1;
            app->timeout = apcf.timeout;
            app->res_timeout = apcf.res_timeout * 1000000;
            app->idle_timeout = apcf.idle_timeout;
            app->max_pending_responses = 2;
            app->max_requests = apcf.requests;

            app->targets = targets;

            engine = task->thread->engine;

            app->engine = engine;

            app->adjust_idle_work.handler = nxt_router_adjust_idle_timer;
            app->adjust_idle_work.task = &engine->task;
            app->adjust_idle_work.obj = app;

            nxt_queue_insert_tail(&tmcf->apps, &app->link);

            nxt_router_app_use(task, app, 1);

            app->joint = app_joint;

            app_joint->use_count = 1;
            app_joint->app = app;

            app_joint->idle_timer.bias = NXT_TIMER_DEFAULT_BIAS;
            app_joint->idle_timer.work_queue = &engine->fast_work_queue;
            app_joint->idle_timer.handler = nxt_router_app_idle_timeout;
            app_joint->idle_timer.task = &engine->task;
            app_joint->idle_timer.log = app_joint->idle_timer.task->log;

            app_joint->free_app_work.handler = nxt_router_free_app;
            app_joint->free_app_work.task = &engine->task;
            app_joint->free_app_work.obj = app_joint;
        }
    }

    routes_conf = nxt_conf_get_path(conf, &routes_path);
    if (nxt_fast_path(routes_conf != NULL)) {
        routes = nxt_http_routes_create(task, tmcf, routes_conf);
        if (nxt_slow_path(routes == NULL)) {
            return NXT_ERROR;
        }
        tmcf->router_conf->routes = routes;
    }

    ret = nxt_upstreams_create(task, tmcf, conf);
    if (nxt_slow_path(ret != NXT_OK)) {
        return ret;
    }

    http = nxt_conf_get_path(conf, &http_path);
#if 0
    if (http == NULL) {
        nxt_alert(task, "no \"http\" block");
        return NXT_ERROR;
    }
#endif

    websocket = nxt_conf_get_path(conf, &websocket_path);

    listeners = nxt_conf_get_path(conf, &listeners_path);

    if (listeners != NULL) {
        next = 0;

        for ( ;; ) {
            listener = nxt_conf_next_object_member(listeners, &name, &next);
            if (listener == NULL) {
                break;
            }

            skcf = nxt_router_socket_conf(task, tmcf, &name);
            if (skcf == NULL) {
                goto fail;
            }

            nxt_memzero(&lscf, sizeof(lscf));

            ret = nxt_conf_map_object(mp, listener, nxt_router_listener_conf,
                                      nxt_nitems(nxt_router_listener_conf),
                                      &lscf);
            if (ret != NXT_OK) {
                nxt_alert(task, "listener map error");
                goto fail;
            }

            nxt_debug(task, "application: %V", &lscf.application);

            // STUB, default values if http block is not defined.
            skcf->header_buffer_size = 2048;
            skcf->large_header_buffer_size = 8192;
            skcf->large_header_buffers = 4;
            skcf->body_buffer_size = 16 * 1024;
            skcf->max_body_size = 8 * 1024 * 1024;
            skcf->proxy_header_buffer_size = 64 * 1024;
            skcf->proxy_buffer_size = 4096;
            skcf->proxy_buffers = 256;
            skcf->idle_timeout = 180 * 1000;
            skcf->header_read_timeout = 30 * 1000;
            skcf->body_read_timeout = 30 * 1000;
            skcf->send_timeout = 30 * 1000;
            skcf->proxy_timeout = 60 * 1000;
            skcf->proxy_send_timeout = 30 * 1000;
            skcf->proxy_read_timeout = 30 * 1000;

            skcf->websocket_conf.max_frame_size = 1024 * 1024;
            skcf->websocket_conf.read_timeout = 60 * 1000;
            skcf->websocket_conf.keepalive_interval = 30 * 1000;

            nxt_str_null(&skcf->body_temp_path);

            if (http != NULL) {
                ret = nxt_conf_map_object(mp, http, nxt_router_http_conf,
                                          nxt_nitems(nxt_router_http_conf),
                                          skcf);
                if (ret != NXT_OK) {
                    nxt_alert(task, "http map error");
                    goto fail;
                }
            }

            if (websocket != NULL) {
                ret = nxt_conf_map_object(mp, websocket,
                                          nxt_router_websocket_conf,
                                          nxt_nitems(nxt_router_websocket_conf),
                                          &skcf->websocket_conf);
                if (ret != NXT_OK) {
                    nxt_alert(task, "websocket map error");
                    goto fail;
                }
            }

            t = &skcf->body_temp_path;

            if (t->length == 0) {
                t->start = (u_char *) task->thread->runtime->tmp;
                t->length = nxt_strlen(t->start);
            }

#if (NXT_TLS)
            value = nxt_conf_get_path(listener, &certificate_path);

            if (value != NULL) {
                nxt_conf_get_string(value, &name);

                tls = nxt_mp_get(mp, sizeof(nxt_router_tlssock_t));
                if (nxt_slow_path(tls == NULL)) {
                    goto fail;
                }

                tls->name = name;
                tls->conf = skcf;

                nxt_queue_insert_tail(&tmcf->tls, &tls->link);
            }
#endif

            skcf->listen->handler = nxt_http_conn_init;
            skcf->router_conf = tmcf->router_conf;
            skcf->router_conf->count++;

            if (lscf.pass.length != 0) {
                skcf->action = nxt_http_action_create(task, tmcf, &lscf.pass);

            /* COMPATIBILITY: listener application. */
            } else if (lscf.application.length > 0) {
                skcf->action = nxt_http_pass_application(task, tmcf,
                                                         &lscf.application);
            }
        }
    }

    ret = nxt_http_routes_resolve(task, tmcf);
    if (nxt_slow_path(ret != NXT_OK)) {
        goto fail;
    }

    value = nxt_conf_get_path(conf, &access_log_path);

    if (value != NULL) {
        nxt_conf_get_string(value, &path);

        access_log = router->access_log;

        if (access_log != NULL && nxt_strstr_eq(&path, &access_log->path)) {
            nxt_thread_spin_lock(&router->lock);
            access_log->count++;
            nxt_thread_spin_unlock(&router->lock);

        } else {
            access_log = nxt_malloc(sizeof(nxt_router_access_log_t)
                                    + path.length);
            if (access_log == NULL) {
                nxt_alert(task, "failed to allocate access log structure");
                goto fail;
            }

            access_log->fd = -1;
            access_log->handler = &nxt_router_access_log_writer;
            access_log->count = 1;

            access_log->path.length = path.length;
            access_log->path.start = (u_char *) access_log
                                     + sizeof(nxt_router_access_log_t);

            nxt_memcpy(access_log->path.start, path.start, path.length);
        }

        tmcf->router_conf->access_log = access_log;
    }

    nxt_queue_add(&deleting_sockets, &router->sockets);
    nxt_queue_init(&router->sockets);

    return NXT_OK;

app_fail:

    nxt_mp_destroy(app_mp);

fail:

    nxt_queue_each(app, &tmcf->apps, nxt_app_t, link) {

        nxt_queue_remove(&app->link);
        nxt_thread_mutex_destroy(&app->mutex);
        nxt_mp_destroy(app->mem_pool);

    } nxt_queue_loop;

    return NXT_ERROR;
}


static nxt_int_t
nxt_router_conf_process_static(nxt_task_t *task, nxt_router_conf_t *rtcf,
    nxt_conf_value_t *conf)
{
    uint32_t          next, i;
    nxt_mp_t          *mp;
    nxt_str_t         *type, extension, str;
    nxt_int_t         ret;
    nxt_uint_t        exts;
    nxt_conf_value_t  *mtypes_conf, *ext_conf, *value;

    static nxt_str_t  mtypes_path = nxt_string("/mime_types");

    mp = rtcf->mem_pool;

    ret = nxt_http_static_mtypes_init(mp, &rtcf->mtypes_hash);
    if (nxt_slow_path(ret != NXT_OK)) {
        return NXT_ERROR;
    }

    if (conf == NULL) {
        return NXT_OK;
    }

    mtypes_conf = nxt_conf_get_path(conf, &mtypes_path);

    if (mtypes_conf != NULL) {
        next = 0;

        for ( ;; ) {
            ext_conf = nxt_conf_next_object_member(mtypes_conf, &str, &next);

            if (ext_conf == NULL) {
                break;
            }

            type = nxt_str_dup(mp, NULL, &str);
            if (nxt_slow_path(type == NULL)) {
                return NXT_ERROR;
            }

            if (nxt_conf_type(ext_conf) == NXT_CONF_STRING) {
                nxt_conf_get_string(ext_conf, &str);

                if (nxt_slow_path(nxt_str_dup(mp, &extension, &str) == NULL)) {
                    return NXT_ERROR;
                }

                ret = nxt_http_static_mtypes_hash_add(mp, &rtcf->mtypes_hash,
                                                      &extension, type);
                if (nxt_slow_path(ret != NXT_OK)) {
                    return NXT_ERROR;
                }

                continue;
            }

            exts = nxt_conf_array_elements_count(ext_conf);

            for (i = 0; i < exts; i++) {
                value = nxt_conf_get_array_element(ext_conf, i);

                nxt_conf_get_string(value, &str);

                if (nxt_slow_path(nxt_str_dup(mp, &extension, &str) == NULL)) {
                    return NXT_ERROR;
                }

                ret = nxt_http_static_mtypes_hash_add(mp, &rtcf->mtypes_hash,
                                                      &extension, type);
                if (nxt_slow_path(ret != NXT_OK)) {
                    return NXT_ERROR;
                }
            }
        }
    }

    return NXT_OK;
}


static nxt_app_t *
nxt_router_app_find(nxt_queue_t *queue, nxt_str_t *name)
{
    nxt_app_t  *app;

    nxt_queue_each(app, queue, nxt_app_t, link) {

        if (nxt_strstr_eq(name, &app->name)) {
            return app;
        }

    } nxt_queue_loop;

    return NULL;
}


void
nxt_router_listener_application(nxt_router_temp_conf_t *tmcf, nxt_str_t *name,
    nxt_http_action_t *action)
{
    nxt_app_t  *app;

    app = nxt_router_app_find(&tmcf->apps, name);

    if (app == NULL) {
        app = nxt_router_app_find(&tmcf->previous, name);
    }

    action->u.application = app;
    action->handler = nxt_http_application_handler;
}


static nxt_socket_conf_t *
nxt_router_socket_conf(nxt_task_t *task, nxt_router_temp_conf_t *tmcf,
    nxt_str_t *name)
{
    size_t               size;
    nxt_int_t            ret;
    nxt_bool_t           wildcard;
    nxt_sockaddr_t       *sa;
    nxt_socket_conf_t    *skcf;
    nxt_listen_socket_t  *ls;

    sa = nxt_sockaddr_parse(tmcf->mem_pool, name);
    if (nxt_slow_path(sa == NULL)) {
        nxt_alert(task, "invalid listener \"%V\"", name);
        return NULL;
    }

    sa->type = SOCK_STREAM;

    nxt_debug(task, "router listener: \"%*s\"",
              (size_t) sa->length, nxt_sockaddr_start(sa));

    skcf = nxt_mp_zget(tmcf->router_conf->mem_pool, sizeof(nxt_socket_conf_t));
    if (nxt_slow_path(skcf == NULL)) {
        return NULL;
    }

    size = nxt_sockaddr_size(sa);

    ret = nxt_router_listen_socket_find(tmcf, skcf, sa);

    if (ret != NXT_OK) {

        ls = nxt_zalloc(sizeof(nxt_listen_socket_t) + size);
        if (nxt_slow_path(ls == NULL)) {
            return NULL;
        }

        skcf->listen = ls;

        ls->sockaddr = nxt_pointer_to(ls, sizeof(nxt_listen_socket_t));
        nxt_memcpy(ls->sockaddr, sa, size);

        nxt_listen_socket_remote_size(ls);

        ls->socket = -1;
        ls->backlog = NXT_LISTEN_BACKLOG;
        ls->flags = NXT_NONBLOCK;
        ls->read_after_accept = 1;
    }

    switch (sa->u.sockaddr.sa_family) {
#if (NXT_HAVE_UNIX_DOMAIN)
    case AF_UNIX:
        wildcard = 0;
        break;
#endif
#if (NXT_INET6)
    case AF_INET6:
        wildcard = IN6_IS_ADDR_UNSPECIFIED(&sa->u.sockaddr_in6.sin6_addr);
        break;
#endif
    case AF_INET:
    default:
        wildcard = (sa->u.sockaddr_in.sin_addr.s_addr == INADDR_ANY);
        break;
    }

    if (!wildcard) {
        skcf->sockaddr = nxt_mp_zget(tmcf->router_conf->mem_pool, size);
        if (nxt_slow_path(skcf->sockaddr == NULL)) {
            return NULL;
        }

        nxt_memcpy(skcf->sockaddr, sa, size);
    }

    return skcf;
}


static nxt_int_t
nxt_router_listen_socket_find(nxt_router_temp_conf_t *tmcf,
    nxt_socket_conf_t *nskcf, nxt_sockaddr_t *sa)
{
    nxt_router_t       *router;
    nxt_queue_link_t   *qlk;
    nxt_socket_conf_t  *skcf;

    router = tmcf->router_conf->router;

    for (qlk = nxt_queue_first(&router->sockets);
         qlk != nxt_queue_tail(&router->sockets);
         qlk = nxt_queue_next(qlk))
    {
        skcf = nxt_queue_link_data(qlk, nxt_socket_conf_t, link);

        if (nxt_sockaddr_cmp(skcf->listen->sockaddr, sa)) {
            nskcf->listen = skcf->listen;

            nxt_queue_remove(qlk);
            nxt_queue_insert_tail(&keeping_sockets, qlk);

            nxt_queue_insert_tail(&updating_sockets, &nskcf->link);

            return NXT_OK;
        }
    }

    nxt_queue_insert_tail(&pending_sockets, &nskcf->link);

    return NXT_DECLINED;
}


static void
nxt_router_listen_socket_rpc_create(nxt_task_t *task,
    nxt_router_temp_conf_t *tmcf, nxt_socket_conf_t *skcf)
{
    size_t            size;
    uint32_t          stream;
    nxt_int_t         ret;
    nxt_buf_t         *b;
    nxt_port_t        *main_port, *router_port;
    nxt_runtime_t     *rt;
    nxt_socket_rpc_t  *rpc;

    rpc = nxt_mp_alloc(tmcf->mem_pool, sizeof(nxt_socket_rpc_t));
    if (rpc == NULL) {
        goto fail;
    }

    rpc->socket_conf = skcf;
    rpc->temp_conf = tmcf;

    size = nxt_sockaddr_size(skcf->listen->sockaddr);

    b = nxt_buf_mem_alloc(tmcf->mem_pool, size, 0);
    if (b == NULL) {
        goto fail;
    }

    b->mem.free = nxt_cpymem(b->mem.free, skcf->listen->sockaddr, size);

    rt = task->thread->runtime;
    main_port = rt->port_by_type[NXT_PROCESS_MAIN];
    router_port = rt->port_by_type[NXT_PROCESS_ROUTER];

    stream = nxt_port_rpc_register_handler(task, router_port,
                                           nxt_router_listen_socket_ready,
                                           nxt_router_listen_socket_error,
                                           main_port->pid, rpc);
    if (nxt_slow_path(stream == 0)) {
        goto fail;
    }

    ret = nxt_port_socket_write(task, main_port, NXT_PORT_MSG_SOCKET, -1,
                                stream, router_port->id, b);

    if (nxt_slow_path(ret != NXT_OK)) {
        nxt_port_rpc_cancel(task, router_port, stream);
        goto fail;
    }

    return;

fail:

    nxt_router_conf_error(task, tmcf);
}


static void
nxt_router_listen_socket_ready(nxt_task_t *task, nxt_port_recv_msg_t *msg,
    void *data)
{
    nxt_int_t         ret;
    nxt_socket_t      s;
    nxt_socket_rpc_t  *rpc;

    rpc = data;

    s = msg->fd;

    ret = nxt_socket_nonblocking(task, s);
    if (nxt_slow_path(ret != NXT_OK)) {
        goto fail;
    }

    nxt_socket_defer_accept(task, s, rpc->socket_conf->listen->sockaddr);

    ret = nxt_listen_socket(task, s, NXT_LISTEN_BACKLOG);
    if (nxt_slow_path(ret != NXT_OK)) {
        goto fail;
    }

    rpc->socket_conf->listen->socket = s;

    nxt_work_queue_add(&task->thread->engine->fast_work_queue,
                       nxt_router_conf_apply, task, rpc->temp_conf, NULL);

    return;

fail:

    nxt_socket_close(task, s);

    nxt_router_conf_error(task, rpc->temp_conf);
}


static void
nxt_router_listen_socket_error(nxt_task_t *task, nxt_port_recv_msg_t *msg,
    void *data)
{
    nxt_socket_rpc_t        *rpc;
    nxt_router_temp_conf_t  *tmcf;

    rpc = data;
    tmcf = rpc->temp_conf;

#if 0
    u_char                  *p;
    size_t                  size;
    uint8_t                 error;
    nxt_buf_t               *in, *out;
    nxt_sockaddr_t          *sa;

    static nxt_str_t  socket_errors[] = {
        nxt_string("ListenerSystem"),
        nxt_string("ListenerNoIPv6"),
        nxt_string("ListenerPort"),
        nxt_string("ListenerInUse"),
        nxt_string("ListenerNoAddress"),
        nxt_string("ListenerNoAccess"),
        nxt_string("ListenerPath"),
    };

    sa = rpc->socket_conf->listen->sockaddr;

    in = nxt_buf_chk_make_plain(tmcf->mem_pool, msg->buf, msg->size);

    if (nxt_slow_path(in == NULL)) {
        return;
    }

    p = in->mem.pos;

    error = *p++;

    size = nxt_length("listen socket error: ")
           + nxt_length("{listener: \"\", code:\"\", message: \"\"}")
           + sa->length + socket_errors[error].length + (in->mem.free - p);

    out = nxt_buf_mem_alloc(tmcf->mem_pool, size, 0);
    if (nxt_slow_path(out == NULL)) {
        return;
    }

    out->mem.free = nxt_sprintf(out->mem.free, out->mem.end,
                        "listen socket error: "
                        "{listener: \"%*s\", code:\"%V\", message: \"%*s\"}",
                        (size_t) sa->length, nxt_sockaddr_start(sa),
                        &socket_errors[error], in->mem.free - p, p);

    nxt_debug(task, "%*s", out->mem.free - out->mem.pos, out->mem.pos);
#endif

    nxt_router_conf_error(task, tmcf);
}


#if (NXT_TLS)

static void
nxt_router_tls_rpc_create(nxt_task_t *task, nxt_router_temp_conf_t *tmcf,
    nxt_router_tlssock_t *tls)
{
    nxt_socket_rpc_t  *rpc;

    rpc = nxt_mp_alloc(tmcf->mem_pool, sizeof(nxt_socket_rpc_t));
    if (rpc == NULL) {
        nxt_router_conf_error(task, tmcf);
        return;
    }

    rpc->socket_conf = tls->conf;
    rpc->temp_conf = tmcf;

    nxt_cert_store_get(task, &tls->name, tmcf->mem_pool,
                       nxt_router_tls_rpc_handler, rpc);
}


static void
nxt_router_tls_rpc_handler(nxt_task_t *task, nxt_port_recv_msg_t *msg,
    void *data)
{
    nxt_mp_t               *mp;
    nxt_int_t              ret;
    nxt_tls_conf_t         *tlscf;
    nxt_socket_rpc_t       *rpc;
    nxt_router_temp_conf_t *tmcf;

    nxt_debug(task, "tls rpc handler");

    rpc = data;
    tmcf = rpc->temp_conf;

    if (msg == NULL || msg->port_msg.type == _NXT_PORT_MSG_RPC_ERROR) {
        goto fail;
    }

    mp = tmcf->router_conf->mem_pool;

    tlscf = nxt_mp_zget(mp, sizeof(nxt_tls_conf_t));
    if (nxt_slow_path(tlscf == NULL)) {
        goto fail;
    }

    tlscf->chain_file = msg->fd;

    ret = task->thread->runtime->tls->server_init(task, tlscf);
    if (nxt_slow_path(ret != NXT_OK)) {
        goto fail;
    }

    rpc->socket_conf->tls = tlscf;

    nxt_work_queue_add(&task->thread->engine->fast_work_queue,
                       nxt_router_conf_apply, task, tmcf, NULL);
    return;

fail:

    nxt_router_conf_error(task, tmcf);
}

#endif


static void
nxt_router_app_rpc_create(nxt_task_t *task,
    nxt_router_temp_conf_t *tmcf, nxt_app_t *app)
{
    size_t         size;
    uint32_t       stream;
    nxt_int_t      ret;
    nxt_buf_t      *b;
    nxt_port_t     *main_port, *router_port;
    nxt_runtime_t  *rt;
    nxt_app_rpc_t  *rpc;

    rpc = nxt_mp_alloc(tmcf->mem_pool, sizeof(nxt_app_rpc_t));
    if (rpc == NULL) {
        goto fail;
    }

    rpc->app = app;
    rpc->temp_conf = tmcf;

    nxt_debug(task, "app '%V' prefork", &app->name);

    size = app->name.length + 1 + app->conf.length;

    b = nxt_buf_mem_alloc(tmcf->mem_pool, size, 0);
    if (nxt_slow_path(b == NULL)) {
        goto fail;
    }

    nxt_buf_cpystr(b, &app->name);
    *b->mem.free++ = '\0';
    nxt_buf_cpystr(b, &app->conf);

    rt = task->thread->runtime;
    main_port = rt->port_by_type[NXT_PROCESS_MAIN];
    router_port = rt->port_by_type[NXT_PROCESS_ROUTER];

    stream = nxt_port_rpc_register_handler(task, router_port,
                                           nxt_router_app_prefork_ready,
                                           nxt_router_app_prefork_error,
                                           -1, rpc);
    if (nxt_slow_path(stream == 0)) {
        goto fail;
    }

    ret = nxt_port_socket_write(task, main_port, NXT_PORT_MSG_START_PROCESS,
                                -1, stream, router_port->id, b);

    if (nxt_slow_path(ret != NXT_OK)) {
        nxt_port_rpc_cancel(task, router_port, stream);
        goto fail;
    }

    app->pending_processes++;

    return;

fail:

    nxt_router_conf_error(task, tmcf);
}


static void
nxt_router_app_prefork_ready(nxt_task_t *task, nxt_port_recv_msg_t *msg,
    void *data)
{
    nxt_app_t           *app;
    nxt_port_t          *port;
    nxt_app_rpc_t       *rpc;
    nxt_event_engine_t  *engine;

    rpc = data;
    app = rpc->app;

    port = msg->u.new_port;
    port->app = app;

    app->pending_processes--;
    app->processes++;
    app->idle_processes++;

    engine = task->thread->engine;

    nxt_queue_insert_tail(&app->ports, &port->app_link);
    nxt_queue_insert_tail(&app->spare_ports, &port->idle_link);

    port->idle_start = 0;

    nxt_port_inc_use(port);

    nxt_work_queue_add(&engine->fast_work_queue,
                       nxt_router_conf_apply, task, rpc->temp_conf, NULL);
}


static void
nxt_router_app_prefork_error(nxt_task_t *task, nxt_port_recv_msg_t *msg,
    void *data)
{
    nxt_app_t               *app;
    nxt_app_rpc_t           *rpc;
    nxt_router_temp_conf_t  *tmcf;

    rpc = data;
    app = rpc->app;
    tmcf = rpc->temp_conf;

    nxt_log(task, NXT_LOG_WARN, "failed to start application \"%V\"",
            &app->name);

    app->pending_processes--;

    nxt_router_conf_error(task, tmcf);
}


static nxt_int_t
nxt_router_engines_create(nxt_task_t *task, nxt_router_t *router,
    nxt_router_temp_conf_t *tmcf, const nxt_event_interface_t *interface)
{
    nxt_int_t                 ret;
    nxt_uint_t                n, threads;
    nxt_queue_link_t          *qlk;
    nxt_router_engine_conf_t  *recf;

    threads = tmcf->router_conf->threads;

    tmcf->engines = nxt_array_create(tmcf->mem_pool, threads,
                                     sizeof(nxt_router_engine_conf_t));
    if (nxt_slow_path(tmcf->engines == NULL)) {
        return NXT_ERROR;
    }

    n = 0;

    for (qlk = nxt_queue_first(&router->engines);
         qlk != nxt_queue_tail(&router->engines);
         qlk = nxt_queue_next(qlk))
    {
        recf = nxt_array_zero_add(tmcf->engines);
        if (nxt_slow_path(recf == NULL)) {
            return NXT_ERROR;
        }

        recf->engine = nxt_queue_link_data(qlk, nxt_event_engine_t, link0);

        if (n < threads) {
            recf->action = NXT_ROUTER_ENGINE_KEEP;
            ret = nxt_router_engine_conf_update(tmcf, recf);

        } else {
            recf->action = NXT_ROUTER_ENGINE_DELETE;
            ret = nxt_router_engine_conf_delete(tmcf, recf);
        }

        if (nxt_slow_path(ret != NXT_OK)) {
            return ret;
        }

        n++;
    }

    tmcf->new_threads = n;

    while (n < threads) {
        recf = nxt_array_zero_add(tmcf->engines);
        if (nxt_slow_path(recf == NULL)) {
            return NXT_ERROR;
        }

        recf->action = NXT_ROUTER_ENGINE_ADD;

        recf->engine = nxt_event_engine_create(task, interface, NULL, 0, 0);
        if (nxt_slow_path(recf->engine == NULL)) {
            return NXT_ERROR;
        }

        ret = nxt_router_engine_conf_create(tmcf, recf);
        if (nxt_slow_path(ret != NXT_OK)) {
            return ret;
        }

        n++;
    }

    return NXT_OK;
}


static nxt_int_t
nxt_router_engine_conf_create(nxt_router_temp_conf_t *tmcf,
    nxt_router_engine_conf_t *recf)
{
    nxt_int_t  ret;

    ret = nxt_router_engine_joints_create(tmcf, recf, &creating_sockets,
                                          nxt_router_listen_socket_create);
    if (nxt_slow_path(ret != NXT_OK)) {
        return ret;
    }

    ret = nxt_router_engine_joints_create(tmcf, recf, &updating_sockets,
                                          nxt_router_listen_socket_create);
    if (nxt_slow_path(ret != NXT_OK)) {
        return ret;
    }

    return ret;
}


static nxt_int_t
nxt_router_engine_conf_update(nxt_router_temp_conf_t *tmcf,
    nxt_router_engine_conf_t *recf)
{
    nxt_int_t  ret;

    ret = nxt_router_engine_joints_create(tmcf, recf, &creating_sockets,
                                          nxt_router_listen_socket_create);
    if (nxt_slow_path(ret != NXT_OK)) {
        return ret;
    }

    ret = nxt_router_engine_joints_create(tmcf, recf, &updating_sockets,
                                          nxt_router_listen_socket_update);
    if (nxt_slow_path(ret != NXT_OK)) {
        return ret;
    }

    ret = nxt_router_engine_joints_delete(tmcf, recf, &deleting_sockets);
    if (nxt_slow_path(ret != NXT_OK)) {
        return ret;
    }

    return ret;
}


static nxt_int_t
nxt_router_engine_conf_delete(nxt_router_temp_conf_t *tmcf,
    nxt_router_engine_conf_t *recf)
{
    nxt_int_t  ret;

    ret = nxt_router_engine_quit(tmcf, recf);
    if (nxt_slow_path(ret != NXT_OK)) {
        return ret;
    }

    ret = nxt_router_engine_joints_delete(tmcf, recf, &updating_sockets);
    if (nxt_slow_path(ret != NXT_OK)) {
        return ret;
    }

    return nxt_router_engine_joints_delete(tmcf, recf, &deleting_sockets);
}


static nxt_int_t
nxt_router_engine_joints_create(nxt_router_temp_conf_t *tmcf,
    nxt_router_engine_conf_t *recf, nxt_queue_t *sockets,
    nxt_work_handler_t handler)
{
    nxt_int_t                ret;
    nxt_joint_job_t          *job;
    nxt_queue_link_t         *qlk;
    nxt_socket_conf_t        *skcf;
    nxt_socket_conf_joint_t  *joint;

    for (qlk = nxt_queue_first(sockets);
         qlk != nxt_queue_tail(sockets);
         qlk = nxt_queue_next(qlk))
    {
        job = nxt_mp_get(tmcf->mem_pool, sizeof(nxt_joint_job_t));
        if (nxt_slow_path(job == NULL)) {
            return NXT_ERROR;
        }

        job->work.next = recf->jobs;
        recf->jobs = &job->work;

        job->task = tmcf->engine->task;
        job->work.handler = handler;
        job->work.task = &job->task;
        job->work.obj = job;
        job->tmcf = tmcf;

        tmcf->count++;

        joint = nxt_mp_alloc(tmcf->router_conf->mem_pool,
                             sizeof(nxt_socket_conf_joint_t));
        if (nxt_slow_path(joint == NULL)) {
            return NXT_ERROR;
        }

        job->work.data = joint;

        ret = nxt_upstreams_joint_create(tmcf, &joint->upstreams);
        if (nxt_slow_path(ret != NXT_OK)) {
            return ret;
        }

        joint->count = 1;

        skcf = nxt_queue_link_data(qlk, nxt_socket_conf_t, link);
        skcf->count++;
        joint->socket_conf = skcf;

        joint->engine = recf->engine;
    }

    return NXT_OK;
}


static nxt_int_t
nxt_router_engine_quit(nxt_router_temp_conf_t *tmcf,
    nxt_router_engine_conf_t *recf)
{
    nxt_joint_job_t  *job;

    job = nxt_mp_get(tmcf->mem_pool, sizeof(nxt_joint_job_t));
    if (nxt_slow_path(job == NULL)) {
        return NXT_ERROR;
    }

    job->work.next = recf->jobs;
    recf->jobs = &job->work;

    job->task = tmcf->engine->task;
    job->work.handler = nxt_router_worker_thread_quit;
    job->work.task = &job->task;
    job->work.obj = NULL;
    job->work.data = NULL;
    job->tmcf = NULL;

    return NXT_OK;
}


static nxt_int_t
nxt_router_engine_joints_delete(nxt_router_temp_conf_t *tmcf,
    nxt_router_engine_conf_t *recf, nxt_queue_t *sockets)
{
    nxt_joint_job_t   *job;
    nxt_queue_link_t  *qlk;

    for (qlk = nxt_queue_first(sockets);
         qlk != nxt_queue_tail(sockets);
         qlk = nxt_queue_next(qlk))
    {
        job = nxt_mp_get(tmcf->mem_pool, sizeof(nxt_joint_job_t));
        if (nxt_slow_path(job == NULL)) {
            return NXT_ERROR;
        }

        job->work.next = recf->jobs;
        recf->jobs = &job->work;

        job->task = tmcf->engine->task;
        job->work.handler = nxt_router_listen_socket_delete;
        job->work.task = &job->task;
        job->work.obj = job;
        job->work.data = nxt_queue_link_data(qlk, nxt_socket_conf_t, link);
        job->tmcf = tmcf;

        tmcf->count++;
    }

    return NXT_OK;
}


static nxt_int_t
nxt_router_threads_create(nxt_task_t *task, nxt_runtime_t *rt,
    nxt_router_temp_conf_t *tmcf)
{
    nxt_int_t                 ret;
    nxt_uint_t                i, threads;
    nxt_router_engine_conf_t  *recf;

    recf = tmcf->engines->elts;
    threads = tmcf->router_conf->threads;

    for (i = tmcf->new_threads; i < threads; i++) {
        ret = nxt_router_thread_create(task, rt, recf[i].engine);
        if (nxt_slow_path(ret != NXT_OK)) {
            return ret;
        }
    }

    return NXT_OK;
}


static nxt_int_t
nxt_router_thread_create(nxt_task_t *task, nxt_runtime_t *rt,
    nxt_event_engine_t *engine)
{
    nxt_int_t            ret;
    nxt_thread_link_t    *link;
    nxt_thread_handle_t  handle;

    link = nxt_zalloc(sizeof(nxt_thread_link_t));

    if (nxt_slow_path(link == NULL)) {
        return NXT_ERROR;
    }

    link->start = nxt_router_thread_start;
    link->engine = engine;
    link->work.handler = nxt_router_thread_exit_handler;
    link->work.task = task;
    link->work.data = link;

    nxt_queue_insert_tail(&rt->engines, &engine->link);

    ret = nxt_thread_create(&handle, link);

    if (nxt_slow_path(ret != NXT_OK)) {
        nxt_queue_remove(&engine->link);
    }

    return ret;
}


static void
nxt_router_apps_sort(nxt_task_t *task, nxt_router_t *router,
    nxt_router_temp_conf_t *tmcf)
{
    nxt_app_t  *app;

    nxt_queue_each(app, &router->apps, nxt_app_t, link) {

        nxt_router_app_unlink(task, app);

    } nxt_queue_loop;

    nxt_queue_add(&router->apps, &tmcf->previous);
    nxt_queue_add(&router->apps, &tmcf->apps);
}


static void
nxt_router_engines_post(nxt_router_t *router, nxt_router_temp_conf_t *tmcf)
{
    nxt_uint_t                n;
    nxt_event_engine_t        *engine;
    nxt_router_engine_conf_t  *recf;

    recf = tmcf->engines->elts;

    for (n = tmcf->engines->nelts; n != 0; n--) {
        engine = recf->engine;

        switch (recf->action) {

        case NXT_ROUTER_ENGINE_KEEP:
            break;

        case NXT_ROUTER_ENGINE_ADD:
            nxt_queue_insert_tail(&router->engines, &engine->link0);
            break;

        case NXT_ROUTER_ENGINE_DELETE:
            nxt_queue_remove(&engine->link0);
            break;
        }

        nxt_router_engine_post(engine, recf->jobs);

        recf++;
    }
}


static void
nxt_router_engine_post(nxt_event_engine_t *engine, nxt_work_t *jobs)
{
    nxt_work_t  *work, *next;

    for (work = jobs; work != NULL; work = next) {
        next = work->next;
        work->next = NULL;

        nxt_event_engine_post(engine, work);
    }
}


static nxt_port_handlers_t  nxt_router_app_port_handlers = {
    .rpc_error = nxt_port_rpc_handler,
    .mmap      = nxt_port_mmap_handler,
    .data      = nxt_port_rpc_handler,
    .oosm      = nxt_router_oosm_handler,
};


static void
nxt_router_thread_start(void *data)
{
    nxt_int_t           ret;
    nxt_port_t          *port;
    nxt_task_t          *task;
    nxt_thread_t        *thread;
    nxt_thread_link_t   *link;
    nxt_event_engine_t  *engine;

    link = data;
    engine = link->engine;
    task = &engine->task;

    thread = nxt_thread();

    nxt_event_engine_thread_adopt(engine);

    /* STUB */
    thread->runtime = engine->task.thread->runtime;

    engine->task.thread = thread;
    engine->task.log = thread->log;
    thread->engine = engine;
    thread->task = &engine->task;
#if 0
    thread->fiber = &engine->fibers->fiber;
#endif

    engine->mem_pool = nxt_mp_create(4096, 128, 1024, 64);
    if (nxt_slow_path(engine->mem_pool == NULL)) {
        return;
    }

    port = nxt_port_new(task, nxt_port_get_next_id(), nxt_pid,
                        NXT_PROCESS_ROUTER);
    if (nxt_slow_path(port == NULL)) {
        return;
    }

    ret = nxt_port_socket_init(task, port, 0);
    if (nxt_slow_path(ret != NXT_OK)) {
        nxt_port_use(task, port, -1);
        return;
    }

    engine->port = port;

    nxt_port_enable(task, port, &nxt_router_app_port_handlers);

    nxt_event_engine_start(engine);
}


static void
nxt_router_listen_socket_create(nxt_task_t *task, void *obj, void *data)
{
    nxt_joint_job_t          *job;
    nxt_socket_conf_t        *skcf;
    nxt_listen_event_t       *lev;
    nxt_listen_socket_t      *ls;
    nxt_thread_spinlock_t    *lock;
    nxt_socket_conf_joint_t  *joint;

    job = obj;
    joint = data;

    nxt_queue_insert_tail(&task->thread->engine->joints, &joint->link);

    skcf = joint->socket_conf;
    ls = skcf->listen;

    lev = nxt_listen_event(task, ls);
    if (nxt_slow_path(lev == NULL)) {
        nxt_router_listen_socket_release(task, skcf);
        return;
    }

    lev->socket.data = joint;

    lock = &skcf->router_conf->router->lock;

    nxt_thread_spin_lock(lock);
    ls->count++;
    nxt_thread_spin_unlock(lock);

    job->work.next = NULL;
    job->work.handler = nxt_router_conf_wait;

    nxt_event_engine_post(job->tmcf->engine, &job->work);
}


nxt_inline nxt_listen_event_t *
nxt_router_listen_event(nxt_queue_t *listen_connections,
    nxt_socket_conf_t *skcf)
{
    nxt_socket_t        fd;
    nxt_queue_link_t    *qlk;
    nxt_listen_event_t  *lev;

    fd = skcf->listen->socket;

    for (qlk = nxt_queue_first(listen_connections);
         qlk != nxt_queue_tail(listen_connections);
         qlk = nxt_queue_next(qlk))
    {
        lev = nxt_queue_link_data(qlk, nxt_listen_event_t, link);

        if (fd == lev->socket.fd) {
            return lev;
        }
    }

    return NULL;
}


static void
nxt_router_listen_socket_update(nxt_task_t *task, void *obj, void *data)
{
    nxt_joint_job_t          *job;
    nxt_event_engine_t       *engine;
    nxt_listen_event_t       *lev;
    nxt_socket_conf_joint_t  *joint, *old;

    job = obj;
    joint = data;

    engine = task->thread->engine;

    nxt_queue_insert_tail(&engine->joints, &joint->link);

    lev = nxt_router_listen_event(&engine->listen_connections,
                                  joint->socket_conf);

    old = lev->socket.data;
    lev->socket.data = joint;
    lev->listen = joint->socket_conf->listen;

    job->work.next = NULL;
    job->work.handler = nxt_router_conf_wait;

    nxt_event_engine_post(job->tmcf->engine, &job->work);

    /*
     * The task is allocated from configuration temporary
     * memory pool so it can be freed after engine post operation.
     */

    nxt_router_conf_release(&engine->task, old);
}


static void
nxt_router_listen_socket_delete(nxt_task_t *task, void *obj, void *data)
{
    nxt_joint_job_t     *job;
    nxt_socket_conf_t   *skcf;
    nxt_listen_event_t  *lev;
    nxt_event_engine_t  *engine;

    job = obj;
    skcf = data;

    engine = task->thread->engine;

    lev = nxt_router_listen_event(&engine->listen_connections, skcf);

    nxt_fd_event_delete(engine, &lev->socket);

    nxt_debug(task, "engine %p: listen socket delete: %d", engine,
              lev->socket.fd);

    lev->timer.handler = nxt_router_listen_socket_close;
    lev->timer.work_queue = &engine->fast_work_queue;

    nxt_timer_add(engine, &lev->timer, 0);

    job->work.next = NULL;
    job->work.handler = nxt_router_conf_wait;

    nxt_event_engine_post(job->tmcf->engine, &job->work);
}


static void
nxt_router_worker_thread_quit(nxt_task_t *task, void *obj, void *data)
{
    nxt_event_engine_t  *engine;

    nxt_debug(task, "router worker thread quit");

    engine = task->thread->engine;

    engine->shutdown = 1;

    if (nxt_queue_is_empty(&engine->joints)) {
        nxt_thread_exit(task->thread);
    }
}


static void
nxt_router_listen_socket_close(nxt_task_t *task, void *obj, void *data)
{
    nxt_timer_t              *timer;
    nxt_listen_event_t       *lev;
    nxt_socket_conf_joint_t  *joint;

    timer = obj;
    lev = nxt_timer_data(timer, nxt_listen_event_t, timer);

    nxt_debug(task, "engine %p: listen socket close: %d", task->thread->engine,
              lev->socket.fd);

    nxt_queue_remove(&lev->link);

    joint = lev->socket.data;
    lev->socket.data = NULL;

    /* 'task' refers to lev->task and we cannot use after nxt_free() */
    task = &task->thread->engine->task;

    nxt_router_listen_socket_release(task, joint->socket_conf);

    nxt_router_listen_event_release(task, lev, joint);
}


static void
nxt_router_listen_socket_release(nxt_task_t *task, nxt_socket_conf_t *skcf)
{
    nxt_listen_socket_t    *ls;
    nxt_thread_spinlock_t  *lock;

    ls = skcf->listen;
    lock = &skcf->router_conf->router->lock;

    nxt_thread_spin_lock(lock);

    nxt_debug(task, "engine %p: listen socket release: ls->count %D",
              task->thread->engine, ls->count);

    if (--ls->count != 0) {
        ls = NULL;
    }

    nxt_thread_spin_unlock(lock);

    if (ls != NULL) {
        nxt_socket_close(task, ls->socket);
        nxt_free(ls);
    }
}


void
nxt_router_listen_event_release(nxt_task_t *task, nxt_listen_event_t *lev,
    nxt_socket_conf_joint_t *joint)
{
    nxt_event_engine_t  *engine;

    nxt_debug(task, "listen event count: %D", lev->count);

    engine = task->thread->engine;

    if (--lev->count == 0) {
        if (lev->next != NULL) {
            nxt_sockaddr_cache_free(engine, lev->next);

            nxt_conn_free(task, lev->next);
        }

        nxt_free(lev);
    }

    if (joint != NULL) {
        nxt_router_conf_release(task, joint);
    }

    if (engine->shutdown && nxt_queue_is_empty(&engine->joints)) {
        nxt_thread_exit(task->thread);
    }
}


void
nxt_router_conf_release(nxt_task_t *task, nxt_socket_conf_joint_t *joint)
{
    nxt_socket_conf_t      *skcf;
    nxt_router_conf_t      *rtcf;
    nxt_thread_spinlock_t  *lock;

    nxt_debug(task, "conf joint %p count: %D", joint, joint->count);

    if (--joint->count != 0) {
        return;
    }

    nxt_queue_remove(&joint->link);

    /*
     * The joint content can not be safely used after the critical
     * section protected by the spinlock because its memory pool may
     * be already destroyed by another thread.
     */
    skcf = joint->socket_conf;
    rtcf = skcf->router_conf;
    lock = &rtcf->router->lock;

    nxt_thread_spin_lock(lock);

    nxt_debug(task, "conf skcf %p: %D, rtcf %p: %D", skcf, skcf->count,
              rtcf, rtcf->count);

    if (--skcf->count != 0) {
        skcf = NULL;
        rtcf = NULL;

    } else {
        nxt_queue_remove(&skcf->link);

        if (--rtcf->count != 0) {
            rtcf = NULL;
        }
    }

    nxt_thread_spin_unlock(lock);

    if (skcf != NULL) {
        if (skcf->action != NULL) {
            nxt_http_action_cleanup(task, skcf->action);
        }

#if (NXT_TLS)
        if (skcf->tls != NULL) {
            task->thread->runtime->tls->server_free(task, skcf->tls);
        }
#endif
    }

    /* TODO remove engine->port */
    /* TODO excude from connected ports */

    if (rtcf != NULL) {
        nxt_debug(task, "old router conf is destroyed");

        nxt_http_routes_cleanup(task, rtcf->routes);

        nxt_router_access_log_release(task, lock, rtcf->access_log);

        nxt_mp_thread_adopt(rtcf->mem_pool);

        nxt_mp_destroy(rtcf->mem_pool);
    }
}


static void
nxt_router_access_log_writer(nxt_task_t *task, nxt_http_request_t *r,
    nxt_router_access_log_t *access_log)
{
    size_t     size;
    u_char     *buf, *p;
    nxt_off_t  bytes;

    static nxt_time_string_t  date_cache = {
        (nxt_atomic_uint_t) -1,
        nxt_router_access_log_date,
        "%02d/%s/%4d:%02d:%02d:%02d %c%02d%02d",
        nxt_length("31/Dec/1986:19:40:00 +0300"),
        NXT_THREAD_TIME_LOCAL,
        NXT_THREAD_TIME_SEC,
    };

    size = r->remote->address_length
           + 6                  /* ' - - [' */
           + date_cache.size
           + 3                  /* '] "' */
           + r->method->length
           + 1                  /* space */
           + r->target.length
           + 1                  /* space */
           + r->version.length
           + 2                  /* '" ' */
           + 3                  /* status */
           + 1                  /* space */
           + NXT_OFF_T_LEN
           + 2                  /* ' "' */
           + (r->referer != NULL ? r->referer->value_length : 1)
           + 3                  /* '" "' */
           + (r->user_agent != NULL ? r->user_agent->value_length : 1)
           + 2                  /* '"\n' */
    ;

    buf = nxt_mp_nget(r->mem_pool, size);
    if (nxt_slow_path(buf == NULL)) {
        return;
    }

    p = nxt_cpymem(buf, nxt_sockaddr_address(r->remote),
                   r->remote->address_length);

    p = nxt_cpymem(p, " - - [", 6);

    p = nxt_thread_time_string(task->thread, &date_cache, p);

    p = nxt_cpymem(p, "] \"", 3);

    if (r->method->length != 0) {
        p = nxt_cpymem(p, r->method->start, r->method->length);

        if (r->target.length != 0) {
            *p++ = ' ';
            p = nxt_cpymem(p, r->target.start, r->target.length);

            if (r->version.length != 0) {
                *p++ = ' ';
                p = nxt_cpymem(p, r->version.start, r->version.length);
            }
        }

    } else {
        *p++ = '-';
    }

    p = nxt_cpymem(p, "\" ", 2);

    p = nxt_sprintf(p, p + 3, "%03d", r->status);

    *p++ = ' ';

    bytes = nxt_http_proto[r->protocol].body_bytes_sent(task, r->proto);

    p = nxt_sprintf(p, p + NXT_OFF_T_LEN, "%O", bytes);

    p = nxt_cpymem(p, " \"", 2);

    if (r->referer != NULL) {
        p = nxt_cpymem(p, r->referer->value, r->referer->value_length);

    } else {
        *p++ = '-';
    }

    p = nxt_cpymem(p, "\" \"", 3);

    if (r->user_agent != NULL) {
        p = nxt_cpymem(p, r->user_agent->value, r->user_agent->value_length);

    } else {
        *p++ = '-';
    }

    p = nxt_cpymem(p, "\"\n", 2);

    nxt_fd_write(access_log->fd, buf, p - buf);
}


static u_char *
nxt_router_access_log_date(u_char *buf, nxt_realtime_t *now, struct tm *tm,
    size_t size, const char *format)
{
    u_char  sign;
    time_t  gmtoff;

    static const char  *month[] = { "Jan", "Feb", "Mar", "Apr", "May", "Jun",
                                    "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" };

    gmtoff = nxt_timezone(tm) / 60;

    if (gmtoff < 0) {
        gmtoff = -gmtoff;
        sign = '-';

    } else {
        sign = '+';
    }

    return nxt_sprintf(buf, buf + size, format,
                       tm->tm_mday, month[tm->tm_mon], tm->tm_year + 1900,
                       tm->tm_hour, tm->tm_min, tm->tm_sec,
                       sign, gmtoff / 60, gmtoff % 60);
}


static void
nxt_router_access_log_open(nxt_task_t *task, nxt_router_temp_conf_t *tmcf)
{
    uint32_t                 stream;
    nxt_int_t                ret;
    nxt_buf_t                *b;
    nxt_port_t               *main_port, *router_port;
    nxt_runtime_t            *rt;
    nxt_router_access_log_t  *access_log;

    access_log = tmcf->router_conf->access_log;

    b = nxt_buf_mem_alloc(tmcf->mem_pool, access_log->path.length + 1, 0);
    if (nxt_slow_path(b == NULL)) {
        goto fail;
    }

    nxt_buf_cpystr(b, &access_log->path);
    *b->mem.free++ = '\0';

    rt = task->thread->runtime;
    main_port = rt->port_by_type[NXT_PROCESS_MAIN];
    router_port = rt->port_by_type[NXT_PROCESS_ROUTER];

    stream = nxt_port_rpc_register_handler(task, router_port,
                                           nxt_router_access_log_ready,
                                           nxt_router_access_log_error,
                                           -1, tmcf);
    if (nxt_slow_path(stream == 0)) {
        goto fail;
    }

    ret = nxt_port_socket_write(task, main_port, NXT_PORT_MSG_ACCESS_LOG, -1,
                                stream, router_port->id, b);

    if (nxt_slow_path(ret != NXT_OK)) {
        nxt_port_rpc_cancel(task, router_port, stream);
        goto fail;
    }

    return;

fail:

    nxt_router_conf_error(task, tmcf);
}


static void
nxt_router_access_log_ready(nxt_task_t *task, nxt_port_recv_msg_t *msg,
    void *data)
{
    nxt_router_temp_conf_t   *tmcf;
    nxt_router_access_log_t  *access_log;

    tmcf = data;

    access_log = tmcf->router_conf->access_log;

    access_log->fd = msg->fd;

    nxt_work_queue_add(&task->thread->engine->fast_work_queue,
                       nxt_router_conf_apply, task, tmcf, NULL);
}


static void
nxt_router_access_log_error(nxt_task_t *task, nxt_port_recv_msg_t *msg,
    void *data)
{
    nxt_router_temp_conf_t  *tmcf;

    tmcf = data;

    nxt_router_conf_error(task, tmcf);
}


static void
nxt_router_access_log_release(nxt_task_t *task, nxt_thread_spinlock_t *lock,
    nxt_router_access_log_t *access_log)
{
    if (access_log == NULL) {
        return;
    }

    nxt_thread_spin_lock(lock);

    if (--access_log->count != 0) {
        access_log = NULL;
    }

    nxt_thread_spin_unlock(lock);

    if (access_log != NULL) {

        if (access_log->fd != -1) {
            nxt_fd_close(access_log->fd);
        }

        nxt_free(access_log);
    }
}


typedef struct {
    nxt_mp_t                 *mem_pool;
    nxt_router_access_log_t  *access_log;
} nxt_router_access_log_reopen_t;


void
nxt_router_access_log_reopen_handler(nxt_task_t *task, nxt_port_recv_msg_t *msg)
{
    nxt_mp_t                        *mp;
    uint32_t                        stream;
    nxt_int_t                       ret;
    nxt_buf_t                       *b;
    nxt_port_t                      *main_port, *router_port;
    nxt_runtime_t                   *rt;
    nxt_router_access_log_t         *access_log;
    nxt_router_access_log_reopen_t  *reopen;

    access_log = nxt_router->access_log;

    if (access_log == NULL) {
        return;
    }

    mp = nxt_mp_create(1024, 128, 256, 32);
    if (nxt_slow_path(mp == NULL)) {
        return;
    }

    reopen = nxt_mp_get(mp, sizeof(nxt_router_access_log_reopen_t));
    if (nxt_slow_path(reopen == NULL)) {
        goto fail;
    }

    reopen->mem_pool = mp;
    reopen->access_log = access_log;

    b = nxt_buf_mem_alloc(mp, access_log->path.length + 1, 0);
    if (nxt_slow_path(b == NULL)) {
        goto fail;
    }

    b->completion_handler = nxt_router_access_log_reopen_completion;

    nxt_buf_cpystr(b, &access_log->path);
    *b->mem.free++ = '\0';

    rt = task->thread->runtime;
    main_port = rt->port_by_type[NXT_PROCESS_MAIN];
    router_port = rt->port_by_type[NXT_PROCESS_ROUTER];

    stream = nxt_port_rpc_register_handler(task, router_port,
                                           nxt_router_access_log_reopen_ready,
                                           nxt_router_access_log_reopen_error,
                                           -1, reopen);
    if (nxt_slow_path(stream == 0)) {
        goto fail;
    }

    ret = nxt_port_socket_write(task, main_port, NXT_PORT_MSG_ACCESS_LOG, -1,
                                stream, router_port->id, b);

    if (nxt_slow_path(ret != NXT_OK)) {
        nxt_port_rpc_cancel(task, router_port, stream);
        goto fail;
    }

    nxt_mp_retain(mp);

    return;

fail:

    nxt_mp_destroy(mp);
}


static void
nxt_router_access_log_reopen_completion(nxt_task_t *task, void *obj, void *data)
{
    nxt_mp_t   *mp;
    nxt_buf_t  *b;

    b = obj;
    mp = b->data;

    nxt_mp_release(mp);
}


static void
nxt_router_access_log_reopen_ready(nxt_task_t *task, nxt_port_recv_msg_t *msg,
    void *data)
{
    nxt_router_access_log_t         *access_log;
    nxt_router_access_log_reopen_t  *reopen;

    reopen = data;

    access_log = reopen->access_log;

    if (access_log == nxt_router->access_log) {

        if (nxt_slow_path(dup2(msg->fd, access_log->fd) == -1)) {
            nxt_alert(task, "dup2(%FD, %FD) failed %E",
                      msg->fd, access_log->fd, nxt_errno);
        }
    }

    nxt_fd_close(msg->fd);
    nxt_mp_release(reopen->mem_pool);
}


static void
nxt_router_access_log_reopen_error(nxt_task_t *task, nxt_port_recv_msg_t *msg,
    void *data)
{
    nxt_router_access_log_reopen_t  *reopen;

    reopen = data;

    nxt_mp_release(reopen->mem_pool);
}


static void
nxt_router_thread_exit_handler(nxt_task_t *task, void *obj, void *data)
{
    nxt_port_t           *port;
    nxt_thread_link_t    *link;
    nxt_event_engine_t   *engine;
    nxt_thread_handle_t  handle;

    handle = (nxt_thread_handle_t) obj;
    link = data;

    nxt_thread_wait(handle);

    engine = link->engine;

    nxt_queue_remove(&engine->link);

    port = engine->port;

    // TODO notify all apps

    port->engine = task->thread->engine;
    nxt_mp_thread_adopt(port->mem_pool);
    nxt_port_use(task, port, -1);

    nxt_mp_thread_adopt(engine->mem_pool);
    nxt_mp_destroy(engine->mem_pool);

    nxt_event_engine_free(engine);

    nxt_free(link);
}


static void
nxt_router_response_ready_handler(nxt_task_t *task, nxt_port_recv_msg_t *msg,
    void *data)
{
    nxt_int_t               ret;
    nxt_buf_t               *b, *next;
    nxt_port_t              *app_port;
    nxt_unit_field_t        *f;
    nxt_http_field_t        *field;
    nxt_http_request_t      *r;
    nxt_unit_response_t     *resp;
    nxt_request_app_link_t  *req_app_link;
    nxt_request_rpc_data_t  *req_rpc_data;

    b = msg->buf;
    req_rpc_data = data;

    if (msg->size == 0) {
        b = NULL;
    }

    r = req_rpc_data->request;
    if (nxt_slow_path(r == NULL)) {
        return;
    }

    if (r->error) {
        nxt_request_rpc_data_unlink(task, req_rpc_data);
        return;
    }

    if (msg->port_msg.last != 0) {
        nxt_debug(task, "router data create last buf");

        nxt_buf_chain_add(&b, nxt_http_buf_last(r));

        nxt_request_rpc_data_unlink(task, req_rpc_data);

    } else {
        if (req_rpc_data->app != NULL && req_rpc_data->app->timeout != 0) {
            r->timer.handler = nxt_router_app_timeout;
            r->timer_data = req_rpc_data;
            nxt_timer_add(task->thread->engine, &r->timer,
                          req_rpc_data->app->timeout);
        }
    }

    if (b == NULL) {
        return;
    }

    if (msg->buf == b) {
        /* Disable instant buffer completion/re-using by port. */
        msg->buf = NULL;
    }

    if (r->header_sent) {
        nxt_buf_chain_add(&r->out, b);
        nxt_http_request_send_body(task, r, NULL);

    } else {
        size_t b_size = nxt_buf_mem_used_size(&b->mem);

        if (nxt_slow_path(b_size < sizeof(*resp))) {
            goto fail;
        }

        resp = (void *) b->mem.pos;
        if (nxt_slow_path(b_size < sizeof(*resp)
              + resp->fields_count * sizeof(nxt_unit_field_t))) {
            goto fail;
        }

        field = NULL;

        for (f = resp->fields; f < resp->fields + resp->fields_count; f++) {
            if (f->skip) {
                continue;
            }

            field = nxt_list_add(r->resp.fields);

            if (nxt_slow_path(field == NULL)) {
                goto fail;
            }

            field->hash = f->hash;
            field->skip = 0;
            field->hopbyhop = 0;

            field->name_length = f->name_length;
            field->value_length = f->value_length;
            field->name = nxt_unit_sptr_get(&f->name);
            field->value = nxt_unit_sptr_get(&f->value);

            ret = nxt_http_field_process(field, &nxt_response_fields_hash, r);
            if (nxt_slow_path(ret != NXT_OK)) {
                goto fail;
            }

            nxt_debug(task, "header%s: %*s: %*s",
                      (field->skip ? " skipped" : ""),
                      (size_t) field->name_length, field->name,
                      (size_t) field->value_length, field->value);

            if (field->skip) {
                r->resp.fields->last->nelts--;
            }
        }

        r->status = resp->status;

        if (resp->piggyback_content_length != 0) {
            b->mem.pos = nxt_unit_sptr_get(&resp->piggyback_content);
            b->mem.free = b->mem.pos + resp->piggyback_content_length;

        } else {
            b->mem.pos = b->mem.free;
        }

        if (nxt_buf_mem_used_size(&b->mem) == 0) {
            next = b->next;
            b->next = NULL;

            nxt_work_queue_add(&task->thread->engine->fast_work_queue,
                               b->completion_handler, task, b, b->parent);

            b = next;
        }

        if (b != NULL) {
            nxt_buf_chain_add(&r->out, b);
        }

        nxt_http_request_header_send(task, r, nxt_http_request_send_body, NULL);

        if (r->websocket_handshake
            && r->status == NXT_HTTP_SWITCHING_PROTOCOLS)
        {
            req_app_link = nxt_request_app_link_alloc(task,
                                                     req_rpc_data->req_app_link,
                                                     req_rpc_data);
            if (nxt_slow_path(req_app_link == NULL)) {
                goto fail;
            }

            app_port = req_app_link->app_port;

            if (app_port == NULL && req_rpc_data->app_port != NULL) {
                req_app_link->app_port = req_rpc_data->app_port;
                app_port = req_app_link->app_port;
                req_app_link->apr_action = req_rpc_data->apr_action;

                req_rpc_data->app_port = NULL;
            }

            if (nxt_slow_path(app_port == NULL)) {
                goto fail;
            }

            nxt_thread_mutex_lock(&req_rpc_data->app->mutex);

            nxt_queue_insert_tail(&app_port->active_websockets,
                                  &req_app_link->link_port_websockets);

            nxt_thread_mutex_unlock(&req_rpc_data->app->mutex);

            nxt_router_app_port_release(task, app_port, NXT_APR_UPGRADE);
            req_app_link->apr_action = NXT_APR_CLOSE;

            nxt_debug(task, "req_app_link stream #%uD upgrade",
                      req_app_link->stream);

            r->state = &nxt_http_websocket;

        } else {
            r->state = &nxt_http_request_send_state;
        }
    }

    return;

fail:

    nxt_http_request_error(task, r, NXT_HTTP_SERVICE_UNAVAILABLE);

    nxt_request_rpc_data_unlink(task, req_rpc_data);
}


static const nxt_http_request_state_t  nxt_http_request_send_state
    nxt_aligned(64) =
{
    .error_handler = nxt_http_request_error_handler,
};


static void
nxt_http_request_send_body(nxt_task_t *task, void *obj, void *data)
{
    nxt_buf_t           *out;
    nxt_http_request_t  *r;

    r = obj;

    out = r->out;

    if (out != NULL) {
        r->out = NULL;
        nxt_http_request_send(task, r, out);
    }
}


static void
nxt_router_response_error_handler(nxt_task_t *task, nxt_port_recv_msg_t *msg,
    void *data)
{
    nxt_int_t               res;
    nxt_port_t              *port;
    nxt_bool_t              cancelled;
    nxt_request_app_link_t  *req_app_link;
    nxt_request_rpc_data_t  *req_rpc_data;

    req_rpc_data = data;

    req_app_link = req_rpc_data->req_app_link;

    if (req_app_link != NULL) {
        cancelled = nxt_router_msg_cancel(task, &req_app_link->msg_info,
                                          req_app_link->stream);
        if (cancelled) {
            res = nxt_router_app_port(task, req_rpc_data->app, req_app_link);

            if (res == NXT_OK) {
                port = req_app_link->app_port;

                if (nxt_slow_path(port == NULL)) {
                    nxt_log(task, NXT_LOG_ERR,
                            "port is NULL in cancelled req_app_link");
                    return;
                }

                nxt_port_rpc_ex_set_peer(task, task->thread->engine->port,
                                         req_rpc_data, port->pid);

                nxt_router_app_prepare_request(task, req_app_link);
            }

            msg->port_msg.last = 0;

            return;
        }
    }

    if (req_rpc_data->request != NULL) {
        nxt_http_request_error(task, req_rpc_data->request,
                               NXT_HTTP_SERVICE_UNAVAILABLE);
    }

    nxt_request_rpc_data_unlink(task, req_rpc_data);
}


static void
nxt_router_app_port_ready(nxt_task_t *task, nxt_port_recv_msg_t *msg,
    void *data)
{
    nxt_app_t        *app;
    nxt_port_t       *port;
    nxt_app_joint_t  *app_joint;

    app_joint = data;
    port = msg->u.new_port;

    nxt_assert(app_joint != NULL);
    nxt_assert(port != NULL);

    app = app_joint->app;

    nxt_router_app_joint_use(task, app_joint, -1);

    if (nxt_slow_path(app == NULL)) {
        nxt_debug(task, "new port ready for released app, send QUIT");

        nxt_port_socket_write(task, port, NXT_PORT_MSG_QUIT, -1, 0, 0, NULL);

        return;
    }

    port->app = app;

    nxt_thread_mutex_lock(&app->mutex);

    nxt_assert(app->pending_processes != 0);

    app->pending_processes--;
    app->processes++;

    nxt_thread_mutex_unlock(&app->mutex);

    nxt_debug(task, "app '%V' new port ready, pid %PI, %d/%d",
              &app->name, port->pid, app->processes, app->pending_processes);

    nxt_router_app_port_release(task, port, NXT_APR_NEW_PORT);
}


static void
nxt_router_app_port_error(nxt_task_t *task, nxt_port_recv_msg_t *msg,
    void *data)
{
    nxt_app_t               *app;
    nxt_app_joint_t         *app_joint;
    nxt_queue_link_t        *lnk;
    nxt_request_app_link_t  *req_app_link;

    app_joint = data;

    nxt_assert(app_joint != NULL);

    app = app_joint->app;

    nxt_router_app_joint_use(task, app_joint, -1);

    if (nxt_slow_path(app == NULL)) {
        nxt_debug(task, "start error for released app");

        return;
    }

    nxt_debug(task, "app '%V' %p start error", &app->name, app);

    nxt_thread_mutex_lock(&app->mutex);

    nxt_assert(app->pending_processes != 0);

    app->pending_processes--;

    if (!nxt_queue_is_empty(&app->requests)) {
        lnk = nxt_queue_last(&app->requests);
        nxt_queue_remove(lnk);
        lnk->next = NULL;

        req_app_link = nxt_queue_link_data(lnk, nxt_request_app_link_t,
                                           link_app_requests);

    } else {
        req_app_link = NULL;
    }

    nxt_thread_mutex_unlock(&app->mutex);

    if (req_app_link != NULL) {
        nxt_debug(task, "app '%V' %p abort next stream #%uD",
                  &app->name, app, req_app_link->stream);

        nxt_request_app_link_error(task, app, req_app_link,
                                   "Failed to start application process");
        nxt_request_app_link_use(task, req_app_link, -1);
    }
}

nxt_inline nxt_port_t *
nxt_router_app_get_port_for_quit(nxt_app_t *app);

void
nxt_router_app_use(nxt_task_t *task, nxt_app_t *app, int i)
{
    int  c;

    c = nxt_atomic_fetch_add(&app->use_count, i);

    if (i < 0 && c == -i) {

        if (task->thread->engine != app->engine) {
            nxt_event_engine_post(app->engine, &app->joint->free_app_work);

        } else {
            nxt_router_free_app(task, app->joint, NULL);
        }
    }
}


nxt_inline nxt_bool_t
nxt_router_app_first_port_busy(nxt_app_t *app)
{
    nxt_port_t        *port;
    nxt_queue_link_t  *lnk;

    lnk = nxt_queue_first(&app->ports);
    port = nxt_queue_link_data(lnk, nxt_port_t, app_link);

    return port->app_pending_responses > 0;
}


nxt_inline nxt_port_t *
nxt_router_pop_first_port(nxt_app_t *app)
{
    nxt_port_t        *port;
    nxt_queue_link_t  *lnk;

    lnk = nxt_queue_first(&app->ports);
    nxt_queue_remove(lnk);

    port = nxt_queue_link_data(lnk, nxt_port_t, app_link);

    port->app_pending_responses++;

    if (nxt_queue_chk_remove(&port->idle_link)) {
        app->idle_processes--;

        if (port->idle_start == 0) {
            nxt_assert(app->idle_processes < app->spare_processes);

        } else {
            nxt_assert(app->idle_processes >= app->spare_processes);

            port->idle_start = 0;
        }
    }

    if ((app->max_pending_responses == 0
            || port->app_pending_responses < app->max_pending_responses)
        && (app->max_requests == 0
            || port->app_responses + port->app_pending_responses
                < app->max_requests))
    {
        nxt_queue_insert_tail(&app->ports, lnk);

        nxt_port_inc_use(port);

    } else {
        lnk->next = NULL;
    }

    return port;
}


nxt_inline nxt_port_t *
nxt_router_app_get_port_for_quit(nxt_app_t *app)
{
    nxt_port_t  *port;

    port = NULL;

    nxt_thread_mutex_lock(&app->mutex);

    nxt_queue_each(port, &app->ports, nxt_port_t, app_link) {

        if (port->app_pending_responses > 0) {
            port = NULL;

            continue;
        }

        /* Caller is responsible to decrease port use count. */
        nxt_queue_chk_remove(&port->app_link);

        if (nxt_queue_chk_remove(&port->idle_link)) {
            app->idle_processes--;
        }

        port->app = NULL;
        app->processes--;

        break;

    } nxt_queue_loop;

    nxt_thread_mutex_unlock(&app->mutex);

    return port;
}


static void
nxt_router_app_unlink(nxt_task_t *task, nxt_app_t *app)
{
    nxt_debug(task, "app '%V' %p unlink", &app->name, app);

    nxt_queue_remove(&app->link);

    nxt_router_app_use(task, app, -1);
}


static void
nxt_router_app_process_request(nxt_task_t *task, void *obj, void *data)
{
    nxt_request_app_link_t  *req_app_link;

    req_app_link = data;

#if (NXT_DEBUG)
    {
    nxt_app_t  *app;

    app = obj;

    nxt_assert(app != NULL);
    nxt_assert(req_app_link != NULL);
    nxt_assert(req_app_link->app_port != NULL);

    nxt_debug(task, "app '%V' %p process next stream #%uD",
              &app->name, app, req_app_link->stream);
    }
#endif

    nxt_router_app_prepare_request(task, req_app_link);

    nxt_request_app_link_use(task, req_app_link, -1);
}


static void
nxt_router_app_port_release(nxt_task_t *task, nxt_port_t *port,
    nxt_apr_action_t action)
{
    int                      inc_use;
    uint32_t                 dec_pending, got_response;
    nxt_app_t                *app;
    nxt_bool_t               port_unchained;
    nxt_bool_t               send_quit, cancelled, adjust_idle_timer;
    nxt_queue_link_t         *lnk;
    nxt_request_app_link_t   *req_app_link, *pending_ra, *re_ra;
    nxt_port_select_state_t  state;

    nxt_assert(port != NULL);
    nxt_assert(port->app != NULL);

    req_app_link = NULL;

    app = port->app;

    inc_use = 0;
    dec_pending = 0;
    got_response = 0;

    switch (action) {
    case NXT_APR_NEW_PORT:
        break;
    case NXT_APR_REQUEST_FAILED:
        dec_pending = 1;
        inc_use = -1;
        break;
    case NXT_APR_GOT_RESPONSE:
        dec_pending = 1;
        got_response = 1;
        inc_use = -1;
        break;
    case NXT_APR_UPGRADE:
        dec_pending = 1;
        got_response = 1;
        break;
    case NXT_APR_CLOSE:
        inc_use = -1;
        break;
    }

    nxt_thread_mutex_lock(&app->mutex);

    port->app_pending_responses -= dec_pending;
    port->app_responses += got_response;

    if (port->pair[1] != -1
        && (app->max_pending_responses == 0
            || port->app_pending_responses < app->max_pending_responses)
        && (app->max_requests == 0
            || port->app_responses + port->app_pending_responses
                < app->max_requests))
    {
        if (port->app_link.next == NULL) {
            if (port->app_pending_responses > 0) {
                nxt_queue_insert_tail(&app->ports, &port->app_link);

            } else {
                nxt_queue_insert_head(&app->ports, &port->app_link);
            }

            nxt_port_inc_use(port);

        } else {
            if (port->app_pending_responses == 0
                && nxt_queue_first(&app->ports) != &port->app_link)
            {
                nxt_queue_remove(&port->app_link);
                nxt_queue_insert_head(&app->ports, &port->app_link);
            }
        }
    }

    if (!nxt_queue_is_empty(&app->ports)
        && !nxt_queue_is_empty(&app->requests))
    {
        lnk = nxt_queue_first(&app->requests);
        nxt_queue_remove(lnk);
        lnk->next = NULL;

        req_app_link = nxt_queue_link_data(lnk, nxt_request_app_link_t,
                                           link_app_requests);

        req_app_link->app_port = nxt_router_pop_first_port(app);

        if (req_app_link->app_port->app_pending_responses > 1) {
            nxt_request_app_link_pending(task, app, req_app_link);
        }
    }

    /* Pop first pending request for this port. */
    if (dec_pending > 0
        && !nxt_queue_is_empty(&port->pending_requests))
    {
        lnk = nxt_queue_first(&port->pending_requests);
        nxt_queue_remove(lnk);
        lnk->next = NULL;

        pending_ra = nxt_queue_link_data(lnk, nxt_request_app_link_t,
                                         link_port_pending);

        nxt_assert(pending_ra->link_app_pending.next != NULL);

        nxt_queue_remove(&pending_ra->link_app_pending);
        pending_ra->link_app_pending.next = NULL;

    } else {
        pending_ra = NULL;
    }

    /* Try to cancel and re-schedule first stalled request for this app. */
    if (got_response > 0 && !nxt_queue_is_empty(&app->pending)) {
        lnk = nxt_queue_first(&app->pending);

        re_ra = nxt_queue_link_data(lnk, nxt_request_app_link_t,
                                    link_app_pending);

        if (re_ra->res_time <= nxt_thread_monotonic_time(task->thread)) {

            nxt_debug(task, "app '%V' stalled request #%uD detected",
                      &app->name, re_ra->stream);

            cancelled = nxt_router_msg_cancel(task, &re_ra->msg_info,
                                              re_ra->stream);

            if (cancelled) {
                state.req_app_link = re_ra;
                state.app = app;

                /*
                 * Need to increment use count "in advance" because
                 * nxt_router_port_select() will remove re_ra from lists
                 * and decrement use count.
                 */
                nxt_request_app_link_inc_use(re_ra);

                nxt_router_port_select(task, &state);

                goto re_ra_cancelled;
            }
        }
    }

    re_ra = NULL;

re_ra_cancelled:

    send_quit = (app->max_requests > 0
                 && port->app_pending_responses == 0
                 && port->app_responses >= app->max_requests);

    if (send_quit) {
        port_unchained = nxt_queue_chk_remove(&port->app_link);

        port->app = NULL;
        app->processes--;

    } else {
        port_unchained = 0;
    }

    adjust_idle_timer = 0;

    if (port->pair[1] != -1 && !send_quit && port->app_pending_responses == 0
        && nxt_queue_is_empty(&port->active_websockets)
        && port->idle_link.next == NULL)
    {
        if (app->idle_processes == app->spare_processes
            && app->adjust_idle_work.data == NULL)
        {
            adjust_idle_timer = 1;
            app->adjust_idle_work.data = app;
            app->adjust_idle_work.next = NULL;
        }

        if (app->idle_processes < app->spare_processes) {
            nxt_queue_insert_tail(&app->spare_ports, &port->idle_link);

        } else {
            nxt_queue_insert_tail(&app->idle_ports, &port->idle_link);

            port->idle_start = task->thread->engine->timers.now;
        }

        app->idle_processes++;
    }

    nxt_thread_mutex_unlock(&app->mutex);

    if (adjust_idle_timer) {
        nxt_router_app_use(task, app, 1);
        nxt_event_engine_post(app->engine, &app->adjust_idle_work);
    }

    if (pending_ra != NULL) {
        nxt_request_app_link_use(task, pending_ra, -1);
    }

    if (re_ra != NULL) {
        if (nxt_router_port_post_select(task, &state) == NXT_OK) {
            /*
             * Reference counter already incremented above, this will
             * keep re_ra while nxt_router_app_process_request()
             * task is in queue.  Reference counter decreased in
             * nxt_router_app_process_request() after processing.
             */

            nxt_work_queue_add(&task->thread->engine->fast_work_queue,
                               nxt_router_app_process_request,
                               &task->thread->engine->task, app, re_ra);

        } else {
            nxt_request_app_link_use(task, re_ra, -1);
        }
    }

    if (req_app_link != NULL) {
        /*
         * There should be call nxt_request_app_link_inc_use(req_app_link),
         * because of one more link in the queue.  But one link was
         * recently removed from app->requests linked list.
         * Corresponding decrement is in nxt_router_app_process_request().
         */

        nxt_work_queue_add(&task->thread->engine->fast_work_queue,
                           nxt_router_app_process_request,
                           &task->thread->engine->task, app, req_app_link);

        goto adjust_use;
    }

    /* ? */
    if (port->pair[1] == -1) {
        nxt_debug(task, "app '%V' %p port %p already closed (pid %PI dead?)",
                  &app->name, app, port, port->pid);

        goto adjust_use;
    }

    if (send_quit) {
        nxt_debug(task, "app '%V' %p send QUIT to port",
                  &app->name, app);

        nxt_port_socket_write(task, port, NXT_PORT_MSG_QUIT,
                              -1, 0, 0, NULL);

        if (port_unchained) {
            nxt_port_use(task, port, -1);
        }

        goto adjust_use;
    }

    nxt_debug(task, "app '%V' %p requests queue is empty, keep the port",
              &app->name, app);

adjust_use:

    nxt_port_use(task, port, inc_use);
}


void
nxt_router_app_port_close(nxt_task_t *task, nxt_port_t *port)
{
    nxt_app_t         *app;
    nxt_bool_t        unchain, start_process;
    nxt_port_t        *idle_port;
    nxt_queue_link_t  *idle_lnk;

    app = port->app;

    nxt_assert(app != NULL);

    nxt_thread_mutex_lock(&app->mutex);

    unchain = nxt_queue_chk_remove(&port->app_link);

    if (nxt_queue_chk_remove(&port->idle_link)) {
        app->idle_processes--;

        if (port->idle_start == 0
            && app->idle_processes >= app->spare_processes)
        {
            nxt_assert(!nxt_queue_is_empty(&app->idle_ports));

            idle_lnk = nxt_queue_last(&app->idle_ports);
            idle_port = nxt_queue_link_data(idle_lnk, nxt_port_t, idle_link);
            nxt_queue_remove(idle_lnk);

            nxt_queue_insert_tail(&app->spare_ports, idle_lnk);

            idle_port->idle_start = 0;
        }
    }

    app->processes--;

    start_process = !task->thread->engine->shutdown
                    && nxt_router_app_can_start(app)
                    && (!nxt_queue_is_empty(&app->requests)
                        || nxt_router_app_need_start(app));

    if (start_process) {
        app->pending_processes++;
    }

    nxt_thread_mutex_unlock(&app->mutex);

    nxt_debug(task, "app '%V' pid %PI closed", &app->name, port->pid);

    if (unchain) {
        nxt_port_use(task, port, -1);
    }

    if (start_process) {
        nxt_router_start_app_process(task, app);
    }
}


static void
nxt_router_adjust_idle_timer(nxt_task_t *task, void *obj, void *data)
{
    nxt_app_t           *app;
    nxt_bool_t          queued;
    nxt_port_t          *port;
    nxt_msec_t          timeout, threshold;
    nxt_queue_link_t    *lnk;
    nxt_event_engine_t  *engine;

    app = obj;
    queued = (data == app);

    nxt_debug(task, "nxt_router_adjust_idle_timer: app \"%V\", queued %b",
              &app->name, queued);

    engine = task->thread->engine;

    nxt_assert(app->engine == engine);

    threshold = engine->timers.now + app->joint->idle_timer.bias;
    timeout = 0;

    nxt_thread_mutex_lock(&app->mutex);

    if (queued) {
        app->adjust_idle_work.data = NULL;
    }

    while (app->idle_processes > app->spare_processes) {

        nxt_assert(!nxt_queue_is_empty(&app->idle_ports));

        lnk = nxt_queue_first(&app->idle_ports);
        port = nxt_queue_link_data(lnk, nxt_port_t, idle_link);

        timeout = port->idle_start + app->idle_timeout;

        if (timeout > threshold) {
            break;
        }

        nxt_queue_remove(lnk);
        lnk->next = NULL;

        nxt_queue_chk_remove(&port->app_link);

        app->idle_processes--;
        app->processes--;
        port->app = NULL;

        nxt_thread_mutex_unlock(&app->mutex);

        nxt_debug(task, "app '%V' send QUIT to idle port %PI",
                  &app->name, port->pid);

        nxt_port_socket_write(task, port, NXT_PORT_MSG_QUIT, -1, 0, 0, NULL);

        nxt_port_use(task, port, -1);

        nxt_thread_mutex_lock(&app->mutex);
    }

    nxt_thread_mutex_unlock(&app->mutex);

    if (timeout > threshold) {
        nxt_timer_add(engine, &app->joint->idle_timer, timeout - threshold);

    } else {
        nxt_timer_disable(engine, &app->joint->idle_timer);
    }

    if (queued) {
        nxt_router_app_use(task, app, -1);
    }
}


static void
nxt_router_app_idle_timeout(nxt_task_t *task, void *obj, void *data)
{
    nxt_timer_t      *timer;
    nxt_app_joint_t  *app_joint;

    timer = obj;
    app_joint = nxt_container_of(timer, nxt_app_joint_t, idle_timer);

    if (nxt_fast_path(app_joint->app != NULL)) {
        nxt_router_adjust_idle_timer(task, app_joint->app, NULL);
    }
}


static void
nxt_router_app_joint_release_handler(nxt_task_t *task, void *obj, void *data)
{
    nxt_timer_t      *timer;
    nxt_app_joint_t  *app_joint;

    timer = obj;
    app_joint = nxt_container_of(timer, nxt_app_joint_t, idle_timer);

    nxt_router_app_joint_use(task, app_joint, -1);
}


static void
nxt_router_free_app(nxt_task_t *task, void *obj, void *data)
{
    nxt_app_t        *app;
    nxt_port_t       *port;
    nxt_app_joint_t  *app_joint;

    app_joint = obj;
    app = app_joint->app;

    for ( ;; ) {
        port = nxt_router_app_get_port_for_quit(app);
        if (port == NULL) {
            break;
        }

        nxt_debug(task, "send QUIT to app '%V' pid %PI", &app->name, port->pid);

        nxt_port_socket_write(task, port, NXT_PORT_MSG_QUIT, -1, 0, 0, NULL);

        nxt_port_use(task, port, -1);
    }

    nxt_assert(app->processes == 0);
    nxt_assert(app->idle_processes == 0);
    nxt_assert(nxt_queue_is_empty(&app->requests));
    nxt_assert(nxt_queue_is_empty(&app->ports));
    nxt_assert(nxt_queue_is_empty(&app->spare_ports));
    nxt_assert(nxt_queue_is_empty(&app->idle_ports));

    nxt_thread_mutex_destroy(&app->mutex);
    nxt_mp_destroy(app->mem_pool);

    app_joint->app = NULL;

    if (nxt_timer_delete(task->thread->engine, &app_joint->idle_timer)) {
        app_joint->idle_timer.handler = nxt_router_app_joint_release_handler;
        nxt_timer_add(task->thread->engine, &app_joint->idle_timer, 0);

    } else {
        nxt_router_app_joint_use(task, app_joint, -1);
    }
}


static void
nxt_router_port_select(nxt_task_t *task, nxt_port_select_state_t *state)
{
    int                     ra_use_delta;
    nxt_app_t               *app;
    nxt_bool_t              can_start_process;
    nxt_request_app_link_t  *req_app_link;

    req_app_link = state->req_app_link;
    app = state->app;

    state->failed_port_use_delta = 0;
    ra_use_delta = -nxt_queue_chk_remove(&req_app_link->link_app_requests);

    if (nxt_queue_chk_remove(&req_app_link->link_port_pending))
    {
        nxt_assert(req_app_link->link_app_pending.next != NULL);

        nxt_queue_remove(&req_app_link->link_app_pending);
        req_app_link->link_app_pending.next = NULL;

        ra_use_delta--;
    }

    state->failed_port = req_app_link->app_port;

    if (req_app_link->app_port != NULL) {
        state->failed_port_use_delta--;

        state->failed_port->app_pending_responses--;

        if (nxt_queue_chk_remove(&state->failed_port->app_link)) {
            state->failed_port_use_delta--;
        }

        req_app_link->app_port = NULL;
    }

    can_start_process = nxt_router_app_can_start(app);

    state->port = NULL;
    state->start_process = 0;

    if (nxt_queue_is_empty(&app->ports)
        || (can_start_process && nxt_router_app_first_port_busy(app)) )
    {
        req_app_link = nxt_request_app_link_alloc(task, req_app_link,
                                                  req_app_link->req_rpc_data);
        if (nxt_slow_path(req_app_link == NULL)) {
            goto fail;
        }

        if (nxt_slow_path(state->failed_port != NULL)) {
            nxt_queue_insert_head(&app->requests,
                                  &req_app_link->link_app_requests);

        } else {
            nxt_queue_insert_tail(&app->requests,
                                  &req_app_link->link_app_requests);
        }

        nxt_request_app_link_inc_use(req_app_link);

        nxt_debug(task, "req_app_link stream #%uD enqueue to app->requests",
                  req_app_link->stream);

        if (can_start_process) {
            app->pending_processes++;
            state->start_process = 1;
        }

    } else {
        state->port = nxt_router_pop_first_port(app);

        if (state->port->app_pending_responses > 1) {
            req_app_link = nxt_request_app_link_alloc(task, req_app_link,
                                                    req_app_link->req_rpc_data);
            if (nxt_slow_path(req_app_link == NULL)) {
                goto fail;
            }

            req_app_link->app_port = state->port;

            nxt_request_app_link_pending(task, app, req_app_link);
        }

        if (can_start_process && nxt_router_app_need_start(app)) {
            app->pending_processes++;
            state->start_process = 1;
        }
    }

    nxt_request_app_link_chk_use(req_app_link, ra_use_delta);

fail:

    state->shared_ra = req_app_link;
}


static nxt_int_t
nxt_router_port_post_select(nxt_task_t *task, nxt_port_select_state_t *state)
{
    nxt_int_t               res;
    nxt_app_t               *app;
    nxt_request_app_link_t  *req_app_link;

    req_app_link = state->shared_ra;
    app = state->app;

    if (state->failed_port_use_delta != 0) {
        nxt_port_use(task, state->failed_port, state->failed_port_use_delta);
    }

    if (nxt_slow_path(req_app_link == NULL)) {
        if (state->port != NULL) {
            nxt_port_use(task, state->port, -1);
        }

        nxt_request_app_link_error(task, app, state->req_app_link,
                            "Failed to allocate shared req<->app link");

        return NXT_ERROR;
    }

    if (state->port != NULL) {
        nxt_debug(task, "already have port for app '%V' %p ", &app->name, app);

        req_app_link->app_port = state->port;

        if (state->start_process) {
            nxt_router_start_app_process(task, app);
        }

        return NXT_OK;
    }

    if (!state->start_process) {
        nxt_debug(task, "app '%V' %p too many running or pending processes",
                  &app->name, app);

        return NXT_AGAIN;
    }

    res = nxt_router_start_app_process(task, app);

    if (nxt_slow_path(res != NXT_OK)) {
        nxt_request_app_link_error(task, app, req_app_link,
                                   "Failed to start app process");

        return NXT_ERROR;
    }

    return NXT_AGAIN;
}


static nxt_int_t
nxt_router_app_port(nxt_task_t *task, nxt_app_t *app,
    nxt_request_app_link_t *req_app_link)
{
    nxt_port_select_state_t  state;

    state.req_app_link = req_app_link;
    state.app = app;

    nxt_thread_mutex_lock(&app->mutex);

    nxt_router_port_select(task, &state);

    nxt_thread_mutex_unlock(&app->mutex);

    return nxt_router_port_post_select(task, &state);
}


void
nxt_router_process_http_request(nxt_task_t *task, nxt_http_request_t *r,
    nxt_app_t *app)
{
    nxt_int_t               res;
    nxt_port_t              *port;
    nxt_event_engine_t      *engine;
    nxt_request_app_link_t  ra_local, *req_app_link;
    nxt_request_rpc_data_t  *req_rpc_data;

    engine = task->thread->engine;

    req_rpc_data = nxt_port_rpc_register_handler_ex(task, engine->port,
                                          nxt_router_response_ready_handler,
                                          nxt_router_response_error_handler,
                                          sizeof(nxt_request_rpc_data_t));
    if (nxt_slow_path(req_rpc_data == NULL)) {
        nxt_http_request_error(task, r, NXT_HTTP_INTERNAL_SERVER_ERROR);
        return;
    }

    /*
     * At this point we have request req_rpc_data allocated and registered
     * in port handlers.  Need to fixup request memory pool.  Counterpart
     * release will be called via following call chain:
     *    nxt_request_rpc_data_unlink() ->
     *        nxt_router_http_request_done() ->
     *            nxt_router_http_request_release()
     */
    nxt_mp_retain(r->mem_pool);

    r->timer.task = &engine->task;
    r->timer.work_queue = &engine->fast_work_queue;
    r->timer.log = engine->task.log;
    r->timer.bias = NXT_TIMER_DEFAULT_BIAS;

    req_rpc_data->stream = nxt_port_rpc_ex_stream(req_rpc_data);
    req_rpc_data->app = app;

    nxt_router_app_use(task, app, 1);

    req_rpc_data->request = r;
    r->req_rpc_data = req_rpc_data;

    req_app_link = &ra_local;
    nxt_request_app_link_init(task, req_app_link, req_rpc_data);

    res = nxt_router_app_port(task, app, req_app_link);
    req_app_link = req_rpc_data->req_app_link;

    if (res == NXT_OK) {
        port = req_app_link->app_port;

        nxt_assert(port != NULL);

        nxt_port_rpc_ex_set_peer(task, engine->port, req_rpc_data, port->pid);

        nxt_router_app_prepare_request(task, req_app_link);
    }

    nxt_request_app_link_use(task, req_app_link, -1);
}


static void
nxt_router_dummy_buf_completion(nxt_task_t *task, void *obj, void *data)
{
}


static void
nxt_router_app_prepare_request(nxt_task_t *task,
    nxt_request_app_link_t *req_app_link)
{
    nxt_buf_t         *buf;
    nxt_int_t         res;
    nxt_port_t        *port, *c_port, *reply_port;
    nxt_apr_action_t  apr_action;

    nxt_assert(req_app_link->app_port != NULL);

    port = req_app_link->app_port;
    reply_port = req_app_link->reply_port;

    apr_action = NXT_APR_REQUEST_FAILED;

    c_port = nxt_process_connected_port_find(port->process, reply_port);

    if (nxt_slow_path(c_port != reply_port)) {
        res = nxt_port_send_port(task, port, reply_port, 0);

        if (nxt_slow_path(res != NXT_OK)) {
            nxt_request_app_link_error(task, port->app, req_app_link,
                                "Failed to send reply port to application");

            goto release_port;
        }

        nxt_process_connected_port_add(port->process, reply_port);
    }

    buf = nxt_router_prepare_msg(task, req_app_link->request, port,
                                 nxt_app_msg_prefix[port->app->type]);

    if (nxt_slow_path(buf == NULL)) {
        nxt_request_app_link_error(task, port->app, req_app_link,
                            "Failed to prepare message for application");
        goto release_port;
    }

    nxt_debug(task, "about to send %O bytes buffer to app process port %d",
                    nxt_buf_used_size(buf),
                    port->socket.fd);

    apr_action = NXT_APR_NEW_PORT;

    req_app_link->msg_info.buf = buf;
    req_app_link->msg_info.completion_handler = buf->completion_handler;

    for (; buf; buf = buf->next) {
        buf->completion_handler = nxt_router_dummy_buf_completion;
    }

    buf = req_app_link->msg_info.buf;

    res = nxt_port_mmap_get_tracking(task, port,
                                     &req_app_link->msg_info.tracking,
                                     req_app_link->stream);
    if (nxt_slow_path(res != NXT_OK)) {
        nxt_request_app_link_error(task, port->app, req_app_link,
                                   "Failed to get tracking area");
        goto release_port;
    }

    if (req_app_link->body_fd != -1) {
        nxt_debug(task, "stream #%uD: send body fd %d", req_app_link->stream,
                  req_app_link->body_fd);

        lseek(req_app_link->body_fd, 0, SEEK_SET);
    }

    res = nxt_port_socket_twrite(task, port, NXT_PORT_MSG_REQ_HEADERS,
                                 req_app_link->body_fd,
                                 req_app_link->stream, reply_port->id, buf,
                                 &req_app_link->msg_info.tracking);

    if (nxt_slow_path(res != NXT_OK)) {
        nxt_request_app_link_error(task, port->app, req_app_link,
                                   "Failed to send message to application");
        goto release_port;
    }

release_port:

    nxt_router_app_port_release(task, port, apr_action);

    nxt_request_app_link_update_peer(task, req_app_link);
}


struct nxt_fields_iter_s {
    nxt_list_part_t   *part;
    nxt_http_field_t  *field;
};

typedef struct nxt_fields_iter_s  nxt_fields_iter_t;


static nxt_http_field_t *
nxt_fields_part_first(nxt_list_part_t *part, nxt_fields_iter_t *i)
{
    if (part == NULL) {
        return NULL;
    }

    while (part->nelts == 0) {
        part = part->next;
        if (part == NULL) {
            return NULL;
        }
    }

    i->part = part;
    i->field = nxt_list_data(i->part);

    return i->field;
}


static nxt_http_field_t *
nxt_fields_first(nxt_list_t *fields, nxt_fields_iter_t *i)
{
    return nxt_fields_part_first(nxt_list_part(fields), i);
}


static nxt_http_field_t *
nxt_fields_next(nxt_fields_iter_t *i)
{
    nxt_http_field_t  *end = nxt_list_data(i->part);

    end += i->part->nelts;
    i->field++;

    if (i->field < end) {
        return i->field;
    }

    return nxt_fields_part_first(i->part->next, i);
}


static nxt_buf_t *
nxt_router_prepare_msg(nxt_task_t *task, nxt_http_request_t *r,
    nxt_port_t *port, const nxt_str_t *prefix)
{
    void                *target_pos, *query_pos;
    u_char              *pos, *end, *p, c;
    size_t              fields_count, req_size, size, free_size;
    size_t              copy_size;
    nxt_off_t           content_length;
    nxt_buf_t           *b, *buf, *out, **tail;
    nxt_http_field_t    *field, *dup;
    nxt_unit_field_t    *dst_field;
    nxt_fields_iter_t   iter, dup_iter;
    nxt_unit_request_t  *req;

    req_size = sizeof(nxt_unit_request_t)
               + r->method->length + 1
               + r->version.length + 1
               + r->remote->length + 1
               + r->local->length + 1
               + r->server_name.length + 1
               + r->target.length + 1
               + (r->path->start != r->target.start ? r->path->length + 1 : 0);

    content_length = r->content_length_n < 0 ? 0 : r->content_length_n;
    fields_count = 0;

    nxt_list_each(field, r->fields) {
        fields_count++;

        req_size += field->name_length + prefix->length + 1
                    + field->value_length + 1;
    } nxt_list_loop;

    req_size += fields_count * sizeof(nxt_unit_field_t);

    if (nxt_slow_path(req_size > PORT_MMAP_DATA_SIZE)) {
        nxt_alert(task, "headers to big to fit in shared memory (%d)",
                  (int) req_size);

        return NULL;
    }

    out = nxt_port_mmap_get_buf(task, port,
              nxt_min(req_size + content_length, PORT_MMAP_DATA_SIZE));
    if (nxt_slow_path(out == NULL)) {
        return NULL;
    }

    req = (nxt_unit_request_t *) out->mem.free;
    out->mem.free += req_size;

    req->app_target = r->app_target;

    req->content_length = content_length;

    p = (u_char *) (req->fields + fields_count);

    nxt_debug(task, "fields_count=%d", (int) fields_count);

    req->method_length = r->method->length;
    nxt_unit_sptr_set(&req->method, p);
    p = nxt_cpymem(p, r->method->start, r->method->length);
    *p++ = '\0';

    req->version_length = r->version.length;
    nxt_unit_sptr_set(&req->version, p);
    p = nxt_cpymem(p, r->version.start, r->version.length);
    *p++ = '\0';

    req->remote_length = r->remote->address_length;
    nxt_unit_sptr_set(&req->remote, p);
    p = nxt_cpymem(p, nxt_sockaddr_address(r->remote),
                   r->remote->address_length);
    *p++ = '\0';

    req->local_length = r->local->address_length;
    nxt_unit_sptr_set(&req->local, p);
    p = nxt_cpymem(p, nxt_sockaddr_address(r->local), r->local->address_length);
    *p++ = '\0';

    req->tls = (r->tls != NULL);
    req->websocket_handshake = r->websocket_handshake;

    req->server_name_length = r->server_name.length;
    nxt_unit_sptr_set(&req->server_name, p);
    p = nxt_cpymem(p, r->server_name.start, r->server_name.length);
    *p++ = '\0';

    target_pos = p;
    req->target_length = (uint32_t) r->target.length;
    nxt_unit_sptr_set(&req->target, p);
    p = nxt_cpymem(p, r->target.start, r->target.length);
    *p++ = '\0';

    req->path_length = (uint32_t) r->path->length;
    if (r->path->start == r->target.start) {
        nxt_unit_sptr_set(&req->path, target_pos);

    } else {
        nxt_unit_sptr_set(&req->path, p);
        p = nxt_cpymem(p, r->path->start, r->path->length);
        *p++ = '\0';
    }

    req->query_length = r->args != NULL ? (uint32_t) r->args->length : 0;
    if (r->args != NULL && r->args->start != NULL) {
        query_pos = nxt_pointer_to(target_pos,
                                   r->args->start - r->target.start);

        nxt_unit_sptr_set(&req->query, query_pos);

    } else {
        req->query.offset = 0;
    }

    req->content_length_field = NXT_UNIT_NONE_FIELD;
    req->content_type_field   = NXT_UNIT_NONE_FIELD;
    req->cookie_field         = NXT_UNIT_NONE_FIELD;

    dst_field = req->fields;

    for (field = nxt_fields_first(r->fields, &iter);
         field != NULL;
         field = nxt_fields_next(&iter))
    {
        if (field->skip) {
            continue;
        }

        dst_field->hash = field->hash;
        dst_field->skip = 0;
        dst_field->name_length = field->name_length + prefix->length;
        dst_field->value_length = field->value_length;

        if (field == r->content_length) {
            req->content_length_field = dst_field - req->fields;

        } else if (field == r->content_type) {
            req->content_type_field = dst_field - req->fields;

        } else if (field == r->cookie) {
            req->cookie_field = dst_field - req->fields;
        }

        nxt_debug(task, "add field 0x%04Xd, %d, %d, %p : %d %p",
                  (int) field->hash, (int) field->skip,
                  (int) field->name_length, field->name,
                  (int) field->value_length, field->value);

        if (prefix->length != 0) {
            nxt_unit_sptr_set(&dst_field->name, p);
            p = nxt_cpymem(p, prefix->start, prefix->length);

            end = field->name + field->name_length;
            for (pos = field->name; pos < end; pos++) {
                c = *pos;

                if (c >= 'a' && c <= 'z') {
                    *p++ = (c & ~0x20);
                    continue;
                }

                if (c == '-') {
                    *p++ = '_';
                    continue;
                }

                *p++ = c;
            }

        } else {
            nxt_unit_sptr_set(&dst_field->name, p);
            p = nxt_cpymem(p, field->name, field->name_length);
        }

        *p++ = '\0';

        nxt_unit_sptr_set(&dst_field->value, p);
        p = nxt_cpymem(p, field->value, field->value_length);

        if (prefix->length != 0) {
            dup_iter = iter;

            for (dup = nxt_fields_next(&dup_iter);
                 dup != NULL;
                 dup = nxt_fields_next(&dup_iter))
            {
                if (dup->name_length != field->name_length
                    || dup->skip
                    || dup->hash != field->hash
                    || nxt_memcasecmp(dup->name, field->name, dup->name_length))
                {
                    continue;
                }

                p = nxt_cpymem(p, ", ", 2);
                p = nxt_cpymem(p, dup->value, dup->value_length);

                dst_field->value_length += 2 + dup->value_length;

                dup->skip = 1;
            }
        }

        *p++ = '\0';

        dst_field++;
    }

    req->fields_count = (uint32_t) (dst_field - req->fields);

    nxt_unit_sptr_set(&req->preread_content, out->mem.free);

    buf = out;
    tail = &buf->next;

    for (b = r->body; b != NULL; b = b->next) {
        size = nxt_buf_mem_used_size(&b->mem);
        pos = b->mem.pos;

        while (size > 0) {
            if (buf == NULL) {
                free_size = nxt_min(size, PORT_MMAP_DATA_SIZE);

                buf = nxt_port_mmap_get_buf(task, port, free_size);
                if (nxt_slow_path(buf == NULL)) {
                    while (out != NULL) {
                        buf = out->next;
                        out->next = NULL;
                        out->completion_handler(task, out, out->parent);
                        out = buf;
                    }
                    return NULL;
                }

                *tail = buf;
                tail = &buf->next;

            } else {
                free_size = nxt_buf_mem_free_size(&buf->mem);
                if (free_size < size
                    && nxt_port_mmap_increase_buf(task, buf, size, 1)
                       == NXT_OK)
                {
                    free_size = nxt_buf_mem_free_size(&buf->mem);
                }
            }

            if (free_size > 0) {
                copy_size = nxt_min(free_size, size);

                buf->mem.free = nxt_cpymem(buf->mem.free, pos, copy_size);

                size -= copy_size;
                pos += copy_size;

                if (size == 0) {
                    break;
                }
            }

            buf = NULL;
        }
    }

    return out;
}


static void
nxt_router_app_timeout(nxt_task_t *task, void *obj, void *data)
{
    nxt_app_t                *app;
    nxt_bool_t               cancelled, unlinked;
    nxt_port_t               *port;
    nxt_timer_t              *timer;
    nxt_queue_link_t         *lnk;
    nxt_http_request_t       *r;
    nxt_request_app_link_t   *pending_ra;
    nxt_request_rpc_data_t   *req_rpc_data;
    nxt_port_select_state_t  state;

    timer = obj;

    nxt_debug(task, "router app timeout");

    r = nxt_timer_data(timer, nxt_http_request_t, timer);
    req_rpc_data = r->timer_data;
    app = req_rpc_data->app;

    if (app == NULL) {
        goto generate_error;
    }

    port = NULL;
    pending_ra = NULL;

    if (req_rpc_data->app_port != NULL) {
        port = req_rpc_data->app_port;
        req_rpc_data->app_port = NULL;
    }

    if (port == NULL && req_rpc_data->req_app_link != NULL
        && req_rpc_data->req_app_link->app_port != NULL)
    {
        port = req_rpc_data->req_app_link->app_port;
        req_rpc_data->req_app_link->app_port = NULL;
    }

    if (port == NULL) {
        goto generate_error;
    }

    nxt_thread_mutex_lock(&app->mutex);

    unlinked = nxt_queue_chk_remove(&port->app_link);

    if (!nxt_queue_is_empty(&port->pending_requests)) {
        lnk = nxt_queue_first(&port->pending_requests);

        pending_ra = nxt_queue_link_data(lnk, nxt_request_app_link_t,
                                         link_port_pending);

        nxt_assert(pending_ra->link_app_pending.next != NULL);

        nxt_debug(task, "app '%V' pending request #%uD found",
                  &app->name, pending_ra->stream);

        cancelled = nxt_router_msg_cancel(task, &pending_ra->msg_info,
                                          pending_ra->stream);

        if (cancelled) {
            state.req_app_link = pending_ra;
            state.app = app;

            /*
             * Need to increment use count "in advance" because
             * nxt_router_port_select() will remove pending_ra from lists
             * and decrement use count.
             */
            nxt_request_app_link_inc_use(pending_ra);

            nxt_router_port_select(task, &state);

        } else {
            pending_ra = NULL;
        }
    }

    nxt_thread_mutex_unlock(&app->mutex);

    if (pending_ra != NULL) {
        if (nxt_router_port_post_select(task, &state) == NXT_OK) {
            /*
             * Reference counter already incremented above, this will
             * keep pending_ra while nxt_router_app_process_request()
             * task is in queue.  Reference counter decreased in
             * nxt_router_app_process_request() after processing.
             */

            nxt_work_queue_add(&task->thread->engine->fast_work_queue,
                               nxt_router_app_process_request,
                               &task->thread->engine->task, app, pending_ra);

        } else {
            nxt_request_app_link_use(task, pending_ra, -1);
        }
    }

    nxt_debug(task, "send quit to app '%V' pid %PI", &app->name, port->pid);

    nxt_port_socket_write(task, port, NXT_PORT_MSG_QUIT, -1, 0, 0, NULL);

    nxt_port_use(task, port, unlinked ? -2 : -1);

generate_error:

    nxt_http_request_error(task, r, NXT_HTTP_SERVICE_UNAVAILABLE);

    nxt_request_rpc_data_unlink(task, req_rpc_data);
}


static nxt_int_t
nxt_router_http_request_done(nxt_task_t *task, nxt_http_request_t *r)
{
    r->timer.handler = nxt_router_http_request_release;
    nxt_timer_add(task->thread->engine, &r->timer, 0);

    return NXT_OK;
}


static void
nxt_router_http_request_release(nxt_task_t *task, void *obj, void *data)
{
    nxt_http_request_t  *r;

    nxt_debug(task, "http app release");

    r = nxt_timer_data(obj, nxt_http_request_t, timer);

    nxt_mp_release(r->mem_pool);
}


static void
nxt_router_oosm_handler(nxt_task_t *task, nxt_port_recv_msg_t *msg)
{
    size_t                   mi;
    uint32_t                 i;
    nxt_bool_t               ack;
    nxt_process_t            *process;
    nxt_free_map_t           *m;
    nxt_port_mmap_header_t   *hdr;

    nxt_debug(task, "oosm in %PI", msg->port_msg.pid);

    process = nxt_runtime_process_find(task->thread->runtime,
                                       msg->port_msg.pid);
    if (nxt_slow_path(process == NULL)) {
        return;
    }

    ack = 0;

    /*
     * To mitigate possible racing condition (when OOSM message received
     * after some of the memory was already freed), need to try to find
     * first free segment in shared memory and send ACK if found.
     */

    nxt_thread_mutex_lock(&process->incoming.mutex);

    for (i = 0; i < process->incoming.size; i++) {
        hdr = process->incoming.elts[i].mmap_handler->hdr;
        m = hdr->free_map;

        for (mi = 0; mi < MAX_FREE_IDX; mi++) {
            if (m[mi] != 0) {
                ack = 1;

                nxt_debug(task, "oosm: already free #%uD %uz = 0x%08xA",
                          i, mi, m[mi]);

                break;
            }
        }
    }

    nxt_thread_mutex_unlock(&process->incoming.mutex);

    if (ack) {
        (void) nxt_port_socket_write(task, msg->port, NXT_PORT_MSG_SHM_ACK,
                                     -1, 0, 0, NULL);
    }
}