Moving request limit control to libunit.

Introducting application graceful stop.  For now only used when application
process reach request limit value.

This closes #585 issue on GitHub.

24 files changed, 273 insertions, 248 deletions

diff --git a/docs/changes.xml b/docs/changes.xml
index 3a5fa2b2..b9ddd3c7 100644
--- a/docs/changes.xml
+++ b/docs/changes.xml
@@ -50,6 +50,13 @@ NGINX Unit updated to 1.26.0.
 </para>
 </change>
 
+<change type="bugfix">
+<para>
+the router and app processes could crash when reaching requests limit
+in asynchronous or multithreaded apps.
+</para>
+</change>
+
 </changes>
 
 
diff --git a/go/port.go b/go/port.go
index 78351322..388adc4a 100644
--- a/go/port.go
+++ b/go/port.go
@@ -120,7 +120,8 @@ func nxt_go_add_port(ctx *C.nxt_unit_ctx_t, p *C.nxt_unit_port_t) C.int {
 }
 
 //export nxt_go_remove_port
-func nxt_go_remove_port(unit *C.nxt_unit_t, p *C.nxt_unit_port_t) {
+func nxt_go_remove_port(unit *C.nxt_unit_t, ctx *C.nxt_unit_ctx_t,
+	p *C.nxt_unit_port_t) {
 
 	key := port_key{
 		pid: int(p.id.pid),
diff --git a/src/nodejs/unit-http/unit.cpp b/src/nodejs/unit-http/unit.cpp
index 589eca3f..ee5dc46f 100644
--- a/src/nodejs/unit-http/unit.cpp
+++ b/src/nodejs/unit-http/unit.cpp
@@ -519,11 +519,11 @@ Unit::add_port(nxt_unit_ctx_t *ctx, nxt_unit_port_t *port)
 
 
 void
-Unit::remove_port(nxt_unit_t *unit, nxt_unit_port_t *port)
+Unit::remove_port(nxt_unit_t *unit, nxt_unit_ctx_t *ctx, nxt_unit_port_t *port)
 {
     port_data_t  *data;
 
-    if (port->data != NULL) {
+    if (port->data != NULL && ctx != NULL) {
         data = (port_data_t *) port->data;
 
         data->stop();
diff --git a/src/nodejs/unit-http/unit.h b/src/nodejs/unit-http/unit.h
index 4ef40d45..1aa93073 100644
--- a/src/nodejs/unit-http/unit.h
+++ b/src/nodejs/unit-http/unit.h
@@ -41,7 +41,8 @@ private:
     void shm_ack_handler(nxt_unit_ctx_t *ctx);
 
     static int add_port(nxt_unit_ctx_t *ctx, nxt_unit_port_t *port);
-    static void remove_port(nxt_unit_t *unit, nxt_unit_port_t *port);
+    static void remove_port(nxt_unit_t *unit, nxt_unit_ctx_t *ctx,
+                            nxt_unit_port_t *port);
 
     static void quit_cb(nxt_unit_ctx_t *ctx);
     void quit(nxt_unit_ctx_t *ctx);
diff --git a/src/nxt_application.c b/src/nxt_application.c
index 5d58e60c..096ba4b4 100644
--- a/src/nxt_application.c
+++ b/src/nxt_application.c
@@ -687,7 +687,8 @@ nxt_app_parse_type(u_char *p, size_t length)
 
 
 nxt_int_t
-nxt_unit_default_init(nxt_task_t *task, nxt_unit_init_t *init)
+nxt_unit_default_init(nxt_task_t *task, nxt_unit_init_t *init,
+    nxt_common_app_conf_t *conf)
 {
     nxt_port_t     *my_port, *main_port, *router_port;
     nxt_runtime_t  *rt;
@@ -730,5 +731,8 @@ nxt_unit_default_init(nxt_task_t *task, nxt_unit_init_t *init)
 
     init->log_fd = 2;
 
+    init->shm_limit = conf->shm_limit;
+    init->request_limit = conf->request_limit;
+
     return NXT_OK;
 }
diff --git a/src/nxt_application.h b/src/nxt_application.h
index 6fbdc4be..4612f072 100644
--- a/src/nxt_application.h
+++ b/src/nxt_application.h
@@ -101,6 +101,7 @@ struct nxt_common_app_conf_s {
     nxt_conf_value_t           *limits;
 
     size_t                     shm_limit;
+    uint32_t                   request_limit;
 
     union {
         nxt_external_app_conf_t  external;
@@ -137,7 +138,7 @@ NXT_EXPORT extern nxt_str_t  nxt_server;
 extern nxt_app_module_t      nxt_external_module;
 
 NXT_EXPORT nxt_int_t nxt_unit_default_init(nxt_task_t *task,
-    nxt_unit_init_t *init);
+    nxt_unit_init_t *init, nxt_common_app_conf_t *conf);
 
 
 #endif /* _NXT_APPLICATION_H_INCLIDED_ */
diff --git a/src/nxt_external.c b/src/nxt_external.c
index 5703e294..1275aa87 100644
--- a/src/nxt_external.c
+++ b/src/nxt_external.c
@@ -113,13 +113,13 @@ nxt_external_start(nxt_task_t *task, nxt_process_data_t *data)
                     "%PI,%ud,%d;"
                     "%PI,%ud,%d;"
                     "%PI,%ud,%d,%d;"
-                    "%d,%z,%Z",
+                    "%d,%z,%uD,%Z",
                     NXT_VERSION, my_port->process->stream,
                     main_port->pid, main_port->id, main_port->pair[1],
                     router_port->pid, router_port->id, router_port->pair[1],
                     my_port->pid, my_port->id, my_port->pair[0],
                                                my_port->pair[1],
-                    2, conf->shm_limit);
+                    2, conf->shm_limit, conf->request_limit);
 
     if (nxt_slow_path(p == end)) {
         nxt_alert(task, "internal error: buffer too small for NXT_UNIT_INIT");
diff --git a/src/nxt_java.c b/src/nxt_java.c
index ac715c0b..75c8ee19 100644
--- a/src/nxt_java.c
+++ b/src/nxt_java.c
@@ -428,7 +428,7 @@ nxt_java_start(nxt_task_t *task, nxt_process_data_t *data)
         return NXT_ERROR;
     }
 
-    nxt_unit_default_init(task, &java_init);
+    nxt_unit_default_init(task, &java_init, app_conf);
 
     java_init.callbacks.request_handler = nxt_java_request_handler;
     java_init.callbacks.websocket_handler = nxt_java_websocket_handler;
@@ -437,7 +437,6 @@ nxt_java_start(nxt_task_t *task, nxt_process_data_t *data)
     java_init.request_data_size = sizeof(nxt_java_request_data_t);
     java_init.data = &java_data;
     java_init.ctx_data = env;
-    java_init.shm_limit = app_conf->shm_limit;
 
     ctx = nxt_unit_init(&java_init);
     if (nxt_slow_path(ctx == NULL)) {
@@ -616,11 +615,6 @@ nxt_java_ready_handler(nxt_unit_ctx_t *ctx)
     nxt_java_data_t      *java_data;
     nxt_java_app_conf_t  *c;
 
-    /* Worker thread context. */
-    if (!nxt_unit_is_main_ctx(ctx)) {
-        return NXT_UNIT_OK;
-    }
-
     java_data = ctx->unit->data;
     c = java_data->conf;
 
diff --git a/src/nxt_main_process.c b/src/nxt_main_process.c
index 86425dab..fe21aeb5 100644
--- a/src/nxt_main_process.c
+++ b/src/nxt_main_process.c
@@ -154,6 +154,12 @@ static nxt_conf_map_t  nxt_common_app_limits_conf[] = {
         offsetof(nxt_common_app_conf_t, shm_limit),
     },
 
+    {
+        nxt_string("requests"),
+        NXT_CONF_MAP_INT32,
+        offsetof(nxt_common_app_conf_t, request_limit),
+    },
+
 };
 
 
@@ -392,6 +398,7 @@ nxt_port_main_start_process_handler(nxt_task_t *task, nxt_port_recv_msg_t *msg)
     *p = '\0';
 
     app_conf->shm_limit = 100 * 1024 * 1024;
+    app_conf->request_limit = 0;
 
     start += app_conf->name.length + 1;
 
diff --git a/src/nxt_php_sapi.c b/src/nxt_php_sapi.c
index 3fb3b0db..ea5f5581 100644
--- a/src/nxt_php_sapi.c
+++ b/src/nxt_php_sapi.c
@@ -485,14 +485,13 @@ nxt_php_start(nxt_task_t *task, nxt_process_data_t *data)
         }
     }
 
-    ret = nxt_unit_default_init(task, &php_init);
+    ret = nxt_unit_default_init(task, &php_init, conf);
     if (nxt_slow_path(ret != NXT_OK)) {
         nxt_alert(task, "nxt_unit_default_init() failed");
         return ret;
     }
 
     php_init.callbacks.request_handler = nxt_php_request_handler;
-    php_init.shm_limit = conf->shm_limit;
 
     unit_ctx = nxt_unit_init(&php_init);
     if (nxt_slow_path(unit_ctx == NULL)) {
diff --git a/src/nxt_port.h b/src/nxt_port.h
index a0bc2512..c698a49c 100644
--- a/src/nxt_port.h
+++ b/src/nxt_port.h
@@ -224,8 +224,6 @@ struct nxt_port_s {
     /* Maximum interleave of message parts. */
     uint32_t            max_share;
 
-    uint32_t            app_responses;
-
     uint32_t            active_websockets;
     uint32_t            active_requests;
 
diff --git a/src/nxt_router.c b/src/nxt_router.c
index bbfe3dcf..9317d752 100644
--- a/src/nxt_router.c
+++ b/src/nxt_router.c
@@ -27,7 +27,6 @@ typedef struct {
     uint32_t          spare_processes;
     nxt_msec_t        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;
@@ -1293,12 +1292,6 @@ static nxt_conf_map_t  nxt_router_app_limits_conf[] = {
         NXT_CONF_MAP_MSEC,
         offsetof(nxt_router_app_conf_t, timeout),
     },
-
-    {
-        nxt_string("requests"),
-        NXT_CONF_MAP_INT32,
-        offsetof(nxt_router_app_conf_t, requests),
-    },
 };
 
 
@@ -1567,7 +1560,6 @@ nxt_router_conf_create(nxt_task_t *task, nxt_router_temp_conf_t *tmcf,
             apcf.spare_processes = 0;
             apcf.timeout = 0;
             apcf.idle_timeout = 15000;
-            apcf.requests = 0;
             apcf.limits_value = NULL;
             apcf.processes_value = NULL;
             apcf.targets_value = NULL;
@@ -1647,7 +1639,6 @@ nxt_router_conf_create(nxt_task_t *task, nxt_router_temp_conf_t *tmcf,
             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 requests: %D", apcf.requests);
 
             lang = nxt_app_lang_module(task->thread->runtime, &apcf.type);
 
@@ -1678,7 +1669,6 @@ nxt_router_conf_create(nxt_task_t *task, nxt_router_temp_conf_t *tmcf,
                                          ? apcf.spare_processes : 1;
             app->timeout = apcf.timeout;
             app->idle_timeout = apcf.idle_timeout;
-            app->max_requests = apcf.requests;
 
             app->targets = targets;
 
@@ -4676,7 +4666,7 @@ nxt_router_app_port_release(nxt_task_t *task, nxt_app_t *app, nxt_port_t *port,
 {
     int         inc_use;
     uint32_t    got_response, dec_requests;
-    nxt_bool_t  port_unchained, send_quit, adjust_idle_timer;
+    nxt_bool_t  adjust_idle_timer;
     nxt_port_t  *main_app_port;
 
     nxt_assert(port != NULL);
@@ -4722,40 +4712,18 @@ nxt_router_app_port_release(nxt_task_t *task, nxt_app_t *app, nxt_port_t *port,
 
     nxt_thread_mutex_lock(&app->mutex);
 
-    main_app_port->app_responses += got_response;
     main_app_port->active_requests -= got_response + dec_requests;
     app->active_requests -= got_response + dec_requests;
 
-    if (main_app_port->pair[1] != -1
-        && (app->max_requests == 0
-            || main_app_port->app_responses < app->max_requests))
-    {
-        if (main_app_port->app_link.next == NULL) {
-            nxt_queue_insert_tail(&app->ports, &main_app_port->app_link);
-
-            nxt_port_inc_use(main_app_port);
-        }
-    }
-
-    send_quit = (app->max_requests > 0
-                 && main_app_port->app_responses >= app->max_requests);
-
-    if (send_quit) {
-        port_unchained = nxt_queue_chk_remove(&main_app_port->app_link);
-
-        nxt_port_hash_remove(&app->port_hash, main_app_port);
-        app->port_hash_count--;
-
-        main_app_port->app = NULL;
-        app->processes--;
+    if (main_app_port->pair[1] != -1 && main_app_port->app_link.next == NULL) {
+        nxt_queue_insert_tail(&app->ports, &main_app_port->app_link);
 
-    } else {
-        port_unchained = 0;
+        nxt_port_inc_use(main_app_port);
     }
 
     adjust_idle_timer = 0;
 
-    if (main_app_port->pair[1] != -1 && !send_quit
+    if (main_app_port->pair[1] != -1
         && main_app_port->active_requests == 0
         && main_app_port->active_websockets == 0
         && main_app_port->idle_link.next == NULL)
@@ -4800,19 +4768,6 @@ nxt_router_app_port_release(nxt_task_t *task, nxt_app_t *app, nxt_port_t *port,
         goto adjust_use;
     }
 
-    if (send_quit) {
-        nxt_debug(task, "app '%V' %p send QUIT to port", &app->name, app);
-
-        nxt_port_socket_write(task, main_app_port, NXT_PORT_MSG_QUIT, -1, 0, 0,
-                              NULL);
-
-        if (port_unchained) {
-            nxt_port_use(task, main_app_port, -1);
-        }
-
-        goto adjust_use;
-    }
-
     nxt_debug(task, "app '%V' %p requests queue is empty, keep the port",
               &app->name, app);
 
diff --git a/src/nxt_router.h b/src/nxt_router.h
index fc068b53..011663c3 100644
--- a/src/nxt_router.h
+++ b/src/nxt_router.h
@@ -124,7 +124,6 @@ struct nxt_app_s {
     uint32_t               max_processes;
     uint32_t               spare_processes;
     uint32_t               max_pending_processes;
-    uint32_t               max_requests;
 
     uint32_t               generation;
 
diff --git a/src/nxt_unit.c b/src/nxt_unit.c
index ae4499d8..3a31becd 100644
--- a/src/nxt_unit.c
+++ b/src/nxt_unit.c
@@ -25,6 +25,11 @@
 #define NXT_UNIT_LOCAL_BUF_SIZE  \
     (NXT_UNIT_MAX_PLAIN_SIZE + sizeof(nxt_port_msg_t))
 
+enum {
+    NXT_QUIT_NORMAL   = 0,
+    NXT_QUIT_GRACEFUL = 1,
+};
+
 typedef struct nxt_unit_impl_s                  nxt_unit_impl_t;
 typedef struct nxt_unit_mmap_s                  nxt_unit_mmap_t;
 typedef struct nxt_unit_mmaps_s                 nxt_unit_mmaps_t;
@@ -51,7 +56,8 @@ nxt_inline void nxt_unit_mmap_buf_insert_tail(nxt_unit_mmap_buf_t **prev,
 nxt_inline void nxt_unit_mmap_buf_unlink(nxt_unit_mmap_buf_t *mmap_buf);
 static int nxt_unit_read_env(nxt_unit_port_t *ready_port,
     nxt_unit_port_t *router_port, nxt_unit_port_t *read_port,
-    int *log_fd, uint32_t *stream, uint32_t *shm_limit);
+    int *log_fd, uint32_t *stream, uint32_t *shm_limit,
+    uint32_t *request_limit);
 static int nxt_unit_ready(nxt_unit_ctx_t *ctx, int ready_fd, uint32_t stream,
     int queue_fd);
 static int nxt_unit_process_msg(nxt_unit_ctx_t *ctx, nxt_unit_read_buf_t *rbuf,
@@ -130,6 +136,7 @@ static nxt_unit_process_t *nxt_unit_process_find(nxt_unit_impl_t *lib,
 static nxt_unit_process_t *nxt_unit_process_pop_first(nxt_unit_impl_t *lib);
 static int nxt_unit_run_once_impl(nxt_unit_ctx_t *ctx);
 static int nxt_unit_read_buf(nxt_unit_ctx_t *ctx, nxt_unit_read_buf_t *rbuf);
+static int nxt_unit_chk_ready(nxt_unit_ctx_t *ctx);
 static int nxt_unit_process_pending_rbuf(nxt_unit_ctx_t *ctx);
 static void nxt_unit_process_ready_req(nxt_unit_ctx_t *ctx);
 nxt_inline int nxt_unit_is_read_queue(nxt_unit_read_buf_t *rbuf);
@@ -150,14 +157,14 @@ static nxt_unit_port_t *nxt_unit_add_port(nxt_unit_ctx_t *ctx,
     nxt_unit_port_t *port, void *queue);
 static void nxt_unit_process_awaiting_req(nxt_unit_ctx_t *ctx,
     nxt_queue_t *awaiting_req);
-static void nxt_unit_remove_port(nxt_unit_impl_t *lib,
+static void nxt_unit_remove_port(nxt_unit_impl_t *lib, nxt_unit_ctx_t *ctx,
     nxt_unit_port_id_t *port_id);
 static nxt_unit_port_t *nxt_unit_remove_port_unsafe(nxt_unit_impl_t *lib,
     nxt_unit_port_id_t *port_id);
 static void nxt_unit_remove_pid(nxt_unit_impl_t *lib, pid_t pid);
 static void nxt_unit_remove_process(nxt_unit_impl_t *lib,
     nxt_unit_process_t *process);
-static void nxt_unit_quit(nxt_unit_ctx_t *ctx);
+static void nxt_unit_quit(nxt_unit_ctx_t *ctx, uint8_t quit_param);
 static int nxt_unit_get_port(nxt_unit_ctx_t *ctx, nxt_unit_port_id_t *port_id);
 static ssize_t nxt_unit_port_send(nxt_unit_ctx_t *ctx,
     nxt_unit_port_t *port, const void *buf, size_t buf_size,
@@ -174,7 +181,7 @@ static int nxt_unit_port_recv(nxt_unit_ctx_t *ctx, nxt_unit_port_t *port,
     nxt_unit_read_buf_t *rbuf);
 static int nxt_unit_port_queue_recv(nxt_unit_port_t *port,
     nxt_unit_read_buf_t *rbuf);
-static int nxt_unit_app_queue_recv(nxt_unit_port_t *port,
+static int nxt_unit_app_queue_recv(nxt_unit_ctx_t *ctx, nxt_unit_port_t *port,
     nxt_unit_read_buf_t *rbuf);
 nxt_inline int nxt_unit_close(int fd);
 static int nxt_unit_fd_blocking(int fd);
@@ -311,8 +318,9 @@ struct nxt_unit_ctx_impl_s {
     /*  of nxt_unit_read_buf_t */
     nxt_queue_t                   free_rbuf;
 
-    int                           online;
-    int                           ready;
+    uint8_t                       online;       /* 1 bit */
+    uint8_t                       ready;        /* 1 bit */
+    uint8_t                       quit_param;
 
     nxt_unit_mmap_buf_t           ctx_buf[2];
     nxt_unit_read_buf_t           ctx_read_buf;
@@ -344,9 +352,11 @@ struct nxt_unit_impl_s {
     nxt_unit_callbacks_t     callbacks;
 
     nxt_atomic_t             use_count;
+    nxt_atomic_t             request_count;
 
     uint32_t                 request_data_size;
     uint32_t                 shm_mmap_limit;
+    uint32_t                 request_limit;
 
     pthread_mutex_t          mutex;
 
@@ -414,7 +424,7 @@ nxt_unit_init(nxt_unit_init_t *init)
 {
     int              rc, queue_fd;
     void             *mem;
-    uint32_t         ready_stream, shm_limit;
+    uint32_t         ready_stream, shm_limit, request_limit;
     nxt_unit_ctx_t   *ctx;
     nxt_unit_impl_t  *lib;
     nxt_unit_port_t  ready_port, router_port, read_port;
@@ -446,13 +456,15 @@ nxt_unit_init(nxt_unit_init_t *init)
 
     } else {
         rc = nxt_unit_read_env(&ready_port, &router_port, &read_port,
-                               &lib->log_fd, &ready_stream, &shm_limit);
+                               &lib->log_fd, &ready_stream, &shm_limit,
+                               &request_limit);
         if (nxt_slow_path(rc != NXT_UNIT_OK)) {
             goto fail;
         }
 
         lib->shm_mmap_limit = (shm_limit + PORT_MMAP_DATA_SIZE - 1)
                                 / PORT_MMAP_DATA_SIZE;
+        lib->request_limit = request_limit;
     }
 
     if (nxt_slow_path(lib->shm_mmap_limit < 1)) {
@@ -564,6 +576,7 @@ nxt_unit_create(nxt_unit_init_t *init)
     lib->request_data_size = init->request_data_size;
     lib->shm_mmap_limit = (init->shm_limit + PORT_MMAP_DATA_SIZE - 1)
                             / PORT_MMAP_DATA_SIZE;
+    lib->request_limit = init->request_limit;
 
     lib->processes.slot = NULL;
     lib->ports.slot = NULL;
@@ -573,6 +586,7 @@ nxt_unit_create(nxt_unit_init_t *init)
     nxt_queue_init(&lib->contexts);
 
     lib->use_count = 0;
+    lib->request_count = 0;
     lib->router_port = NULL;
     lib->shared_port = NULL;
 
@@ -632,6 +646,7 @@ nxt_unit_ctx_init(nxt_unit_impl_t *lib, nxt_unit_ctx_impl_t *ctx_impl,
     ctx_impl->wait_items = 0;
     ctx_impl->online = 1;
     ctx_impl->ready = 0;
+    ctx_impl->quit_param = NXT_QUIT_GRACEFUL;
 
     nxt_queue_init(&ctx_impl->free_req);
     nxt_queue_init(&ctx_impl->free_ws);
@@ -780,7 +795,7 @@ nxt_unit_mmap_buf_unlink(nxt_unit_mmap_buf_t *mmap_buf)
 static int
 nxt_unit_read_env(nxt_unit_port_t *ready_port, nxt_unit_port_t *router_port,
     nxt_unit_port_t *read_port, int *log_fd, uint32_t *stream,
-    uint32_t *shm_limit)
+    uint32_t *shm_limit, uint32_t *request_limit)
 {
     int       rc;
     int       ready_fd, router_fd, read_in_fd, read_out_fd;
@@ -825,12 +840,12 @@ nxt_unit_read_env(nxt_unit_port_t *ready_port, nxt_unit_port_t *router_port,
                 "%"PRId64",%"PRIu32",%d;"
                 "%"PRId64",%"PRIu32",%d;"
                 "%"PRId64",%"PRIu32",%d,%d;"
-                "%d,%"PRIu32,
+                "%d,%"PRIu32",%"PRIu32,
                 &ready_stream,
                 &ready_pid, &ready_id, &ready_fd,
                 &router_pid, &router_id, &router_fd,
                 &read_pid, &read_id, &read_in_fd, &read_out_fd,
-                log_fd, shm_limit);
+                log_fd, shm_limit, request_limit);
 
     if (nxt_slow_path(rc == EOF)) {
         nxt_unit_alert(NULL, "sscanf(%s) failed: %s (%d) for %s env",
@@ -839,9 +854,9 @@ nxt_unit_read_env(nxt_unit_port_t *ready_port, nxt_unit_port_t *router_port,
         return NXT_UNIT_ERROR;
     }
 
-    if (nxt_slow_path(rc != 13)) {
+    if (nxt_slow_path(rc != 14)) {
         nxt_unit_alert(NULL, "invalid number of variables in %s env: "
-                       "found %d of %d in %s", NXT_UNIT_INIT_ENV, rc, 13, vars);
+                       "found %d of %d in %s", NXT_UNIT_INIT_ENV, rc, 14, vars);
 
         return NXT_UNIT_ERROR;
     }
@@ -929,6 +944,7 @@ nxt_unit_process_msg(nxt_unit_ctx_t *ctx, nxt_unit_read_buf_t *rbuf,
 {
     int                  rc;
     pid_t                pid;
+    uint8_t              quit_param;
     struct cmsghdr       *cm;
     nxt_port_msg_t       *port_msg;
     nxt_unit_impl_t      *lib;
@@ -959,7 +975,7 @@ nxt_unit_process_msg(nxt_unit_ctx_t *ctx, nxt_unit_read_buf_t *rbuf,
         if (nxt_slow_path(rbuf->size == 0)) {
             nxt_unit_debug(ctx, "read port closed");
 
-            nxt_unit_quit(ctx);
+            nxt_unit_quit(ctx, NXT_QUIT_GRACEFUL);
             rc = NXT_UNIT_OK;
             goto done;
         }
@@ -1018,9 +1034,18 @@ nxt_unit_process_msg(nxt_unit_ctx_t *ctx, nxt_unit_read_buf_t *rbuf,
         break;
 
     case _NXT_PORT_MSG_QUIT:
-        nxt_unit_debug(ctx, "#%"PRIu32": quit", port_msg->stream);
+        if (recv_msg.size == sizeof(quit_param)) {
+            memcpy(&quit_param, recv_msg.start, sizeof(quit_param));
+
+        } else {
+            quit_param = NXT_QUIT_NORMAL;
+        }
+
+        nxt_unit_debug(ctx, "#%"PRIu32": %squit", port_msg->stream,
+                       (quit_param == NXT_QUIT_GRACEFUL ? "graceful " : ""));
+
+        nxt_unit_quit(ctx, quit_param);
 
-        nxt_unit_quit(ctx);
         rc = NXT_UNIT_OK;
         break;
 
@@ -1220,15 +1245,36 @@ nxt_unit_ctx_ready(nxt_unit_ctx_t *ctx)
     nxt_unit_impl_t      *lib;
     nxt_unit_ctx_impl_t  *ctx_impl;
 
-    lib = nxt_container_of(ctx->unit, nxt_unit_impl_t, unit);
     ctx_impl = nxt_container_of(ctx, nxt_unit_ctx_impl_t, ctx);
 
+    if (nxt_slow_path(ctx_impl->ready)) {
+        return NXT_UNIT_OK;
+    }
+
     ctx_impl->ready = 1;
 
-    if (lib->callbacks.ready_handler) {
+    lib = nxt_container_of(ctx->unit, nxt_unit_impl_t, unit);
+
+    /* Call ready_handler() only for main context. */
+    if (&lib->main_ctx == ctx_impl && lib->callbacks.ready_handler != NULL) {
         return lib->callbacks.ready_handler(ctx);
     }
 
+    if (&lib->main_ctx != ctx_impl) {
+        /* Check if the main context is already stopped or quit. */
+        if (nxt_slow_path(!lib->main_ctx.ready)) {
+            ctx_impl->ready = 0;
+
+            nxt_unit_quit(ctx, lib->main_ctx.quit_param);
+
+            return NXT_UNIT_OK;
+        }
+
+        if (lib->callbacks.add_port != NULL) {
+            lib->callbacks.add_port(ctx, lib->shared_port);
+        }
+    }
+
     return NXT_UNIT_OK;
 }
 
@@ -1741,10 +1787,12 @@ nxt_unit_request_info_get(nxt_unit_ctx_t *ctx)
 static void
 nxt_unit_request_info_release(nxt_unit_request_info_t *req)
 {
+    nxt_unit_ctx_t                *ctx;
     nxt_unit_ctx_impl_t           *ctx_impl;
     nxt_unit_request_info_impl_t  *req_impl;
 
-    ctx_impl = nxt_container_of(req->ctx, nxt_unit_ctx_impl_t, ctx);
+    ctx = req->ctx;
+    ctx_impl = nxt_container_of(ctx, nxt_unit_ctx_impl_t, ctx);
     req_impl = nxt_container_of(req, nxt_unit_request_info_impl_t, req);
 
     req->response = NULL;
@@ -1783,6 +1831,10 @@ nxt_unit_request_info_release(nxt_unit_request_info_t *req)
     nxt_queue_insert_tail(&ctx_impl->free_req, &req_impl->link);
 
     pthread_mutex_unlock(&ctx_impl->mutex);
+
+    if (nxt_slow_path(!nxt_unit_chk_ready(ctx))) {
+        nxt_unit_quit(ctx, NXT_QUIT_GRACEFUL);
+    }
 }
 
 
@@ -4522,7 +4574,7 @@ nxt_unit_run(nxt_unit_ctx_t *ctx)
         rc = nxt_unit_run_once_impl(ctx);
 
         if (nxt_slow_path(rc == NXT_UNIT_ERROR)) {
-            nxt_unit_quit(ctx);
+            nxt_unit_quit(ctx, NXT_QUIT_NORMAL);
             break;
         }
     }
@@ -4586,6 +4638,7 @@ static int
 nxt_unit_read_buf(nxt_unit_ctx_t *ctx, nxt_unit_read_buf_t *rbuf)
 {
     int                   nevents, res, err;
+    nxt_uint_t            nfds;
     nxt_unit_impl_t       *lib;
     nxt_unit_ctx_impl_t   *ctx_impl;
     nxt_unit_port_impl_t  *port_impl;
@@ -4593,7 +4646,7 @@ nxt_unit_read_buf(nxt_unit_ctx_t *ctx, nxt_unit_read_buf_t *rbuf)
 
     ctx_impl = nxt_container_of(ctx, nxt_unit_ctx_impl_t, ctx);
 
-    if (ctx_impl->wait_items > 0 || ctx_impl->ready == 0) {
+    if (ctx_impl->wait_items > 0 || !nxt_unit_chk_ready(ctx)) {
         return nxt_unit_ctx_port_recv(ctx, ctx_impl->read_port, rbuf);
     }
 
@@ -4626,20 +4679,28 @@ retry:
         }
     }
 
-    res = nxt_unit_app_queue_recv(lib->shared_port, rbuf);
-    if (res == NXT_UNIT_OK) {
-        return NXT_UNIT_OK;
+    if (nxt_fast_path(nxt_unit_chk_ready(ctx))) {
+        res = nxt_unit_app_queue_recv(ctx, lib->shared_port, rbuf);
+        if (res == NXT_UNIT_OK) {
+            return NXT_UNIT_OK;
+        }
+
+        fds[1].fd = lib->shared_port->in_fd;
+        fds[1].events = POLLIN;
+
+        nfds = 2;
+
+    } else {
+        nfds = 1;
     }
 
     fds[0].fd = ctx_impl->read_port->in_fd;
     fds[0].events = POLLIN;
     fds[0].revents = 0;
 
-    fds[1].fd = lib->shared_port->in_fd;
-    fds[1].events = POLLIN;
     fds[1].revents = 0;
 
-    nevents = poll(fds, 2, -1);
+    nevents = poll(fds, nfds, -1);
     if (nxt_slow_path(nevents == -1)) {
         err = errno;
 
@@ -4686,6 +4747,21 @@ retry:
 
 
 static int
+nxt_unit_chk_ready(nxt_unit_ctx_t *ctx)
+{
+    nxt_unit_impl_t      *lib;
+    nxt_unit_ctx_impl_t  *ctx_impl;
+
+    ctx_impl = nxt_container_of(ctx, nxt_unit_ctx_impl_t, ctx);
+    lib = nxt_container_of(ctx->unit, nxt_unit_impl_t, unit);
+
+    return (ctx_impl->ready
+            && (lib->request_limit == 0
+                || lib->request_count < lib->request_limit));
+}
+
+
+static int
 nxt_unit_process_pending_rbuf(nxt_unit_ctx_t *ctx)
 {
     int                  rc;
@@ -4723,6 +4799,10 @@ nxt_unit_process_pending_rbuf(nxt_unit_ctx_t *ctx)
 
     } nxt_queue_loop;
 
+    if (!ctx_impl->ready) {
+        nxt_unit_quit(ctx, NXT_QUIT_GRACEFUL);
+    }
+
     return rc;
 }
 
@@ -4903,16 +4983,14 @@ nxt_unit_run_shared(nxt_unit_ctx_t *ctx)
     int                  rc;
     nxt_unit_impl_t      *lib;
     nxt_unit_read_buf_t  *rbuf;
-    nxt_unit_ctx_impl_t  *ctx_impl;
 
     nxt_unit_ctx_use(ctx);
 
     lib = nxt_container_of(ctx->unit, nxt_unit_impl_t, unit);
-    ctx_impl = nxt_container_of(ctx, nxt_unit_ctx_impl_t, ctx);
 
     rc = NXT_UNIT_OK;
 
-    while (nxt_fast_path(ctx_impl->online)) {
+    while (nxt_fast_path(nxt_unit_chk_ready(ctx))) {
         rbuf = nxt_unit_read_buf_get(ctx);
         if (nxt_slow_path(rbuf == NULL)) {
             rc = NXT_UNIT_ERROR;
@@ -4949,17 +5027,15 @@ nxt_unit_dequeue_request(nxt_unit_ctx_t *ctx)
     int                      rc;
     nxt_unit_impl_t          *lib;
     nxt_unit_read_buf_t      *rbuf;
-    nxt_unit_ctx_impl_t      *ctx_impl;
     nxt_unit_request_info_t  *req;
 
     nxt_unit_ctx_use(ctx);
 
     lib = nxt_container_of(ctx->unit, nxt_unit_impl_t, unit);
-    ctx_impl = nxt_container_of(ctx, nxt_unit_ctx_impl_t, ctx);
 
     req = NULL;
 
-    if (nxt_slow_path(!ctx_impl->online)) {
+    if (nxt_slow_path(!nxt_unit_chk_ready(ctx))) {
         goto done;
     }
 
@@ -4968,7 +5044,7 @@ nxt_unit_dequeue_request(nxt_unit_ctx_t *ctx)
         goto done;
     }
 
-    rc = nxt_unit_app_queue_recv(lib->shared_port, rbuf);
+    rc = nxt_unit_app_queue_recv(ctx, lib->shared_port, rbuf);
     if (rc != NXT_UNIT_OK) {
         nxt_unit_read_buf_release(ctx, rbuf);
         goto done;
@@ -4985,17 +5061,6 @@ done:
 
 
 int
-nxt_unit_is_main_ctx(nxt_unit_ctx_t *ctx)
-{
-    nxt_unit_impl_t  *lib;
-
-    lib = nxt_container_of(ctx->unit, nxt_unit_impl_t, unit);
-
-    return (ctx == &lib->main_ctx.ctx);
-}
-
-
-int
 nxt_unit_process_port_msg(nxt_unit_ctx_t *ctx, nxt_unit_port_t *port)
 {
     int  rc;
@@ -5017,13 +5082,17 @@ nxt_unit_process_port_msg_impl(nxt_unit_ctx_t *ctx, nxt_unit_port_t *port)
     nxt_unit_impl_t      *lib;
     nxt_unit_read_buf_t  *rbuf;
 
+    lib = nxt_container_of(ctx->unit, nxt_unit_impl_t, unit);
+
+    if (port == lib->shared_port && !nxt_unit_chk_ready(ctx)) {
+        return NXT_UNIT_AGAIN;
+    }
+
     rbuf = nxt_unit_read_buf_get(ctx);
     if (nxt_slow_path(rbuf == NULL)) {
         return NXT_UNIT_ERROR;
     }
 
-    lib = nxt_container_of(ctx->unit, nxt_unit_impl_t, unit);
-
     if (port == lib->shared_port) {
         rc = nxt_unit_shared_port_recv(ctx, port, rbuf);
 
@@ -5194,7 +5263,7 @@ nxt_unit_ctx_free(nxt_unit_ctx_impl_t *ctx_impl)
     pthread_mutex_unlock(&lib->mutex);
 
     if (nxt_fast_path(ctx_impl->read_port != NULL)) {
-        nxt_unit_remove_port(lib, &ctx_impl->read_port->id);
+        nxt_unit_remove_port(lib, NULL, &ctx_impl->read_port->id);
         nxt_unit_port_release(ctx_impl->read_port);
     }
 
@@ -5605,7 +5674,8 @@ nxt_unit_process_awaiting_req(nxt_unit_ctx_t *ctx, nxt_queue_t *awaiting_req)
 
 
 static void
-nxt_unit_remove_port(nxt_unit_impl_t *lib, nxt_unit_port_id_t *port_id)
+nxt_unit_remove_port(nxt_unit_impl_t *lib, nxt_unit_ctx_t *ctx,
+    nxt_unit_port_id_t *port_id)
 {
     nxt_unit_port_t       *port;
     nxt_unit_port_impl_t  *port_impl;
@@ -5623,7 +5693,7 @@ nxt_unit_remove_port(nxt_unit_impl_t *lib, nxt_unit_port_id_t *port_id)
     pthread_mutex_unlock(&lib->mutex);
 
     if (lib->callbacks.remove_port != NULL && port != NULL) {
-        lib->callbacks.remove_port(&lib->unit, port);
+        lib->callbacks.remove_port(&lib->unit, ctx, port);
     }
 
     if (nxt_fast_path(port != NULL)) {
@@ -5700,7 +5770,7 @@ nxt_unit_remove_process(nxt_unit_impl_t *lib, nxt_unit_process_t *process)
         nxt_queue_remove(&port->link);
 
         if (lib->callbacks.remove_port != NULL) {
-            lib->callbacks.remove_port(&lib->unit, &port->port);
+            lib->callbacks.remove_port(&lib->unit, NULL, &port->port);
         }
 
         nxt_unit_port_release(&port->port);
@@ -5712,56 +5782,96 @@ nxt_unit_remove_process(nxt_unit_impl_t *lib, nxt_unit_process_t *process)
 
 
 static void
-nxt_unit_quit(nxt_unit_ctx_t *ctx)
+nxt_unit_quit(nxt_unit_ctx_t *ctx, uint8_t quit_param)
 {
-    nxt_port_msg_t                msg;
+    nxt_bool_t                    skip_graceful_broadcast, quit;
     nxt_unit_impl_t               *lib;
     nxt_unit_ctx_impl_t           *ctx_impl;
     nxt_unit_callbacks_t          *cb;
     nxt_unit_request_info_t       *req;
     nxt_unit_request_info_impl_t  *req_impl;
 
+    struct {
+        nxt_port_msg_t            msg;
+        uint8_t                   quit_param;
+    } nxt_packed m;
+
     lib = nxt_container_of(ctx->unit, nxt_unit_impl_t, unit);
     ctx_impl = nxt_container_of(ctx, nxt_unit_ctx_impl_t, ctx);
 
-    if (!ctx_impl->online) {
+    nxt_unit_debug(ctx, "quit: %d/%d/%d", (int) quit_param, ctx_impl->ready,
+                   ctx_impl->online);
+
+    if (nxt_slow_path(!ctx_impl->online)) {
         return;
     }
 
-    ctx_impl->online = 0;
+    skip_graceful_broadcast = quit_param == NXT_QUIT_GRACEFUL
+                              && !ctx_impl->ready;
 
     cb = &lib->callbacks;
 
-    if (cb->quit != NULL) {
-        cb->quit(ctx);
+    if (nxt_fast_path(ctx_impl->ready)) {
+        ctx_impl->ready = 0;
+
+        if (cb->remove_port != NULL) {
+            cb->remove_port(&lib->unit, ctx, lib->shared_port);
+        }
     }
 
-    nxt_queue_each(req_impl, &ctx_impl->active_req,
-                   nxt_unit_request_info_impl_t, link)
-    {
-        req = &req_impl->req;
+    if (quit_param == NXT_QUIT_GRACEFUL) {
+        pthread_mutex_lock(&ctx_impl->mutex);
 
-        nxt_unit_req_warn(req, "active request on ctx quit");
+        quit = nxt_queue_is_empty(&ctx_impl->active_req)
+               && nxt_queue_is_empty(&ctx_impl->pending_rbuf)
+               && ctx_impl->wait_items == 0;
 
-        if (cb->close_handler) {
-            nxt_unit_req_debug(req, "close_handler");
+        pthread_mutex_unlock(&ctx_impl->mutex);
 
-            cb->close_handler(req);
+    } else {
+        quit = 1;
+        ctx_impl->quit_param = NXT_QUIT_GRACEFUL;
+    }
 
-        } else {
-            nxt_unit_request_done(req, NXT_UNIT_ERROR);
+    if (quit) {
+        ctx_impl->online = 0;
+
+        if (cb->quit != NULL) {
+            cb->quit(ctx);
         }
 
-    } nxt_queue_loop;
+        nxt_queue_each(req_impl, &ctx_impl->active_req,
+                       nxt_unit_request_info_impl_t, link)
+        {
+            req = &req_impl->req;
 
-    if (ctx != &lib->main_ctx.ctx) {
+            nxt_unit_req_warn(req, "active request on ctx quit");
+
+            if (cb->close_handler) {
+                nxt_unit_req_debug(req, "close_handler");
+
+                cb->close_handler(req);
+
+            } else {
+                nxt_unit_request_done(req, NXT_UNIT_ERROR);
+            }
+
+        } nxt_queue_loop;
+
+        if (nxt_fast_path(ctx_impl->read_port != NULL)) {
+            nxt_unit_remove_port(lib, ctx, &ctx_impl->read_port->id);
+        }
+    }
+
+    if (ctx != &lib->main_ctx.ctx || skip_graceful_broadcast) {
         return;
     }
 
-    memset(&msg, 0, sizeof(nxt_port_msg_t));
+    memset(&m.msg, 0, sizeof(nxt_port_msg_t));
 
-    msg.pid = lib->pid;
-    msg.type = _NXT_PORT_MSG_QUIT;
+    m.msg.pid = lib->pid;
+    m.msg.type = _NXT_PORT_MSG_QUIT;
+    m.quit_param = quit_param;
 
     pthread_mutex_lock(&lib->mutex);
 
@@ -5775,7 +5885,7 @@ nxt_unit_quit(nxt_unit_ctx_t *ctx)
         }
 
         (void) nxt_unit_port_send(ctx, ctx_impl->read_port,
-                                  &msg, sizeof(msg), NULL, 0);
+                                  &m, sizeof(m), NULL, 0);
 
     } nxt_queue_loop;
 
@@ -6089,7 +6199,11 @@ nxt_unit_shared_port_recv(nxt_unit_ctx_t *ctx, nxt_unit_port_t *port,
 
 retry:
 
-    res = nxt_unit_app_queue_recv(port, rbuf);
+    res = nxt_unit_app_queue_recv(ctx, port, rbuf);
+
+    if (res == NXT_UNIT_OK) {
+        return NXT_UNIT_OK;
+    }
 
     if (res == NXT_UNIT_AGAIN) {
         res = nxt_unit_port_recv(ctx, port, rbuf);
@@ -6194,13 +6308,20 @@ nxt_unit_port_queue_recv(nxt_unit_port_t *port, nxt_unit_read_buf_t *rbuf)
 
 
 static int
-nxt_unit_app_queue_recv(nxt_unit_port_t *port, nxt_unit_read_buf_t *rbuf)
+nxt_unit_app_queue_recv(nxt_unit_ctx_t *ctx, nxt_unit_port_t *port,
+    nxt_unit_read_buf_t *rbuf)
 {
     uint32_t              cookie;
     nxt_port_msg_t        *port_msg;
     nxt_app_queue_t       *queue;
+    nxt_unit_impl_t       *lib;
     nxt_unit_port_impl_t  *port_impl;
 
+    struct {
+        nxt_port_msg_t    msg;
+        uint8_t           quit_param;
+    } nxt_packed m;
+
     port_impl = nxt_container_of(port, nxt_unit_port_impl_t, port);
     queue = port_impl->queue;
 
@@ -6214,6 +6335,25 @@ retry:
         port_msg = (nxt_port_msg_t *) rbuf->buf;
 
         if (nxt_app_queue_cancel(queue, cookie, port_msg->stream)) {
+            lib = nxt_container_of(ctx->unit, nxt_unit_impl_t, unit);
+
+            if (lib->request_limit != 0) {
+                nxt_atomic_fetch_add(&lib->request_count, 1);
+
+                if (nxt_slow_path(lib->request_count >= lib->request_limit)) {
+                    nxt_unit_debug(ctx, "request limit reached");
+
+                    memset(&m.msg, 0, sizeof(nxt_port_msg_t));
+
+                    m.msg.pid = lib->pid;
+                    m.msg.type = _NXT_PORT_MSG_QUIT;
+                    m.quit_param = NXT_QUIT_GRACEFUL;
+
+                    (void) nxt_unit_port_send(ctx, lib->main_ctx.read_port,
+                                              &m, sizeof(m), NULL, 0);
+                }
+            }
+
             return NXT_UNIT_OK;
         }
 
diff --git a/src/nxt_unit.h b/src/nxt_unit.h
index 1e1a8dbe..484b7d56 100644
--- a/src/nxt_unit.h
+++ b/src/nxt_unit.h
@@ -136,7 +136,8 @@ struct nxt_unit_callbacks_s {
     int      (*add_port)(nxt_unit_ctx_t *, nxt_unit_port_t *port);
 
     /* Remove previously added port. Optional. */
-    void     (*remove_port)(nxt_unit_t *, nxt_unit_port_t *port);
+    void     (*remove_port)(nxt_unit_t *, nxt_unit_ctx_t *,
+                            nxt_unit_port_t *port);
 
     /* Remove all data associated with process pid including ports. Optional. */
     void     (*remove_pid)(nxt_unit_t *, pid_t pid);
@@ -167,6 +168,7 @@ struct nxt_unit_init_s {
 
     uint32_t              request_data_size;
     uint32_t              shm_limit;
+    uint32_t              request_limit;
 
     nxt_unit_callbacks_t  callbacks;
 
@@ -215,8 +217,6 @@ int nxt_unit_run_shared(nxt_unit_ctx_t *ctx);
 
 nxt_unit_request_info_t *nxt_unit_dequeue_request(nxt_unit_ctx_t *ctx);
 
-int nxt_unit_is_main_ctx(nxt_unit_ctx_t *ctx);
-
 /*
  * Receive and process one message, invoke configured callbacks.
  *
diff --git a/src/perl/nxt_perl_psgi.c b/src/perl/nxt_perl_psgi.c
index 5df1465d..02555c96 100644
--- a/src/perl/nxt_perl_psgi.c
+++ b/src/perl/nxt_perl_psgi.c
@@ -1184,13 +1184,12 @@ nxt_perl_psgi_start(nxt_task_t *task, nxt_process_data_t *data)
         goto fail;
     }
 
-    nxt_unit_default_init(task, &perl_init);
+    nxt_unit_default_init(task, &perl_init, common_conf);
 
     perl_init.callbacks.request_handler = nxt_perl_psgi_request_handler;
     perl_init.callbacks.ready_handler = nxt_perl_psgi_ready_handler;
     perl_init.data = c;
     perl_init.ctx_data = &pctx;
-    perl_init.shm_limit = common_conf->shm_limit;
 
     unit_ctx = nxt_unit_init(&perl_init);
     if (nxt_slow_path(unit_ctx == NULL)) {
@@ -1292,11 +1291,6 @@ nxt_perl_psgi_ready_handler(nxt_unit_ctx_t *ctx)
     nxt_perl_app_conf_t  *c;
     nxt_perl_psgi_ctx_t  *pctx;
 
-    /* Worker thread context. */
-    if (!nxt_unit_is_main_ctx(ctx)) {
-        return NXT_UNIT_OK;
-    }
-
     c = ctx->unit->data;
 
     if (c->threads <= 1) {
diff --git a/src/python/nxt_python.c b/src/python/nxt_python.c
index abb04194..8687c869 100644
--- a/src/python/nxt_python.c
+++ b/src/python/nxt_python.c
@@ -230,10 +230,9 @@ nxt_python_start(nxt_task_t *task, nxt_process_data_t *data)
         }
     }
 
-    nxt_unit_default_init(task, &python_init);
+    nxt_unit_default_init(task, &python_init, data->app);
 
     python_init.data = c;
-    python_init.shm_limit = data->app->shm_limit;
     python_init.callbacks.ready_handler = nxt_python_ready_handler;
 
     proto = c->protocol;
@@ -522,18 +521,6 @@ nxt_python_ready_handler(nxt_unit_ctx_t *ctx)
     nxt_py_thread_info_t   *ti;
     nxt_python_app_conf_t  *c;
 
-    if (nxt_py_proto.ready != NULL) {
-        res = nxt_py_proto.ready(ctx);
-        if (nxt_slow_path(res != NXT_UNIT_OK)) {
-            return NXT_UNIT_ERROR;
-        }
-    }
-
-    /* Worker thread context. */
-    if (!nxt_unit_is_main_ctx(ctx)) {
-        return NXT_UNIT_OK;
-    }
-
     c = ctx->unit->data;
 
     if (c->threads <= 1) {
diff --git a/src/python/nxt_python.h b/src/python/nxt_python.h
index e4eac9dc..eddb1cfc 100644
--- a/src/python/nxt_python.h
+++ b/src/python/nxt_python.h
@@ -64,7 +64,6 @@ typedef struct {
     void  (*ctx_data_free)(void *data);
     int   (*startup)(void *data);
     int   (*run)(nxt_unit_ctx_t *ctx);
-    int   (*ready)(nxt_unit_ctx_t *ctx);
     void  (*done)(void);
 } nxt_python_proto_t;
 
diff --git a/src/python/nxt_python_asgi.c b/src/python/nxt_python_asgi.c
index 8bf43d94..354e3a81 100644
--- a/src/python/nxt_python_asgi.c
+++ b/src/python/nxt_python_asgi.c
@@ -33,11 +33,10 @@ static PyObject *nxt_py_asgi_create_address(nxt_unit_sptr_t *sptr, uint8_t len,
 static PyObject *nxt_py_asgi_create_header(nxt_unit_field_t *f);
 static PyObject *nxt_py_asgi_create_subprotocols(nxt_unit_field_t *f);
 
-static int nxt_python_asgi_ready(nxt_unit_ctx_t *ctx);
-
 static int nxt_py_asgi_add_port(nxt_unit_ctx_t *ctx, nxt_unit_port_t *port);
 static int nxt_py_asgi_add_reader(nxt_unit_ctx_t *ctx, nxt_unit_port_t *port);
-static void nxt_py_asgi_remove_port(nxt_unit_t *lib, nxt_unit_port_t *port);
+static void nxt_py_asgi_remove_port(nxt_unit_t *lib, nxt_unit_ctx_t *ctx,
+    nxt_unit_port_t *port);
 static void nxt_py_asgi_quit(nxt_unit_ctx_t *ctx);
 static void nxt_py_asgi_shm_ack_handler(nxt_unit_ctx_t *ctx);
 
@@ -45,7 +44,6 @@ static PyObject *nxt_py_asgi_port_read(PyObject *self, PyObject *args);
 static void nxt_python_asgi_done(void);
 
 static PyObject           *nxt_py_port_read;
-static nxt_unit_port_t    *nxt_py_shared_port;
 
 static PyMethodDef        nxt_py_port_read_method =
     {"unit_port_read", nxt_py_asgi_port_read, METH_VARARGS, ""};
@@ -55,7 +53,6 @@ static nxt_python_proto_t  nxt_py_asgi_proto = {
     .ctx_data_free  = nxt_python_asgi_ctx_data_free,
     .startup        = nxt_python_asgi_startup,
     .run            = nxt_python_asgi_run,
-    .ready          = nxt_python_asgi_ready,
     .done           = nxt_python_asgi_done,
 };
 
@@ -362,13 +359,6 @@ nxt_python_asgi_run(nxt_unit_ctx_t *ctx)
 
     Py_DECREF(res);
 
-    nxt_py_asgi_remove_reader(ctx, nxt_py_shared_port);
-    nxt_py_asgi_remove_reader(ctx, ctx_data->port);
-
-    if (ctx_data->port != NULL) {
-        ctx_data->port = NULL;
-    }
-
     nxt_py_asgi_lifespan_shutdown(ctx);
 
     return NXT_UNIT_OK;
@@ -892,27 +882,9 @@ fail:
 
 
 static int
-nxt_python_asgi_ready(nxt_unit_ctx_t *ctx)
-{
-    nxt_unit_port_t  *port;
-
-    if (nxt_slow_path(nxt_py_shared_port == NULL)) {
-        return NXT_UNIT_ERROR;
-    }
-
-    port = nxt_py_shared_port;
-
-    nxt_unit_debug(ctx, "asgi_ready %d %p %p", port->in_fd, ctx, port);
-
-    return nxt_py_asgi_add_reader(ctx, port);
-}
-
-
-static int
 nxt_py_asgi_add_port(nxt_unit_ctx_t *ctx, nxt_unit_port_t *port)
 {
-    int                     nb;
-    nxt_py_asgi_ctx_data_t  *ctx_data;
+    int  nb;
 
     if (port->in_fd == -1) {
         return NXT_UNIT_OK;
@@ -929,16 +901,6 @@ nxt_py_asgi_add_port(nxt_unit_ctx_t *ctx, nxt_unit_port_t *port)
 
     nxt_unit_debug(ctx, "asgi_add_port %d %p %p", port->in_fd, ctx, port);
 
-    if (port->id.id == NXT_UNIT_SHARED_PORT_ID) {
-        nxt_py_shared_port = port;
-
-        return NXT_UNIT_OK;
-    }
-
-    ctx_data = ctx->data;
-
-    ctx_data->port = port;
-
     return nxt_py_asgi_add_reader(ctx, port);
 }
 
@@ -1008,17 +970,16 @@ clean_fd:
 
 
 static void
-nxt_py_asgi_remove_port(nxt_unit_t *lib, nxt_unit_port_t *port)
+nxt_py_asgi_remove_port(nxt_unit_t *lib, nxt_unit_ctx_t *ctx,
+    nxt_unit_port_t *port)
 {
-    if (port->in_fd == -1) {
+    if (port->in_fd == -1 || ctx == NULL) {
         return;
     }
 
     nxt_unit_debug(NULL, "asgi_remove_port %d %p", port->in_fd, port);
 
-    if (nxt_py_shared_port == port) {
-        nxt_py_shared_port = NULL;
-    }
+    nxt_py_asgi_remove_reader(ctx, port);
 }
 
 
@@ -1032,27 +993,6 @@ nxt_py_asgi_quit(nxt_unit_ctx_t *ctx)
 
     ctx_data = ctx->data;
 
-    if (nxt_py_shared_port != NULL) {
-        p = PyLong_FromLong(nxt_py_shared_port->in_fd);
-        if (nxt_slow_path(p == NULL)) {
-            nxt_unit_alert(NULL, "Python failed to create Long");
-            nxt_python_print_exception();
-
-        } else {
-            res = PyObject_CallFunctionObjArgs(ctx_data->loop_remove_reader,
-                                               p, NULL);
-            if (nxt_slow_path(res == NULL)) {
-                nxt_unit_alert(NULL, "Python failed to remove_reader");
-                nxt_python_print_exception();
-
-            } else {
-                Py_DECREF(res);
-            }
-
-            Py_DECREF(p);
-        }
-    }
-
     p = PyLong_FromLong(0);
     if (nxt_slow_path(p == NULL)) {
         nxt_unit_alert(NULL, "Python failed to create Long");
diff --git a/src/python/nxt_python_asgi.h b/src/python/nxt_python_asgi.h
index 20702065..94478a36 100644
--- a/src/python/nxt_python_asgi.h
+++ b/src/python/nxt_python_asgi.h
@@ -34,7 +34,6 @@ typedef struct {
     PyObject         *quit_future;
     PyObject         *quit_future_set_result;
     PyObject         **target_lifespans;
-    nxt_unit_port_t  *port;
 } nxt_py_asgi_ctx_data_t;
 
 PyObject *nxt_py_asgi_enum_headers(PyObject *headers,
diff --git a/src/python/nxt_python_asgi_http.c b/src/python/nxt_python_asgi_http.c
index c4a77d53..05c0da4f 100644
--- a/src/python/nxt_python_asgi_http.c
+++ b/src/python/nxt_python_asgi_http.c
@@ -636,9 +636,11 @@ nxt_py_asgi_http_close_handler(nxt_unit_request_info_t *req)
 
     nxt_unit_req_debug(req, "asgi_http_close_handler");
 
-    http->closed = 1;
+    if (nxt_fast_path(http != NULL)) {
+        http->closed = 1;
 
-    nxt_py_asgi_http_emit_disconnect(http);
+        nxt_py_asgi_http_emit_disconnect(http);
+    }
 }
 
 
diff --git a/src/python/nxt_python_asgi_websocket.c b/src/python/nxt_python_asgi_websocket.c
index fc7d9fa4..ab1d0324 100644
--- a/src/python/nxt_python_asgi_websocket.c
+++ b/src/python/nxt_python_asgi_websocket.c
@@ -980,6 +980,10 @@ nxt_py_asgi_websocket_close_handler(nxt_unit_request_info_t *req)
 
     nxt_unit_req_debug(req, "asgi_websocket_close_handler");
 
+    if (nxt_slow_path(ws == NULL)) {
+        return;
+    }
+
     if (ws->receive_future == NULL) {
         ws->state = NXT_WS_DISCONNECTED;
 
diff --git a/src/ruby/nxt_ruby.c b/src/ruby/nxt_ruby.c
index 522869b5..62498127 100644
--- a/src/ruby/nxt_ruby.c
+++ b/src/ruby/nxt_ruby.c
@@ -357,11 +357,10 @@ nxt_ruby_start(nxt_task_t *task, nxt_process_data_t *data)
         goto fail;
     }
 
-    nxt_unit_default_init(task, &ruby_unit_init);
+    nxt_unit_default_init(task, &ruby_unit_init, conf);
 
     ruby_unit_init.callbacks.request_handler = nxt_ruby_request_handler;
     ruby_unit_init.callbacks.ready_handler = nxt_ruby_ready_handler;
-    ruby_unit_init.shm_limit = conf->shm_limit;
     ruby_unit_init.data = c;
     ruby_unit_init.ctx_data = &ruby_ctx;
 
@@ -1258,11 +1257,6 @@ nxt_ruby_ready_handler(nxt_unit_ctx_t *ctx)
     nxt_ruby_ctx_t       *rctx;
     nxt_ruby_app_conf_t  *c;
 
-    /* Worker thread context. */
-    if (!nxt_unit_is_main_ctx(ctx)) {
-        return NXT_UNIT_OK;
-    }
-
     c = ctx->unit->data;
 
     if (c->threads <= 1) {
diff --git a/src/test/nxt_unit_app_test.c b/src/test/nxt_unit_app_test.c
index a5f3728c..8fda9740 100644
--- a/src/test/nxt_unit_app_test.c
+++ b/src/test/nxt_unit_app_test.c
@@ -97,7 +97,7 @@ ready_handler(nxt_unit_ctx_t *ctx)
 
     nxt_unit_debug(ctx, "ready");
 
-    if (!nxt_unit_is_main_ctx(ctx) || thread_count <= 1) {
+    if (thread_count <= 1) {
         return NXT_UNIT_OK;
     }