17 files changed, 858 insertions, 401 deletions

diff --git a/src/nxt_application.c b/src/nxt_application.c
index 1b23eca3..4689f622 100644
--- a/src/nxt_application.c
+++ b/src/nxt_application.c
@@ -11,8 +11,22 @@
 #include <nxt_application.h>
 #include <nxt_master_process.h>
 
+#include <glob.h>
+
+
+typedef struct {
+    nxt_str_t   type;
+    nxt_str_t   version;
+    nxt_str_t   file;
+} nxt_module_t;
+
+
+static nxt_buf_t *nxt_discovery_modules(nxt_task_t *task, const char *path);
+static nxt_int_t nxt_discovery_module(nxt_task_t *task, nxt_mp_t *mp,
+    nxt_array_t *modules, const char *name);
+static nxt_app_module_t *nxt_app_module_load(nxt_task_t *task,
+    const char *name);
 
-nxt_application_module_t         *nxt_app_modules[NXT_APP_MAX];
 
 static nxt_thread_mutex_t        nxt_app_mutex;
 static nxt_thread_cond_t         nxt_app_cond;
@@ -22,14 +36,243 @@ static nxt_http_fields_hash_t        *nxt_app_request_fields_hash;
 
 static nxt_application_module_t      *nxt_app;
 
+
+nxt_int_t
+nxt_discovery_start(nxt_task_t *task, void *data)
+{
+    nxt_buf_t         *b;
+    nxt_port_t        *main_port;
+    nxt_runtime_t     *rt;
+
+    nxt_debug(task, "DISCOVERY");
+
+    b = nxt_discovery_modules(task, "build/nginext.*");
+
+    rt = task->thread->runtime;
+    main_port = rt->port_by_type[NXT_PROCESS_MASTER];
+
+    nxt_port_socket_write(task, main_port, NXT_PORT_MSG_MODULES, -1,
+                          0, -1, b);
+
+    return NXT_OK;
+}
+
+
+static void
+nxt_discovery_completion_handler(nxt_task_t *task, void *obj, void *data)
+{
+    nxt_mp_t   *mp;
+    nxt_buf_t  *b;
+
+    b = obj;
+    mp = b->data;
+
+    nxt_mp_destroy(mp);
+
+    exit(0);
+}
+
+
+static nxt_buf_t *
+nxt_discovery_modules(nxt_task_t *task, const char *path)
+{
+    char          *name;
+    u_char        *p, *end;
+    size_t        size;
+    glob_t        glb;
+    nxt_mp_t      *mp;
+    nxt_buf_t     *b;
+    nxt_int_t     ret;
+    nxt_uint_t    i, n;
+    nxt_array_t   *modules;
+    nxt_module_t  *module;
+
+    b = NULL;
+
+    mp = nxt_mp_create(1024, 128, 256, 32);
+    if (mp == NULL) {
+        return b;
+    }
+
+    ret = glob(path, 0, NULL, &glb);
+
+    if (ret == 0) {
+        n = glb.gl_pathc;
+
+        modules = nxt_array_create(mp, n, sizeof(nxt_module_t));
+        if (modules == NULL) {
+            goto fail;
+        }
+
+        for (i = 0; i < n; i++) {
+            name = glb.gl_pathv[i];
+
+            ret = nxt_discovery_module(task, mp, modules, name);
+            if (ret != NXT_OK) {
+                goto fail;
+            }
+        }
+
+        size = sizeof("[]") - 1;
+        module = modules->elts;
+        n = modules->nelts;
+
+        for (i = 0; i < n; i++) {
+            nxt_debug(task, "module: %V %V %V",
+                      &module[i].type, &module[i].version, &module[i].file);
+
+            size += sizeof("{\"type\": \"\",") - 1;
+            size += sizeof(" \"version\": \"\",") - 1;
+            size += sizeof(" \"file\": \"\"},") - 1;
+
+            size += module[i].type.length
+                    + module[i].version.length
+                    + module[i].file.length;
+        }
+
+        b = nxt_buf_mem_alloc(mp, size, 0);
+        if (b == NULL) {
+            goto fail;
+        }
+
+        b->completion_handler = nxt_discovery_completion_handler;
+
+        p = b->mem.free;
+        end = b->mem.end;
+        *p++ = '[';
+
+        for (i = 0; i < n; i++) {
+            p = nxt_sprintf(p, end,
+                  "{\"type\": \"%V\", \"version\": \"%V\", \"file\": \"%V\"},",
+                  &module[i].type, &module[i].version, &module[i].file);
+        }
+
+        *p++ = ']';
+        b->mem.free = p;
+    }
+
+fail:
+
+    globfree(&glb);
+
+    return b;
+}
+
+
+static nxt_int_t
+nxt_discovery_module(nxt_task_t *task, nxt_mp_t *mp, nxt_array_t *modules,
+    const char *name)
+{
+    void                      *dl;
+    nxt_str_t                 *s;
+    nxt_int_t                 ret;
+    nxt_uint_t                i, n;
+    nxt_module_t              *module;
+    nxt_application_module_t  *app;
+
+    /*
+     * Only memory allocation failure should return NXT_ERROR.
+     * Any module processing errors are ignored.
+     */
+    ret = NXT_ERROR;
+
+    dl = dlopen(name, RTLD_GLOBAL | RTLD_NOW);
+
+    if (dl == NULL) {
+        nxt_log(task, NXT_LOG_CRIT, "dlopen(\"%s\"), failed: \"%s\"",
+                name, dlerror());
+        return NXT_OK;
+    }
+
+    app = dlsym(dl, "nxt_app_module");
+
+    if (app != NULL) {
+        nxt_log(task, NXT_LOG_NOTICE, "module: %V \"%s\"",
+                &app->version, name);
+
+        module = modules->elts;
+        n = modules->nelts;
+
+        for (i = 0; i < n; i++) {
+            if (nxt_strstr_eq(&app->version, &module[i].version)) {
+                nxt_log(task, NXT_LOG_NOTICE,
+                        "ignoring %s module with the same "
+                        "application language version %V as in %s",
+                        name, &module[i].version, &module[i].file);
+
+                goto done;
+            }
+        }
+
+        module = nxt_array_add(modules);
+        if (module == NULL) {
+            goto fail;
+        }
+
+        s = nxt_str_dup(mp, &module->type, &app->type);
+        if (s == NULL) {
+            goto fail;
+        }
+
+        s = nxt_str_dup(mp, &module->version, &app->version);
+        if (s == NULL) {
+            goto fail;
+        }
+
+        module->file.length = nxt_strlen(name);
+
+        module->file.start = nxt_mp_alloc(mp, module->file.length);
+        if (module->file.start == NULL) {
+            goto fail;
+        }
+
+        nxt_memcpy(module->file.start, name, module->file.length);
+
+    } else {
+        nxt_log(task, NXT_LOG_CRIT, "dlsym(\"%s\"), failed: \"%s\"",
+                name, dlerror());
+    }
+
+done:
+
+    ret = NXT_OK;
+
+fail:
+
+    if (dlclose(dl) != 0) {
+        nxt_log(task, NXT_LOG_CRIT, "dlclose(\"%s\"), failed: \"%s\"",
+                name, dlerror());
+    }
+
+    return ret;
+}
+
+
 nxt_int_t
 nxt_app_start(nxt_task_t *task, void *data)
 {
-    nxt_int_t             ret;
-    nxt_common_app_conf_t *app_conf;
+    nxt_int_t              ret;
+    nxt_app_lang_module_t  *lang;
+    nxt_common_app_conf_t  *app_conf;
 
     app_conf = data;
 
+    lang = nxt_app_lang_module(task->thread->runtime, &app_conf->type);
+    if (nxt_slow_path(lang == NULL)) {
+        nxt_log(task, NXT_LOG_CRIT, "unknown application type: \"%V\"",
+                &app_conf->type);
+        return NXT_ERROR;
+    }
+
+    nxt_app = lang->module;
+
+    if (nxt_app == NULL) {
+        nxt_debug(task, "application language module: %V \"%s\"",
+                  &lang->version, lang->file);
+
+        nxt_app = nxt_app_module_load(task, lang->file);
+    }
+
     if (nxt_slow_path(nxt_thread_mutex_create(&nxt_app_mutex) != NXT_OK)) {
         return NXT_ERROR;
     }
@@ -38,8 +281,6 @@ nxt_app_start(nxt_task_t *task, void *data)
         return NXT_ERROR;
     }
 
-    nxt_app = nxt_app_modules[app_conf->type_id];
-
     ret = nxt_app->init(task, data);
 
     if (nxt_slow_path(ret != NXT_OK)) {
@@ -53,6 +294,24 @@ nxt_app_start(nxt_task_t *task, void *data)
 }
 
 
+static nxt_app_module_t *
+nxt_app_module_load(nxt_task_t *task, const char *name)
+{
+    void  *dl;
+
+    dl = dlopen(name, RTLD_GLOBAL | RTLD_LAZY);
+
+    if (dl != NULL) {
+        return dlsym(dl, "nxt_app_module");
+    }
+
+    nxt_log(task, NXT_LOG_CRIT, "dlopen(\"%s\"), failed: \"%s\"",
+            name, dlerror());
+
+    return NULL;
+}
+
+
 nxt_int_t
 nxt_app_http_init(nxt_task_t *task, nxt_runtime_t *rt)
 {
@@ -681,30 +940,56 @@ nxt_app_msg_write_raw(nxt_task_t *task, nxt_app_wmsg_t *msg, const u_char *c,
 }
 
 
+nxt_app_lang_module_t *
+nxt_app_lang_module(nxt_runtime_t *rt, nxt_str_t *name)
+{
+    u_char                 *p, *end, *version;
+    size_t                 type_length, version_length;
+    nxt_uint_t             i, n;
+    nxt_app_lang_module_t  *lang;
+
+    end = name->start + name->length;
+    version = end;
+
+    for (p = name->start; p < end; p++) {
+        if (*p == ' ') {
+            version = p + 1;
+            break;
+        }
+
+        if (*p >= '0' && *p <= '9') {
+            version = p;
+            break;
+        }
+    }
+
+    type_length = p - name->start;
+    version_length = end - version;
+
+    lang = rt->languages->elts;
+    n = rt->languages->nelts;
+
+    for (i = 0; i < n; i++) {
+        if (nxt_str_eq(&lang[i].type, name->start, type_length)
+            && nxt_str_start(&lang[i].version, version, version_length))
+        {
+            return &lang[i];
+        }
+    }
+
+    return NULL;
+}
+
+
 nxt_app_type_t
 nxt_app_parse_type(nxt_str_t *str)
 {
     if (nxt_str_eq(str, "python", 6)) {
         return NXT_APP_PYTHON;
 
-    } else if (nxt_str_eq(str, "python2", 7)) {
-        return NXT_APP_PYTHON2;
-
-    } else if (nxt_str_eq(str, "python3", 7)) {
-        return NXT_APP_PYTHON3;
-
     } else if (nxt_str_eq(str, "php", 3)) {
         return NXT_APP_PHP;
 
-    } else if (nxt_str_eq(str, "php5", 4)) {
-        return NXT_APP_PHP5;
-
-    } else if (nxt_str_eq(str, "php7", 4)) {
-        return NXT_APP_PHP7;
-
-    } else if (nxt_str_eq(str, "ruby", 4)) {
-        return NXT_APP_RUBY;
-
     } else if (nxt_str_eq(str, "go", 2)) {
         return NXT_APP_GO;
 
diff --git a/src/nxt_application.h b/src/nxt_application.h
index 9efb5008..c8d9998d 100644
--- a/src/nxt_application.h
+++ b/src/nxt_application.h
@@ -10,20 +10,26 @@
 
 
 typedef enum {
-    NXT_APP_UNKNOWN = 0,
     NXT_APP_PYTHON,
-    NXT_APP_PYTHON2,
-    NXT_APP_PYTHON3,
     NXT_APP_PHP,
-    NXT_APP_PHP5,
-    NXT_APP_PHP7,
-    NXT_APP_RUBY,
     NXT_APP_GO,
 
-    NXT_APP_MAX,
+    NXT_APP_UNKNOWN,
 } nxt_app_type_t;
 
 
+typedef struct nxt_app_module_s  nxt_application_module_t;
+typedef struct nxt_app_module_s  nxt_app_module_t;
+
+
+typedef struct {
+    nxt_str_t                 type;
+    nxt_str_t                 version;
+    char                      *file;
+    nxt_application_module_t  *module;
+} nxt_app_lang_module_t;
+
+
 typedef struct nxt_common_app_conf_s nxt_common_app_conf_t;
 
 
@@ -48,7 +54,6 @@ typedef struct {
 struct nxt_common_app_conf_s {
     nxt_str_t       name;
     nxt_str_t       type;
-    nxt_app_type_t  type_id;
     nxt_str_t       user;
     nxt_str_t       group;
 
@@ -148,13 +153,13 @@ nxt_inline u_char *
 nxt_app_msg_write_length(u_char *dst, size_t length);
 
 /* TODO asynchronous mmap buffer assignment */
-u_char *nxt_app_msg_write_get_buf(nxt_task_t *task, nxt_app_wmsg_t *msg,
-    size_t size);
+NXT_EXPORT u_char *nxt_app_msg_write_get_buf(nxt_task_t *task,
+    nxt_app_wmsg_t *msg, size_t size);
 
-nxt_int_t nxt_app_msg_write(nxt_task_t *task, nxt_app_wmsg_t *msg,
+NXT_EXPORT nxt_int_t nxt_app_msg_write(nxt_task_t *task, nxt_app_wmsg_t *msg,
     u_char *c, size_t size);
 
-nxt_int_t nxt_app_msg_write_prefixed_upcase(nxt_task_t *task,
+NXT_EXPORT nxt_int_t nxt_app_msg_write_prefixed_upcase(nxt_task_t *task,
     nxt_app_wmsg_t *msg, const nxt_str_t *prefix, const nxt_str_t *v);
 
 nxt_inline nxt_int_t
@@ -178,44 +183,37 @@ nxt_app_msg_write_nvp_(nxt_task_t *task, nxt_app_wmsg_t *msg,
 nxt_inline nxt_int_t nxt_app_msg_write_size(nxt_task_t *task,
     nxt_app_wmsg_t *msg, size_t size);
 
-nxt_int_t nxt_app_msg_flush(nxt_task_t *task, nxt_app_wmsg_t *msg,
+NXT_EXPORT nxt_int_t nxt_app_msg_flush(nxt_task_t *task, nxt_app_wmsg_t *msg,
     nxt_bool_t last);
 
-nxt_int_t nxt_app_msg_write_raw(nxt_task_t *task, nxt_app_wmsg_t *msg,
-    const u_char *c, size_t size);
+NXT_EXPORT nxt_int_t nxt_app_msg_write_raw(nxt_task_t *task,
+    nxt_app_wmsg_t *msg, const u_char *c, size_t size);
 
-nxt_int_t nxt_app_msg_read_str(nxt_task_t *task, nxt_app_rmsg_t *msg,
+NXT_EXPORT nxt_int_t nxt_app_msg_read_str(nxt_task_t *task, nxt_app_rmsg_t *msg,
     nxt_str_t *str);
 
-size_t nxt_app_msg_read_raw(nxt_task_t *task, nxt_app_rmsg_t *msg, void *buf,
-    size_t size);
+NXT_EXPORT size_t nxt_app_msg_read_raw(nxt_task_t *task,
+    nxt_app_rmsg_t *msg, void *buf, size_t size);
 
-nxt_int_t nxt_app_msg_read_nvp(nxt_task_t *task, nxt_app_rmsg_t *rmsg,
-    nxt_str_t *n, nxt_str_t *v);
+NXT_EXPORT nxt_int_t nxt_app_msg_read_nvp(nxt_task_t *task,
+    nxt_app_rmsg_t *rmsg, nxt_str_t *n, nxt_str_t *v);
 
-nxt_int_t nxt_app_msg_read_size(nxt_task_t *task, nxt_app_rmsg_t *rmsg,
-    size_t *size);
+NXT_EXPORT nxt_int_t nxt_app_msg_read_size(nxt_task_t *task,
+    nxt_app_rmsg_t *rmsg, size_t *size);
 
 
-typedef struct nxt_app_module_s  nxt_application_module_t;
-typedef struct nxt_app_module_s  nxt_app_module_t;
-
 struct nxt_app_module_s {
+    nxt_str_t                  type;
+    nxt_str_t                  version;
+
     nxt_int_t                  (*init)(nxt_task_t *task,
                                     nxt_common_app_conf_t *conf);
-    nxt_int_t                  (*prepare_msg)(nxt_task_t *task,
-                                    nxt_app_request_t *r,
-                                    nxt_app_wmsg_t *wmsg);
     nxt_int_t                  (*run)(nxt_task_t *task,
                                     nxt_app_rmsg_t *rmsg,
                                     nxt_app_wmsg_t *wmsg);
 };
 
 
-extern nxt_application_module_t  *nxt_app_modules[NXT_APP_MAX];
-
-
-
 nxt_int_t nxt_app_http_read_body(nxt_app_request_t *r, u_char *data,
     size_t len);
 nxt_int_t nxt_app_write(nxt_app_request_t *r, const u_char *data, size_t len);
@@ -290,6 +288,11 @@ nxt_app_msg_read_length(u_char *src, size_t *length)
 }
 
 
+nxt_app_lang_module_t *nxt_app_lang_module(nxt_runtime_t *rt, nxt_str_t *name);
 nxt_app_type_t nxt_app_parse_type(nxt_str_t *str);
 
+
+extern nxt_application_module_t  nxt_go_module;
+
+
 #endif /* _NXT_APPLICATION_H_INCLIDED_ */
diff --git a/src/nxt_conf_validation.c b/src/nxt_conf_validation.c
index 0608eaa9..5cc2569f 100644
--- a/src/nxt_conf_validation.c
+++ b/src/nxt_conf_validation.c
@@ -6,6 +6,7 @@
 
 #include <nxt_main.h>
 #include <nxt_conf.h>
+#include <nxt_application.h>
 
 
 typedef struct {
@@ -213,11 +214,20 @@ static nxt_int_t
 nxt_conf_vldt_app(nxt_conf_value_t *conf, nxt_str_t *name,
     nxt_conf_value_t *value)
 {
-    nxt_str_t         type;
-    nxt_conf_value_t  *type_value;
+    nxt_str_t              type;
+    nxt_uint_t             n;
+    nxt_thread_t           *thread;
+    nxt_conf_value_t       *type_value;
+    nxt_app_lang_module_t  *lang;
 
     static nxt_str_t  type_str = nxt_string("type");
 
+    static void  *members[] = {
+        nxt_conf_vldt_python_members,
+        nxt_conf_vldt_php_members,
+        nxt_conf_vldt_go_members,
+    };
+
     type_value = nxt_conf_get_object_member(value, &type_str, NULL);
 
     if (nxt_slow_path(type_value == NULL)) {
@@ -230,16 +240,16 @@ nxt_conf_vldt_app(nxt_conf_value_t *conf, nxt_str_t *name,
 
     nxt_conf_get_string(type_value, &type);
 
-    if (nxt_str_eq(&type, "python", 6)) {
-        return nxt_conf_vldt_object(conf, value, nxt_conf_vldt_python_members);
-    }
+    thread = nxt_thread();
 
-    if (nxt_str_eq(&type, "php", 3)) {
-        return nxt_conf_vldt_object(conf, value, nxt_conf_vldt_php_members);
+    lang = nxt_app_lang_module(thread->runtime, &type);
+    if (lang == NULL) {
+        return NXT_ERROR;
     }
 
-    if (nxt_str_eq(&type, "go", 2)) {
-        return nxt_conf_vldt_object(conf, value, nxt_conf_vldt_go_members);
+    n = nxt_app_parse_type(&lang->type);
+    if (n != NXT_APP_UNKNOWN) {
+        return nxt_conf_vldt_object(conf, value, members[n]);
     }
 
     return NXT_ERROR;
diff --git a/src/nxt_go.c b/src/nxt_go.c
index b821cced..ee446921 100644
--- a/src/nxt_go.c
+++ b/src/nxt_go.c
@@ -10,30 +10,17 @@
 
 static nxt_int_t nxt_go_init(nxt_task_t *task, nxt_common_app_conf_t *conf);
 
-static nxt_int_t nxt_go_prepare_msg(nxt_task_t *task,
-                      nxt_app_request_t *r, nxt_app_wmsg_t *msg);
-
 static nxt_int_t nxt_go_run(nxt_task_t *task,
                       nxt_app_rmsg_t *rmsg, nxt_app_wmsg_t *msg);
 
 nxt_application_module_t  nxt_go_module = {
+    nxt_string("go"),
+    nxt_string("go"),
     nxt_go_init,
-    nxt_go_prepare_msg,
-    nxt_go_run
+    nxt_go_run,
 };
 
 
-nxt_int_t
-nxt_go_module_init(nxt_thread_t *thr, nxt_runtime_t *rt);
-
-nxt_int_t
-nxt_go_module_init(nxt_thread_t *thr, nxt_runtime_t *rt)
-{
-    nxt_app_modules[NXT_APP_GO] = &nxt_go_module;
-
-    return NXT_OK;
-}
-
 extern char  **environ;
 
 nxt_inline int
@@ -113,82 +100,6 @@ nxt_go_init(nxt_task_t *task, nxt_common_app_conf_t *conf)
 
 
 static nxt_int_t
-nxt_go_prepare_msg(nxt_task_t *task, nxt_app_request_t *r, nxt_app_wmsg_t *wmsg)
-{
-    nxt_int_t                 rc;
-    nxt_buf_t                 *b;
-    nxt_http_field_t          *field;
-    nxt_app_request_header_t  *h;
-
-    static const nxt_str_t eof = nxt_null_string;
-
-    h = &r->header;
-
-#define RC(S)                                                                 \
-    do {                                                                      \
-        rc = (S);                                                             \
-        if (nxt_slow_path(rc != NXT_OK)) {                                    \
-            goto fail;                                                        \
-        }                                                                     \
-    } while(0)
-
-#define NXT_WRITE(N)                                                          \
-    RC(nxt_app_msg_write_str(task, wmsg, N))
-
-    /* TODO error handle, async mmap buffer assignment */
-
-    NXT_WRITE(&h->method);
-    NXT_WRITE(&h->target);
-    if (h->path.start == h->target.start) {
-        NXT_WRITE(&eof);
-    } else {
-        NXT_WRITE(&h->path);
-    }
-
-    if (h->query.start != NULL) {
-        RC(nxt_app_msg_write_size(task, wmsg,
-                                  h->query.start - h->target.start + 1));
-    } else {
-        RC(nxt_app_msg_write_size(task, wmsg, 0));
-    }
-
-    NXT_WRITE(&h->version);
-
-    NXT_WRITE(&h->host);
-    NXT_WRITE(&h->cookie);
-    NXT_WRITE(&h->content_type);
-    NXT_WRITE(&h->content_length);
-
-    RC(nxt_app_msg_write_size(task, wmsg, h->parsed_content_length));
-
-    nxt_list_each(field, h->fields) {
-        NXT_WRITE(&field->name);
-        NXT_WRITE(&field->value);
-
-    } nxt_list_loop;
-
-    /* end-of-headers mark */
-    NXT_WRITE(&eof);
-
-    RC(nxt_app_msg_write_size(task, wmsg, r->body.preread_size));
-
-    for(b = r->body.buf; b != NULL; b = b->next) {
-        RC(nxt_app_msg_write_raw(task, wmsg, b->mem.pos,
-                                 nxt_buf_mem_used_size(&b->mem)));
-    }
-
-#undef NXT_WRITE
-#undef RC
-
-    return NXT_OK;
-
-fail:
-
-    return NXT_ERROR;
-}
-
-
-static nxt_int_t
 nxt_go_run(nxt_task_t *task,
            nxt_app_rmsg_t *rmsg, nxt_app_wmsg_t *msg)
 {
diff --git a/src/nxt_master_process.c b/src/nxt_master_process.c
index 3e72ce85..8a4f8564 100644
--- a/src/nxt_master_process.c
+++ b/src/nxt_master_process.c
@@ -27,6 +27,8 @@ static nxt_int_t nxt_master_start_controller_process(nxt_task_t *task,
     nxt_runtime_t *rt);
 static nxt_int_t nxt_master_start_router_process(nxt_task_t *task,
     nxt_runtime_t *rt);
+static nxt_int_t nxt_master_start_discovery_process(nxt_task_t *task,
+    nxt_runtime_t *rt);
 static nxt_int_t nxt_master_start_worker_process(nxt_task_t *task,
     nxt_runtime_t *rt, nxt_common_app_conf_t *app_conf, uint32_t stream);
 static nxt_int_t nxt_master_create_worker_process(nxt_task_t *task,
@@ -44,6 +46,9 @@ static void nxt_master_port_socket_handler(nxt_task_t *task,
     nxt_port_recv_msg_t *msg);
 static nxt_int_t nxt_master_listening_socket(nxt_sockaddr_t *sa,
     nxt_listening_socket_t *ls);
+static void nxt_master_port_modules_handler(nxt_task_t *task,
+    nxt_port_recv_msg_t *msg);
+static int nxt_cdecl nxt_app_lang_compare(const void *v1, const void *v2);
 
 
 const nxt_sig_event_t  nxt_master_process_signals[] = {
@@ -63,8 +68,6 @@ nxt_int_t
 nxt_master_process_start(nxt_thread_t *thr, nxt_task_t *task,
     nxt_runtime_t *rt)
 {
-    nxt_int_t  ret;
-
     rt->types |= (1U << NXT_PROCESS_MASTER);
 
     if (nxt_master_process_port_create(task, rt) != NXT_OK) {
@@ -73,12 +76,12 @@ nxt_master_process_start(nxt_thread_t *thr, nxt_task_t *task,
 
     nxt_master_process_title(task);
 
-    ret = nxt_master_start_controller_process(task, rt);
-    if (ret != NXT_OK) {
-        return ret;
-    }
-
-    return nxt_master_start_router_process(task, rt);
+    /*
+     * The dicsovery process will send a message processed by
+     * nxt_master_port_modules_handler() which starts the controller
+     * and router processes.
+     */
+    return nxt_master_start_discovery_process(task, rt);
 }
 
 
@@ -197,8 +200,6 @@ nxt_port_master_start_worker_handler(nxt_task_t *task, nxt_port_recv_msg_t *msg)
         return;
     }
 
-    app_conf.type_id = nxt_app_parse_type(&app_conf.type);
-
     ret = nxt_master_start_worker_process(task, task->thread->runtime,
                                           &app_conf, msg->port_msg.stream);
 
@@ -216,6 +217,7 @@ static nxt_port_handler_t  nxt_master_process_port_handlers[] = {
     nxt_port_ready_handler,
     nxt_port_master_start_worker_handler,
     nxt_master_port_socket_handler,
+    nxt_master_port_modules_handler,
     nxt_port_rpc_handler,
     nxt_port_rpc_handler,
 };
@@ -289,7 +291,7 @@ nxt_master_start_controller_process(nxt_task_t *task, nxt_runtime_t *rt)
 {
     nxt_process_init_t  *init;
 
-    init = nxt_mp_get(rt->mem_pool, sizeof(nxt_process_init_t));
+    init = nxt_malloc(sizeof(nxt_process_init_t));
     if (nxt_slow_path(init == NULL)) {
         return NXT_ERROR;
     }
@@ -309,11 +311,35 @@ nxt_master_start_controller_process(nxt_task_t *task, nxt_runtime_t *rt)
 
 
 static nxt_int_t
+nxt_master_start_discovery_process(nxt_task_t *task, nxt_runtime_t *rt)
+{
+    nxt_process_init_t  *init;
+
+    init = nxt_malloc(sizeof(nxt_process_init_t));
+    if (nxt_slow_path(init == NULL)) {
+        return NXT_ERROR;
+    }
+
+    init->start = nxt_discovery_start;
+    init->name = "discovery";
+    init->user_cred = &rt->user_cred;
+    init->port_handlers = nxt_discovery_process_port_handlers;
+    init->signals = nxt_worker_process_signals;
+    init->type = NXT_PROCESS_DISCOVERY;
+    init->data = rt;
+    init->stream = 0;
+    init->restart = 0;
+
+    return nxt_master_create_worker_process(task, rt, init);
+}
+
+
+static nxt_int_t
 nxt_master_start_router_process(nxt_task_t *task, nxt_runtime_t *rt)
 {
     nxt_process_init_t  *init;
 
-    init = nxt_mp_get(rt->mem_pool, sizeof(nxt_process_init_t));
+    init = nxt_malloc(sizeof(nxt_process_init_t));
     if (nxt_slow_path(init == NULL)) {
         return NXT_ERROR;
     }
@@ -885,3 +911,130 @@ fail:
 
     return NXT_ERROR;
 }
+
+
+static nxt_conf_map_t  nxt_app_lang_module_map[] = {
+    {
+        nxt_string("type"),
+        NXT_CONF_MAP_STR_COPY,
+        offsetof(nxt_app_lang_module_t, type),
+    },
+
+    {
+        nxt_string("version"),
+        NXT_CONF_MAP_STR_COPY,
+        offsetof(nxt_app_lang_module_t, version),
+    },
+
+    {
+        nxt_string("file"),
+        NXT_CONF_MAP_CSTRZ,
+        offsetof(nxt_app_lang_module_t, file),
+    },
+};
+
+
+static void
+nxt_master_port_modules_handler(nxt_task_t *task, nxt_port_recv_msg_t *msg)
+{
+    uint32_t               index;
+    nxt_mp_t               *mp;
+    nxt_int_t              ret;
+    nxt_buf_t              *b;
+    nxt_runtime_t          *rt;
+    nxt_conf_value_t       *conf, *root, *value;
+    nxt_app_lang_module_t  *lang;
+
+    static nxt_str_t   root_path = nxt_string("/");
+
+    rt = task->thread->runtime;
+
+    if (msg->port_msg.pid != rt->port_by_type[NXT_PROCESS_DISCOVERY]->pid) {
+        return;
+    }
+
+    b = msg->buf;
+
+    if (b == NULL) {
+        return;
+    }
+
+    nxt_debug(task, "application languages: \"%*s\"",
+              b->mem.free - b->mem.pos, b->mem.pos);
+
+    mp = nxt_mp_create(1024, 128, 256, 32);
+    if (mp == NULL) {
+        return;
+    }
+
+    conf = nxt_conf_json_parse(mp, b->mem.pos, b->mem.free, NULL);
+    if (conf == NULL) {
+        goto fail;
+    }
+
+    root = nxt_conf_get_path(conf, &root_path);
+    if (root == NULL) {
+        goto fail;
+    }
+
+    for (index = 0; /* void */ ; index++) {
+        value = nxt_conf_get_array_element(root, index);
+        if (value == NULL) {
+            break;
+        }
+
+        lang = nxt_array_add(rt->languages);
+        if (lang == NULL) {
+            goto fail;
+        }
+
+        lang->module = NULL;
+
+        ret = nxt_conf_map_object(rt->mem_pool, value, nxt_app_lang_module_map,
+                                  nxt_nitems(nxt_app_lang_module_map), lang);
+
+        if (ret != NXT_OK) {
+            goto fail;
+        }
+
+        nxt_debug(task, "lang %V %V \"%s\"",
+                  &lang->type, &lang->version, lang->file);
+    }
+
+    qsort(rt->languages->elts, rt->languages->nelts,
+          sizeof(nxt_app_lang_module_t), nxt_app_lang_compare);
+
+fail:
+
+    nxt_mp_destroy(mp);
+
+    ret = nxt_master_start_controller_process(task, rt);
+
+    if (ret == NXT_OK) {
+        (void) nxt_master_start_router_process(task, rt);
+    }
+}
+
+
+static int nxt_cdecl
+nxt_app_lang_compare(const void *v1, const void *v2)
+{
+    int                          n;
+    size_t                       length;
+    const nxt_app_lang_module_t  *lang1, *lang2;
+
+    lang1 = v1;
+    lang2 = v2;
+
+    length = nxt_min(lang1->version.length, lang2->version.length);
+
+    n = nxt_strncmp(lang1->version.start, lang2->version.start, length);
+
+    if (n == 0) {
+        n = lang1->version.length - lang2->version.length;
+    }
+
+    /* Negate result to move higher versions to the beginning. */
+
+    return -n;
+}
diff --git a/src/nxt_master_process.h b/src/nxt_master_process.h
index 3a7e4988..be591c76 100644
--- a/src/nxt_master_process.h
+++ b/src/nxt_master_process.h
@@ -25,10 +25,12 @@ void nxt_master_stop_worker_processes(nxt_task_t *task, nxt_runtime_t *runtime);
 
 nxt_int_t nxt_controller_start(nxt_task_t *task, void *data);
 nxt_int_t nxt_router_start(nxt_task_t *task, void *data);
+nxt_int_t nxt_discovery_start(nxt_task_t *task, void *data);
 nxt_int_t nxt_app_start(nxt_task_t *task, void *data);
 
 extern nxt_port_handler_t  nxt_controller_process_port_handlers[];
 extern nxt_port_handler_t  nxt_worker_process_port_handlers[];
+extern nxt_port_handler_t  nxt_discovery_process_port_handlers[];
 extern nxt_port_handler_t  nxt_app_process_port_handlers[];
 extern nxt_port_handler_t  nxt_router_process_port_handlers[];
 extern const nxt_sig_event_t  nxt_master_process_signals[];
diff --git a/src/nxt_php_sapi.c b/src/nxt_php_sapi.c
index 4f8f4696..1e1f4087 100644
--- a/src/nxt_php_sapi.c
+++ b/src/nxt_php_sapi.c
@@ -16,9 +16,6 @@
 
 static nxt_int_t nxt_php_init(nxt_task_t *task, nxt_common_app_conf_t *conf);
 
-static nxt_int_t nxt_php_prepare_msg(nxt_task_t *task,
-                      nxt_app_request_t *r, nxt_app_wmsg_t *wmsg);
-
 static nxt_int_t nxt_php_run(nxt_task_t *task,
                       nxt_app_rmsg_t *rmsg, nxt_app_wmsg_t *wmsg);
 
@@ -58,8 +55,6 @@ static int nxt_php_read_post(char *buffer, uint count_bytes TSRMLS_DC);
 
 static void nxt_php_flush(void *server_context);
 
-extern nxt_int_t nxt_php_sapi_init(nxt_thread_t *thr, nxt_runtime_t *rt);
-
 
 static sapi_module_struct  nxt_php_sapi_module =
 {
@@ -173,30 +168,14 @@ nxt_php_str_trim_lead(nxt_str_t *str, u_char t)
 }
 
 
-nxt_application_module_t  nxt_php_module = {
+NXT_EXPORT nxt_application_module_t  nxt_app_module = {
+    nxt_string("php"),
+    nxt_string(PHP_VERSION),
     nxt_php_init,
-    nxt_php_prepare_msg,
-    nxt_php_run
+    nxt_php_run,
 };
 
 
-nxt_int_t
-nxt_php_sapi_init(nxt_thread_t *thr, nxt_runtime_t *rt)
-{
-    nxt_app_modules[NXT_APP_PHP] = &nxt_php_module;
-
-#if PHP_MAJOR_VERSION == 5
-    nxt_app_modules[NXT_APP_PHP5] = &nxt_php_module;
-#endif
-
-#if PHP_MAJOR_VERSION == 7
-    nxt_app_modules[NXT_APP_PHP7] = &nxt_php_module;
-#endif
-
-    return NXT_OK;
-}
-
-
 static nxt_int_t
 nxt_php_init(nxt_task_t *task, nxt_common_app_conf_t *conf)
 {
@@ -357,92 +336,6 @@ fail:
 
 
 static nxt_int_t
-nxt_php_prepare_msg(nxt_task_t *task, nxt_app_request_t *r,
-    nxt_app_wmsg_t *wmsg)
-{
-    nxt_int_t                 rc;
-    nxt_buf_t                 *b;
-    nxt_http_field_t          *field;
-    nxt_app_request_header_t  *h;
-
-    static const nxt_str_t prefix = nxt_string("HTTP_");
-    static const nxt_str_t eof = nxt_null_string;
-
-    h = &r->header;
-
-#define RC(S)                                                                 \
-    do {                                                                      \
-        rc = (S);                                                             \
-        if (nxt_slow_path(rc != NXT_OK)) {                                    \
-            goto fail;                                                        \
-        }                                                                     \
-    } while(0)
-
-#define NXT_WRITE(N)                                                          \
-    RC(nxt_app_msg_write_str(task, wmsg, N))
-
-    /* TODO error handle, async mmap buffer assignment */
-
-    NXT_WRITE(&h->method);
-    NXT_WRITE(&h->target);
-    if (h->path.start == h->target.start) {
-        NXT_WRITE(&eof);
-    } else {
-        NXT_WRITE(&h->path);
-    }
-
-    if (h->query.start != NULL) {
-        RC(nxt_app_msg_write_size(task, wmsg,
-                                  h->query.start - h->target.start + 1));
-    } else {
-        RC(nxt_app_msg_write_size(task, wmsg, 0));
-    }
-
-    NXT_WRITE(&h->version);
-
-    // PHP_SELF
-    // SCRIPT_NAME
-    // SCRIPT_FILENAME
-    // DOCUMENT_ROOT
-
-    NXT_WRITE(&r->remote);
-
-    NXT_WRITE(&h->host);
-    NXT_WRITE(&h->cookie);
-    NXT_WRITE(&h->content_type);
-    NXT_WRITE(&h->content_length);
-
-    RC(nxt_app_msg_write_size(task, wmsg, h->parsed_content_length));
-
-    nxt_list_each(field, h->fields) {
-        RC(nxt_app_msg_write_prefixed_upcase(task, wmsg,
-                                             &prefix, &field->name));
-        NXT_WRITE(&field->value);
-
-    } nxt_list_loop;
-
-    /* end-of-headers mark */
-    NXT_WRITE(&eof);
-
-    RC(nxt_app_msg_write_size(task, wmsg, r->body.preread_size));
-
-    for(b = r->body.buf; b != NULL; b = b->next) {
-        RC(nxt_app_msg_write_raw(task, wmsg, b->mem.pos,
-                                 nxt_buf_mem_used_size(&b->mem)));
-    }
-
-#undef NXT_WRITE
-#undef RC
-
-    return NXT_OK;
-
-fail:
-
-    return NXT_ERROR;
-}
-
-
-static nxt_int_t
 nxt_php_run(nxt_task_t *task,
     nxt_app_rmsg_t *rmsg, nxt_app_wmsg_t *wmsg)
 {
diff --git a/src/nxt_port.h b/src/nxt_port.h
index 3f584e9f..78228ff7 100644
--- a/src/nxt_port.h
+++ b/src/nxt_port.h
@@ -24,6 +24,7 @@ typedef enum {
     _NXT_PORT_MSG_READY,
     _NXT_PORT_MSG_START_WORKER,
     _NXT_PORT_MSG_SOCKET,
+    _NXT_PORT_MSG_MODULES,
     _NXT_PORT_MSG_RPC_READY,
     _NXT_PORT_MSG_RPC_ERROR,
 
@@ -41,6 +42,7 @@ typedef enum {
     NXT_PORT_MSG_START_WORKER   = _NXT_PORT_MSG_START_WORKER |
                                   NXT_PORT_MSG_LAST,
     NXT_PORT_MSG_SOCKET         = _NXT_PORT_MSG_SOCKET | NXT_PORT_MSG_LAST,
+    NXT_PORT_MSG_MODULES        = _NXT_PORT_MSG_MODULES | NXT_PORT_MSG_LAST,
     NXT_PORT_MSG_RPC_READY      = _NXT_PORT_MSG_RPC_READY,
     NXT_PORT_MSG_RPC_READY_LAST = _NXT_PORT_MSG_RPC_READY | NXT_PORT_MSG_LAST,
     NXT_PORT_MSG_RPC_ERROR      = _NXT_PORT_MSG_RPC_ERROR | NXT_PORT_MSG_LAST,
diff --git a/src/nxt_process.h b/src/nxt_process.h
index b76c4f1a..8f33b4af 100644
--- a/src/nxt_process.h
+++ b/src/nxt_process.h
@@ -14,6 +14,7 @@ typedef enum {
     NXT_PROCESS_CONTROLLER,
     NXT_PROCESS_ROUTER,
     NXT_PROCESS_WORKER,
+    NXT_PROCESS_DISCOVERY,
 
     NXT_PROCESS_MAX,
 } nxt_process_type_t;
diff --git a/src/nxt_python_wsgi.c b/src/nxt_python_wsgi.c
index f1bd170f..f5c3ebae 100644
--- a/src/nxt_python_wsgi.c
+++ b/src/nxt_python_wsgi.c
@@ -61,9 +61,6 @@ typedef struct nxt_python_run_ctx_s nxt_python_run_ctx_t;
 
 static nxt_int_t nxt_python_init(nxt_task_t *task, nxt_common_app_conf_t *conf);
 
-static nxt_int_t nxt_python_prepare_msg(nxt_task_t *task,
-                      nxt_app_request_t *r, nxt_app_wmsg_t *msg);
-
 static nxt_int_t nxt_python_run(nxt_task_t *task,
                       nxt_app_rmsg_t *rmsg, nxt_app_wmsg_t *msg);
 
@@ -93,13 +90,12 @@ nxt_inline nxt_int_t nxt_python_write(nxt_python_run_ctx_t *ctx,
 nxt_inline nxt_int_t nxt_python_write_py_str(nxt_python_run_ctx_t *ctx,
                       PyObject *str, nxt_bool_t flush, nxt_bool_t last);
 
-extern nxt_int_t nxt_python_wsgi_init(nxt_thread_t *thr, nxt_runtime_t *rt);
-
 
-nxt_application_module_t  nxt_python_module = {
+NXT_EXPORT nxt_application_module_t  nxt_app_module = {
+    nxt_string("python"),
+    nxt_string(PY_VERSION),
     nxt_python_init,
-    nxt_python_prepare_msg,
-    nxt_python_run
+    nxt_python_run,
 };
 
 
@@ -177,23 +173,6 @@ static PyObject           *nxt_py_environ_ptyp;
 static nxt_python_run_ctx_t  *nxt_python_run_ctx;
 
 
-nxt_int_t
-nxt_python_wsgi_init(nxt_thread_t *thr, nxt_runtime_t *rt)
-{
-    nxt_app_modules[NXT_APP_PYTHON] = &nxt_python_module;
-
-#if PY_MAJOR_VERSION == 2
-    nxt_app_modules[NXT_APP_PYTHON2] = &nxt_python_module;
-#endif
-
-#if PY_MAJOR_VERSION == 3
-    nxt_app_modules[NXT_APP_PYTHON3] = &nxt_python_module;
-#endif
-
-    return NXT_OK;
-}
-
-
 static nxt_int_t
 nxt_python_init(nxt_task_t *task, nxt_common_app_conf_t *conf)
 {
@@ -320,84 +299,6 @@ fail:
 
 
 static nxt_int_t
-nxt_python_prepare_msg(nxt_task_t *task, nxt_app_request_t *r,
-    nxt_app_wmsg_t *wmsg)
-{
-    nxt_int_t                 rc;
-    nxt_buf_t                 *b;
-    nxt_http_field_t          *field;
-    nxt_app_request_header_t  *h;
-
-    static const nxt_str_t prefix = nxt_string("HTTP_");
-    static const nxt_str_t eof = nxt_null_string;
-
-    h = &r->header;
-
-#define RC(S)                                                                 \
-    do {                                                                      \
-        rc = (S);                                                             \
-        if (nxt_slow_path(rc != NXT_OK)) {                                    \
-            goto fail;                                                        \
-        }                                                                     \
-    } while(0)
-
-#define NXT_WRITE(N)                                                          \
-    RC(nxt_app_msg_write_str(task, wmsg, N))
-
-    /* TODO error handle, async mmap buffer assignment */
-
-    NXT_WRITE(&h->method);
-    NXT_WRITE(&h->target);
-    if (h->path.start == h->target.start) {
-        NXT_WRITE(&eof);
-    } else {
-        NXT_WRITE(&h->path);
-    }
-
-    if (h->query.start != NULL) {
-        RC(nxt_app_msg_write_size(task, wmsg,
-                                  h->query.start - h->target.start + 1));
-    } else {
-        RC(nxt_app_msg_write_size(task, wmsg, 0));
-    }
-
-    NXT_WRITE(&h->version);
-
-    NXT_WRITE(&r->remote);
-
-    NXT_WRITE(&h->host);
-    NXT_WRITE(&h->content_type);
-    NXT_WRITE(&h->content_length);
-
-    nxt_list_each(field, h->fields) {
-        RC(nxt_app_msg_write_prefixed_upcase(task, wmsg,
-                                             &prefix, &field->name));
-        NXT_WRITE(&field->value);
-
-    } nxt_list_loop;
-
-    /* end-of-headers mark */
-    NXT_WRITE(&eof);
-
-    RC(nxt_app_msg_write_size(task, wmsg, r->body.preread_size));
-
-    for(b = r->body.buf; b != NULL; b = b->next) {
-        RC(nxt_app_msg_write_raw(task, wmsg, b->mem.pos,
-                                 nxt_buf_mem_used_size(&b->mem)));
-    }
-
-#undef NXT_WRITE
-#undef RC
-
-    return NXT_OK;
-
-fail:
-
-    return NXT_ERROR;
-}
-
-
-static nxt_int_t
 nxt_python_run(nxt_task_t *task, nxt_app_rmsg_t *rmsg, nxt_app_wmsg_t *wmsg)
 {
     u_char    *buf;
diff --git a/src/nxt_router.c b/src/nxt_router.c
index 5a053278..8ddddb46 100644
--- a/src/nxt_router.c
+++ b/src/nxt_router.c
@@ -134,6 +134,12 @@ static void nxt_router_process_http_request(nxt_task_t *task,
     nxt_conn_t *c, nxt_app_parse_ctx_t *ap);
 static void nxt_router_process_http_request_mp(nxt_task_t *task,
     nxt_req_app_link_t *ra, nxt_port_t *port);
+static nxt_int_t nxt_python_prepare_msg(nxt_task_t *task, nxt_app_request_t *r,
+    nxt_app_wmsg_t *wmsg);
+static nxt_int_t nxt_php_prepare_msg(nxt_task_t *task, nxt_app_request_t *r,
+    nxt_app_wmsg_t *wmsg);
+static nxt_int_t nxt_go_prepare_msg(nxt_task_t *task, nxt_app_request_t *r,
+    nxt_app_wmsg_t *wmsg);
 static void nxt_router_conn_ready(nxt_task_t *task, void *obj, void *data);
 static void nxt_router_conn_close(nxt_task_t *task, void *obj, void *data);
 static void nxt_router_conn_free(nxt_task_t *task, void *obj, void *data);
@@ -146,6 +152,14 @@ static void nxt_router_gen_error(nxt_task_t *task, nxt_conn_t *c, int code,
 
 static nxt_router_t  *nxt_router;
 
+
+static nxt_app_prepare_msg_t  nxt_app_prepare_msg[] = {
+    nxt_python_prepare_msg,
+    nxt_php_prepare_msg,
+    nxt_go_prepare_msg,
+};
+
+
 nxt_int_t
 nxt_router_start(nxt_task_t *task, void *data)
 {
@@ -654,6 +668,7 @@ nxt_router_conf_create(nxt_task_t *task, nxt_router_temp_conf_t *tmcf,
     nxt_conf_value_t            *applications, *application;
     nxt_conf_value_t            *listeners, *listener;
     nxt_socket_conf_t           *skcf;
+    nxt_app_lang_module_t       *lang;
     nxt_router_app_conf_t       apcf;
     nxt_router_listener_conf_t  lscf;
 
@@ -735,17 +750,27 @@ 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 workers: %D", apcf.workers);
 
-        type = nxt_app_parse_type(&apcf.type);
+        lang = nxt_app_lang_module(task->thread->runtime, &apcf.type);
 
-        if (type == NXT_APP_UNKNOWN) {
+        if (lang == NULL) {
             nxt_log(task, NXT_LOG_CRIT, "unknown application type: \"%V\"",
                     &apcf.type);
             goto app_fail;
         }
 
-        if (nxt_app_modules[type] == NULL) {
+        nxt_debug(task, "application language module: \"%s\"", lang->file);
+
+        type = nxt_app_parse_type(&lang->type);
+
+        if (type == NXT_APP_UNKNOWN) {
+            nxt_log(task, NXT_LOG_CRIT, "unknown application type: \"%V\"",
+                    &lang->type);
+            goto app_fail;
+        }
+
+        if (nxt_app_prepare_msg[type] == NULL) {
             nxt_log(task, NXT_LOG_CRIT, "unsupported application type: \"%V\"",
-                    &apcf.type);
+                    &lang->type);
             goto app_fail;
         }
 
@@ -763,7 +788,7 @@ nxt_router_conf_create(nxt_task_t *task, nxt_router_temp_conf_t *tmcf,
         app->type = type;
         app->max_workers = apcf.workers;
         app->live = 1;
-        app->module = nxt_app_modules[type];
+        app->prepare_msg = nxt_app_prepare_msg[type];
 
         nxt_queue_insert_tail(&tmcf->apps, &app->link);
     }
@@ -2687,7 +2712,7 @@ nxt_router_process_http_request_mp(nxt_task_t *task, nxt_req_app_link_t *ra,
     wmsg.buf = &wmsg.write;
     wmsg.stream = ra->req_id;
 
-    res = port->app->module->prepare_msg(task, &ap->r, &wmsg);
+    res = port->app->prepare_msg(task, &ap->r, &wmsg);
 
     if (nxt_slow_path(res != NXT_OK)) {
         nxt_router_gen_error(task, c, 500,
@@ -2710,6 +2735,246 @@ nxt_router_process_http_request_mp(nxt_task_t *task, nxt_req_app_link_t *ra,
 }
 
 
+static nxt_int_t
+nxt_python_prepare_msg(nxt_task_t *task, nxt_app_request_t *r,
+    nxt_app_wmsg_t *wmsg)
+{
+    nxt_int_t                 rc;
+    nxt_buf_t                 *b;
+    nxt_http_field_t          *field;
+    nxt_app_request_header_t  *h;
+
+    static const nxt_str_t prefix = nxt_string("HTTP_");
+    static const nxt_str_t eof = nxt_null_string;
+
+    h = &r->header;
+
+#define RC(S)                                                                 \
+    do {                                                                      \
+        rc = (S);                                                             \
+        if (nxt_slow_path(rc != NXT_OK)) {                                    \
+            goto fail;                                                        \
+        }                                                                     \
+    } while(0)
+
+#define NXT_WRITE(N)                                                          \
+    RC(nxt_app_msg_write_str(task, wmsg, N))
+
+    /* TODO error handle, async mmap buffer assignment */
+
+    NXT_WRITE(&h->method);
+    NXT_WRITE(&h->target);
+    if (h->path.start == h->target.start) {
+        NXT_WRITE(&eof);
+    } else {
+        NXT_WRITE(&h->path);
+    }
+
+    if (h->query.start != NULL) {
+        RC(nxt_app_msg_write_size(task, wmsg,
+                                  h->query.start - h->target.start + 1));
+    } else {
+        RC(nxt_app_msg_write_size(task, wmsg, 0));
+    }
+
+    NXT_WRITE(&h->version);
+
+    NXT_WRITE(&r->remote);
+
+    NXT_WRITE(&h->host);
+    NXT_WRITE(&h->content_type);
+    NXT_WRITE(&h->content_length);
+
+    nxt_list_each(field, h->fields) {
+        RC(nxt_app_msg_write_prefixed_upcase(task, wmsg,
+                                             &prefix, &field->name));
+        NXT_WRITE(&field->value);
+
+    } nxt_list_loop;
+
+    /* end-of-headers mark */
+    NXT_WRITE(&eof);
+
+    RC(nxt_app_msg_write_size(task, wmsg, r->body.preread_size));
+
+    for(b = r->body.buf; b != NULL; b = b->next) {
+        RC(nxt_app_msg_write_raw(task, wmsg, b->mem.pos,
+                                 nxt_buf_mem_used_size(&b->mem)));
+    }
+
+#undef NXT_WRITE
+#undef RC
+
+    return NXT_OK;
+
+fail:
+
+    return NXT_ERROR;
+}
+
+
+static nxt_int_t
+nxt_php_prepare_msg(nxt_task_t *task, nxt_app_request_t *r,
+    nxt_app_wmsg_t *wmsg)
+{
+    nxt_int_t                 rc;
+    nxt_buf_t                 *b;
+    nxt_http_field_t          *field;
+    nxt_app_request_header_t  *h;
+
+    static const nxt_str_t prefix = nxt_string("HTTP_");
+    static const nxt_str_t eof = nxt_null_string;
+
+    h = &r->header;
+
+#define RC(S)                                                                 \
+    do {                                                                      \
+        rc = (S);                                                             \
+        if (nxt_slow_path(rc != NXT_OK)) {                                    \
+            goto fail;                                                        \
+        }                                                                     \
+    } while(0)
+
+#define NXT_WRITE(N)                                                          \
+    RC(nxt_app_msg_write_str(task, wmsg, N))
+
+    /* TODO error handle, async mmap buffer assignment */
+
+    NXT_WRITE(&h->method);
+    NXT_WRITE(&h->target);
+    if (h->path.start == h->target.start) {
+        NXT_WRITE(&eof);
+    } else {
+        NXT_WRITE(&h->path);
+    }
+
+    if (h->query.start != NULL) {
+        RC(nxt_app_msg_write_size(task, wmsg,
+                                  h->query.start - h->target.start + 1));
+    } else {
+        RC(nxt_app_msg_write_size(task, wmsg, 0));
+    }
+
+    NXT_WRITE(&h->version);
+
+    // PHP_SELF
+    // SCRIPT_NAME
+    // SCRIPT_FILENAME
+    // DOCUMENT_ROOT
+
+    NXT_WRITE(&r->remote);
+
+    NXT_WRITE(&h->host);
+    NXT_WRITE(&h->cookie);
+    NXT_WRITE(&h->content_type);
+    NXT_WRITE(&h->content_length);
+
+    RC(nxt_app_msg_write_size(task, wmsg, h->parsed_content_length));
+
+    nxt_list_each(field, h->fields) {
+        RC(nxt_app_msg_write_prefixed_upcase(task, wmsg,
+                                             &prefix, &field->name));
+        NXT_WRITE(&field->value);
+
+    } nxt_list_loop;
+
+    /* end-of-headers mark */
+    NXT_WRITE(&eof);
+
+    RC(nxt_app_msg_write_size(task, wmsg, r->body.preread_size));
+
+    for(b = r->body.buf; b != NULL; b = b->next) {
+        RC(nxt_app_msg_write_raw(task, wmsg, b->mem.pos,
+                                 nxt_buf_mem_used_size(&b->mem)));
+    }
+
+#undef NXT_WRITE
+#undef RC
+
+    return NXT_OK;
+
+fail:
+
+    return NXT_ERROR;
+}
+
+
+static nxt_int_t
+nxt_go_prepare_msg(nxt_task_t *task, nxt_app_request_t *r, nxt_app_wmsg_t *wmsg)
+{
+    nxt_int_t                 rc;
+    nxt_buf_t                 *b;
+    nxt_http_field_t          *field;
+    nxt_app_request_header_t  *h;
+
+    static const nxt_str_t eof = nxt_null_string;
+
+    h = &r->header;
+
+#define RC(S)                                                                 \
+    do {                                                                      \
+        rc = (S);                                                             \
+        if (nxt_slow_path(rc != NXT_OK)) {                                    \
+            goto fail;                                                        \
+        }                                                                     \
+    } while(0)
+
+#define NXT_WRITE(N)                                                          \
+    RC(nxt_app_msg_write_str(task, wmsg, N))
+
+    /* TODO error handle, async mmap buffer assignment */
+
+    NXT_WRITE(&h->method);
+    NXT_WRITE(&h->target);
+    if (h->path.start == h->target.start) {
+        NXT_WRITE(&eof);
+    } else {
+        NXT_WRITE(&h->path);
+    }
+
+    if (h->query.start != NULL) {
+        RC(nxt_app_msg_write_size(task, wmsg,
+                                  h->query.start - h->target.start + 1));
+    } else {
+        RC(nxt_app_msg_write_size(task, wmsg, 0));
+    }
+
+    NXT_WRITE(&h->version);
+
+    NXT_WRITE(&h->host);
+    NXT_WRITE(&h->cookie);
+    NXT_WRITE(&h->content_type);
+    NXT_WRITE(&h->content_length);
+
+    RC(nxt_app_msg_write_size(task, wmsg, h->parsed_content_length));
+
+    nxt_list_each(field, h->fields) {
+        NXT_WRITE(&field->name);
+        NXT_WRITE(&field->value);
+
+    } nxt_list_loop;
+
+    /* end-of-headers mark */
+    NXT_WRITE(&eof);
+
+    RC(nxt_app_msg_write_size(task, wmsg, r->body.preread_size));
+
+    for(b = r->body.buf; b != NULL; b = b->next) {
+        RC(nxt_app_msg_write_raw(task, wmsg, b->mem.pos,
+                                 nxt_buf_mem_used_size(&b->mem)));
+    }
+
+#undef NXT_WRITE
+#undef RC
+
+    return NXT_OK;
+
+fail:
+
+    return NXT_ERROR;
+}
+
+
 static const nxt_conn_state_t  nxt_router_conn_close_state
     nxt_aligned(64) =
 {
diff --git a/src/nxt_router.h b/src/nxt_router.h
index 2a8a30e1..6e44f1d8 100644
--- a/src/nxt_router.h
+++ b/src/nxt_router.h
@@ -66,6 +66,11 @@ typedef struct {
 } nxt_joint_job_t;
 
 
+
+typedef nxt_int_t (*nxt_app_prepare_msg_t)(nxt_task_t *task,
+    nxt_app_request_t *r, nxt_app_wmsg_t *wmsg);
+
+
 struct nxt_app_s {
     nxt_thread_mutex_t     mutex;    /* Protects ports queue. */
     nxt_queue_t            ports;    /* of nxt_port_t.app_link */
@@ -83,7 +88,7 @@ struct nxt_app_s {
     nxt_queue_link_t       link;
 
     nxt_str_t              conf;
-    nxt_app_module_t       *module;
+    nxt_app_prepare_msg_t  prepare_msg;
 };
 
 
diff --git a/src/nxt_runtime.c b/src/nxt_runtime.c
index 30474ce8..5e67ecfd 100644
--- a/src/nxt_runtime.c
+++ b/src/nxt_runtime.c
@@ -57,10 +57,11 @@ static nxt_process_t *nxt_runtime_process_remove_pid(nxt_runtime_t *rt,
 nxt_int_t
 nxt_runtime_create(nxt_task_t *task)
 {
-    nxt_mp_t       *mp;
-    nxt_int_t      ret;
-    nxt_array_t    *listen_sockets;
-    nxt_runtime_t  *rt;
+    nxt_mp_t               *mp;
+    nxt_int_t              ret;
+    nxt_array_t            *listen_sockets;
+    nxt_runtime_t          *rt;
+    nxt_app_lang_module_t  *lang;
 
     mp = nxt_mp_create(1024, 128, 256, 32);
 
@@ -90,6 +91,18 @@ nxt_runtime_create(nxt_task_t *task)
         goto fail;
     }
 
+    rt->languages = nxt_array_create(mp, 1, sizeof(nxt_app_lang_module_t));
+    if (nxt_slow_path(rt->languages == NULL)) {
+        goto fail;
+    }
+
+    /* Should not fail. */
+    lang = nxt_array_add(rt->languages);
+    lang->type = (nxt_str_t) nxt_string("go");
+    lang->version = (nxt_str_t) nxt_null_string;
+    lang->file = NULL;
+    lang->module = &nxt_go_module;
+
     listen_sockets = nxt_array_create(mp, 1, sizeof(nxt_listen_socket_t));
     if (nxt_slow_path(listen_sockets == NULL)) {
         goto fail;
@@ -324,7 +337,6 @@ nxt_runtime_thread_pools(nxt_thread_t *thr, nxt_runtime_t *rt)
 static void
 nxt_runtime_start(nxt_task_t *task, void *obj, void *data)
 {
-    nxt_uint_t     i;
     nxt_runtime_t  *rt;
 
     rt = obj;
@@ -338,12 +350,6 @@ nxt_runtime_start(nxt_task_t *task, void *obj, void *data)
         goto fail;
     }
 
-    for (i = 0; i < nxt_init_modules_n; i++) {
-        if (nxt_init_modules[i](task->thread, rt) != NXT_OK) {
-            goto fail;
-        }
-    }
-
     if (nxt_runtime_log_files_create(task, rt) != NXT_OK) {
         goto fail;
     }
diff --git a/src/nxt_runtime.h b/src/nxt_runtime.h
index 7922c2ef..4961bfb8 100644
--- a/src/nxt_runtime.h
+++ b/src/nxt_runtime.h
@@ -19,6 +19,7 @@ struct nxt_runtime_s {
     nxt_array_t            *listen_sockets;     /* of nxt_listen_socket_t */
 
     nxt_array_t            *services;           /* of nxt_service_t */
+    nxt_array_t            *languages;          /* of nxt_app_lang_module_t */
     void                   *data;
 
     nxt_runtime_cont_t     start;
diff --git a/src/nxt_string.c b/src/nxt_string.c
index 90e5734d..4690851c 100644
--- a/src/nxt_string.c
+++ b/src/nxt_string.c
@@ -64,8 +64,7 @@ nxt_str_dup(nxt_mp_t *mp, nxt_str_t *dst, const nxt_str_t *src)
  * nxt_str_cstrz() creates a C style zero-terminated copy of a source
  * nxt_str_t.  The function is intended to create strings suitable
  * for libc and kernel interfaces so result is pointer to char instead
- * of u_char to minimize casts.  The copy is aligned to 2 bytes thus
- * the lowest bit may be used as marker.
+ * of u_char to minimize casts.
  */
 
 char *
@@ -73,7 +72,7 @@ nxt_str_cstrz(nxt_mp_t *mp, const nxt_str_t *src)
 {
     char  *p, *dst;
 
-    dst = nxt_mp_align(mp, 2, src->length + 1);
+    dst = nxt_mp_alloc(mp, src->length + 1);
 
     if (nxt_fast_path(dst != NULL)) {
         p = nxt_cpymem(dst, src->start, src->length);
diff --git a/src/nxt_string.h b/src/nxt_string.h
index e5611e35..56dc18d7 100644
--- a/src/nxt_string.h
+++ b/src/nxt_string.h
@@ -158,7 +158,7 @@ nxt_str_eq(s, p, _length)                                                     \
 
 #define                                                                       \
 nxt_str_start(s, p, _length)                                                  \
-    (((s)->length > _length) && (nxt_memcmp((s)->start, p, _length) == 0))
+    (((s)->length >= _length) && (nxt_memcmp((s)->start, p, _length) == 0))
 
 
 #define                                                                       \
diff --git a/src/nxt_worker_process.c b/src/nxt_worker_process.c
index bd6674d5..59290d0b 100644
--- a/src/nxt_worker_process.c
+++ b/src/nxt_worker_process.c
@@ -32,6 +32,7 @@ nxt_port_handler_t  nxt_controller_process_port_handlers[] = {
     NULL, /* NXT_PORT_MSG_READY        */
     NULL, /* NXT_PORT_MSG_START_WORKER */
     NULL, /* NXT_PORT_MSG_SOCKET       */
+    NULL, /* NXT_PORT_MSG_MODULES      */
     nxt_port_rpc_handler,
     nxt_port_rpc_handler,
 };
@@ -47,6 +48,7 @@ nxt_port_handler_t  nxt_worker_process_port_handlers[] = {
     NULL, /* NXT_PORT_MSG_READY        */
     NULL, /* NXT_PORT_MSG_START_WORKER */
     NULL, /* NXT_PORT_MSG_SOCKET       */
+    NULL, /* NXT_PORT_MSG_MODULES      */
     nxt_port_rpc_handler,
     nxt_port_rpc_handler,
 };
@@ -62,6 +64,7 @@ nxt_port_handler_t  nxt_app_process_port_handlers[] = {
     NULL, /* NXT_PORT_MSG_READY        */
     NULL, /* NXT_PORT_MSG_START_WORKER */
     NULL, /* NXT_PORT_MSG_SOCKET       */
+    NULL, /* NXT_PORT_MSG_MODULES      */
     nxt_port_rpc_handler,
     nxt_port_rpc_handler,
 };
@@ -77,6 +80,23 @@ nxt_port_handler_t  nxt_router_process_port_handlers[] = {
     NULL, /* NXT_PORT_MSG_READY        */
     NULL, /* NXT_PORT_MSG_START_WORKER */
     NULL, /* NXT_PORT_MSG_SOCKET       */
+    NULL, /* NXT_PORT_MSG_MODULES      */
+    nxt_port_rpc_handler,
+    nxt_port_rpc_handler,
+};
+
+
+nxt_port_handler_t  nxt_discovery_process_port_handlers[] = {
+    nxt_worker_process_quit_handler,
+    nxt_port_new_port_handler,
+    nxt_port_change_log_file_handler,
+    nxt_port_mmap_handler,
+    nxt_port_data_handler,
+    nxt_port_remove_pid_handler,
+    NULL, /* NXT_PORT_MSG_READY        */
+    NULL, /* NXT_PORT_MSG_START_WORKER */
+    NULL, /* NXT_PORT_MSG_SOCKET       */
+    NULL, /* NXT_PORT_MSG_MODULES      */
     nxt_port_rpc_handler,
     nxt_port_rpc_handler,
 };