Round robin upstream added.

11 files changed, 654 insertions, 34 deletions

diff --git a/auto/sources b/auto/sources
index 98e4a1f4..2283e543 100644
--- a/auto/sources
+++ b/auto/sources
@@ -69,6 +69,7 @@ NXT_LIB_SRCS=" \
     src/nxt_job_resolve.c \
     src/nxt_sockaddr.c \
     src/nxt_listen_socket.c \
+    src/nxt_upstream.c \
     src/nxt_upstream_round_robin.c \
     src/nxt_http_parse.c \
     src/nxt_app_log.c \
diff --git a/src/nxt_conf_validation.c b/src/nxt_conf_validation.c
index 8189cd44..86c1dbcb 100644
--- a/src/nxt_conf_validation.c
+++ b/src/nxt_conf_validation.c
@@ -110,6 +110,12 @@ static nxt_int_t nxt_conf_vldt_java_classpath(nxt_conf_validation_t *vldt,
     nxt_conf_value_t *value);
 static nxt_int_t nxt_conf_vldt_java_option(nxt_conf_validation_t *vldt,
     nxt_conf_value_t *value);
+static nxt_int_t nxt_conf_vldt_upstream(nxt_conf_validation_t *vldt,
+     nxt_str_t *name, nxt_conf_value_t *value);
+static nxt_int_t nxt_conf_vldt_server(nxt_conf_validation_t *vldt,
+    nxt_str_t *name, nxt_conf_value_t *value);
+static nxt_int_t nxt_conf_vldt_server_weight(nxt_conf_validation_t *vldt,
+    nxt_conf_value_t *value, void *data);
 
 static nxt_int_t nxt_conf_vldt_isolation(nxt_conf_validation_t *vldt,
     nxt_conf_value_t *value, void *data);
@@ -226,6 +232,11 @@ static nxt_conf_vldt_object_t  nxt_conf_vldt_root_members[] = {
       &nxt_conf_vldt_object_iterator,
       (void *) &nxt_conf_vldt_app },
 
+    { nxt_string("upstreams"),
+      NXT_CONF_VLDT_OBJECT,
+      &nxt_conf_vldt_object_iterator,
+      (void *) &nxt_conf_vldt_upstream },
+
     { nxt_string("access_log"),
       NXT_CONF_VLDT_STRING,
       NULL,
@@ -682,6 +693,26 @@ static nxt_conf_vldt_object_t  nxt_conf_vldt_java_members[] = {
 };
 
 
+static nxt_conf_vldt_object_t  nxt_conf_vldt_upstream_members[] = {
+    { nxt_string("servers"),
+      NXT_CONF_VLDT_OBJECT,
+      &nxt_conf_vldt_object_iterator,
+      (void *) &nxt_conf_vldt_server },
+
+    NXT_CONF_VLDT_END
+};
+
+
+static nxt_conf_vldt_object_t  nxt_conf_vldt_upstream_server_members[] = {
+    { nxt_string("weight"),
+      NXT_CONF_VLDT_INTEGER,
+      &nxt_conf_vldt_server_weight,
+      NULL },
+
+    NXT_CONF_VLDT_END
+};
+
+
 nxt_int_t
 nxt_conf_validate(nxt_conf_validation_t *vldt)
 {
@@ -1017,6 +1048,27 @@ nxt_conf_vldt_pass(nxt_conf_validation_t *vldt, nxt_conf_value_t *value,
         return NXT_OK;
     }
 
+    if (nxt_str_eq(&first, "upstreams", 9)) {
+
+        if (second.length == 0) {
+            goto error;
+        }
+
+        value = nxt_conf_get_object_member(vldt->conf, &first, NULL);
+
+        if (nxt_slow_path(value == NULL)) {
+            goto error;
+        }
+
+        value = nxt_conf_get_object_member(value, &second, NULL);
+
+        if (nxt_slow_path(value == NULL)) {
+            goto error;
+        }
+
+        return NXT_OK;
+    }
+
     if (nxt_str_eq(&first, "routes", 6)) {
         value = nxt_conf_get_object_member(vldt->conf, &first, NULL);
 
@@ -1901,3 +1953,81 @@ nxt_conf_vldt_java_option(nxt_conf_validation_t *vldt, nxt_conf_value_t *value)
 
     return NXT_OK;
 }
+
+
+static nxt_int_t
+nxt_conf_vldt_upstream(nxt_conf_validation_t *vldt, nxt_str_t *name,
+    nxt_conf_value_t *value)
+{
+    nxt_int_t         ret;
+    nxt_conf_value_t  *conf;
+
+    static nxt_str_t  servers = nxt_string("servers");
+
+    ret = nxt_conf_vldt_type(vldt, name, value, NXT_CONF_VLDT_OBJECT);
+
+    if (ret != NXT_OK) {
+        return ret;
+    }
+
+    ret = nxt_conf_vldt_object(vldt, value, nxt_conf_vldt_upstream_members);
+
+    if (ret != NXT_OK) {
+        return ret;
+    }
+
+    conf = nxt_conf_get_object_member(value, &servers, NULL);
+    if (conf == NULL) {
+        return nxt_conf_vldt_error(vldt, "The \"%V\" upstream must contain "
+                                   "\"servers\" object value.", name);
+    }
+
+    return NXT_OK;
+}
+
+
+static nxt_int_t
+nxt_conf_vldt_server(nxt_conf_validation_t *vldt, nxt_str_t *name,
+    nxt_conf_value_t *value)
+{
+    nxt_int_t       ret;
+    nxt_sockaddr_t  *sa;
+
+    ret = nxt_conf_vldt_type(vldt, name, value, NXT_CONF_VLDT_OBJECT);
+
+    if (ret != NXT_OK) {
+        return ret;
+    }
+
+    sa = nxt_sockaddr_parse(vldt->pool, name);
+
+    if (sa == NULL) {
+        return nxt_conf_vldt_error(vldt, "The \"%V\" is not valid "
+                                   "server address.", name);
+    }
+
+    return nxt_conf_vldt_object(vldt, value,
+                                nxt_conf_vldt_upstream_server_members);
+}
+
+
+static nxt_int_t
+nxt_conf_vldt_server_weight(nxt_conf_validation_t *vldt,
+    nxt_conf_value_t *value, void *data)
+{
+    int64_t  int_value;
+
+    int_value = nxt_conf_get_integer(value);
+
+    if (int_value <= 0) {
+        return nxt_conf_vldt_error(vldt, "The \"weight\" number must be "
+                                   "greater than 0.");
+    }
+
+    if (int_value > NXT_INT32_T_MAX) {
+        return nxt_conf_vldt_error(vldt, "The \"weight\" number must "
+                                   "not exceed %d.", NXT_INT32_T_MAX);
+    }
+
+    return NXT_OK;
+}
diff --git a/src/nxt_h1proto.c b/src/nxt_h1proto.c
index 8ce57893..1a6c537e 100644
--- a/src/nxt_h1proto.c
+++ b/src/nxt_h1proto.c
@@ -6,6 +6,7 @@
 
 #include <nxt_router.h>
 #include <nxt_http.h>
+#include <nxt_upstream.h>
 #include <nxt_h1proto.h>
 #include <nxt_websocket.h>
 #include <nxt_websocket_header.h>
@@ -2004,7 +2005,7 @@ nxt_h1p_peer_connect(nxt_task_t *task, nxt_http_peer_t *peer)
     c->read_timer.task = task;
     c->write_timer.task = task;
     c->socket.data = peer;
-    c->remote = peer->sockaddr;
+    c->remote = peer->server->sockaddr;
 
     c->socket.write_ready = 1;
     c->write_state = &nxt_h1p_peer_connect_state;
diff --git a/src/nxt_http.h b/src/nxt_http.h
index 67c7645b..0e0694e5 100644
--- a/src/nxt_http.h
+++ b/src/nxt_http.h
@@ -106,10 +106,12 @@ typedef struct {
 } nxt_http_response_t;
 
 
+typedef struct nxt_upstream_server_s  nxt_upstream_server_t;
+
 typedef struct {
     nxt_http_proto_t                proto;
     nxt_http_request_t              *request;
-    nxt_sockaddr_t                  *sockaddr;
+    nxt_upstream_server_t           *server;
     nxt_list_t                      *fields;
     nxt_buf_t                       *body;
     nxt_off_t                       remainder;
@@ -178,7 +180,6 @@ struct nxt_http_request_s {
 
 
 typedef struct nxt_http_route_s     nxt_http_route_t;
-typedef struct nxt_http_upstream_s  nxt_http_upstream_t;
 
 
 struct nxt_http_action_s {
@@ -187,9 +188,10 @@ struct nxt_http_action_s {
                                         nxt_http_action_t *action);
     union {
         nxt_http_route_t            *route;
-        nxt_http_upstream_t         *upstream;
         nxt_app_t                   *application;
         nxt_http_action_t           *fallback;
+        nxt_upstream_t              *upstream;
+        uint32_t                    upstream_number;
     } u;
 
     nxt_str_t                       name;
@@ -275,6 +277,11 @@ nxt_http_action_t *nxt_http_pass_application(nxt_task_t *task,
 void nxt_http_routes_cleanup(nxt_task_t *task, nxt_http_routes_t *routes);
 void nxt_http_action_cleanup(nxt_task_t *task, nxt_http_action_t *action);
 
+nxt_int_t nxt_upstreams_create(nxt_task_t *task, nxt_router_temp_conf_t *tmcf,
+    nxt_conf_value_t *conf);
+nxt_int_t nxt_upstreams_joint_create(nxt_router_temp_conf_t *tmcf,
+    nxt_upstream_t ***upstream_joint);
+
 nxt_http_action_t *nxt_http_static_handler(nxt_task_t *task,
     nxt_http_request_t *r, nxt_http_action_t *action);
 nxt_int_t nxt_http_static_mtypes_init(nxt_mp_t *mp, nxt_lvlhsh_t *hash);
@@ -285,6 +292,11 @@ nxt_str_t *nxt_http_static_mtypes_hash_find(nxt_lvlhsh_t *hash,
 
 nxt_http_action_t *nxt_http_application_handler(nxt_task_t *task,
     nxt_http_request_t *r, nxt_http_action_t *action);
+void nxt_upstream_find(nxt_upstreams_t *upstreams, nxt_str_t *name,
+    nxt_http_action_t *action);
+nxt_http_action_t *nxt_upstream_proxy_handler(nxt_task_t *task,
+    nxt_http_request_t *r, nxt_upstream_t *upstream);
+
 
 nxt_int_t nxt_http_proxy_create(nxt_mp_t *mp, nxt_http_action_t *action);
 nxt_int_t nxt_http_proxy_date(void *ctx, nxt_http_field_t *field,
diff --git a/src/nxt_http_proxy.c b/src/nxt_http_proxy.c
index 7f4eeff2..893e9303 100644
--- a/src/nxt_http_proxy.c
+++ b/src/nxt_http_proxy.c
@@ -6,23 +6,21 @@
 
 #include <nxt_router.h>
 #include <nxt_http.h>
+#include <nxt_upstream.h>
 
 
-typedef void (*nxt_http_upstream_connect_t)(nxt_task_t *task,
-    nxt_http_upstream_t *upstream, nxt_http_peer_t *peer);
-
-
-struct nxt_http_upstream_s {
-    uint32_t                     current;
-    uint32_t                     n;
-    uint8_t                      protocol;
-    nxt_http_upstream_connect_t  connect;
-    nxt_sockaddr_t               *sockaddr[1];
+struct nxt_upstream_proxy_s {
+    nxt_sockaddr_t  *sockaddr;
+    uint8_t         protocol;
 };
 
 
-static void nxt_http_upstream_connect(nxt_task_t *task,
-    nxt_http_upstream_t *upstream, nxt_http_peer_t *peer);
+static void nxt_http_proxy_server_get(nxt_task_t *task,
+    nxt_upstream_server_t *us);
+static void nxt_http_proxy_upstream_ready(nxt_task_t *task,
+    nxt_upstream_server_t *us);
+static void nxt_http_proxy_upstream_error(nxt_task_t *task,
+    nxt_upstream_server_t *us);
 static nxt_http_action_t *nxt_http_proxy_handler(nxt_task_t *task,
     nxt_http_request_t *r, nxt_http_action_t *action);
 static void nxt_http_proxy_header_send(nxt_task_t *task, void *obj, void *data);
@@ -43,12 +41,24 @@ static const nxt_http_request_state_t  nxt_http_proxy_header_read_state;
 static const nxt_http_request_state_t  nxt_http_proxy_read_state;
 
 
+static const nxt_upstream_server_proto_t  nxt_upstream_simple_proto = {
+    .get = nxt_http_proxy_server_get,
+};
+
+
+static const nxt_upstream_peer_state_t  nxt_upstream_proxy_state = {
+    .ready = nxt_http_proxy_upstream_ready,
+    .error = nxt_http_proxy_upstream_error,
+};
+
+
 nxt_int_t
 nxt_http_proxy_create(nxt_mp_t *mp, nxt_http_action_t *action)
 {
-    nxt_str_t            name;
-    nxt_sockaddr_t       *sa;
-    nxt_http_upstream_t  *upstream;
+    nxt_str_t             name;
+    nxt_sockaddr_t        *sa;
+    nxt_upstream_t        *up;
+    nxt_upstream_proxy_t  *proxy;
 
     sa = NULL;
     name = action->name;
@@ -66,18 +76,25 @@ nxt_http_proxy_create(nxt_mp_t *mp, nxt_http_action_t *action)
     }
 
     if (sa != NULL) {
-        upstream = nxt_mp_alloc(mp, sizeof(nxt_http_upstream_t));
-        if (nxt_slow_path(upstream == NULL)) {
+        up = nxt_mp_alloc(mp, sizeof(nxt_upstream_t));
+        if (nxt_slow_path(up == NULL)) {
+            return NXT_ERROR;
+        }
+
+        up->name.length = sa->length;
+        up->name.start = nxt_sockaddr_start(sa);
+        up->proto = &nxt_upstream_simple_proto;
+
+        proxy = nxt_mp_alloc(mp, sizeof(nxt_upstream_proxy_t));
+        if (nxt_slow_path(proxy == NULL)) {
             return NXT_ERROR;
         }
 
-        upstream->current = 0;
-        upstream->n = 1;
-        upstream->protocol = NXT_HTTP_PROTO_H1;
-        upstream->connect = nxt_http_upstream_connect;
-        upstream->sockaddr[0] = sa;
+        proxy->sockaddr = sa;
+        proxy->protocol = NXT_HTTP_PROTO_H1;
+        up->type.proxy = proxy;
 
-        action->u.upstream = upstream;
+        action->u.upstream = up;
         action->handler = nxt_http_proxy_handler;
     }
 
@@ -89,7 +106,22 @@ static nxt_http_action_t *
 nxt_http_proxy_handler(nxt_task_t *task, nxt_http_request_t *r,
     nxt_http_action_t *action)
 {
-    nxt_http_peer_t  *peer;
+    return nxt_upstream_proxy_handler(task, r, action->u.upstream);
+}
+
+
+nxt_http_action_t *
+nxt_upstream_proxy_handler(nxt_task_t *task, nxt_http_request_t *r,
+    nxt_upstream_t *upstream)
+{
+    nxt_http_peer_t        *peer;
+    nxt_upstream_server_t  *us;
+
+    us = nxt_mp_zalloc(r->mem_pool, sizeof(nxt_upstream_server_t));
+    if (nxt_slow_path(us == NULL)) {
+        nxt_http_request_error(task, r, NXT_HTTP_INTERNAL_SERVER_ERROR);
+        return NULL;
+    }
 
     peer = nxt_mp_zalloc(r->mem_pool, sizeof(nxt_http_peer_t));
     if (nxt_slow_path(peer == NULL)) {
@@ -102,18 +134,39 @@ nxt_http_proxy_handler(nxt_task_t *task, nxt_http_request_t *r,
 
     nxt_mp_retain(r->mem_pool);
 
-    action->u.upstream->connect(task, action->u.upstream, peer);
+    us->state = &nxt_upstream_proxy_state;
+    us->peer.http = peer;
+    peer->server = us;
+
+    us->upstream = upstream;
+    upstream->proto->get(task, us);
 
     return NULL;
 }
 
 
 static void
-nxt_http_upstream_connect(nxt_task_t *task, nxt_http_upstream_t *upstream,
-    nxt_http_peer_t *peer)
+nxt_http_proxy_server_get(nxt_task_t *task, nxt_upstream_server_t *us)
 {
-    peer->protocol = upstream->protocol;
-    peer->sockaddr = upstream->sockaddr[0];
+    nxt_upstream_proxy_t  *proxy;
+
+    proxy = us->upstream->type.proxy;
+
+    us->sockaddr = proxy->sockaddr;
+    us->protocol = proxy->protocol;
+
+    us->state->ready(task, us);
+}
+
+
+static void
+nxt_http_proxy_upstream_ready(nxt_task_t *task, nxt_upstream_server_t *us)
+{
+    nxt_http_peer_t  *peer;
+
+    peer = us->peer.http;
+
+    peer->protocol = us->protocol;
 
     peer->request->state = &nxt_http_proxy_header_send_state;
 
@@ -121,6 +174,19 @@ nxt_http_upstream_connect(nxt_task_t *task, nxt_http_upstream_t *upstream,
 }
 
 
+static void
+nxt_http_proxy_upstream_error(nxt_task_t *task, nxt_upstream_server_t *us)
+{
+    nxt_http_request_t  *r;
+
+    r = us->peer.http->request;
+
+    nxt_mp_release(r->mem_pool);
+
+    nxt_http_request_error(task, r, NXT_HTTP_BAD_GATEWAY);
+}
+
+
 static const nxt_http_request_state_t  nxt_http_proxy_header_send_state
     nxt_aligned(64) =
 {
diff --git a/src/nxt_http_route.c b/src/nxt_http_route.c
index df52894a..d7f20bcb 100644
--- a/src/nxt_http_route.c
+++ b/src/nxt_http_route.c
@@ -1114,6 +1114,12 @@ nxt_http_action_resolve(nxt_task_t *task, nxt_router_temp_conf_t *tmcf,
         nxt_router_listener_application(tmcf, &name, action);
         nxt_router_app_use(task, action->u.application, 1);
 
+    } else if (nxt_str_start(&name, "upstreams/", 10)) {
+        name.length -= 10;
+        name.start += 10;
+
+        nxt_upstream_find(tmcf->router_conf->upstreams, &name, action);
+
     } else if (nxt_str_start(&name, "routes", 6)) {
 
         if (name.length == 6) {
diff --git a/src/nxt_router.c b/src/nxt_router.c
index 46a6b921..d77ffa2b 100644
--- a/src/nxt_router.c
+++ b/src/nxt_router.c
@@ -1634,6 +1634,11 @@ nxt_router_conf_create(nxt_task_t *task, nxt_router_temp_conf_t *tmcf,
         tmcf->router_conf->routes = routes;
     }
 
+    ret = nxt_upstreams_create(task, tmcf, conf);
+    if (nxt_slow_path(ret != NXT_OK)) {
+        return ret;
+    }
+
     http = nxt_conf_get_path(conf, &http_path);
 #if 0
     if (http == NULL) {
@@ -2526,6 +2531,7 @@ nxt_router_engine_joints_create(nxt_router_temp_conf_t *tmcf,
     nxt_router_engine_conf_t *recf, nxt_queue_t *sockets,
     nxt_work_handler_t handler)
 {
+    nxt_int_t                ret;
     nxt_joint_job_t          *job;
     nxt_queue_link_t         *qlk;
     nxt_socket_conf_t        *skcf;
@@ -2559,6 +2565,11 @@ nxt_router_engine_joints_create(nxt_router_temp_conf_t *tmcf,
 
         job->work.data = joint;
 
+        ret = nxt_upstreams_joint_create(tmcf, &joint->upstreams);
+        if (nxt_slow_path(ret != NXT_OK)) {
+            return ret;
+        }
+
         joint->count = 1;
 
         skcf = nxt_queue_link_data(qlk, nxt_socket_conf_t, link);
diff --git a/src/nxt_router.h b/src/nxt_router.h
index 9ce9f3be..85ef9a6c 100644
--- a/src/nxt_router.h
+++ b/src/nxt_router.h
@@ -18,6 +18,8 @@ typedef struct nxt_http_request_s  nxt_http_request_t;
 
 typedef struct nxt_http_action_s        nxt_http_action_t;
 typedef struct nxt_http_routes_s        nxt_http_routes_t;
+typedef struct nxt_upstream_s           nxt_upstream_t;
+typedef struct nxt_upstreams_s          nxt_upstreams_t;
 typedef struct nxt_router_access_log_s  nxt_router_access_log_t;
 
 
@@ -43,6 +45,7 @@ typedef struct {
 
     nxt_router_t             *router;
     nxt_http_routes_t        *routes;
+    nxt_upstreams_t          *upstreams;
 
     nxt_lvlhsh_t             mtypes_hash;
 
@@ -196,6 +199,8 @@ typedef struct {
     nxt_event_engine_t     *engine;
     nxt_socket_conf_t      *socket_conf;
 
+    nxt_upstream_t         **upstreams;
+
     /* Modules configuraitons. */
 } nxt_socket_conf_joint_t;
 
diff --git a/src/nxt_upstream.c b/src/nxt_upstream.c
index 3899a3ce..66b6619a 100644
--- a/src/nxt_upstream.c
+++ b/src/nxt_upstream.c
@@ -4,4 +4,137 @@
  * Copyright (C) NGINX, Inc.
  */
 
-#include <nxt_main.h>
+#include <nxt_router.h>
+#include <nxt_http.h>
+#include <nxt_upstream.h>
+
+
+static nxt_http_action_t *nxt_upstream_handler(nxt_task_t *task,
+    nxt_http_request_t *r, nxt_http_action_t *action);
+
+
+nxt_int_t
+nxt_upstreams_create(nxt_task_t *task, nxt_router_temp_conf_t *tmcf,
+    nxt_conf_value_t *conf)
+{
+    size_t            size;
+    uint32_t          i, n, next;
+    nxt_mp_t          *mp;
+    nxt_int_t         ret;
+    nxt_str_t         name, *string;
+    nxt_upstreams_t   *upstreams;
+    nxt_conf_value_t  *upstreams_conf, *upcf;
+
+    static nxt_str_t  upstreams_name = nxt_string("upstreams");
+
+    upstreams_conf = nxt_conf_get_object_member(conf, &upstreams_name, NULL);
+
+    if (upstreams_conf == NULL) {
+        return NXT_OK;
+    }
+
+    n = nxt_conf_object_members_count(upstreams_conf);
+
+    if (n == 0) {
+        return NXT_OK;
+    }
+
+    mp = tmcf->router_conf->mem_pool;
+    size = sizeof(nxt_upstreams_t) + n * sizeof(nxt_upstream_t);
+
+    upstreams = nxt_mp_zalloc(mp, size);
+    if (nxt_slow_path(upstreams == NULL)) {
+        return NXT_ERROR;
+    }
+
+    upstreams->items = n;
+    next = 0;
+
+    for (i = 0; i < n; i++) {
+        upcf = nxt_conf_next_object_member(upstreams_conf, &name, &next);
+
+        string = nxt_str_dup(mp, &upstreams->upstream[i].name, &name);
+        if (nxt_slow_path(string == NULL)) {
+            return NXT_ERROR;
+        }
+
+        ret = nxt_upstream_round_robin_create(task, tmcf, upcf,
+                                              &upstreams->upstream[i]);
+        if (nxt_slow_path(ret != NXT_OK)) {
+            return NXT_ERROR;
+        }
+    }
+
+    tmcf->router_conf->upstreams = upstreams;
+
+    return NXT_OK;
+}
+
+
+void
+nxt_upstream_find(nxt_upstreams_t *upstreams, nxt_str_t *name,
+    nxt_http_action_t *action)
+{
+    uint32_t        i, n;
+    nxt_upstream_t  *upstream;
+
+    upstream = &upstreams->upstream[0];
+    n = upstreams->items;
+
+    for (i = 0; i < n; i++) {
+        if (nxt_strstr_eq(&upstream[i].name, name)) {
+            action->u.upstream_number = i;
+            action->handler = nxt_upstream_handler;
+
+            return;
+        }
+    }
+}
+
+
+nxt_int_t
+nxt_upstreams_joint_create(nxt_router_temp_conf_t *tmcf,
+    nxt_upstream_t ***upstream_joint)
+{
+    uint32_t           i, n;
+    nxt_upstream_t     *u, **up;
+    nxt_upstreams_t    *upstreams;
+    nxt_router_conf_t  *router_conf;
+
+    router_conf = tmcf->router_conf;
+    upstreams = router_conf->upstreams;
+
+    if (upstreams == NULL) {
+        *upstream_joint = NULL;
+        return NXT_OK;
+    }
+
+    n = upstreams->items;
+
+    up = nxt_mp_zalloc(router_conf->mem_pool, n * sizeof(nxt_upstream_t *));
+    if (nxt_slow_path(up == NULL)) {
+        return NXT_ERROR;
+    }
+
+    u = &upstreams->upstream[0];
+
+    for (i = 0; i < n; i++) {
+        up[i] = u[i].proto->joint_create(tmcf, &u[i]);
+        if (nxt_slow_path(up[i] == NULL)) {
+            return NXT_ERROR;
+        }
+    }
+
+    *upstream_joint = up;
+
+    return NXT_OK;
+}
+
+
+static nxt_http_action_t *
+nxt_upstream_handler(nxt_task_t *task, nxt_http_request_t *r,
+    nxt_http_action_t *action)
+{
+    return nxt_upstream_proxy_handler(task, r,
+                              r->conf->upstreams[action->u.upstream_number]);
+}
diff --git a/src/nxt_upstream.h b/src/nxt_upstream.h
index a25e0940..afc53774 100644
--- a/src/nxt_upstream.h
+++ b/src/nxt_upstream.h
@@ -8,4 +8,74 @@
 #define _NXT_UPSTREAM_H_INCLUDED_
 
 
+typedef struct nxt_upstream_proxy_s            nxt_upstream_proxy_t;
+typedef struct nxt_upstream_round_robin_s      nxt_upstream_round_robin_t;
+typedef struct nxt_upstream_round_robin_server_s
+    nxt_upstream_round_robin_server_t;
+
+
+typedef void (*nxt_upstream_peer_ready_t)(nxt_task_t *task,
+    nxt_upstream_server_t *us);
+typedef void (*nxt_upstream_peer_error_t)(nxt_task_t *task,
+    nxt_upstream_server_t *us);
+
+
+typedef struct {
+    nxt_upstream_peer_ready_t                  ready;
+    nxt_upstream_peer_error_t                  error;
+} nxt_upstream_peer_state_t;
+
+
+typedef nxt_upstream_t *(*nxt_upstream_joint_create_t)(
+    nxt_router_temp_conf_t *tmcf, nxt_upstream_t *upstream);
+typedef void (*nxt_upstream_server_get_t)(nxt_task_t *task,
+    nxt_upstream_server_t *us);
+
+
+typedef struct {
+    nxt_upstream_joint_create_t                joint_create;
+    nxt_upstream_server_get_t                  get;
+} nxt_upstream_server_proto_t;
+
+
+struct nxt_upstream_s {
+    const nxt_upstream_server_proto_t          *proto;
+
+    union {
+        nxt_upstream_proxy_t                   *proxy;
+        nxt_upstream_round_robin_t             *round_robin;
+    } type;
+
+    nxt_str_t                                  name;
+};
+
+
+struct nxt_upstreams_s {
+    uint32_t                                   items;
+    nxt_upstream_t                             upstream[0];
+};
+
+
+struct nxt_upstream_server_s {
+    nxt_sockaddr_t                             *sockaddr;
+    const nxt_upstream_peer_state_t            *state;
+    nxt_upstream_t                             *upstream;
+
+    uint8_t                                    protocol;
+
+    union {
+        nxt_upstream_round_robin_server_t      *round_robin;
+    } server;
+
+    union {
+        nxt_http_peer_t                        *http;
+    } peer;
+};
+
+
+nxt_int_t nxt_upstream_round_robin_create(nxt_task_t *task,
+    nxt_router_temp_conf_t *tmcf, nxt_conf_value_t *upstream_conf,
+    nxt_upstream_t *upstream);
+
+
 #endif /* _NXT_UPSTREAM_H_INCLUDED_ */
diff --git a/src/nxt_upstream_round_robin.c b/src/nxt_upstream_round_robin.c
index 4d53c716..fd76ecb5 100644
--- a/src/nxt_upstream_round_robin.c
+++ b/src/nxt_upstream_round_robin.c
@@ -4,3 +4,188 @@
  * Copyright (C) NGINX, Inc.
  */
 
+#include <nxt_router.h>
+#include <nxt_http.h>
+#include <nxt_upstream.h>
+
+
+struct nxt_upstream_round_robin_server_s {
+    nxt_sockaddr_t                     *sockaddr;
+
+    int32_t                            current_weight;
+    int32_t                            effective_weight;
+    int32_t                            weight;
+
+    uint8_t                            protocol;
+};
+
+
+struct nxt_upstream_round_robin_s {
+    uint32_t                           items;
+    nxt_upstream_round_robin_server_t  server[0];
+};
+
+
+static nxt_upstream_t *nxt_upstream_round_robin_joint_create(
+    nxt_router_temp_conf_t *tmcf, nxt_upstream_t *upstream);
+static void nxt_upstream_round_robin_server_get(nxt_task_t *task,
+    nxt_upstream_server_t *us);
+
+
+static const nxt_upstream_server_proto_t  nxt_upstream_round_robin_proto = {
+    .joint_create = nxt_upstream_round_robin_joint_create,
+    .get          = nxt_upstream_round_robin_server_get,
+};
+
+
+static nxt_conf_map_t  nxt_upstream_round_robin_server_conf[] = {
+    {
+        nxt_string("weight"),
+        NXT_CONF_MAP_INT32,
+        offsetof(nxt_upstream_round_robin_server_t, weight),
+    },
+};
+
+
+nxt_int_t
+nxt_upstream_round_robin_create(nxt_task_t *task, nxt_router_temp_conf_t *tmcf,
+    nxt_conf_value_t *upstream_conf, nxt_upstream_t *upstream)
+{
+    size_t                      size;
+    uint32_t                    i, n, next;
+    nxt_mp_t                    *mp;
+    nxt_str_t                   name;
+    nxt_sockaddr_t              *sa;
+    nxt_conf_value_t            *servers_conf, *srvcf;
+    nxt_upstream_round_robin_t  *urr;
+
+    static nxt_str_t  servers = nxt_string("servers");
+
+    mp = tmcf->router_conf->mem_pool;
+
+    servers_conf = nxt_conf_get_object_member(upstream_conf, &servers, NULL);
+    n = nxt_conf_object_members_count(servers_conf);
+
+    size = sizeof(nxt_upstream_round_robin_t)
+           + n * sizeof(nxt_upstream_round_robin_server_t);
+
+    urr = nxt_mp_zalloc(mp, size);
+    if (nxt_slow_path(urr == NULL)) {
+        return NXT_ERROR;
+    }
+
+    urr->items = n;
+    next = 0;
+
+    for (i = 0; i < n; i++) {
+        srvcf = nxt_conf_next_object_member(servers_conf, &name, &next);
+
+        sa = nxt_sockaddr_parse(mp, &name);
+        if (nxt_slow_path(sa == NULL)) {
+            return NXT_ERROR;
+        }
+
+        sa->type = SOCK_STREAM;
+
+        urr->server[i].sockaddr = sa;
+        urr->server[i].weight = 1;
+        urr->server[i].protocol = NXT_HTTP_PROTO_H1;
+
+        nxt_conf_map_object(mp, srvcf, nxt_upstream_round_robin_server_conf,
+                            nxt_nitems(nxt_upstream_round_robin_server_conf),
+                            &urr->server[i]);
+
+        urr->server[i].effective_weight = urr->server[i].weight;
+    }
+
+    upstream->proto = &nxt_upstream_round_robin_proto;
+    upstream->type.round_robin = urr;
+
+    return NXT_OK;
+}
+
+
+static nxt_upstream_t *
+nxt_upstream_round_robin_joint_create(nxt_router_temp_conf_t *tmcf,
+    nxt_upstream_t *upstream)
+{
+    size_t                      size;
+    uint32_t                    i, n;
+    nxt_mp_t                    *mp;
+    nxt_upstream_t              *u;
+    nxt_upstream_round_robin_t  *urr, *urrcf;
+
+    mp = tmcf->router_conf->mem_pool;
+
+    u = nxt_mp_alloc(mp, sizeof(nxt_upstream_t));
+    if (nxt_slow_path(u == NULL)) {
+        return NULL;
+    }
+
+    *u = *upstream;
+
+    urrcf = upstream->type.round_robin;
+
+    size = sizeof(nxt_upstream_round_robin_t)
+           + urrcf->items * sizeof(nxt_upstream_round_robin_server_t);
+
+    urr = nxt_mp_alloc(mp, size);
+    if (nxt_slow_path(urr == NULL)) {
+        return NULL;
+    }
+
+    u->type.round_robin = urr;
+
+    n = urrcf->items;
+    urr->items = n;
+
+    for (i = 0; i < n; i++) {
+        urr->server[i] = urrcf->server[i];
+    }
+
+    return u;
+}
+
+
+static void
+nxt_upstream_round_robin_server_get(nxt_task_t *task, nxt_upstream_server_t *us)
+{
+    int32_t                            total;
+    uint32_t                           i, n;
+    nxt_upstream_round_robin_t         *round_robin;
+    nxt_upstream_round_robin_server_t  *s, *best;
+
+    best = NULL;
+    total = 0;
+
+    round_robin = us->upstream->type.round_robin;
+
+    s = round_robin->server;
+    n = round_robin->items;
+
+    for (i = 0; i < n; i++) {
+
+        s[i].current_weight += s[i].effective_weight;
+        total += s[i].effective_weight;
+
+        if (s[i].effective_weight < s[i].weight) {
+            s[i].effective_weight++;
+        }
+
+        if (best == NULL || s[i].current_weight > best->current_weight) {
+            best = &s[i];
+        }
+    }
+
+    if (best == NULL) {
+        us->state->error(task, us);
+        return;
+    }
+
+    best->current_weight -= total;
+    us->sockaddr = best->sockaddr;
+    us->protocol = best->protocol;
+    us->server.round_robin = best;
+
+    us->state->ready(task, us);
+}