src/http/ngx_http_upstream_round_robin.c - net/nginx-mbedtls - Rivoreo Source Code Repositories


 /*
  * Copyright (C) Igor Sysoev
  */


 #include <ngx_config.h>
 #include <ngx_core.h>
 #include <ngx_http.h>


 static ngx_int_t ngx_http_upstream_cmp_servers(const void *one,
     const void *two);
 static ngx_uint_t
 ngx_http_upstream_get_peer(ngx_http_upstream_rr_peers_t *peers);

 #if (NGX_HTTP_SSL)

 static ngx_int_t ngx_http_upstream_empty_set_session(ngx_peer_connection_t *pc,
     void *data);
 static void ngx_http_upstream_empty_save_session(ngx_peer_connection_t *pc,
     void *data);

 #endif


 ngx_int_t
 ngx_http_upstream_init_round_robin(ngx_conf_t *cf,
     ngx_http_upstream_srv_conf_t *us)
 {
     ngx_url_t                      u;
     ngx_uint_t                     i, j, n;
     ngx_http_upstream_server_t    *server;
     ngx_http_upstream_rr_peers_t  *peers, *backup;

     us->peer.init = ngx_http_upstream_init_round_robin_peer;

     if (us->servers) {
         server = us->servers->elts;

         n = 0;

         for (i = 0; i < us->servers->nelts; i++) {
             if (server[i].backup) {
                 continue;
             }

             n += server[i].naddrs;
         }

         peers = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_rr_peers_t)
                               + sizeof(ngx_http_upstream_rr_peer_t) * (n - 1));
         if (peers == NULL) {
             return NGX_ERROR;
         }

         peers->single = (n == 1);
         peers->number = n;
         peers->name = &us->host;

         n = 0;

         for (i = 0; i < us->servers->nelts; i++) {
             for (j = 0; j < server[i].naddrs; j++) {
                 if (server[i].backup) {
                     continue;
                 }

                 peers->peer[n].sockaddr = server[i].addrs[j].sockaddr;
                 peers->peer[n].socklen = server[i].addrs[j].socklen;
                 peers->peer[n].name = server[i].addrs[j].name;
                 peers->peer[n].max_fails = server[i].max_fails;
                 peers->peer[n].fail_timeout = server[i].fail_timeout;
                 peers->peer[n].down = server[i].down;
                 peers->peer[n].weight = server[i].down ? 0 : server[i].weight;
                 peers->peer[n].current_weight = peers->peer[n].weight;
                 n++;
             }
         }

         us->peer.data = peers;

         ngx_sort(&peers->peer[0], (size_t) n,
                  sizeof(ngx_http_upstream_rr_peer_t),
                  ngx_http_upstream_cmp_servers);

         /* backup servers */

         n = 0;

         for (i = 0; i < us->servers->nelts; i++) {
             if (!server[i].backup) {
                 continue;
             }

             n += server[i].naddrs;
         }

         if (n == 0) {
             return NGX_OK;
         }

         backup = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_rr_peers_t)
                               + sizeof(ngx_http_upstream_rr_peer_t) * (n - 1));
         if (backup == NULL) {
             return NGX_ERROR;
         }

         peers->single = 0;
         backup->single = 0;
         backup->number = n;
         backup->name = &us->host;

         n = 0;

         for (i = 0; i < us->servers->nelts; i++) {
             for (j = 0; j < server[i].naddrs; j++) {
                 if (!server[i].backup) {
                     continue;
                 }

                 backup->peer[n].sockaddr = server[i].addrs[j].sockaddr;
                 backup->peer[n].socklen = server[i].addrs[j].socklen;
                 backup->peer[n].name = server[i].addrs[j].name;
                 backup->peer[n].weight = server[i].weight;
                 backup->peer[n].current_weight = server[i].weight;
                 backup->peer[n].max_fails = server[i].max_fails;
                 backup->peer[n].fail_timeout = server[i].fail_timeout;
                 backup->peer[n].down = server[i].down;
                 n++;
             }
         }

         peers->next = backup;

         ngx_sort(&backup->peer[0], (size_t) n,
                  sizeof(ngx_http_upstream_rr_peer_t),
                  ngx_http_upstream_cmp_servers);

         return NGX_OK;
     }


     /* an upstream implicitly defined by proxy_pass, etc. */

     if (us->port == 0 && us->default_port == 0) {
         ngx_log_error(NGX_LOG_EMERG, cf->log, 0,
                       "no port in upstream \"%V\" in %s:%ui",
                       &us->host, us->file_name, us->line);
         return NGX_ERROR;
     }

     ngx_memzero(&u, sizeof(ngx_url_t));

     u.host = us->host;
     u.port = (in_port_t) (us->port ? us->port : us->default_port);

     if (ngx_inet_resolve_host(cf->pool, &u) != NGX_OK) {
         if (u.err) {
             ngx_log_error(NGX_LOG_EMERG, cf->log, 0,
                           "%s in upstream \"%V\" in %s:%ui",
                           u.err, &us->host, us->file_name, us->line);
         }

         return NGX_ERROR;
     }

     n = u.naddrs;

     peers = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_rr_peers_t)
                               + sizeof(ngx_http_upstream_rr_peer_t) * (n - 1));
     if (peers == NULL) {
         return NGX_ERROR;
     }

     peers->single = (n == 1);
     peers->number = n;
     peers->name = &us->host;

     for (i = 0; i < u.naddrs; i++) {
         peers->peer[i].sockaddr = u.addrs[i].sockaddr;
         peers->peer[i].socklen = u.addrs[i].socklen;
         peers->peer[i].name = u.addrs[i].name;
         peers->peer[i].weight = 1;
         peers->peer[i].current_weight = 1;
         peers->peer[i].max_fails = 1;
         peers->peer[i].fail_timeout = 10;
     }

     us->peer.data = peers;

     /* implicitly defined upstream has no backup servers */

     return NGX_OK;
 }


 static ngx_int_t
 ngx_http_upstream_cmp_servers(const void *one, const void *two)
 {
     ngx_http_upstream_rr_peer_t  *first, *second;

     first = (ngx_http_upstream_rr_peer_t *) one;
     second = (ngx_http_upstream_rr_peer_t *) two;

     return (first->weight < second->weight);
 }


 ngx_int_t
 ngx_http_upstream_init_round_robin_peer(ngx_http_request_t *r,
     ngx_http_upstream_srv_conf_t *us)
 {
     ngx_uint_t                         n;
     ngx_http_upstream_rr_peer_data_t  *rrp;

     rrp = r->upstream->peer.data;

     if (rrp == NULL) {
         rrp = ngx_palloc(r->pool, sizeof(ngx_http_upstream_rr_peer_data_t));
         if (rrp == NULL) {
             return NGX_ERROR;
         }

         r->upstream->peer.data = rrp;
     }

     rrp->peers = us->peer.data;
     rrp->current = 0;

     n = rrp->peers->number;

     if (rrp->peers->next && rrp->peers->next->number > n) {
         n = rrp->peers->next->number;
     }

     if (n <= 8 * sizeof(uintptr_t)) {
         rrp->tried = &rrp->data;
         rrp->data = 0;

     } else {
         n = (n + (8 * sizeof(uintptr_t) - 1)) / (8 * sizeof(uintptr_t));

         rrp->tried = ngx_pcalloc(r->pool, n * sizeof(uintptr_t));
         if (rrp->tried == NULL) {
             return NGX_ERROR;
         }
     }

     r->upstream->peer.get = ngx_http_upstream_get_round_robin_peer;
     r->upstream->peer.free = ngx_http_upstream_free_round_robin_peer;
     r->upstream->peer.tries = rrp->peers->number;
 #if (NGX_HTTP_SSL)
     r->upstream->peer.set_session =
                                ngx_http_upstream_set_round_robin_peer_session;
     r->upstream->peer.save_session =
                                ngx_http_upstream_save_round_robin_peer_session;
 #endif

     return NGX_OK;
 }


 ngx_int_t
 ngx_http_upstream_create_round_robin_peer(ngx_http_request_t *r,
     ngx_http_upstream_resolved_t *ur)
 {
     u_char                            *p;
     size_t                             len;
     ngx_uint_t                         i, n;
     struct sockaddr_in                *sin;
     ngx_http_upstream_rr_peers_t      *peers;
     ngx_http_upstream_rr_peer_data_t  *rrp;

     rrp = r->upstream->peer.data;

     if (rrp == NULL) {
         rrp = ngx_palloc(r->pool, sizeof(ngx_http_upstream_rr_peer_data_t));
         if (rrp == NULL) {
             return NGX_ERROR;
         }

         r->upstream->peer.data = rrp;
     }

     peers = ngx_pcalloc(r->pool, sizeof(ngx_http_upstream_rr_peers_t)
                      + sizeof(ngx_http_upstream_rr_peer_t) * (ur->naddrs - 1));
     if (peers == NULL) {
         return NGX_ERROR;
     }

     peers->single = (ur->naddrs == 1);
     peers->number = ur->naddrs;
     peers->name = &ur->host;

     if (ur->sockaddr) {
         peers->peer[0].sockaddr = ur->sockaddr;
         peers->peer[0].socklen = ur->socklen;
         peers->peer[0].name = ur->host;
         peers->peer[0].weight = 1;
         peers->peer[0].current_weight = 1;
         peers->peer[0].max_fails = 1;
         peers->peer[0].fail_timeout = 10;

     } else {

         for (i = 0; i < ur->naddrs; i++) {

             len = NGX_INET_ADDRSTRLEN + sizeof(":65536") - 1;

             p = ngx_pnalloc(r->pool, len);
             if (p == NULL) {
                 return NGX_ERROR;
             }

             len = ngx_inet_ntop(AF_INET, &ur->addrs[i], p, NGX_INET_ADDRSTRLEN);
             len = ngx_sprintf(&p[len], ":%d", ur->port) - p;

             sin = ngx_pcalloc(r->pool, sizeof(struct sockaddr_in));
             if (sin == NULL) {
                 return NGX_ERROR;
             }

             sin->sin_family = AF_INET;
             sin->sin_port = htons(ur->port);
             sin->sin_addr.s_addr = ur->addrs[i];

             peers->peer[i].sockaddr = (struct sockaddr *) sin;
             peers->peer[i].socklen = sizeof(struct sockaddr_in);
             peers->peer[i].name.len = len;
             peers->peer[i].name.data = p;
             peers->peer[i].weight = 1;
             peers->peer[i].current_weight = 1;
             peers->peer[i].max_fails = 1;
             peers->peer[i].fail_timeout = 10;
         }
     }

     rrp->peers = peers;
     rrp->current = 0;

     if (rrp->peers->number <= 8 * sizeof(uintptr_t)) {
         rrp->tried = &rrp->data;
         rrp->data = 0;

     } else {
         n = (rrp->peers->number + (8 * sizeof(uintptr_t) - 1))
                 / (8 * sizeof(uintptr_t));

         rrp->tried = ngx_pcalloc(r->pool, n * sizeof(uintptr_t));
         if (rrp->tried == NULL) {
             return NGX_ERROR;
         }
     }

     r->upstream->peer.get = ngx_http_upstream_get_round_robin_peer;
     r->upstream->peer.free = ngx_http_upstream_free_round_robin_peer;
     r->upstream->peer.tries = rrp->peers->number;
 #if (NGX_HTTP_SSL)
     r->upstream->peer.set_session = ngx_http_upstream_empty_set_session;
     r->upstream->peer.save_session = ngx_http_upstream_empty_save_session;
 #endif

     return NGX_OK;
 }


 ngx_int_t
 ngx_http_upstream_get_round_robin_peer(ngx_peer_connection_t *pc, void *data)
 {
     ngx_http_upstream_rr_peer_data_t  *rrp = data;

     time_t                         now;
     uintptr_t                      m;
     ngx_int_t                      rc;
     ngx_uint_t                     i, n;
     ngx_connection_t              *c;
     ngx_http_upstream_rr_peer_t   *peer;
     ngx_http_upstream_rr_peers_t  *peers;

     ngx_log_debug1(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                    "get rr peer, try: %ui", pc->tries);

     now = ngx_time();

     /* ngx_lock_mutex(rrp->peers->mutex); */

     if (rrp->peers->last_cached) {

         /* cached connection */

         c = rrp->peers->cached[rrp->peers->last_cached];
         rrp->peers->last_cached--;

         /* ngx_unlock_mutex(ppr->peers->mutex); */

 #if (NGX_THREADS)
         c->read->lock = c->read->own_lock;
         c->write->lock = c->write->own_lock;
 #endif

         pc->connection = c;
         pc->cached = 1;

         return NGX_OK;
     }

     pc->cached = 0;
     pc->connection = NULL;

     if (rrp->peers->single) {
         peer = &rrp->peers->peer[0];

     } else {

         /* there are several peers */

         if (pc->tries == rrp->peers->number) {

             /* it's a first try - get a current peer */

             i = pc->tries;

             for ( ;; ) {
                 rrp->current = ngx_http_upstream_get_peer(rrp->peers);

                 ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                                "get rr peer, current: %ui %i",
                                rrp->current,
                                rrp->peers->peer[rrp->current].current_weight);

                 n = rrp->current / (8 * sizeof(uintptr_t));
                 m = (uintptr_t) 1 << rrp->current % (8 * sizeof(uintptr_t));

                 if (!(rrp->tried[n] & m)) {
                     peer = &rrp->peers->peer[rrp->current];

                     if (!peer->down) {

                         if (peer->max_fails == 0
                             || peer->fails < peer->max_fails)
                         {
                             break;
                         }

                         if (now - peer->checked > peer->fail_timeout) {
                             peer->checked = now;
                             break;
                         }

                         peer->current_weight = 0;

                     } else {
                         rrp->tried[n] |= m;
                     }

                     pc->tries--;
                 }

                 if (pc->tries == 0) {
                     goto failed;
                 }

                 if (--i == 0) {
                     ngx_log_error(NGX_LOG_ALERT, pc->log, 0,
                                   "round robin upstream stuck on %ui tries",
                                   pc->tries);
                     goto failed;
                 }
             }

             peer->current_weight--;

         } else {

             i = pc->tries;

             for ( ;; ) {
                 n = rrp->current / (8 * sizeof(uintptr_t));
                 m = (uintptr_t) 1 << rrp->current % (8 * sizeof(uintptr_t));

                 if (!(rrp->tried[n] & m)) {

                     peer = &rrp->peers->peer[rrp->current];

                     if (!peer->down) {

                         if (peer->max_fails == 0
                             || peer->fails < peer->max_fails)
                         {
                             break;
                         }

                         if (now - peer->checked > peer->fail_timeout) {
                             peer->checked = now;
                             break;
                         }

                         peer->current_weight = 0;

                     } else {
                         rrp->tried[n] |= m;
                     }

                     pc->tries--;
                 }

                 rrp->current++;

                 if (rrp->current >= rrp->peers->number) {
                     rrp->current = 0;
                 }

                 if (pc->tries == 0) {
                     goto failed;
                 }

                 if (--i == 0) {
                     ngx_log_error(NGX_LOG_ALERT, pc->log, 0,
                                   "round robin upstream stuck on %ui tries",
                                   pc->tries);
                     goto failed;
                 }
             }

             peer->current_weight--;
         }

         rrp->tried[n] |= m;
     }

     pc->sockaddr = peer->sockaddr;
     pc->socklen = peer->socklen;
     pc->name = &peer->name;

     /* ngx_unlock_mutex(rrp->peers->mutex); */

     if (pc->tries == 1 && rrp->peers->next) {
         pc->tries += rrp->peers->next->number;

         n = rrp->peers->next->number / (8 * sizeof(uintptr_t)) + 1;
         for (i = 0; i < n; i++) {
              rrp->tried[i] = 0;
         }
     }

     return NGX_OK;

 failed:

     peers = rrp->peers;

     if (peers->next) {

         /* ngx_unlock_mutex(peers->mutex); */

         ngx_log_debug0(NGX_LOG_DEBUG_HTTP, pc->log, 0, "backup servers");

         rrp->peers = peers->next;
         pc->tries = rrp->peers->number;

         n = rrp->peers->number / (8 * sizeof(uintptr_t)) + 1;
         for (i = 0; i < n; i++) {
              rrp->tried[i] = 0;
         }

         rc = ngx_http_upstream_get_round_robin_peer(pc, rrp);

         if (rc != NGX_BUSY) {
             return rc;
         }

         /* ngx_lock_mutex(peers->mutex); */
     }

     /* all peers failed, mark them as live for quick recovery */

     for (i = 0; i < peers->number; i++) {
         peers->peer[i].fails = 0;
     }

     /* ngx_unlock_mutex(peers->mutex); */

     pc->name = peers->name;

     return NGX_BUSY;
 }


 static ngx_uint_t
 ngx_http_upstream_get_peer(ngx_http_upstream_rr_peers_t *peers)
 {
     ngx_uint_t                    i, n, reset = 0;
     ngx_http_upstream_rr_peer_t  *peer;

     peer = &peers->peer[0];

     for ( ;; ) {

         for (i = 0; i < peers->number; i++) {

             if (peer[i].current_weight <= 0) {
                 continue;
             }

             n = i;

             while (i < peers->number - 1) {

                 i++;

                 if (peer[i].current_weight <= 0) {
                     continue;
                 }

                 if (peer[n].current_weight * 1000 / peer[i].current_weight
                     > peer[n].weight * 1000 / peer[i].weight)
                 {
                     return n;
                 }

                 n = i;
             }

             if (peer[i].current_weight > 0) {
                 n = i;
             }

             return n;
         }

         if (reset++) {
             return 0;
         }

         for (i = 0; i < peers->number; i++) {
             peer[i].current_weight = peer[i].weight;
         }
     }
 }


 void
 ngx_http_upstream_free_round_robin_peer(ngx_peer_connection_t *pc, void *data,
     ngx_uint_t state)
 {
     ngx_http_upstream_rr_peer_data_t  *rrp = data;

     time_t                       now;
     ngx_http_upstream_rr_peer_t  *peer;

     ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                    "free rr peer %ui %ui", pc->tries, state);

     if (state == 0 && pc->tries == 0) {
         return;
     }

     /* TODO: NGX_PEER_KEEPALIVE */

     if (rrp->peers->single) {
         pc->tries = 0;
         return;
     }

     peer = &rrp->peers->peer[rrp->current];

     if (state & NGX_PEER_FAILED) {
         now = ngx_time();

         /* ngx_lock_mutex(rrp->peers->mutex); */

         peer->fails++;
         peer->accessed = now;
         peer->checked = now;

         if (peer->max_fails) {
             peer->current_weight -= peer->weight / peer->max_fails;
         }

         ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                        "free rr peer failed: %ui %i",
                        rrp->current, peer->current_weight);

         if (peer->current_weight < 0) {
             peer->current_weight = 0;
         }

         /* ngx_unlock_mutex(rrp->peers->mutex); */

     } else {

         /* mark peer live if check passed */

         if (peer->accessed < peer->checked) {
             peer->fails = 0;
         }
     }

     rrp->current++;

     if (rrp->current >= rrp->peers->number) {
         rrp->current = 0;
     }

     if (pc->tries) {
         pc->tries--;
     }

     /* ngx_unlock_mutex(rrp->peers->mutex); */
 }


 #if (NGX_HTTP_SSL)

 ngx_int_t
 ngx_http_upstream_set_round_robin_peer_session(ngx_peer_connection_t *pc,
     void *data)
 {
     ngx_http_upstream_rr_peer_data_t  *rrp = data;

     ngx_int_t                     rc;
     ngx_ssl_session_t            *ssl_session;
     ngx_http_upstream_rr_peer_t  *peer;

     peer = &rrp->peers->peer[rrp->current];

     /* TODO: threads only mutex */
     /* ngx_lock_mutex(rrp->peers->mutex); */

     ssl_session = peer->ssl_session;

     rc = ngx_ssl_set_session(pc->connection, ssl_session);

     ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                    "set session: %p:%d",
                    ssl_session, ssl_session ? ssl_session->references : 0);

     /* ngx_unlock_mutex(rrp->peers->mutex); */

     return rc;
 }


 void
 ngx_http_upstream_save_round_robin_peer_session(ngx_peer_connection_t *pc,
     void *data)
 {
     ngx_http_upstream_rr_peer_data_t  *rrp = data;

     ngx_ssl_session_t            *old_ssl_session, *ssl_session;
     ngx_http_upstream_rr_peer_t  *peer;

     ssl_session = ngx_ssl_get_session(pc->connection);

     if (ssl_session == NULL) {
         return;
     }

     ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                    "save session: %p:%d", ssl_session, ssl_session->references);

     peer = &rrp->peers->peer[rrp->current];

     /* TODO: threads only mutex */
     /* ngx_lock_mutex(rrp->peers->mutex); */

     old_ssl_session = peer->ssl_session;
     peer->ssl_session = ssl_session;

     /* ngx_unlock_mutex(rrp->peers->mutex); */

     if (old_ssl_session) {

         ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                        "old session: %p:%d",
                        old_ssl_session, old_ssl_session->references);

         /* TODO: may block */

         ngx_ssl_free_session(old_ssl_session);
     }
 }


 static ngx_int_t
 ngx_http_upstream_empty_set_session(ngx_peer_connection_t *pc, void *data)
 {
     return NGX_OK;
 }


 static void
 ngx_http_upstream_empty_save_session(ngx_peer_connection_t *pc, void *data)
 {
     return;
 }

 #endif

	/*
	* Copyright (C) Igor Sysoev
	*/


	#include <ngx_config.h>
	#include <ngx_core.h>
	#include <ngx_http.h>


	static ngx_int_t ngx_http_upstream_cmp_servers(const void *one,
	const void *two);
	static ngx_uint_t
	ngx_http_upstream_get_peer(ngx_http_upstream_rr_peers_t *peers);

	#if (NGX_HTTP_SSL)

	static ngx_int_t ngx_http_upstream_empty_set_session(ngx_peer_connection_t *pc,
	void *data);
	static void ngx_http_upstream_empty_save_session(ngx_peer_connection_t *pc,
	void *data);

	#endif


	ngx_int_t
	ngx_http_upstream_init_round_robin(ngx_conf_t *cf,
	ngx_http_upstream_srv_conf_t *us)
	{
	ngx_url_t u;
	ngx_uint_t i, j, n;
	ngx_http_upstream_server_t *server;
	ngx_http_upstream_rr_peers_t peers, backup;

	us->peer.init = ngx_http_upstream_init_round_robin_peer;

	if (us->servers) {
	server = us->servers->elts;

	n = 0;

	for (i = 0; i < us->servers->nelts; i++) {
	if (server[i].backup) {
	continue;
	}

	n += server[i].naddrs;
	}

	peers = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_rr_peers_t)
	+ sizeof(ngx_http_upstream_rr_peer_t) * (n - 1));
	if (peers == NULL) {
	return NGX_ERROR;
	}

	peers->single = (n == 1);
	peers->number = n;
	peers->name = &us->host;

	n = 0;

	for (i = 0; i < us->servers->nelts; i++) {
	for (j = 0; j < server[i].naddrs; j++) {
	if (server[i].backup) {
	continue;
	}

	peers->peer[n].sockaddr = server[i].addrs[j].sockaddr;
	peers->peer[n].socklen = server[i].addrs[j].socklen;
	peers->peer[n].name = server[i].addrs[j].name;
	peers->peer[n].max_fails = server[i].max_fails;
	peers->peer[n].fail_timeout = server[i].fail_timeout;
	peers->peer[n].down = server[i].down;
	peers->peer[n].weight = server[i].down ? 0 : server[i].weight;
	peers->peer[n].current_weight = peers->peer[n].weight;
	n++;
	}
	}

	us->peer.data = peers;

	ngx_sort(&peers->peer[0], (size_t) n,
	sizeof(ngx_http_upstream_rr_peer_t),
	ngx_http_upstream_cmp_servers);

	/* backup servers */

	n = 0;

	for (i = 0; i < us->servers->nelts; i++) {
	if (!server[i].backup) {
	continue;
	}

	n += server[i].naddrs;
	}

	if (n == 0) {
	return NGX_OK;
	}

	backup = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_rr_peers_t)
	+ sizeof(ngx_http_upstream_rr_peer_t) * (n - 1));
	if (backup == NULL) {
	return NGX_ERROR;
	}

	peers->single = 0;
	backup->single = 0;
	backup->number = n;
	backup->name = &us->host;

	n = 0;

	for (i = 0; i < us->servers->nelts; i++) {
	for (j = 0; j < server[i].naddrs; j++) {
	if (!server[i].backup) {
	continue;
	}

	backup->peer[n].sockaddr = server[i].addrs[j].sockaddr;
	backup->peer[n].socklen = server[i].addrs[j].socklen;
	backup->peer[n].name = server[i].addrs[j].name;
	backup->peer[n].weight = server[i].weight;
	backup->peer[n].current_weight = server[i].weight;
	backup->peer[n].max_fails = server[i].max_fails;
	backup->peer[n].fail_timeout = server[i].fail_timeout;
	backup->peer[n].down = server[i].down;
	n++;
	}
	}

	peers->next = backup;

	ngx_sort(&backup->peer[0], (size_t) n,
	sizeof(ngx_http_upstream_rr_peer_t),
	ngx_http_upstream_cmp_servers);

	return NGX_OK;
	}


	/* an upstream implicitly defined by proxy_pass, etc. */

	if (us->port == 0 && us->default_port == 0) {
	ngx_log_error(NGX_LOG_EMERG, cf->log, 0,
	"no port in upstream \"%V\" in %s:%ui",
	&us->host, us->file_name, us->line);
	return NGX_ERROR;
	}

	ngx_memzero(&u, sizeof(ngx_url_t));

	u.host = us->host;
	u.port = (in_port_t) (us->port ? us->port : us->default_port);

	if (ngx_inet_resolve_host(cf->pool, &u) != NGX_OK) {
	if (u.err) {
	ngx_log_error(NGX_LOG_EMERG, cf->log, 0,
	"%s in upstream \"%V\" in %s:%ui",
	u.err, &us->host, us->file_name, us->line);
	}

	return NGX_ERROR;
	}

	n = u.naddrs;

	peers = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_rr_peers_t)
	+ sizeof(ngx_http_upstream_rr_peer_t) * (n - 1));
	if (peers == NULL) {
	return NGX_ERROR;
	}

	peers->single = (n == 1);
	peers->number = n;
	peers->name = &us->host;

	for (i = 0; i < u.naddrs; i++) {
	peers->peer[i].sockaddr = u.addrs[i].sockaddr;
	peers->peer[i].socklen = u.addrs[i].socklen;
	peers->peer[i].name = u.addrs[i].name;
	peers->peer[i].weight = 1;
	peers->peer[i].current_weight = 1;
	peers->peer[i].max_fails = 1;
	peers->peer[i].fail_timeout = 10;
	}

	us->peer.data = peers;

	/* implicitly defined upstream has no backup servers */

	return NGX_OK;
	}


	static ngx_int_t
	ngx_http_upstream_cmp_servers(const void one, const void two)
	{
	ngx_http_upstream_rr_peer_t first, second;

	first = (ngx_http_upstream_rr_peer_t *) one;
	second = (ngx_http_upstream_rr_peer_t *) two;

	return (first->weight < second->weight);
	}


	ngx_int_t
	ngx_http_upstream_init_round_robin_peer(ngx_http_request_t *r,
	ngx_http_upstream_srv_conf_t *us)
	{
	ngx_uint_t n;
	ngx_http_upstream_rr_peer_data_t *rrp;

	rrp = r->upstream->peer.data;

	if (rrp == NULL) {
	rrp = ngx_palloc(r->pool, sizeof(ngx_http_upstream_rr_peer_data_t));
	if (rrp == NULL) {
	return NGX_ERROR;
	}

	r->upstream->peer.data = rrp;
	}

	rrp->peers = us->peer.data;
	rrp->current = 0;

	n = rrp->peers->number;

	if (rrp->peers->next && rrp->peers->next->number > n) {
	n = rrp->peers->next->number;
	}

	if (n <= 8 * sizeof(uintptr_t)) {
	rrp->tried = &rrp->data;
	rrp->data = 0;

	} else {
	n = (n + (8 * sizeof(uintptr_t) - 1)) / (8 * sizeof(uintptr_t));

	rrp->tried = ngx_pcalloc(r->pool, n * sizeof(uintptr_t));
	if (rrp->tried == NULL) {
	return NGX_ERROR;
	}
	}

	r->upstream->peer.get = ngx_http_upstream_get_round_robin_peer;
	r->upstream->peer.free = ngx_http_upstream_free_round_robin_peer;
	r->upstream->peer.tries = rrp->peers->number;
	#if (NGX_HTTP_SSL)
	r->upstream->peer.set_session =
	ngx_http_upstream_set_round_robin_peer_session;
	r->upstream->peer.save_session =
	ngx_http_upstream_save_round_robin_peer_session;
	#endif

	return NGX_OK;
	}


	ngx_int_t
	ngx_http_upstream_create_round_robin_peer(ngx_http_request_t *r,
	ngx_http_upstream_resolved_t *ur)
	{
	u_char *p;
	size_t len;
	ngx_uint_t i, n;
	struct sockaddr_in *sin;
	ngx_http_upstream_rr_peers_t *peers;
	ngx_http_upstream_rr_peer_data_t *rrp;

	rrp = r->upstream->peer.data;

	if (rrp == NULL) {
	rrp = ngx_palloc(r->pool, sizeof(ngx_http_upstream_rr_peer_data_t));
	if (rrp == NULL) {
	return NGX_ERROR;
	}

	r->upstream->peer.data = rrp;
	}

	peers = ngx_pcalloc(r->pool, sizeof(ngx_http_upstream_rr_peers_t)
	+ sizeof(ngx_http_upstream_rr_peer_t) * (ur->naddrs - 1));
	if (peers == NULL) {
	return NGX_ERROR;
	}

	peers->single = (ur->naddrs == 1);
	peers->number = ur->naddrs;
	peers->name = &ur->host;

	if (ur->sockaddr) {
	peers->peer[0].sockaddr = ur->sockaddr;
	peers->peer[0].socklen = ur->socklen;
	peers->peer[0].name = ur->host;
	peers->peer[0].weight = 1;
	peers->peer[0].current_weight = 1;
	peers->peer[0].max_fails = 1;
	peers->peer[0].fail_timeout = 10;

	} else {

	for (i = 0; i < ur->naddrs; i++) {

	len = NGX_INET_ADDRSTRLEN + sizeof(":65536") - 1;

	p = ngx_pnalloc(r->pool, len);
	if (p == NULL) {
	return NGX_ERROR;
	}

	len = ngx_inet_ntop(AF_INET, &ur->addrs[i], p, NGX_INET_ADDRSTRLEN);
	len = ngx_sprintf(&p[len], ":%d", ur->port) - p;

	sin = ngx_pcalloc(r->pool, sizeof(struct sockaddr_in));
	if (sin == NULL) {
	return NGX_ERROR;
	}

	sin->sin_family = AF_INET;
	sin->sin_port = htons(ur->port);
	sin->sin_addr.s_addr = ur->addrs[i];

	peers->peer[i].sockaddr = (struct sockaddr *) sin;
	peers->peer[i].socklen = sizeof(struct sockaddr_in);
	peers->peer[i].name.len = len;
	peers->peer[i].name.data = p;
	peers->peer[i].weight = 1;
	peers->peer[i].current_weight = 1;
	peers->peer[i].max_fails = 1;
	peers->peer[i].fail_timeout = 10;
	}
	}

	rrp->peers = peers;
	rrp->current = 0;

	if (rrp->peers->number <= 8 * sizeof(uintptr_t)) {
	rrp->tried = &rrp->data;
	rrp->data = 0;

	} else {
	n = (rrp->peers->number + (8 * sizeof(uintptr_t) - 1))
	/ (8 * sizeof(uintptr_t));

	rrp->tried = ngx_pcalloc(r->pool, n * sizeof(uintptr_t));
	if (rrp->tried == NULL) {
	return NGX_ERROR;
	}
	}

	r->upstream->peer.get = ngx_http_upstream_get_round_robin_peer;
	r->upstream->peer.free = ngx_http_upstream_free_round_robin_peer;
	r->upstream->peer.tries = rrp->peers->number;
	#if (NGX_HTTP_SSL)
	r->upstream->peer.set_session = ngx_http_upstream_empty_set_session;
	r->upstream->peer.save_session = ngx_http_upstream_empty_save_session;
	#endif

	return NGX_OK;
	}


	ngx_int_t
	ngx_http_upstream_get_round_robin_peer(ngx_peer_connection_t pc, void data)
	{
	ngx_http_upstream_rr_peer_data_t *rrp = data;

	time_t now;
	uintptr_t m;
	ngx_int_t rc;
	ngx_uint_t i, n;
	ngx_connection_t *c;
	ngx_http_upstream_rr_peer_t *peer;
	ngx_http_upstream_rr_peers_t *peers;

	ngx_log_debug1(NGX_LOG_DEBUG_HTTP, pc->log, 0,
	"get rr peer, try: %ui", pc->tries);

	now = ngx_time();

	/* ngx_lock_mutex(rrp->peers->mutex); */

	if (rrp->peers->last_cached) {

	/* cached connection */

	c = rrp->peers->cached[rrp->peers->last_cached];
	rrp->peers->last_cached--;

	/* ngx_unlock_mutex(ppr->peers->mutex); */

	#if (NGX_THREADS)
	c->read->lock = c->read->own_lock;
	c->write->lock = c->write->own_lock;
	#endif

	pc->connection = c;
	pc->cached = 1;

	return NGX_OK;
	}

	pc->cached = 0;
	pc->connection = NULL;

	if (rrp->peers->single) {
	peer = &rrp->peers->peer[0];

	} else {

	/* there are several peers */

	if (pc->tries == rrp->peers->number) {

	/* it's a first try - get a current peer */

	i = pc->tries;

	for ( ;; ) {
	rrp->current = ngx_http_upstream_get_peer(rrp->peers);

	ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
	"get rr peer, current: %ui %i",
	rrp->current,
	rrp->peers->peer[rrp->current].current_weight);

	n = rrp->current / (8 * sizeof(uintptr_t));
	m = (uintptr_t) 1 << rrp->current % (8 * sizeof(uintptr_t));

	if (!(rrp->tried[n] & m)) {
	peer = &rrp->peers->peer[rrp->current];

	if (!peer->down) {

	if (peer->max_fails == 0
	\|\| peer->fails < peer->max_fails)
	{
	break;
	}

	if (now - peer->checked > peer->fail_timeout) {
	peer->checked = now;
	break;
	}

	peer->current_weight = 0;

	} else {
	rrp->tried[n] \|= m;
	}

	pc->tries--;
	}

	if (pc->tries == 0) {
	goto failed;
	}

	if (--i == 0) {
	ngx_log_error(NGX_LOG_ALERT, pc->log, 0,
	"round robin upstream stuck on %ui tries",
	pc->tries);
	goto failed;
	}
	}

	peer->current_weight--;

	} else {

	i = pc->tries;

	for ( ;; ) {
	n = rrp->current / (8 * sizeof(uintptr_t));
	m = (uintptr_t) 1 << rrp->current % (8 * sizeof(uintptr_t));

	if (!(rrp->tried[n] & m)) {

	peer = &rrp->peers->peer[rrp->current];

	if (!peer->down) {

	if (peer->max_fails == 0
	\|\| peer->fails < peer->max_fails)
	{
	break;
	}

	if (now - peer->checked > peer->fail_timeout) {
	peer->checked = now;
	break;
	}

	peer->current_weight = 0;

	} else {
	rrp->tried[n] \|= m;
	}

	pc->tries--;
	}

	rrp->current++;

	if (rrp->current >= rrp->peers->number) {
	rrp->current = 0;
	}

	if (pc->tries == 0) {
	goto failed;
	}

	if (--i == 0) {
	ngx_log_error(NGX_LOG_ALERT, pc->log, 0,
	"round robin upstream stuck on %ui tries",
	pc->tries);
	goto failed;
	}
	}

	peer->current_weight--;
	}

	rrp->tried[n] \|= m;
	}

	pc->sockaddr = peer->sockaddr;
	pc->socklen = peer->socklen;
	pc->name = &peer->name;

	/* ngx_unlock_mutex(rrp->peers->mutex); */

	if (pc->tries == 1 && rrp->peers->next) {
	pc->tries += rrp->peers->next->number;

	n = rrp->peers->next->number / (8 * sizeof(uintptr_t)) + 1;
	for (i = 0; i < n; i++) {
	rrp->tried[i] = 0;
	}
	}

	return NGX_OK;

	failed:

	peers = rrp->peers;

	if (peers->next) {

	/* ngx_unlock_mutex(peers->mutex); */

	ngx_log_debug0(NGX_LOG_DEBUG_HTTP, pc->log, 0, "backup servers");

	rrp->peers = peers->next;
	pc->tries = rrp->peers->number;

	n = rrp->peers->number / (8 * sizeof(uintptr_t)) + 1;
	for (i = 0; i < n; i++) {
	rrp->tried[i] = 0;
	}

	rc = ngx_http_upstream_get_round_robin_peer(pc, rrp);

	if (rc != NGX_BUSY) {
	return rc;
	}

	/* ngx_lock_mutex(peers->mutex); */
	}

	/* all peers failed, mark them as live for quick recovery */

	for (i = 0; i < peers->number; i++) {
	peers->peer[i].fails = 0;
	}

	/* ngx_unlock_mutex(peers->mutex); */

	pc->name = peers->name;

	return NGX_BUSY;
	}


	static ngx_uint_t
	ngx_http_upstream_get_peer(ngx_http_upstream_rr_peers_t *peers)
	{
	ngx_uint_t i, n, reset = 0;
	ngx_http_upstream_rr_peer_t *peer;

	peer = &peers->peer[0];

	for ( ;; ) {

	for (i = 0; i < peers->number; i++) {

	if (peer[i].current_weight <= 0) {
	continue;
	}

	n = i;

	while (i < peers->number - 1) {

	i++;

	if (peer[i].current_weight <= 0) {
	continue;
	}

	if (peer[n].current_weight * 1000 / peer[i].current_weight
	> peer[n].weight * 1000 / peer[i].weight)
	{
	return n;
	}

	n = i;
	}

	if (peer[i].current_weight > 0) {
	n = i;
	}

	return n;
	}

	if (reset++) {
	return 0;
	}

	for (i = 0; i < peers->number; i++) {
	peer[i].current_weight = peer[i].weight;
	}
	}
	}


	void
	ngx_http_upstream_free_round_robin_peer(ngx_peer_connection_t pc, void data,
	ngx_uint_t state)
	{
	ngx_http_upstream_rr_peer_data_t *rrp = data;

	time_t now;
	ngx_http_upstream_rr_peer_t *peer;

	ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
	"free rr peer %ui %ui", pc->tries, state);

	if (state == 0 && pc->tries == 0) {
	return;
	}

	/* TODO: NGX_PEER_KEEPALIVE */

	if (rrp->peers->single) {
	pc->tries = 0;
	return;
	}

	peer = &rrp->peers->peer[rrp->current];

	if (state & NGX_PEER_FAILED) {
	now = ngx_time();

	/* ngx_lock_mutex(rrp->peers->mutex); */

	peer->fails++;
	peer->accessed = now;
	peer->checked = now;

	if (peer->max_fails) {
	peer->current_weight -= peer->weight / peer->max_fails;
	}

	ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
	"free rr peer failed: %ui %i",
	rrp->current, peer->current_weight);

	if (peer->current_weight < 0) {
	peer->current_weight = 0;
	}

	/* ngx_unlock_mutex(rrp->peers->mutex); */

	} else {

	/* mark peer live if check passed */

	if (peer->accessed < peer->checked) {
	peer->fails = 0;
	}
	}

	rrp->current++;

	if (rrp->current >= rrp->peers->number) {
	rrp->current = 0;
	}

	if (pc->tries) {
	pc->tries--;
	}

	/* ngx_unlock_mutex(rrp->peers->mutex); */
	}


	#if (NGX_HTTP_SSL)

	ngx_int_t
	ngx_http_upstream_set_round_robin_peer_session(ngx_peer_connection_t *pc,
	void *data)
	{
	ngx_http_upstream_rr_peer_data_t *rrp = data;

	ngx_int_t rc;
	ngx_ssl_session_t *ssl_session;
	ngx_http_upstream_rr_peer_t *peer;

	peer = &rrp->peers->peer[rrp->current];

	/* TODO: threads only mutex */
	/* ngx_lock_mutex(rrp->peers->mutex); */

	ssl_session = peer->ssl_session;

	rc = ngx_ssl_set_session(pc->connection, ssl_session);

	ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
	"set session: %p:%d",
	ssl_session, ssl_session ? ssl_session->references : 0);

	/* ngx_unlock_mutex(rrp->peers->mutex); */

	return rc;
	}


	void
	ngx_http_upstream_save_round_robin_peer_session(ngx_peer_connection_t *pc,
	void *data)
	{
	ngx_http_upstream_rr_peer_data_t *rrp = data;

	ngx_ssl_session_t old_ssl_session, ssl_session;
	ngx_http_upstream_rr_peer_t *peer;

	ssl_session = ngx_ssl_get_session(pc->connection);

	if (ssl_session == NULL) {
	return;
	}

	ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
	"save session: %p:%d", ssl_session, ssl_session->references);

	peer = &rrp->peers->peer[rrp->current];

	/* TODO: threads only mutex */
	/* ngx_lock_mutex(rrp->peers->mutex); */

	old_ssl_session = peer->ssl_session;
	peer->ssl_session = ssl_session;

	/* ngx_unlock_mutex(rrp->peers->mutex); */

	if (old_ssl_session) {

	ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
	"old session: %p:%d",
	old_ssl_session, old_ssl_session->references);

	/* TODO: may block */

	ngx_ssl_free_session(old_ssl_session);
	}
	}


	static ngx_int_t
	ngx_http_upstream_empty_set_session(ngx_peer_connection_t pc, void data)
	{
	return NGX_OK;
	}


	static void
	ngx_http_upstream_empty_save_session(ngx_peer_connection_t pc, void data)
	{
	return;
	}

	#endif