diff --git a/auto/modules b/auto/modules
index 7d3216b..ebea302 100644
--- a/auto/modules
+++ b/auto/modules
@@ -345,6 +345,11 @@
     HTTP_SRCS="$HTTP_SRCS $HTTP_UPSTREAM_IP_HASH_SRCS"
 fi
 
+if [ $HTTP_UPSTREAM_LEAST_CONN = YES ]; then
+    HTTP_MODULES="$HTTP_MODULES $HTTP_UPSTREAM_LEAST_CONN_MODULE"
+    HTTP_SRCS="$HTTP_SRCS $HTTP_UPSTREAM_LEAST_CONN_SRCS"
+fi
+
 if [ $HTTP_UPSTREAM_KEEPALIVE = YES ]; then
     HTTP_MODULES="$HTTP_MODULES $HTTP_UPSTREAM_KEEPALIVE_MODULE"
     HTTP_SRCS="$HTTP_SRCS $HTTP_UPSTREAM_KEEPALIVE_SRCS"
diff --git a/auto/options b/auto/options
index 393be40..11f23c6 100644
--- a/auto/options
+++ b/auto/options
@@ -96,6 +96,7 @@
 HTTP_MP4=NO
 HTTP_GZIP_STATIC=NO
 HTTP_UPSTREAM_IP_HASH=YES
+HTTP_UPSTREAM_LEAST_CONN=YES
 HTTP_UPSTREAM_KEEPALIVE=YES
 
 # STUB
@@ -243,6 +244,8 @@
         --without-http_empty_gif_module) HTTP_EMPTY_GIF=NO          ;;
         --without-http_browser_module)   HTTP_BROWSER=NO            ;;
         --without-http_upstream_ip_hash_module) HTTP_UPSTREAM_IP_HASH=NO ;;
+        --without-http_upstream_least_conn_module)
+                                         HTTP_UPSTREAM_LEAST_CONN=NO ;;
         --without-http_upstream_keepalive_module) HTTP_UPSTREAM_KEEPALIVE=NO ;;
 
         --with-http_perl_module)         HTTP_PERL=YES              ;;
diff --git a/auto/sources b/auto/sources
index 374ad66..522d722 100644
--- a/auto/sources
+++ b/auto/sources
@@ -479,6 +479,11 @@
 HTTP_UPSTREAM_IP_HASH_SRCS=src/http/modules/ngx_http_upstream_ip_hash_module.c
 
 
+HTTP_UPSTREAM_LEAST_CONN_MODULE=ngx_http_upstream_least_conn_module
+HTTP_UPSTREAM_LEAST_CONN_SRCS=" \
+    src/http/modules/ngx_http_upstream_least_conn_module.c"
+
+
 HTTP_UPSTREAM_KEEPALIVE_MODULE=ngx_http_upstream_keepalive_module
 HTTP_UPSTREAM_KEEPALIVE_SRCS=" \
     src/http/modules/ngx_http_upstream_keepalive_module.c"
diff --git a/src/http/modules/ngx_http_upstream_least_conn_module.c b/src/http/modules/ngx_http_upstream_least_conn_module.c
new file mode 100644
index 0000000..bc9a146
--- /dev/null
+++ b/src/http/modules/ngx_http_upstream_least_conn_module.c
@@ -0,0 +1,404 @@
+
+/*
+ * Copyright (C) Maxim Dounin
+ * Copyright (C) Nginx, Inc.
+ */
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+#include <ngx_http.h>
+
+
+typedef struct {
+    ngx_uint_t                        *conns;
+} ngx_http_upstream_least_conn_conf_t;
+
+
+typedef struct {
+    /* the round robin data must be first */
+    ngx_http_upstream_rr_peer_data_t   rrp;
+
+    ngx_uint_t                        *conns;
+
+    ngx_event_get_peer_pt              get_rr_peer;
+    ngx_event_free_peer_pt             free_rr_peer;
+} ngx_http_upstream_lc_peer_data_t;
+
+
+static ngx_int_t ngx_http_upstream_init_least_conn_peer(ngx_http_request_t *r,
+    ngx_http_upstream_srv_conf_t *us);
+static ngx_int_t ngx_http_upstream_get_least_conn_peer(
+    ngx_peer_connection_t *pc, void *data);
+static void ngx_http_upstream_free_least_conn_peer(ngx_peer_connection_t *pc,
+    void *data, ngx_uint_t state);
+static void *ngx_http_upstream_least_conn_create_conf(ngx_conf_t *cf);
+static char *ngx_http_upstream_least_conn(ngx_conf_t *cf, ngx_command_t *cmd,
+    void *conf);
+
+
+static ngx_command_t  ngx_http_upstream_least_conn_commands[] = {
+
+    { ngx_string("least_conn"),
+      NGX_HTTP_UPS_CONF|NGX_CONF_NOARGS,
+      ngx_http_upstream_least_conn,
+      0,
+      0,
+      NULL },
+
+      ngx_null_command
+};
+
+
+static ngx_http_module_t  ngx_http_upstream_least_conn_module_ctx = {
+    NULL,                                  /* preconfiguration */
+    NULL,                                  /* postconfiguration */
+
+    NULL,                                  /* create main configuration */
+    NULL,                                  /* init main configuration */
+
+    ngx_http_upstream_least_conn_create_conf, /* create server configuration */
+    NULL,                                  /* merge server configuration */
+
+    NULL,                                  /* create location configuration */
+    NULL                                   /* merge location configuration */
+};
+
+
+ngx_module_t  ngx_http_upstream_least_conn_module = {
+    NGX_MODULE_V1,
+    &ngx_http_upstream_least_conn_module_ctx, /* module context */
+    ngx_http_upstream_least_conn_commands, /* module directives */
+    NGX_HTTP_MODULE,                       /* module type */
+    NULL,                                  /* init master */
+    NULL,                                  /* init module */
+    NULL,                                  /* init process */
+    NULL,                                  /* init thread */
+    NULL,                                  /* exit thread */
+    NULL,                                  /* exit process */
+    NULL,                                  /* exit master */
+    NGX_MODULE_V1_PADDING
+};
+
+
+ngx_int_t
+ngx_http_upstream_init_least_conn(ngx_conf_t *cf,
+    ngx_http_upstream_srv_conf_t *us)
+{
+    ngx_uint_t                            n;
+    ngx_http_upstream_rr_peers_t         *peers;
+    ngx_http_upstream_least_conn_conf_t  *lcf;
+
+    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, cf->log, 0,
+                   "init least conn");
+
+    if (ngx_http_upstream_init_round_robin(cf, us) != NGX_OK) {
+        return NGX_ERROR;
+    }
+
+    peers = us->peer.data;
+
+    n = peers->number;
+
+    if (peers->next) {
+        n += peers->next->number;
+    }
+
+    lcf = ngx_http_conf_upstream_srv_conf(us,
+                                          ngx_http_upstream_least_conn_module);
+
+    lcf->conns = ngx_pcalloc(cf->pool, sizeof(ngx_uint_t) * n);
+    if (lcf->conns == NULL) {
+        return NGX_ERROR;
+    }
+
+    us->peer.init = ngx_http_upstream_init_least_conn_peer;
+
+    return NGX_OK;
+}
+
+
+static ngx_int_t
+ngx_http_upstream_init_least_conn_peer(ngx_http_request_t *r,
+    ngx_http_upstream_srv_conf_t *us)
+{
+    ngx_int_t                             rc;
+    ngx_http_upstream_lc_peer_data_t     *lcp;
+    ngx_http_upstream_least_conn_conf_t  *lcf;
+
+    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
+                   "init least conn peer");
+
+    lcf = ngx_http_conf_upstream_srv_conf(us,
+                                          ngx_http_upstream_least_conn_module);
+
+    lcp = ngx_palloc(r->pool, sizeof(ngx_http_upstream_lc_peer_data_t));
+    if (lcp == NULL) {
+        return NGX_ERROR;
+    }
+
+    lcp->conns = lcf->conns;
+
+    r->upstream->peer.data = &lcp->rrp;
+
+    rc = ngx_http_upstream_init_round_robin_peer(r, us);
+
+    if (ngx_http_upstream_init_round_robin_peer(r, us) != NGX_OK) {
+        return NGX_ERROR;
+    }
+
+    r->upstream->peer.get = ngx_http_upstream_get_least_conn_peer;
+    r->upstream->peer.free = ngx_http_upstream_free_least_conn_peer;
+
+    lcp->get_rr_peer = ngx_http_upstream_get_round_robin_peer;
+    lcp->free_rr_peer = ngx_http_upstream_free_round_robin_peer;
+
+    return NGX_OK;
+}
+
+
+static ngx_int_t
+ngx_http_upstream_get_least_conn_peer(ngx_peer_connection_t *pc, void *data)
+{
+    ngx_http_upstream_lc_peer_data_t  *lcp = data;
+
+    time_t                         now;
+    uintptr_t                      m;
+    ngx_int_t                      rc, total;
+    ngx_uint_t                     i, n, p, many;
+    ngx_http_upstream_rr_peer_t   *peer, *best;
+    ngx_http_upstream_rr_peers_t  *peers;
+
+    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, pc->log, 0,
+                   "get least conn peer, try: %ui", pc->tries);
+
+    if (lcp->rrp.peers->single) {
+        return lcp->get_rr_peer(pc, &lcp->rrp);
+    }
+
+    pc->cached = 0;
+    pc->connection = NULL;
+
+    now = ngx_time();
+
+    peers = lcp->rrp.peers;
+
+    best = NULL;
+    total = 0;
+
+#if (NGX_SUPPRESS_WARN)
+    many = 0;
+    p = 0;
+#endif
+
+    for (i = 0; i < peers->number; i++) {
+
+        n = i / (8 * sizeof(uintptr_t));
+        m = (uintptr_t) 1 << i % (8 * sizeof(uintptr_t));
+
+        if (lcp->rrp.tried[n] & m) {
+            continue;
+        }
+
+        peer = &peers->peer[i];
+
+        if (peer->down) {
+            continue;
+        }
+
+        if (peer->max_fails
+            && peer->fails >= peer->max_fails
+            && now - peer->checked <= peer->fail_timeout)
+        {
+            continue;
+        }
+
+        /*
+         * select peer with least number of connections; if there are
+         * multiple peers with the same number of connections, select
+         * based on round-robin
+         */
+
+        if (best == NULL
+            || lcp->conns[i] * best->weight < lcp->conns[p] * peer->weight)
+        {
+            best = peer;
+            many = 0;
+            p = i;
+
+        } else if (lcp->conns[i] * best->weight
+                   == lcp->conns[p] * peer->weight)
+        {
+            many = 1;
+        }
+    }
+
+    if (best == NULL) {
+        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, pc->log, 0,
+                       "get least conn peer, no peer found");
+
+        goto failed;
+    }
+
+    if (many) {
+        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, pc->log, 0,
+                       "get least conn peer, many");
+
+        for (i = p; i < peers->number; i++) {
+
+            n = i / (8 * sizeof(uintptr_t));
+            m = (uintptr_t) 1 << i % (8 * sizeof(uintptr_t));
+
+            if (lcp->rrp.tried[n] & m) {
+                continue;
+            }
+
+            peer = &peers->peer[i];
+
+            if (peer->down) {
+                continue;
+            }
+
+            if (lcp->conns[i] * best->weight != lcp->conns[p] * peer->weight) {
+                continue;
+            }
+
+            if (peer->max_fails
+                && peer->fails >= peer->max_fails
+                && now - peer->checked <= peer->fail_timeout)
+            {
+                continue;
+            }
+
+            peer->current_weight += peer->effective_weight;
+            total += peer->effective_weight;
+
+            if (peer->effective_weight < peer->weight) {
+                peer->effective_weight++;
+            }
+
+            if (peer->current_weight > best->current_weight) {
+                best = peer;
+                p = i;
+            }
+        }
+    }
+
+    best->current_weight -= total;
+    best->checked = now;
+
+    pc->sockaddr = best->sockaddr;
+    pc->socklen = best->socklen;
+    pc->name = &best->name;
+
+    lcp->rrp.current = p;
+
+    n = p / (8 * sizeof(uintptr_t));
+    m = (uintptr_t) 1 << p % (8 * sizeof(uintptr_t));
+
+    lcp->rrp.tried[n] |= m;
+    lcp->conns[p]++;
+
+    if (pc->tries == 1 && peers->next) {
+        pc->tries += peers->next->number;
+    }
+
+    return NGX_OK;
+
+failed:
+
+    if (peers->next) {
+        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, pc->log, 0,
+                       "get least conn peer, backup servers");
+
+        lcp->conns += peers->number;
+
+        lcp->rrp.peers = peers->next;
+        pc->tries = lcp->rrp.peers->number;
+
+        n = lcp->rrp.peers->number / (8 * sizeof(uintptr_t)) + 1;
+        for (i = 0; i < n; i++) {
+             lcp->rrp.tried[i] = 0;
+        }
+
+        rc = ngx_http_upstream_get_least_conn_peer(pc, lcp);
+
+        if (rc != NGX_BUSY) {
+            return rc;
+        }
+    }
+
+    /* all peers failed, mark them as live for quick recovery */
+
+    for (i = 0; i < peers->number; i++) {
+        peers->peer[i].fails = 0;
+    }
+
+    pc->name = peers->name;
+
+    return NGX_BUSY;
+}
+
+
+static void
+ngx_http_upstream_free_least_conn_peer(ngx_peer_connection_t *pc,
+    void *data, ngx_uint_t state)
+{
+    ngx_http_upstream_lc_peer_data_t  *lcp = data;
+
+    ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
+                   "free least conn peer %ui %ui", pc->tries, state);
+
+    if (lcp->rrp.peers->single) {
+        return lcp->free_rr_peer(pc, &lcp->rrp, state);
+    }
+
+    if (state == 0 && pc->tries == 0) {
+        return;
+    }
+
+    lcp->conns[lcp->rrp.current]--;
+
+    return lcp->free_rr_peer(pc, &lcp->rrp, state);
+}
+
+
+static void *
+ngx_http_upstream_least_conn_create_conf(ngx_conf_t *cf)
+{
+    ngx_http_upstream_least_conn_conf_t  *conf;
+
+    conf = ngx_pcalloc(cf->pool,
+                       sizeof(ngx_http_upstream_least_conn_conf_t));
+    if (conf == NULL) {
+        return NULL;
+    }
+
+    /*
+     * set by ngx_pcalloc():
+     *
+     *     conf->conns = NULL;
+     */
+
+    return conf;
+}
+
+
+static char *
+ngx_http_upstream_least_conn(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
+{
+    ngx_http_upstream_srv_conf_t  *uscf;
+
+    uscf = ngx_http_conf_get_module_srv_conf(cf, ngx_http_upstream_module);
+
+    uscf->peer.init_upstream = ngx_http_upstream_init_least_conn;
+
+    uscf->flags = NGX_HTTP_UPSTREAM_CREATE
+                  |NGX_HTTP_UPSTREAM_WEIGHT
+                  |NGX_HTTP_UPSTREAM_MAX_FAILS
+                  |NGX_HTTP_UPSTREAM_FAIL_TIMEOUT
+                  |NGX_HTTP_UPSTREAM_DOWN
+                  |NGX_HTTP_UPSTREAM_BACKUP;
+
+    return NGX_CONF_OK;
+}