Merge of r4622, r4623: balancing changes.

*) Upstream: smooth weighted round-robin balancing.

   For edge case weights like { 5, 1, 1 } we now produce { a, a, b, a, c, a, a }
   sequence instead of { c, b, a, a, a, a, a } produced previously.

   Algorithm is as follows: on each peer selection we increase current_weight
   of each eligible peer by its weight, select peer with greatest current_weight
   and reduce its current_weight by total number of weight points distributed
   among peers.

   In case of { 5, 1, 1 } weights this gives the following sequence of
   current_weight's:

        a  b  c
        0  0  0  (initial state)

        5  1  1  (a selected)
       -2  1  1

        3  2  2  (a selected)
       -4  2  2

        1  3  3  (b selected)
        1 -4  3

        6 -3  4  (a selected)
       -1 -3  4

        4 -2  5  (c selected)
        4 -2 -2

        9 -1 -1  (a selected)
        2 -1 -1

        7  0  0  (a selected)
        0  0  0

   To preserve weight reduction in case of failures the effective_weight
   variable was introduced, which usually matches peer's weight, but is
   reduced temporarily on peer failures.

   This change also fixes loop with backup servers and proxy_next_upstream
   http_404 (ticket #47), and skipping alive upstreams in some cases if there
   are multiple dead ones (ticket #64).

*) Upstream: fixed ip_hash rebalancing with the "down" flag.

   Due to weight being set to 0 for down peers, order of peers after sorting
   wasn't the same as without the "down" flag (with down peers at the end),
   resulting in client rebalancing for clients on other servers.  The only
   rebalancing which should happen after adding "down" to a server is one
   for clients on the server.

   The problem was introduced in r1377 (which fixed endless loop by setting
   weight to 0 for down servers).  The loop is no longer possible with new
   smooth algorithm, so preserving original weight is safe.

diff --git a/src/http/ngx_http_upstream_round_robin.c b/src/http/ngx_http_upstream_round_robin.c
index f0fac87369927275e3ba169c6e71533836fbb40b..214de7b74fce5b383b1b1d89ebf7e7f29204da23 100644 (file)
--- a/src/http/ngx_http_upstream_round_robin.c
+++ b/src/http/ngx_http_upstream_round_robin.c
@@ -12,8 +12,8 @@
 
 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);
+static ngx_http_upstream_rr_peer_t *ngx_http_upstream_get_peer(
+    ngx_http_upstream_rr_peer_data_t *rrp);
 
 #if (NGX_HTTP_SSL)
 
@@ -80,8 +80,9 @@ ngx_http_upstream_init_round_robin(ngx_conf_t *cf,
                 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;
+                peers->peer[n].weight = server[i].weight;
+                peers->peer[n].effective_weight = server[i].weight;
+                peers->peer[n].current_weight = 0;
                 n++;
             }
         }
@@ -131,7 +132,8 @@ ngx_http_upstream_init_round_robin(ngx_conf_t *cf,
                 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].effective_weight = server[i].weight;
+                backup->peer[n].current_weight = 0;
                 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;
@@ -190,7 +192,8 @@ ngx_http_upstream_init_round_robin(ngx_conf_t *cf,
         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].effective_weight = 1;
+        peers->peer[i].current_weight = 0;
         peers->peer[i].max_fails = 1;
         peers->peer[i].fail_timeout = 10;
     }
@@ -306,7 +309,8 @@ ngx_http_upstream_create_round_robin_peer(ngx_http_request_t *r,
         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].effective_weight = 1;
+        peers->peer[0].current_weight = 0;
         peers->peer[0].max_fails = 1;
         peers->peer[0].fail_timeout = 10;
 
@@ -338,7 +342,8 @@ ngx_http_upstream_create_round_robin_peer(ngx_http_request_t *r,
             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].effective_weight = 1;
+            peers->peer[i].current_weight = 0;
             peers->peer[i].max_fails = 1;
             peers->peer[i].fail_timeout = 10;
         }
@@ -378,8 +383,6 @@ 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;
@@ -389,8 +392,6 @@ ngx_http_upstream_get_round_robin_peer(ngx_peer_connection_t *pc, void *data)
     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) {
@@ -423,118 +424,15 @@ ngx_http_upstream_get_round_robin_peer(ngx_peer_connection_t *pc, void *data)
 
         /* 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;
-                        }
+        peer = ngx_http_upstream_get_peer(rrp);
 
-                        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--;
+        if (peer == NULL) {
+            goto failed;
         }
 
-        rrp->tried[n] |= m;
+        ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
+                       "get rr peer, current: %ui %i",
+                       rrp->current, peer->current_weight);
     }
 
     pc->sockaddr = peer->sockaddr;
@@ -545,11 +443,6 @@ ngx_http_upstream_get_round_robin_peer(ngx_peer_connection_t *pc, void *data)
 
     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;
@@ -595,56 +488,71 @@ failed:
 }
 
 
-static ngx_uint_t
-ngx_http_upstream_get_peer(ngx_http_upstream_rr_peers_t *peers)
+static ngx_http_upstream_rr_peer_t *
+ngx_http_upstream_get_peer(ngx_http_upstream_rr_peer_data_t *rrp)
 {
-    ngx_uint_t                    i, n, reset = 0;
-    ngx_http_upstream_rr_peer_t  *peer;
+    time_t                        now;
+    uintptr_t                     m;
+    ngx_int_t                     total;
+    ngx_uint_t                    i, n;
+    ngx_http_upstream_rr_peer_t  *peer, *best;
 
-    peer = &peers->peer[0];
+    now = ngx_time();
 
-    for ( ;; ) {
+    best = NULL;
+    total = 0;
 
-        for (i = 0; i < peers->number; i++) {
+    for (i = 0; i < rrp->peers->number; i++) {
 
-            if (peer[i].current_weight <= 0) {
-                continue;
-            }
+        n = i / (8 * sizeof(uintptr_t));
+        m = (uintptr_t) 1 << i % (8 * sizeof(uintptr_t));
 
-            n = i;
-
-            while (i < peers->number - 1) {
-
-                i++;
+        if (rrp->tried[n] & m) {
+            continue;
+        }
 
-                if (peer[i].current_weight <= 0) {
-                    continue;
-                }
+        peer = &rrp->peers->peer[i];
 
-                if (peer[n].current_weight * 1000 / peer[i].current_weight
-                    > peer[n].weight * 1000 / peer[i].weight)
-                {
-                    return n;
-                }
+        if (peer->down) {
+            continue;
+        }
 
-                n = i;
-            }
+        if (peer->max_fails
+            && peer->fails >= peer->max_fails
+            && now - peer->checked <= peer->fail_timeout)
+        {
+            continue;
+        }
 
-            if (peer[i].current_weight > 0) {
-                n = i;
-            }
+        peer->current_weight += peer->effective_weight;
+        total += peer->effective_weight;
 
-            return n;
+        if (peer->effective_weight < peer->weight) {
+            peer->effective_weight++;
         }
 
-        if (reset++) {
-            return 0;
+        if (best == NULL || peer->current_weight > best->current_weight) {
+            best = peer;
         }
+    }
 
-        for (i = 0; i < peers->number; i++) {
-            peer[i].current_weight = peer[i].weight;
-        }
+    if (best == NULL) {
+        return NULL;
     }
+
+    i = best - &rrp->peers->peer[0];
+
+    rrp->current = i;
+
+    n = i / (8 * sizeof(uintptr_t));
+    m = (uintptr_t) 1 << i % (8 * sizeof(uintptr_t));
+
+    rrp->tried[n] |= m;
+
+    best->current_weight -= total;
+    best->checked = now;
+
+    return best;
 }
 
 
@@ -683,15 +591,15 @@ ngx_http_upstream_free_round_robin_peer(ngx_peer_connection_t *pc, void *data,
         peer->checked = now;
 
         if (peer->max_fails) {
-            peer->current_weight -= peer->weight / peer->max_fails;
+            peer->effective_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);
+                       rrp->current, peer->effective_weight);
 
-        if (peer->current_weight < 0) {
-            peer->current_weight = 0;
+        if (peer->effective_weight < 0) {
+            peer->effective_weight = 0;
         }
 
         /* ngx_unlock_mutex(rrp->peers->mutex); */
@@ -705,12 +613,6 @@ ngx_http_upstream_free_round_robin_peer(ngx_peer_connection_t *pc, void *data,
         }
     }
 
-    rrp->current++;
-
-    if (rrp->current >= rrp->peers->number) {
-        rrp->current = 0;
-    }
-
     if (pc->tries) {
         pc->tries--;
     }

diff --git a/src/http/ngx_http_upstream_round_robin.h b/src/http/ngx_http_upstream_round_robin.h
index 4b70f2f5bac709f5200c1bd97794055cae207973..4de3caea1b069f068f14212f788716e38e0032c4 100644 (file)
--- a/src/http/ngx_http_upstream_round_robin.h
+++ b/src/http/ngx_http_upstream_round_robin.h
@@ -20,6 +20,7 @@ typedef struct {
     ngx_str_t                       name;
 
     ngx_int_t                       current_weight;
+    ngx_int_t                       effective_weight;
     ngx_int_t                       weight;
 
     ngx_uint_t                      fails;