Upstream hash: limited number of tries in consistent case.

While this may result in non-ideal distribution of requests if nginx
won't be able to select a server in a reasonable number of attempts,
this still looks better than severe performance degradation observed
if there is no limit and there are many points configured (ticket #1030).
This is also in line with what we do for other hash balancing methods.

diff --git a/src/http/modules/ngx_http_upstream_hash_module.c b/src/http/modules/ngx_http_upstream_hash_module.c
index 6c28c6456e97b1fe3ec723cddf8ae9f54a2dab78..78e672c0f261907b58ef5941ceec10a716d7db85 100644 (file)
--- a/src/http/modules/ngx_http_upstream_hash_module.c
+++ b/src/http/modules/ngx_http_upstream_hash_module.c
@@ -503,6 +503,11 @@ ngx_http_upstream_get_chash_peer(ngx_peer_connection_t *pc, void *data)
 
     ngx_http_upstream_rr_peers_wlock(hp->rrp.peers);
 
+    if (hp->tries > 20 || hp->rrp.peers->single) {
+        ngx_http_upstream_rr_peers_unlock(hp->rrp.peers);
+        return hp->get_rr_peer(pc, &hp->rrp);
+    }
+
     pc->cached = 0;
     pc->connection = NULL;
 
@@ -577,10 +582,9 @@ ngx_http_upstream_get_chash_peer(ngx_peer_connection_t *pc, void *data)
         hp->hash++;
         hp->tries++;
 
-        if (hp->tries >= points->number) {
-            pc->name = hp->rrp.peers->name;
+        if (hp->tries > 20) {
             ngx_http_upstream_rr_peers_unlock(hp->rrp.peers);
-            return NGX_BUSY;
+            return hp->get_rr_peer(pc, &hp->rrp);
         }
     }
 

diff --git a/src/stream/ngx_stream_upstream_hash_module.c b/src/stream/ngx_stream_upstream_hash_module.c
index cb44fcdad6f0665192a02e8002ad2142efc7917b..413537989679dce6e46475903a1e7bc055261813 100644 (file)
--- a/src/stream/ngx_stream_upstream_hash_module.c
+++ b/src/stream/ngx_stream_upstream_hash_module.c
@@ -505,6 +505,11 @@ ngx_stream_upstream_get_chash_peer(ngx_peer_connection_t *pc, void *data)
 
     ngx_stream_upstream_rr_peers_wlock(hp->rrp.peers);
 
+    if (hp->tries > 20 || hp->rrp.peers->single) {
+        ngx_stream_upstream_rr_peers_unlock(hp->rrp.peers);
+        return hp->get_rr_peer(pc, &hp->rrp);
+    }
+
     pc->connection = NULL;
 
     now = ngx_time();
@@ -578,10 +583,9 @@ ngx_stream_upstream_get_chash_peer(ngx_peer_connection_t *pc, void *data)
         hp->hash++;
         hp->tries++;
 
-        if (hp->tries >= points->number) {
-            pc->name = hp->rrp.peers->name;
+        if (hp->tries > 20) {
             ngx_stream_upstream_rr_peers_unlock(hp->rrp.peers);
-            return NGX_BUSY;
+            return hp->get_rr_peer(pc, &hp->rrp);
         }
     }