From 624fbe94a23e183dc356f9c3e696a816cb67acc2 Mon Sep 17 00:00:00 2001 From: Maxim Dounin Date: Thu, 18 Aug 2011 16:52:38 +0000 Subject: [PATCH] Fixing cpu hog with all upstream servers marked "down". The following configuration causes nginx to hog cpu due to infinite loop in ngx_http_upstream_get_peer(): upstream backend { server 127.0.0.1:8080 down; server 127.0.0.1:8080 down; } server { ... location / { proxy_pass http://backend; } } Make sure we don't loop infinitely in ngx_http_upstream_get_peer() but stop after resetting peer weights once. Return 0 if we are stuck. This is guaranteed to work as peer 0 always exists, and eventually ngx_http_upstream_get_round_robin_peer() will do the right thing falling back to backup servers or returning NGX_BUSY. --- src/http/ngx_http_upstream_round_robin.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/src/http/ngx_http_upstream_round_robin.c b/src/http/ngx_http_upstream_round_robin.c index de34b2884..c15790aa0 100644 --- a/src/http/ngx_http_upstream_round_robin.c +++ b/src/http/ngx_http_upstream_round_robin.c @@ -585,7 +585,7 @@ failed: static ngx_uint_t ngx_http_upstream_get_peer(ngx_http_upstream_rr_peers_t *peers) { - ngx_uint_t i, n; + ngx_uint_t i, n, reset = 0; ngx_http_upstream_rr_peer_t *peer; peer = &peers->peer[0]; @@ -624,6 +624,10 @@ ngx_http_upstream_get_peer(ngx_http_upstream_rr_peers_t *peers) return n; } + if (reset++) { + return 0; + } + for (i = 0; i < peers->number; i++) { peer[i].current_weight = peer[i].weight; }