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Fixing cpu hog with all upstream servers marked "down".

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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.
This commit is contained in:
Maxim Dounin 2011-08-18 16:52:38 +00:00
parent 9bc8fc4602
commit 624fbe94a2
1 changed files with 5 additions and 1 deletions
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6
src/http/ngx_http_upstream_round_robin.c
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@ -585,7 +585,7 @@ failed:
static ngx_uint_t static ngx_uint_t
ngx_http_upstream_get_peer(ngx_http_upstream_rr_peers_t *peers) 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; ngx_http_upstream_rr_peer_t *peer;
peer = &peers->peer[0]; peer = &peers->peer[0];
@ -624,6 +624,10 @@ ngx_http_upstream_get_peer(ngx_http_upstream_rr_peers_t *peers)
return n; return n;
} }
if (reset++) {
return 0;
}
for (i = 0; i < peers->number; i++) { for (i = 0; i < peers->number; i++) {
peer[i].current_weight = peer[i].weight; peer[i].current_weight = peer[i].weight;
} }