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.
diff --git a/src/http/ngx_http_upstream_round_robin.c b/src/http/ngx_http_upstream_round_robin.c
index de34b28..c15790a 100644
--- a/src/http/ngx_http_upstream_round_robin.c
+++ b/src/http/ngx_http_upstream_round_robin.c
@@ -585,7 +585,7 @@
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 @@
return n;
}
+ if (reset++) {
+ return 0;
+ }
+
for (i = 0; i < peers->number; i++) {
peer[i].current_weight = peer[i].weight;
}
