Hello!

On Fri, Mar 30, 2012 at 07:06:17PM +0530, Sparsh Gupta wrote:

> Upon further debugging, the possible issue is at the following line:
>
> src/http/ngx_http_upstream_round_robin.c:433
> 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));
>
>
>
> The pc->tries is a ridiculously large number, which causes looping. Here is
> the configuration used to reproduce the error:
>
> worker_processes 1;
> worker_rlimit_nofile 32768;
> error_log /var/log/nginx/error.log warn;
> events { worker_connections 16384; use epoll; }
>
> http {
> access_log off;
>
> upstream a {
> server 10.56.140.8 backup;
> server 10.56.140.2 backup;
> server 10.56.140.4 backup;
> server 10.56.140.6 backup;
> }
>
> upstream b {
> server 10.56.140.16 max_fails=100 fail_timeout=5s;
> server 10.56.140.8 backup;
> server 10.56.140.2 backup;
> server 10.56.140.4 backup;
> server 10.56.140.6 backup;
> }
>
> server {
> listen 80;
>
> location = /j.php {
> include /etc/nginx/proxy.conf; #with some timeout variables
> which are not relevant here I think
> proxy_pass http://b;
> error_page 403 404 500 502 503 504 = @fallback;
> }
>
> location @fallback {
> proxy_pass http://a;
> }
> }
> }

Upstream "a" have only backup servers, and this is what causes
problems. This is in fact configuration error (you have to define
at least one non-backup server, else "backup" flag doesn't make
sense). But obviously this should be either rejected during
configuration parsing or handled somehow, CPU hog is a bug, thank
you for report.

With the following patch nginx will reject such configuration
during configuration parsing:

--- a/src/http/ngx_http_upstream_round_robin.c
+++ b/src/http/ngx_http_upstream_round_robin.c
@@ -49,6 +49,13 @@ ngx_http_upstream_init_round_robin(ngx_c
n += server[i].naddrs;
}

+ if (n == 0) {
+ ngx_log_error(NGX_LOG_EMERG, cf->log, 0,
+ "no servers in upstream \"%V\" in %s:%ui",
+ &us->host, us->file_name, us->line);
+ return NGX_ERROR;
+ }
+
peers = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_rr_peers_t)
+ sizeof(ngx_http_upstream_rr_peer_t) * (n - 1));
if (peers == NULL) {


Maxim Dounin

>
>
> Sparsh Gupta
>
>
> On 30 March 2012 18:23, Sparsh Gupta <sparshgupta@gmail.com> wrote:
>
> > I compiled a stable release 1.0.14 with no 3rd party modules and under
> > heavy load, gdb is showing hot looping around when error_page directive
> > is used. The CPU (all 8 cores) reaches 100% usage and the server stops
> > responding to further requests
> >
> > I am happy to share my configurations but its a very simple arrangement
> > with varnish server being the backend for proxy_pass. I am using
> > apache-benchmark to test it.
> >
> > Thanks
> > Sparsh Gupta
> >

> _______________________________________________
> nginx mailing list
> nginx@nginx.org
> http://mailman.nginx.org/mailman/listinfo/nginx

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