100% with upstream / backup server

[Matthias Rieber]

Hi,

I've noticed a strange issue. I've a configuration like:

...
upstream _backend {
   server 10.0.0.1:80 down;
   server 10.0.0.2:80 down;
   server 127.0.0.1:80 backup;
}
...


the purpose is to disable all backends and switch to some kind of 
maintenance mode.

Howerver, with this config, all workers have after the first requests a 
very high cpu load and nginx is not properly answering requests anymore.
Whenn I kill the workers, they reappear with the high load.

I such a setup not allowed?

kind regards,

matthias