I got 502 and error_log print upstream sent invalid status "0"

[Maxim Dounin]

Hello!

On Thu, Mar 29, 2012 at 11:14:46PM -0400, neoesque wrote:

> Hi everyone,
> 
> I have a php-fpm backend. And sometimes I got nginx return 502. After I
> check the error_log I found each 502s are caused by upstream sent
> invalid status "0" while reading response header from upstream
> 
> The error_log are in the form "upstream sent invalid status "0" while
> reading response header from upstream client: 127.0.0.1, server: xxxx,
> request: "xxxxx HTTP/1.0", upstream:
> "fastcgi://unix:/dev/shm/api-php.socket:", host: "xxxx", referrer:
> "xxxx""
> 
> Does anyone have same experience? I have no idea after search Google
> 'upstream sent invalid status "0"'
> 
> I think it is caused by PHP. But why does it sent status '0'? 

The message in question means nginx got header line "Status: 0" 
from php.  Most likely it's what you php code did, not php by 
itself.

Maxim Dounin