# I got 502 and error\_log print upstream sent invalid status "0" **URL:** \ **Category:** NGINX\ **Created:** [March 30, 2012, 5:15am UTC](https://www.ruby-forum.com/t/i-got-502-and-error-log-print-upstream-sent-invalid-status-0/218390 "2012-03-30T05:15:16Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![dubstep](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/cdc98d/32.png) [@dubstep](https://www.ruby-forum.com/u/dubstep)\ **Post date:** [March 30, 2012, 5:15am UTC](https://www.ruby-forum.com/t/i-got-502-and-error-log-print-upstream-sent-invalid-status-0/218390/1 "2012-03-30T05:15:16Z")
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’? Yours Sincerely. Posted at Nginx Forum: > **[I got 502 and error\_log print upstream sent invalid status "0"](https://forum.nginx.org/read.php?2,224638,224638#msg-224638)** > > 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... ---
**Author:** ![neoesque](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/54ee81/32.png) [@neoesque](https://www.ruby-forum.com/u/neoesque)\ **Post date:** [March 30, 2012, 5:28am UTC](https://www.ruby-forum.com/t/i-got-502-and-error-log-print-upstream-sent-invalid-status-0/218390/2 "2012-03-30T05:28:22Z")
Hello! On Thu, Mar 29, 2012 at 11:14:46PM -0400, neoesque wrote: > “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 D. ---
**Author:** ![neoesque](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/54ee81/32.png) [@neoesque](https://www.ruby-forum.com/u/neoesque)\ **Post date:** [March 30, 2012, 5:45am UTC](https://www.ruby-forum.com/t/i-got-502-and-error-log-print-upstream-sent-invalid-status-0/218390/3 "2012-03-30T05:45:11Z")
Hi, Maxim Thanks, I’ll check those PHP codes. Posted at Nginx Forum: > **[Re: I got 502 and error\_log print upstream sent invalid status "0"](https://forum.nginx.org/read.php?2,224638,224642#msg-224642)** > > 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... ---
**Author:** ![neoesque](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/54ee81/32.png) [@neoesque](https://www.ruby-forum.com/u/neoesque)\ **Post date:** [March 30, 2012, 5:57am UTC](https://www.ruby-forum.com/t/i-got-502-and-error-log-print-upstream-sent-invalid-status-0/218390/4 "2012-03-30T05:57:35Z")
OH! You are right, Maxim. Those errors are retrieving other webpage by using curl. And the upstreams return status code 0 seldomly. Thank you. Posted at Nginx Forum: > **[Re: I got 502 and error\_log print upstream sent invalid status "0"](https://forum.nginx.org/read.php?2,224638,224645#msg-224645)** > > 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...