Debugging 504 Gateway Timeout and its actual cause and solution
mdounin at mdounin.ru
Fri Jan 8 16:34:23 UTC 2016
On Wed, Jan 06, 2016 at 02:56:43AM -0500, Keyur wrote:
> Thanks Richard & itpp2015 for your response.
> Further update :
> There are 2 cases :
> 1. 504 @ 120 seconds coming with below mentioned error :
> 2016/01/05 03:50:54 [error] 1070#0: *201650845 upstream timed out (110:
> Connection timed out) while connecting to upstream, client: 22.214.171.124,
> server: x.x.x.x, request: "GET /some/url HTTP/1.1", upstream:
> "fastcgi://127.0.0.1:9000", host: "example.com"
This means that nginx failed to connect to your backend server in
time. This can happen in two basic cases:
- network problems (unlikely for localhost though); e.g., this can
happen if you have a statefull firewall configured between nginx
and there aren't enough states.
- backend is overloaded and doesn't accept connections fast
The latter is more likely, and usually happens when using
Linux. Try watching your backend listen socket queue (something
like "ss -nlt" should work on Linux) and/or try switching on
net.ipv4.tcp_abort_on_overflow sysctl to see if it's the case.
> 2. 504 @ 300 seconds coming with below mentioned error :
> 2016/01/05 00:51:43 [error] 1067#0: *200656359 upstream timed out (110:
> Connection timed out) while reading response header from upstream, client:
> 126.96.36.199, server: 192.168.12.101, request: "GET /some/url HTTP/1.1",
> upstream: "fastcgi://127.0.0.1:9000", host: "example.com"
The message suggests the backend failed to respond in time to a
particular request. Depending on the request this may be either
some generic problem (i.e., the backend is overloaded) or a
problem with handling of the particular request. Try debugging
what happens on the backend.
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