Hello!
On Fri, Jun 20, 2014 at 11:29:39PM +0000, Eric Swenson wrote:
> Hello Maxim,
>
> On 6/20/14, 3:46 PM, "Maxim Dounin" <mdounin@mdounin.ru> wrote:
>
> >Hello!
> >
> >On Fri, Jun 20, 2014 at 07:32:36PM +0000, Eric Swenson wrote:
> >
> >[...]
> >
> >> This works fine. However, every once in a while (say, every
> >> week or so), traffic to https://app.example.com/svc/api/xxxx
> >> returns gateway 502 errors. The API service (located at
> >> https://svc.example.com/api) is working fine and is accessible
> >> directly. However, through the proxy setup (above), nginx will
> >> not pass traffic. Simply restarting nginx gets it working again
> >> for another week or so, only to have it get into the same state
> >> again some random interval later.
> >>
> >> Does anyone have any ideas what might be causing nginx to fail
> >> to proxy traffic when no changes to the configuration have been
> >> made and the backend service is functioning normally?
> >
> >First of all, it may be a good idea to take a look into error log.
>
> The only messages in the error log were ones for hours before and for
> hours after the ³problem², of the form:
>
> 2014/06/17 17:14:16 [error] 28165#0: *1508 no user/password was provided
> for basic authentication, client: 11.12.13.14, server:
> app.test.example.com, request: "GET / HTTP/1.1", host:
> ³app.test.example.com"
>
> There was nothing related to the 502 errors around the time of the first
> request that failed with a 502 error code. The access log shows quite a
> few requests failing with a 502 status code from that point forward, up
> until the time that I restarted nginx.
If there is nothing in error logs, and you are getting 502 errors,
then there are two options:
1. The 502 errors are returned by your backend, not generated by
nginx.
2. You did something wrong while configuring error logs and/or you
are looking into a wrong log.
In this particular case, I would suggest the latter.
--
Maxim Dounin
http://nginx.org/
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