Status code 0

[Sébastien Rebecchi]

Hello

Just to close that conversation, it seems this was an error of our devops
in charge of alerting, who was using curl in a bad way.

Best regards,

Sébastien

Le lun. 6 mai 2024 à 11:33, Sébastien Rebecchi <srebecchi at kameleoon.com> a
écrit :

> Hello!
>
> There is nothing regarding this issue in nginx logs.
>
> Now I think the issue is not with nginx itself, but in front of nginx,
> with Linux itself.
> We monitor using curl, and it seems that curl can print status code 0 when
> it can not establish a connection with the server.
> I think the Linux kernel is not configured properly to handle our
> connection peaks. Looking at net.core.somaxconn, we have the default of
> 128. More generally, I will deep dive into this and possibly other kernel
> settings to see if optimizing them will solve the problem. For information,
> on each of our servers we have an average of around 80K simultaneous TCP
> connections globally and around 35K in state ESTABLISHED (according to
> netstat/ss -nta), and more during high peaks.
> I saw this doc section which is a good starting point
> https://www.nginx.com/blog/tuning-nginx/#Tuning-Your-Linux-Configuration
> If you have any advice on other settings to increase, this would be very
> appreciated.
>
> I will keep you in touch about my investigations, to confirm at least that
> there is no bug on nginx side, which i am quite confident about now.
>
> Thank you very much for your help!
>
> Le sam. 4 mai 2024 à 20:47, Maxim Dounin <mdounin at mdounin.ru> a écrit :
>
>> Hello!
>>
>> On Sat, May 04, 2024 at 07:31:43PM +0200, Sébastien Rebecchi wrote:
>>
>> > Hello
>> >
>> > What does it mean when nginx returns an http status code 0?
>> >
>> > We see that cause we monitor nginx response status code, which is used
>> as
>> > front of our apps. The apps themselves can not return 0, only 200 or
>> 500.
>> > So it seems issue here comes from nginx itself which can not process the
>> > connection under high peak of load, but why 0, is that expected?
>>
>> Status code 0 as seen in nginx http access logs means that nginx
>> wasn't able to generate any reasonable status code, even some
>> generic failure like 500 (Internal Server Error), yet the request
>> was closed.
>>
>> This usually happens due to some fatal issues, like unexpected
>> conditions (which might indicate a bug somewhere), unexpected
>> errors, or memory allocation errors if it wasn't possible to
>> return 500.
>>
>> In most cases there should be additional details in the error log
>> explaining the reasons.  If there aren't any, or reasons aren't
>> clear, it might be a good idea to dig further.
>>
>> --
>> Maxim Dounin
>> http://mdounin.ru/
>> --
>> nginx mailing list
>> nginx at freenginx.org
>> https://freenginx.org/mailman/listinfo/nginx
>>
>
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