Varnish 503 on POST requests once in a while

[Guillaume Quintard]

Hi,

Most probably, varnishncsa isn't going to give you the full picture, so
let's go for the exhaustive way:

varnishlog -q "BerespStatus eq 503" -w /whatever/file


you can then read the logs with

varnishlog -r /whatever/file


(more logging pointers here:
https://docs.varnish-software.com/tutorials/vsl-query/)

If you can get your hands on a failed transaction, we should be able to
tell you what went wrong. Most probably, you hit a timeout of some sort. Or
it could be that the backend was declared sick, if you have probes.

-- 
Guillaume Quintard


On Thu, Dec 26, 2019 at 6:33 AM Maninder Singh <mandys at gmail.com> wrote:

> Hi,
>
> I am facing a strange problem.
>
> I am running varnish 4.1.11 on port 80 which is behind a LB.
>
> Varnish then connects to apache 2.4 ( on port 8080 ) and also have php-fpm
> running.
>
> Now, everything works fine but once in a while I am seeing 503 response
> from varnish for a POST request. During this time there is no log in apache
> also ( neither access log nor error log ).
>
> Where does this request vanish ?
>
> How do I debug this issue ?
>
> Some more details:
>
> * I have varnishncsa turned on with following flags.
>
> ExecStart=/usr/bin/varnishncsa -q 'not (ReqURL ~
> "\.(js|css|png|jpeg|jpg|ico|gif|swf|woff)" or ReqHeader:User-Agent ~
> "HTTP-Monitor" or ReqHeader:User-Agent ~ "Monitoring/1.1")' -a -w
> /var/log/varnish/varnishncsa.log -D -f /etc/sysconfig/varnishncsa
>
> Here is the entry in varnish log during that time.
>
> X.X.X.X, LB.IP.0.0 - - [25/Dec/2019:00:26:40 -0600] 2629363 "POST
> http://mydomain.com/LetsCelebrate HTTP/1.1" 503 1288 "
> https://referringdomain.com/LetsCelebrate?hostingUrl=https%3A%2F%2Fxy.abc.com"
> "Mozilla/5.0 (Linux; Android 9; SM-A920F) AppleWebKit/537.36 (KHTML, like
> Gecko) Chrome/79.0.3945.93 Mobile Safari/537.36" "mydomain.com" miss
>
> In .vcl file I have following set.
>  .first_byte_timeout = 120s;
>
> Now, I am not logging varnish to apache requests ( which backend fetch ).
> As you can see above I am only logging client requests.
>
> Is their a way to log client requests like above but then also log backend
> fetch failures to another log file ?
> [ Running 2 instances of varnishncsa ? ]
>
> Any pointers ?
>
> Please let me know.
>
> Thanks.
>
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>
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