Nginx prematurely closing connections when reloaded

Thu Mar 28 15:40:03 UTC 2024

Sébastien,

The message about the signal process is only the beginning of the process.
You are interested in messages like the following:

> 2024/03/26 13:36:36 [notice] 723#723: signal 1 (SIGHUP) received from 
> 69064, reconfiguring
> 2024/03/26 13:36:36 [notice] 723#723: reconfiguring
> 2024/03/26 13:36:36 [notice] 723#723: using the "epoll" event method
> 2024/03/26 13:36:36 [notice] 723#723: start worker processes
> 2024/03/26 13:36:36 [notice] 723#723: start worker process 69065
> 2024/03/26 13:36:36 [notice] 723#723: start worker process 69066
> 2024/03/26 13:36:36 [notice] 723#723: start cache manager process 69067
> 2024/03/26 13:36:36 [notice] 61903#61903: gracefully shutting down
> 2024/03/26 13:36:36 [notice] 61905#61905: exiting
> 2024/03/26 13:36:36 [notice] 61903#61903: exiting
> 2024/03/26 13:36:36 [notice] 61904#61904: gracefully shutting down
> 2024/03/26 13:36:36 [notice] 61904#61904: exiting
> 2024/03/26 13:36:36 [notice] 61903#61903: exit

Note the 'gracefully shutting down' and 'exiting' message from workers. 
Also the 'start' and 'reconfiguring' messages from the master process.
There should be a similar sequence somewhere in your logs.
Having these logs may help explaining what happens on a reload.

Kind regards,
Igor.

On 26/03/2024 12:41, Sébastien Rebecchi wrote:
> Hi Igor
>
> There is no special logs on the IP_1 (the reloaded one) side, only 1 
> log line, which is expected:
> --- BEGIN ---
> 2024/03/26 13:37:55 [notice] 3928855#0: signal process started
> --- END ---
>
> I did not configure worker_shutdown_timeout, it is unlimited.
>
> Sébastien.
>
> Le lun. 25 mars 2024 à 17:59, Igor Ippolitov <iippolitov at nginx.com> a 
> écrit :
>
>     Sébastien,
>
>     Nginx should keep active connections open and wait for a request
>     to complete before closing.
>     A reload starts a new set of workers while old workers wait for
>     old connections to shut down.
>     The only exception I'm aware of is having worker_shutdown_timeout
>     configured: in this case a worker will wait till this timeout and
>     forcibly close a connection. Be default there is no timeout.
>
>     It would be curious to see error log of nginx at IP_1 (the
>     reloaded one) while the reload happens. It may explain the reason
>     for connection resets.
>
>     Kind regards,
>     Igor.
>
>     On 25/03/2024 12:31, Sébastien Rebecchi wrote:
>>
>>     Hello
>>
>>
>>     I have an issue with nginx closing prematurely connections when
>>     reload is performed.
>>
>>
>>     I have some nginx servers configured to proxy_pass requests to an
>>     upstream group. This group itself is composed of several servers
>>     which are nginx themselves, and is configured to use keepalive
>>     connections.
>>
>>     When I trigger a reload (-s reload) on an nginx of one of the
>>     servers which is target of the upstream, I see in error logs of
>>     all servers in front that connection was reset by the nginx which
>>     was reloaded.
>>
>>
>>     Here configuration of upstream group (IPs are hidden replaced by
>>     IP_X):
>>
>>     --- BEGIN ---
>>
>>     upstream data_api {
>>
>>     random;
>>
>>
>>     server IP_1:80 max_fails=3 fail_timeout=30s;
>>
>>     server IP_2:80 max_fails=3 fail_timeout=30s;
>>
>>     server IP_3:80 max_fails=3 fail_timeout=30s;
>>
>>     server IP_4:80 max_fails=3 fail_timeout=30s;
>>
>>     server IP_5:80 max_fails=3 fail_timeout=30s;
>>
>>     server IP_6:80 max_fails=3 fail_timeout=30s;
>>
>>     server IP_7:80 max_fails=3 fail_timeout=30s;
>>
>>     server IP_8:80 max_fails=3 fail_timeout=30s;
>>
>>     server IP_9:80 max_fails=3 fail_timeout=30s;
>>
>>     server IP_10:80 max_fails=3 fail_timeout=30s;
>>
>>
>>     keepalive 20;
>>
>>     }
>>
>>     --- END ---
>>
>>
>>     Here configuration of the location using this upstream:
>>
>>     --- BEGIN ---
>>
>>     location / {
>>
>>     proxy_pass http://data_api;
>>
>>
>>     proxy_http_version 1.1;
>>
>>     proxy_set_header Connection "";
>>
>>
>>     proxy_set_header Host $host;
>>
>>     proxy_set_header X-Real-IP $real_ip;
>>
>>     proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
>>
>>
>>     proxy_connect_timeout 2s;
>>
>>     proxy_send_timeout 6s;
>>
>>     proxy_read_timeout 10s;
>>
>>
>>     proxy_next_upstream error timeout http_502 http_504;
>>
>>     }
>>
>>     --- END ---
>>
>>
>>     And here the kind of error messages I get when I reload nginx of
>>     "IP_1":
>>
>>     --- BEGIN ---
>>
>>     2024/03/25 11:24:25 [error] 3758170#0: *1795895162 recv() failed
>>     (104: Connection reset by peer) while reading response header
>>     from upstream, client: CLIENT_IP_HIDDEN, server: SERVER_HIDDEN,
>>     request: "POST /REQUEST_LOCATION_HIDDEN HTTP/2.0", upstream:
>>     "http://IP_1:80/REQUEST_LOCATION_HIDDEN
>>     <http://IP_1:80/REQUEST_LOCATION_HIDDEN>", host: "HOST_HIDDEN",
>>     referrer: "REFERRER_HIDDEN"
>>
>>     --- END ---
>>
>>
>>     I thought -s reload was doing graceful shutdown of connections.
>>     Is it due to the fact that nginx can not handle that when using
>>     keepalive connections? Is it a bug?
>>
>>     I am using nginx 1.24.0 everywhere, no particular
>>
>>
>>     Thank you for any help.
>>
>>
>>     Sébastien
>>
>>
>>     _______________________________________________
>>     nginx mailing list
>>     nginx at nginx.org
>>     https://mailman.nginx.org/mailman/listinfo/nginx
>
>
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