Apache hangs on "child process X still did not exit, sending a SIGKILL"

Question

I did update on server to php7.3-fpm to get http2 working. Setup everything needed, h2 works great, all websites is up. But like every 5 minutes server get stuck on these errors until I restart apache.

I checked all configs, tried to calculate MaxRequestWorkers, maxclients, pm.max_children, pm.start_servers, pm.min_spare_servers, pm.max_spare_servers. Every change make it worse or make it stay longer.

Server config

debian 10
apache 2.4.38
php 7.3.14
5.8GB memory
2 x Intel(R) Xeon(R) CPU E3-1585L v5 @ 3.00GHz

Server stats

approx 100-200 live users
https://i.stack.imgur.com/kKxLh.png (can't post images no rep)

Errors

[Tue Nov 03 15:30:07.450356 2020] [core:warn] [pid 31147:tid 139885881660544] AH00045: child process 31148 still did not exit, sending a SIGTERM
[Tue Nov 03 15:30:07.450391 2020] [core:warn] [pid 31147:tid 139885881660544] AH00045: child process 31149 still did not exit, sending a SIGTERM
[Tue Nov 03 15:30:07.450397 2020] [core:warn] [pid 31147:tid 139885881660544] AH00045: child process 5692 still did not exit, sending a SIGTERM
[Tue Nov 03 15:30:07.450401 2020] [core:warn] [pid 31147:tid 139885881660544] AH00045: child process 5860 still did not exit, sending a SIGTERM
[Tue Nov 03 15:30:07.450406 2020] [core:warn] [pid 31147:tid 139885881660544] AH00045: child process 5982 still did not exit, sending a SIGTERM
[Tue Nov 03 15:30:07.450410 2020] [core:warn] [pid 31147:tid 139885881660544] AH00045: child process 6138 still did not exit, sending a SIGTERM
[Tue Nov 03 15:30:09.452520 2020] [core:warn] [pid 31147:tid 139885881660544] AH00045: child process 31148 still did not exit, sending a SIGTERM
[Tue Nov 03 15:30:09.452556 2020] [core:warn] [pid 31147:tid 139885881660544] AH00045: child process 31149 still did not exit, sending a SIGTERM
[Tue Nov 03 15:30:09.452562 2020] [core:warn] [pid 31147:tid 139885881660544] AH00045: child process 5692 still did not exit, sending a SIGTERM
[Tue Nov 03 15:30:09.452567 2020] [core:warn] [pid 31147:tid 139885881660544] AH00045: child process 5860 still did not exit, sending a SIGTERM
[Tue Nov 03 15:30:09.452573 2020] [core:warn] [pid 31147:tid 139885881660544] AH00045: child process 5982 still did not exit, sending a SIGTERM
[Tue Nov 03 15:30:09.452578 2020] [core:warn] [pid 31147:tid 139885881660544] AH00045: child process 6138 still did not exit, sending a SIGTERM
[Tue Nov 03 15:30:11.454710 2020] [core:warn] [pid 31147:tid 139885881660544] AH00045: child process 31148 still did not exit, sending a SIGTERM
[Tue Nov 03 15:30:11.454739 2020] [core:warn] [pid 31147:tid 139885881660544] AH00045: child process 31149 still did not exit, sending a SIGTERM
[Tue Nov 03 15:30:11.454744 2020] [core:warn] [pid 31147:tid 139885881660544] AH00045: child process 5692 still did not exit, sending a SIGTERM
[Tue Nov 03 15:30:11.454760 2020] [core:warn] [pid 31147:tid 139885881660544] AH00045: child process 5860 still did not exit, sending a SIGTERM
[Tue Nov 03 15:30:11.454764 2020] [core:warn] [pid 31147:tid 139885881660544] AH00045: child process 5982 still did not exit, sending a SIGTERM
[Tue Nov 03 15:30:11.454768 2020] [core:warn] [pid 31147:tid 139885881660544] AH00045: child process 6138 still did not exit, sending a SIGTERM
[Tue Nov 03 15:30:13.456926 2020] [core:error] [pid 31147:tid 139885881660544] AH00046: child process 31148 still did not exit, sending a SIGKILL
[Tue Nov 03 15:30:13.456983 2020] [core:error] [pid 31147:tid 139885881660544] AH00046: child process 31149 still did not exit, sending a SIGKILL
[Tue Nov 03 15:30:13.457006 2020] [core:error] [pid 31147:tid 139885881660544] AH00046: child process 5692 still did not exit, sending a SIGKILL
[Tue Nov 03 15:30:13.457028 2020] [core:error] [pid 31147:tid 139885881660544] AH00046: child process 5860 still did not exit, sending a SIGKILL
[Tue Nov 03 15:30:13.457059 2020] [core:error] [pid 31147:tid 139885881660544] AH00046: child process 5982 still did not exit, sending a SIGKILL
[Tue Nov 03 15:30:13.457094 2020] [core:error] [pid 31147:tid 139885881660544] AH00046: child process 6138 still did not exit, sending a SIGKILL
[Tue Nov 03 15:30:14.458349 2020] [mpm_event:notice] [pid 31147:tid 139885881660544] AH00491: caught SIGTERM, shutting down

Server mpm-event.conf

<IfModule mpm_event_module>
    StartServers             2
    MinSpareThreads      25
    MaxSpareThreads      75
    ThreadLimit          64
    ThreadsPerChild      25
    MaxRequestWorkers     150
    MaxConnectionsPerChild   0
</IfModule>

Thanks for support,

Andrew Schulman · Accepted Answer · 2020-11-26T13:28:41.673

0

You may need to switch your MPM from event to prefork. Most versions of PHP are still not thread safe, and the only MPM that's safe to use with non-thread-safe code is prefork, since it creates new processes, instead of threads, to handle new requests.

edited Nov 26 '20 at 13:28

answered Nov 04 '20 at 12:17

Andrew Schulman

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PHP-FPM is fine to use and is recommended over prefork. It is also a single-threaded solution. The issue is probably due to [stuck clients](http://techmythsworld.blogspot.com/2011/11/solving-httpd-maxclients-and-modstatus.html). – rustyx Mar 08 '21 at 15:15
i had to switch to event to use PHP-FPM? – luky Jan 05 '22 at 10:19

Apache hangs on "child process X still did not exit, sending a SIGKILL"

1 Answers1