systemctl stop kumomta.service / systemctl restart kumomta.service hangs

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1

Hello ! When i execute the systemctl stop kumomta.service or systemctl restart kumomta.service command, it hangs for approx 5 minutes before stopping the service, i have seen some similar reports in the Discord, do you have an idea why ? In total i had 2 installation of kumomta on 2 different machines, from my experience it seems that in the beginning everything works fine, but if you start to make several restarts in a row, the issue will show up.

This issue is happening in our testing env, so it has very little load

Logs :

2025-04-01T09:11:06.286099Z  INFO localset-0 kumod::smtp_server: smtp listener on 0.0.0.0:2525 -> stopping
2025-04-01T09:11:06.286188Z  INFO   qmaint-0 kumod::ready_queue: queue_config_maintainer stopping
2025-04-01T09:11:06.287393Z  INFO   qmaint-0 kumod::queue: queue_config_maintainer stopping
2025-04-01T09:15:38.611822Z  INFO       main kumo_server_common::start: Shutdown completed OK!
2025-04-01T09:15:38.626678Z  INFO       main kumod::spool: Shutting down spool
2025-04-01T09:15:38.626987Z  INFO       main kumod::spool: data shutdown completed in 170.949µs
2025-04-01T09:15:38.627003Z  INFO       main kumod::spool: meta shutdown completed in 149.111µs
2025-04-01T09:15:38.627389Z  INFO       main kumod: application logic complete, returning from main

Kcli top at the moment of the stop :

Thank you for your help

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3

Stacktrace:
message.txt (37.1 KB)

4

Service status while the stop command is hanging :

kumomta.service - KumoMTA SMTP service
     Loaded: loaded (/etc/systemd/system/kumomta.service; enabled; preset: enabled)
     Active: deactivating (stop-sigterm) since Tue 2025-04-01 11:49:59 CEST; 2min 2s ago
   Main PID: 181751 (kumod)
      Tasks: 27 (limit: 19102)
     Memory: 38.6M (peak: 97.3M)
        CPU: 623ms
     CGroup: /system.slice/kumomta.service
             └─181751 /opt/kumomta/sbin/kumod --policy /opt/kumomta/etc/policy/init.lua --user kumod

avril 01 11:49:44 xxxxx systemd[1]: Started kumomta.service - KumoMTA SMTP service.
avril 01 11:49:59 xxxxx systemd[1]: Stopping kumomta.service - KumoMTA SMTP service...
5

It seems that if kumo has been running for a while (a dozen minutes i’d say), the systemctl stop kumomta.service will be executed almost instantly, but if just after that stop, i start & try to stop the service again, this time the systemctl stop kumomta.service command will hang for 5 minutes

6

Kumomta may need some time to process the unprocessed data before shutting down safely. May I ask if the sending volume will be large?

7

Connections are not instantly terminated when restarting or shutting down, they are allowed to complete their timeouts. That is the most typical cause.

8

It sounds like you have a misconfiguration somewhere. 5 minutes is the systemd timeout so you will probably find that if you trace the journal in debug mode you will see whatever is thrashing around and a final SIGKILL, which should never happen if it is configured correctly.

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