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Doc: Troubleshooting: recommend reducing concurrency for more speed (#9777)

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Alexander Aleksandrovič Klimov 2023-06-05 18:30:06 +02:00 committed by GitHub
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@ -317,6 +317,52 @@ not `assign where match("MySQL*", host.name) && host.vars.production`.
For all test hosts `host.vars.production` will be false and terminate
the `&&` rather than also evaluating `match("MySQL*", host.name)`.
### Try reducing concurrency (threads)
!!! note
This section applies rather to systems with more than eight CPU cores.
In case of less consider upgrading your hardware instead.
Yes, reducing and not increasing. By default, Icinga 2 already starts as many
threads as there are CPU cores according to the OS (unaware of SMT aka
Hyper-Threading). So there's no point in increasing as Icinga would not gain
additional CPU time.
But more threads also require more synchronization between them. This may
outweigh the CPU time gain and even worsen the performance. So reducing may
indeed help or at least save CPU time and power at no cost.
Start with benchmarking your Icinga 2 config with `time icinga2 daemon -C` on
the node in question. The results will be most accurate during normal operation,
i.e. while Icinga is running, but not reloading (e.g. due to config deployments).
Icinga accepts the argument `-DConfiguration.Concurrency=` with the number (of
threads) immediately after the "=". Start with 8 and finish with the number of
CPU cores. Write down the times. I.e.:
* `time icinga2 daemon -C -DConfiguration.Concurrency=8`
* `time icinga2 daemon -C -DConfiguration.Concurrency=10`
* `time icinga2 daemon -C -DConfiguration.Concurrency=12`
* ...
If significantly less threads than CPU cores significantly reduce the time
(reported as "real") Icinga 2 needs to load its configuration, pick the number
with the best time and persist it in your init daemon. In case of systemd copy
the `ExecStart=` line from output of `systemctl cat icinga2.service` first.
Next, run `systemctl edit icinga2.service`. This will open an editor. Add
`[Service]` (if not already present) and the copied `ExecStart=` line. Append
`-DConfiguration.Concurrency=` and the chosen number so that the result looks
like this:
```
[Service]
ExecStart=/usr/sbin/icinga2 daemon --close-stdio -e ${ICINGA2_ERROR_LOG} -DConfiguration.Concurrency=42
```
Save the file and close the editor. Restart Icinga.
Finally verify whether your changes took effect and enjoy the speed.
## Configuration Troubleshooting <a id="troubleshooting-configuration"></a>
### List Configuration Objects <a id="troubleshooting-list-configuration-objects"></a>