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Document docker resource limits (#25925)

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* Document docker resource limits

* No longer experimental on JVM10
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Arnout Engelen 2018-11-15 16:48:57 +01:00 • committed by Christopher Batey
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akka-docs/src/main/paradox/additional/deploy.md
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@ -42,7 +42,34 @@ You can look at the
@scala[@extref[Cluster with docker-compose example project](samples:akka-sample-cluster-docker-compose-scala)]
to see what this looks like in practice.
For the JVM to run well in a Docker container, there are some general (not Akka specific) parameters that might need tuning. You may want to look into using [`-XX:+UnlockExperimentalVMOptions -XX:+UseCGroupMemoryLimitForHeap`](https://dzone.com/articles/running-a-jvm-in-a-container-without-getting-kille) options for your JVM later than 8u131, which makes it understand c-group memory limits.
For the JVM to run well in a Docker container, there are some general (not Akka specific) parameters that might need tuning:
### Resource limits
Docker allows [constraining each containers' resource usage](https://docs.docker.com/config/containers/resource_constraints/).
#### Memory
You may want to look into using [`-XX:+UnlockExperimentalVMOptions -XX:+UseCGroupMemoryLimitForHeap`](https://dzone.com/articles/running-a-jvm-in-a-container-without-getting-kille) options for your JVM later than 8u131, which makes it understand c-group memory limits. On JVM 10 and later, the `-XX:+UnlockExperimentalVMOptions` option is no longer needed.
#### CPU
For multi-threaded applications such as the JVM, the CFS scheduler limits are an ill fit, because they will restrict
the allowed CPU usage even when more CPU cycles are available from the host system. This means your application may be
starved of CPU time, but your system appears idle.
For this reason, it is best to avoid `--cpus` and `--cpu-quota` entirely, and instead specify relative container weights using `--cpu-shares` instead.
## In Kubernetes
### Cluster bootstrap
To take advantage of the fact that your are running inside of Kubernetes while forming a cluster, you can use the [Akka Cluster Bootstrap](https://developer.lightbend.com/docs/akka-management/current/bootstrap/) module.
You can look at the
@extref[Cluster with Kubernetes example project](samples:akka-sample-cluster-kubernetes-java)
to see what this looks like in practice.
### Resource limits
To avoid CFS scheduler limits, it is best not to use `resources.limits.cpu` limits, but use `resources.requests.cpu` configuration instead.