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Clarify PreStop hook behaviour

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This commit is contained in:
Luke Addison
2021-02-01 16:47:44 +00:00
parent 2527359c13
commit bfea67aa82
1 changed files with 15 additions and 17 deletions
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content/en/docs/concepts/containers/container-lifecycle-hooks.md
+15 -17
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@@ -36,10 +36,12 @@ No parameters are passed to the handler.
`PreStop` `PreStop`
This hook is called immediately before a container is terminated due to an API request or management event such as liveness probe failure, preemption, resource contention and others. A call to the preStop hook fails if the container is already in terminated or completed state. This hook is called immediately before a container is terminated due to an API request or management
It is blocking, meaning it is synchronous, event such as a liveness/startup probe failure, preemption, resource contention and others. This
so it must complete before the signal to stop the container can be sent. hook is not called if the container crashes or exits. The Pod's termination grace period countdown
No parameters are passed to the handler. begins before the `PreStop` hook is executed. Regardless of the outcome of the handler, the
container will eventually terminate within the Pod's termination grace period. No parameters are
passed to the handler.
A more detailed description of the termination behavior can be found in A more detailed description of the termination behavior can be found in
[Termination of Pods](/docs/concepts/workloads/pods/pod-lifecycle/#pod-termination). [Termination of Pods](/docs/concepts/workloads/pods/pod-lifecycle/#pod-termination).
@@ -65,19 +67,15 @@ the Container ENTRYPOINT and hook fire asynchronously.
However, if the hook takes too long to run or hangs, However, if the hook takes too long to run or hangs,
the Container cannot reach a `running` state. the Container cannot reach a `running` state.
`PreStop` hooks are not executed asynchronously from the signal `PreStop` hooks are not executed asynchronously from the signal to stop the Container; the hook must
to stop the Container; the hook must complete its execution before complete its execution before the TERM signal can be sent. If a `PreStop` hook hangs during
the signal can be sent. execution, the Pod's phase will be `Terminating` and remain there until the Pod is killed after its
If a `PreStop` hook hangs during execution, `terminationGracePeriodSeconds` expires. This grace period applies to the total time it takes for
the Pod's phase will be `Terminating` and remain there until the Pod is both the `PreStop` hook to execute and for the Container to stop normally. If, for example,
killed after its `terminationGracePeriodSeconds` expires. `terminationGracePeriodSeconds` is 60, and the hook takes 55 seconds to complete, and the Container
This grace period applies to the total time it takes for both takes 10 seconds to stop normally after receiving the signal, then the Container will be killed
the `PreStop` hook to execute and for the Container to stop normally. before it can stop normally, since `terminationGracePeriodSeconds` is less than the total time
If, for example, `terminationGracePeriodSeconds` is 60, and the hook (55+10) it takes for these two things to happen.
takes 55 seconds to complete, and the Container takes 10 seconds to stop
normally after receiving the signal, then the Container will be killed
before it can stop normally, since `terminationGracePeriodSeconds` is
less than the total time (55+10) it takes for these two things to happen.
If either a `PostStart` or `PreStop` hook fails, If either a `PostStart` or `PreStop` hook fails,
it kills the Container. it kills the Container.