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Merge pull request #30155 from euank/clarify-container-lifecycle 

Automatic merge from submit-queue

docs: Detail possible transitions in CRI

Right now the document doesn't make it clear that transitions are unidirectional and a exited container won't be restarted, but replaced by a fresh copy.

cc @yujuhong @feiskyer @kubernetes/sig-node
pull/6/head
Kubernetes Submit Queue 2016-08-05 12:41:31 -07:00 committed by GitHub
parent f9cadb290b bad07dd06f
commit 13f376c9af
1 changed files with 20 additions and 5 deletions
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25
docs/proposals/container-runtime-interface-v1.md
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@ -175,11 +175,26 @@ To delete a pod:
stop container C --> remove container C --> delete sandbox Foo
```
The restart policy in the Pod Spec defines how indiviual containers should
be handled when they terminated. Kubelet is responsible to ensure that the
restart policy is enforced. In other words, once Kubelet discovers that a
container terminates (e.g., through `List()`), it will create and start a new
container if needed.
The container runtime must not apply any transition (such as starting a new
container) unless explicitly instructed by Kubelet. It is Kubelet's
responsibility to enforce garbage collection, restart policy, and otherwise
react to changes in lifecycle.
The only transitions that are possible for a container are described below:
```
() -> Created // A container can only transition to created from the
// empty, nonexistent state. The ContainerRuntime.Create
// method causes this transition.
Created -> Running // The ContainerRuntime.Start method may be applied to a
// Created container to move it to Running
Running -> Exited // The ContainerRuntime.Stop method may be applied to a running
// container to move it to Exited.
// A container may also make this transition under its own volition
Exited -> () // An exited container can be moved to the terminal empty
// state via a ContainerRuntime.Remove call.
```
Kubelet is also responsible for gracefully terminating all the containers
in the sandbox before deleting the sandbox. If Kubelet chooses to delete