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StatefulSet: Document workaround for known rolling update issue. (#13190)

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Anthony Yeh
2019-03-21 07:01:41 -07:00
committed by Kubernetes Prow Robot
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commit 6c95d99195
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content/en/docs/concepts/workloads/controllers/statefulset.md
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@@ -48,6 +48,10 @@ provides a set of stateless replicas. Controllers such as
* Deleting and/or scaling a StatefulSet down will *not* delete the volumes associated with the StatefulSet. This is done to ensure data safety, which is generally more valuable than an automatic purge of all related StatefulSet resources. * Deleting and/or scaling a StatefulSet down will *not* delete the volumes associated with the StatefulSet. This is done to ensure data safety, which is generally more valuable than an automatic purge of all related StatefulSet resources.
* StatefulSets currently require a [Headless Service](/docs/concepts/services-networking/service/#headless-services) to be responsible for the network identity of the Pods. You are responsible for creating this Service. * StatefulSets currently require a [Headless Service](/docs/concepts/services-networking/service/#headless-services) to be responsible for the network identity of the Pods. You are responsible for creating this Service.
* StatefulSets do not provide any guarantees on the termination of pods when a StatefulSet is deleted. To achieve ordered and graceful termination of the pods in the StatefulSet, it is possible to scale the StatefulSet down to 0 prior to deletion. * StatefulSets do not provide any guarantees on the termination of pods when a StatefulSet is deleted. To achieve ordered and graceful termination of the pods in the StatefulSet, it is possible to scale the StatefulSet down to 0 prior to deletion.
* When using [Rolling Updates](#rolling-updates) with the default
[Pod Management Policy](#pod-management-policies) (`OrderedReady`),
it's possible to get into a broken state that requires
[manual intervention to repair](#forced-rollback).
## Components ## Components
The example below demonstrates the components of a StatefulSet. The example below demonstrates the components of a StatefulSet.
@@ -241,6 +245,26 @@ updates to its `.spec.template` will not be propagated to its Pods.
In most cases you will not need to use a partition, but they are useful if you want to stage an In most cases you will not need to use a partition, but they are useful if you want to stage an
update, roll out a canary, or perform a phased roll out. update, roll out a canary, or perform a phased roll out.
#### Forced Rollback
When using [Rolling Updates](#rolling-updates) with the default
[Pod Management Policy](#pod-management-policies) (`OrderedReady`),
it's possible to get into a broken state that requires manual intervention to repair.
If you update the Pod template to a configuration that never becomes Running and
Ready (for example, due to a bad binary or application-level configuration error),
StatefulSet will stop the rollout and wait.
In this state, it's not enough to revert the Pod template to a good configuration.
Due to a [known issue](https://github.com/kubernetes/kubernetes/issues/67250),
StatefulSet will continue to wait for the broken Pod to become Ready
(which never happens) before it will attempt to revert it back to the working
configuration.
After reverting the template, you must also delete any Pods that StatefulSet had
already attempted to run with the bad configuration.
StatefulSet will then begin to recreate the Pods using the reverted template.
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