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Warn about implications on selector updates

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Signed-off-by: Michail Kargakis <mkargaki@redhat.com>
This commit is contained in:
Michail Kargakis
2017-05-23 16:14:45 +02:00
committed by Andrew Chen
parent 328b62a34a
commit 8a27d982e6
1 changed files with 16 additions and 1 deletions
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docs/concepts/workloads/controllers/deployment.md
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@@ -209,7 +209,7 @@ least 2 Pods were available and at most 4 Pods were created at all times. It the
the new and the old ReplicaSet, with the same rolling update strategy. Finally, we'll have 3 available replicas
in the new ReplicaSet, and the old ReplicaSet is scaled down to 0.
### Rollover (multiple rollouts in-flight)
### Rollover (aka multiple updates in-flight)
Each time a new deployment object is observed by the deployment controller, a ReplicaSet is created to bring up
the desired Pods if there is no existing ReplicaSet doing so. Existing ReplicaSet controlling Pods whose labels
@@ -227,6 +227,21 @@ killing the 3 `nginx:1.7.9` Pods that it had created, and will start creating
`nginx:1.9.1` Pods. It will not wait for 5 replicas of `nginx:1.7.9` to be created
before changing course.
### Label selector updates
It is generally discouraged to make label selector updates and it is suggested to plan your selectors up front.
In any case, if you need to perform a label selector update, exercise great caution and make sure you have grasped
all of the implications.
* Selector additions require the pod template labels in the Deployment spec to be updated with the new label, too,
otherwise a validation error is returned. This change is a non-overlapping one, meaning that the new selector does
not select ReplicaSets and Pods created with the old selector, resulting in orphaning all old ReplicaSets and
creating a new ReplicaSet.
* Selector updates, i.e., changing the existing value in a selector key, result in the same behavior as additions.
* Selector removals, i.e., removing an existing key from the Deployment selector, do not require any changes in the
pod template labels, no existing ReplicaSet is orphaned, and a new ReplicaSet will not be created, but note that the
removed label will still exist in any existing Pods and ReplicaSets.
## Rolling Back a Deployment
Sometimes you may want to rollback a Deployment; for example, when the Deployment is not stable, such as crash looping.