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Warn about implications on selector updates

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Signed-off-by: Michail Kargakis <mkargaki@redhat.com>
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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 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. 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 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 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 `nginx:1.9.1` Pods. It will not wait for 5 replicas of `nginx:1.7.9` to be created
before changing course. 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 ## Rolling Back a Deployment
Sometimes you may want to rollback a Deployment; for example, when the Deployment is not stable, such as crash looping. Sometimes you may want to rollback a Deployment; for example, when the Deployment is not stable, such as crash looping.