Add Task: Scaling Stateful Sets #1774

janetkuo · 2016-11-23T01:00:54Z

cc @bprashanth @erictune @foxish @kow3ns @enisoc @kubernetes/sig-apps

This change is

janetkuo · 2016-11-23T01:02:53Z

The first commit is the common title for all new task docs for stateful set -- other PRs can include it to avoid dup works

foxish · 2016-11-23T01:04:28Z

docs/tasks/manage-stateful-set/scale-stateful-set.md

+
+### Use `kubectl` to scale Stateful Sets
+
+#### `kubectl scale` (>= 1.4 release)


Is this the client version? It's not clear if it is.

Removed this and suggested users to upgrade to >=1.5 kubectl

foxish · 2016-11-23T01:05:13Z

docs/tasks/manage-stateful-set/scale-stateful-set.md

+
+#### Scaling down doesn't not work right
+
+You cannot scale down a Stateful Set when some of the stateful pods it manages are unhealthy. Scaling down only takes place


s/some/any/

foxish · 2016-11-23T01:06:27Z

docs/tasks/manage-stateful-set/scale-stateful-set.md

+
+* Stateful Sets are only available in Kubernetes release >= 1.5. 
+* Stateful Sets are previously known as Pet Sets in Kubernetes release 1.3-1.4. You can either upgrade your Pet Sets to Stateful Sets, 
+or just change all `statefulset` references to `petset`. *TODO: link to upgrade from Pet Sets to Stateful Sets.*


just change all statefulset references to petset

I think this is a little unclear.

I don't think we need to refer to past versions from the 1.5 docs.

Removed all paragraphs about <1.5 clusters and petsets

foxish · 2016-11-23T01:08:12Z

docs/tasks/manage-stateful-set/scale-stateful-set.md

+kubectl scale statefulsets <stateful-set-name> --replicas=<new-replicas>
+```
+
+Note that `kubectl scale` only works on Stateful Set with Kubernetes release >= 1.4. 


Do we need to assert this, since Stateful Sets don't exist in older releases anyway.

kubectl scale works for Pet Sets in 1.4. Not sure how to handle the wording StatefulSets/PetSets without being too verbose

Do we even need to have Pet Set instructions at this point? I think removing all references to Pet Sets, and just explaining Stateful Sets would be cleaner. Also, isn't the old documentation for Pet Set going to be there anyway?

isn't the old documentation for Pet Set going to be there anyway?

The current doc plan is to deprecate the old user-guide for PetSets and link to StatefulSet concept guide there.

@devin-donnelly When we release 1.5 docs are we going to make the 1.4 docs available at kubernetes.io/1.4? We used to do that, but it doesn't work anymore.

Removed 1.4 stuffs

enisoc · 2016-11-23T01:35:38Z

Review status: 0 of 3 files reviewed at latest revision, 6 unresolved discussions.

docs/tasks/manage-stateful-set/scale-stateful-set.md, line 22 at r1 (raw file):

* Stateful Sets are previously known as Pet Sets in Kubernetes release 1.3-1.4. You can either upgrade your Pet Sets to Stateful Sets, 
or just change all `statefulset` references to `petset`. *TODO: link to upgrade from Pet Sets to Stateful Sets.*
* **Not all stateful applications scale nicely.** You need to understand your Stateful Sets well before continue. If you're unsure, remember that it may not be safe to scale your Stateful Sets.

"before continuing" or "before you continue"

docs/tasks/manage-stateful-set/scale-stateful-set.md, line 38 at r1 (raw file):

If you wish to change the number of replicas of your Stateful Set, just use this command:

I think you can delete "if you wish" and "just" to be more direct.

Comments from Reviewable

erictune · 2016-11-24T14:50:31Z

docs/tasks/manage-stateful-set/scale-stateful-set.md

+* Stateful Sets are only available in Kubernetes release >= 1.5. 
+* Stateful Sets are previously known as Pet Sets in Kubernetes release 1.3-1.4. You can either upgrade your Pet Sets to Stateful Sets, 
+or just change all `statefulset` references to `petset`. *TODO: link to upgrade from Pet Sets to Stateful Sets.*
+* **Not all stateful applications scale nicely.** You need to understand your Stateful Sets well before continue. If you're unsure, remember that it may not be safe to scale your Stateful Sets. 


before you continue or before continu ing.

erictune · 2016-11-24T15:00:18Z

docs/tasks/manage-stateful-set/scale-stateful-set.md

+#### Scaling down doesn't not work right
+
+You cannot scale down a Stateful Set when some of the stateful pods it manages are unhealthy. Scaling down only takes place
+after those stateful pods become running and ready. See discussions [here](https://github.com/kubernetes/kubernetes/issues/36333). 


Copy foxish's explanation verbatim here rather than linking to issue/

erictune

Looks good overall. Couple of questions and one missing word.

janetkuo · 2016-11-30T23:32:54Z

Review status: 0 of 3 files reviewed at latest revision, 8 unresolved discussions.

docs/tasks/manage-stateful-set/scale-stateful-set.md, line 22 at r1 (raw file):

Previously, enisoc (Anthony Yeh) wrote…

"before continuing" or "before you continue"

Done.

docs/tasks/manage-stateful-set/scale-stateful-set.md, line 22 at r1 (raw file):

Previously, erictune (Eric Tune) wrote…

before you continue or before continu ing.

Done.

docs/tasks/manage-stateful-set/scale-stateful-set.md, line 38 at r1 (raw file):

Previously, enisoc (Anthony Yeh) wrote…

I think you can delete "if you wish" and "just" to be more direct.

Done.

docs/tasks/manage-stateful-set/scale-stateful-set.md, line 74 at r1 (raw file):

Previously, erictune (Eric Tune) wrote…

Copy foxish's explanation verbatim here rather than linking to issue/

Done.

Comments from Reviewable

devin-donnelly · 2016-12-01T22:01:13Z

docs/tasks/manage-stateful-set/scale-stateful-set.md

+
+With a StatefulSet of size > 1, if there is an unhealthy Pod, there is no way 
+for Kubernetes to know (yet) if it is due to a permanent fault or a transient
+one (upgrade/maintenance/node reboot). If it were a permanent fault, scaling


"If it were a" -> "If the pod is unhealthy due to a permanent fault"

devin-donnelly · 2016-12-01T22:01:36Z

docs/tasks/manage-stateful-set/scale-stateful-set.md

+With a StatefulSet of size > 1, if there is an unhealthy Pod, there is no way 
+for Kubernetes to know (yet) if it is due to a permanent fault or a transient
+one (upgrade/maintenance/node reboot). If it were a permanent fault, scaling
+without paying heed to it may lead to a state where the StatefulSet membership


"without paying heed to it" -> "without correcting the fault"

devin-donnelly · 2016-12-01T22:02:34Z

docs/tasks/manage-stateful-set/scale-stateful-set.md

+one (upgrade/maintenance/node reboot). If it were a permanent fault, scaling
+without paying heed to it may lead to a state where the StatefulSet membership
+drops below a certain minimum number of "replicas" that are needed to function
+correctly, leading to unavailability (or worse).


End the sentence after "correctly". Second sentence: "This may cause your StatefulSet to become unavailable."

If you keep "or worse", explain what "or worse" means; it's kind of ominous but unhelpful as is.

devin-donnelly · 2016-12-01T22:03:28Z

docs/tasks/manage-stateful-set/scale-stateful-set.md

+drops below a certain minimum number of "replicas" that are needed to function
+correctly, leading to unavailability (or worse).
+
+If it were a transient one and the Pod were coming back up shortly, you won't


"If it were a transient one and the Pod were coming back up shortly" -> "If the pod is unhealthy due to a transient fault and the Pod might become available again,"

devin-donnelly · 2016-12-01T22:03:57Z

docs/tasks/manage-stateful-set/scale-stateful-set.md

+correctly, leading to unavailability (or worse).
+
+If it were a transient one and the Pod were coming back up shortly, you won't
+want that to interleave with your scale-up/scale-down operation. Some distributed


"the transient error may interfere with your scale-up/scale-down operation."

janetkuo · 2016-12-02T21:55:13Z

Review status: 0 of 3 files reviewed at latest revision, 13 unresolved discussions.

docs/tasks/manage-stateful-set/scale-stateful-set.md, line 80 at r2 (raw file):

Previously, devin-donnelly wrote…

"If it were a" -> "If the pod is unhealthy due to a permanent fault"

Done.

docs/tasks/manage-stateful-set/scale-stateful-set.md, line 81 at r2 (raw file):

Previously, devin-donnelly wrote…

"without paying heed to it" -> "without correcting the fault"

Done.

docs/tasks/manage-stateful-set/scale-stateful-set.md, line 83 at r2 (raw file):

Previously, devin-donnelly wrote…

End the sentence after "correctly". Second sentence: "This may cause your StatefulSet to become unavailable."

If you keep "or worse", explain what "or worse" means; it's kind of ominous but unhelpful as is.

Done.

docs/tasks/manage-stateful-set/scale-stateful-set.md, line 85 at r2 (raw file):

Previously, devin-donnelly wrote…

"If it were a transient one and the Pod were coming back up shortly" -> "If the pod is unhealthy due to a transient fault and the Pod might become available again,"

Done.

docs/tasks/manage-stateful-set/scale-stateful-set.md, line 86 at r2 (raw file):

Previously, devin-donnelly wrote…

"the transient error may interfere with your scale-up/scale-down operation."

Done.

Comments from Reviewable

devin-donnelly · 2016-12-02T21:58:06Z

Thanks! Merging now.

janetkuo added area/stateful-apps labels Nov 23, 2016

janetkuo added this to the 1.5 milestone Nov 23, 2016

k8s-ci-robot added the cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. label Nov 23, 2016

k8s-github-robot assigned smarterclayton Nov 23, 2016

foxish reviewed Nov 23, 2016

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janetkuo assigned foxish Nov 23, 2016

erictune reviewed Nov 24, 2016

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erictune mentioned this pull request Nov 28, 2016

Make StatefulSets safe during cluster failure kubernetes/enhancements#119

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devin-donnelly added the Tech Review LGTM label Dec 1, 2016

devin-donnelly suggested changes Dec 1, 2016

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devin-donnelly added Docs Review: Open Issues and removed Needs Docs Review labels Dec 1, 2016

janetkuo added 3 commits December 2, 2016 13:37

Add task: scaling stateful sets

09bf6df

Address comments from foxish, enisoc, and erictune

d43cbbe

Address Devin's comments

b770349

devin-donnelly approved these changes Dec 2, 2016

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devin-donnelly added Docs LGTM and removed Docs Review: Open Issues labels Dec 2, 2016

devin-donnelly merged commit 42e33c4 into kubernetes:release-1.5 Dec 2, 2016

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Add Task: Scaling Stateful Sets #1774

Add Task: Scaling Stateful Sets #1774

janetkuo commented Nov 23, 2016 •

edited by thockin

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janetkuo commented Dec 2, 2016

devin-donnelly commented Dec 2, 2016


		### Use `kubectl` to scale Stateful Sets

		#### `kubectl scale` (>= 1.4 release)


		#### Scaling down doesn't not work right

		You cannot scale down a Stateful Set when some of the stateful pods it manages are unhealthy. Scaling down only takes place

Add Task: Scaling Stateful Sets #1774

Add Task: Scaling Stateful Sets #1774

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janetkuo commented Nov 23, 2016 • edited by thockin Loading

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