Add toleration with toleration seconds condition #24041

zhouya0 · 2020-09-22T07:07:17Z

This PR adds the condition that the tolerations with toleration seconds.
Ref: kubernetes/kubernetes#92170 (comment)

zhouya0 · 2020-09-22T07:11:20Z

/assign @alculquicondor

netlify · 2020-09-22T07:18:56Z

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alculquicondor · 2020-09-22T14:30:40Z

content/en/docs/concepts/scheduling-eviction/taint-and-toleration.md

@@ -101,6 +101,9 @@ effect `PreferNoSchedule` then Kubernetes will *try* to not schedule the pod ont
 * if there is at least one un-ignored taint with effect `NoExecute` then the pod will be evicted from
 the node (if it is already running on the node), and will not be
 scheduled onto the node (if it is not yet running on the node).
+* if there is only one tolerated taint with effect `NoExecute` then the pod will still be scheduled onto the node even if


This makes very little sense, sorry.

I think this should be pointed out as a note to the following paragraphs, which describe the tolerationSeconds functionality. There is a toleration anyways, so the third bullet applies, thus the pod can be scheduled.

@zhouya0 I'm afraid I agree with @alculquicondor

Was there a part of the page you found confusing? Maybe knowing that will help someone propose a different change that still reduces the confusion you noticed.

Context: kubernetes/kubernetes#92170

More specifically, kubernetes/kubernetes#92170 (comment)

@alculquicondor @sftim
I followed your suggestions. Please review this again :)

k8s-ci-robot · 2020-09-28T03:13:40Z

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alculquicondor · 2020-09-28T15:34:44Z

content/en/docs/concepts/scheduling-eviction/taint-and-toleration.md

@@ -148,6 +148,14 @@ means that if this pod is running and a matching taint is added to the node, the
 the pod will stay bound to the node for 3600 seconds, and then be evicted. If the
 taint is removed before that time, the pod will not be evicted.

+{{< note >}}
+The evicted pod with `tolerationSeconds` field has the possibility to be scheduled to the prior node again. To avoid such behavior:


I think we are lacking some subsections for the whole "concepts" section. @sftim, could you advice?

In particular, I feel like there should be subtitle before line 132.

Other than that, we have to stress the fact that, even with "tolerationSeconds", this is still a toleration, and for that reason the Pod can get scheduled in the same node again.

Instead of "to avoid such behavior", I would say "If this is not what you want", then "you can add a NoSchedule taint additionally to the NoExecute taint".

Then, I don't think you have to distinguish system-level taints (what is that anyways?). Only the second point is relevant.

Sure, feel free to add a heading before line 132 - no objection from me for doing that.

The problem is that then that heading seems isolated. We don't have a heading for "taints" or "tolerations". But maybe we can fix that in a follow up.

I think system-level taints is like node.kubernetes.io/unreachable when node is down. And controller will add both NoExcute and NoSchedule taint to the node.

That's already covered in https://kubernetes.io/docs/concepts/scheduling-eviction/taint-and-toleration/#taint-nodes-by-condition

The fact that they are added automatically doesn't change how you write tolerations for them :)

BTW, PR #25998 is improving some of the documentation in this area.

alculquicondor · 2020-10-22T14:17:26Z

ping for the last review comments

zhouya0 · 2020-10-23T01:57:21Z

ping for the last review comments

Sorry I have to say, with my poor english, I can't do Other than that, we have to stress the fact that, even with "tolerationSeconds", this is still a toleration, and for that reason the Pod can get scheduled in the same node again. in a standard format.

I'll leave this to other contributors :)

alculquicondor · 2020-10-23T14:05:10Z

Thanks for the progress @zhouya0

sftim

@zhouya0 this proposed wording is not quite idiomatic English. I have guessed at what you meant to say and proposed another way to write that. How do these suggestions look?

sftim · 2021-01-12T18:21:14Z

content/en/docs/concepts/scheduling-eviction/taint-and-toleration.md

+- If the node is tainted by system admin, the best practice is to apply both `NoExecute` and `NoSchedule` taints; otherwise, the pod may be
+scheduled and evicted back and forth.


Suggested change

- If the node is tainted by system admin, the best practice is to apply both `NoExecute` and `NoSchedule` taints; otherwise, the pod may be

scheduled and evicted back and forth.

- If you are setting a `NoExecute` taint manually on a node, you should normally also

set `NoSchedule`. Otherwise, any new Pod that could run on this node may be scheduled

onto, it but then immediately face eviction because of the `NoExecute` taint.

sftim · 2021-01-12T18:21:17Z

content/en/docs/concepts/scheduling-eviction/taint-and-toleration.md

+- If the node is added system-level taints, Kubernetes will be responsible for applying `NoExecute` taint, as well as `Noschedule` taint.
+So the pod won't be scheduled to the prior node.


@zhouya0 is this another way of writing what you meant?

Suggested change

- If the node is added system-level taints, Kubernetes will be responsible for applying `NoExecute` taint, as well as `Noschedule` taint.

So the pod won't be scheduled to the prior node.

- If the node is tainted based on kubelet or node status , Kubernetes is responsible for applying the `NoExecute` and `NoSchedule` taints. These taints prevent the scheduler placing the replacement Pod onto the same node.

kbhawkey · 2021-02-28T00:57:05Z

Hi @zhouya0 .
Thanks for contributing!
What do you think about accepting the suggested changes?

tengqm · 2021-03-29T01:27:24Z

/close
No response from author for a long ... time.

k8s-ci-robot · 2021-03-29T01:27:33Z

@tengqm: Closed this PR.

In response to this:

/close
No response from author for a long ... time.

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k8s-ci-robot added cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. size/XS Denotes a PR that changes 0-9 lines, ignoring generated files. labels Sep 22, 2020

k8s-ci-robot requested review from davidopp and kevin-wangzefeng September 22, 2020 07:07

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zhouya0 force-pushed the add_toleration_seconds_condition branch 2 times, most recently from 0012f6b to ad4d75f Compare September 22, 2020 07:10

k8s-ci-robot assigned alculquicondor Sep 22, 2020

alculquicondor reviewed Sep 22, 2020

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Add toleration seconds condition

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zhouya0 force-pushed the add_toleration_seconds_condition branch from ad4d75f to 3409144 Compare September 28, 2020 03:13

alculquicondor reviewed Sep 28, 2020

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alculquicondor mentioned this pull request Oct 23, 2020

Scheduler should care toleration seconds kubernetes/kubernetes#92170

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Add toleration with toleration seconds condition #24041

Add toleration with toleration seconds condition #24041

zhouya0 commented Sep 22, 2020

zhouya0 commented Sep 22, 2020

netlify bot commented Sep 22, 2020

netlify bot commented Sep 22, 2020 •

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alculquicondor Sep 22, 2020

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zhouya0 Sep 28, 2020

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alculquicondor Sep 28, 2020

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zhouya0 Sep 29, 2020

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sftim Jan 12, 2021

alculquicondor commented Oct 22, 2020

zhouya0 commented Oct 23, 2020

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sftim Jan 12, 2021

kbhawkey commented Feb 28, 2021

tengqm commented Mar 29, 2021

k8s-ci-robot commented Mar 29, 2021

		- If the node is tainted by system admin, the best practice is to apply both `NoExecute` and `NoSchedule` taints; otherwise, the pod may be
		scheduled and evicted back and forth.

-- If the node is tainted by system admin, the best practice is to apply both `NoExecute` and `NoSchedule` taints; otherwise, the pod may be
-scheduled and evicted back and forth.
+- If you are setting a `NoExecute` taint manually on a node, you should normally also
+  set `NoSchedule`. Otherwise, any new Pod that could run on this node may be scheduled
+  onto, it but then immediately face eviction because of the `NoExecute` taint.

		- If the node is added system-level taints, Kubernetes will be responsible for applying `NoExecute` taint, as well as `Noschedule` taint.
		So the pod won't be scheduled to the prior node.

	- If the node is added system-level taints, Kubernetes will be responsible for applying `NoExecute` taint, as well as `Noschedule` taint.
	So the pod won't be scheduled to the prior node.
	- If the node is tainted based on kubelet or node status , Kubernetes is responsible for applying the `NoExecute` and `NoSchedule` taints. These taints prevent the scheduler placing the replacement Pod onto the same node.

Add toleration with toleration seconds condition #24041

Add toleration with toleration seconds condition #24041

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zhouya0 commented Sep 22, 2020

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alculquicondor commented Oct 22, 2020

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