[TEP-0135] Validate multiple PVC-based Workspaces in TaskRuns

[QuanZhang-William]

Prior to this commit, we only validate that 1 PVC is allowed to be binded to a TaskRun in AffinityAssistantPerWorkspace coschedule mode. The validation was skipped when there is no affinity assistant presents in the TaskRun (i.e. in standalone TaskRun or in AffinityAssistantDisabled coschedule mode). This commit adds the missing validation.

This commit also updates workspace related documentation.

/kind bug

Changes

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[QuanZhang-William]

/test pull-tekton-pipeline-beta-integration-tests
/test pull-tekton-pipeline-integration-tests

due to timeout

[lbernick]

Previously, with affinity assistant disabled, we let taskrun pods get scheduled by the kube scheduler, and they could non deterministically fail if a taskrun was bound to multiple pvcs, depending on how the pods ended up being scheduled. It sounds like this commit is preventing this from happening at all by rejecting these taskruns when the affinity assistant is disabled? Is this what you intended? I think a validation failure may be the better choice here, although this isn't backwards compatible; curious what others think

[QuanZhang-William]

Previously, with affinity assistant disabled, we let taskrun pods get scheduled by the kube scheduler, and they could non deterministically fail if a taskrun was bound to multiple pvcs, depending on how the pods ended up being scheduled. It sounds like this commit is preventing this from happening at all by rejecting these taskruns when the affinity assistant is disabled? Is this what you intended? I think a validation failure may be the better choice here, although this isn't backwards compatible; curious what others think

Yeah, you are right. I think ideally the validation should fail a standalone TaskRun with multiple PVCs due to potential AZ conflict.

And I missed that prior to TEP-0135, we do allow standalone TaskRun with multiple PVC here, so this change is backward incompatible. Making this change probably needs some discussion across OSS.

I would suggest that we do not merge this PR for now and leave it open to discussion. I will create a separate one just to adding documentation. WDYT?

[QuanZhang-William]

/hold

[lbernick]

I would suggest that we do not merge this PR for now and leave it open to discussion. I will create a separate one just to adding documentation. WDYT?

SGTM!

[tekton-robot]

@QuanZhang-William: PR needs rebase.

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[jerop]

@QuanZhang-William are you still working on this?

(cleaning up old pull requests)

[QuanZhang-William]

@jerop. Thanks for the reminder. This PR introduces backward incompatible changes; and we don't have user request to add validation for >1 PVCs binded to a TaskRun. We can close this PR for now.

/close

[tekton-robot]

@QuanZhang-William: Closed this PR.

In response to this:

@jerop. Thanks for the reminder. This PR introduces backward incompatible changes; and we don't have user request to add validation for >1 PVCs binded to a TaskRun. We can close this PR for now.

/close

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