NO-JIRA: Fix static pod pruning logic for non-contiguous set of revisions

[grandeit]

Fix static pod pruning logic for non-contiguous set of revisions

Problem

The PruneController contains a logic bug in revisionsToKeep() that prevents pruning when the protected revision set is non-contiguous but spans from revision 1 to LatestAvailableRevision.

Scenario that triggers the bug:
Node has very old LastFailedRevision: 5
Cluster is now at LatestAvailableRevision: 100
Limits are failedRevisionLimit: 5, succeededRevisionLimit: 5
Protected set becomes {1,2,3,4,5,96,97,98,99,100} (10 revisions)

The buggy logic sees:
First element: 1
Last element: 100
Returns keepAll = true -> No pruning happens.
This causes a lot of revision-status-* ConfigMaps (and their owned ConfigMaps) to accumulate until a later failed revision eventually removes the first revision from the set.

Solution

Check if the set has exactly LatestAvailableRevision elements before triggering the keepAll optimization. This ensures that the set has no gaps and is in-fact contiguous.

Testing

Added test case: "prunes non-contiguous set (keeps 1-10 and 96-100, prunes 11-95)" that verifies:

Two nodes with LastFailedRevision: 5 and LastFailedRevision: 10
CurrentRevision: 100 on both nodes
LatestAvailableRevision: 100

Protected set: {1,2,3,4,5,6,7,8,9,10,96,97,98,99,100} (15 revisions)
Revisions 11 - 95 are pruned.
keepAll optimization does not trigger.

[openshift-ci-robot]

@grandeit: This pull request explicitly references no jira issue.

In response to this:

Fix static pod pruning logic for non-contiguous set of revisions

Problem

The PruneController contains a logic bug in revisionsToKeep() that prevents pruning when the protected revision set is non-contiguous but spans from revision 1 to LatestAvailableRevision.

Scenario that triggers the bug:
Node has very old LastFailedRevision: 5
Cluster is now at LatestAvailableRevision: 100
Limits are failedRevisionLimit: 5, succeededRevisionLimit: 5
Protected set becomes {1,2,3,4,5,96,97,98,99,100} (10 revisions)

The buggy logic sees:
First element: 1
Last element: 100
Returns keepAll = true -> No pruning happens.
This causes a lot of revision-status-* ConfigMaps (and their owned ConfigMaps) to accumulate until a later failed revision eventually removes the first revision from the set.

Solution

Check if the set has exactly LatestAvailableRevision elements before triggering the keepAll optimization. This ensures that the set has no gaps and is in-fact contiguous.

Testing

Added test case: "prunes non-contiguous set (keeps 1-10 and 96-100, prunes 11-95)" that verifies:

Two nodes with LastFailedRevision: 5 and LastFailedRevision: 10
CurrentRevision: 100 on both nodes
LatestAvailableRevision: 100

Protected set: {1,2,3,4,5,6,7,8,9,10,96,97,98,99,100} (15 revisions)
Revisions 11 - 95 are pruned.
keepAll optimization does not trigger.

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[openshift-ci]

Hi @grandeit. Thanks for your PR.

I'm waiting for a github.com member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[openshift-ci]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: grandeit
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