etcdserver: separate "raft log compact" from snapshot

[clement2026]

Part of #17098. This PR separates "raft log compact" from snapshot.

Changes

• Introduce a new variable CompactRaftLogEveryNApplies to control how often raft log is compacted
• Make CompactRaftLogEveryNApplies tunable.
• Fix the failing test case TestV3WatchRestoreSnapshotUnsync by setting CompactRaftLogEveryNApplies to 1, ensuring compaction occurs after each snapshot.

Need Help

This PR also breaks some e2e test cases:

• TestRecoverSnapshotBackend
• TestMixVersionsSnapshotByMockingPartition

because they expect a compaction right after the snapshot to ensure a snapshot is sent to their followers.

I haven’t figured out a fix yet, other than making CompactRaftLogEveryNApplies a command-line argument, but that doesn’t seem ideal.

To Do

• Fix failing tests
• Benchmark different values for CompactRaftLogEveryNApplies: 1, 10, 100, 1000, and choose the best on as default value.

[k8s-ci-robot]

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[k8s-ci-robot]

Hi @clement2026. Thanks for your PR.

I'm waiting for a etcd-io 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.

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[clement2026]

How do you guys usually find the failing test case in the logs?

I tried the following keywords but no luck this time, any tips?

Error Trace, failed to, fatal

logs_26517259659.zip

[ivanvc]

Hi @clement2026, search for FAIL in 5_Run set -euo pipefail.txt. It looks like TestMixVersionsSnapshotByMockingPartition is the one failing.

[clement2026]

Hi @clement2026, search for FAIL in 5_Run set -euo pipefail.txt. It looks like TestMixVersionsSnapshotByMockingPartition is the one failing.

Thanks a lot! The all-caps ‘FAIL’ is super helpful.

[k8s-ci-robot]

PR needs rebase.

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.