OCPBUGS-100390: UPSTREAM: 21443: Revert "Reuse events between sync loops"

[redhat-chai-bot]

Cherry-pick: etcd memory regression fix for 4.21

Cherry-pick of upstream etcd-io/etcd#21443 — Revert "Reuse events between sync loops"

Problem

etcd 3.6 introduced a memory regression that scales with cluster size (OCPBUGS-76329). The rangeEventsWithReuse optimization held event objects across sync loops, causing unbounded memory growth:

Cluster Size	etcd 3.5 Max RSS	etcd 3.6 Max RSS	Max Change
24 nodes	468 MiB	541 MiB	+15.6%
120 nodes	893 MiB	1.24 GiB	+42.2%
250 nodes	1.13 GiB	2.96 GiB	+162%

Fix

This cherry-picks the upstream revert which:

• Removes the rangeEventsWithReuse function
• Removes the shared evs variable from syncWatchersLoop
• Restores the original rangeEvents and kvsToEvents signatures with contains filtering

Why cherry-pick instead of full rebase

OCP 4.21 etcd is on 3.6.5. A full rebase to 3.6.9+ is complicated by Go version constraints (see openshift/etcd#377 which is held). This targeted cherry-pick addresses the critical memory regression without introducing other changes.

Build and test verification

• go build ./... ✅
• go test ./server/storage/mvcc/... ✅ (11.7s)

References

• Upstream issue: Increased memory usage with 3.6 event reuse etcd-io/etcd#21355
• Upstream fix: [release-3.6] Revert "Reuse events between sync loops" etcd-io/etcd#21443
• Jira: https://redhat.atlassian.net/browse/OCPBUGS-76329
• 4.22 rebase (includes this fix): OCPBUGS-82497: Rebase v3.6.13 for openshift-4.22 #393

---

@sdodson requested in Slack thread

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ci/prow/upstream-e2e	0ff063b	link	false	/test upstream-e2e

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[sdodson]

/jira cherry-pick OCPBUGS-76329

[openshift-ci-robot]

@sdodson: Jira Issue OCPBUGS-76329 has been cloned as Jira Issue OCPBUGS-100390. Will retitle bug to link to clone.
/retitle OCPBUGS-100390: UPSTREAM: 21443: Revert "Reuse events between sync loops"

Details

In response to this:

/jira cherry-pick OCPBUGS-76329

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[openshift-ci-robot]

@redhat-chai-bot: This pull request references Jira Issue OCPBUGS-100390, which is invalid:

• expected dependent Jira Issue OCPBUGS-76329 to be in one of the following states: VERIFIED, RELEASE PENDING, CLOSED (ERRATA), CLOSED (CURRENT RELEASE), CLOSED (DONE), CLOSED (DONE-ERRATA), but it is ON_QA instead

Comment /jira refresh to re-evaluate validity if changes to the Jira bug are made, or edit the title of this pull request to link to a different bug.

The bug has been updated to refer to the pull request using the external bug tracker.

Details

In response to this:

Cherry-pick: etcd memory regression fix for 4.21

Cherry-pick of upstream etcd-io/etcd#21443 — Revert "Reuse events between sync loops"

Problem

etcd 3.6 introduced a memory regression that scales with cluster size (OCPBUGS-76329). The rangeEventsWithReuse optimization held event objects across sync loops, causing unbounded memory growth:

Cluster Size	etcd 3.5 Max RSS	etcd 3.6 Max RSS	Max Change
24 nodes	468 MiB	541 MiB	+15.6%
120 nodes	893 MiB	1.24 GiB	+42.2%
250 nodes	1.13 GiB	2.96 GiB	+162%

Fix

This cherry-picks the upstream revert which:

• Removes the rangeEventsWithReuse function
• Removes the shared evs variable from syncWatchersLoop
• Restores the original rangeEvents and kvsToEvents signatures with contains filtering

Why cherry-pick instead of full rebase

OCP 4.21 etcd is on 3.6.5. A full rebase to 3.6.9+ is complicated by Go version constraints (see openshift/etcd#377 which is held). This targeted cherry-pick addresses the critical memory regression without introducing other changes.

Build and test verification

• go build ./... ✅
• go test ./server/storage/mvcc/... ✅ (11.7s)

References

• Upstream issue: Increased memory usage with 3.6 event reuse etcd-io/etcd#21355
• Upstream fix: [release-3.6] Revert "Reuse events between sync loops" etcd-io/etcd#21443
• Jira: https://redhat.atlassian.net/browse/OCPBUGS-76329
• 4.22 rebase (includes this fix): OCPBUGS-82497: Rebase v3.6.13 for openshift-4.22 #393

---

@sdodson requested in Slack thread

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[sdodson]

/jira refresh

[openshift-ci-robot]

@sdodson: This pull request references Jira Issue OCPBUGS-100390, which is valid. The bug has been moved to the POST state.

7 validation(s) were run on this bug

• bug is open, matching expected state (open)
• bug target version (4.21.z) matches configured target version for branch (4.21.z)
• bug is in the state New, which is one of the valid states (NEW, ASSIGNED, POST)
• release note text is set and does not match the template
• dependent bug Jira Issue OCPBUGS-76329 is in the state Verified, which is one of the valid states (VERIFIED, RELEASE PENDING, CLOSED (ERRATA), CLOSED (CURRENT RELEASE), CLOSED (DONE), CLOSED (DONE-ERRATA))
• dependent Jira Issue OCPBUGS-76329 targets the "4.22.0" version, which is one of the valid target versions: 4.22.0
• bug has dependents

Details

In response to this:

/jira refresh

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[sdodson]

/verified by @mcornea on 4.22, assume the same holds true here

[openshift-ci-robot]

@sdodson: This PR has been marked as verified by @mcornea on 4.22,assume the same holds true here.

Details

In response to this:

/verified by @mcornea on 4.22, assume the same holds true here

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[openshift-ci-robot]

@redhat-chai-bot: Jira Issue Verification Checks: Jira Issue OCPBUGS-100390
✔️ This pull request was pre-merge verified.
✔️ All associated pull requests have merged.
✔️ All associated, merged pull requests were pre-merge verified.

Jira Issue OCPBUGS-100390 has been moved to the MODIFIED state and will move to the VERIFIED state when the change is available in an accepted nightly payload. 🕓

Details

In response to this:

Cherry-pick: etcd memory regression fix for 4.21

Cherry-pick of upstream etcd-io/etcd#21443 — Revert "Reuse events between sync loops"

Problem

etcd 3.6 introduced a memory regression that scales with cluster size (OCPBUGS-76329). The rangeEventsWithReuse optimization held event objects across sync loops, causing unbounded memory growth:

Cluster Size	etcd 3.5 Max RSS	etcd 3.6 Max RSS	Max Change
24 nodes	468 MiB	541 MiB	+15.6%
120 nodes	893 MiB	1.24 GiB	+42.2%
250 nodes	1.13 GiB	2.96 GiB	+162%

Fix

This cherry-picks the upstream revert which:

• Removes the rangeEventsWithReuse function
• Removes the shared evs variable from syncWatchersLoop
• Restores the original rangeEvents and kvsToEvents signatures with contains filtering

Why cherry-pick instead of full rebase

OCP 4.21 etcd is on 3.6.5. A full rebase to 3.6.9+ is complicated by Go version constraints (see openshift/etcd#377 which is held). This targeted cherry-pick addresses the critical memory regression without introducing other changes.

Build and test verification

• go build ./... ✅
• go test ./server/storage/mvcc/... ✅ (11.7s)

References

• Upstream issue: Increased memory usage with 3.6 event reuse etcd-io/etcd#21355
• Upstream fix: [release-3.6] Revert "Reuse events between sync loops" etcd-io/etcd#21443
• Jira: https://redhat.atlassian.net/browse/OCPBUGS-76329
• 4.22 rebase (includes this fix): OCPBUGS-82497: Rebase v3.6.13 for openshift-4.22 #393

---

@sdodson requested in Slack thread

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