fix(controllers): replace EtcdMember Pods that reach a terminal phase - #370
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Navigate logical layers of code changes, visualize relationships, and explore their blast radius. 📝 WalkthroughWalkthroughThe controller now detects member-owned Pods in ChangesTerminal Pod Recovery
Priority: ⬆️ High Estimated code review effort: 3 (Moderate) | ~25 minutes Change: Bug fix · Severity of issue fixed: High Sequence Diagram(s)sequenceDiagram
participant EtcdMemberReconciler
participant KubernetesAPI
participant EtcdMemberStatus
EtcdMemberReconciler->>KubernetesAPI: Read member-owned Pod
KubernetesAPI-->>EtcdMemberReconciler: Return Succeeded or Failed Pod
EtcdMemberReconciler->>EtcdMemberStatus: Set MemberReady=False with PodReplacing
EtcdMemberReconciler->>KubernetesAPI: Delete terminal Pod
KubernetesAPI-->>EtcdMemberReconciler: Confirm deletion or NotFound
EtcdMemberReconciler->>EtcdMemberReconciler: Requeue after 2 seconds
Merge Risk: 🟡 Moderate · up to A terminal memory-backed member can be recreated with empty temporary storage under its old identity instead of being replaced. Persist the observed Pod UID or enter replacement directly before merging. 🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
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🧪 Generate unit tests (beta)
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A graceful node shutdown SIGTERMs etcd, which exits 0, and the kubelet moves the Pod to a terminal phase (Succeeded, or Failed on a non-zero exit) without deleting it. The kubelet never restarts containers in a terminal Pod, and the operator manages bare Pods rather than a StatefulSet, so ensurePod — which only recreates on NotFound — treated the Succeeded Pod as present and left the member down permanently. This was seen in production after all nodes of a cluster were rebooted at once: every etcd Pod was Succeeded and etcd never recovered until the Pods were deleted by hand. The crash-loop detector didn't help (it needs 5+ restarts; a clean exit has zero) and neither did the pod-loss detector (it fires only on a missing or UID-changed Pod). Delete an owned Pod that has reached a terminal phase and has no deletionTimestamp, then requeue. The next reconcile recreates it: a PVC-backed member resumes from its data dir with the same member ID; a memory-backed member falls into the existing pod-loss path once the Pod is gone (its tmpfs data was lost, so it is replaced, not recreated). A Pod already terminating is left to finish, so a manual restart, drain, or eviction is untouched. Not quorum-gated: a whole-cluster reboot lands every member here at once and all must be free to recreate. Fixes #368 Assisted-By: LLM Signed-off-by: Andrey Kolkov <androndo@gmail.com>
Deleting a terminal-phase Pod returned before any status write. When the re-creation then failed (missing TLS Secret, quota) updateStatus never ran, so the member kept advertising MemberReady=True with no Pod and inflated the cluster's readyMembers count that the crash-loop quorum gate reads. Set Ready=False with reason PodReplacing in the same pass, keeping the phase and reason the Pod died with, and log the delete like the other destructive paths in Reconcile. Status.PodUID is preserved so the memory pod-loss gate still fires on the next pass. Pin the ownership conjunct of the delete guard with its own test. Assisted-By: LLM Signed-off-by: Andrey Kolkov <androndo@gmail.com>
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The condition was written after the Pod delete, so a conflicting status write (the cluster controller patches member status too) returned an error with the Pod already gone; the retry found nothing terminal and the flip was lost. Split the delete into a predicate and the delete itself, and persist the condition first so a failed write leaves the terminal Pod in place as the retry trigger. Trim the comments to the reasons. Assisted-By: LLM Signed-off-by: Andrey Kolkov <androndo@gmail.com>
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Inline comments:
In `@controllers/etcdmember_controller.go`:
- Around line 174-176: Update the terminal-Pod handling around
setMemberCondition so a memory-backed member with an empty Status.PodUID records
the observed pod.UID before the Pod is deleted; track both the condition and UID
changes when deciding whether to call r.Status().Update. Add a test covering an
initially empty Status.PodUID.
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controllers/etcdmember_controller.gocontrollers/etcdmember_controller_test.go
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Timofei Larkin (lllamnyp)
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Approving. The failure this fixes is real and permanent, and the remedy delegates to paths that already exist rather than inventing a second replacement policy.
On the diagnosis. A Pod in Succeeded/Failed is still an object in the API, so ensurePod — which creates only on NotFound — sees a Pod present and does nothing, while the kubelet never restarts a terminal Pod's containers. Neither existing self-heal path can reach it: etcdContainerStuck needs RestartCount >= 5 on a not-ready container, and the memory Pod-loss detector needs the Pod object missing or UID-changed. Deleting the Pod is the only lever that converts this state into something the controller already knows how to handle, and both outcomes are delegated correctly — PVC-backed resumes from its data dir with the same member ID, memory-backed falls into the Pod-loss path and is replaced with a fresh one.
One small correction to the description, which does not change the fix: buildPod sets no restartPolicy, so it defaults to Always, under which a container exiting 0 is simply restarted and the Pod stays Running. The terminal phase comes from the kubelet's graceful-node-shutdown manager marking the whole Pod terminal (Failed/reason Terminated, or Succeeded on kubelet versions carrying that bug), or from eviction/admission failure. Handling both phases is right either way, and it is also why terminal-phase and crash-loop are disjoint signals rather than overlapping ones.
On the ordering. Writing MemberReady=False before the delete, and returning the status-write error so the delete is never reached on failure, is the right way round and matters more than it looks. The cluster controller sums MemberReady=True into Status.ReadyMembers, and clusterHasQuorumWithout — the gate on the member-destroying crash-loop path — reads that count. A stale-high ready count is exactly what lets a second concurrent failure pass the quorum gate and delete a member when quorum is already gone. Proving the ordering by fault injection rather than by inspection is the right level of rigour for this.
Avoiding ensurePodAbsent here is also correct and worth the comment it got: that helper clears Status.PodUID, which would disarm the memory Pod-loss gate and bring the member back on an empty tmpfs under its old identity.
On not quorum-gating the replacement. Agreed, and it should stay that way. Replacement is non-destructive for PVC-backed members — the PVC, data dir and member ID all survive, and etcd observes a restart rather than a membership change — so a quorum gate would make the exact incident in #368 unrecoverable, since quorum is gone precisely when every member needs replacing. The gate belongs where the destruction is.
Checked separately, both fine:
- A restore-seed member whose Pod is replaced re-runs its restore init container; the restore agent skips when
<datadir>/memberexists, so a replacement does not roll the data dir back to the snapshot. buildPodcan hand a replacement--initial-cluster-state=newwhen the member is the seed with no discovered member ID and no latched ClusterID. That is inert for PVC-backed (etcd ignores it on a non-empty data dir) and unreachable for memory-backed, where the Pod-loss path deletes the member beforeensurePodruns.
Non-blocking follow-ups, filed as #372: the replacement path has no cap or backoff, so a Pod that lands in Failed deterministically churns indefinitely (no data or quorum risk, but it also never escalates to etcdContainerStuck, since each replacement resets RestartCount); Status.PodUID could be backfilled inside the status update the branch already performs, so the memory path stops depending on when status was last persisted; and a reconcile-level negative over a Running Pod would pin explicitly what TestPodInTerminalPhase currently only covers at the predicate.
Verified locally: build, vet and the full controllers suite green.
## What this PR does Bumps the vendored `etcd-operator` from **v0.5.5** to **[v0.5.6](https://github.com/cozystack/etcd-operator/releases/tag/v0.5.6)**. v0.5.6 is a controller-only bug-fix release; the two changes are: - **Terminal-phase `EtcdMember` Pods are replaced** ([etcd-operator#370](cozystack/etcd-operator#370)). A graceful node shutdown SIGTERMs etcd, which exits 0, and the kubelet parks the Pod in `Succeeded` without deleting it. The operator manages bare Pods and only recreated on `NotFound`, so after a whole-cluster reboot every member stayed down until the Pods were deleted by hand. The reconciler now deletes an owned Pod in a terminal phase and lets the next pass recreate it against the same PVC (or, for memory-backed members, through the existing pod-loss re-add path). - **`EtcdCluster` status stays truthful while etcd is unreachable** ([etcd-operator#369](cozystack/etcd-operator#369)). On a converged cluster the learner-promote and auth reconcile paths returned their transient requeue before `updateStatus`, so `Available`/`Degraded` and `readyMembers` froze at the last healthy value and a fully down cluster kept advertising `Available=True`. The status write now always happens, with the requeue carried through it. Package changes are pin-only: - **`etcd-operator`**: `appVersion` → v0.5.6 (image tag derives from it), `ETCD_OPERATOR_REF` → v0.5.6, `tests/deployment_test.yaml` image pins → v0.5.6. - **`etcd-operator-crds`**: `ETCD_OPERATOR_REF` → v0.5.6. `make update` at the new ref produces an empty diff: the five CRDs are byte-identical to v0.5.5, and `charts/etcd-operator/files/manager-role-rules.yaml` did not change, so `templates/rbac.yaml` is untouched. Verified locally: `helm unittest` 18/18 (`etcd-operator`) and 1/1 (`etcd-operator-crds`), `helm lint` clean on both, `helm template` renders `ghcr.io/cozystack/etcd-operator:v0.5.6`, and that tag resolves in ghcr.io. ### Screenshots n/a — no UI changes. ### Downstream repositories Walked the trigger map against the diff. The change is confined to `packages/system/etcd-operator{,-crds}` and touches only version pins: etcd-operator is a system component (not a `packages/apps`/`packages/extra` package the website and TF provider track), no CRD, schema, values, `hack/`, installer or platform values changed. - [x] No downstream repository is affected by this change ### Release note ```release-note chore(etcd-operator): bump to v0.5.6, which replaces EtcdMember Pods left in a terminal phase after a node shutdown and keeps EtcdCluster Available/Degraded conditions truthful while etcd is unreachable ``` <!-- This is an auto-generated comment: release notes by coderabbit.ai --> ## Summary by CodeRabbit * **Updates** * Updated the etcd operator to version 0.5.6. This version is used consistently across the operator deployment and its associated custom resource definitions. <!-- end of auto-generated comment: release notes by coderabbit.ai -->
2 participants
Problem
Fixes #368.
A graceful node shutdown SIGTERMs etcd, which exits 0; the kubelet moves the Pod to a terminal phase (
Succeeded, orFailedon a non-zero exit) without deleting it. The kubelet never restarts containers in a terminal Pod, and the operator manages bare Pods (not a StatefulSet), soEtcdMemberReconciler.ensurePod— which only recreates onNotFound— treated theSucceededPod as present and left the member down permanently.Seen in production: all nodes of a cluster were rebooted at once, every etcd Pod went
Succeeded, and etcd never recovered until the Pods were deleted by hand. Neither existing self-heal caught it:etcdContainerStuck) needsRestartCount >= 5— a clean exit has zero restarts;Fix
Delete an owned Pod in a terminal phase with no
deletionTimestamp, then requeue. The next reconcile recreates it, reusing the existing paths per storage type:ensurePodrecreates against the same PVC; etcd resumes from its data dir with the same member ID.This addresses the issue's five considerations:
etcdContainerStuckpath.Pendinguntil its node returns (a Pending Pod is not terminal, so it is not re-deleted).deletionTimestampset) is left to finish.Tests
TestPodInTerminalPhase— the phase predicate (Running/Pending/Unknown false; Succeeded/Failed true).TestReconcile_ReplacesTerminalPhasePod— PVC-backed: pass 1 deletes theSucceededPod, pass 2 recreates a fresh Pod against the preserved PVC.TestReconcile_MemoryMemberTerminalPodTriggersReplacement— memory-backed: pass 1 deletes the terminal Pod, pass 2 marks the member for replacement and creates no fresh tmpfs Pod.TestDeleteTerminalPod_SkipsPodBeingDeleted— a Pod already terminating is left alone.Verified the two reconcile tests fail against a no-op
deleteTerminalPodand pass with the fix.go vetclean; fullgo test ./...green.Summary by CodeRabbit