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server: don't unlink the socket file on listener close - #1564
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Walkthrough
ChangesUnix Listener Socket Retention
Priority: ⬆️ High Estimated code review effort: 2 (Simple) | ~5 minutes Change: Bug fix Suggested reviewers: Merge Risk: ⚪ Minimal · up to
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Check skipped - CodeRabbit’s high-level summary is enabled. |
| Title check | |
The title clearly and concisely describes the main change: preventing the Unix socket file from being unlinked when the listener closes. |
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Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 1 files. |
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Actionable comments posted: 1
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Inline comments:
Review comments at @pkg/server/server.go:
- Line 151: Update the Unix listener shutdown path around
SetUnlinkOnClose(false) and server.Shutdown to remove the socket on graceful
shutdown only if the path still identifies the socket owned by this listener;
preserve a successor’s socket if it has replaced the path.
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pkg/server/server.go
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cc @wizhaoredhat |
🚀 Performance Test ResultsStatus: ❌ Failed Workloads Tested: 2 node-density-cni-0.4.0📊 Kubernetes Workload Metrics Reportnode-density-cni-0.4.0 Performance ResultsGenerated on: 2026-10-19 14:15:47 UTC
🎯 Pod Ready Latency (Main KPI)Report generated by Multus performance testing node-density-cni-0.3.1📊 Kubernetes Workload Metrics Reportnode-density-cni-0.3.1 Performance ResultsGenerated on: 2026-10-19 14:15:47 UTC
🎯 Pod Ready Latency (Main KPI)
Report generated by Multus performance testing Previous Run2026-10-19 07:02:19 UTC🚀 Performance Test ResultsStatus: ✅ Completed Workloads Tested: 2 node-density-cni-0.4.0📊 Kubernetes Workload Metrics Reportnode-density-cni-0.4.0 Performance ResultsGenerated on: 2026-10-19 13:49:30 UTC
🎯 Pod Ready Latency (Main KPI)
Report generated by Multus performance testing node-density-cni-0.3.1📊 Kubernetes Workload Metrics Reportnode-density-cni-0.3.1 Performance ResultsGenerated on: 2026-10-19 13:49:30 UTC
🎯 Pod Ready Latency (Main KPI)
Report generated by Multus performance testing 🤖 Generated by performance-report workflow |
| if err != nil { | ||
| return nil, logging.Errorf("failed to listen on pod info socket: %v", err) | ||
| } | ||
| // Keep the socket file in place when the listener is closed. Go's unix |
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I think the solution for this should be to change the policy rollout to recreate no?
not sure if a daemonset supports that mode like deployment
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nice idea, but daemonset doesn't support it
what important is that they won't co exist, which recreate enforce, but only on upgrade btw,
not on manual pod deletion, where they can co exists
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I'm OK with this.
I just wonder if this biiiiig comment is actually required, or if this can live in the commit msg.
You call, not blocking on it.
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whatever you prefer
i can either drop it or make it succint (will look meanwhile)
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btw maxSurge=0 might control daemonSet, but again not protected when deleting manually
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is this an issue ? same question for the failing lane, will check those once the rest of the PR is lgmted |
| if err != nil { | ||
| return nil, logging.Errorf("failed to listen on pod info socket: %v", err) | ||
| } | ||
| // Keep the socket file in place when the listener is closed. Go's unix |
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I'm OK with this.
I just wonder if this biiiiig comment is actually required, or if this can live in the commit msg.
You call, not blocking on it.
Go's unix listener created by net.Listen unlinks its socket path when the listener is closed. With the graceful-termination delay introduced in v4.3.1 (SigTermCancelAfter = 10s), an old daemon can still be shutting down while its successor has already recreated the socket at the same path. When the old listener finally closes, Go unlinks the path and deletes the successor's live socket file. The new daemon keeps listening on an orphaned inode and clients can no longer connect to /run/multus/multus.sock. Disable the implicit unlink-on-close with SetUnlinkOnClose(false). This is safe because startup cleanup is already handled by FilesystemPreRequirements, which removes the whole socket directory before every listen, so no stale socket files are left behind. Verified on a k8s-1.36 kubevirtci cluster with CNAO's "deploy all components at once" + "deploy all components one by one" spec pair: without the fix the successor's socket file is deleted ~6s after creation and multus-dynamic-networks-controller probes fail with `curl: (7)` forever; with the fix both specs pass and the healthz endpoint answers 200 from inside client pods throughout. Assisted-by: GLM 5.3 Signed-off-by: Or Shoval <oshoval@redhat.com>
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btw this kind is very old Line 8 in 069314b it uses also old k8s to test lets use 0.33 ? |
Makes sense to me, but I don't maintain this code base. |
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thanks guys ! can you please create a release ? |
Problem
When a multus pod is replaced (rolling update, redeploy, test teardown), the
successor daemon's unix socket is sometimes deleted from the node a few
seconds after it starts. The new daemon keeps listening on an orphaned inode,
nothing can connect to
/run/multus/multus.sockanymore, and clients probingthe socket (e.g. multus-dynamic-networks-controller) crashloop until the pod
is manually restarted.
Observed as persistent flaky failures in CNAO's
deploy all components one by onee2e spec with multus v4.3.1.Root cause
A unix listener created by
net.Listenunlinks its socket file when it isclosed.
GetListenerusesnet.Listen, so every graceful daemon shutdownunlinks
/run/multus/multus.sockby path — without checking whether thefile it removes is still the one this daemon created. If a successor daemon
has already bound a new socket at that path, the new socket is deleted.
With the graceful-termination delay introduced in v4.3.1
(
SigTermCancelAfter = 10s), an old daemon can still be shutting down whileits successor is already starting:
listener stays open.
/run/multusand its socket at the samepath (the old listener survives on the now-orphaned old inode).
socket path — deleting the new daemon's socket file.
The race window is the old daemon's graceful-shutdown delay; any successor
daemon that binds the same path during that window gets its socket deleted.
Fix
Disable the implicit unlink-on-close on the listener:
This is safe because socket cleanup is already handled properly at startup:
FilesystemPreRequirementsdoesRemoveAll(socketDir)before every listen,which removes any stale socket file from a previous daemon. The implicit
path-based unlink on close is redundant for cleanup and actively harmful
when a successor has already re-created the socket at the same path.
Verification
Reproduced on a k8s-1.36 kubevirtci cluster with CNAO's
deploy all components at once+deploy all components one by onespecpair (the second deploys multus while the first one's pod is still
terminating):
~6s after creation; the new daemon listens on an orphaned inode; the
dynamic-networks-controller probes fail with
curl: (7)forever; thespec times out waiting for
Available.healthz endpoint answers 200 from inside client pods throughout.
Summary by CodeRabbit