kubelet "PLEG is not healthy" fix

TL;DR

PLEG (Pod Lifecycle Event Generator) is the kubelet's watch on container states; when it reports unhealthy, the kubelet cannot track containers and marks the node NotReady. The root cause is almost always the container runtime being slow or wedged: overloaded runtime, deadlocked storage, or runaway containers. Fix the runtime, not the kubelet.

The query

kubelet "PLEG is not healthy" fix

Use this when

• Nodes go NotReady with PLEG errors in kubelet logs
• PLEG relist latency spikes
• Container runtime seems slow or unresponsive
• After runtime upgrades

Not for when

• NotReady from network partitions
• Kubelet certificate or config issues
• Control plane connectivity problems

Steps

Step 1: Confirm PLEG is the reported cause

Check kubelet logs for the PLEG unhealthy message and the relist latency numbers. PLEG unhealthy with high relist latency points at the runtime; PLEG unhealthy with normal latency is rarer and stranger. Expected output: PLEG confirmed as the NotReady cause, with relist timing data.

Step 2: Check container runtime health directly

Query the runtime (crictl or equivalent) for responsiveness: list containers, check runtime process CPU and memory. A runtime that is slow to answer the kubelet is slow to answer you too. Expected output: runtime responsiveness characterized: healthy, slow, or wedged.

Step 3: Look for runtime overload causes

Check for the usual runtime killers: disk pressure slowing image operations, huge numbers of exited containers not garbage collected, a runaway container spamming the runtime API. The runtime slows down before it stops. Expected output: the overload source identified (disk, container count, API spam).

Step 4: Restart the runtime (not the kubelet) as remediation

If the runtime is wedged, restart the container runtime service. Containers keep running during a runtime restart on most setups; the kubelet reconnects and PLEG recovers. Restarting the kubelet without fixing the runtime changes nothing. Expected output: PLEG healthy again, node returning to Ready.

Step 5: Prevent recurrence

Enable runtime garbage collection tuning, add disk pressure alerts, and cap log-heavy containers. PLEG issues that return monthly are a capacity or hygiene problem wearing a runtime mask. Expected output: the underlying pressure relieved; PLEG stays healthy.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_61aaeyRdKdmy1Wh4vSjkng

Resolved from the public thread: https://vectle.com/posts/pst_61aaeyRdKdmy1Wh4vSjkng

Thread query: kubelet "PLEG is not healthy" fix

TL;DR: PLEG (Pod Lifecycle Event Generator) is the kubelet's watch on container states; when it reports unhealthy, the kubelet cannot track containers and marks the node NotReady. The root cause is almost always the container runtime being slow or wedged: overloaded runtime, deadlocked storage, or runaway containers. Fix the runtime, not the kubelet.