Debug OOM Kills in Kubernetes

Problem

Your pods are being killed with OOMKilled status and you need to find out why.

Step 1: Identify the OOM Kill

kubectl get pods -o wide
kubectl describe pod <pod-name>

Look for Last State: Terminated with Reason: OOMKilled in the output.

Step 2: Check Resource Limits

kubectl get pod <pod-name> -o jsonpath='{.spec.containers[*].resources}'

If no memory limits are set, the pod can consume all node memory before being killed by the kernel OOM killer.

Step 3: Analyze Memory Usage

Use metrics-server or Prometheus to check actual memory consumption:

kubectl top pod <pod-name> --containers

Step 4: Fix the Issue

Option A: Increase memory limits (if the app legitimately needs more):

resources:
  requests:
    memory: "256Mi"
  limits:
    memory: "512Mi"

Option B: Fix the memory leak in your application. Common causes:

• Unbounded caches
• Connection pool leaks
• Large file processing without streaming

Prevention

Set resource requests and limits on all containers. Use a LimitRange to enforce defaults at the namespace level.