Kubernetes Pod Restarted Due to Memory Issue

Problem

How can you check if a Kubernetes pod has restarted due to a memory issue or any other issue?

Solution

Follow the steps below to determine whether a pod in your Kubernetes cluster has restarted due to a memory issue.

Use the following command to gather detailed information about the pod. This will include the status, restart count, and the reason for any previous restarts.
```
kubectl describe pod <pod_name>
```
For example:
```
kubectl describe pod nextgen-gw-0
```

Analyze the Output, specifically under the Last State section:

vprobe:
  Container ID:   containerd://40c8585cf88dc7d0dd4e43560dc631ef559b0c92e6d5d429719a384aaea77777
  Image:          us-central1-docker.pkg.dev/opsramp-registry/gateway-cluster-images/vprobe:17.0.0
  Image ID:       us-central1-docker.pkg.dev/opsramp-registry/gateway-cluster-images/vprobe@sha256:8de1a98c3c14307fa4882c7e7422a1a4e4d507d2bbc454b53f905062b665e9d2
  Port:           <none>
  Host Port:      <none>
  State:          Running
    Started:      Mon, 29 Jan 2024 12:01:30 +0530
  Last State:     Terminated
    Reason:       OOMKilled
    Exit Code:    137
    Started:      Mon, 29 Jan 2024 12:00:42 +0530
    Finished:     Mon, 29 Jan 2024 12:01:29 +0530
  Ready:          True
  Restart Count:  1

In the Last State section, look for the following indications:
- Reason: The reason listed as OOMKilled means the pod was killed because it ran out of memory.
- Exit Code: An exit code of 137 indicates the container was forcefully stopped due to an out-of-memory condition.

Conclusion

If the pod’s last state shows Reason: OOMKilled and Exit Code: 137, this confirms that the pod was restarted due to insufficient memory (Out of Memory or OOM condition). You may need to allocate more memory resources to this pod or optimize the workload to prevent this from happening again.