What is Kubernetes Pod Disruption Budget?

Question

Accepted Answer

**PDB** — limit voluntary disruptions for availability.

```yaml
apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  name: myapp-pdb
spec:
  minAvailable: 2  # or maxUnavailable: 1
  selector:
    matchLabels:
      app: myapp
---
# Percentage-based
apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  name: critical-pdb
spec:
  maxUnavailable: "10%"
  selector:
    matchLabels:
      app: critical
  unhealthyPodEvictionPolicy: AlwaysAllow
```

```bash
# Commands
kubectl get pdb
kubectl describe pdb myapp-pdb

# Check disruption budget status
kubectl get pdb -o wide
kubectl get pdb myapp-pdb -o jsonpath='{.status}' | jq

# Test disruption
kubectl drain node-1 --ignore-daemonsets --delete-emptydir-data --force

# Verify allowed disruptions
kubectl get pdb myapp-pdb -o jsonpath='{.status.disruptionsAllowed}'

# Check current Pod count vs budget
kubectl get pdb myapp-pdb -o jsonpath='{.status.currentHealthy}/{.status.desiredHealthy}'
```

**Disruptions:**
- Voluntary: drain, delete, scaling down.
- Involuntary: node crash, OOM kill.

**Policies:**
- minAvailable: minimum Pods must be running.
- maxUnavailable: maximum Pods can be down.

**Best Practices:**
- Use for critical workloads.
- Set conservative values for databases.
- Test with `kubectl drain`.

DevOps: What is Kubernetes Pod Disruption Budget?