What is Kubernetes Pod Overcommit?

Question

Accepted Answer

**Overcommit** — allocate more resources than physically available.

```yaml
# Node with overcommit
apiVersion: v1
kind: Node
metadata:
  name: node-1
  labels:
    node-type: overcommit
spec:
  taints: []
---
# Pods requesting more than node capacity
apiVersion: apps/v1
kind: Deployment
metadata:
  name: overcommit-app
spec:
  replicas: 20
  template:
    metadata:
      labels:
        app: overcommit
    spec:
      containers:
      - name: app
        image: nginx:latest
        resources:
          requests:
            cpu: "500m"   # Total: 20 * 500m = 10 CPU
            memory: "256Mi" # Total: 20 * 256Mi = 5Gi
          limits:
            cpu: "1000m"
            memory: "512Mi"
```

```bash
# Check node capacity vs allocated
kubectl describe node node-1 | grep -A 5 "Allocated resources"

# Check overcommit ratio
kubectl get node node-1 -o jsonpath='{.status.capacity}' | jq
kubectl get node node-1 -o jsonpath='{.status.allocatable}' | jq

# Check actual resource usage
kubectl top nodes
kubectl top pods --sort-by=cpu

# Monitor resource pressure
kubectl get nodes -o custom-columns=NAME:.metadata.name,MEMORY_PRESSURE:.status.conditions[?(@.type=="MemoryPressure")].status
kubectl get nodes -o custom-columns=NAME:.metadata.name,CPU_PRESSURE:.status.conditions[?(@.type=="PIDPressure")].status

# Check eviction events
kubectl get events --field-selector reason=Evicted
```

**Overcommit Strategies:**
- requests < limits: overcommit ratio.
- Default limits: LimitRange.
- QoS classes: Burstable, BestEffort.

**Risks:**
- Memory overcommit → OOM kills.
- CPU overcommit → throttling.
- Node pressure → Pod eviction.

DevOps: What is Kubernetes Pod Overcommit?