Kubernetes Probes Liveness Readiness

startupProbe:
  httpGet:
    path: /health
    port: 3000
  failureThreshold: 30     # 30 × 10s = 300s max startup time
  periodSeconds: 10

livenessProbe:
  httpGet:
    path: /health
    port: 3000
  initialDelaySeconds: 5
  periodSeconds: 15
  timeoutSeconds: 3
  failureThreshold: 3      # 3 failures = restart
  successThreshold: 1

readinessProbe:
  httpGet:
    path: /ready
    port: 3000
  initialDelaySeconds: 5
  periodSeconds: 5
  timeoutSeconds: 2
  failureThreshold: 3
  successThreshold: 1

// /health — liveness (is the process alive?)
app.get('/health', (req, res) => {
  res.status(200).json({ status: 'alive' });
});

// /ready — readiness (can we handle requests?)
app.get('/ready', async (req, res) => {
  try {
    // Check database
    await db.query('SELECT 1');
    // Check Redis
    await redis.ping();
    // Check critical dependencies
    res.status(200).json({ status: 'ready' });
  } catch (error) {
    res.status(503).json({ status: 'not ready', error: error.message });
  }
});

livenessProbe:
  httpGet:
    path: /health
    port: 3000
    httpHeaders:
      - name: Authorization
        value: Bearer internal-token

livenessProbe:
  tcpSocket:
    port: 5432

livenessProbe:
  exec:
    command:
      - /bin/sh
      - -c
      - pg_isready -U postgres

livenessProbe:
  grpc:
    port: 50051
    service: my.health.v1.Health

apiVersion: apps/v1
kind: Deployment
metadata:
  name: api
spec:
  replicas: 3
  template:
    spec:
      containers:
        - name: api
          image: my-api:v2.0
          ports:
            - containerPort: 3000

          # Wait up to 5 minutes for startup
          startupProbe:
            httpGet:
              path: /health
              port: 3000
            failureThreshold: 30
            periodSeconds: 10

          # Check if process is alive (every 15s)
          livenessProbe:
            httpGet:
              path: /health
              port: 3000
            periodSeconds: 15
            timeoutSeconds: 3
            failureThreshold: 3

          # Check if ready for traffic (every 5s)
          readinessProbe:
            httpGet:
              path: /ready
              port: 3000
            periodSeconds: 5
            timeoutSeconds: 2
            failureThreshold: 3

          resources:
            requests:
              cpu: 200m
              memory: 256Mi
            limits:
              cpu: "1"
              memory: 512Mi

# Check probe status
kubectl describe pod my-pod | grep -A10 "Liveness\|Readiness\|Startup"

# Check events for probe failures
kubectl get events --field-selector involvedObject.name=my-pod

# Test endpoint manually
kubectl exec my-pod -- curl -sf http://localhost:3000/health
kubectl exec my-pod -- curl -sf http://localhost:3000/ready