How to fix Failing Readiness Probe in Kubernetes

kubectl describe pod <pod-name> -n <namespace> | grep -A 10 "Readiness"
kubectl get pod <pod-name> -n <namespace> -o yaml | grep -A 10 "readinessProbe:"
kubectl get pod <pod-name> -n <namespace> -o jsonpath='{.status.conditions[?(@.type=="Ready")]}'

Readiness: http-get delay=10s timeout=5s period=10s #success=1 #failure=3

kubectl logs <pod-name> -n <namespace> -f
kubectl logs <pod-name> -n <namespace> --tail=100 | grep -i "ready\|waiting\|error"

# Check for repeated failures:
kubectl logs <pod-name> -n <namespace> | head -30  # First log lines
kubectl logs <pod-name> -n <namespace> | tail -30  # Last log lines

# Execute the probe command directly:
kubectl exec -it <pod-name> -n <namespace> -- sh

# For HTTP probe:
curl -v http://localhost:8080/ready
curl -v http://localhost:8080/readiness
echo $?  # Should return 0 and HTTP 200

# For TCP probe:
nc -zv localhost 8080

# For exec probe:
/bin/ready-check.sh

# Check response time:
time curl http://localhost:8080/ready

# From inside the pod:
kubectl exec -it <pod-name> -n <namespace> -- sh

# Check database connectivity:
nc -zv database-host 5432
psql -h database-host -U user -d mydb -c "SELECT 1"

# Check cache/Redis:
redis-cli -h redis-host ping

# Check other services:
curl -v http://api-service:8080/health

# Check DNS:
nslookup database-host
getent hosts database-host

# Patch the deployment:
kubectl patch deployment <name> -n <namespace> -p '{"spec":{"template":{"spec":{"containers":[{"name":"<container>","readinessProbe":{"initialDelaySeconds":60}}]}}}}'

# Or edit YAML:
kubectl edit deployment <name> -n <namespace>

apiVersion: apps/v1
kind: Deployment
metadata:
  name: ready-app
spec:
  template:
    spec:
      containers:
      - name: app
        image: myapp:latest
        readinessProbe:
          httpGet:
            path: /ready
            port: 8080
          initialDelaySeconds: 45  # Wait 45 seconds before first check
          periodSeconds: 10
          failureThreshold: 3

kubectl patch deployment <name> -n <namespace> -p '{"spec":{"template":{"spec":{"containers":[{"name":"<container>","readinessProbe":{"timeoutSeconds":10}}]}}}}'

# Or edit YAML:

readinessProbe:
  httpGet:
    path: /ready
    port: 8080
  initialDelaySeconds: 30
  periodSeconds: 10
  timeoutSeconds: 10  # Increase from default 1 to 10
  failureThreshold: 3

# Python/Flask example:
@app.route('/ready', methods=['GET'])
def readiness():
    """Readiness check: is the app ready to serve traffic?"""
    try:
        # Check if application has completed initialization
        if not app.config.get('initialized'):
            return jsonify({'status': 'not_ready'}), 503
        
        # Check database connectivity
        db.session.execute('SELECT 1')
        
        # Check cache (optional)
        if app.config.get('use_cache'):
            cache.ping()
        
        return jsonify({'status': 'ready'}), 200
    except Exception as e:
        print(f"Readiness check failed: {e}")
        return jsonify({'status': 'error', 'message': str(e)}), 503

readinessProbe:
  httpGet:
    path: /api/external-service/status
    port: 8080

readinessProbe:
  httpGet:
    path: /ready  # Just check if app is initialized
    port: 8080