Fine-Tuning Probes with Configuration Options

Let's put these concepts into practice by creating a Deployment that uses both liveness and readiness probes. We will use a simple application that exposes an HTTP endpoint for health checks.

kubectl apply -f - <
---
# create a temporary namespace to perform our test
apiVersion: v1
kind: Namespace
metadata:
  name: healthcheck
---
# create a Deployment with liveness and readiness probes
apiVersion: apps/v1
kind: Deployment
metadata:
  name: stateless-flask
  namespace: healthcheck
spec:
  replicas: 1
  selector:
    matchLabels:
      app: stateless-flask
  template:
    metadata:
      labels:
        app: stateless-flask
    spec:
      containers:
      - name: stateless-flask
        image: eon01/stateless-flask
        ports:
        - containerPort: 5000
        livenessProbe:
          exec:
            command:
            - python3
            - -c
            - |
              import urllib.request, sys
              from datetime import datetime

              timestamp = datetime.now().strftime('%Y-%m-%d %H:%M:%S')

              try:
                  urllib.request.urlopen('http://example.com', timeout=2)
                  # Write to container's main process stdout
                  with open('/proc/1/fd/1', 'w') as f:
                      f.write(f"{timestamp} - Liveness probe: example.com is reachable\n")
                  sys.exit(0)
              except Exception as e:
                  # Write to container's main process stderr
                  with open('/proc/1/fd/2', 'w') as f:
                      f.write(f"{timestamp} - Liveness probe: Cannot reach example.com - {str(e)}\n")
                  sys.exit(1)
          initialDelaySeconds: 5
          periodSeconds: 5
          timeoutSeconds: 3
          successThreshold: 1
          failureThreshold: 3
        readinessProbe:
          httpGet:
            path: /tasks
            port: 5000
          initialDelaySeconds: 10
          periodSeconds: 15
          timeoutSeconds: 10
          successThreshold: 1
          failureThreshold: 15
        # terminationGracePeriodSeconds: 10
EOF

Our liveness probe uses an exec mechanism that runs a Python script to check if example.com is reachable. If it is, the probe succeeds; otherwise, it fails.

The script is as follows:

import urllib.request, sys
from datetime import datetime
timestamp = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
try:
    urllib.request.urlopen('http://example.com', timeout=2)
    # Write to container's main process stdout
    with open('/proc/1/fd/1', 'w') as f:
        f.write(f"{timestamp} - Liveness probe: example.com is reachable\n")
    sys.exit(0)
except Exception as e:
    # Write to container's main process stderr
    with open('/proc/1/fd/2', 'w') as f:
        f.write(

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