Readiness Probes

Readiness probes are essential in Kubernetes to ensure that a pod is ready to accept traffic. They help manage the lifecycle of pods by determining when they are ready to serve requests.

POD Status

• Pending: The pod is waiting for resources to be allocated or for scheduling.
• ContainerCreating: The pod is being created, and its containers are being initialized.
• Running: The pod is running and ready to accept traffic.
• Not Ready: The pod is not ready to accept traffic, often due to initialization tasks or configuration issues.
• Failed: The pod has encountered an error and is not functioning correctly.

POD Conditions

• PodScheduled: Indicates whether the pod has been scheduled to a node.
• Initialized: Indicates whether the pod has been initialized.
• ContainersReady: Indicates whether all containers in the pod are ready.
• Ready: Indicates whether the pod is ready to accept traffic.

Readiness Probe

A readiness probe checks if a pod is ready to handle requests. If the probe fails, the pod will not receive traffic until it passes the readiness check again.

apiVersion: v1
kind: Pod
metadata:
  name: readiness-probe-example
spec:
  containers:
  - name: myapp
    image: myapp:latest
    readinessProbe:
      httpGet:
        path: /api/health
        port: 8080
      initialDelaySeconds: 5
      periodSeconds: 10
      failureThreshold: 3

HTTP Get Readiness Probe

readinessProbe:
     httpGet:
        path: /api/health
        port: 8080

TCP Socket Readiness Probe

readinessProbe:
     tcpSocket:
        port: 8080

Exec Readiness Probe

readinessProbe:
     exec:
        command:
        - cat
        - /tmp/healthy

Liveness Probes

Liveness probes are used to determine if a pod is still running. If a liveness probe fails, Kubernetes will restart the pod to restore its functionality.

apiVersion: v1
kind: Pod
metadata:
  name: liveness-probe-example
spec:
  containers:
  - name: myapp
    image: myapp:latest
    livenessProbe:
      httpGet:
        path: /api/health
        port: 8080
      initialDelaySeconds: 5
      periodSeconds: 10
      failureThreshold: 3

HTTP Get Liveness Probe

livenessProbe:
     httpGet:
       path: /api/health
       port: 8080

TCP Socket Liveness Probe

livenessProbe:
     tcpSocket:
       port: 8080

Exec Liveness Probe

livenessProbe:
     exec:
       command:
       - cat
       - /tmp/healthy