DevOps: What is Kubernetes Pod Lifecycle Readiness Probe?

1apiVersion: apps/v1
2kind: Deployment
3metadata:
4  name: myapp
5spec:
6  replicas: 3
7  template:
8    spec:
9      containers:
10      - name: app
11        image: myapp:latest
12        readinessProbe:
13          httpGet:
14            path: /ready
15            port: 8080
16            httpHeaders:
17            - name: X-Readiness
18              value: "check"
19          initialDelaySeconds: 5
20          periodSeconds: 10
21          timeoutSeconds: 3
22          successThreshold: 1
23          failureThreshold: 3
24---
25# TCP readiness probe
26apiVersion: apps/v1
27kind: Deployment
28metadata:
29  name: myapp-tcp
30spec:
31  template:
32    spec:
33      containers:
34      - name: app
35        image: myapp:latest
36        readinessProbe:
37          tcpSocket:
38            port: 8080
39          initialDelaySeconds: 5
40          periodSeconds: 10
41---
42# Exec readiness probe
43apiVersion: apps/v1
44kind: Deployment
45metadata:
46  name: myapp-exec
47spec:
48  template:
49    spec:
50      containers:
51      - name: app
52        image: myapp:latest
53        readinessProbe:
54          exec:
55            command:
56            - sh
57            - -c
58            - "curl -f http://localhost:8080/ready || exit 1"
59          initialDelaySeconds: 5
60          periodSeconds: 10

1# Check readiness probe
2kubectl describe pod my-pod | grep -A 10 "readinessProbe"
3
4# Check Pod ready condition
5kubectl get pod my-pod -o jsonpath='{.status.conditions[?(@.type=="Ready")].status}'
6
7# Check endpoint inclusion
8kubectl get endpoints myapp
9
10# Verify readiness
11kubectl get pods -o wide | grep myapp
12
13# Check probe logs
14kubectl logs my-pod --previous
15
16# Verify readiness endpoint
17kubectl exec my-pod -- curl -s http://localhost:8080/ready