health.md

Health Checks

Exercise 1: Deploy a pod with a health check

1. Create a pod that exposes an endpoint /health, responding with an HTTP 200 status code

   Save the following file as hc.yaml

   cat > hc.yaml <<EOF
   apiVersion: v1
   kind: Pod
   metadata:
     name: hc
   spec:
     containers:
     - name: simpleservice
       image: mhausenblas/simpleservice:0.5.0
       ports:
       - containerPort: 9876
       livenessProbe:
         initialDelaySeconds: 2
         periodSeconds: 5
         httpGet:
           path: /health
           port: 9876
   EOF  
   

   Pay attention to livenessProbe section.

2. Deploy the pod

   kubectl create -f hc.yaml
   

3. Describe the pod; it should be considered healthy

   kubectl describe pod hc
   

4. Now we launch a bad pod, that is, a pod that has a container that randomly (in the time range 1 to 4 sec) does not return a 200 code Save the following file as bad-hc.yaml

   cat > bad-hc.yaml <<EOF
   apiVersion: v1
   kind: Pod
   metadata:
     name: bad-hc
   spec:
     containers:
     - name: simpleservice
       image: mhausenblas/simpleservice:0.5.0
       ports:
       - containerPort: 9876
       env:
       - name: HEALTH_MIN
         value: "1000"
       - name: HEALTH_MAX
         value: "4000"
       livenessProbe:
         initialDelaySeconds: 2
         periodSeconds: 5
         httpGet:
           path: /health
           port: 9876
   EOF
   

5. Deploy the pod

   kubectl create -f bad-hc.yaml
   

6. Check events at the bad pod

   kubectl describe pod bad-hc
   

   You should see that bad pod was restarted several times.

7. Delete the pods

   kubectl delete pod hc bad-hc
   

Exercise 2: Use readiness probe

1. Create a pod readiness.yaml with a readinessProbe that kicks in after 10 seconds

   cat > readiness.yaml <<EOF
   apiVersion: v1
   kind: Pod
   metadata:
     name: readiness
   spec:
     containers:
     - name: simpleservice
       image: mhausenblas/simpleservice:0.5.0
       ports:
       - containerPort: 9876
       readinessProbe:
         initialDelaySeconds: 10
         httpGet:
           path: /health
           port: 9876
   EOF
   

2. Deploy the pod

   kubectl create -f readiness.yaml
   

3. Looking at the events of the pod. You should see that, eventually, the pod is ready to serve traffic

   kubectl describe pod readiness
   

4. Delete the pod

   kubectl delete pod readiness
   

Exercise 3 (Optional): Create health check for nginx pod

1. Deploy a pod that runs nginx and uses port 80 and root path for the health check. Ensure that pod is healthy.
2. Change health check configuration to make pod unhealthy.
3. Observe whether kubernetes tries to restart the unhealthy pod.

Exercise 4 (Optional): Create health check using TCP sockets

1. Modify hc.yaml to use a TCP socket handler instead of HTTP GET handler. Reference link
2. Deploy the pod and see if the pod is considered healthy.

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Next: Deployments