Kubernetes Readiness

Readiness

Method

If readiness is not ready, it will remove endpoint of pod, so the network is not reachable even it register to DNS. if readiness is ready, it will enable the endpoint of pod, so the network is reachable.

Readiness Setting

       image: 192.168.51.130:5000/uwebserverv6


        readinessProbe:
          tcpSocket:
            port: 8000
          initialDelaySeconds: 60
          periodSeconds: 5

where initialDelaySeonds is delay time to probe the readiness, and after initial Delay, it will start to delete port 8000.

NAME                          READY     STATUS    RESTARTS   AGE
dep-c-2945203518-dcjjm        0/1       Running   0          1m

To see endpoint, not yet setting

root@kubecontext:~/k8sdeployex/dependency/test2# kubectl get ep
NAME          ENDPOINTS                             AGE
dep-c                                               1m

Although you see the dep-c's status is running, but in actually the networking is not reachable.

Do not use nslookup since the name has been register to Sky-DNS. So if you just use nslookup dep-c, it will be connected.

After Readiness is ready.

root@kubecontext:~/k8sdeployex/dependency/test2# kubectl get po
NAME                          READY     STATUS    RESTARTS   AGE
dep-c-3125362030-4tnjk        1/1       Running   0          1m

root@kubecontext:~/k8sdeployex/dependency/test2# kubectl get ep
NAME          ENDPOINTS                             AGE
dep-c         192.168.15.6:8000                     1m

Mention that

1. initialDelaySeconds is delay time for probe. We set 60 is for after container launched 60secs, we then start to probe. Why is 60 secs, since we assume that the container will load data and is about 60 secs.
2. Do not use nslookup, since the DNS has registry the IP root@kubecontext:~/k8sdeployex/dependency# kubectl get svc NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE dep-c 172.18.254.42 <none> 8000/TCP 1m So you will see nslookup detect is true, but the readiness is not ready.

initContainer Setting

      initContainers:
      - name: init-myservice
        image: 192.168.51.130:5000/emotibot-k8s/busybox:latest
        command: ['sh', '-c', 'until nc -v -z -w 1 dep-c 8000 ; do echo waiting for myservice; sleep 2; done;']
        #command: ['sh', '-c', 'until nslookup dep-c ; do echo waiting for myservice; sleep 2; done;']

Do not use nslookup, since DNS is registry. use nc to detect domain name and port is better.