Serialize creation of Pods in a deployment manifest using Helm charts

Question

So I have a helm chart that deploys a pod, so the next task is to create another pod once the first pod is running.

So I created a simple pod.yaml in chart/templates which creates a simple pod-b, so next step to only create pod-b after pod-a is running.

So was only at helm hooks but don't think they care about pod status.

Another idea is to use Init container like below but not sure how to write command to lookup a pod is running?

spec:
  containers:
  - name: myapp-container
    image: busybox
    command: ['sh', '-c', 'echo The app is running! && sleep 3600']
  initContainers:
  - name: init-myservice
    image: busybox
    command: ['sh', '-c', 'until nslookup myservice; do echo waiting for myservice; sleep 2; done;']

Another idea is a simple script to check pod status something like:

y=`kubectl get po -l app=am -o 'jsonpath={.items[0].status.phase}'`
   while [ $i -le 5 ]
   do
    if [[ "$y" == "Running" ]]; then
      break
    fi
    sleep 5
   done

Any advice would be great.

Answer 1

If you want your post-install/post-upgrade chart hooks to work, you should add readiness probes to your first pod and use --wait flag.

helm upgrade --install -n test --wait mychart .

pod.yaml

apiVersion: v1
kind: Pod
metadata:
  name: readiness-exec
  labels:
    test: readiness
spec:
  containers:
  - name: readiness
    image: k8s.gcr.io/busybox
    args:
    - /bin/sh
    - -c
    - sleep 30; touch /tmp/healthy; sleep 600
    readinessProbe:
      exec:
        command:
        - cat
        - /tmp/healthy
      initialDelaySeconds: 10
      periodSeconds: 5
      failureThreshold: 10

hook.yaml

apiVersion: batch/v1
kind: Job
metadata:
  name: "post-deploy"
  annotations:
    "helm.sh/hook": post-upgrade,post-install
    "helm.sh/hook-delete-policy": before-hook-creation
spec:
  backoffLimit: 1
  template:
    metadata:
      name: "post-deploy"
    spec:
      restartPolicy: Never
      containers:
        - name: post-deploy
          image: k8s.gcr.io/busybox
          args:
          - /bin/sh
          - -c
          - echo "executed only after previous pod is ready"