Serialize creation of Pods in a deployment manifest using Helm charts - kubernetes

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"