How to run command after initialization - kubernetes

Question

I would like to run specific command after initialization of deployment is successful.
This is my yaml file:
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: auth
spec:
replicas: 1
template:
metadata:
labels:
app: auth
spec:
containers:
- name: auth
image: {{my-service-image}}
env:
- name: NODE_ENV
value: "docker-dev"
resources:
requests:
cpu: 100m
memory: 100Mi
ports:
- containerPort: 3000
However, I would like to run command for db migration after (not before) deployment is successfully initialized and pods are running.
I can do it manually for every pod (with kubectl exec), but this is not very scalable.

Answer 1

I resolved it using lifecycles:
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: auth
spec:
replicas: 1
template:
metadata:
labels:
app: auth
spec:
containers:
- name: auth
image: {{my-service-image}}
env:
- name: NODE_ENV
value: "docker-dev"
resources:
requests:
cpu: 100m
memory: 100Mi
ports:
- containerPort: 3000
lifecycle:
postStart:
exec:
command: ["/bin/sh", "-c", {{cmd}}]

Answer 2

You can use Helm to deploy a set of Kubernetes resources. And then, use a Helm hook, e.g. post-install or post-upgrade, to run a Job in a separate docker container. Set your Job to invoke db migration. A Job will run >=1 Pods to completion, so it fits here quite well.

Answer 3

I chose to use a readinessProbe
My application requires configuration after the process has completely started.
The postStart command was running before the app was ready.
readinessProbe:
exec:
command: [healthcheck]
initialDelaySeconds: 30
periodSeconds: 2
timeoutSeconds: 1
successThreshold: 3
failureThreshold: 10