dependencies - Helm wait till dependency deployment are ready on kubernetes

Question

I'm using helm chart to deploy my application on kubernetes. But services that I'm using in my stack depends on other services how do I make sure helm will not deploy until the dependencies are up?

Answer 1

Typically you don't; you just let Helm (or kubectl apply -f) start everything in one shot and let it retry starting everything.

The most common pattern is for a container process to simply crash at startup if an external service isn't available; the Kubernetes Pod mechanism will restart the container when this happens. If the dependency never comes up you'll be stuck in CrashLoopBackOff state forever, but if it appears in 5-10 seconds then everything will come up normally within a minute or two.

Also remember that pods of any sort are fairly disposable in Kubernetes. IME if something isn't working in a service one of the first things to try is kubectl delete pod and letting a Deployment controller recreate it. Kubernetes can do this on its own too, for example if it decides it needs to relocate a pod on to a different node. That is: even if some dependency is up when your pod first start sup, there's no guarantee it will stay up forever.