Helm chart variable definitions

Question

I am creating an helm chart that should install 2 services. It has a dependency that first postgresql service will be installed. Then the other service should use the database user,password,hostname and port for the postgresql service installed.

Since I need to get these details run time I.e soon installed postgresql service of course user details I will use as env variables, hostname and port to be used once postgresql is deployed.

I tried using some template functions and subchart concepts that I got from different sites.. but nothing is solving the requirement.

Is there any examples that I can get to match the above requirement ?

Answer 1

There are a couple of ways you could do this, for ex. using a InitContainer to check if DB is up, but I will show you with a sample example in the charts. I am using Wordpress Chart as an example

    livenessProbe:
      httpGet:
        path: /wp-login.php
        port: http
      initialDelaySeconds: 120
      timeoutSeconds: 5
      failureThreshold: 6
    readinessProbe:
      httpGet:
        path: /wp-login.php
        port: http
      initialDelaySeconds: 30
      timeoutSeconds: 3
      periodSeconds: 5

I have removed some lines for brevity.

The readiness probe will start acting after a initialDelaySeconds of 30 seconds, will check every periodSeconds i.e. 5 seconds to see if the page responds. Unless the readiness probe succeeds, the traffic won't be sent to this pod. If the probe succeeds then we are good.

The second check - liveness probe does something more. It is starting 120 seconds after the pod is deployed. But if the check fails, it will restart the pod and it will restart failureThreshold times i.e. 6 times.

Coming back to your question and how to solve this:

• Use liveness and readiness probes in the applications which are dependent on the database
• Use some defaults based on your experience and optimize them as you go.

More information about the readiness and liveness probes can be found here