helm: support initContainers

[calvinbui]

Description

Support initContainers on Helm chart

Fixes #3830

Checklist

• Unit tests updated
• End user documentation updated

[k8s-ci-robot]

Welcome @calvinbui!

It looks like this is your first PR to kubernetes-sigs/external-dns 🎉. Please refer to our pull request process documentation to help your PR have a smooth ride to approval.

You will be prompted by a bot to use commands during the review process. Do not be afraid to follow the prompts! It is okay to experiment. Here is the bot commands documentation.

You can also check if kubernetes-sigs/external-dns has its own contribution guidelines.

You may want to refer to our testing guide if you run into trouble with your tests not passing.

If you are having difficulty getting your pull request seen, please follow the recommended escalation practices. Also, for tips and tricks in the contribution process you may want to read the Kubernetes contributor cheat sheet. We want to make sure your contribution gets all the attention it needs!

Thank you, and welcome to Kubernetes. 😃

[k8s-ci-robot]

Hi @calvinbui. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[mloiseleur]

Thanks for this PR.
At first, I was thinking about asking to add tests but ... there is no tests in external-dns chart FTM.

[stevehipwell]

@calvinbui thanks for the PR, could you update the README to add the new initContainers value? Also have you tested this locally?

[calvinbui]

@calvinbui thanks for the PR, could you update the README to add the new initContainers value? Also have you tested this locally?

Forgot about that! Added.

Yes, I have tested templating with the initContainers value.

[mloiseleur]

Suggested change

	{{- toYaml . | nindent 8 }}
	{{- tpl (toYaml .) . | nindent 8 }}

By using tpl, it will allow to use {{ include "external-dns.image" . }} in the values

[calvinbui]

i've never seen any templating possible through values?

it doesn't work for me:

initContainers:
  - name: init-jitter
    image: {{ include "external-dns.image" . }}
    command:
      - /bin/sh
      - -c
      - 'FOR=$((RANDOM % 10))s;echo "Sleeping for $FOR";sleep $FOR'

Error: cannot load values.yaml: error converting YAML to JSON: yaml: invalid map key: map[interface {}]interface {}{"include \"external-dns.image\" .":interface {}(nil)}

[stevehipwell]

@mloiseleur that would be incorrect, tpl shouldn't be used like this. If you want tpl support you'd need to support init containers as either a string or an array and only template when it's been provided as a string. I'd prefer this to stay as it is.

[mloiseleur]

@calvinbui It has been done on Traefik Helm Chart, see this PR for instance.
@stevehipwell I understand. It's ok for me.

[stevehipwell]

@mloiseleur this is a well known anti-pattern that looks like it should work, works in very simple scenarios but fails hard for anything more complex. To prove this attempt to use the selector labels template for traefik affinity match labels and you will see what I mean.

[mloiseleur]

Yes, you're right.

[stevehipwell]

/ok-to-test

[mloiseleur]

@calvinbui The CI has been fixed with #3829. If you rebase this PR, CI should be able to pass as expected.

[mloiseleur]

/test pull-external-dns-lint

[stevehipwell]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: calvinbui, mloiseleur, stevehipwell

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• charts/OWNERS [stevehipwell]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[mloiseleur]

/lgtm