feat: randomise startup

[elblivion]

Description

We run multiple Kubernetes clusters in our production AWS account, when a configuration change is made to external-dns simultaneously we see a lot of throttling from the AWS Route53 API.

This mitigates the issue by introducing a randomised wait on startup. This mitigates rather than solves folks' issues with AWS Route63 rate limits, but might alleviate the pain when running multiple external-dns instances in the same account as we do.

Fixes #ISSUE

Checklist

• Unit tests updated
• End user documentation updated

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[elblivion]

/assign @njuettner

[Raffo]

What about providing documentation on how to do this with an init container? It would have the same effect and we wouldn't need to modify the code of the project.

[elblivion]

Hi @Raffo! I updated the change so it's adding to the docs instead.

[Raffo]

/approve
/lgtm

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: elblivion, Raffo

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[dudicoco]

@elblivion what is the benefit of running multiple pods of external-dns?
They would do the exact same job and would probably conflict with each other, or is the use case here is to have a different deployments with different configuration?

[elblivion]

@dudicoco this is not for multiple instances on the same Deployment, rather on multiple clusters in the same AWS account. I see now this isn't clearly explained in the update. :-/

[dudicoco]

@elblivion what is the advantage of running multiple pods in one deployment? I don't think that is best practice per my previous comment.

[johanneswuerbach]

I'm a college of @elblivion and I'll try to explain it in my words 😄 : We are running multiple k8s clusters in the same AWS account, but only one pod per k8s cluster. Nevertheless operations like an external-dns version update will roll all those pods at the same time causing us to hit rate-limit, so this change is mitigating this issue. Does that make sense?