Add leader election to tide

[stpabhi]

fixes #16153

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[alvaroaleman]

@stpabhi Did you mean to close the PR?

[stpabhi]

@alvaroaleman yes. My bad that I didn’t read the comment that says mgr is not used to control the lifecycle. I believe whatever changes I requested might be no-op. Also, is there any reason for doing that? I haven’t looked at the code in detail yet. Any pointers?

[alvaroaleman]

So the reason why we don't use the Manager for the binaries lifecycle is that it doesn't support graceful termination (xref kubernetes-sigs/controller-runtime#764). This is why we currently have the interrupts package even though it solves a problem that is not specific to this project in any way.

Now that I think about it though, we could probably:

• Continue to use interrupt to manage the binaries lifecycle
• Build a wrapper for the tide controllers that implements manager.Runnable (This is needed so the Manager can control their lifecycle)
• Have that wrapper finish an active sync but not start a new one once its stop channel is closed
• Somehow tell interrupts that it has to wait (maybe we can add the controllers to both the manager and interrupts?)

Strictly speaking that means that there is a short period in which two tide instances could do work since we basically ignore the lost leader lease during shutdown and finish our current work anyways, but that is certainly better than no leader election at all.

WDYT?

[stpabhi]

Thanks for the input. I will take a look at the references and interrupts pkg to understand it.