fix: Force Lease Expiration When Leader Exits

[RaghavRoy145]

What type of PR is this?

/kind bug

What this PR does / why we need it:

Currently, when the leader exits (say, after receiving a SIGINT) the workers need to wait for its lease to expire before a leader is re-elected. This patch mimics the behaviour of the Go Client implementation of using ctx.Done(): https://github.com/kubernetes/client-go/blob/1309f64d6648411b4a36a2f7fa84dd8df31884b6/tools/leaderelection/leaderelection.go#L265-L291. It captures the SIGINT and forces the lease to exit by setting the expiration to a date in the past, and it also sets the acquire_time to None to force a leader election.

• Issue Reproduction

  As mentioned in the issue: leaderelection do not stop leading properly #2075, to reproduce this issue you can follow leaderelection/example.py. Run it on 2-3 nodes (or tmux screens) and once a leader is elected hit Ctrl+C to force the leader to exit. The workers then wait for the leader's lease to expire before a new leader is elected.

• Expected behavior

  The leader exiting should trigger a leader election without having the workers wait for the lease to expire.

Which issue(s) this PR fixes:

Fixes #2075

Special notes for your reviewer:

This is still not a complete fix. It is definitely hacky at the moment and I would love any guidance here! Currently, the patch only handles SIGINT but a leader may exit for various reasons, and there should be a more elegant way of handling this. Probably using the thread context but I was not able to figure that out. Further, the implementation of the force_expire_lease() function is not elegant; you shouldn't need to set acquire_time to None and setting expiration to the past is also a code smell in my opinion. This patch is a proof of concept because of this.

I also had to change the imports to point to my definitions of electionconfig.py and leaderelectionrecord.py for this to work and I'm sure there is a better way of handling this.

If its more sensible to mark this PR a draft, I'm happy to do so!

Does this PR introduce a user-facing change?

None

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

None

[k8s-ci-robot]

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[RaghavRoy145]

/assign @yliaog

[RaghavRoy145]

/assign @yliaog

Oops, I was supposed to do that after the reviews 🙃