cordon limiter

[dbenque]

Proposition of implementation for #89

The new flags are not mandatory. Behavior of draino is unchanged if new flag are absent. The flags for limits can be repeated and cumulated. See README for details.

[codecov[bot]]

Codecov Report

Merging #90 into master will decrease coverage by 1.41%. The diff coverage is 69.74%.

@@            Coverage Diff             @@
##           master      #90      +/-   ##
==========================================
- Coverage   76.67%   75.25%   -1.42%     
==========================================
  Files           7        8       +1     
  Lines         553      582      +29     
==========================================
+ Hits          424      438      +14     
- Misses        115      119       +4     
- Partials       14       25      +11     

Impacted Files	Coverage Δ
internal/kubernetes/eventhandler.go	61.41% <0.00%> (-6.42%)	:arrow_down:
internal/kubernetes/drainer.go	85.44% <66.66%> (+2.66%)	:arrow_up:
internal/kubernetes/limiter.go	73.26% <73.26%> (ø)
internal/kubernetes/nodefilters.go	91.11% <100.00%> (-1.35%)	:arrow_down:
internal/kubernetes/watch.go	62.50% <100.00%> (+15.83%)	:arrow_up:
internal/kubernetes/util.go	16.66% <0.00%> (-8.34%)	:arrow_down:
internal/kubernetes/drainSchedule.go	67.53% <0.00%> (-1.36%)	:arrow_down:
internal/kubernetes/podfilters.go	100.00% <0.00%> (ø)
... and 3 more

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[dbenque]

@jacobstr FYI, I have used that feature (build from our fork) on our clusters, and we have been able to rotate several thousands of nodes in a really smooth and controlled way.

[jacobstr]

@dbenque pardon the delay looking this over. Had a storm of merges a few weeks ago and haven't given Draino the ❤️ since then. This looks like a worthy contribution and I'm happy to give it a look over and mainline it. Ya'll are probably running a lot of draino forks over at DataDog :)

[dbenque]

@dbenque pardon the delay looking this over. Had a storm of merges a few weeks ago and haven't given Draino the ❤️ since then. This looks like a worthy contribution and I'm happy to give it a look over and mainline it. Ya'll are probably running a lot of draino forks over at DataDog :)

@jacobstr, yes we are, I have couple of contributions that I would like to add to draino. I think it would make sense that we meet (video-call) to discuss a bit about these possible evolutions to check if they fit in our draino roadmap or if I need to think about other ways to achieve some of my goals. If ok, can you ping me on the kubernetes slack @ david.benque ?

[hikhvar]

Any updates on this? We want to deploy draino to our clusters as well. However we are missing some sort of safe-guard like this to prevent false mass drainings.