[WIP] Change hashing algorithm in Deployments

[0xmichalis]

Superseded by #44774

[k8s-reviewable]

This change is 

[0xmichalis]

@wojtek-t I want to write a test that spins up a cluster, creates X namespaces, creates Y deployments in each namespace, runs Z rollouts for each deployment, restart the controller manager with --deployment-hashing-algorithm=migrates-to-fnv, kick new rolllouts for all the existing deployments, and verify in the end that all replica sets have migrated. Any ideas where such a test should live?

X (average # of namespaces per cluster)
Y (average # of deployments per namespace)
Z (can be 2, can be 200)

[0xmichalis]

@smarterclayton where do we expose metrics for the controller manager? I can't seem to find those under the master /metrics endpoint.

[bgrant0607]

cc @janetkuo

[smarterclayton]

No idea - scheduler has it, and I thought it was enabled for controller manager because someone was looking at queue depths a while back.

[janetkuo]

where do we expose metrics for the controller manager?

Is this what you're looking for?
https://github.com/kubernetes/kubernetes/blob/master/pkg/metrics/metrics_grabber.go#L122

func (g *MetricsGrabber) GrabFromControllerManager() (ControllerManagerMetrics, error) {
	if !g.registeredMaster {
		return ControllerManagerMetrics{}, fmt.Errorf("Master's Kubelet is not registered. Skipping ControllerManager's metrics gathering.")
	}
	output, err := g.getMetricsFromPod(fmt.Sprintf("%v-%v", "kube-controller-manager", g.masterName), api.NamespaceSystem, ports.ControllerManagerPort)
	if err != nil {
		return ControllerManagerMetrics{}, err
	}
	return parseControllerManagerMetrics(output)
}

[0xmichalis]

@janetkuo the library you are linking is assuming we are running a self-hosted cluster (components run inside pods). I can't see us using it anywhere in the Kubernetes repository apart from some e2e tests.

[janetkuo]

@Kargakis FYI the controller manager metrics handler is here

[0xmichalis]

@janetkuo thanks for the pointer.

Note that if the update on the Deployment proposal that I have up for review is accepted (kubernetes/community#384), then we may not need to migrate old replica sets.

[k8s-github-robot]

@Kargakis PR needs rebase

[0xmichalis]

A migration won't be needed. Closing this one