Issue 4230: remove readiness check for cache exclusion

[alexanderConstantinescu]

What type of PR is this?

/kind bug

What this PR does / why we need it:

Issue #4230 explains things in greater depth, but here's the TL;DR

kubernetes/kubernetes#109706 stopped syncing load balancers when changes are observed to the readiness state of the Node object. Load balancers are essentially almost only re-synced whenever a Node is: added, deleted, has the exclusion label added. The service controller expectation is that the cloud-providers just accept the list of nodes provided through the UpdateLoadBalancerHost call and try to configure the load balancers with the entire set of nodes provided. Given that Azure performs additional filtering of the nodes and excludes NotReady nodes, there will be situations where the node which just transitioned to Ready isn't added to the load balancer node set, because the service controller doesn't re-sync load balancers due to the readiness state change.

This patch removes this additional filtering of the readiness state so that all NotReady nodes get added to the load balancer set. The health check probes used by the load balancer will then determine which nodes should be used for traffic load balancing.

Please have a look at the referenced enhancement proposal which merged in 1.26: kubernetes/enhancements#3458

/cc @JoelSpeed

Which issue(s) this PR fixes:

Fixes #4230

Special notes for your reviewer:

Does this PR introduce a user-facing change?

Fixes issue 4230 and removes the additional filtering on `NotReady` nodes by the azure cloud provider code 

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

https://github.com/kubernetes/enhancements/issues/3458

[k8s-ci-robot]

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[k8s-ci-robot]

Hi @alexanderConstantinescu. Thanks for your PR.

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[alexanderConstantinescu]

This will need back-ports to release-1.26 and release-1.27

[feiskyer]

Thanks for the PR!
/ok-to-test

[alexanderConstantinescu]

@feiskyer what's the back-port process for AKS? I guess I need to file a PR to master in https://github.com/kubernetes/kubernetes/tree/master/staging/src/k8s.io/legacy-cloud-providers/azure ? And then back-port that to release-1.26 / release-1.27? Or is everything done in this repo?

[JoelSpeed]

Changes LGTM based on my understanding of the code and changes reported in the linked issue
/lgtm

[alexanderConstantinescu]

@feiskyer : could you please have a look at this quite soon? AKS has released several versions of 1.26 with this bug, and it's a pretty important one since it's really easy to trigger and and cause a complete downtime for any ETP:Local services on the cluster

[feiskyer]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: alexanderConstantinescu, feiskyer

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[feiskyer]

/cherry-pick release-1.26

[k8s-infra-cherrypick-robot]

@feiskyer: once the present PR merges, I will cherry-pick it on top of release-1.26 in a new PR and assign it to you.

In response to this:

/cherry-pick release-1.26

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[feiskyer]

/cherry-pick release-1.27

[k8s-infra-cherrypick-robot]

@feiskyer: once the present PR merges, I will cherry-pick it on top of release-1.27 in a new PR and assign it to you.

In response to this:

/cherry-pick release-1.27

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[k8s-ci-robot]

New changes are detected. LGTM label has been removed.

[feiskyer]

Rebased due to conflicts and added lgtm label back.

[feiskyer]

/test pull-cloud-provider-azure-e2e-ccm-capz

[k8s-infra-cherrypick-robot]

@feiskyer: #4234 failed to apply on top of branch "release-1.26":

Applying: Issue 4230: remove readiness check for cache exclusion
Using index info to reconstruct a base tree...
M	pkg/provider/azure.go
M	pkg/provider/azure_test.go
Falling back to patching base and 3-way merge...
Auto-merging pkg/provider/azure_test.go
Auto-merging pkg/provider/azure.go
CONFLICT (content): Merge conflict in pkg/provider/azure.go
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
Patch failed at 0001 Issue 4230: remove readiness check for cache exclusion
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

In response to this:

/cherry-pick release-1.26

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[k8s-infra-cherrypick-robot]

@feiskyer: #4234 failed to apply on top of branch "release-1.27":

Applying: Issue 4230: remove readiness check for cache exclusion
Using index info to reconstruct a base tree...
M	pkg/provider/azure.go
M	pkg/provider/azure_test.go
Falling back to patching base and 3-way merge...
Auto-merging pkg/provider/azure_test.go
Auto-merging pkg/provider/azure.go
CONFLICT (content): Merge conflict in pkg/provider/azure.go
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
Patch failed at 0001 Issue 4230: remove readiness check for cache exclusion
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

In response to this:

/cherry-pick release-1.27

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[aaron-trout]

Hi @feiskyer, are you able to confirm which AKS releases this has/will make it's way into? I see there was one 18 hours ago: https://github.com/Azure/AKS/releases/tag/2023-07-30

Thanks!