Fix route-controller by fanning out getInstancesByIDs through the batcher

[babyhuey]

What type of PR is this?

/kind bug

What this PR does / why we need it:

describeInstanceBatcher.DescribeInstances requires an input with exactly one instance ID:

https://github.com/kubernetes/cloud-provider-aws/blob/master/pkg/providers/v1/describe_instance_batch.go#L56-L58

The batcher's BatchExecutor is what aggregates concurrent single-instance inputs back into one DescribeInstances API call. But getInstancesByIDs was passing the full slice of instance IDs as a single input, which trips that guard and errors out any time more than one instance is looked up.

The most visible consequence is that in clusters using kubenet / route-based pod networking, the route-controller's initial ListRoutes call always needs to look up every node and therefore always fails with expected to receive a single instance only, found N. No pod-CIDR VPC routes get created and source-dest-check is left enabled on new workers, so pods on new nodes have no connectivity — see #1351.

This PR fans out one goroutine per instance ID, each passing a single-instance input into the batcher. The batcher then coalesces those concurrent calls into one underlying DescribeInstances API call, preserving the original batching behavior while honoring the single-instance contract.

Which issue(s) this PR fixes:

Fixes #1351

Special notes for your reviewer:

• go build ./... clean
• go test ./pkg/providers/v1/... passes
• The only other caller of getInstancesByIDs (aws.go:3412) already passes a single-ID slice, so its behavior is unchanged.

Does this PR introduce a user-facing change?

Fix route-controller and other code paths that resolve multiple instances in one call. `getInstancesByIDs` previously passed the full slice into `describeInstanceBatcher.DescribeInstances`, which rejects inputs with more than one ID, breaking the route-controller in kubenet/route-based clusters.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: babyhuey / name: Hannah Lyons (7e2c805)

[k8s-ci-robot]

This issue is currently awaiting triage.

If cloud-provider-aws contributors determine this is a relevant issue, they will accept it by applying the triage/accepted label and provide further guidance.

The triage/accepted label can be added by org members by writing /triage accepted in a comment.

Details

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-sigs/prow repository.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please assign kmala for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[k8s-ci-robot]

Welcome @babyhuey!

It looks like this is your first PR to kubernetes/cloud-provider-aws 🎉. Please refer to our pull request process documentation to help your PR have a smooth ride to approval.

You will be prompted by a bot to use commands during the review process. Do not be afraid to follow the prompts! It is okay to experiment. Here is the bot commands documentation.

You can also check if kubernetes/cloud-provider-aws has its own contribution guidelines.

You may want to refer to our testing guide if you run into trouble with your tests not passing.

If you are having difficulty getting your pull request seen, please follow the recommended escalation practices. Also, for tips and tricks in the contribution process you may want to read the Kubernetes contributor cheat sheet. We want to make sure your contribution gets all the attention it needs!

Thank you, and welcome to Kubernetes. 😃

[k8s-ci-robot]

Hi @babyhuey. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work.

Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Details

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-sigs/prow repository.

[babyhuey]

/check-cla

[kmala]

I think we should add the functionality in the batcher instead of the client making complex logic

[babyhuey]

Thanks @kmala, that makes sense. I moved the fan out into describeInstanceBatcher.DescribeInstances itself in the latest push, so multi ID inputs are split into one batcher.Add per ID inside the batcher and the caller in getInstancesByIDs is back to the simple single call. Added a regression test (TestDescribeInstanceBatchingWithMultipleInstanceIDs) covering the multi ID path. Local go test ./pkg/providers/v1/..., gofmt, golint, and vet all pass.

[hakman]

/ok-to-test