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Handle context in the process loop #132005

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kei01234kei
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What type of PR is this?

/kind cleanup

What this PR does / why we need it:

To address the TODO comment.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

NONE

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

@k8s-ci-robot k8s-ci-robot added release-note-none Denotes a PR that doesn't merit a release note. size/S Denotes a PR that changes 10-29 lines, ignoring generated files. kind/cleanup Categorizes issue or PR as related to cleaning up code, process, or technical debt. cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. do-not-merge/needs-sig Indicates an issue or PR lacks a `sig/foo` label and requires one. needs-triage Indicates an issue or PR lacks a `triage/foo` label and requires one. needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. needs-priority Indicates a PR lacks a `priority/foo` label and requires one. labels May 28, 2025
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Hi @kei01234kei. 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.

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@k8s-ci-robot k8s-ci-robot requested review from dims and mikedanese May 28, 2025 15:37
@k8s-ci-robot k8s-ci-robot added sig/api-machinery Categorizes an issue or PR as relevant to SIG API Machinery. and removed do-not-merge/needs-sig Indicates an issue or PR lacks a `sig/foo` label and requires one. labels May 28, 2025
@kei01234kei kei01234kei changed the title handle context in process loop Handle context in the process loop May 28, 2025
BenTheElder
BenTheElder reviewed Jun 3, 2025
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staging/src/k8s.io/client-go/tools/cache/controller.go Outdated
case <-ctx.Done():
return
default:
_, err := c.config.Queue.Pop(PopProcessFunc(c.config.Process))
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can this block indefinitely?

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The Pop method can block indefinitely for some reason, but it is clear that this is not intentional, considering that the method acquires a lock for its entire execution.

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If Pop can block indefinitely, then adding context here won't actually be respected?

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It would also need to accept context, or have some timeout or ...

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If Pop can block indefinitely, then adding context here won't actually be respected?

I read the code carefully again, and I realized that Pop does not block indefinitely.
Pop is blocked when Wait is called here.

kubernetes/staging/src/k8s.io/client-go/tools/cache/delta_fifo.go

Lines 497 to 506 in 00d3750

for len(f.queue) == 0 {
// When the queue is empty, invocation of Pop() is blocked until new item is enqueued.
// When Close() is called, the f.closed is set and the condition is broadcasted.
// Which causes this loop to continue and return from the Pop().
if f.closed {
return nil, ErrFIFOClosed
}
f.cond.Wait()
}

However, when the ctx is done, Close is called, which then calls Broadcast here.

kubernetes/staging/src/k8s.io/client-go/tools/cache/controller.go

Lines 150 to 153 in 00d3750

go func() {
<-ctx.Done()
c.config.Queue.Close()
}()

This means Pop can return.
That's why Pop does not block indefinitely.

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/triage accpeted

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@BenTheElder: The label(s) triage/accpeted cannot be applied, because the repository doesn't have them.

In response to this:

/triage accpeted

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.

@kei01234kei kei01234kei requested a review from BenTheElder June 6, 2025 05:01
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(@BenTheElder, Triage is not accepted yet.)

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(@BenTheElder, Triage is not accepted yet.)

ah, fwiw this just removes it from the triage queue, it doesn't impact merging etc
/triage accepted

@k8s-ci-robot k8s-ci-robot added triage/accepted Indicates an issue or PR is ready to be actively worked on. size/L Denotes a PR that changes 100-499 lines, ignoring generated files. and removed needs-triage Indicates an issue or PR lacks a `triage/foo` label and requires one. size/S Denotes a PR that changes 10-29 lines, ignoring generated files. labels Jun 10, 2025
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/ok-to-test

@k8s-ci-robot k8s-ci-robot added ok-to-test Indicates a non-member PR verified by an org member that is safe to test. sig/scheduling Categorizes an issue or PR as relevant to SIG Scheduling. and removed needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. labels Jun 15, 2025
@kei01234kei kei01234kei force-pushed the handle_context_in_processloop branch from 67faafa to 2cd5dbb Compare June 15, 2025 06:50
@kei01234kei
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@BenTheElder
I would be grateful if you could review this pr when you have time.

@googs1025
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hi! Can you get ci through first? 😄

@k8s-ci-robot k8s-ci-robot added size/S Denotes a PR that changes 10-29 lines, ignoring generated files. and removed size/L Denotes a PR that changes 100-499 lines, ignoring generated files. labels Jun 26, 2025
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[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: kei01234kei
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@dims dims Awaiting requested review from dims

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