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apiserver: fix data race on request body with timeout #117164

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apiserver: fix data race on request body with timeout #117164

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tkashem
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@tkashem tkashem commented Apr 7, 2023

What type of PR is this?

/kind bug

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #117052

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.:

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[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: tkashem
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@k8s-ci-robot k8s-ci-robot requested review from dims and sttts April 7, 2023 18:31
@k8s-ci-robot k8s-ci-robot added area/apiserver sig/api-machinery Categorizes an issue or PR as relevant to SIG API Machinery. 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-priority Indicates a PR lacks a `priority/foo` label and requires one. and removed do-not-merge/needs-sig Indicates an issue or PR lacks a `sig/foo` label and requires one. labels Apr 7, 2023
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tkashem commented Apr 7, 2023

proof of concept, to support #117111, please feel free to use it if you find it reasonable.

/cc @pohly @aojea

@k8s-ci-robot k8s-ci-robot requested review from aojea and pohly April 7, 2023 18:36
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pohly commented Apr 7, 2023

That looks like the code that I wrote, I also had such a timeout reader.

Can you explain more in your PR how it's different from what I proposed and why it should get merged? I just says "fixes 117052" without saying much about how it fixes that problem?

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aojea commented Apr 8, 2023

I was expecting we could use the new 1.20 golang functionality to implement per handlers timeouts and get rid of the groutine hack :/

pohly
pohly reviewed Apr 10, 2023
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staging/src/k8s.io/apiserver/pkg/server/filters/timeout.go
if tr.timedOut {
return 0, http.ErrHandlerTimeout
}
return tr.ReadCloser.Read(b)
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Suppose Read blocks because it is waiting for the HTTP client to send the body. Then the lock is held and timeout() in timeoutHandler.ServeHTTP blocks, preventing the timeout handling.

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@tkashem tkashem Apr 10, 2023 •
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yes, this could happen. I think we already have this today for the ResponseWriter

kubernetes/staging/src/k8s.io/apiserver/pkg/server/filters/timeout.go

Line 149 in ad18954

tw.timeout(err)

ioutil.ReadAll reads 512 bytes at a time, so the the Read calls will probably be intermingled between the two goroutinesin in this situation:

  • goroutine B does a Read and reads some bytes from the Request Body (before timeout)
  • request times out
  • timeout handler marks the body reader as timed out
  • goroutine A or B calls Read and gets ErrHandlerTimeout

I don't think we need to prevent Read calls getting intermingled, the request has timed out and we are sending a 504 to the caller.

but if a Read or Write call blocks from goroutine B it will freeze the timeout handler and prevent it from sending a panic or 504 indefinitely.

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tkashem commented Apr 10, 2023 •
edited

I was expecting we could use the new 1.20 golang functionality to implement per handlers timeouts and get rid of the groutine hack :/

@aojea #114189 will pave the way for go 1.20 per handler timeout, I need to resolve the test failures. As far as when we should remove the tiemeout filter, i put some thoughts here: #117111 (comment)

This PR (or #117111) is a short-term band aid if we want to run the integration test suite race enabled now.

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cici37 commented Apr 11, 2023

/triage accepted

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pohly commented Jan 19, 2024

/remove lifecycle/rotten

@tkashem : are you still working on this?

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pohly commented Jan 19, 2024

/remove-lifecycle rotten

@k8s-ci-robot k8s-ci-robot removed the lifecycle/rotten Denotes an issue or PR that has aged beyond stale and will be auto-closed. label Jan 19, 2024
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The Kubernetes project currently lacks enough contributors to adequately respond to all PRs.

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/lifecycle stale

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pohly commented Apr 19, 2024

/remove-lifecycle rotten

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/lifecycle rotten

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apiserver: data race
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