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Add optional websocket keepalive pings for idle Exec sessions#2878

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copilot/exec-timeout-fix
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Add optional websocket keepalive pings for idle Exec sessions#2878
Copilot wants to merge 5 commits into
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copilot/exec-timeout-fix

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Copilot AI commented May 26, 2026 •
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Exec websocket sessions can be dropped around the 5-minute mark in some proxy/network paths when no traffic is sent. This change adds an opt-in keepalive mechanism for Exec without changing default behavior.

  • API: opt-in exec keepalive

    • Added ExecOptions with pingIntervalMs?: number.
    • Extended Exec.exec(...) with an optional trailing options parameter.

  • Behavior: ping/pong-aware websocket keepalive

    • When pingIntervalMs is a positive integer, Exec sends websocket ping frames while the socket is open.
    • Keepalive tracks pong responses and allows only one outstanding ping at a time (next ping is sent after pong is handled).
    • Keepalive is ignored when the underlying socket does not expose ping().

  • Lifecycle: cleanup on termination

    • Keepalive timer is cleared on websocket close and error to avoid orphaned intervals.
    • Pong listener is removed during cleanup.

  • Coverage: focused unit test

    • Added a targeted exec_test case validating that pings are emitted when configured, pong handling enables subsequent pings, and pings stop after close.
const exec = new Exec(kc);

await exec.exec(
  'ns',
  'pod',
  'container',
  ['sh', '-c', 'long-running-command'],
  stdout,
  stderr,
  stdin,
  false,
  undefined,
  { pingIntervalMs: 30_000 },
);

@k8s-ci-robot k8s-ci-robot added the do-not-merge/work-in-progress Indicates that a PR should not merge because it is a work in progress. label May 26, 2026
Copilot AI linked an issue May 26, 2026 that may be closed by this pull request
Exec timeout after 5 minutes #2870
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@k8s-ci-robot k8s-ci-robot added cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. size/XS Denotes a PR that changes 0-9 lines, ignoring generated files. labels May 26, 2026
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k8s-ci-robot commented May 26, 2026

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[APPROVALNOTIFIER] This PR is NOT APPROVED

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

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@k8s-ci-robot k8s-ci-robot added size/M Denotes a PR that changes 30-99 lines, ignoring generated files. and removed size/XS Denotes a PR that changes 0-9 lines, ignoring generated files. labels May 26, 2026
Copilot AI changed the title [WIP] Implement optional ping-pong for exec timeout Add optional websocket keepalive pings for idle Exec sessions May 26, 2026
Copilot AI requested a review from brendandburns May 26, 2026 17:54
mstruebing
mstruebing reviewed May 27, 2026
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/lgtm

Will leave it in this state for now. to give others the chance to look at it.

@k8s-ci-robot k8s-ci-robot added the lgtm "Looks good to me", indicates that a PR is ready to be merged. label May 27, 2026
brendandburns
brendandburns reviewed Jun 1, 2026
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Comment thread src/exec.ts
brendandburns
brendandburns reviewed Jun 1, 2026
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Comment thread src/exec.ts Outdated

const timer = setInterval(() => {
if (conn.readyState === WebSocket.OPEN) {
socket.ping!();

@brendandburns brendandburns Jun 1, 2026

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Please add handling for the pong message.

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brendandburns commented Jun 1, 2026

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@copilot mostly looks good, please add handling for the pong message.

@k8s-ci-robot k8s-ci-robot removed the lgtm "Looks good to me", indicates that a PR is ready to be merged. label Jun 1, 2026
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New changes are detected. LGTM label has been removed.

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linux-foundation-easycla Bot commented Jun 1, 2026 •
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@k8s-ci-robot k8s-ci-robot added cncf-cla: no Indicates the PR's author has not signed the CNCF CLA. and removed cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. labels Jun 1, 2026

Copilot AI commented Jun 1, 2026

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@copilot mostly looks good, please add handling for the pong message.

Addressed in commits 0d44dad and 5ec26ce. Exec keepalive now handles pong by allowing only one outstanding ping until a pong is received, and it cleans up the pong listener on close/error.

Copilot AI requested a review from brendandburns June 1, 2026 03:19
@brendandburns brendandburns marked this pull request as ready for review June 25, 2026 17:02
@kubernetes-prow kubernetes-prow Bot removed the do-not-merge/work-in-progress Indicates that a PR should not merge because it is a work in progress. label Jun 25, 2026
@kubernetes-prow kubernetes-prow Bot requested a review from cjihrig June 25, 2026 17:02
cjihrig
cjihrig approved these changes Jun 26, 2026
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Two minor, optional nits, but LGTM.

Comment thread src/exec.ts
return true;
});
const pingIntervalMs = options?.pingIntervalMs;
if (pingIntervalMs !== undefined && Number.isInteger(pingIntervalMs) && pingIntervalMs > 0) {

@cjihrig cjihrig Jun 26, 2026

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Will this silently ignore invalid pingIntervalMs values? If so, maybe it should throw instead.

Comment thread src/exec.ts
Comment on lines +102 to +111
const onPong = () => {
awaitingPong = false;
};
const clearKeepAlive = () => {
clearInterval(timer);
socket.removeListener?.('pong', onPong);
};
socket.on?.('pong', onPong);
socket.on?.('close', clearKeepAlive);
socket.on?.('error', clearKeepAlive);

@cjihrig cjihrig Jun 26, 2026

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Maybe this block should be conditional based on whether socket.on is a function or not.

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cjihrig, Copilot

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The pull request process is described here

Details Needs approval from an approver in each of these files:

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

@kubernetes-prow kubernetes-prow Bot added the approved Indicates a PR has been approved by an approver from all required OWNERS files. label Jun 26, 2026
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Exec timeout after 5 minutes

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