fix(socket-mode): stop waiting on a close handshake Slack never completes by WilliamBergamin · Pull Request #2819 · slackapi/node-slack-sdk

WilliamBergamin · 2026-11-05T17:41:50Z

Summary

This pull request stops disconnect() from waiting 5 seconds or more on a close handshake that Slack never completes.

Fixes #2752. Supersedes #2697 (thanks @Grmiade, credited as co-author).

The cause: undici marks the socket CLOSING once the close frames are exchanged, but only fires close when the peer ends TCP. Slack never does, so disconnect() waited until the pong watchdog gave up (about clientPingTimeout, with the A pong wasn't received warning) or until the 30s fallback timer.

🟢 The close-handshake timeout drops from 30s to 1s, logged at debug since it is the expected path against Slack.
🟢 The ping/pong heartbeat stops once the close frame is sent, so the timeout owns the wait and the false pong warning is gone.
🟢 When Slack starts the close handshake, the socket is terminated on the next heartbeat tick. undici's ping() silently does nothing while CLOSING, so before this only the watchdog caught it.

Why 1s and not 0: the wait lets acks queued just before disconnect() (bolt ack() then app.stop()) reach Slack before the socket is destroyed, and it still works with a custom dispatcher, where the SDK can't reach the underlying socket.

Testing

The updated and new unit tests fail on main.

To check by hand against a build of this branch:

Run slack-shutdown.mjs from SocketModeClient.disconnect() takes ~5 seconds to close on 3.0.1 #2752 with a real xapp- token and press Ctrl+C: disconnect() resolves in about 1s with no pong warning (5 to 6.6s on main).
Against a local peer that never answers the close frame: 6.17s with a pong warning on main, 1.00s with no warning on this branch.

Requirements

I've read and understood the Contributing Guidelines and have done my best effort to follow them.
I've read and agree to the Code of Conduct.

🤖 Generated with Claude Code

…etes undici marks the socket CLOSING when the close handshake completes but only fires "close" once the peer ends TCP, which Slack never does. disconnect() therefore waited for the pong watchdog (about clientPingTimeout) or the 30s fallback timer. - Lower the close-handshake timeout to 1s and log it at debug: it is the expected path against Slack. - Stop the ping/pong heartbeat once the close frame is sent, so the timeout owns the wait and the spurious "A pong wasn't received" warning is gone. - When Slack starts the close handshake, terminate on the next heartbeat tick; undici's ping() silently does nothing while CLOSING. Fixes #2752. Supersedes #2697. Co-authored-by: Grmiade <jeremy@payfit.com> Co-authored-by: Claude <svc-devxp-claude@slack-corp.com>

changeset-bot · 2026-11-05T17:41:58Z

🦋 Changeset detected

Latest commit: 76c94cc

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@slack/socket-mode	Patch

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codecov · 2026-11-05T17:43:37Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.90%. Comparing base (822f6a4) to head (76c94cc).
⚠️ Report is 3 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2819   +/-   ##
=======================================
  Coverage   93.89%   93.90%           
=======================================
  Files          66       66           
  Lines       10571    10581   +10     
  Branches      611      611           
=======================================
+ Hits         9926     9936   +10     
- Misses        609      611    +2     
+ Partials       36       34    -2

Flag	Coverage Δ
cli-hooks	`93.84% <100.00%> (+0.09%)`	⬆️
cli-test	`93.84% <100.00%> (+0.09%)`	⬆️
logger	`93.84% <100.00%> (+0.09%)`	⬆️
oauth	`93.84% <100.00%> (+0.09%)`	⬆️
socket-mode	`93.84% <100.00%> (+0.09%)`	⬆️
web-api	`93.84% <100.00%> (+0.09%)`	⬆️
webhook	`93.84% <100.00%> (+0.09%)`	⬆️

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Co-Authored-By: Claude <svc-devxp-claude@slack-corp.com>

…ake short The test still passed with stopMonitoringPings() removed from disconnect(), since the heartbeat's CLOSING check cleaned up early with no ping or warn. Asserting no close before the 1s timeout guards the ack window, and the test name now says what it checks. Co-Authored-By: Claude <svc-devxp-claude@slack-corp.com>

zimeg

🔌 @WilliamBergamin LGTM! Stopping the heartbeat once the close frame is sent is a clean fix, and thanks for the tests that fail on main ✨

mwbrooks

✅ Thanks @WilliamBergamin! Taking app.stop() from 5s down to about 1s is a lovely quality-of-life fix for Bolt apps.

mwbrooks · 2026-11-06T05:13:38Z

          this.logger.error('WebSocket not available, skipping ping.');
          return;
        }
+        if (this.websocket.readyState === WebSocket.CLOSING) {


praise: Terminating on the next heartbeat tick is a neat answer to undici's silent ping() while CLOSING, and disconnect() already routes that state straight to cleanup().

WilliamBergamin mentioned this pull request Nov 5, 2026

fix(socket-mode): open the replacement connection before closing the old one on refresh #2821

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2 tasks done

Merge branch 'main' into fix-issue-2752

a78bfb5

WilliamBergamin commented Nov 5, 2026

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Comment thread packages/socket-mode/src/SlackWebSocket.ts Resolved

WilliamBergamin and others added 3 commits November 5, 2026 12:55

chore(socket-mode): drop redundant stopMonitoringPings comment

efe703b

Co-Authored-By: Claude <svc-devxp-claude@slack-corp.com>

Merge branch 'main' into fix-issue-2752

8730184

WilliamBergamin self-assigned this Nov 5, 2026

WilliamBergamin added bug M-T: A confirmed bug report. Issues are confirmed when the reproduction steps are documented semver:patch pkg:socket-mode applies to `@slack/socket-mode` labels Nov 5, 2026

Merge branch 'main' into fix-issue-2752

76c94cc

WilliamBergamin marked this pull request as ready for review November 5, 2026 20:50

WilliamBergamin requested a review from a team as a code owner November 5, 2026 20:50

zimeg added this to the socket-mode@next milestone Nov 6, 2026

zimeg approved these changes Nov 6, 2026

View reviewed changes

mwbrooks approved these changes Nov 6, 2026

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WilliamBergamin merged commit 1d3a1af into main Nov 6, 2026
22 checks passed

WilliamBergamin deleted the fix-issue-2752 branch November 6, 2026 14:14

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fix(socket-mode): stop waiting on a close handshake Slack never completes - #2819

fix(socket-mode): stop waiting on a close handshake Slack never completes#2819
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