worker: emit worker exit notifications on BroadcastChannel by SudhansuBandha · Pull Request #65575 · nodejs/node

SudhansuBandha · 2026-08-27T06:39:13Z

Expose worker termination notifications through BroadcastChannel so consumers can observe when a worker exits and inspect its thread ID and exit code.

Fixes: #59053

Labeeb2339

The current lint-cpp check reports 10 style errors in the new C++ code, so this PR is not yet lint-clean. Notably: trailing whitespace at src/node_messaging.cc:855 and src/node_messaging.h:194/233/235, an over-80-character line at src/node_messaging.cc:896, missing spaces in if(environment->is_stopping()) at :970, and incorrect indentation around WorkerExitNotification in src/node_messaging.h:226-229. Running the repository C++ formatter/linter and committing its output should address these before the functional review proceeds.

codecov · 2026-08-27T08:17:49Z

Codecov Report

❌ Patch coverage is 98.43750% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 90.07%. Comparing base (9f37c77) to head (d8a79bf).
⚠️ Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
src/node_messaging.cc	98.27%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #65575      +/-   ##
==========================================
+ Coverage   90.05%   90.07%   +0.02%     
==========================================
  Files         751      751              
  Lines      254868   254944      +76     
  Branches    48107    48122      +15     
==========================================
+ Hits       229531   229653     +122     
+ Misses      16511    16471      -40     
+ Partials     8826     8820       -6

Files with missing lines	Coverage Δ
lib/internal/worker/io.js	`99.20% <100.00%> (+<0.01%)`	⬆️
src/node_messaging.h	`63.15% <ø> (ø)`
src/node_messaging.cc	`83.51% <98.27%> (+0.47%)`	⬆️

... and 40 files with indirect coverage changes

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addaleax · 2026-08-27T15:05:01Z

 * Type: {Function} Invoked with a received message cannot be
  deserialized.

+### `broadcastChannel.onworkerexited`


This needs a YAML tag for version history tracking

Updated the fix in latest commit

addaleax · 2026-08-27T15:05:56Z

+
+  if (worker_exit_notifications_.empty()) return false;
+
+  *notification = worker_exit_notifications_.front();


Prefer std::optional<> instead of assigning to out parameters (esp. if they have non-trivial types)

Updated the fix in latest commit

addaleax · 2026-08-27T15:07:12Z

+        return;
+      }
+      continue;
+    }


This is duplicating a significant amount of logic – is there a reason that this needs to be a new message type, and cannot be something that would be conveyed through normal messages in the queue?

I tried to implement a separate pipeline since this notification is related to worker lifecycle instead of inter thread messages of Broadcast Channel. If this is not something to be done then I will update the PR to use existing pipeline for emitting these lifecycle events.

I think that would significantly simplify the implementation and make it easier to write consumers -- events will happen in order from their perspective, rather than seeing a worker exit before all its messages have been sent

Sure, I will implement the suggested changes. Thanks for your feedback!!

Updated the implementation to use existing queue for these events

addaleax · 2026-08-27T15:07:46Z

+      const ExitCode exit_code = environment->exit_code(ExitCode::kNoFailure);
+
+      Debug(this,
+            "Worker exiting: thread_id=%" PRIu64 ", exit_code=%d",


Suggested change

"Worker exiting: thread_id=%" PRIu64 ", exit_code=%d",

"Worker exiting: thread_id=%d, exit_code=%d",

Debug() doesn't care about the actual type anyway

Updated the fix in latest commit

SudhansuBandha · 2026-09-03T07:10:30Z

node/src/node_messaging.cc

Line 823 in 144e679

HandleScope handle_scope(env()->isolate());

node/src/node_messaging.cc

Line 853 in 144e679

HandleScope handle_scope(env()->isolate());

I have observed the same line being present twice in OnMessage handler I have kept the first and removed the second. If this is not to be done then please let me know @addaleax I will revert it.

MikeMcC399 · 2026-09-18T08:15:35Z

The GitHub Actions CI workflow had previously failed due to problems with GitHub.

I triggered re-runs, however there are now other failures.

The PR branch is now more that 300 commits behind the main branch, and some issues that caused CI failures have been fixed in the meantime.

Please rebase the branch in this PR according to the Pull requests documentation to make sure that all available fixes are included.

Expose worker termination notifications through BroadcastChannel so consumers can observe when a worker exits andinspect its thread ID and exit code. Fixes: nodejs#59053 Signed-off-by: SudhansuBandha <bandhasudhansu@gmail.com>

MikeMcC399 · 2026-09-18T14:00:36Z

GitHub Actions CI workflow tests are hanging up and will probably time out after the default 6 hour maximum duration is reached.

It does not look like other current PRs have this issue.

See Pull requests > Step 6: Test

Before submitting your changes in a pull request, always run the full Node.js test suite.

with further details under BUILDING > Running tests.

nodejs-github-bot added c++ Issues and PRs that require attention from people who are familiar with C++. needs-ci PRs that need a full CI run. worker Issues and PRs related to the worker_threads module and Worker API. labels Aug 27, 2026

SudhansuBandha mentioned this pull request Aug 27, 2026

BroadcastChannel doesn't fill in useful MessageEvent fields like source, or ports #59053

Open

Labeeb2339 reviewed Aug 27, 2026

View reviewed changes

SudhansuBandha force-pushed the worker-lifecycle-broadcast-channel branch from 4dd297f to d8a79bf Compare August 27, 2026 15:04

addaleax requested changes Aug 27, 2026

View reviewed changes

SudhansuBandha requested a review from addaleax September 3, 2026 07:11

SudhansuBandha force-pushed the worker-lifecycle-broadcast-channel branch from f23efdb to b1c9fb9 Compare September 3, 2026 15:22

SudhansuBandha added 3 commits September 18, 2026 13:52

worker: emit worker exit notifications on BroadcastChannel

0e4bba8

Expose worker termination notifications through BroadcastChannel so consumers can observe when a worker exits andinspect its thread ID and exit code. Fixes: nodejs#59053 Signed-off-by: SudhansuBandha <bandhasudhansu@gmail.com>

worker: updated worker exit notification messaging pipeline

ac90798

worker: resolved clang lint issues

f3007df

SudhansuBandha force-pushed the worker-lifecycle-broadcast-channel branch from b1c9fb9 to f3007df Compare September 18, 2026 08:23


		if (worker_exit_notifications_.empty()) return false;

		*notification = worker_exit_notifications_.front();

	"Worker exiting: thread_id=%" PRIu64 ", exit_code=%d",
	"Worker exiting: thread_id=%d, exit_code=%d",

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addaleax Aug 27, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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SudhansuBandha commented Sep 3, 2026

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MikeMcC399 commented Sep 18, 2026

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MikeMcC399 commented Sep 18, 2026

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