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worker_threads: settle terminate() from the exit handler #44252

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worker_threads: settle terminate() from the exit handler #44252

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ef8e000
worker_threads: settle terminate() from the exit handler
robobun Sep 29, 2026
225acf1
worker_threads: read the native thread id outside the exit handler
robobun Sep 29, 2026
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1 change: 1 addition & 0 deletions src/js/internal/shared.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -435,6 +435,7 @@ export default {
once,
getLazy,
guardCallback,
reportUncaughtException,
isInsideNodeModules,
resistStopPropagation,

Expand Down
123 changes: 73 additions & 50 deletions src/js/node/worker_threads.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,7 @@ type WebWorker = InstanceType<typeof globalThis.Worker> & {

const EventEmitter = require("node:events");
const { SafeMap } = require("internal/primordials");
const { throwNotImplemented, warnNotImplementedOnce } = require("internal/shared");
const { throwNotImplemented, warnNotImplementedOnce, reportUncaughtException } = require("internal/shared");
const {
validateString,
validateObject,
Expand Down Expand Up @@ -809,6 +809,21 @@ function moveMessagePortToContext(port, _context) {
throwNotImplemented("worker_threads.moveMessagePortToContext");
}

type TerminateCallback = (err: null, exitCode: number) => void;
type PendingTerminate = PromiseWithResolvers<number> & {
// The callbacks of terminate(callback) (DEP0132).
callbacks?: TerminateCallback[];
};

// node also continues its exit handler after a 'message' listener throws: https://github.com/nodejs/node/blob/v26.3.0/lib/internal/event_target.js#L1117-L1119
function emitGuarded(worker: Worker, name: string, value: unknown) {
try {
worker.emit(name, value);
} catch (err) {
reportUncaughtException(err);
}
}

class Worker extends EventEmitter {
#worker: WebWorker;
#performance;
Expand All @@ -823,12 +838,11 @@ class Worker extends EventEmitter {
#stdout;
#stderr;

// this is used by terminate();
// either is the exit code if exited, a promise resolving to the exit code, or undefined if we haven't sent .terminate() yet
#onExitPromise: Promise<number> | number | undefined = undefined;
// Made by the first terminate() on a Worker that has not exited. #onClose settles it after 'exit'.
#pendingTerminate: PendingTerminate | undefined = undefined;
#urlToRevoke = "";
// threadId captured for cleaning up the messaging control port on close.
#messagingThreadId: number | undefined = undefined;
// A copy, because the native id is -1 when the worker's last messages are delivered and node's is not: https://github.com/nodejs/node/blob/v26.3.0/lib/internal/worker.js#L511-L515
#threadId = -1;

constructor(filename: string, options: NodeWorkerOptions = {}) {
super();
Expand Down Expand Up @@ -956,8 +970,8 @@ class Worker extends EventEmitter {
}
// threadId is only assigned once the WebWorker exists; register the hub-side
// control port with the messaging hub now.
this.#messagingThreadId = this.#worker.threadId;
messaging.registerMainThreadPort(this.#messagingThreadId, portToMain);
this.#threadId = this.#worker.threadId;
messaging.registerMainThreadPort(this.#threadId, portToMain);
// The transfer is committed - release fds that were transferred but are
// not referenced from workerData (nothing will deserialize them).
options[kFinalizeJSTransferables]?.();
Expand Down Expand Up @@ -1000,7 +1014,7 @@ class Worker extends EventEmitter {
}

get threadId() {
return this.#worker.threadId;
return this.#exited ? -1 : this.#threadId;
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}

get threadName() {
Expand Down Expand Up @@ -1051,39 +1065,28 @@ class Worker extends EventEmitter {
});
}

// node settles the promise from once("exit"), so removeAllListeners() loses it. Here #onClose settles it: https://github.com/nodejs/node/blob/v26.3.0/lib/internal/worker.js#L476-L491
terminate(callback?: unknown) {
if (typeof callback === "function") {
const hasCallback = typeof callback === "function";
if (hasCallback) {
process.emitWarning(
"Passing a callback to worker.terminate() is deprecated. It returns a Promise instead.",
"DeprecationWarning",
"DEP0132",
);
this.#worker.addEventListener("close", event => callback(null, event.code), { once: true });
}

const onExitPromise = this.#onExitPromise;
// Not a truthy test: after exit #onExitPromise is the exit code, which can be 0;
// falling through would wait on a 'close' event that never fires again.
if (onExitPromise !== undefined) {
// node: terminate() on an already-exited worker resolves with undefined;
// an in-progress terminate (a promise) resolves with the exit code below.
return $isPromise(onExitPromise) ? onExitPromise : Promise.$resolve(undefined);
// node: terminate() on an already-exited worker resolves with undefined.
if (this.#exited) return Promise.$resolve(undefined);

let pending = this.#pendingTerminate;
if (pending === undefined) {
pending = this.#pendingTerminate = Promise.withResolvers<number>();
// Keep the event loop alive until the exit, so the promise of an unref()'ed worker resolves too.
this.#worker.ref();
this.#worker.terminate();
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}

const { resolve, promise } = Promise.withResolvers<number>();
this.#worker.addEventListener(
"close",
event => {
resolve(event.code);
},
{ once: true },
);
// Keep the event loop alive until termination completes so the returned
// promise still resolves even if the worker was unref()'ed.
this.#worker.ref();
this.#worker.terminate();

return (this.#onExitPromise = promise);
if (hasCallback) (pending.callbacks ??= []).push(callback as TerminateCallback);
return pending.promise;
}

postMessage(...args: [any, any]) {
Expand Down Expand Up @@ -1157,7 +1160,7 @@ class Worker extends EventEmitter {
if (includeObjectsCollectedByMinorGC !== undefined)
validateBoolean(includeObjectsCollectedByMinorGC, "options.includeObjectsCollectedByMinorGC");
}
if (this.#exited) {
if (this.#worker.threadId === -1) {
return Promise.$reject($ERR_WORKER_NOT_RUNNING("Worker instance not running"));
}
// Bun has no allocation-sampling heap profiler; yield a valid but empty
Expand All @@ -1168,17 +1171,47 @@ class Worker extends EventEmitter {
}

#onClose(e) {
this.#exited = true;
const code: number = e.code;
try {
this.#exit(code);
} finally {
// A throw from a stdio listener ends #exit, as it ends node's kOnExit. terminate() settles on that path too.
this.#exited = true;
const pending = this.#pendingTerminate;
if (pending !== undefined) {
this.#pendingTerminate = undefined;
const callbacks = pending.callbacks;
if (callbacks !== undefined) {
for (let i = 0; i < callbacks.length; i++) {
try {
callbacks[i](null, code);
} catch (err) {
reportUncaughtException(err);
}
}
}
pending.resolve(code);
}
}
}

// The order of node's kOnExit: the last messages, the exit state, the stdio EOF, then 'exit'. https://github.com/nodejs/node/blob/v26.3.0/lib/internal/worker.js#L393-L410
#exit(code: number) {
// Revoke the eval blob: URL now that the worker has exited; the
// FinalizationRegistry remains only as a GC safety net.
if (this.#urlToRevoke) {
URL.revokeObjectURL(this.#urlToRevoke);
this.#urlToRevoke = "";
}
if (this.#messagingThreadId !== undefined) {
messaging.destroyMainThreadPort(this.#messagingThreadId);
this.#messagingThreadId = undefined;
messaging.destroyMainThreadPort(this.#threadId);
{
let entry;
while ((entry = _receiveMessageOnPort(this.#publicPort)) !== undefined) {
emitGuarded(this, "message", entry.message);
}
this.#publicPort.close();
}
this.#exited = true;
// End captured stdio readables when the worker exits, even if it was
// terminated before its own streams finished.
if (this.#stdout) {
Expand All @@ -1197,17 +1230,7 @@ class Worker extends EventEmitter {
this.#stdin.destroy();
}
this.#stdinPort?.close();
// node delivers everything the worker posted before it exited ahead of
// 'exit' (kOnExit drains the public port), then closes the port.
{
let entry;
while ((entry = _receiveMessageOnPort(this.#publicPort)) !== undefined) {
this.emit("message", entry.message);
}
this.#publicPort.close();
}
this.#onExitPromise = e.code;
this.emit("exit", e.code);
emitGuarded(this, "exit", code);
}

#onError(event: ErrorEvent) {
Expand Down
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