module: have a single hooks thread for all workers

lib/internal/main/worker_thread.js

@@ -95,6 +95,7 @@ port.on('message', (message) => {
       filename,
       hasStdin,
       publicPort,
+      hooksPort,
       workerData,
     } = message;
 
@@ -109,6 +110,7 @@ port.on('message', (message) => {
     }
 
     require('internal/worker').assignEnvironmentData(environmentData);
+    require('internal/worker').hooksPort = hooksPort;
 
     if (SharedArrayBuffer !== undefined) {
       // The counter is only passed to the workers created by the main thread,

lib/internal/modules/esm/hooks.js

@@ -35,7 +35,7 @@ const {
 const { exitCodes: { kUnsettledTopLevelAwait } } = internalBinding('errors');
 const { URL } = require('internal/url');
 const { canParse: URLCanParse } = internalBinding('url');
-const { receiveMessageOnPort } = require('worker_threads');
+const { receiveMessageOnPort, isMainThread } = require('worker_threads');
 const {
   isAnyArrayBuffer,
   isArrayBufferView,
@@ -482,6 +482,8 @@ class HooksProxy {
    */
   #worker;
 
+  #portToHooksThread;
+
   /**
    * The last notification ID received from the worker. This is used to detect
    * if the worker has already sent a notification before putting the main
@@ -499,26 +501,38 @@ class HooksProxy {
   #isReady = false;
 
   constructor() {
-    const { InternalWorker } = require('internal/worker');
-    MessageChannel ??= require('internal/worker/io').MessageChannel;
-
+    const { InternalWorker, hooksPort } = require('internal/worker');
     const lock = new SharedArrayBuffer(SHARED_MEMORY_BYTE_LENGTH);
     this.#lock = new Int32Array(lock);
 
-    this.#worker = new InternalWorker(loaderWorkerId, {
-      stderr: false,
-      stdin: false,
-      stdout: false,
-      trackUnmanagedFds: false,
-      workerData: {
-        lock,
-      },
-    });
-    this.#worker.unref(); // ! Allows the process to eventually exit.
-    this.#worker.on('exit', process.exit);
+    if (isMainThread) {
+      // Main thread is the only one that creates the internal single hooks worker
+      this.#worker = new InternalWorker(loaderWorkerId, {
+        stderr: false,
+        stdin: false,
+        stdout: false,
+        trackUnmanagedFds: false,
+        workerData: {
+          lock,
+        },
+      });
+      this.#worker.unref(); // ! Allows the process to eventually exit.
+      this.#worker.on('exit', process.exit);
+      this.#portToHooksThread = this.#worker;
+    } else {
+      this.#portToHooksThread = hooksPort;
+    }
   }
 
   waitForWorker() {
+    // There is one Hooks instance for each worker thread. But only one of these Hooks instances
+    // has an InternalWorker. That was the Hooks instance created for the main thread.
+    // It means for all Hooks instances that are not on the main thread => they are ready because they
+    // delegate to the single InternalWorker anyway.
+    if (!isMainThread) {
+      return;
+    }
+
     if (!this.#isReady) {
       const { kIsOnline } = require('internal/worker');
       if (!this.#worker[kIsOnline]) {
@@ -535,6 +549,37 @@ class HooksProxy {
     }
   }
 
+  #postMessageToWorker(method, type, transferList, args) {
+    this.waitForWorker();
+
+    MessageChannel ??= require('internal/worker/io').MessageChannel;
+
+    const {
+      port1: fromHooksThread,
+      port2: toHooksThread,
+    } = new MessageChannel();
+
+    // Pass work to the worker.
+    debug(`post ${type} message to worker`, { method, args, transferList });
+    const usedTransferList = [toHooksThread];
+    if (transferList) {
+      ArrayPrototypePushApply(usedTransferList, transferList);
+    }
+
+    this.#portToHooksThread.postMessage(
+      {
+        __proto__: null,
+        args,
+        lock: this.#lock,
+        method,
+        port: toHooksThread,
+      },
+      usedTransferList,
+    );
+
+    return fromHooksThread;
+  }
+
   /**
    * Invoke a remote method asynchronously.
    * @param {string} method Method to invoke
@@ -543,22 +588,7 @@ class HooksProxy {
    * @returns {Promise<any>}
    */
   async makeAsyncRequest(method, transferList, ...args) {
-    this.waitForWorker();
-
-    MessageChannel ??= require('internal/worker/io').MessageChannel;
-    const asyncCommChannel = new MessageChannel();
-
-    // Pass work to the worker.
-    debug('post async message to worker', { method, args, transferList });
-    const finalTransferList = [asyncCommChannel.port2];
-    if (transferList) {
-      ArrayPrototypePushApply(finalTransferList, transferList);
-    }
-    this.#worker.postMessage({
-      __proto__: null,
-      method, args,
-      port: asyncCommChannel.port2,
-    }, finalTransferList);
+    const fromHooksThread = this.#postMessageToWorker(method, 'Async', transferList, args);
 
     if (this.#numberOfPendingAsyncResponses++ === 0) {
       // On the next lines, the main thread will await a response from the worker thread that might
@@ -567,7 +597,11 @@ class HooksProxy {
       // However we want to keep the process alive until the worker thread responds (or until the
       // event loop of the worker thread is also empty), so we ref the worker until we get all the
       // responses back.
-      this.#worker.ref();
+      if (this.#worker) {
+        this.#worker.ref();
+      } else {
+        this.#portToHooksThread.ref();
+      }
     }
 
     let response;
@@ -576,18 +610,26 @@ class HooksProxy {
       await AtomicsWaitAsync(this.#lock, WORKER_TO_MAIN_THREAD_NOTIFICATION, this.#workerNotificationLastId).value;
       this.#workerNotificationLastId = AtomicsLoad(this.#lock, WORKER_TO_MAIN_THREAD_NOTIFICATION);
 
-      response = receiveMessageOnPort(asyncCommChannel.port1);
+      response = receiveMessageOnPort(fromHooksThread);
     } while (response == null);
     debug('got async response from worker', { method, args }, this.#lock);
 
     if (--this.#numberOfPendingAsyncResponses === 0) {
       // We got all the responses from the worker, its job is done (until next time).
-      this.#worker.unref();
+      if (this.#worker) {
+        this.#worker.unref();
+      } else {
+        this.#portToHooksThread.unref();
+      }
+    }
+
+    if (response.message.status === 'exit') {
+      process.exit(response.message.body);
     }
 
-    const body = this.#unwrapMessage(response);
-    asyncCommChannel.port1.close();
-    return body;
+    fromHooksThread.close();
+
+    return this.#unwrapMessage(response);
   }
 
   /**
@@ -598,11 +640,7 @@ class HooksProxy {
    * @returns {any}
    */
   makeSyncRequest(method, transferList, ...args) {
-    this.waitForWorker();
-
-    // Pass work to the worker.
-    debug('post sync message to worker', { method, args, transferList });
-    this.#worker.postMessage({ __proto__: null, method, args }, transferList);
+    const fromHooksThread = this.#postMessageToWorker(method, 'Sync', transferList, args);
 
     let response;
     do {
@@ -611,14 +649,17 @@ class HooksProxy {
       AtomicsWait(this.#lock, WORKER_TO_MAIN_THREAD_NOTIFICATION, this.#workerNotificationLastId);
       this.#workerNotificationLastId = AtomicsLoad(this.#lock, WORKER_TO_MAIN_THREAD_NOTIFICATION);
 
-      response = this.#worker.receiveMessageSync();
+      response = receiveMessageOnPort(fromHooksThread);
     } while (response == null);
     debug('got sync response from worker', { method, args });
     if (response.message.status === 'never-settle') {
       process.exit(kUnsettledTopLevelAwait);
     } else if (response.message.status === 'exit') {
       process.exit(response.message.body);
     }
+
+    fromHooksThread.close();
+
     return this.#unwrapMessage(response);
   }
 

lib/internal/modules/esm/loader.js

@@ -41,6 +41,7 @@ const { ModuleWrap, kEvaluating, kEvaluated } = internalBinding('module_wrap');
 const {
   urlToFilename,
 } = require('internal/modules/helpers');
+const { isMainThread } = require('worker_threads');
 let defaultResolve, defaultLoad, defaultLoadSync, importMetaInitializer;
 
 /**
@@ -607,21 +608,26 @@ class CustomizedModuleLoader {
    */
   constructor() {
     getHooksProxy();
+    _hasCustomizations = true;
   }
 
   /**
-   * Register some loader specifier.
+   * Register a loader specifier.
    * @param {string} originalSpecifier The specified URL path of the loader to
    *                                   be registered.
    * @param {string} parentURL The parent URL from where the loader will be
    *                           registered if using it package name as specifier
    * @param {any} [data] Arbitrary data to be passed from the custom loader
    * (user-land) to the worker.
    * @param {any[]} [transferList] Objects in `data` that are changing ownership
-   * @returns {{ format: string, url: URL['href'] }}
+   * @returns {{ format: string, url: URL['href'] } | undefined}
    */
   register(originalSpecifier, parentURL, data, transferList) {
-    return hooksProxy.makeSyncRequest('register', transferList, originalSpecifier, parentURL, data);
+    if (isMainThread) {
+      // Only the main thread has a Hooks instance with worker thread. All other Worker threads
+      // delegate their hooks to the HooksThread of the main thread.
+      return hooksProxy.makeSyncRequest('register', transferList, originalSpecifier, parentURL, data);
+    }
   }
 
   /**
@@ -719,6 +725,12 @@ function getHooksProxy() {
   return hooksProxy;
 }
 
+let _hasCustomizations = false;
+function hasCustomizations() {
+  return _hasCustomizations;
+}
+
+
 let cascadedLoader;
 
 /**
@@ -780,6 +792,7 @@ function register(specifier, parentURL = undefined, options) {
 
 module.exports = {
   createModuleLoader,
+  hasCustomizations,
   getHooksProxy,
   getOrInitializeCascadedLoader,
   register,