[fix] Emit at most one event per event loop iteration

Fixes #2216

Author: lpinca

lib/receiver.js

@@ -13,13 +13,6 @@ const { concat, toArrayBuffer, unmask } = require('./buffer-util');
 const { isValidStatusCode, isValidUTF8 } = require('./validation');
 
 const FastBuffer = Buffer[Symbol.species];
-const promise = Promise.resolve();
-
-//
-// `queueMicrotask()` is not available in Node.js < 11.
-//
-const queueTask =
- typeof queueMicrotask === 'function' ? queueMicrotask : queueMicrotaskShim;
 
 const GET_INFO = 0;
 const GET_PAYLOAD_LENGTH_16 = 1;
@@ -577,7 +570,7 @@ class Receiver extends Writable {
  this._state = GET_INFO;
  } else {
  this._state = DEFER_EVENT;
- queueTask(() => {
+ setImmediate(() => {
  this.emit('message', data, true);
  this._state = GET_INFO;
  this.startLoop(cb);
@@ -604,7 +597,7 @@ class Receiver extends Writable {
  this._state = GET_INFO;
  } else {
  this._state = DEFER_EVENT;
- queueTask(() => {
+ setImmediate(() => {
  this.emit('message', buf, false);
  this._state = GET_INFO;
  this.startLoop(cb);
@@ -675,7 +668,7 @@ class Receiver extends Writable {
  this._state = GET_INFO;
  } else {
  this._state = DEFER_EVENT;
- queueTask(() => {
+ setImmediate(() => {
  this.emit(this._opcode === 0x09 ? 'ping' : 'pong', data);
  this._state = GET_INFO;
  this.startLoop(cb);
@@ -711,32 +704,3 @@ class Receiver extends Writable {
 }
 
 module.exports = Receiver;
-
-/**
- * A shim for `queueMicrotask()`.
- *
- * @param {Function} cb Callback
- */
-function queueMicrotaskShim(cb) {
- promise.then(cb).catch(throwErrorNextTick);
-}
-
-/**
- * Throws an error.
- *
- * @param {Error} err The error to throw
- * @private
- */
-function throwError(err) {
- throw err;
-}
-
-/**
- * Throws an error in the next tick.
- *
- * @param {Error} err The error to throw
- * @private
- */
-function throwErrorNextTick(err) {
- process.nextTick(throwError, err);
-}

test/receiver.test.js

@@ -1085,17 +1085,21 @@ describe('Receiver', () => {
  receiver.write(Buffer.from([0x88, 0x03, 0x03, 0xe8, 0xf8]));
  });
 
- it('emits at most one event per microtask', (done) => {
+ it('emits at most one event per event loop iteration', (done) => {
  const actual = [];
  const expected = [
  '1',
- 'microtask 1',
+ '- 1',
+ '-- 1',
  '2',
- 'microtask 2',
+ '- 2',
+ '-- 2',
  '3',
- 'microtask 3',
+ '- 3',
+ '-- 3',
  '4',
- 'microtask 4'
+ '- 4',
+ '-- 4'
  ];
 
  function listener(data) {
@@ -1104,12 +1108,16 @@ describe('Receiver', () => {
 
  // `queueMicrotask()` is not available in Node.js < 11.
  Promise.resolve().then(() => {
- actual.push(`microtask ${message}`);
+ actual.push(`- ${message}`);
 
- if (actual.length === 8) {
- assert.deepStrictEqual(actual, expected);
- done();
- }
+ Promise.resolve().then(() => {
+ actual.push(`-- ${message}`);
+
+ if (actual.length === 12) {
+ assert.deepStrictEqual(actual, expected);
+ done();
+ }
+ });
  });
  }
 

test/websocket.test.js

@@ -4205,8 +4205,7 @@ describe('WebSocket', () => {
 
  if (messages.push(message.toString()) > 1) return;
 
- // `queueMicrotask()` is not available in Node.js < 11.
- Promise.resolve().then(() => {
+ setImmediate(() => {
  process.nextTick(() => {
  assert.strictEqual(ws._receiver._state, 5);
  ws.close(1000);
@@ -4456,8 +4455,7 @@ describe('WebSocket', () => {
 
  if (messages.push(message.toString()) > 1) return;
 
- // `queueMicrotask()` is not available in Node.js < 11.
- Promise.resolve().then(() => {
+ setImmediate(() => {
  process.nextTick(() => {
  assert.strictEqual(ws._receiver._state, 5);
  ws.terminate();