feat: Implement random port retry logic

bin/utils.js

@@ -8,6 +8,7 @@
   space-before-function-paren
 */
 const open = require('opn');
+const portfinder = require('portfinder');
 
 const colors = {
   info (useColor, msg) {
@@ -105,10 +106,44 @@ function bonjour (options) {
   });
 }
 
+function tryParseInt(input) {
+  const output = parseInt(input, 10);
+  if (Number.isNaN(output)) {
+    return null;
+  }
+  return output;
+}
+
+function findPort(server, defaultPort, defaultPortRetry, fn) {
+  let tryCount = 0;
+  server.listeningApp.on('error', (err) => {
+    if (err.code === 'EADDRINUSE') {
+      if (tryCount < defaultPortRetry) {
+        portfinder.basePort = defaultPort;
+        tryCount += 1;
+        portfinder.getPort((err, port) => {
+          fn(err, port);
+        });
+      } else {
+        fn(err);
+      }
+    } else {
+      throw err;
+    }
+  });
+  portfinder.basePort = defaultPort;
+  tryCount += 1;
+  portfinder.getPort((err, port) => {
+    fn(err, port);
+  });
+}
+
 module.exports = {
   status,
   colors,
   version,
   bonjour,
-  defaultTo
+  defaultTo,
+  tryParseInt,
+  findPort
 };

bin/webpack-dev-server.js

@@ -19,7 +19,6 @@ const fs = require('fs');
 const net = require('net');
 const path = require('path');
 
-const portfinder = require('portfinder');
 const importLocal = require('import-local');
 
 const yargs = require('yargs');
@@ -32,7 +31,9 @@ const {
   status,
   version,
   bonjour,
-  defaultTo
+  defaultTo,
+  tryParseInt,
+  findPort
 } = require('./utils');
 
 const Server = require('../lib/Server');
@@ -97,6 +98,12 @@ const config = require('webpack-cli/bin/convert-argv')(yargs, argv, {
 // we should use portfinder.
 const DEFAULT_PORT = 8080;
 
+// Try to find unused port and listen on it for 3 times,
+// if port is not specified in options.
+// Because NaN == null is false, defaultTo fails if parseInt returns NaN
+// so the tryParseInt function is introduced to handle NaN
+const defaultPortRetry = defaultTo(tryParseInt(process.env.DEFAULT_PORT_RETRY), 3);
+
 function processOptions (config) {
   // processOptions {Promise}
   if (typeof config.then === 'function') {
@@ -305,23 +312,7 @@ function processOptions (config) {
     ? defaultTo(options.port, argv.port)
     : defaultTo(argv.port, options.port);
 
-  if (options.port != null) {
-    startDevServer(config, options);
-
-    return;
-  }
-
-  portfinder.basePort = DEFAULT_PORT;
-
-  portfinder.getPort((err, port) => {
-    if (err) {
-      throw err;
-    }
-
-    options.port = port;
-
-    startDevServer(config, options);
-  });
+  startDevServer(config, options);
 }
 
 function startDevServer(config, options) {
@@ -404,21 +395,35 @@ function startDevServer(config, options) {
         status(uri, options, log, argv.color);
       });
     });
-  } else {
+    return;
+  }
+
+  const startServer = () => {
     server.listen(options.port, options.host, (err) => {
       if (err) {
         throw err;
       }
-
       if (options.bonjour) {
         bonjour(options);
       }
-
       const uri = createDomain(options, server.listeningApp) + suffix;
-
       status(uri, options, log, argv.color);
     });
+  };
+
+  if (options.port) {
+    startServer();
+    return;
   }
+
+  // only run port finder if no port as been specified
+  findPort(server, DEFAULT_PORT, defaultPortRetry, (err, port) => {
+    if (err) {
+      throw err;
+    }
+    options.port = port;
+    startServer();
+  });
 }
 
 processOptions(config);

test/Util.test.js

@@ -1,9 +1,12 @@
 'use strict';
 
+const EventEmitter = require('events');
+const assert = require('assert');
 const webpack = require('webpack');
 const internalIp = require('internal-ip');
 const Server = require('../lib/Server');
 const createDomain = require('../lib/utils/createDomain');
+const findPort = require('../bin/utils').findPort;
 const config = require('./fixtures/simple-config/webpack.config');
 
 describe('check utility functions', () => {
@@ -104,3 +107,38 @@ describe('check utility functions', () => {
     }
   });
 });
+
+describe('findPort cli utility function', () => {
+  let mockServer = null;
+  beforeEach(() => {
+    mockServer = {
+      listeningApp: new EventEmitter()
+    };
+  });
+  afterEach(() => {
+    mockServer.listeningApp.removeAllListeners('error');
+    mockServer = null;
+  });
+  it('should find empty port starting from defaultPort', (done) => {
+    findPort(mockServer, 8180, 3, (err, port) => {
+      assert(err == null);
+      assert(port === 8180);
+      done();
+    });
+  });
+  it('should retry finding port for up to defaultPortRetry times', (done) => {
+    let count = 0;
+    const defaultPortRetry = 5;
+    findPort(mockServer, 8180, defaultPortRetry, (err) => {
+      if (err == null) {
+        count += 1;
+        const mockError = new Error('EADDRINUSE');
+        mockError.code = 'EADDRINUSE';
+        mockServer.listeningApp.emit('error', mockError);
+        return;
+      }
+      assert(count === defaultPortRetry);
+      done();
+    });
+  });
+});

test/cli.test.js

@@ -59,4 +59,61 @@ describe('CLI', () => {
       done();
     });
   }).timeout(18000);
+
+  it('should use different random port when multiple instances are started on different processes', (done) => {
+    const cliPath = path.resolve(__dirname, '../bin/webpack-dev-server.js');
+    const examplePath = path.resolve(__dirname, '../examples/cli/public');
+
+    const cp = execa('node', [ cliPath ], { cwd: examplePath });
+    const cp2 = execa('node', [ cliPath ], { cwd: examplePath });
+
+    const runtime = {
+      cp: {
+        port: null,
+        done: false
+      },
+      cp2: {
+        port: null,
+        done: false
+      }
+    };
+
+    cp.stdout.on('data', (data) => {
+      const bits = data.toString();
+      const portMatch = /Project is running at http:\/\/localhost:(\d*)\//.exec(bits);
+      if (portMatch) {
+        runtime.cp.port = portMatch[1];
+      }
+      if (/Compiled successfully/.test(bits)) {
+        assert(cp.pid !== 0);
+        cp.kill('SIGINT');
+      }
+    });
+    cp2.stdout.on('data', (data) => {
+      const bits = data.toString();
+      const portMatch = /Project is running at http:\/\/localhost:(\d*)\//.exec(bits);
+      if (portMatch) {
+        runtime.cp2.port = portMatch[1];
+      }
+      if (/Compiled successfully/.test(bits)) {
+        assert(cp.pid !== 0);
+        cp2.kill('SIGINT');
+      }
+    });
+
+    cp.on('exit', () => {
+      runtime.cp.done = true;
+      if (runtime.cp2.done) {
+        assert(runtime.cp.port !== runtime.cp2.port);
+        done();
+      }
+    });
+    cp2.on('exit', () => {
+      runtime.cp2.done = true;
+      if (runtime.cp.done) {
+        assert(runtime.cp.port !== runtime.cp2.port);
+        done();
+      }
+    });
+  }).timeout(18000);
 });