chore(travis): use different port numbers per build

We can't establish multiple SSH tunnels for the same port (for BrowserStack).
This makes it possible to run multiple parallel builds using BrowserStack.

Author: vojtajina

lib/browser-stack/start-tunnel.js

@@ -3,7 +3,7 @@ var http = require('http');
 var BrowserStackTunnel = require('browserstacktunnel-wrapper');
 
 var HOSTNAME = 'localhost';
-var PORTS = [9090, 9876];
+var PORTS = require('../grunt/utils').availablePorts;
 var ACCESS_KEY = process.env.BROWSER_STACK_ACCESS_KEY;
 var READY_FILE = process.env.SAUCE_CONNECT_READY_FILE;
 

lib/grunt/utils.js

@@ -5,6 +5,22 @@ var spawn = require('child_process').spawn;
 var version;
 var CSP_CSS_HEADER = '/* Include this file in your html if you are using the CSP mode. */\n\n';
 
+var PORT_MIN = 8000;
+var PORT_MAX = 9999;
+var TRAVIS_BUILD_NUMBER = parseInt(process.env.TRAVIS_BUILD_NUMBER, 10);
+var getRandomPorts = function() {
+  if (!process.env.TRAVIS) {
+    return [9876, 9877];
+  }
+
+  // Generate two numbers between PORT_MIN and PORT_MAX, based on TRAVIS_BUILD_NUMBER.
+  return [
+    PORT_MIN + (TRAVIS_BUILD_NUMBER % (PORT_MAX - PORT_MIN)),
+    PORT_MIN + ((TRAVIS_BUILD_NUMBER + 100) % (PORT_MAX - PORT_MIN))
+  ];
+};
+
+
 module.exports = {
 
   init: function() {
@@ -279,7 +295,7 @@ module.exports = {
       stream: options && options.stream
     };
 
-    args.push('--port=' + this.sauceLabsAvailablePorts.pop());
+    args.push('--port=' + this.availablePorts.pop());
 
     if (args.indexOf('test:e2e') !== -1 && grunt.option('e2e-browsers')) {
       args.push('--browsers=' + grunt.option('e2e-browsers'));
@@ -295,5 +311,7 @@ module.exports = {
   },
 
   // see http://saucelabs.com/docs/connect#localhost
-  sauceLabsAvailablePorts: [9000, 9001, 9080, 9090, 9876]
+  sauceLabsAvailablePorts: [9000, 9001, 9080, 9090, 9876],
+  // pseudo-random port numbers for BrowserStack
+  availablePorts: getRandomPorts()
 };