Use a fixed worker pool size

js/global_worker_pool.js

@@ -0,0 +1,16 @@
+'use strict';
+var WorkerPool = require('./util/worker_pool');
+
+var globalWorkerPool;
+
+/**
+ * Creates (if necessary) and returns the single, global WorkerPool instance
+ * to be shared across each Map
+ * @private
+ */
+module.exports = function getGlobalWorkerPool () {
+    if (!globalWorkerPool) {
+        globalWorkerPool = new WorkerPool();
+    }
+    return globalWorkerPool;
+};

js/mapbox-gl.js

@@ -13,6 +13,8 @@ mapboxgl.Attribution = require('./ui/control/attribution');
 mapboxgl.Popup = require('./ui/popup');
 mapboxgl.Marker = require('./ui/marker');
 
+mapboxgl.WorkerPool = require('./util/worker_pool');
+
 mapboxgl.Style = require('./style/style');
 
 mapboxgl.LngLat = require('./geo/lng_lat');

js/style/style.js

@@ -18,15 +18,13 @@ var QueryFeatures = require('../source/query_features');
 var SourceCache = require('../source/source_cache');
 var styleSpec = require('./style_spec');
 var StyleFunction = require('./style_function');
-var WorkerPool = require('../util/worker_pool');
-
-var workerPool = new WorkerPool();
+var getWorkerPool = require('../global_worker_pool');
 
 module.exports = Style;
 
-function Style(stylesheet, animationLoop, workerCount) {
+function Style(stylesheet, animationLoop) {
     this.animationLoop = animationLoop || new AnimationLoop();
-    this.dispatcher = new Dispatcher(workerPool, workerCount || 1, this);
+    this.dispatcher = new Dispatcher(getWorkerPool(), this);
     this.spriteAtlas = new SpriteAtlas(1024, 1024);
     this.lineAtlas = new LineAtlas(256, 512);
 

js/ui/map.js

@@ -52,8 +52,7 @@ var defaultOptions = {
     failIfMajorPerformanceCaveat: false,
     preserveDrawingBuffer: false,
 
-    trackResize: true,
-    workerCount: Math.max(browser.hardwareConcurrency - 1, 1)
+    trackResize: true
 };
 
 /**
@@ -114,7 +113,6 @@ var defaultOptions = {
  * @param {number} [options.zoom=0] The initial zoom level of the map. If `zoom` is not specified in the constructor options, Mapbox GL JS will look for it in the map's style object. If it is not specified in the style, either, it will default to `0`.
  * @param {number} [options.bearing=0] The initial bearing (rotation) of the map, measured in degrees counter-clockwise from north. If `bearing` is not specified in the constructor options, Mapbox GL JS will look for it in the map's style object. If it is not specified in the style, either, it will default to `0`.
  * @param {number} [options.pitch=0] The initial pitch (tilt) of the map, measured in degrees away from the plane of the screen (0-60). If `pitch` is not specified in the constructor options, Mapbox GL JS will look for it in the map's style object. If it is not specified in the style, either, it will default to `0`.
- * @param {number} [options.workerCount=navigator.hardwareConcurrency - 1] The number of WebWorkers that Mapbox GL JS should use to process vector tile data.
  * @example
  * var map = new mapboxgl.Map({
  *   container: 'map',
@@ -128,15 +126,10 @@ var Map = module.exports = function(options) {
 
     options = util.extend({}, defaultOptions, options);
 
-    if (options.workerCount < 1) {
-        throw new Error('workerCount must an integer greater than or equal to 1.');
-    }
-
     this._interactive = options.interactive;
     this._failIfMajorPerformanceCaveat = options.failIfMajorPerformanceCaveat;
     this._preserveDrawingBuffer = options.preserveDrawingBuffer;
     this._trackResize = options.trackResize;
-    this._workerCount = options.workerCount;
     this._bearingSnap = options.bearingSnap;
 
     if (typeof options.container === 'string') {
@@ -641,7 +634,7 @@ util.extend(Map.prototype, /** @lends Map.prototype */{
         } else if (style instanceof Style) {
             this.style = style;
         } else {
-            this.style = new Style(style, this.animationLoop, this._workerCount);
+            this.style = new Style(style, this.animationLoop);
         }
 
         this.style

js/util/dispatcher.js

@@ -12,12 +12,12 @@ module.exports = Dispatcher;
  * @interface Dispatcher
  * @private
  */
-function Dispatcher(workerPool, length, parent) {
+function Dispatcher(workerPool, parent) {
     this.workerPool = workerPool;
     this.actors = [];
     this.currentActor = 0;
     this.id = util.uniqueId();
-    var workers = this.workerPool.acquire(this.id, length);
+    var workers = this.workerPool.acquire(this.id);
     for (var i = 0; i < workers.length; i++) {
         var worker = workers[i];
         var actor = new Actor(worker, parent, this.id);

js/util/worker_pool.js

@@ -2,33 +2,36 @@
 
 var assert = require('assert');
 var WebWorker = require('./web_worker');
+var browser = require('./browser');
 
 module.exports = WorkerPool;
 
+WorkerPool.WORKER_COUNT = Math.max(browser.hardwareConcurrency - 1, 1);
+
 function WorkerPool() {
-    this.workers = [];
+    this.workerCount = WorkerPool.WORKER_COUNT;
     this.active = {};
 }
 
 WorkerPool.prototype = {
-    acquire: function (mapId, workerCount) {
-        this._resize(workerCount);
-        this.active[mapId] = workerCount;
-        return this.workers.slice(0, workerCount);
+    acquire: function (mapId) {
+        if (!this.workers) {
+            assert(typeof this.workerCount === 'number');
+            this.workers = [];
+            while (this.workers.length < this.workerCount) {
+                this.workers.push(new WebWorker());
+            }
+        }
+
+        this.active[mapId] = true;
+        return this.workers.slice();
     },
 
     release: function (mapId) {
         delete this.active[mapId];
         if (Object.keys(this.active).length === 0) {
             this.workers.forEach(function (w) { w.terminate(); });
-            this.workers = [];
-        }
-    },
-
-    _resize: function (len) {
-        assert(typeof len === 'number');
-        while (this.workers.length < len) {
-            this.workers.push(new WebWorker());
+            this.workers = null;
         }
     }
 };

test/js/style/style.test.js

@@ -1232,10 +1232,3 @@ test('Style#addSourceType', function (t) {
 
     t.end();
 });
-
-test('Style creates correct number of workers', function(t) {
-    var style = new Style(createStyleJSON(), null, 3);
-    t.equal(style.dispatcher.actors.length, 3);
-    t.ok(style);
-    t.end();
-});

test/js/ui/map.test.js

@@ -993,17 +993,6 @@ test('Map', function(t) {
         t.end();
     });
 
-    t.test('workerCount option', function(t) {
-        var map = createMap({ style: createStyle() });
-        t.equal(map.style.dispatcher.actors.length, browser.hardwareConcurrency - 1, 'workerCount defaults to hardwareConcurrency - 1');
-        map = createMap({ style: createStyle(), workerCount: 3 });
-        t.equal(map.style.dispatcher.actors.length, 3, 'workerCount option is used');
-        t.throws(function () {
-            createMap({ workerCount: 0 });
-        });
-        t.end();
-    });
-
     t.end();
 });
 

test/js/util/dispatcher.test.js

@@ -13,16 +13,15 @@ test('Dispatcher', function (t) {
 
         var releaseCalled = [];
         var workerPool = {
-            acquire: function (id, count) {
-                t.equal(count, 2);
+            acquire: function () {
                 return workers;
             },
             release: function (id) {
                 releaseCalled.push(id);
             }
         };
 
-        dispatcher = new Dispatcher(workerPool, 2, {});
+        dispatcher = new Dispatcher(workerPool, {});
         t.same(dispatcher.actors.map(function (actor) { return actor.target; }), workers);
         dispatcher.remove();
         t.equal(dispatcher.actors.length, 0, 'actors discarded');
@@ -37,10 +36,14 @@ test('Dispatcher', function (t) {
         var ids = [];
         function Actor (target, parent, mapId) { ids.push(mapId); }
 
+        var previousWorkerCount = WorkerPool.WORKER_COUNT;
+        WorkerPool.WORKER_COUNT = 1;
+
         var workerPool = new WorkerPool();
-        var dispatchers = [new Dispatcher(workerPool, 1, {}), new Dispatcher(workerPool, 1, {})];
+        var dispatchers = [new Dispatcher(workerPool, {}), new Dispatcher(workerPool, {})];
         t.same(ids, dispatchers.map(function (d) { return d.id; }));
 
+        WorkerPool.WORKER_COUNT = previousWorkerCount;
         t.end();
     });
 

test/js/util/worker_pool.test.js

@@ -1,19 +1,31 @@
 'use strict';
 
 var test = require('tap').test;
+var proxyquire = require('proxyquire');
 var WorkerPool = require('../../../js/util/worker_pool');
 
 test('WorkerPool', function (t) {
+    t.test('.WORKER_COUNT', function (t) {
+        var WorkerPool = proxyquire('../../../js/util/worker_pool', {
+            './browser': { hardwareConcurrency: 15 }
+        });
+        t.equal(WorkerPool.WORKER_COUNT, 14);
+
+        WorkerPool.WORKER_COUNT = 4;
+        t.end();
+    });
+
     t.test('#acquire', function (t) {
-        var pool = new WorkerPool();
+        // make sure we're actually creating some workers
+        t.ok(WorkerPool.WORKER_COUNT > 0);
 
-        t.equal(pool.workers.length, 0);
-        var workers1 = pool.acquire('map-1', 4);
-        t.equal(workers1.length, 4);
+        var pool = new WorkerPool();
 
-        var workers2 = pool.acquire('map-2', 8);
-        t.equal(workers2.length, 8);
-        t.equal(pool.workers.length, 8);
+        t.notOk(pool.workers);
+        var workers1 = pool.acquire('map-1');
+        var workers2 = pool.acquire('map-2');
+        t.equal(workers1.length, WorkerPool.WORKER_COUNT);
+        t.equal(workers2.length, WorkerPool.WORKER_COUNT);
 
         // check that the two different dispatchers' workers arrays correspond
         workers1.forEach(function (w, i) { t.equal(w, workers2[i]); });
@@ -22,8 +34,8 @@ test('WorkerPool', function (t) {
 
     t.test('#release', function (t) {
         var pool = new WorkerPool();
-        pool.acquire('map-1', 1);
-        var workers = pool.acquire('map-2', 4);
+        pool.acquire('map-1');
+        var workers = pool.acquire('map-2');
         var terminated = 0;
         workers.forEach(function (w) {
             w.terminate = function () { terminated += 1; };
@@ -32,12 +44,12 @@ test('WorkerPool', function (t) {
         pool.release('map-2');
         t.comment('keeps workers if a dispatcher is still active');
         t.equal(terminated, 0);
-        t.equal(pool.workers.length, 4);
+        t.ok(pool.workers.length > 0);
 
         t.comment('terminates workers if no dispatchers are active');
         pool.release('map-1');
-        t.equal(terminated, 4);
-        t.equal(pool.workers.length, 0);
+        t.equal(terminated, WorkerPool.WORKER_COUNT);
+        t.notOk(pool.workers);
 
         t.end();
     });