Improved JSDoc and comments for URL service Queue class

- no implementation changes, just improving the JSDoc and comments to
  make this more readable
- also switches some assertions in the tests to use the spy instance to
  fix a typing issue

ghost/core/core/server/services/url/Queue.js

@@ -7,28 +7,26 @@ const errors = require('@tryghost/errors');
 /**
  * ### Purpose of this queue
  *
- * Ghost fetches as earliest as possible the resources from the database. The reason is simply: we
- * want to know all urls as soon as possible.
+ * Ghost fetches the resources as early as possible from the database. The simple reason is: we
+ * want to know all URLs as soon as possible.
  *
- * Parallel to this, the routes are read/prepared and registered in express.
- * So the challenge is to handle both resource availability and route registration.
- * If you start an event, all subscribers of it are executed in a sequence. The queue will wait
- * till the current subscriber has finished it's work.
- * The url service must ensure that each url in the system exists once. The order of
- * subscribers defines who will possibly own an url first.
+ * Parallel to this, the routes are read/prepared and registered in express. So the challenge is
+ * to handle both resource availability and route registration. If you start an event, all subscribers
+ * of it are executed in a sequence. The queue will wait until the current subscriber has finished its work.
  *
- * If an event has finished, the subscribers of this event still remain in the queue.
- * That means:
+ * The URL service must ensure that each URL in the system exists only once. The order of
+ * subscribers defines who will possibly own an URL first.
  *
- * - you can re-run an event
- * - you can add more subscribers to an existing queue
- * - you can order subscribers (helpful if you want to order routers)
+ * If an event has finished, the subscribers of this event still remain in the queue. That means:
+ *  - you can re-run an event
+ *  - you can add more subscribers to an existing queue
+ *  - you can order subscribers (helpful if you want to order routers)
  *
- * Each subscriber represents one instance of the url generator. One url generator represents one router.
+ * Each subscriber represents one instance of the URL generator. One URL generator represents one router.
  *
  * ### Tolerance option
  *
- * You can define a tolerance value per event. If you want to wait an amount of time till you think
+ * You can define a `tolerance` value per event. This allows you to wait an amount of time until you think
  * all subscribers have registered.
  *
  * ### Some examples to understand cases
@@ -63,21 +61,26 @@ const errors = require('@tryghost/errors');
  *   - makes use of `toNotify` to remember who was notified already
  */
 class Queue extends EventEmitter {
-    constructor() {
-        super();
-        this.queue = {};
-        this.toNotify = {};
-    }
+    /** @type {Record<string, {tolerance: number, requiredSubscriberCount: number, subscribers: Array<Function>}>} */
+    queue = {};
+
+    /** @type {Record<string, {event: string, timeoutInMS: number, notified: Array<Function>, timeout?: NodeJS.Timeout | null}>} */
+    toNotify = {};
 
     /**
      * @description Register a subscriber for this queue.
      *
-     * tolerance:
+     * Also initializes the queue for this event if it hasn't already.
+     *
+     * The tolerance is for the event on the queue (milliseconds):
      *   - 0: don't wait for more subscribers [default]
      *   - 100: wait long enough till all subscribers have registered (e.g. bootstrap)
      *
      * @param {Object} options
-     * @param {function} fn
+     * @param {string} options.event
+     * @param {number} [options.tolerance]
+     * @param {number} [options.requiredSubscriberCount]
+     * @param {Function} fn
      */
     register(options, fn) {
         if (!Object.prototype.hasOwnProperty.call(options, 'tolerance')) {
@@ -101,6 +104,9 @@ class Queue extends EventEmitter {
     /**
      * @description The queue runs & executes subscribers one by one (sequentially)
      * @param {Object} options
+     * @param {string} options.event
+     * @param {string} options.action
+     * @param {Object} [options.eventData]
      */
     run(options) {
         const {event, action, eventData} = options;
@@ -145,12 +151,12 @@ class Queue extends EventEmitter {
             // CASE 3: wait for more subscribers, i am still tolerant
             if (this.queue[event].tolerance === 0) {
                 delete this.toNotify[action];
-                debug('run.ended (1)', event, action);
+                debug('run.ended (zero tolerance)', event, action);
                 this.emit('ended', event);
             } else if (subscribers.length >= this.queue[event].requiredSubscriberCount &&
                 this.toNotify[action].timeoutInMS > this.queue[event].tolerance) {
                 delete this.toNotify[action];
-                debug('run.ended (2)', event, action);
+                debug('run.ended (tolerance and subscribers)', event, action);
                 this.emit('ended', event);
             } else {
                 debug('run.retry', event, action, this.toNotify[action].timeoutInMS);
@@ -168,11 +174,15 @@ class Queue extends EventEmitter {
      * @description Start the queue from outside.
      *
      * CASE:
-     *
      *   - resources were fetched from database on bootstrap
      *   - resource was added
      *
-     * @param options
+     * @param {Object} options
+     * @param {string} options.event
+     * @param {number} [options.tolerance]
+     * @param {number} [options.timeoutInMS]
+     * @param {number} [options.requiredSubscriberCount]
+     * @param {string} [options.action]
      */
     start(options) {
         debug('start');

ghost/core/test/unit/server/services/url/Queue.test.js

@@ -5,12 +5,16 @@ const logging = require('@tryghost/logging');
 const Queue = require('../../../../../core/server/services/url/Queue');
 
 describe('Unit: services/url/Queue', function () {
+    /** @type {Queue} */
     let queue;
 
+    /** @type {sinon.SinonSpy} */
+    let queueRunSpy;
+
     beforeEach(function () {
         queue = new Queue();
 
-        sinon.spy(queue, 'run');
+        queueRunSpy = sinon.spy(queue, 'run');
         sinon.stub(logging, 'error');
     });
 
@@ -50,7 +54,7 @@ describe('Unit: services/url/Queue', function () {
         it('no subscribers', function (done) {
             queue.addListener('ended', function (event) {
                 event.should.eql('nachos');
-                queue.run.callCount.should.eql(1);
+                queueRunSpy.callCount.should.eql(1);
                 done();
             });
 
@@ -64,7 +68,7 @@ describe('Unit: services/url/Queue', function () {
 
             queue.addListener('ended', function (event) {
                 event.should.eql('nachos');
-                queue.run.callCount.should.eql(2);
+                queueRunSpy.callCount.should.eql(2);
                 notified.should.eql(1);
                 done();
             });
@@ -88,7 +92,7 @@ describe('Unit: services/url/Queue', function () {
                 event.should.eql('nachos');
 
                 // 9 subscribers + start triggers run
-                queue.run.callCount.should.eql(10);
+                queueRunSpy.callCount.should.eql(10);
                 notified.should.eql(9);
                 order.should.eql([0, 1, 2, 3, 4, 5, 6, 7, 8]);
                 done();
@@ -113,7 +117,7 @@ describe('Unit: services/url/Queue', function () {
 
             queue.addListener('ended', function (event) {
                 event.should.eql('nachos');
-                queue.run.callCount.should.eql(1);
+                queueRunSpy.callCount.should.eql(1);
                 notified.should.eql(0);
                 done();
             });
@@ -244,7 +248,6 @@ describe('Unit: services/url/Queue', function () {
                 queue.register({
                     event: 'nachos',
                     tolerance: 100,
-                    timeoutInMS: 20,
                     requiredSubscriberCount: 1
                 }, function () {
                     called = called + 1;