fix: dedupe events

Author: TobiTenno

package-lock.json

@@ -40,9 +40,8 @@
     "@types/form-data": "^2.5.0",
     "@types/request": "^2.48.4",
     "chai": "3.4.0",
-    "eslint": "^6.8.0",
+    "eslint": "^7.20.0",
     "eslint-config-airbnb-base": "^14.1.0",
-    "eslint-plugin-babel": "^5.3.0",
     "eslint-plugin-import": "^2.20.2",
     "mocha": "^7.2.0",
     "nock": "11.7.2",
@@ -125,6 +124,7 @@
     "slow": 1000,
     "normal": 400,
     "retries": 4,
-    "reporter": "min"
+    "reporter": "min",
+    "timeout": 5000
   }
 }

package.json

@@ -91,6 +91,12 @@ class Feed {
      */
     this.maxHistoryLength; // eslint-disable-line no-unused-expressions
 
+    /**
+     * Track first load failing so skipFirstLoad can be honored on the first passing load
+     * @type {Boolean}
+     */
+    this.failedFirstLoad = true;
+
     ({
       items: this.items, url: this.url, refresh: this.refresh, userAgent: this.userAgent,
       eventName: this.eventName,
@@ -185,7 +191,9 @@ class Feed {
       })
       .on('response', (res) => {
         if (res.statusCode !== RESPONSE_CODES.OK) {
-          this.handleError(new FeedError(`This URL returned a ${res.statusCode} status code`, 'fetch_url_error', this.url));
+          const err = new FeedError(`This URL returned a ${res.statusCode} status code`, 'fetch_url_error', this.url);
+          Error.captureStackTrace(err);
+          this.handleError(err);
         }
       })
       .on('error', () => {

src/Feed.js

@@ -94,8 +94,15 @@ class FeedEmitter extends EventEmitter {
      * @type {boolean}
      */
     this.skipFirstLoad = options.skipFirstLoad;
-  }
 
+    /**
+     * Map of emitted event urls grouped by event.
+     * This is to help prevent overlapping/dupe events in a single event name
+     * Each entry set clears at the same interval as the most recently applied feed.
+     * @type {Object}
+     */
+    this.emittedUrlsPerEvent = {};
+  }
 
   /**
    * UserFeedConfig typedef
@@ -194,6 +201,14 @@ class FeedEmitter extends EventEmitter {
       this.removeFromFeedList(feedInList);
     }
 
+    if (!this.emittedUrlsPerEvent[feed.eventName]) {
+      this.emittedUrlsPerEvent[feed.eventName] = {
+        timeout: setTimeout(() => {
+          this.emittedUrlsPerEvent[feed.eventName].urls = [];
+        }, feed.refresh),
+        urls: [],
+      };
+    }
     this.addToFeedList(feed);
   }
 
@@ -231,6 +246,7 @@ class FeedEmitter extends EventEmitter {
   createSetInterval(feed) {
     const feedManager = new FeedManager(this, feed);
     feedManager.getContent(true);
+
     return setInterval(feedManager.getContent.bind(feedManager), feed.refresh);
   }
 
@@ -248,6 +264,28 @@ class FeedEmitter extends EventEmitter {
     const pos = this.feedList.findIndex((e) => e.url === feed.url);
     this.feedList.splice(pos, 1);
   }
+
+  /**
+   * Override emit to check if emitted event has already
+   *  been emitted on the same event
+   *  **WARNING:** This is a very limited scope implementation
+   *     If we ever need to emit more than one thing at once, we should expand this
+   * @param  {string} event event name to emit
+   * @param  {Object} data  event data/args
+   * @returns {boolean}       [description]
+   */
+  emit(event, data) {
+    // should only get triggered by initial-load, which we don't want to muck up memory with
+    if (!this.emittedUrlsPerEvent[event]) {
+      return super.emit(event, data);
+    }
+
+    if (this.emittedUrlsPerEvent[event].urls.includes(data.link)) {
+      return false;
+    }
+    this.emittedUrlsPerEvent[event].urls.push(data.link);
+    return super.emit(event, data);
+  }
 }
 
 module.exports = FeedEmitter;

src/FeedEmitter.js

@@ -84,7 +84,7 @@ class FeedManager {
   populateNewItemsInFeed(data, firstload) {
     data.newItems.forEach((item) => {
       this.feed.addItem(item);
-      if (!(firstload && this.instance.skipFirstLoad)) {
+      if ((firstload && !this.instance.skipFirstLoad) || !firstload) {
         this.instance.emit(this.feed.eventName, item);
       }
     });
@@ -96,6 +96,7 @@ class FeedManager {
    * @param  {FeedError} error handle error
    */
   onError(error) {
+    console.error(error.stack);
     this.instance.emit('error', error);
   }
 
@@ -114,9 +115,13 @@ class FeedManager {
     this.feed.updateHxLength(items);
     this.sortItemsByDate(data);
     this.identifyNewItems(data);
-    this.populateNewItemsInFeed(data, firstload);
+
+    const innerFirst = firstload || (!firstload && this.feed.failedFirstLoad);
+
+    this.populateNewItemsInFeed(data, innerFirst);
     if (firstload && !this.instance.skipFirstLoad) {
       this.instance.emit(`initial-load:${this.feed.url}`, { url: this.feed.url, items: this.feed.items });
+      this.feed.failedFirstLoad = false;
     }
   }
 }