feat(stats): Add the ability to enable callStats only on a certain % of conferences

JitsiConference.js

 import Statistics from './modules/statistics/statistics';
 import Transcriber from './modules/transcription/transcriber';
 import GlobalOnErrorHandler from './modules/util/GlobalOnErrorHandler';
+import { hashString } from './modules/util/MathUtil';
 import RandomUtil from './modules/util/RandomUtil';
 import ComponentsVersions from './modules/version/ComponentsVersions';
 import VideoSIPGW from './modules/videosipgw/VideoSIPGW';
             });
     this.participantConnectionStatus.init();
 
+    // Add the ability to enable callStats only on a percentage of conferences based on config.js settings.
+    let enableCallStats = true;
+
+    if (config.testing && config.testing.callStatsThreshold) {
+        enableCallStats = (hashString(this.options.name) % 100) < config.testing.callStatsThreshold;
+    }
+
     if (!this.statistics) {
         this.statistics = new Statistics(this.xmpp, {
             aliasName: this._statsCurrentId,
             callStatsID: config.callStatsID,
             callStatsSecret: config.callStatsSecret,
             callStatsApplicationLogsDisabled: config.callStatsApplicationLogsDisabled,
+            enableCallStats,
             roomName: this.options.name,
             applicationName: config.applicationName,
             getWiFiStatsMethod: config.getWiFiStatsMethod

modules/statistics/statistics.js

     this.options = options || {};
 
     this.callStatsIntegrationEnabled
-        = this.options.callStatsID && this.options.callStatsSecret
+        = this.options.callStatsID && this.options.callStatsSecret && this.options.enableCallStats
 
             // Even though AppID and AppSecret may be specified, the integration
             // of callstats.io may be disabled because of globally-disallowed

modules/util/MathUtil.js

     return valueArray.length > 0 ? valueArray.reduce((a, b) => a + b) / valueArray.length : 0;
 }
 
+/**
+ * Calculates a unique hash for a given string similar to Java's
+ * implementation of String.hashCode()
+ *
+ * @param {String} string - String whose hash has to be calculated.
+ * @returns {number} - Unique hash code calculated.
+ */
+export function hashString(string) {
+    let hash = 0;
+
+    for (let i = 0; i < string.length; i++) {
+        hash += Math.pow(string.charCodeAt(i) * 31, string.length - i);
+
+        /* eslint-disable no-bitwise */
+        hash = hash & hash; // Convert to 32bit integer
+    }
+
+    return Math.abs(hash);
+}
 
 /**
  * Returns only the positive values from an array of numbers.