[FIX] RocketChat.settings.get causing memory leak (sometimes) (#11487)

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packages/rocketchat-lib/server/functions/checkUsernameAvailability.js

@@ -1,23 +1,26 @@
-import _ from 'underscore';
 import s from 'underscore.string';
 
+
+let usernameBlackList = [];
+
+const toRegExp = username => new RegExp(`^${ s.escapeRegExp(username).trim() }$`, 'i');
+
+RocketChat.settings.get('Accounts_BlockedUsernameList', (key, value) => {
+	usernameBlackList = value.split(',').map(toRegExp);
+});
+
+const usernameIsBlocked = (username, usernameBlackList) => usernameBlackList.length
+	&& usernameBlackList.some(restrictedUsername => restrictedUsername.test(s.trim(s.escapeRegExp(username))));
+
 RocketChat.checkUsernameAvailability = function(username) {
-	return RocketChat.settings.get('Accounts_BlockedUsernameList', function(key, value) {
-		const usernameBlackList = _.map(value.split(','), function(username) {
-			return username.trim();
-		});
-		if (usernameBlackList.length !== 0) {
-			if (usernameBlackList.every(restrictedUsername => {
-				const regex = new RegExp(`^${ s.escapeRegExp(restrictedUsername) }$`, 'i');
-				return !regex.test(s.trim(s.escapeRegExp(username)));
-			})) {
-				return !Meteor.users.findOne({
-					username: {
-						$regex: new RegExp(`^${ s.trim(s.escapeRegExp(username)) }$`, 'i')
-					}
-				});
-			}
-			return false;
+
+	if (usernameIsBlocked(username, usernameBlackList)) {
+		return false;
+	}
+
+	return !Meteor.users.findOne({
+		username: {
+			$regex: toRegExp(username)
 		}
-	});
+	}, { fields: { _id: 1 } });
 };

packages/rocketchat-livechat/imports/server/rest/upload.js

@@ -1,6 +1,14 @@
 import Busboy from 'busboy';
 import filesize from 'filesize';
 import LivechatVisitors from '../../../server/models/LivechatVisitors';
+let maxFileSize;
+RocketChat.settings.get('FileUpload_MaxFileSize', function(key, value) {
+	try {
+		maxFileSize = parseInt(value);
+	} catch (e) {
+		maxFileSize = RocketChat.models.Settings.findOneById('FileUpload_MaxFileSize').packageValue;
+	}
+});
 
 RocketChat.API.v1.addRoute('livechat/upload/:rid', {
 	post() {
@@ -61,14 +69,6 @@ RocketChat.API.v1.addRoute('livechat/upload/:rid', {
 			});
 		}
 
-		const maxFileSize = RocketChat.settings.get('FileUpload_MaxFileSize', function(key, value) {
-			try {
-				return parseInt(value);
-			} catch (e) {
-				return RocketChat.models.Settings.findOneById('FileUpload_MaxFileSize').packageValue;
-			}
-		});
-
 		// -1 maxFileSize means there is no limit
 		if (maxFileSize >= -1 && file.fileBuffer.length > maxFileSize) {
 			return RocketChat.API.v1.failure({