fix: update online example to support Redis v4+ and remove outdated dependency

examples/online/index.js

@@ -4,15 +4,15 @@
 // https://redis.io/
 
 // then:
-// $ npm install redis online
+// $ npm install redis
 // $ redis-server
 
 /**
  * Module dependencies.
  */
 
 var express = require('../..');
-var online = require('online');
+var online = require('./online-tracker');
 var redis = require('redis');
 var db = redis.createClient();
 
@@ -27,9 +27,13 @@ var app = express();
 // activity tracking, in this case using
 // the UA string, you would use req.user.id etc
 
-app.use(function(req, res, next){
-  // fire-and-forget
-  online.add(req.headers['user-agent']);
+app.use(async (req, res, next) => {
+  try {
+    // fire-and-forget
+    await online.add(req.headers['user-agent']);
+  } catch (err) {
+    next(err);
+  }
   next();
 });
 
@@ -47,15 +51,37 @@ function list(ids) {
  * GET users online.
  */
 
-app.get('/', function(req, res, next){
-  online.last(5, function(err, ids){
-    if (err) return next(err);
-    res.send('<p>Users online: ' + ids.length + '</p>' + list(ids));
-  });
+app.get('/', async (req, res, next) => {
+  try {
+      const activeUsers = await online.last(5);
+      res.send('<p>Users online:' + activeUsers.length + '</p>' + list(activeUsers));
+    } catch (err) {
+      next(err);
+  }
 });
 
-/* istanbul ignore next */
-if (!module.parent) {
-  app.listen(3000);
-  console.log('Express started on port 3000');
+
+/**
+ * Redis Initialization
+ */
+async function initializeRedis() {
+  try {
+    // Connect to Redis
+    await db.connect();
+  } catch (err) {
+    console.error('Error initializing Redis:', err);
+    process.exit(1);
+  }
 }
+
+/**
+ * Start the Server
+ */
+
+(async () => {
+  await initializeRedis(); // Initialize Redis before starting the server
+  if (!module.parent) {
+    app.listen(3000);
+    console.log('Express started on port 3000');
+  }
+})();

examples/online/online-tracker.js

@@ -0,0 +1,44 @@
+'use strict';
+
+const { createClient } = require('redis');
+
+/**
+ * Factory function to create an OnlineTracker instance
+ *
+ * @param {Object} redisClient - The Redis client instance.
+ * @returns {Object} An object with methods for user activity tracking.
+ */
+
+function createOnlineTracker(redisClient) {
+  // Method to add a user's activity
+  async function add(user) {
+    const now = Date.now();
+    try {
+      await redisClient.hSet('online_users', user, now.toString());
+    } catch (err) {
+      console.error('Error setting user activity:', err);
+    }
+  }
+
+  // Method to get the list of users active in the last N minutes
+  async function last(minutes) {
+    const threshold = Date.now() - minutes * 60 * 1000;
+    try {
+      const users = await redisClient.hGetAll('online_users');
+      return Object.entries(users || {}).filter(([_, lastActive]) => {
+        return parseInt(lastActive, 10) >= threshold;
+      }).map(([id]) => id);
+    } catch (err) {
+      console.error('Error retrieving active users:', err);
+      throw err;
+    }
+  }
+
+  return {
+    add,
+    last,
+  };
+}
+
+// Export the factory function
+module.exports = createOnlineTracker;