Scaling WebSockets Horizontally: A Simple Guide for Beginners
Introduction
WebSockets have become a vital technology for real-time communication in modern web applications. Scaling WebSockets horizontally, i.e., across multiple servers, is essential to ensure your system can handle increasing loads and maintain responsiveness. In this article, we will explore how to achieve basic horizontal scalability for WebSockets, breaking it down into easy-to-understand steps even for beginners.
Understanding WebSockets
Before we dive into horizontal scaling, let’s clarify what WebSockets are. WebSockets provide full-duplex communication channels over a single TCP connection, allowing real-time data exchange between a client (e.g., a web browser) and a server. They are commonly used for chat applications, online gaming, collaborative tools, and live notifications.
The Challenge of Scaling
As your application grows, a single WebSocket server may not be sufficient to handle the increasing number of connections and messages. To address this challenge, we can distribute the WebSocket connections across multiple servers.
Horizontal Scaling
Horizontal scaling, also known as scaling out, involves adding more servers to your system to distribute the load. In the context of WebSockets, we can scale horizontally by creating a WebSocket cluster with multiple servers. Each server in the cluster is responsible for handling a portion of the WebSocket connections.
Here are the key steps to scale WebSockets horizontally:
Load Balancer
Implement a load balancer that distributes incoming WebSocket connection requests evenly among the WebSocket servers. A load balancer acts as a traffic cop, ensuring that each server receives a fair share of connections.
WebSocket Servers:
Set up multiple WebSocket servers in your cluster. These servers handle the actual WebSocket connections and communication with clients.
Client Connections
Clients (e.g., web browsers) connect to your application through the load balancer. The load balancer forwards WebSocket connection requests to one of the WebSocket servers in the cluster.
Shared State
As we are using multiple WebSocket servers, we can use a common data store like a message queue. This allows WebSocket servers in the cluster to share information, such as user presence or chat history.
In the following example, we can see 4 apps are connected to 3 different WebSocket servers. If App1 sends the information WebSocket Server 1 will send the information to Redis. Then redis will broadcast the information to all the servers. And those servers will forward the information to their respective connections.
Conclusion
Scaling WebSockets horizontally is a crucial step in ensuring your real-time web application remains responsive and reliable as it grows. By following the basic steps outlined in this article, you can achieve horizontal scalability while keeping your system straightforward and efficient.
Remember that horizontal scaling is not a one-size-fits-all solution, and the specific implementation may vary based on your application’s requirements. However, this guide should give you a simple foundation to get started on your journey to building scalable WebSocket-based systems.
