link: Real-Time Notification Architectures

Server-Sent Events

Diagram

Overview

Server-Sent Events (SSE) is a web technology that enables servers to push real-time updates to clients over a single, long-lived HTTP connection. SSE is part of the HTML5 specification and provides a simple, efficient way to send continuous data streams from the server to the browser.

How SSE Works

SSE works by establishing a persistent HTTP connection from the client to the server. The server can then send updates to the client whenever new data is available. Here’s a typical flow:

1. Client Request: The client initiates an HTTP request to the server to start receiving events.
2. Server Response: The server keeps the connection open and sends updates as they become available, using a specific format for event data.
3. Client Handling: The client processes the incoming events and updates the UI or performs other actions accordingly.

Pros/Cons

Pros

• Simplicity: Easy to implement using standard HTTP and JavaScript.
• Efficiency: Maintains a single connection for multiple updates, reducing overhead.
• Compatibility: Well-supported by modern browsers without the need for additional libraries or plugins.

Cons

• Limited Bidirectionality: Only allows server-to-client communication; client-to-server interactions require additional mechanisms like AJAX.
• Connection Limits: Browsers typically limit the number of open SSE connections per domain.
• Less Control Over Reconnection: Automatic reconnection is handled by the browser, offering less control over reconnection logic compared to WebSockets.

Use Cases

SSE is ideal for applications that require continuous updates from the server to the client without the complexity of WebSockets. Examples include:

• Live Feeds: Streaming news updates, social media feeds, or stock market tickers.
• Notifications: Sending real-time alerts or notifications to users.
• Monitoring Dashboards: Displaying live updates in monitoring or analytics dashboards.

Summary

Server-Sent Events provide a straightforward method for pushing real-time updates from the server to the client. While they offer simplicity and efficiency for server-to-client communication, they are best suited for scenarios where unidirectional data flow is sufficient. For bidirectional communication needs, alternatives like WebSockets might be more appropriate.