Server-Sent Events (SSE) | NextJS & FastApi

Step-by-Step Tutorial: Implementing Server-Sent Events (SSE) using NextJS & FastAPI

Overview:

In this tutorial, we will implement Server-Sent Events (SSE) to establish communication between the front end (NextJS) and the back end (FastAPI) applications. SSE allows the server to push updates to the client over a single, long-lived connection.

Step 1: Understanding Frontend-Backend Communication

• When a website is opened in a browser, the front end makes an API call to the backend to fetch data.
• The backend responds with data that the front end renders on the page.
• This communication uses the HTTP protocol with requests and responses.

Step 2: Setting Up the Backend (FastAPI)

1. Create a new folder for the backend.
2. Inside the backend folder, create a requirements.txt file with necessary imports like FastAPI and uvicorn.
3. Set up a FastAPI application and configure CORS middleware to allow connections from the front end.
4. Create an endpoint to add events and a streaming endpoint to stream events to the front end using SSE.

Step 3: Implementing Backend Logic

1. Define an Event model to store event data.
2. Use a deque to store events in a queue.
3. Implement methods to add events, get events, and count events.
4. Create an API endpoint to add new events and a streaming endpoint to stream events to the front end.

Step 4: Setting Up the Frontend (NextJS)

1. Create a new folder for the frontend.
2. Set up the NextJS application.
3. Create a client component to handle SSE connections.
4. Use useEffect to establish a connection to the backend and listen for incoming events.
5. Parse the received JSON data and display it on the frontend.

Step 5: Displaying Events on the Frontend

1. Style the displayed events using CSS classes based on the event type (success, error, warning, default).
2. Update the frontend to show different colored alerts based on the event type.
3. Test the SSE implementation by sending events from the backend and observing them being displayed on the frontend.

Step 6: Testing and Finalizing

1. Test the SSE implementation by sending different types of events from the backend.
2. Ensure that events are displayed correctly on the frontend with appropriate styling.
3. Make any necessary adjustments to the backend or frontend code for seamless communication.
4. Once everything works as expected, finalize the implementation and consider deploying the application.

By following these steps, you can successfully implement Server-Sent Events (SSE) using NextJS and FastAPI for real-time communication between your frontend and backend applications.