Server-Sent Events (SSE) is a simple, one-way communication channel between a client and a server, allowing the server to push updates to the client in real-time. This technology is particularly useful for applications that require live updates, such as stock tickers, sports scores, or live chat systems.
SSE Nextjs provides a convenient way to handle SSE in Nextjs applications, making it easy to implement real-time data streaming. By using the built-in SSE support in Nextjs, developers can create seamless and efficient real-time experiences for their users.
With SSE Nextjs, you can create event streams that are automatically managed by the server, eliminating the need for manual event handling. This means you can focus on building the core functionality of your application, without worrying about the underlying infrastructure.
Setting up Next.js for Server-Sent Events
To set up Next.js for Server-Sent Events, you need to create a file named route.ts in the app/api/stream directory. The dynamic constant is set to force-dynamic, preventing caching of responses on the Vercel platform.
A ReadableStream is created to generate a stream of data to be sent to the client. In the start method of the stream, a message is encoded and enqueued into the stream's controller.
To stream Completion and Chat Completion API responses from OpenAI with LangChain callbacks, you'll need to create a file named route.ts in the app/api/stream/completion directory. The changes from the initial streaming route handler are highlighted below.
A minimal listener to Server-Sent Events API messages can be set up in the Next.js frontend. This involves subscribing to the SSE's in the React client code.
The default Next.js server compresses everything by default, which can cause issues with Server-Sent Events. To fix this, you need to add the Cache-Control header with the value "no-cache, no-transform" to the API response.
Here are some key points to keep in mind when setting up Next.js for Server-Sent Events:
- Create a file named route.ts in the app/api/stream directory to set up the Server-Sent Events API.
- Use the Cache-Control header with the value "no-cache, no-transform" to prevent compression issues.
- Create a file named route.ts in the app/api/stream/completion directory to stream Completion and Chat Completion API responses from OpenAI with LangChain callbacks.
By following these steps and using the highlighted changes from the initial streaming route handler, you can successfully set up Next.js for Server-Sent Events.
Implementing SSE in React
To implement Server-Sent Events (SSE) in React, you need to initiate a POST request to the specified API route. Upon receiving a response, you would decode the incoming data as a string using TextDecoderStream method, and continuously read the data from stream.
The SSE API in Next.js app router allows you to deliver real-time data updates from the server to the client without the need for continuous polling. This enables a unidirectional flow of data over a single, long-lived HTTP connection.
To manage the state of the conversation between the user and chatbot, you can use state variables. You would update the state variables messages and latestMessage to store the conversation history and the latest message, respectively.
Here are the key steps to manage the state of the conversation:
- Declare a state variable to store the incoming data stream received from the SSE API.
- Upon receiving a complete message, add the latest received message to the messages state array and reset the latest message state to an empty string.
- As data is received incrementally, append it to the incomingMessage variable and update the latest message state with the concatenated incoming data.
By following these steps, you can ensure real-time updates of the conversation display and create dynamic user interfaces representing the messages exchanged in the conversation and the latest AI generated response.
In the React client code, you can subscribe to the SSE's like this: `eventSource.addEventListener('message', event => { console.log(event.data); });`. However, the connection always stays open on the Next.js API, and it's not easy to close it by detecting client disconnect.
Deploying and Utilities
To deploy your Next.js app, start by creating a GitHub repository containing your app's code. This is the foundation for hosting your app on Vercel.
You can then navigate to the Vercel Dashboard and create a New Project. This is where you'll link your GitHub repository to Vercel.
To link your repository, select the GitHub option and authenticate with your GitHub account. Once authenticated, you can select the repository you created earlier.
Here's a step-by-step guide to linking your repository to Vercel:
- Create a GitHub repository containing your app's code.
- Navigate to the Vercel Dashboard and create a New Project.
- Link the new project to the GitHub repository you have just created.
After linking your repository, you can update the Environment Variables in Vercel to match those in your local .env file. This ensures your app is configured correctly on Vercel.
Deploy to Vercel
To deploy your app to Vercel, start by creating a GitHub repository containing your app's code. This is the foundation for your deployment process.
Next, navigate to the Vercel Dashboard and create a New Project. This will allow you to link your project to your GitHub repository.
You'll then need to link the new project to the GitHub repository you've just created. This is a crucial step in setting up your deployment process.
In Settings, update the Environment Variables to match those in your local .env file. This ensures that your app has the necessary settings to run smoothly on Vercel.
Here's a step-by-step guide to deploying to Vercel:
- Start by creating a GitHub repository containing your app's code.
- Navigate to the Vercel Dashboard and create a New Project.
- Link the new project to the GitHub repository you have just created.
- Update the Environment Variables to match those in your local .env file.
- Finally, deploy your app!
OpenAI Stream Utility
The OpenAI Stream Utility is a crucial component in our deployment process, enabling us to efficiently handle real-time data from OpenAI's API.
We created the OpenAIStream utility to facilitate this, which is responsible for creating a readable stream that transforms the streamed data for easy consumption by the front-end.
The OpenAIStream utility specifically uses the eventsource-parser library to properly parse the Server-Sent Events (SSE) stream response from OpenAI.
This library is essential for handling the SSE stream response, making it possible for us to process the data in a seamless and efficient manner.
By utilizing the eventsource-parser library, we can ensure that the streamed data is properly formatted and ready for consumption by our front-end application.
Managing Conversation State in React
Managing conversation state in React can be a challenge, especially when dealing with real-time updates like those provided by Server-Sent Events (SSE) in Next.js.
To capture user input, we need to send it to the server via a POST request, as shown in the front-end implementation example.
This is where a robust state management system comes into play, allowing us to keep track of user input and update the conversation state in real-time.
We can use the Next.js front-end implementation to capture user input, send it to the server, and display the streaming response in real-time, just like in the example code.
By doing so, we can ensure that our conversation state is always up-to-date and reflect the latest user input.
In the example code, we see that the streaming response is displayed in real-time, which is essential for a seamless user experience.
Sources
- https://nextjs.org/docs/app/building-your-application/data-fetching/server-actions-and-mutations
- https://stackoverflow.com/questions/74408942/how-to-forward-server-sent-events-in-nextjs-api
- https://docs.amplify.aws/react/build-a-backend/server-side-rendering/
- https://upstash.com/blog/sse-streaming-llm-responses
- https://mubin.io/streaming-real-time-openai-data-in-nextjs-a-practical-guide
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