Implementing asynchronous Server-Sent Events (SSE)

SSE is a server push mechanism that sends data to the browser without reloading the page. Once subscribed, it generates event-driven streams in real time for various purposes.

Creating SSE in the FastAPI framework only requires the following:

• The EventSourceResponse class from the sse_starlette.see module
• An event generator

Above all, the framework also allows non-blocking implementation of the whole server push mechanism using coroutines that can run even on HTTP/2. The following is a coroutine API service that implements a Kafka consumer using SSE’s open and lightweight protocol:

from sse_starlette.sse import EventSourceResponse
@router.get('/messenger/sse/add')
async def send_message_stream(request: Request):
        
    async def event_provider():
        while True:
   ...