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Long-polling example

This example shows an example of long-polling implemented with BlackSheep.

The JavaScript and front-end part of this example was adopted from: https://javascript.info/long-polling.

Trying the example

  1. Create a Python virtual environment
  2. Install depedencies (pip install blacksheep uvicorn)
  3. Run the server with uvicorn server:app
  4. Open the web site in several browser tabs to see the effect of long-polling
  5. Submit messages in a browser tab: see how messages are immediately visible in all tabs, thanks to long-polling
  6. Read the source code in server.py to see how long-polling is achieved using asyncio.Queue, and how signal.getsignal(signal.SIGINT) is used in the @app.on_start event handler.
  7. The /subscribe method is used to subscribe for long-polling.
  8. The /publish method is used to publish a message to all subscribers.

How to test a disconnection

To test a client that disconnects, refresh a browser tab, then send a message from an active tab. The console should display messages like this one:

INFO:     127.0.0.1:40834 - "POST /publish HTTP/1.1" 200 OK
🔥🔥🔥 Request is disconnected!
🔥🔥🔥 Request is disconnected!
🔥🔥🔥 Request is disconnected!
🔥🔥🔥 Request is disconnected!
🔥🔥🔥 Request is disconnected!
INFO:     127.0.0.1:40832 - "GET /subscribe?random=0.16177484986012614 HTTP/1.1" 200 OK
INFO:     127.0.0.1:40882 - "GET /subscribe?random=0.08956117949704501 HTTP/1.1" 200 OK
INFO:     127.0.0.1:40882 - "GET /subscribe?random=0.08956117949704501 HTTP/1.1" 200 OK
INFO:     127.0.0.1:40832 - "GET /subscribe?random=0.16177484986012614 HTTP/1.1" 200 OK