What happens to the connection between YARP and the target when the client closed the connection between the browser and YARP?

[wetsai]

Hi, we are using YARP to forward requests in our services. We are seeing some "The request was canceled before receiving a response." debug messages in telemetry. However, we noticed when this happened the target is still continuing processing the request even though the client-YARP connection has been closed. I was wondering if YARP closes the YARP-target connection then the client closes its connection?

Thanks,

[MihaZupan]

It'll depend on the type of request, the HTTP version, and when during the request the client disconnected.

If the client disconnects while YARP is sending out a request to the backend, YARP will "cancel" that outgoing request.
What that means in practice is that we'll close the TCP connection when using HTTP/1.1, or send a reset frame on HTTP/2.
If you're using Kestrel on the backend, both of these would be surfaced to you as HttpContext.RequestAborted getting signaled.

A small exception to that is that if the client disconnects while you're copying back the response, YARP will attempt to keep reading for a short period in hopes that the response is short and that we'll be able to reuse the connection.
This is controlled via SocketsHttpHandler.ResponseDrainTimeout (defaults to 2 second) and SocketsHttpHandler.MaxResponseDrainSize (defaults to 1 MB).
If we hit either limit, we'll go back to closing the connection.

Are you using HttpContext.RequestAborted on the backend to cancel work?