tokio::{select, net::TcpListener} not mixing well

[amitu]

I am using tokio to create a HTTP server and am trying to use tokio::select! {}, but it is leading to intermittent connection refused error.

I have fixed this issue by removing the listener.accept() from the tokio::select {} https://github.com/kulfi-project/kulfi/pull/62 (check the first commit).

The three items we have in my tokio::select {} are tokio::net::TcpListener::accept(), tokio_util::sync::CancellationToken::cancelled() and tokio::sync::watch::Receiver::changed() and all three claim in their docs that they are cancellation safe.

I have not done extensive testing, but it def improves things. I have tested it only on Mac.

Have I encountered a bug? When I get time I will try to create minimal reproducible test case to check if something else I am doing is causing this.

[Darksonn]

The problem is that you're calling accept() twice. For one of the calls, you ignore errors, and for the other call you ignore successful calls. The connection refused happens when the Err() branch accepts a connection and immediately throws it away since it's not an error. You have to instead match on the result after the => instead of using two branches on the select!.