[pve-devel] [RFC PATCH] fix #3106: correctly queue incoming connections

[Dietmar Maurer]

> > -            let connections = proxmox_backup::tools::async_io::HyperAccept(connections);
> > +            let connections = accept_connections(listener, acceptor);
> > +            let connections = hyper::server::accept::from_stream(connections);
> 
> If we move the `from_stream` into the function below...

I have tried to do that for 2 hours, then gave up....
So please tell m e how to make that work!

> >  
> >              Ok(ready
> > -                .and_then(|_| hyper::Server::builder(connections)
> > +               .and_then(|_| hyper::Server::builder(connections)
> >                      .serve(rest_server)
> >                      .with_graceful_shutdown(server::shutdown_future())
> >                      .map_err(Error::from)
> > @@ -170,6 +157,66 @@ async fn run() -> Result<(), Error> {
> >      Ok(())
> >  }
> >  
> > +fn accept_connections(
> > +    mut listener: tokio::net::TcpListener,
> > +    acceptor: Arc<openssl::ssl::SslAcceptor>,
> > +) -> tokio::sync::mpsc::Receiver<Result<tokio_openssl::SslStream<tokio::net::TcpStream>, Error>> {
> 
> ... then this could probably be shortened to
> 
>     ) -> impl Accept {
> 
> shortens the line by 80 ;-)
> 
> > +
> > +    let (sender, receiver) = tokio::sync::mpsc::channel(100);
> > +
> > +    let accept_counter = Arc::new(AtomicUsize::new(0));
> > +
> > +    const MAX_PENDING_ACCEPTS: usize = 100;
> > +
> > +    tokio::spawn(async move {
> > +        loop {
> > +            match listener.accept().await {
> > +                Err(err) => {
> > +                    eprintln!("error accepting tcp connection: {}", err);
> > +                }
> > +                Ok((sock, _addr)) =>  {
> > +                    sock.set_nodelay(true).unwrap();
> > +                    let _ = set_tcp_keepalive(sock.as_raw_fd(), PROXMOX_BACKUP_TCP_KEEPALIVE_TIME);
> > +                    let acceptor = Arc::clone(&acceptor);
> > +                    let mut sender = sender.clone();
> > +
> > +                    if accept_counter.load(Ordering::SeqCst) > MAX_PENDING_ACCEPTS {
> > +                        eprintln!("connection rejected - to many open connections");
> > +                        continue;
> > +                    }
> > +                    accept_counter.fetch_add(1, Ordering::SeqCst);
> 
> We should think about making a counter guard for this sort of thing,
> because from this point onward we're not allowed to use `?` anywhere,
> which is quite annoying.

yes

> 
> > +
> > +                    let accept_counter = accept_counter.clone();
> > +                    tokio::spawn(async move {
> > +                        let accept_future = tokio::time::timeout(
> > +                            Duration::new(10, 0), tokio_openssl::accept(&acceptor, sock));
> > +
> > +                        let result = accept_future.await;
> > +
> > +                        match result {
> > +                            Ok(Ok(connection)) => {
> > +                                if let Err(_) = sender.send(Ok(connection)).await {
> > +                                    eprintln!("detect closed connection channel");
> > +                                }
> > +                            }
> > +                            Ok(Err(err)) => {
> > +                                eprintln!("https handshakeX failed - {}", err);
> > +                            }
> > +                            Err(_) => {
> > +                                eprintln!("https handshake timeout");
> > +                            }
> > +                        }
> 
> which is why I'd rather thave the part above in its own `async fn`
> followed by the `fetch_sub` below, followed by the `eprintln!()`s.
> 
> > +
> > +                        accept_counter.fetch_sub(1, Ordering::SeqCst);
> > +                    });
> > +                }
> > +            }
> > +        }
> > +    });
> > +
> > +    receiver
> > +}
> > +
> >  fn start_stat_generator() {
> >      let abort_future = server::shutdown_future();
> >      let future = Box::pin(run_stat_generator());
> > -- 
> > 2.20.1