tools/async_io: do not error on Accept for StaticIncoming

in proxmox-backup-proxy, we log and discard any errors on 'accept',
so that we can continue to server requests

in proxmox-backup-api, we just have the StaticIncoming that accepts,
which will forward any errors from the underlying TcpListener

this patch also logs and discards the errors, like in the proxy.
Otherwise it could happen that if the api-daemon has more files open
than the proxy, it will shut itself down because of a
'too many open files' error if there are many open connections

(the service should also restart on exit i think, but this is
a separate issue)

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>

src/tools/async_io.rs

@@ -6,6 +6,7 @@ use std::pin::Pin;
 use std::task::{Context, Poll};
 
 use futures::stream::{Stream, TryStream};
+use futures::ready;
 use tokio::io::{AsyncRead, AsyncWrite, ReadBuf};
 use tokio::net::TcpListener;
 use hyper::client::connect::Connection;
@@ -108,10 +109,15 @@ impl hyper::server::accept::Accept for StaticIncoming {
         self: Pin<&mut Self>,
         cx: &mut Context,
     ) -> Poll<Option<Result<Self::Conn, Self::Error>>> {
-        match self.get_mut().0.poll_accept(cx) {
-            Poll::Pending => Poll::Pending,
-            Poll::Ready(Ok((conn, _addr))) => Poll::Ready(Some(Ok(conn))),
-            Poll::Ready(Err(err)) => Poll::Ready(Some(Err(err))),
+        let this = self.get_mut();
+        loop {
+            match ready!(this.0.poll_accept(cx)) {
+                Ok((conn, _addr)) => return Poll::Ready(Some(Ok(conn))),
+                Err(err) => {
+                    eprintln!("error accepting connection: {}", err);
+                    continue;
+                }
+            }
         }
     }
 }