TCP, FramedTCP message send is not truly async #177
Description
As seen in TODO comment and behaviour on io::ErrorKind::WouldBlock.
In server case this blocks communication with other clients.
I stumbled upon a situation when a faulty virtual network tunnel doesn't process sent data and whole program gets stuck in this loop and has 100% CPU utilization. It causes issues and delays in other situations too with large messages.
https://github.com/lemunozm/message-io/blob/master/src/adapters/tcp.rs#L187
fn send(&self, data: &[u8]) -> SendStatus {
// TODO: The current implementation implies an active waiting,
// improve it using POLLIN instead to avoid active waiting.
// Note: Despite the fear that an active waiting could generate,
// this only occurs in the case when the receiver is full because reads slower that it sends.
let mut total_bytes_sent = 0;
loop {
let mut stream = &self.stream;
match stream.write(&data[total_bytes_sent..]) {
Ok(bytes_sent) => {
total_bytes_sent += bytes_sent;
if total_bytes_sent == data.len() {
break SendStatus::Sent
}
}
Err(ref err) if err.kind() == io::ErrorKind::WouldBlock => continue,
// Others errors are considered fatal for the connection.
// a Event::Disconnection will be generated later.
Err(err) => {
log::error!("TCP receive error: {}", err);
break SendStatus::ResourceNotFound // should not happen
}
}
}
}