veloren/network/src/api.rs

use crate::{
    message::{self, InCommingMessage, MessageBuffer, OutGoingMessage},
    scheduler::Scheduler,
    types::{Mid, Pid, Prio, Promises, Requestor::User, Sid},
};
use async_std::{io, sync::RwLock, task};
use futures::{
    channel::{mpsc, oneshot},
    sink::SinkExt,
    stream::StreamExt,
};
use prometheus::Registry;
use serde::{de::DeserializeOwned, Serialize};
use std::{
    collections::HashMap,
    sync::{
        atomic::{AtomicBool, Ordering},
        Arc,
    },
};
use tracing::*;
use tracing_futures::Instrument;
use uvth::ThreadPool;

/// Represents a Tcp or Udp or Mpsc address
#[derive(Clone, Debug, Hash, PartialEq, Eq)]
pub enum Address {
    Tcp(std::net::SocketAddr),
    Udp(std::net::SocketAddr),
    Mpsc(u64),
}

/// `Participants` are generated by the [`Network`] and represent a connection
/// to a remote Participant. Look at the [`connect`] and [`connected`] method of
/// [`Networks`] on how to generate `Participants`
///
/// [`Networks`]: crate::api::Network
/// [`connect`]: Network::connect
/// [`connected`]: Network::connected
pub struct Participant {
    local_pid: Pid,
    remote_pid: Pid,
    stream_open_sender: RwLock<mpsc::UnboundedSender<(Prio, Promises, oneshot::Sender<Stream>)>>,
    stream_opened_receiver: RwLock<mpsc::UnboundedReceiver<Stream>>,
    closed: AtomicBool,
    disconnect_sender: Option<mpsc::UnboundedSender<Pid>>,
}

/// `Streams` represents a channel to send `n` messages with a certain priority
/// and [`Promises`]. messages need always to be send between 2 `Streams`.
///
/// `Streams` are generated by the [`Participant`].
/// Look at the [`open`] and [`opened`] method of [`Participant`] on how to
/// generate `Streams`
///
/// Unlike [`Network`] and [`Participant`], `Streams` don't implement interior
/// mutability, as multiple threads don't need access to the same `Stream`.
/// [`Sync`] is not supported! In that case multiple `Streams` should be used
/// instead. However it's still possible to [`Send`] `Streams`.
///
/// [`Networks`]: crate::api::Network
/// [`open`]: Participant::open
/// [`opened`]: Participant::opened
/// [`Send`]: std::marker::Send
/// [`Sync`]: std::marker::Sync
#[derive(Debug)]
pub struct Stream {
    pid: Pid,
    sid: Sid,
    mid: Mid,
    prio: Prio,
    promises: Promises,
    msg_send_sender: std::sync::mpsc::Sender<(Prio, Pid, Sid, OutGoingMessage)>,
    msg_recv_receiver: mpsc::UnboundedReceiver<InCommingMessage>,
    closed: Arc<AtomicBool>,
    shutdown_sender: Option<mpsc::UnboundedSender<Sid>>,
}

/// Error type thrown by [`Networks`](Network) methods
#[derive(Debug)]
pub enum NetworkError {
    NetworkClosed,
    ListenFailed(std::io::Error),
}

/// Error type thrown by [`Participants`](Participant) methods
#[derive(Debug, PartialEq)]
pub enum ParticipantError {
    ParticipantClosed,
}

/// Error type thrown by [`Streams`](Stream) methods
#[derive(Debug, PartialEq)]
pub enum StreamError {
    StreamClosed,
}

/// Use the `Network` to create connections to other [`Participants`]
///
/// The `Network` is the single source that handles all connections in your
/// Application. You can pass it around multiple threads in an
/// [`Arc`](std::sync::Arc) as all commands have internal mutability.
///
/// The `Network` has methods to [`connect`] and [`disconnect`] to other
/// [`Participants`] via their [`Address`]. All [`Participants`] will be stored
/// in the Network until explicitly disconnected, which is the only way to close
/// the sockets.
///
/// # Examples
/// ```rust
/// use veloren_network::{Network, Pid};
/// use uvth::ThreadPoolBuilder;
///
/// // Create a Network, listen on port `12345` to accept connections and connect to port `80` to connect to a (pseudo) database Application
/// let network = Network::new(Pid::new(), ThreadPoolBuilder::new().build(), None);
/// block_on(async {
///     network.listen(Address::Tcp("127.0.0.1:12345".parse().unwrap())).await?;
///     let database = network.connect(Address::Tcp("127.0.0.1:80".parse().unwrap())).await?;
/// });
/// ```
///
/// [`Participants`]: crate::api::Participant
/// [`connect`]: Network::connect
/// [`disconnect`]: Network::disconnect
pub struct Network {
    local_pid: Pid,
    participants: RwLock<HashMap<Pid, Arc<Participant>>>,
    listen_sender:
        RwLock<mpsc::UnboundedSender<(Address, oneshot::Sender<async_std::io::Result<()>>)>>,
    connect_sender:
        RwLock<mpsc::UnboundedSender<(Address, oneshot::Sender<io::Result<Participant>>)>>,
    connected_receiver: RwLock<mpsc::UnboundedReceiver<Participant>>,
    shutdown_sender: Option<oneshot::Sender<()>>,
}

impl Network {
    /// Generates a new `Network` to handle all connections in an Application
    ///
    /// # Arguments
    /// * `participant_id` - provide it by calling [`Pid::new()`], usually you
    ///   don't want to reuse a Pid for 2 `Networks`
    /// * `thread_pool` - you need to provide a [`ThreadPool`] where exactly 1
    ///   thread will be created to handle all `Network` internals. Additional
    ///   threads will be allocated on an internal async-aware threadpool
    /// * `registry` - Provide a Registy in order to collect Prometheus metrics
    ///   by this `Network`, `None` will deactivate Tracing. Tracing is done via
    ///   [`prometheus`]
    ///
    /// # Examples
    /// ```rust
    /// use uvth::ThreadPoolBuilder;
    /// use veloren_network::{Network, Pid};
    ///
    /// let network = Network::new(Pid::new(), ThreadPoolBuilder::new().build(), None);
    /// ```
    ///
    /// Usually you only create a single `Network` for an application, except
    /// when client and server are in the same application, then you will want
    /// 2. However there are no technical limitations from creating more.
    ///
    /// [`Pid::new()`]: crate::types::Pid::new
    /// [`ThreadPool`]: uvth::ThreadPool
    pub fn new(participant_id: Pid, thread_pool: &ThreadPool, registry: Option<&Registry>) -> Self {
        let p = participant_id;
        debug!(?p, ?User, "starting Network");
        let (scheduler, listen_sender, connect_sender, connected_receiver, shutdown_sender) =
            Scheduler::new(participant_id, registry);
        thread_pool.execute(move || {
            trace!(?p, ?User, "starting sheduler in own thread");
            let _handle = task::block_on(
                scheduler
                    .run()
                    .instrument(tracing::info_span!("scheduler", ?p)),
            );
            trace!(?p, ?User, "stopping sheduler and his own thread");
        });
        Self {
            local_pid: participant_id,
            participants: RwLock::new(HashMap::new()),
            listen_sender: RwLock::new(listen_sender),
            connect_sender: RwLock::new(connect_sender),
            connected_receiver: RwLock::new(connected_receiver),
            shutdown_sender: Some(shutdown_sender),
        }
    }

    /// starts listening on an [`Address`].
    /// When the method returns the `Network` is ready to listen for incoming
    /// connections OR has returned a [`NetworkError`] (e.g. port already used).
    /// You can call [`connected`] to asynchrony wait for a [`Participant`] to
    /// connect. You can call `listen` on multiple addresses, e.g. to
    /// support multiple Protocols or NICs.
    ///
    /// # Examples
    /// ```rust
    /// use uvth::ThreadPoolBuilder;
    /// use veloren_network::{Network, Pid};
    ///
    /// // Create a Network, listen on port `2000` TCP on all NICs and `2001` UDP locally
    /// let network = Network::new(Pid::new(), ThreadPoolBuilder::new().build(), None);
    /// block_on(async {
    ///     network
    ///         .listen(Address::Tcp("0.0.0.0:2000".parse().unwrap()))
    ///         .await?;
    ///     network
    ///         .listen(Address::Udp("127.0.0.1:2001".parse().unwrap()))
    ///         .await?;
    /// });
    /// ```
    ///
    /// [`connected`]: Network::connected
    pub async fn listen(&self, address: Address) -> Result<(), NetworkError> {
        let (result_sender, result_receiver) = oneshot::channel::<async_std::io::Result<()>>();
        debug!(?address, ?User, "listening on address");
        self.listen_sender
            .write()
            .await
            .send((address, result_sender))
            .await?;
        match result_receiver.await? {
            //waiting guarantees that we either listened sucessfully or get an error like port in
            // use
            Ok(()) => Ok(()),
            Err(e) => Err(NetworkError::ListenFailed(e)),
        }
    }

    /// starts connectiong to an [`Address`].
    /// When the method returns the Network either returns a [`Participant`]
    /// ready to open [`Streams`] on OR has returned a [`NetworkError`] (e.g.
    /// can't connect, or invalid Handshake) # Examples
    /// ```rust
    /// use uvth::ThreadPoolBuilder;
    /// use veloren_network::{Network, Pid};
    ///
    /// // Create a Network, connect on port `2000` TCP and `2001` UDP like listening above
    /// let network = Network::new(Pid::new(), ThreadPoolBuilder::new().build(), None);
    /// block_on(async {
    ///     let p1 = network
    ///         .connect(Address::Tcp("127.0.0.1:2000".parse().unwrap()))
    ///         .await?;
    ///     let p2 = network
    ///         .connect(Address::Udp("127.0.0.1:2001".parse().unwrap()))
    ///         .await?;
    ///     assert!(p1.ptr_eq(p2));
    /// });
    /// ```
    /// Usually the `Network` guarantees that a operation on a [`Participant`]
    /// succeeds, e.g. by automatic retrying unless it fails completely e.g. by
    /// disconnecting from the remote. If 2 [`Addresses`] you `connect` to
    /// belongs to the same [`Participant`], you get the same [`Participant`] as
    /// a result. This is useful e.g. by connecting to the same
    /// [`Participant`] via multiple Protocols.
    ///
    /// [`Streams`]: crate::api::Stream
    /// [`Addresses`]: crate::api::Address
    pub async fn connect(&self, address: Address) -> Result<Arc<Participant>, NetworkError> {
        let (pid_sender, pid_receiver) = oneshot::channel::<io::Result<Participant>>();
        debug!(?address, ?User, "connect to address");
        self.connect_sender
            .write()
            .await
            .send((address, pid_sender))
            .await?;
        let participant = pid_receiver.await??;
        let pid = participant.remote_pid;
        debug!(
            ?pid,
            ?User,
            "received Participant id from remote and return to user"
        );
        let participant = Arc::new(participant);
        self.participants
            .write()
            .await
            .insert(participant.remote_pid, participant.clone());
        Ok(participant)
    }

    /// returns a [`Participant`] created from a [`Address`] you called
    /// [`listen`] on before. This function will either return a working
    /// [`Participant`] ready to open [`Streams`] on OR has returned a
    /// [`NetworkError`] (e.g. Network got closed)
    ///
    /// # Examples
    /// ```rust
    /// use uvth::ThreadPoolBuilder;
    /// use veloren_network::{Network, Pid};
    ///
    /// // Create a Network, listen on port `2000` TCP and opens returns their Pid
    /// let network = Network::new(Pid::new(), ThreadPoolBuilder::new().build(), None);
    /// block_on(async {
    ///     network
    ///         .listen(Address::Tcp("0.0.0.0:2000".parse().unwrap()))
    ///         .await?;
    ///     while let Some(participant) = network.connected().await? {
    ///         println!("Participant connected: {}", participant.remote_pid());
    ///     }
    /// });
    /// ```
    ///
    /// [`Streams`]: crate::api::Stream
    /// [`listen`]: crate::api::Network::listen
    pub async fn connected(&self) -> Result<Arc<Participant>, NetworkError> {
        let participant = self.connected_receiver.write().await.next().await?;
        let participant = Arc::new(participant);
        self.participants
            .write()
            .await
            .insert(participant.remote_pid, participant.clone());
        Ok(participant)
    }

    /// disconnecting a [`Participant`] where you move the last existing
    /// [`Arc<Participant>`]. As the [`Network`] also holds [`Arc`] to the
    /// [`Participant`], you need to provide the last [`Arc<Participant>`] and
    /// are not allowed to keep others. If you do so the [`Participant`]
    /// can't be disconnected properly. If you no longer have the respective
    /// [`Participant`], try using the [`participants`] method to get it.
    /// This function will wait for all [`Streams`] to properly close, including
    /// all messages to be send before closing.
    ///
    /// # Examples
    /// ```rust
    /// use uvth::ThreadPoolBuilder;
    /// use veloren_network::{Network, Pid};
    ///
    /// // Create a Network, listen on port `2000` TCP and opens returns their Pid and close connection.
    /// let network = Network::new(Pid::new(), ThreadPoolBuilder::new().build(), None);
    /// block_on(async {
    ///     network
    ///         .listen(Address::Tcp("0.0.0.0:2000".parse().unwrap()))
    ///         .await?;
    ///     while let Some(participant) = network.connected().await? {
    ///         println!("Participant connected: {}", participant.remote_pid());
    ///         network.disconnect(participant).await?;
    ///     }
    /// });
    /// ```
    ///
    /// [`Arc<Participant>`]: crate::api::Participant
    /// [`Streams`]: crate::api::Stream
    /// [`participants`]: Network::participants
    /// [`Arc`]: std::sync::Arc
    pub async fn disconnect(&self, participant: Arc<Participant>) -> Result<(), NetworkError> {
        // Remove, Close and try_unwrap error when unwrap fails!
        let pid = participant.remote_pid;
        debug!(?pid, "removing participant from network");
        self.participants.write().await.remove(&pid)?;
        participant.closed.store(true, Ordering::Relaxed);

        if Arc::try_unwrap(participant).is_err() {
            warn!(
                "you are disconnecting and still keeping a reference to this participant, this is \
                 a bad idea. Participant will only be dropped when you drop your last reference"
            );
        };
        Ok(())
    }

    /// returns a copy of all current connected [`Participants`]
    ///
    /// [`Participants`]: crate::api::Participant
    pub async fn participants(&self) -> HashMap<Pid, Arc<Participant>> {
        self.participants.read().await.clone()
    }
}

impl Participant {
    pub(crate) fn new(
        local_pid: Pid,
        remote_pid: Pid,
        stream_open_sender: mpsc::UnboundedSender<(Prio, Promises, oneshot::Sender<Stream>)>,
        stream_opened_receiver: mpsc::UnboundedReceiver<Stream>,
        disconnect_sender: mpsc::UnboundedSender<Pid>,
    ) -> Self {
        Self {
            local_pid,
            remote_pid,
            stream_open_sender: RwLock::new(stream_open_sender),
            stream_opened_receiver: RwLock::new(stream_opened_receiver),
            closed: AtomicBool::new(false),
            disconnect_sender: Some(disconnect_sender),
        }
    }

    /// Opens a [`Stream`] on this `Participant` with a certain Priority and
    /// [`Promises`]
    ///
    /// # Arguments
    /// * `prio` - valid between 0-63. The priority rates the throughput for
    ///   messages of the [`Stream`] e.g. prio 5 messages will get 1/2 the speed
    ///   prio0 messages have. Prio10 messages only 1/4 and Prio 15 only 1/8,
    ///   etc...
    /// * `promises` - use a combination of you prefered [`Promises`], see the
    ///   link for further documentation. You can combine them, e.g.
    ///   `PROMISES_ORDERED | PROMISES_CONSISTENCY` The Stream will then
    ///   guarantee that those promisses are met.
    ///
    /// A [`ParticipantError`] might be thrown if the `Participant` is already
    /// closed. [`Streams`] can be created without a answer from the remote
    /// side, resulting in very fast creation and closing latency.
    ///
    /// # Examples
    /// ```rust
    /// use uvth::ThreadPoolBuilder;
    /// use veloren_network::{Network, Pid, PROMISES_CONSISTENCY, PROMISES_ORDERED};
    ///
    /// // Create a Network, connect on port 2000 and open a stream
    /// let network = Network::new(Pid::new(), ThreadPoolBuilder::new().build(), None);
    /// block_on(async {
    ///     let p1 = network
    ///         .connect(Address::Tcp("127.0.0.1:2000".parse().unwrap()))
    ///         .await?;
    ///     let _s1 = p1
    ///         .open(100, PROMISES_ORDERED | PROMISES_CONSISTENCY)
    ///         .await?;
    /// });
    /// ```
    ///
    /// [`Streams`]: crate::api::Stream
    pub async fn open(&self, prio: u8, promises: Promises) -> Result<Stream, ParticipantError> {
        //use this lock for now to make sure that only one open at a time is made,
        // TODO: not sure if we can paralise that, check in future
        let mut stream_open_sender = self.stream_open_sender.write().await;
        if self.closed.load(Ordering::Relaxed) {
            warn!(?self.remote_pid, "participant is closed but another open is tried on it");
            return Err(ParticipantError::ParticipantClosed);
        }
        let (sid_sender, sid_receiver) = oneshot::channel();
        if stream_open_sender
            .send((prio, promises, sid_sender))
            .await
            .is_err()
        {
            debug!(?self.remote_pid, ?User, "stream_open_sender failed, closing participant");
            self.closed.store(true, Ordering::Relaxed);
            return Err(ParticipantError::ParticipantClosed);
        }
        match sid_receiver.await {
            Ok(stream) => {
                let sid = stream.sid;
                debug!(?sid, ?self.remote_pid, ?User, "opened stream");
                Ok(stream)
            },
            Err(_) => {
                debug!(?self.remote_pid, ?User, "sid_receiver failed, closing participant");
                self.closed.store(true, Ordering::Relaxed);
                Err(ParticipantError::ParticipantClosed)
            },
        }
    }

    /// Use this method to handle [`Streams`] opened from remote site, like the
    /// [`connected`] method of [`Network`]. This is the associated method
    /// to [`open`]. It's guaranteed that the order of [`open`] and `opened`
    /// is equal. The `nth` [`Streams`] on one side will represent the `nth` on
    /// the other side. A [`ParticipantError`] might be thrown if the
    /// `Participant` is already closed.
    ///
    /// # Examples
    /// ```rust
    /// use veloren_network::{Network, Pid, PROMISES_ORDERED, PROMISES_CONSISTENCY};
    /// use uvth::ThreadPoolBuilder;
    ///
    /// // Create a Network, connect on port 2000 and wait for the other side to open a stream
    /// // Note: It's quite unusal to activly connect, but then wait on a stream to be connected, usually the Appication taking initiative want's to also create the first Stream.
    /// let network = Network::new(Pid::new(), ThreadPoolBuilder::new().build(), None);
    /// block_on(async {
    ///     let p1 = network.connect(Address::Tcp("127.0.0.1:2000".parse().unwrap())).await?;
    ///     let _s1 = p1.opened().await?;
    /// });
    /// ```
    ///
    /// [`Streams`]: crate::api::Stream
    /// [`connected`]: Network::connected
    /// [`open`]: Participant::open
    pub async fn opened(&self) -> Result<Stream, ParticipantError> {
        //use this lock for now to make sure that only one open at a time is made,
        // TODO: not sure if we can paralise that, check in future
        let mut stream_opened_receiver = self.stream_opened_receiver.write().await;
        if self.closed.load(Ordering::Relaxed) {
            warn!(?self.remote_pid, "participant is closed but another open is tried on it");
            return Err(ParticipantError::ParticipantClosed);
        }
        match stream_opened_receiver.next().await {
            Some(stream) => {
                let sid = stream.sid;
                debug!(?sid, ?self.remote_pid, "receive opened stream");
                Ok(stream)
            },
            None => {
                debug!(?self.remote_pid, "stream_opened_receiver failed, closing participant");
                self.closed.store(true, Ordering::Relaxed);
                Err(ParticipantError::ParticipantClosed)
            },
        }
    }

    /// Returns the remote [`Pid`]
    pub fn remote_pid(&self) -> Pid { self.remote_pid }
}

impl Stream {
    pub(crate) fn new(
        pid: Pid,
        sid: Sid,
        prio: Prio,
        promises: Promises,
        msg_send_sender: std::sync::mpsc::Sender<(Prio, Pid, Sid, OutGoingMessage)>,
        msg_recv_receiver: mpsc::UnboundedReceiver<InCommingMessage>,
        closed: Arc<AtomicBool>,
        shutdown_sender: mpsc::UnboundedSender<Sid>,
    ) -> Self {
        Self {
            pid,
            sid,
            mid: 0,
            prio,
            promises,
            msg_send_sender,
            msg_recv_receiver,
            closed,
            shutdown_sender: Some(shutdown_sender),
        }
    }

    /// use to send a arbitrary message to the remote side, by having the remote
    /// side also opened a `Stream` linked to this. the message will be
    /// [`Serialized`], which actually is quite slow compared to most other
    /// calculations done. A faster method [`send_raw`] exists, when extra
    /// speed is needed. The other side needs to use the respective [`recv`]
    /// function and know the type send.
    ///
    /// `send` is an exception to the `async` messages, as it's probably called
    /// quite often so it doesn't wait for execution. Which also means, that
    /// no feedback is provided. It's to assume that the Message got `send`
    /// correctly. If a error occurred, the next call will return an Error.
    /// If the [`Participant`] disconnected it will also be unable to be used
    /// any more. A [`StreamError`] will be returned in the error case, e.g.
    /// when the `Stream` got closed already.
    ///
    /// Note when a `Stream` is dropped, it will still send all messages, though
    /// the `drop` will return immediately, however, when a [`Participant`]
    /// gets gracefully shut down, all remaining messages will be send.
    ///
    /// # Example
    /// ```rust
    /// use futures::executor::block_on;
    /// use veloren_network::{Network, Pid};
    ///
    /// let network = Network::new(Pid::new(), ThreadPoolBuilder::new().build(), None);
    /// block_on(async {
    ///     let participant_a = network.connected().await;
    ///     let mut stream_a = participant_a.opened().await;
    ///     //Send  Message
    ///     stream_a.send("Hello World");
    /// });
    /// ```
    ///
    /// [`send_raw`]: Stream::send_raw
    /// [`recv`]: Stream::recv
    /// [`Serialized`]: Serialize
    pub fn send<M: Serialize>(&mut self, msg: M) -> Result<(), StreamError> {
        self.send_raw(Arc::new(message::serialize(&msg)))
    }

    /// This methods give the option to skip multiple calls of [`bincode`], e.g.
    /// in case the same Message needs to send on multiple `Streams` to multiple
    /// [`Participants`]. Other then that, the same rules apply than for
    /// [`send`]
    ///
    /// # Example
    /// ```rust
    /// use bincode;
    /// use futures::executor::block_on;
    /// use veloren_network::{Network, Pid};
    ///
    /// let network = Network::new(Pid::new(), ThreadPoolBuilder::new().build(), None);
    /// block_on(async {
    ///     let participant_a = network.connected().await;
    ///     let participant_b = network.connected().await;
    ///     let mut stream_a = participant_a.opened().await;
    ///     let mut stream_b = participant_a.opened().await;
    ///
    ///     //Prepare Message and decode it
    ///     let msg = "Hello World";
    ///     let raw_msg = Arc::new(MessageBuffer {
    ///         data: bincode::serialize(&msg).unwrap(),
    ///     });
    ///     //Send same Message to multiple Streams
    ///     stream_a.send_raw(raw_msg.clone());
    ///     stream_b.send_raw(raw_msg.clone());
    /// });
    /// ```
    ///
    /// [`send`]: Stream::send
    /// [`Participants`]: crate::api::Participant
    pub fn send_raw(&mut self, messagebuffer: Arc<MessageBuffer>) -> Result<(), StreamError> {
        if self.closed.load(Ordering::Relaxed) {
            return Err(StreamError::StreamClosed);
        }
        debug!(?messagebuffer, ?User, "sending a message");
        self.msg_send_sender
            .send((self.prio, self.pid, self.sid, OutGoingMessage {
                buffer: messagebuffer,
                cursor: 0,
                mid: self.mid,
                sid: self.sid,
            }))?;
        self.mid += 1;
        Ok(())
    }

    /// use `recv` to wait on a Message send from the remote side by their
    /// `Stream`. The Message needs to implement [`DeserializeOwned`] and
    /// thus, the resulting type must already be known by the receiving side.
    /// If this is not know from the Application logic, one could use a `Enum`
    /// and then handle the received message via a `match` state.
    ///
    /// A [`StreamError`] will be returned in the error case, e.g. when the
    /// `Stream` got closed already.
    pub async fn recv<M: DeserializeOwned>(&mut self) -> Result<M, StreamError> {
        Ok(message::deserialize(self.recv_raw().await?))
    }

    /// the equivalent like [`send_raw`] but for [`recv`], no [`bincode`] is
    /// executed for performance reasons.
    ///
    /// [`send_raw`]: Stream::send_raw
    /// [`recv`]: Stream::recv
    pub async fn recv_raw(&mut self) -> Result<MessageBuffer, StreamError> {
        //no need to access self.closed here, as when this stream is closed the Channel
        // is closed which will trigger a None
        let msg = self.msg_recv_receiver.next().await?;
        info!(?msg, ?User, "delivering a message");
        Ok(msg.buffer)
    }
}

impl Drop for Network {
    fn drop(&mut self) {
        let pid = self.local_pid;
        debug!(?pid, "shutting down Network");
        self.shutdown_sender
            .take()
            .unwrap()
            .send(())
            .expect("scheduler is closed, but nobody other should be able to close it");
    }
}

impl Drop for Participant {
    fn drop(&mut self) {
        // ignore closed, as we need to send it even though we disconnected the
        // participant from network
        let pid = self.remote_pid;
        debug!(?pid, "shutting down Participant");
        task::block_on(async {
            self.disconnect_sender
                .take()
                .unwrap()
                .send(self.remote_pid)
                .await
                .expect("something is wrong in internal scheduler coding")
        });
    }
}

impl Drop for Stream {
    fn drop(&mut self) {
        // a send if closed is unecessary but doesnt hurt, we must not crash here
        if !self.closed.load(Ordering::Relaxed) {
            let sid = self.sid;
            let pid = self.pid;
            debug!(?pid, ?sid, "shutting down Stream");
            if task::block_on(self.shutdown_sender.take().unwrap().send(self.sid)).is_err() {
                warn!(
                    "Other side got already dropped, probably due to timing, other side will \
                     handle this gracefully"
                );
            };
        }
    }
}

impl std::fmt::Debug for Participant {
    #[inline]
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let status = if self.closed.load(Ordering::Relaxed) {
            "[CLOSED]"
        } else {
            "[OPEN]"
        };
        write!(
            f,
            "Participant {{{} local_pid: {:?}, remote_pid: {:?} }}",
            status, &self.local_pid, &self.remote_pid,
        )
    }
}

impl<T> From<std::sync::mpsc::SendError<T>> for StreamError {
    fn from(_err: std::sync::mpsc::SendError<T>) -> Self { StreamError::StreamClosed }
}

impl<T> From<std::sync::mpsc::SendError<T>> for ParticipantError {
    fn from(_err: std::sync::mpsc::SendError<T>) -> Self { ParticipantError::ParticipantClosed }
}

impl<T> From<std::sync::mpsc::SendError<T>> for NetworkError {
    fn from(_err: std::sync::mpsc::SendError<T>) -> Self { NetworkError::NetworkClosed }
}

impl From<async_std::io::Error> for NetworkError {
    fn from(err: async_std::io::Error) -> Self { NetworkError::ListenFailed(err) }
}

impl From<std::option::NoneError> for StreamError {
    fn from(_err: std::option::NoneError) -> Self { StreamError::StreamClosed }
}

impl From<std::option::NoneError> for ParticipantError {
    fn from(_err: std::option::NoneError) -> Self { ParticipantError::ParticipantClosed }
}

impl From<std::option::NoneError> for NetworkError {
    fn from(_err: std::option::NoneError) -> Self { NetworkError::NetworkClosed }
}

impl From<mpsc::SendError> for ParticipantError {
    fn from(_err: mpsc::SendError) -> Self { ParticipantError::ParticipantClosed }
}

impl From<mpsc::SendError> for NetworkError {
    fn from(_err: mpsc::SendError) -> Self { NetworkError::NetworkClosed }
}

impl From<oneshot::Canceled> for ParticipantError {
    fn from(_err: oneshot::Canceled) -> Self { ParticipantError::ParticipantClosed }
}

impl From<oneshot::Canceled> for NetworkError {
    fn from(_err: oneshot::Canceled) -> Self { NetworkError::NetworkClosed }
}