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use crate::{protocols::ReturnableConnection, Pea2Pea};
#[cfg(doc)]
use crate::{protocols::Handshake, Config, Node};
use async_trait::async_trait;
use parking_lot::RwLock;
use tokio::{
io::{AsyncWrite, AsyncWriteExt},
sync::{mpsc, oneshot},
};
use tracing::*;
use std::{any::Any, collections::HashMap, io, net::SocketAddr};
/// Can be used to specify and enable writing, i.e. sending outbound messages. If the [`Handshake`]
/// protocol is enabled too, it goes into force only after the handshake has been concluded.
#[async_trait]
pub trait Writing: Pea2Pea
where
Self: Clone + Send + Sync + 'static,
{
/// The type of the outbound messages; unless their serialization is expensive and the message
/// is broadcasted (in which case it would get serialized multiple times), serialization should
/// be done in [`Writing::write_message`].
type Message: Send;
/// Prepares the node to send messages.
async fn enable_writing(&self) {
let (conn_sender, mut conn_receiver) = mpsc::unbounded_channel::<ReturnableConnection>();
// Use a channel to know when the writing task is ready.
let (tx_writing, rx_writing) = oneshot::channel::<()>();
// the task spawning tasks reading messages from the given stream
let self_clone = self.clone();
let writing_task = tokio::spawn(async move {
trace!(parent: self_clone.node().span(), "spawned the Writing handler task");
tx_writing.send(()).unwrap(); // safe; the channel was just opened
// these objects are sent from `Node::adapt_stream`
while let Some((mut conn, conn_returner)) = conn_receiver.recv().await {
let addr = conn.addr;
let mut writer = conn.writer.take().unwrap(); // safe; it is available at this point
let mut buffer = Vec::new();
let (outbound_message_sender, mut outbound_message_receiver) =
mpsc::channel(self_clone.node().config().outbound_queue_depth);
if let Some(handler) = self_clone.node().protocols.writing_handler.get() {
handler
.senders
.write()
.insert(addr, outbound_message_sender);
} else {
unreachable!();
}
// Use a channel to know when the writer task is ready.
let (tx_writer, rx_writer) = oneshot::channel::<()>();
// the task for writing outbound messages
let writer_clone = self_clone.clone();
let writer_task = tokio::spawn(async move {
let node = writer_clone.node();
trace!(parent: node.span(), "spawned a task for writing messages to {}", addr);
tx_writer.send(()).unwrap(); // safe; the channel was just opened
while let Some(wrapped_msg) = outbound_message_receiver.recv().await {
let msg = wrapped_msg.msg.downcast::<Self::Message>().unwrap();
match writer_clone
.write_to_stream(*msg, addr, &mut buffer, &mut writer)
.await
{
Ok(len) => {
let _ = wrapped_msg.delivery_notification.send(true);
node.known_peers().register_sent_message(addr, len);
node.stats().register_sent_message(len);
trace!(parent: node.span(), "sent {}B to {}", len, addr);
}
Err(e) => {
let _ = wrapped_msg.delivery_notification.send(false);
node.known_peers().register_failure(addr);
error!(parent: node.span(), "couldn't send a message to {}: {}", addr, e);
if node.config().fatal_io_errors.contains(&e.kind()) {
node.disconnect(addr).await;
break;
}
}
}
}
});
let _ = rx_writer.await;
conn.tasks.push(writer_task);
// return the Connection to the Node, resuming Node::adapt_stream
if conn_returner.send(Ok(conn)).is_err() {
unreachable!("could't return a Connection to the Node");
}
}
});
let _ = rx_writing.await;
self.node().tasks.lock().push(writing_task);
// register the WritingHandler with the Node
let hdl = WritingHandler {
handler: conn_sender,
senders: Default::default(),
};
assert!(
self.node().protocols.writing_handler.set(hdl).is_ok(),
"the Writing protocol was enabled more than once!"
);
}
/// Writes the given message to the given writer, using the provided intermediate buffer; returns the number of
/// bytes written to the writer.
async fn write_to_stream<W: AsyncWrite + Unpin + Send>(
&self,
message: Self::Message,
addr: SocketAddr,
buffer: &mut Vec<u8>,
writer: &mut W,
) -> io::Result<usize> {
self.write_message(addr, &message, buffer)?;
let len = buffer.len();
writer.write_all(buffer).await?;
buffer.clear();
Ok(len)
}
/// Writes the provided payload to the given intermediate writer; the payload can get prepended with a header
/// indicating its length, be suffixed with a character indicating that it's complete, etc. The `target`
/// parameter is provided in case serialization depends on the recipient, e.g. in case of encryption.
///
/// note: The default `writer` is a memory buffer and thus writing to it is infallible.
fn write_message<W: io::Write>(
&self,
target: SocketAddr,
message: &Self::Message,
writer: &mut W,
) -> io::Result<()>;
/// Sends the provided message to the specified [`SocketAddr`]. Returns as soon as the message is queued to
/// be sent, without waiting for the actual delivery; instead, the caller is provided with a [`oneshot::Receiver`]
/// which can be used to determine when and whether the message has been delivered.
///
/// # Errors
///
/// The following errors can be returned:
/// - [`io::ErrorKind::NotConnected`] if the node is not connected to the provided address
/// - [`io::ErrorKind::Other`] if the outbound message queue for this address is full
/// - [`io::ErrorKind::Unsupported`] if [`Writing::enable_writing`] hadn't been called yet
fn send_direct_message(
&self,
addr: SocketAddr,
message: Self::Message,
) -> io::Result<oneshot::Receiver<bool>> {
// access the protocol handler
if let Some(handler) = self.node().protocols.writing_handler.get() {
// find the message sender for the given address
if let Some(sender) = handler.senders.read().get(&addr).cloned() {
let (msg, delivery) = WrappedMessage::new(Box::new(message));
sender.try_send(msg).map_err(|e| {
error!(parent: self.node().span(), "can't send a message to {}: {}", addr, e);
self.node().stats().register_failure();
io::ErrorKind::Other.into()
}).map(|_| delivery)
} else {
Err(io::ErrorKind::NotConnected.into())
}
} else {
Err(io::ErrorKind::Unsupported.into())
}
}
/// Broadcasts the provided message to all connected peers. Returns as soon as the message is queued to
/// be sent to all the peers, without waiting for the actual delivery. This method doesn't provide the
/// means to check when and if the messages actually get delivered; you can achieve that by calling
/// [`Writing::send_direct_message`] for each address returned by [`Node::connected_addrs`].
///
/// # Errors
///
/// Returns [`io::ErrorKind::Unsupported`] if [`Writing::enable_writing`] hadn't been called yet.
fn send_broadcast(&self, message: Self::Message) -> io::Result<()>
where
Self::Message: Clone,
{
// access the protocol handler
if let Some(handler) = self.node().protocols.writing_handler.get() {
let senders = handler.senders.read().clone();
for (addr, message_sender) in senders {
let (msg, _delivery) = WrappedMessage::new(Box::new(message.clone()));
let _ = message_sender.try_send(msg).map_err(|e| {
error!(parent: self.node().span(), "can't send a message to {}: {}", addr, e);
self.node().stats().register_failure();
});
}
Ok(())
} else {
Err(io::ErrorKind::Unsupported.into())
}
}
}
/// Used to queue messages for delivery.
pub(crate) struct WrappedMessage {
msg: Box<dyn Any + Send>,
delivery_notification: oneshot::Sender<bool>,
}
impl WrappedMessage {
fn new(msg: Box<dyn Any + Send>) -> (Self, oneshot::Receiver<bool>) {
let (tx, rx) = oneshot::channel();
let wrapped_msg = Self {
msg,
delivery_notification: tx,
};
(wrapped_msg, rx)
}
}
/// The handler object dedicated to the [`Writing`] protocol.
pub struct WritingHandler {
handler: mpsc::UnboundedSender<ReturnableConnection>,
pub(crate) senders: RwLock<HashMap<SocketAddr, mpsc::Sender<WrappedMessage>>>,
}
impl WritingHandler {
pub(crate) fn trigger(&self, item: ReturnableConnection) {
if self.handler.send(item).is_err() {
unreachable!(); // protocol's task is down! can't recover
}
}
}