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use crate::{connections::ConnectionReader, protocols::ReturnableConnection, Pea2Pea};
use async_trait::async_trait;
use tokio::{io::AsyncReadExt, sync::mpsc, task::JoinHandle, time::sleep};
use tracing::*;
use std::{io, net::SocketAddr, time::Duration};
/// Can be used to specify and enable reading, i.e. receiving inbound messages.
/// If handshaking is enabled too, it goes into force only after the handshake has been concluded.
#[async_trait]
pub trait Reading: Pea2Pea
where
Self: Clone + Send + Sync + 'static,
{
/// The final (deserialized) type of incoming messages.
type Message: Send;
// TODO: add an associated type defaulting to ConnectionReader once
// https://github.com/rust-lang/rust/issues/29661 is resolved.
/// Prepares the node to receive messages; failures to read from a connection's stream are penalized by a timeout
/// defined in `NodeConfig`, while broken/unreadable messages result in an immediate disconnect (in order to avoid
/// accidentally reading "borked" messages).
fn enable_reading(&self) {
let (conn_sender, mut conn_receiver) =
mpsc::channel::<ReturnableConnection>(self.node().config.reading_handler_queue_depth);
// the main task spawning per-connection tasks reading messages from their streams
let self_clone = self.clone();
let reading_task = tokio::spawn(async move {
trace!(parent: self_clone.node().span(), "spawned the Reading handler task");
loop {
// these objects are sent from `Node::adapt_stream`
if let Some((mut conn, conn_returner)) = conn_receiver.recv().await {
let addr = conn.addr;
let mut conn_reader = conn.reader.take().unwrap(); // safe; it is available at this point
let (inbound_message_sender, mut inbound_message_receiver) =
mpsc::channel(self_clone.node().config.conn_inbound_queue_depth);
// the task for reading messages from a stream
let reader_clone = self_clone.clone();
let reader_task = tokio::spawn(async move {
let node = reader_clone.node();
trace!(parent: node.span(), "spawned a task for reading messages from {}", addr);
loop {
if let Err(e) = reader_clone
.read_from_stream(&mut conn_reader, &inbound_message_sender)
.await
{
node.known_peers().register_failure(addr);
match e.kind() {
io::ErrorKind::InvalidData | io::ErrorKind::BrokenPipe => {
// can't recover; drop the connection
node.disconnect(addr);
break;
}
io::ErrorKind::Other => {
// an unsuccessful read from the stream is not fatal; instead of disconnecting,
// impose a timeout before attempting another read
sleep(Duration::from_secs(
node.config.invalid_message_penalty_secs,
))
.await;
}
_ => unreachable!(),
}
}
}
});
// the task for processing parsed messages
let processing_clone = self_clone.clone();
let inbound_processing_task = tokio::spawn(async move {
let node = processing_clone.node();
trace!(parent: node.span(), "spawned a task for processing messages from {}", addr);
loop {
if let Some(msg) = inbound_message_receiver.recv().await {
if let Err(e) = processing_clone.process_message(addr, msg).await {
error!(parent: node.span(), "can't process an inbound message: {}", e);
node.known_peers().register_failure(addr);
}
} else {
node.disconnect(addr);
break;
}
}
});
// the Connection object registers the handles of the
// newly created tasks before being returned to the Node
conn.tasks.push(reader_task);
conn.tasks.push(inbound_processing_task);
// return the Connection to the Node, resuming Node::adapt_stream
if conn_returner.send(Ok(conn)).is_err() {
// can't recover if this happens
panic!("can't return a Connection to the Node");
}
} else {
error!("the Reading protocol is down!");
break;
}
}
});
// register the ReadingHandler with the Node
self.node()
.set_reading_handler((conn_sender, reading_task).into());
}
/// Performs a read from the stream. The default implementation is buffered; it sacrifices a bit of simplicity for
/// better performance. Read messages are sent to a message processing task, in order to allow faster reads from
/// the stream.
async fn read_from_stream(
&self,
conn_reader: &mut ConnectionReader,
message_sender: &mpsc::Sender<Self::Message>,
) -> io::Result<()> {
let ConnectionReader {
node,
addr,
reader,
buffer,
carry,
} = conn_reader;
// perform a read from the stream, being careful not to overwrite any bytes carried over from the previous read
match reader.read(&mut buffer[*carry..]).await {
Ok(0) => return Ok(()),
Ok(n) => {
trace!(parent: node.span(), "read {}B from {}", n, addr);
let mut processed = 0;
let mut left = *carry + n;
// several messages could have been read at once; process the contents of the buffer
loop {
// try to read a single message from the buffer
match self.read_message(*addr, &buffer[processed..processed + left]) {
// a full message was read successfully
Ok(Some((msg, len))) => {
// advance the counters
processed += len;
left -= len;
trace!(
parent: node.span(),
"isolated {}B as a message from {}; {}B left to process",
len,
addr,
left
);
node.known_peers().register_received_message(*addr, len);
node.stats.register_received_message(len);
// send the message for further processing
if message_sender.send(msg).await.is_err() {
error!("the inbound message channel is closed");
return Err(io::ErrorKind::BrokenPipe.into());
}
// if the read is exhausted, reset the carry and return
if left == 0 {
*carry = 0;
return Ok(());
}
}
// the message in the buffer is incomplete
Ok(None) => {
// forbid messages that are larger than the read buffer
if left >= buffer.len() {
error!(parent: node.span(), "a message from {} is too large", addr);
return Err(io::ErrorKind::InvalidData.into());
}
trace!(
parent: node.span(),
"a message from {} is incomplete; carrying {}B over",
addr,
left
);
*carry = left;
// move the leftover bytes to the beginning of the buffer; the next read will append bytes
// starting from where the leftover ones end, allowing the message to be completed
buffer.copy_within(processed..processed + left, 0);
return Ok(());
}
// an erroneous message (e.g. an unexpected zero-length payload)
Err(_) => {
error!(parent: node.span(), "a message from {} is invalid", addr);
return Err(io::ErrorKind::InvalidData.into());
}
}
}
}
// a stream read error
Err(e) => {
error!(parent: node.span(), "can't read from {}: {}", addr, e);
Err(io::ErrorKind::Other.into())
}
}
}
/// Reads a single message from `ConnectionReader`'s buffer; `Ok(None)` indicates that the message is
/// incomplete, i.e. further reads from the stream must be performed in order to produce the whole message.
/// Alongside the message it returns the number of bytes the read message occupied in the buffer. An `Err`
/// returned here will result in the associated connection being dropped.
fn read_message(
&self,
source: SocketAddr,
buffer: &[u8],
) -> io::Result<Option<(Self::Message, usize)>>;
/// Processes an inbound message. Can be used to update state, send replies etc.
#[allow(unused_variables)]
async fn process_message(&self, source: SocketAddr, message: Self::Message) -> io::Result<()> {
// don't do anything by default
Ok(())
}
}
/// An object dedicated to spawning tasks handling inbound messages
/// from new connections; used in the `Reading` protocol.
pub struct ReadingHandler {
sender: mpsc::Sender<ReturnableConnection>,
pub(crate) task: JoinHandle<()>,
}
impl ReadingHandler {
/// Sends a returnable `Connection` to a task spawned by the `ReadingHandler`.
pub async fn send(&self, returnable_conn: ReturnableConnection) {
if self.sender.send(returnable_conn).await.is_err() {
error!("ReadingHandler's Receiver is closed");
}
}
}
impl From<(mpsc::Sender<ReturnableConnection>, JoinHandle<()>)> for ReadingHandler {
fn from((sender, task): (mpsc::Sender<ReturnableConnection>, JoinHandle<()>)) -> Self {
Self { sender, task }
}
}