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// This file is part of Substrate.
// Copyright (C) Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
//! Provides the `buffered_link` utility.
//!
//! The buffered link is a channel that allows buffering the method calls on `Link`.
//!
//! # Example
//!
//! ```
//! use sc_consensus::import_queue::Link;
//! # use sc_consensus::import_queue::buffered_link::buffered_link;
//! # use sp_test_primitives::Block;
//! # struct DummyLink; impl Link<Block> for DummyLink {}
//! # let my_link = DummyLink;
//! let (mut tx, mut rx) = buffered_link::<Block>(100_000);
//! tx.blocks_processed(0, 0, vec![]);
//!
//! // Calls `my_link.blocks_processed(0, 0, vec![])` when polled.
//! let _fut = futures::future::poll_fn(move |cx| {
//! rx.poll_actions(cx, &my_link).unwrap();
//! std::task::Poll::Pending::<()>
//! });
//! ```
use crate::import_queue::{Link, RuntimeOrigin};
use futures::prelude::*;
use sc_utils::mpsc::{tracing_unbounded, TracingUnboundedReceiver, TracingUnboundedSender};
use sp_runtime::traits::{Block as BlockT, NumberFor};
use std::{
pin::Pin,
task::{Context, Poll},
};
use super::BlockImportResult;
/// Wraps around an unbounded channel from the `futures` crate. The sender implements `Link` and
/// can be used to buffer commands, and the receiver can be used to poll said commands and transfer
/// them to another link. `queue_size_warning` sets the warning threshold of the channel queue size.
pub fn buffered_link<B: BlockT>(
queue_size_warning: usize,
) -> (BufferedLinkSender<B>, BufferedLinkReceiver<B>) {
let (tx, rx) = tracing_unbounded("mpsc_buffered_link", queue_size_warning);
let tx = BufferedLinkSender { tx };
let rx = BufferedLinkReceiver { rx: rx.fuse() };
(tx, rx)
}
/// See [`buffered_link`].
pub struct BufferedLinkSender<B: BlockT> {
tx: TracingUnboundedSender<BlockImportWorkerMsg<B>>,
}
impl<B: BlockT> BufferedLinkSender<B> {
/// Returns true if the sender points to nowhere.
///
/// Once `true` is returned, it is pointless to use the sender anymore.
pub fn is_closed(&self) -> bool {
self.tx.is_closed()
}
}
impl<B: BlockT> Clone for BufferedLinkSender<B> {
fn clone(&self) -> Self {
BufferedLinkSender { tx: self.tx.clone() }
}
}
/// Internal buffered message.
pub enum BlockImportWorkerMsg<B: BlockT> {
BlocksProcessed(usize, usize, Vec<(BlockImportResult<B>, B::Hash)>),
JustificationImported(RuntimeOrigin, B::Hash, NumberFor<B>, bool),
RequestJustification(B::Hash, NumberFor<B>),
}
impl<B: BlockT> Link<B> for BufferedLinkSender<B> {
fn blocks_processed(
&self,
imported: usize,
count: usize,
results: Vec<(BlockImportResult<B>, B::Hash)>,
) {
let _ = self
.tx
.unbounded_send(BlockImportWorkerMsg::BlocksProcessed(imported, count, results));
}
fn justification_imported(
&self,
who: RuntimeOrigin,
hash: &B::Hash,
number: NumberFor<B>,
success: bool,
) {
let msg = BlockImportWorkerMsg::JustificationImported(who, *hash, number, success);
let _ = self.tx.unbounded_send(msg);
}
fn request_justification(&self, hash: &B::Hash, number: NumberFor<B>) {
let _ = self
.tx
.unbounded_send(BlockImportWorkerMsg::RequestJustification(*hash, number));
}
}
/// See [`buffered_link`].
pub struct BufferedLinkReceiver<B: BlockT> {
rx: stream::Fuse<TracingUnboundedReceiver<BlockImportWorkerMsg<B>>>,
}
impl<B: BlockT> BufferedLinkReceiver<B> {
/// Send action for the synchronization to perform.
pub fn send_actions(&mut self, msg: BlockImportWorkerMsg<B>, link: &dyn Link<B>) {
match msg {
BlockImportWorkerMsg::BlocksProcessed(imported, count, results) =>
link.blocks_processed(imported, count, results),
BlockImportWorkerMsg::JustificationImported(who, hash, number, success) =>
link.justification_imported(who, &hash, number, success),
BlockImportWorkerMsg::RequestJustification(hash, number) =>
link.request_justification(&hash, number),
}
}
/// Polls for the buffered link actions. Any enqueued action will be propagated to the link
/// passed as parameter.
///
/// This method should behave in a way similar to `Future::poll`. It can register the current
/// task and notify later when more actions are ready to be polled. To continue the comparison,
/// it is as if this method always returned `Poll::Pending`.
///
/// Returns an error if the corresponding [`BufferedLinkSender`] has been closed.
pub fn poll_actions(&mut self, cx: &mut Context, link: &dyn Link<B>) -> Result<(), ()> {
loop {
let msg = match Stream::poll_next(Pin::new(&mut self.rx), cx) {
Poll::Ready(Some(msg)) => msg,
Poll::Ready(None) => break Err(()),
Poll::Pending => break Ok(()),
};
self.send_actions(msg, link);
}
}
/// Poll next element from import queue and send the corresponding action command over the link.
pub async fn next_action(&mut self, link: &dyn Link<B>) -> Result<(), ()> {
if let Some(msg) = self.rx.next().await {
self.send_actions(msg, link);
return Ok(())
}
Err(())
}
/// Close the channel.
pub fn close(&mut self) -> bool {
self.rx.get_mut().close()
}
}
#[cfg(test)]
mod tests {
use sp_test_primitives::Block;
#[test]
fn is_closed() {
let (tx, rx) = super::buffered_link::<Block>(1);
assert!(!tx.is_closed());
drop(rx);
assert!(tx.is_closed());
}
}