Implement Network Bridge (#1280)

* network bridge skeleton * move some primitives around and add debug impls * protocol registration glue & abstract network interface * add send_msgs to subsystemctx * select logic * transform different events into actions and handle * implement remaining network bridge state machine * start test skeleton * make network methods asynchronous * extract subsystem out to subsystem crate * port over overseer to subsystem context trait * fix minimal example * fix overseer doc test * update network-bridge crate * write a subsystem test-helpers crate * write a network test helper for network-bridge * set up (broken) view test * Revamp network to be more async-friendly and not require Sync * fix spacing * fix test compilation * insert side-channel for actions * Add some more message types to AllMessages * introduce a test harness * add some tests * ensure service compiles and passes tests * fix typo * fix service-new compilation * Subsystem test helpers send messages synchronously * remove smelly action inspector * remove superfluous let binding * fix warnings * Update node/network/bridge/src/lib.rs Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com> * fix compilation Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>
2026-06-15 12:41:07 +00:00 · 2020-06-30 11:21:40 -04:00
parent 90de55918a
commit d16e7485d4
16 changed files with 1533 additions and 169 deletions
@@ -0,0 +1,150 @@
+// Copyright 2017-2020 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot 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.
+
+// Polkadot 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 Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Subsystem trait definitions and message types.
+//!
+//! Node-side logic for Polkadot is mostly comprised of Subsystems, which are discrete components
+//! that communicate via message-passing. They are coordinated by an overseer, provided by a
+//! separate crate.
+
+use std::pin::Pin;
+
+use futures::prelude::*;
+use futures::channel::{mpsc, oneshot};
+use futures::future::BoxFuture;
+
+use polkadot_primitives::Hash;
+use async_trait::async_trait;
+
+use crate::messages::AllMessages;
+
+pub mod messages;
+
+/// Signals sent by an overseer to a subsystem.
+#[derive(PartialEq, Clone, Debug)]
+pub enum OverseerSignal {
+	/// `Subsystem` should start working on block-based work, given by the relay-chain block hash.
+	StartWork(Hash),
+	/// `Subsystem` should stop working on block-based work specified by the relay-chain block hash.
+	StopWork(Hash),
+	/// Conclude the work of the `Overseer` and all `Subsystem`s.
+	Conclude,
+}
+
+/// A message type that a subsystem receives from an overseer.
+/// It wraps signals from an overseer and messages that are circulating
+/// between subsystems.
+///
+/// It is generic over over the message type `M` that a particular `Subsystem` may use.
+#[derive(Debug)]
+pub enum FromOverseer<M> {
+	/// Signal from the `Overseer`.
+	Signal(OverseerSignal),
+
+	/// Some other `Subsystem`'s message.
+	Communication {
+		msg: M,
+	},
+}
+
+/// An error type that describes faults that may happen
+///
+/// These are:
+///   * Channels being closed
+///   * Subsystems dying when they are not expected to
+///   * Subsystems not dying when they are told to die
+///   * etc.
+#[derive(Debug)]
+pub struct SubsystemError;
+
+impl From<mpsc::SendError> for SubsystemError {
+	fn from(_: mpsc::SendError) -> Self {
+		Self
+	}
+}
+
+impl From<oneshot::Canceled> for SubsystemError {
+	fn from(_: oneshot::Canceled) -> Self {
+		Self
+	}
+}
+
+impl From<futures::task::SpawnError> for SubsystemError {
+    fn from(_: futures::task::SpawnError) -> Self {
+		Self
+    }
+}
+
+impl From<std::convert::Infallible> for SubsystemError {
+	fn from(e: std::convert::Infallible) -> Self {
+		match e {}
+	}
+}
+
+/// An asynchronous subsystem task..
+///
+/// In essence it's just a newtype wrapping a `BoxFuture`.
+pub struct SpawnedSubsystem(pub BoxFuture<'static, ()>);
+
+/// A `Result` type that wraps [`SubsystemError`].
+///
+/// [`SubsystemError`]: struct.SubsystemError.html
+pub type SubsystemResult<T> = Result<T, SubsystemError>;
+
+/// A context type that is given to the [`Subsystem`] upon spawning.
+/// It can be used by [`Subsystem`] to communicate with other [`Subsystem`]s
+/// or spawn jobs.
+///
+/// [`Overseer`]: struct.Overseer.html
+/// [`SubsystemJob`]: trait.SubsystemJob.html
+#[async_trait]
+pub trait SubsystemContext: Send + 'static {
+	/// The message type of this context. Subsystems launched with this context will expect
+	/// to receive messages of this type.
+	type Message: Send;
+
+	/// Try to asynchronously receive a message.
+	///
+	/// This has to be used with caution, if you loop over this without
+	/// using `pending!()` macro you will end up with a busy loop!
+	async fn try_recv(&mut self) -> Result<Option<FromOverseer<Self::Message>>, ()>;
+
+	/// Receive a message.
+	async fn recv(&mut self) -> SubsystemResult<FromOverseer<Self::Message>>;
+
+	/// Spawn a child task on the executor.
+	async fn spawn(&mut self, s: Pin<Box<dyn Future<Output = ()> + Send>>) -> SubsystemResult<()>;
+
+	/// Send a direct message to some other `Subsystem`, routed based on message type.
+	async fn send_message(&mut self, msg: AllMessages) -> SubsystemResult<()>;
+
+	/// Send multiple direct messages to other `Subsystem`s, routed based on message type.
+	async fn send_messages<T>(&mut self, msgs: T) -> SubsystemResult<()>
+		where T: IntoIterator<Item = AllMessages> + Send, T::IntoIter: Send;
+}
+
+/// A trait that describes the [`Subsystem`]s that can run on the [`Overseer`].
+///
+/// It is generic over the message type circulating in the system.
+/// The idea that we want some type contaning persistent state that
+/// can spawn actually running subsystems when asked to.
+///
+/// [`Overseer`]: struct.Overseer.html
+/// [`Subsystem`]: trait.Subsystem.html
+pub trait Subsystem<C: SubsystemContext> {
+	/// Start this `Subsystem` and return `SpawnedSubsystem`.
+	fn start(&mut self, ctx: C) -> SpawnedSubsystem;
+}