Flatten back the structure (#837)

* Remove chains. * Move relay clients. * Flatten generic. * Fix fmt.
2026-05-30 22:11:02 +00:00 · 2021-03-23 14:17:33 +01:00
parent 647eb80165
commit acb872fbb0
109 changed files with 87 additions and 86 deletions
@@ -0,0 +1,619 @@
+// Copyright 2019-2021 Parity Technologies (UK) Ltd.
+// This file is part of Parity Bridges Common.
+
+// Parity Bridges Common 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.
+
+// Parity Bridges Common 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 Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
+
+//! The loop basically reads all missing headers and their finality proofs from the source client.
+//! The proof for the best possible header is then submitted to the target node. The only exception
+//! is the mandatory headers, which we always submit to the target node. For such headers, we
+//! assume that the persistent proof either exists, or will eventually become available.
+
+use crate::{FinalityProof, FinalitySyncPipeline, SourceHeader};
+
+use async_trait::async_trait;
+use backoff::backoff::Backoff;
+use futures::{select, Future, FutureExt, Stream, StreamExt};
+use headers_relay::sync_loop_metrics::SyncLoopMetrics;
+use num_traits::{One, Saturating};
+use relay_utils::{
+	metrics::{start as metrics_start, GlobalMetrics, MetricsParams},
+	relay_loop::Client as RelayClient,
+	retry_backoff, FailedClient, MaybeConnectionError,
+};
+use std::{
+	pin::Pin,
+	time::{Duration, Instant},
+};
+
+/// Finality proof synchronization loop parameters.
+#[derive(Debug, Clone)]
+pub struct FinalitySyncParams {
+	/// Interval at which we check updates on both clients. Normally should be larger than
+	/// `min(source_block_time, target_block_time)`.
+	///
+	/// This parameter may be used to limit transactions rate. Increase the value && you'll get
+	/// infrequent updates => sparse headers => potential slow down of bridge applications, but pallet storage
+	/// won't be super large. Decrease the value to near `source_block_time` and you'll get
+	/// transaction for (almost) every block of the source chain => all source headers will be known
+	/// to the target chain => bridge applications will run faster, but pallet storage may explode
+	/// (but if pruning is there, then it's fine).
+	pub tick: Duration,
+	/// Number of finality proofs to keep in internal buffer between loop wakeups.
+	///
+	/// While in "major syncing" state, we still read finality proofs from the stream. They're stored
+	/// in the internal buffer between loop wakeups. When we're close to the tip of the chain, we may
+	/// meet finality delays if headers are not finalized frequently. So instead of waiting for next
+	/// finality proof to appear in the stream, we may use existing proof from that buffer.
+	pub recent_finality_proofs_limit: usize,
+	/// Timeout before we treat our transactions as lost and restart the whole sync process.
+	pub stall_timeout: Duration,
+}
+
+/// Source client used in finality synchronization loop.
+#[async_trait]
+pub trait SourceClient<P: FinalitySyncPipeline>: RelayClient {
+	/// Stream of new finality proofs. The stream is allowed to miss proofs for some
+	/// headers, even if those headers are mandatory.
+	type FinalityProofsStream: Stream<Item = P::FinalityProof>;
+
+	/// Get best finalized block number.
+	async fn best_finalized_block_number(&self) -> Result<P::Number, Self::Error>;
+
+	/// Get canonical header and its finality proof by number.
+	async fn header_and_finality_proof(
+		&self,
+		number: P::Number,
+	) -> Result<(P::Header, Option<P::FinalityProof>), Self::Error>;
+
+	/// Subscribe to new finality proofs.
+	async fn finality_proofs(&self) -> Result<Self::FinalityProofsStream, Self::Error>;
+}
+
+/// Target client used in finality synchronization loop.
+#[async_trait]
+pub trait TargetClient<P: FinalitySyncPipeline>: RelayClient {
+	/// Get best finalized source block number.
+	async fn best_finalized_source_block_number(&self) -> Result<P::Number, Self::Error>;
+
+	/// Submit header finality proof.
+	async fn submit_finality_proof(&self, header: P::Header, proof: P::FinalityProof) -> Result<(), Self::Error>;
+}
+
+/// Run finality proofs synchronization loop.
+pub async fn run<P: FinalitySyncPipeline>(
+	source_client: impl SourceClient<P>,
+	target_client: impl TargetClient<P>,
+	sync_params: FinalitySyncParams,
+	metrics_params: Option<MetricsParams>,
+	exit_signal: impl Future<Output = ()>,
+) {
+	let exit_signal = exit_signal.shared();
+
+	let metrics_global = GlobalMetrics::default();
+	let metrics_sync = SyncLoopMetrics::default();
+	let metrics_enabled = metrics_params.is_some();
+	metrics_start(
+		format!("{}_to_{}_Sync", P::SOURCE_NAME, P::TARGET_NAME),
+		metrics_params,
+		&metrics_global,
+		&metrics_sync,
+	);
+
+	relay_utils::relay_loop::run(
+		relay_utils::relay_loop::RECONNECT_DELAY,
+		source_client,
+		target_client,
+		|source_client, target_client| {
+			run_until_connection_lost(
+				source_client,
+				target_client,
+				sync_params.clone(),
+				if metrics_enabled {
+					Some(metrics_global.clone())
+				} else {
+					None
+				},
+				if metrics_enabled {
+					Some(metrics_sync.clone())
+				} else {
+					None
+				},
+				exit_signal.clone(),
+			)
+		},
+	)
+	.await;
+}
+
+/// Unjustified headers container. Ordered by header number.
+pub(crate) type UnjustifiedHeaders<H> = Vec<H>;
+/// Finality proofs container. Ordered by target header number.
+pub(crate) type FinalityProofs<P> = Vec<(
+	<P as FinalitySyncPipeline>::Number,
+	<P as FinalitySyncPipeline>::FinalityProof,
+)>;
+/// Reference to finality proofs container.
+pub(crate) type FinalityProofsRef<'a, P> = &'a [(
+	<P as FinalitySyncPipeline>::Number,
+	<P as FinalitySyncPipeline>::FinalityProof,
+)];
+
+/// Error that may happen inside finality synchronization loop.
+#[derive(Debug)]
+pub(crate) enum Error<P: FinalitySyncPipeline, SourceError, TargetError> {
+	/// Source client request has failed with given error.
+	Source(SourceError),
+	/// Target client request has failed with given error.
+	Target(TargetError),
+	/// Finality proof for mandatory header is missing from the source node.
+	MissingMandatoryFinalityProof(P::Number),
+	/// The synchronization has stalled.
+	Stalled,
+}
+
+impl<P, SourceError, TargetError> Error<P, SourceError, TargetError>
+where
+	P: FinalitySyncPipeline,
+	SourceError: MaybeConnectionError,
+	TargetError: MaybeConnectionError,
+{
+	fn fail_if_connection_error(&self) -> Result<(), FailedClient> {
+		match *self {
+			Error::Source(ref error) if error.is_connection_error() => Err(FailedClient::Source),
+			Error::Target(ref error) if error.is_connection_error() => Err(FailedClient::Target),
+			Error::Stalled => Err(FailedClient::Both),
+			_ => Ok(()),
+		}
+	}
+}
+
+/// Information about transaction that we have submitted.
+#[derive(Debug, Clone)]
+struct Transaction<Number> {
+	/// Time when we have submitted this transaction.
+	pub time: Instant,
+	/// The number of the header we have submitted.
+	pub submitted_header_number: Number,
+}
+
+/// Finality proofs stream that may be restarted.
+pub(crate) struct RestartableFinalityProofsStream<S> {
+	/// Flag that the stream needs to be restarted.
+	pub(crate) needs_restart: bool,
+	/// The stream itself.
+	stream: Pin<Box<S>>,
+}
+
+#[cfg(test)]
+impl<S> From<S> for RestartableFinalityProofsStream<S> {
+	fn from(stream: S) -> Self {
+		RestartableFinalityProofsStream {
+			needs_restart: false,
+			stream: Box::pin(stream),
+		}
+	}
+}
+
+/// Finality synchronization loop state.
+struct FinalityLoopState<'a, P: FinalitySyncPipeline, FinalityProofsStream> {
+	/// Synchronization loop progress.
+	progress: &'a mut (Instant, Option<P::Number>),
+	/// Finality proofs stream.
+	finality_proofs_stream: &'a mut RestartableFinalityProofsStream<FinalityProofsStream>,
+	/// Recent finality proofs that we have read from the stream.
+	recent_finality_proofs: &'a mut FinalityProofs<P>,
+	/// Last transaction that we have submitted to the target node.
+	last_transaction: Option<Transaction<P::Number>>,
+}
+
+async fn run_until_connection_lost<P: FinalitySyncPipeline>(
+	source_client: impl SourceClient<P>,
+	target_client: impl TargetClient<P>,
+	sync_params: FinalitySyncParams,
+	metrics_global: Option<GlobalMetrics>,
+	metrics_sync: Option<SyncLoopMetrics>,
+	exit_signal: impl Future<Output = ()>,
+) -> Result<(), FailedClient> {
+	let restart_finality_proofs_stream = || async {
+		source_client.finality_proofs().await.map_err(|error| {
+			log::error!(
+				target: "bridge",
+				"Failed to subscribe to {} justifications: {:?}. Going to reconnect",
+				P::SOURCE_NAME,
+				error,
+			);
+
+			FailedClient::Source
+		})
+	};
+
+	let exit_signal = exit_signal.fuse();
+	futures::pin_mut!(exit_signal);
+
+	let mut finality_proofs_stream = RestartableFinalityProofsStream {
+		needs_restart: false,
+		stream: Box::pin(restart_finality_proofs_stream().await?),
+	};
+	let mut recent_finality_proofs = Vec::new();
+
+	let mut progress = (Instant::now(), None);
+	let mut retry_backoff = retry_backoff();
+	let mut last_transaction = None;
+
+	loop {
+		// run loop iteration
+		let iteration_result = run_loop_iteration(
+			&source_client,
+			&target_client,
+			FinalityLoopState {
+				progress: &mut progress,
+				finality_proofs_stream: &mut finality_proofs_stream,
+				recent_finality_proofs: &mut recent_finality_proofs,
+				last_transaction: last_transaction.clone(),
+			},
+			&sync_params,
+			&metrics_sync,
+		)
+		.await;
+
+		// update global metrics
+		if let Some(ref metrics_global) = metrics_global {
+			metrics_global.update().await;
+		}
+
+		// deal with errors
+		let next_tick = match iteration_result {
+			Ok(updated_last_transaction) => {
+				last_transaction = updated_last_transaction;
+				retry_backoff.reset();
+				sync_params.tick
+			}
+			Err(error) => {
+				log::error!(target: "bridge", "Finality sync loop iteration has failed with error: {:?}", error);
+				error.fail_if_connection_error()?;
+				retry_backoff
+					.next_backoff()
+					.unwrap_or(relay_utils::relay_loop::RECONNECT_DELAY)
+			}
+		};
+		if finality_proofs_stream.needs_restart {
+			log::warn!(target: "bridge", "{} finality proofs stream is being restarted", P::SOURCE_NAME);
+
+			finality_proofs_stream.needs_restart = false;
+			finality_proofs_stream.stream = Box::pin(restart_finality_proofs_stream().await?);
+		}
+
+		// wait till exit signal, or new source block
+		select! {
+			_ = async_std::task::sleep(next_tick).fuse() => {},
+			_ = exit_signal => return Ok(()),
+		}
+	}
+}
+
+async fn run_loop_iteration<P, SC, TC>(
+	source_client: &SC,
+	target_client: &TC,
+	state: FinalityLoopState<'_, P, SC::FinalityProofsStream>,
+	sync_params: &FinalitySyncParams,
+	metrics_sync: &Option<SyncLoopMetrics>,
+) -> Result<Option<Transaction<P::Number>>, Error<P, SC::Error, TC::Error>>
+where
+	P: FinalitySyncPipeline,
+	SC: SourceClient<P>,
+	TC: TargetClient<P>,
+{
+	// read best source headers ids from source and target nodes
+	let best_number_at_source = source_client
+		.best_finalized_block_number()
+		.await
+		.map_err(Error::Source)?;
+	let best_number_at_target = target_client
+		.best_finalized_source_block_number()
+		.await
+		.map_err(Error::Target)?;
+	if let Some(ref metrics_sync) = *metrics_sync {
+		metrics_sync.update_best_block_at_source(best_number_at_source);
+		metrics_sync.update_best_block_at_target(best_number_at_target);
+	}
+	*state.progress = print_sync_progress::<P>(*state.progress, best_number_at_source, best_number_at_target);
+
+	// if we have already submitted header, then we just need to wait for it
+	// if we're waiting too much, then we believe our transaction has been lost and restart sync
+	if let Some(last_transaction) = state.last_transaction {
+		if best_number_at_target >= last_transaction.submitted_header_number {
+			// transaction has been mined && we can continue
+		} else if last_transaction.time.elapsed() > sync_params.stall_timeout {
+			log::error!(
+				target: "bridge",
+				"Finality synchronization from {} to {} has stalled. Going to restart",
+				P::SOURCE_NAME,
+				P::TARGET_NAME,
+			);
+
+			return Err(Error::Stalled);
+		} else {
+			return Ok(Some(last_transaction));
+		}
+	}
+
+	// submit new header if we have something new
+	match select_header_to_submit(
+		source_client,
+		target_client,
+		state.finality_proofs_stream,
+		state.recent_finality_proofs,
+		best_number_at_source,
+		best_number_at_target,
+		sync_params,
+	)
+	.await?
+	{
+		Some((header, justification)) => {
+			let new_transaction = Transaction {
+				time: Instant::now(),
+				submitted_header_number: header.number(),
+			};
+
+			log::debug!(
+				target: "bridge",
+				"Going to submit finality proof of {} header #{:?} to {}",
+				P::SOURCE_NAME,
+				new_transaction.submitted_header_number,
+				P::TARGET_NAME,
+			);
+
+			target_client
+				.submit_finality_proof(header, justification)
+				.await
+				.map_err(Error::Target)?;
+			Ok(Some(new_transaction))
+		}
+		None => Ok(None),
+	}
+}
+
+async fn select_header_to_submit<P, SC, TC>(
+	source_client: &SC,
+	target_client: &TC,
+	finality_proofs_stream: &mut RestartableFinalityProofsStream<SC::FinalityProofsStream>,
+	recent_finality_proofs: &mut FinalityProofs<P>,
+	best_number_at_source: P::Number,
+	best_number_at_target: P::Number,
+	sync_params: &FinalitySyncParams,
+) -> Result<Option<(P::Header, P::FinalityProof)>, Error<P, SC::Error, TC::Error>>
+where
+	P: FinalitySyncPipeline,
+	SC: SourceClient<P>,
+	TC: TargetClient<P>,
+{
+	// to see that the loop is progressing
+	log::trace!(
+		target: "bridge",
+		"Considering range of headers ({:?}; {:?}]",
+		best_number_at_target,
+		best_number_at_source,
+	);
+
+	// read missing headers. if we see that the header schedules GRANDPA change, we need to
+	// submit this header
+	let selected_finality_proof = read_missing_headers::<P, SC, TC>(
+		source_client,
+		target_client,
+		best_number_at_source,
+		best_number_at_target,
+	)
+	.await?;
+	let (mut unjustified_headers, mut selected_finality_proof) = match selected_finality_proof {
+		SelectedFinalityProof::Mandatory(header, finality_proof) => return Ok(Some((header, finality_proof))),
+		SelectedFinalityProof::Regular(unjustified_headers, header, finality_proof) => {
+			(unjustified_headers, Some((header, finality_proof)))
+		}
+		SelectedFinalityProof::None(unjustified_headers) => (unjustified_headers, None),
+	};
+
+	// all headers that are missing from the target client are non-mandatory
+	// => even if we have already selected some header and its persistent finality proof,
+	// we may try to select better header by reading non-persistent proofs from the stream
+	read_finality_proofs_from_stream::<P, _>(finality_proofs_stream, recent_finality_proofs);
+	selected_finality_proof = select_better_recent_finality_proof::<P>(
+		recent_finality_proofs,
+		&mut unjustified_headers,
+		selected_finality_proof,
+	);
+
+	// remove obsolete 'recent' finality proofs + keep its size under certain limit
+	let oldest_finality_proof_to_keep = selected_finality_proof
+		.as_ref()
+		.map(|(header, _)| header.number())
+		.unwrap_or(best_number_at_target);
+	prune_recent_finality_proofs::<P>(
+		oldest_finality_proof_to_keep,
+		recent_finality_proofs,
+		sync_params.recent_finality_proofs_limit,
+	);
+
+	Ok(selected_finality_proof)
+}
+
+/// Finality proof that has been selected by the `read_missing_headers` function.
+pub(crate) enum SelectedFinalityProof<Header, FinalityProof> {
+	/// Mandatory header and its proof has been selected. We shall submit proof for this header.
+	Mandatory(Header, FinalityProof),
+	/// Regular header and its proof has been selected. We may submit this proof, or proof for
+	/// some better header.
+	Regular(UnjustifiedHeaders<Header>, Header, FinalityProof),
+	/// We haven't found any missing header with persistent proof at the target client.
+	None(UnjustifiedHeaders<Header>),
+}
+
+/// Read missing headers and their persistent finality proofs from the target client.
+///
+/// If we have found some header with known proof, it is returned.
+/// Otherwise, `SelectedFinalityProof::None` is returned.
+///
+/// Unless we have found mandatory header, all missing headers are collected and returned.
+pub(crate) async fn read_missing_headers<P: FinalitySyncPipeline, SC: SourceClient<P>, TC: TargetClient<P>>(
+	source_client: &SC,
+	_target_client: &TC,
+	best_number_at_source: P::Number,
+	best_number_at_target: P::Number,
+) -> Result<SelectedFinalityProof<P::Header, P::FinalityProof>, Error<P, SC::Error, TC::Error>> {
+	let mut unjustified_headers = Vec::new();
+	let mut selected_finality_proof = None;
+	let mut header_number = best_number_at_target + One::one();
+	while header_number <= best_number_at_source {
+		let (header, finality_proof) = source_client
+			.header_and_finality_proof(header_number)
+			.await
+			.map_err(Error::Source)?;
+		let is_mandatory = header.is_mandatory();
+
+		match (is_mandatory, finality_proof) {
+			(true, Some(finality_proof)) => {
+				log::trace!(target: "bridge", "Header {:?} is mandatory", header_number);
+				return Ok(SelectedFinalityProof::Mandatory(header, finality_proof));
+			}
+			(true, None) => return Err(Error::MissingMandatoryFinalityProof(header.number())),
+			(false, Some(finality_proof)) => {
+				log::trace!(target: "bridge", "Header {:?} has persistent finality proof", header_number);
+				unjustified_headers.clear();
+				selected_finality_proof = Some((header, finality_proof));
+			}
+			(false, None) => {
+				unjustified_headers.push(header);
+			}
+		}
+
+		header_number = header_number + One::one();
+	}
+
+	Ok(match selected_finality_proof {
+		Some((header, proof)) => SelectedFinalityProof::Regular(unjustified_headers, header, proof),
+		None => SelectedFinalityProof::None(unjustified_headers),
+	})
+}
+
+/// Read finality proofs from the stream.
+pub(crate) fn read_finality_proofs_from_stream<P: FinalitySyncPipeline, FPS: Stream<Item = P::FinalityProof>>(
+	finality_proofs_stream: &mut RestartableFinalityProofsStream<FPS>,
+	recent_finality_proofs: &mut FinalityProofs<P>,
+) {
+	loop {
+		let next_proof = finality_proofs_stream.stream.next();
+		let finality_proof = match next_proof.now_or_never() {
+			Some(Some(finality_proof)) => finality_proof,
+			Some(None) => {
+				finality_proofs_stream.needs_restart = true;
+				break;
+			}
+			None => break,
+		};
+
+		recent_finality_proofs.push((finality_proof.target_header_number(), finality_proof));
+	}
+}
+
+/// Try to select better header and its proof, given finality proofs that we
+/// have recently read from the stream.
+pub(crate) fn select_better_recent_finality_proof<P: FinalitySyncPipeline>(
+	recent_finality_proofs: FinalityProofsRef<P>,
+	unjustified_headers: &mut UnjustifiedHeaders<P::Header>,
+	selected_finality_proof: Option<(P::Header, P::FinalityProof)>,
+) -> Option<(P::Header, P::FinalityProof)> {
+	if unjustified_headers.is_empty() || recent_finality_proofs.is_empty() {
+		return selected_finality_proof;
+	}
+
+	const NOT_EMPTY_PROOF: &str = "we have checked that the vec is not empty; qed";
+
+	// we need proofs for headers in range unjustified_range_begin..=unjustified_range_end
+	let unjustified_range_begin = unjustified_headers.first().expect(NOT_EMPTY_PROOF).number();
+	let unjustified_range_end = unjustified_headers.last().expect(NOT_EMPTY_PROOF).number();
+
+	// we have proofs for headers in range buffered_range_begin..=buffered_range_end
+	let buffered_range_begin = recent_finality_proofs.first().expect(NOT_EMPTY_PROOF).0;
+	let buffered_range_end = recent_finality_proofs.last().expect(NOT_EMPTY_PROOF).0;
+
+	// we have two ranges => find intersection
+	let intersection_begin = std::cmp::max(unjustified_range_begin, buffered_range_begin);
+	let intersection_end = std::cmp::min(unjustified_range_end, buffered_range_end);
+	let intersection = intersection_begin..=intersection_end;
+
+	// find last proof from intersection
+	let selected_finality_proof_index = recent_finality_proofs
+		.binary_search_by_key(intersection.end(), |(number, _)| *number)
+		.unwrap_or_else(|index| index.saturating_sub(1));
+	let (selected_header_number, finality_proof) = &recent_finality_proofs[selected_finality_proof_index];
+	if !intersection.contains(selected_header_number) {
+		return selected_finality_proof;
+	}
+
+	// now remove all obsolete headers and extract selected header
+	let selected_header_position = unjustified_headers
+		.binary_search_by_key(selected_header_number, |header| header.number())
+		.expect("unjustified_headers contain all headers from intersection; qed");
+	let selected_header = unjustified_headers.swap_remove(selected_header_position);
+	Some((selected_header, finality_proof.clone()))
+}
+
+pub(crate) fn prune_recent_finality_proofs<P: FinalitySyncPipeline>(
+	justified_header_number: P::Number,
+	recent_finality_proofs: &mut FinalityProofs<P>,
+	recent_finality_proofs_limit: usize,
+) {
+	let position =
+		recent_finality_proofs.binary_search_by_key(&justified_header_number, |(header_number, _)| *header_number);
+
+	// remove all obsolete elements
+	*recent_finality_proofs = recent_finality_proofs.split_off(
+		position
+			.map(|position| position + 1)
+			.unwrap_or_else(|position| position),
+	);
+
+	// now - limit vec by size
+	let split_index = recent_finality_proofs
+		.len()
+		.saturating_sub(recent_finality_proofs_limit);
+	*recent_finality_proofs = recent_finality_proofs.split_off(split_index);
+}
+
+fn print_sync_progress<P: FinalitySyncPipeline>(
+	progress_context: (Instant, Option<P::Number>),
+	best_number_at_source: P::Number,
+	best_number_at_target: P::Number,
+) -> (Instant, Option<P::Number>) {
+	let (prev_time, prev_best_number_at_target) = progress_context;
+	let now = Instant::now();
+
+	let need_update = now - prev_time > Duration::from_secs(10)
+		|| prev_best_number_at_target
+			.map(|prev_best_number_at_target| {
+				best_number_at_target.saturating_sub(prev_best_number_at_target) > 10.into()
+			})
+			.unwrap_or(true);
+
+	if !need_update {
+		return (prev_time, prev_best_number_at_target);
+	}
+
+	log::info!(
+		target: "bridge",
+		"Synced {:?} of {:?} headers",
+		best_number_at_target,
+		best_number_at_source,
+	);
+	(now, Some(best_number_at_target))
+}