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finality_relay/
lib.rs

1// Copyright 2019-2021 Parity Technologies (UK) Ltd.
2// This file is part of Parity Bridges Common.
3
4// Parity Bridges Common is free software: you can redistribute it and/or modify
5// it under the terms of the GNU General Public License as published by
6// the Free Software Foundation, either version 3 of the License, or
7// (at your option) any later version.
8
9// Parity Bridges Common is distributed in the hope that it will be useful,
10// but WITHOUT ANY WARRANTY; without even the implied warranty of
11// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12// GNU General Public License for more details.
13
14// You should have received a copy of the GNU General Public License
15// along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
16
17//! This crate has single entrypoint to run synchronization loop that is built around finality
18//! proofs, as opposed to headers synchronization loop, which is built around headers. The headers
19//! are still submitted to the target node, but are treated as auxiliary data as we are not trying
20//! to submit all source headers to the target node.
21
22pub use crate::{
23	base::{FinalityPipeline, SourceClientBase},
24	finality_loop::{
25		metrics_prefix, run, FinalitySyncParams, HeadersToRelay, SourceClient, TargetClient,
26	},
27	finality_proofs::{FinalityProofsBuf, FinalityProofsStream},
28	sync_loop_metrics::SyncLoopMetrics,
29};
30
31use bp_header_chain::ConsensusLogReader;
32use relay_utils::{FailedClient, MaybeConnectionError};
33use std::fmt::Debug;
34
35mod base;
36mod finality_loop;
37mod finality_proofs;
38mod headers;
39mod mock;
40mod sync_loop_metrics;
41
42/// Finality proofs synchronization pipeline.
43pub trait FinalitySyncPipeline: FinalityPipeline {
44	/// A reader that can extract the consensus log from the header digest and interpret it.
45	type ConsensusLogReader: ConsensusLogReader;
46	/// Type of header that we're syncing.
47	type Header: SourceHeader<Self::Hash, Self::Number, Self::ConsensusLogReader>;
48}
49
50/// Header that we're receiving from source node.
51pub trait SourceHeader<Hash, Number, Reader>: Clone + Debug + PartialEq + Send + Sync {
52	/// Returns hash of header.
53	fn hash(&self) -> Hash;
54	/// Returns number of header.
55	fn number(&self) -> Number;
56	/// Returns true if this header needs to be submitted to target node.
57	fn is_mandatory(&self) -> bool;
58}
59
60/// Error that may happen inside finality synchronization loop.
61#[derive(Debug)]
62enum Error<P: FinalitySyncPipeline, SourceError, TargetError> {
63	/// Source client request has failed with given error.
64	Source(SourceError),
65	/// Target client request has failed with given error.
66	Target(TargetError),
67	/// Finality proof for mandatory header is missing from the source node.
68	MissingMandatoryFinalityProof(P::Number),
69	/// `submit_finality_proof` transaction failed
70	ProofSubmissionTxFailed {
71		#[allow(dead_code)]
72		submitted_number: P::Number,
73		#[allow(dead_code)]
74		best_number_at_target: P::Number,
75	},
76	/// `submit_finality_proof` transaction lost
77	ProofSubmissionTxLost,
78}
79
80impl<P, SourceError, TargetError> Error<P, SourceError, TargetError>
81where
82	P: FinalitySyncPipeline,
83	SourceError: MaybeConnectionError,
84	TargetError: MaybeConnectionError,
85{
86	fn fail_if_connection_error(&self) -> Result<(), FailedClient> {
87		match *self {
88			Error::Source(ref error) if error.is_connection_error() => Err(FailedClient::Source),
89			Error::Target(ref error) if error.is_connection_error() => Err(FailedClient::Target),
90			_ => Ok(()),
91		}
92	}
93}