polkadot_node_core_chain_api/
lib.rs

1// Copyright (C) Parity Technologies (UK) Ltd.
2// This file is part of Polkadot.
3
4// Polkadot 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// Polkadot 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 Polkadot.  If not, see <http://www.gnu.org/licenses/>.
16
17//! Implements the Chain API Subsystem
18//!
19//! Provides access to the chain data. Every request may return an error.
20//! At the moment, the implementation requires `Client` to implement `HeaderBackend`,
21//! we may add more bounds in the future if we will need e.g. block bodies.
22//!
23//! Supported requests:
24//! * Block hash to number
25//! * Block hash to header
26//! * Block weight (cumulative)
27//! * Finalized block number to hash
28//! * Last finalized block number
29//! * Ancestors
30
31#![deny(unused_crate_dependencies, unused_results)]
32#![warn(missing_docs)]
33
34use std::sync::Arc;
35
36use futures::prelude::*;
37use sc_client_api::AuxStore;
38
39use futures::stream::StreamExt;
40use polkadot_node_subsystem::{
41	messages::ChainApiMessage, overseer, FromOrchestra, OverseerSignal, SpawnedSubsystem,
42	SubsystemError, SubsystemResult,
43};
44use polkadot_node_subsystem_types::ChainApiBackend;
45
46mod metrics;
47use self::metrics::Metrics;
48
49#[cfg(test)]
50mod tests;
51
52const LOG_TARGET: &str = "parachain::chain-api";
53
54/// The Chain API Subsystem implementation.
55pub struct ChainApiSubsystem<Client> {
56	client: Arc<Client>,
57	metrics: Metrics,
58}
59
60impl<Client> ChainApiSubsystem<Client> {
61	/// Create a new Chain API subsystem with the given client.
62	pub fn new(client: Arc<Client>, metrics: Metrics) -> Self {
63		ChainApiSubsystem { client, metrics }
64	}
65}
66
67#[overseer::subsystem(ChainApi, error = SubsystemError, prefix = self::overseer)]
68impl<Client, Context> ChainApiSubsystem<Client>
69where
70	Client: ChainApiBackend + AuxStore + 'static,
71{
72	fn start(self, ctx: Context) -> SpawnedSubsystem {
73		let future = run::<Client, Context>(ctx, self)
74			.map_err(|e| SubsystemError::with_origin("chain-api", e))
75			.boxed();
76		SpawnedSubsystem { future, name: "chain-api-subsystem" }
77	}
78}
79
80#[overseer::contextbounds(ChainApi, prefix = self::overseer)]
81async fn run<Client, Context>(
82	mut ctx: Context,
83	subsystem: ChainApiSubsystem<Client>,
84) -> SubsystemResult<()>
85where
86	Client: ChainApiBackend + AuxStore,
87{
88	loop {
89		match ctx.recv().await? {
90			FromOrchestra::Signal(OverseerSignal::Conclude) => return Ok(()),
91			FromOrchestra::Signal(OverseerSignal::ActiveLeaves(_)) => {},
92			FromOrchestra::Signal(OverseerSignal::BlockFinalized(..)) => {},
93			FromOrchestra::Communication { msg } => match msg {
94				ChainApiMessage::BlockNumber(hash, response_channel) => {
95					let _timer = subsystem.metrics.time_block_number();
96					let result =
97						subsystem.client.number(hash).await.map_err(|e| e.to_string().into());
98					subsystem.metrics.on_request(result.is_ok());
99					let _ = response_channel.send(result);
100				},
101				ChainApiMessage::BlockHeader(hash, response_channel) => {
102					let _timer = subsystem.metrics.time_block_header();
103					let result =
104						subsystem.client.header(hash).await.map_err(|e| e.to_string().into());
105					subsystem.metrics.on_request(result.is_ok());
106					let _ = response_channel.send(result);
107				},
108				ChainApiMessage::BlockWeight(hash, response_channel) => {
109					let _timer = subsystem.metrics.time_block_weight();
110					let result = sc_consensus_babe::block_weight(&*subsystem.client, hash)
111						.map_err(|e| e.to_string().into());
112					subsystem.metrics.on_request(result.is_ok());
113					let _ = response_channel.send(result);
114				},
115				ChainApiMessage::FinalizedBlockHash(number, response_channel) => {
116					let _timer = subsystem.metrics.time_finalized_block_hash();
117					// Note: we don't verify it's finalized
118					let result =
119						subsystem.client.hash(number).await.map_err(|e| e.to_string().into());
120					subsystem.metrics.on_request(result.is_ok());
121					let _ = response_channel.send(result);
122				},
123				ChainApiMessage::FinalizedBlockNumber(response_channel) => {
124					let _timer = subsystem.metrics.time_finalized_block_number();
125					let result = subsystem
126						.client
127						.info()
128						.await
129						.map_err(|e| e.to_string().into())
130						.map(|info| info.finalized_number);
131					subsystem.metrics.on_request(result.is_ok());
132					let _ = response_channel.send(result);
133				},
134				ChainApiMessage::Ancestors { hash, k, response_channel } => {
135					let _timer = subsystem.metrics.time_ancestors();
136					gum::trace!(target: LOG_TARGET, hash=%hash, k=k, "ChainApiMessage::Ancestors");
137
138					let next_parent_stream = futures::stream::unfold(
139						(hash, subsystem.client.clone()),
140						|(hash, client)| async move {
141							let maybe_header = client.header(hash).await;
142							match maybe_header {
143								// propagate the error
144								Err(e) => {
145									let e = e.to_string().into();
146									Some((Err(e), (hash, client)))
147								},
148								// fewer than `k` ancestors are available
149								Ok(None) => None,
150								Ok(Some(header)) => {
151									// stop at the genesis header.
152									if header.number == 0 {
153										None
154									} else {
155										Some((Ok(header.parent_hash), (header.parent_hash, client)))
156									}
157								},
158							}
159						},
160					);
161
162					let result = next_parent_stream.take(k).try_collect().await;
163					subsystem.metrics.on_request(result.is_ok());
164					let _ = response_channel.send(result);
165				},
166			},
167		}
168	}
169}
polkadot_node_core_chain_api/lib.rs

polkadot_node_core_chain_api/
lib.rs
