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// Copyright 2017 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/>.
//! Attestation service.
/// Attestation service. A long running service that creates and manages parachain attestation
/// instances.
///
/// This uses a handle to an underlying thread pool to dispatch heavy work
/// such as candidate verification while performing event-driven work
/// on a local event loop.
use std::thread;
use std::time::{Duration, Instant};
use std::sync::Arc;
use client::{error::Result as ClientResult, BlockchainEvents, ChainHead, BlockBody};
use client::block_builder::api::BlockBuilder;
use client::blockchain::HeaderBackend;
use client::runtime_api::Core;
use primitives::ed25519;
use futures::prelude::*;
use polkadot_primitives::{Block, BlockId};
use polkadot_primitives::parachain::{CandidateReceipt, ParachainHost};
use extrinsic_store::Store as ExtrinsicStore;
use runtime_primitives::traits::{ProvideRuntimeApi, Header as HeaderT};
use tokio::runtime::TaskExecutor;
use tokio::runtime::current_thread::Runtime as LocalRuntime;
use tokio::timer::Interval;
use super::{Network, Collators, TableRouter};
/// Gets a list of the candidates in a block.
pub(crate) fn fetch_candidates<P: BlockBody<Block>>(client: &P, block: &BlockId)
-> ClientResult<Option<impl Iterator<Item=CandidateReceipt>>>
{
use codec::{Encode, Decode};
use polkadot_runtime::{Call, ParachainsCall, UncheckedExtrinsic as RuntimeExtrinsic};
let extrinsics = client.block_body(block)?;
Ok(extrinsics
.into_iter()
.filter_map(|ex| RuntimeExtrinsic::decode(&mut ex.encode().as_slice()))
.filter_map(|ex| match ex.function {
Call::Parachains(ParachainsCall::set_heads(heads)) =>
Some(heads.into_iter().map(|c| c.candidate)),
_ => None,
})
.next())
}
// creates a task to prune redundant entries in availability store upon block finalization
//
// NOTE: this will need to be changed to finality notification rather than
// block import notifications when the consensus switches to non-instant finality.
fn prune_unneeded_availability<P>(client: Arc<P>, extrinsic_store: ExtrinsicStore)
-> impl Future<Item=(),Error=()> + Send
where P: Send + Sync + BlockchainEvents<Block> + BlockBody<Block> + 'static
{
client.finality_notification_stream()
.for_each(move |notification| {
let hash = notification.hash;
let parent_hash = notification.header.parent_hash;
let candidate_hashes = match fetch_candidates(&*client, &BlockId::hash(hash)) {
Ok(Some(candidates)) => candidates.map(|c| c.hash()).collect(),
Ok(None) => {
warn!("Could not extract candidates from block body of imported block {:?}", hash);
return Ok(())
}
Err(e) => {
warn!("Failed to fetch block body for imported block {:?}: {:?}", hash, e);
return Ok(())
}
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};
if let Err(e) = extrinsic_store.candidates_finalized(parent_hash, candidate_hashes) {
warn!(target: "consensus", "Failed to prune unneeded available data: {:?}", e);
}
Ok(())
})
}
/// Parachain candidate attestation service handle.
pub(crate) struct ServiceHandle {
thread: Option<thread::JoinHandle<()>>,
exit_signal: Option<::exit_future::Signal>,
}
/// Create and start a new instance of the attestation service.
pub(crate) fn start<C, N, P>(
client: Arc<P>,
parachain_consensus: Arc<::ParachainConsensus<C, N, P>>,
thread_pool: TaskExecutor,
key: Arc<ed25519::Pair>,
extrinsic_store: ExtrinsicStore,
) -> ServiceHandle
where
C: Collators + Send + Sync + 'static,
<C::Collation as IntoFuture>::Future: Send + 'static,
P: BlockchainEvents<Block> + ChainHead<Block> + BlockBody<Block>,
P: ProvideRuntimeApi + HeaderBackend<Block> + Send + Sync + 'static,
P::Api: ParachainHost<Block> + Core<Block> + BlockBuilder<Block>,
N: Network + Send + Sync + 'static,
N::TableRouter: Send + 'static,
<<N::TableRouter as TableRouter>::FetchIncoming as IntoFuture>::Future: Send + 'static,
{
const TIMER_DELAY: Duration = Duration::from_secs(5);
const TIMER_INTERVAL: Duration = Duration::from_secs(30);
let (signal, exit) = ::exit_future::signal();
let thread = thread::spawn(move || {
let mut runtime = LocalRuntime::new().expect("Could not create local runtime");
let notifications = {
let client = client.clone();
let consensus = parachain_consensus.clone();
let key = key.clone();
client.import_notification_stream()
.for_each(move |notification| {
let parent_hash = notification.hash;
if notification.is_new_best {
let res = client
.runtime_api()
.authorities(&BlockId::hash(parent_hash))
.map_err(Into::into)
.and_then(|authorities| {
consensus.get_or_instantiate(
parent_hash,
notification.header.parent_hash().clone(),
&authorities,
key.clone(),
)
});
if let Err(e) = res {
warn!("Unable to start parachain consensus on top of {:?}: {}",
parent_hash, e);
}
Ok(())
})
.select(exit.clone())
.then(|_| Ok(()))
};
let prune_old_sessions = {
let client = client.clone();
let interval = Interval::new(
Instant::now() + TIMER_DELAY,
TIMER_INTERVAL,
);
interval
.for_each(move |_| match client.leaves() {
Ok(leaves) => {
parachain_consensus.retain(|h| leaves.contains(h));
Ok(())
}
Err(e) => {
warn!("Error fetching leaves from client: {:?}", e);
Ok(())
}
})
.map_err(|e| warn!("Timer error {:?}", e))
.select(exit.clone())
.then(|_| Ok(()))
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};
runtime.spawn(notifications);
thread_pool.spawn(prune_old_sessions);
let prune_available = prune_unneeded_availability(client, extrinsic_store)
.select(exit.clone())
.then(|_| Ok(()));
// spawn this on the tokio executor since it's fine on a thread pool.
thread_pool.spawn(prune_available);
if let Err(e) = runtime.block_on(exit) {
debug!("BFT event loop error {:?}", e);
}
});
ServiceHandle {
thread: Some(thread),
exit_signal: Some(signal),
}
}
impl Drop for ServiceHandle {
fn drop(&mut self) {
if let Some(signal) = self.exit_signal.take() {
signal.fire();
}
if let Some(thread) = self.thread.take() {
thread.join().expect("The service thread has panicked");
}
}
}