Move propose_with into a dedicated blocking threadpool (#614)

Cargo.lock

@@ -3818,6 +3818,7 @@ dependencies = [
  "substrate-transaction-pool 2.0.0 (git+https://github.com/paritytech/substrate?branch=polkadot-master)",
  "substrate-trie 2.0.0 (git+https://github.com/paritytech/substrate?branch=polkadot-master)",
  "tokio 0.1.22 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio-executor 0.2.0-alpha.6 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -6031,6 +6032,8 @@ version = "0.2.0-alpha.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "futures-util-preview 0.3.0-alpha.19 (registry+https://github.com/rust-lang/crates.io-index)",
+ "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio-sync 0.2.0-alpha.6 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]

validation/Cargo.toml

@@ -14,6 +14,7 @@ tokio = "0.1.22"
 derive_more = "0.14.1"
 log = "0.4.8"
 exit-future = "0.1.4"
+tokio-executor = { version = "0.2.0-alpha.6", features = ["blocking"] }
 codec = { package = "parity-scale-codec", version = "1.1.0", default-features = false, features = ["derive"] }
 availability_store = { package = "polkadot-availability-store", path = "../availability-store" }
 parachain = { package = "polkadot-parachain", path = "../parachain" }

validation/src/lib.rs

@@ -34,7 +34,8 @@ use std::{
 	pin::Pin,
 	sync::Arc,
 	time::{self, Duration, Instant},
-	task::{Poll, Context}
+	task::{Poll, Context},
+	mem,
 };
 
 use babe_primitives::BabeApi;
@@ -498,7 +499,7 @@ impl<C, N, P, SC, TxApi> ProposerFactory<C, N, P, SC, TxApi> where
 impl<C, N, P, SC, TxApi> consensus::Environment<Block> for ProposerFactory<C, N, P, SC, TxApi> where
 	C: Collators + Send + 'static,
 	N: Network,
-	TxApi: PoolChainApi<Block=Block>,
+	TxApi: PoolChainApi<Block=Block> + 'static,
 	P: ProvideRuntimeApi + HeaderBackend<Block> + BlockBody<Block> + Send + Sync + 'static,
 	P::Api: ParachainHost<Block> +
 		BlockBuilderApi<Block> +
@@ -557,8 +558,8 @@ pub struct Proposer<C: Send + Sync, TxApi: PoolChainApi> where
 }
 
 impl<C, TxApi> consensus::Proposer<Block> for Proposer<C, TxApi> where
-	TxApi: PoolChainApi<Block=Block>,
-	C: ProvideRuntimeApi + HeaderBackend<Block> + Send + Sync,
+	TxApi: PoolChainApi<Block=Block> + 'static,
+	C: ProvideRuntimeApi + HeaderBackend<Block> + Send + Sync + 'static,
 	C::Api: ParachainHost<Block> + BlockBuilderApi<Block> + ApiExt<Block, Error = client_error::Error>,
 {
 	type Error = Error;
@@ -616,18 +617,20 @@ impl<C, TxApi> consensus::Proposer<Block> for Proposer<C, TxApi> where
 		};
 
 		Either::Left(CreateProposal {
-			parent_hash: self.parent_hash.clone(),
-			parent_number: self.parent_number.clone(),
-			parent_id: self.parent_id.clone(),
-			client: self.client.clone(),
-			transaction_pool: self.transaction_pool.clone(),
-			table: self.tracker.table.clone(),
-			believed_minimum_timestamp: believed_timestamp,
-			timing,
-			inherent_data: Some(inherent_data),
-			inherent_digests,
-			// leave some time for the proposal finalisation
-			deadline,
+			state: CreateProposalState::Pending(CreateProposalData {
+				parent_hash: self.parent_hash.clone(),
+				parent_number: self.parent_number.clone(),
+				parent_id: self.parent_id.clone(),
+				client: self.client.clone(),
+				transaction_pool: self.transaction_pool.clone(),
+				table: self.tracker.table.clone(),
+				believed_minimum_timestamp: believed_timestamp,
+				timing,
+				inherent_data: Some(inherent_data),
+				inherent_digests,
+				// leave some time for the proposal finalisation
+				deadline,
+			})
 		})
 	}
 }
@@ -686,6 +689,21 @@ impl ProposalTiming {
 
 /// Future which resolves upon the creation of a proposal.
 pub struct CreateProposal<C: Send + Sync, TxApi: PoolChainApi> {
+	state: CreateProposalState<C, TxApi>,
+}
+
+/// Current status of the proposal future.
+enum CreateProposalState<C: Send + Sync, TxApi: PoolChainApi> {
+	/// Pending inclusion, with given proposal data.
+	Pending(CreateProposalData<C, TxApi>),
+	/// Represents the state when we switch from pending to fired.
+	Switching,
+	/// Block proposing has fired.
+	Fired(tokio_executor::blocking::Blocking<Result<Block, Error>>),
+}
+
+/// Inner data of the create proposal.
+struct CreateProposalData<C: Send + Sync, TxApi: PoolChainApi> {
 	parent_hash: Hash,
 	parent_number: BlockNumber,
 	parent_id: BlockId,
@@ -699,12 +717,12 @@ pub struct CreateProposal<C: Send + Sync, TxApi: PoolChainApi> {
 	deadline: Instant,
 }
 
-impl<C, TxApi> CreateProposal<C, TxApi> where
+impl<C, TxApi> CreateProposalData<C, TxApi> where
 	TxApi: PoolChainApi<Block=Block>,
 	C: ProvideRuntimeApi + HeaderBackend<Block> + Send + Sync,
 	C::Api: ParachainHost<Block> + BlockBuilderApi<Block> + ApiExt<Block, Error = client_error::Error>,
 {
-	fn propose_with(&mut self, candidates: Vec<AttestedCandidate>) -> Result<Block, Error> {
+	fn propose_with(mut self, candidates: Vec<AttestedCandidate>) -> Result<Block, Error> {
 		use block_builder::BlockBuilder;
 		use runtime_primitives::traits::{Hash as HashT, BlakeTwo256};
 
@@ -792,22 +810,51 @@ impl<C, TxApi> CreateProposal<C, TxApi> where
 }
 
 impl<C, TxApi> futures03::Future for CreateProposal<C, TxApi> where
-	TxApi: PoolChainApi<Block=Block>,
-	C: ProvideRuntimeApi + HeaderBackend<Block> + Send + Sync,
+	TxApi: PoolChainApi<Block=Block> + 'static,
+	C: ProvideRuntimeApi + HeaderBackend<Block> + Send + Sync + 'static,
 	C::Api: ParachainHost<Block> + BlockBuilderApi<Block> + ApiExt<Block, Error = client_error::Error>,
 {
 	type Output = Result<Block, Error>;
 
 	fn poll(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
+		let mut state = CreateProposalState::Switching;
+		mem::swap(&mut state, &mut self.state);
+
 		// 1. try to propose if we have enough includable candidates and other
 		// delays have concluded.
-		let included = self.table.includable_count();
-		futures03::ready!(self.timing.poll(cx, included));
+		let data = match state {
+			CreateProposalState::Pending(mut data) => {
+				let included = data.table.includable_count();
+				match data.timing.poll(cx, included) {
+					Poll::Pending => {
+						self.state = CreateProposalState::Pending(data);
+						return Poll::Pending
+					},
+					Poll::Ready(()) => (),
+				}
+
+				data
+			},
+			CreateProposalState::Switching => return Poll::Pending,
+			CreateProposalState::Fired(mut future) => {
+				let ret = Pin::new(&mut future).poll(cx);
+				self.state = CreateProposalState::Fired(future);
+				return ret
+			},
+		};
 
 		// 2. propose
-		let proposed_candidates = self.table.proposed_set();
+		let future = tokio_executor::blocking::run(move || {
+			let proposed_candidates = data.table.proposed_set();
+			data.propose_with(proposed_candidates)
+		});
+		self.state = CreateProposalState::Fired(future);
 
-		Poll::Ready(self.propose_with(proposed_candidates))
+		match &mut self.state {
+			CreateProposalState::Fired(future) => Pin::new(future).poll(cx),
+			CreateProposalState::Switching | CreateProposalState::Pending(_) =>
+				Poll::Pending,
+		}
 	}
 }