Runtime worker threads (#7089)

* std variant

* principal work

* format and naming

* format and naming continued

* working nested fork

* add comment

* naming and tabs

* line width

* fix wording

* address review

* refactor dynamic dispatch

* update wasmtime

* some care

* move ext

* more refactor

* doc effort

* simplify

* doc effort

* tests and docs

* address review

* naming

* explain some args

* add example

* unwinding for native and tests

* rename stray

* fix refs

* fix tests

* fix warnings

* stray naming

* fixes and comments

* Update primitives/io/src/tasks.rs

Co-authored-by: cheme <emericchevalier.pro@gmail.com>

* make examples "compile"

* dyn_dispatch -> spawn_call

* fix impl

* address review

* Update primitives/io/src/lib.rs

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Update primitives/io/src/tasks.rs

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Update primitives/io/src/async_externalities.rs

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Update primitives/io/src/tasks.rs

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Update frame/example-parallel/src/lib.rs

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* fix compilation

* Update client/executor/common/src/wasm_runtime.rs

Co-authored-by: Sergei Shulepov <sergei@parity.io>

* address review

* Update client/executor/wasmtime/src/instance_wrapper.rs

Co-authored-by: Sergei Shulepov <sergei@parity.io>

* Update client/executor/src/native_executor.rs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Update primitives/io/src/tasks.rs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Update client/executor/src/native_executor.rs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Update primitives/io/src/tasks.rs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Update client/executor/wasmtime/src/instance_wrapper.rs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* address some issues

* address more issues

* wasm_only interface

* define sp_tasks

* avoid anyhow

* fix example

Co-authored-by: cheme <emericchevalier.pro@gmail.com>
Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>
Co-authored-by: Sergei Shulepov <sergei@parity.io>
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

substrate/frame/example-parallel/src/lib.rs

@@ -0,0 +1,152 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2020 Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Parallel tasks example
+//!
+//! This example pallet parallelizes validation of the enlisted participants
+//! (see `enlist_participants` dispatch).
+
+#![cfg_attr(not(feature = "std"), no_std)]
+
+use frame_system::ensure_signed;
+use frame_support::{
+	dispatch::DispatchResult, decl_module, decl_storage, decl_event,
+};
+use sp_runtime::RuntimeDebug;
+
+use codec::{Encode, Decode};
+use sp_std::vec::Vec;
+
+#[cfg(test)]
+mod tests;
+
+pub trait Trait: frame_system::Trait {
+	/// The overarching event type.
+	type Event: From<Event> + Into<<Self as frame_system::Trait>::Event>;
+	/// The overarching dispatch call type.
+	type Call: From<Call<Self>>;
+}
+
+decl_storage! {
+	trait Store for Module<T: Trait> as ExampleOffchainWorker {
+		/// A vector of current participants
+		///
+		/// To enlist someone to participate, signed payload should be
+		/// sent to `enlist`.
+		Participants get(fn participants): Vec<Vec<u8>>;
+
+		/// Current event id to enlist participants to.
+		CurrentEventId get(fn get_current_event_id): Vec<u8>;
+	}
+}
+
+decl_event!(
+	/// Events generated by the module.
+	pub enum Event {
+		/// When new event is drafted.
+		NewEventDrafted(Vec<u8>),
+	}
+);
+
+/// Request to enlist participant.
+#[derive(Encode, Decode, Clone, PartialEq, Eq, RuntimeDebug)]
+pub struct EnlistedParticipant {
+	pub account: Vec<u8>,
+	pub signature: Vec<u8>,
+}
+
+impl EnlistedParticipant {
+	fn verify(&self, event_id: &[u8]) -> bool {
+		use sp_core::Public;
+		use std::convert::TryFrom;
+		use sp_runtime::traits::Verify;
+
+		match sp_core::sr25519::Signature::try_from(&self.signature[..]) {
+			Ok(signature) => {
+				let public = sp_core::sr25519::Public::from_slice(self.account.as_ref());
+				signature.verify(event_id, &public)
+			}
+			_ => false
+		}
+	}
+}
+
+decl_module! {
+	/// A public part of the pallet.
+	pub struct Module<T: Trait> for enum Call where origin: T::Origin {
+		fn deposit_event() = default;
+
+		/// Get the new event running.
+		#[weight = 0]
+		pub fn run_event(origin, id: Vec<u8>) -> DispatchResult {
+			let _ = ensure_signed(origin)?;
+			Participants::kill();
+			CurrentEventId::mutate(move |event_id| *event_id = id);
+			Ok(())
+		}
+
+		/// Submit list of participants to the current event.
+		///
+		/// The example utilizes parallel execution by checking half of the
+		/// signatures in spawned task.
+		#[weight = 0]
+		pub fn enlist_participants(origin, participants: Vec<EnlistedParticipant>)
+			-> DispatchResult
+		{
+			let _ = ensure_signed(origin)?;
+
+			if validate_participants_parallel(&CurrentEventId::get(), &participants[..]) {
+				for participant in participants {
+					Participants::append(participant.account);
+				}
+			}
+			Ok(())
+		}
+	}
+}
+
+fn validate_participants_parallel(event_id: &[u8], participants: &[EnlistedParticipant]) -> bool {
+
+	fn spawn_verify(data: Vec<u8>) -> Vec<u8> {
+		let stream = &mut &data[..];
+		let event_id = Vec::<u8>::decode(stream).expect("Failed to decode");
+		let participants = Vec::<EnlistedParticipant>::decode(stream).expect("Failed to decode");
+
+		for participant in participants {
+			if !participant.verify(&event_id) {
+				return false.encode()
+			}
+		}
+		true.encode()
+	}
+
+	let mut async_payload = Vec::new();
+	event_id.encode_to(&mut async_payload);
+	participants[..participants.len() / 2].encode_to(&mut async_payload);
+
+	let handle = sp_tasks::spawn(spawn_verify, async_payload);
+	let mut result = true;
+
+	for participant in &participants[participants.len()/2+1..] {
+		if !participant.verify(event_id) {
+			result = false;
+			break;
+		}
+	}
+
+	bool::decode(&mut &handle.join()[..]).expect("Failed to decode result") && result
+}