Revert "Use Subscription Manager from jsonrpc-pubsub (#6208)" (#6252)

This reverts commit ea1eb4e57f.

substrate/client/rpc-api/src/lib.rs

@@ -23,8 +23,10 @@
 mod errors;
 mod helpers;
 mod policy;
+mod subscriptions;
 
 pub use jsonrpc_core::IoHandlerExtension as RpcExtension;
+pub use subscriptions::{Subscriptions, TaskExecutor};
 pub use helpers::Receiver;
 pub use policy::DenyUnsafe;
 

substrate/client/rpc-api/src/subscriptions.rs

@@ -0,0 +1,121 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2017-2020 Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0
+
+// This program 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.
+
+// This program 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 this program. If not, see <https://www.gnu.org/licenses/>.
+
+use std::collections::HashMap;
+use std::sync::{Arc, atomic::{self, AtomicUsize}};
+
+use log::{error, warn};
+use jsonrpc_pubsub::{SubscriptionId, typed::{Sink, Subscriber}};
+use parking_lot::Mutex;
+use jsonrpc_core::futures::sync::oneshot;
+use jsonrpc_core::futures::{Future, future};
+
+type Id = u64;
+
+/// Alias for a an implementation of `futures::future::Executor`.
+pub type TaskExecutor = Arc<dyn future::Executor<Box<dyn Future<Item = (), Error = ()> + Send>> + Send + Sync>;
+
+/// Generate unique ids for subscriptions.
+#[derive(Clone, Debug)]
+pub struct IdProvider {
+	next_id: Arc<AtomicUsize>,
+}
+impl Default for IdProvider {
+	fn default() -> Self {
+		IdProvider {
+			next_id: Arc::new(AtomicUsize::new(1)),
+		}
+	}
+}
+
+impl IdProvider {
+	/// Returns next id for the subscription.
+	pub fn next_id(&self) -> Id {
+		self.next_id.fetch_add(1, atomic::Ordering::AcqRel) as u64
+	}
+}
+
+/// Subscriptions manager.
+///
+/// Takes care of assigning unique subscription ids and
+/// driving the sinks into completion.
+#[derive(Clone)]
+pub struct Subscriptions {
+	next_id: IdProvider,
+	active_subscriptions: Arc<Mutex<HashMap<Id, oneshot::Sender<()>>>>,
+	executor: TaskExecutor,
+}
+
+impl Subscriptions {
+	/// Creates new `Subscriptions` object.
+	pub fn new(executor: TaskExecutor) -> Self {
+		Subscriptions {
+			next_id: Default::default(),
+			active_subscriptions: Default::default(),
+			executor,
+		}
+	}
+
+	/// Borrows the internal task executor.
+	///
+	/// This can be used to spawn additional tasks on the underlying event loop.
+	pub fn executor(&self) -> &TaskExecutor {
+		&self.executor
+	}
+
+	/// Creates new subscription for given subscriber.
+	///
+	/// Second parameter is a function that converts Subscriber sink into a future.
+	/// This future will be driven to completion by the underlying event loop
+	/// or will be cancelled in case #cancel is invoked.
+	pub fn add<T, E, G, R, F>(&self, subscriber: Subscriber<T, E>, into_future: G) -> SubscriptionId where
+		G: FnOnce(Sink<T, E>) -> R,
+		R: future::IntoFuture<Future=F, Item=(), Error=()>,
+		F: future::Future<Item=(), Error=()> + Send + 'static,
+	{
+		let id = self.next_id.next_id();
+		let subscription_id: SubscriptionId = id.into();
+		if let Ok(sink) = subscriber.assign_id(subscription_id.clone()) {
+			let (tx, rx) = oneshot::channel();
+			let future = into_future(sink)
+				.into_future()
+				.select(rx.map_err(|e| warn!("Error timeing out: {:?}", e)))
+				.then(|_| Ok(()));
+
+			self.active_subscriptions.lock().insert(id, tx);
+			if self.executor.execute(Box::new(future)).is_err() {
+				error!("Failed to spawn RPC subscription task");
+			}
+		}
+
+		subscription_id
+	}
+
+	/// Cancel subscription.
+	///
+	/// Returns true if subscription existed or false otherwise.
+	pub fn cancel(&self, id: SubscriptionId) -> bool {
+		if let SubscriptionId::Number(id) = id {
+			if let Some(tx) = self.active_subscriptions.lock().remove(&id) {
+				let _ = tx.send(());
+				return true;
+			}
+		}
+		false
+	}
+}