chore(sc-cli): improve runner and signals (#13688)

* chore(sc-cli): improve runner and signals

* Update client/cli/src/runner.rs

* fmt

---------

Co-authored-by: Bastian Köcher <git@kchr.de>

substrate/client/cli/src/signals.rs

@@ -0,0 +1,92 @@
+// This file is part of Substrate.
+
+// Copyright (C) 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 futures::{
+	future::{self, BoxFuture, FutureExt},
+	pin_mut, select, Future,
+};
+
+use sc_service::Error as ServiceError;
+
+/// Abstraction over OS signals to handle the shutdown of the node smoothly.
+///
+/// On `unix` this represents `SigInt` and `SigTerm`.
+pub struct Signals(BoxFuture<'static, ()>);
+
+impl Signals {
+	/// Return the signals future.
+	pub fn future(self) -> BoxFuture<'static, ()> {
+		self.0
+	}
+
+	/// Capture the relevant signals to handle shutdown of the node smoothly.
+	///
+	/// Needs to be called in a Tokio context to have access to the tokio reactor.
+	#[cfg(target_family = "unix")]
+	pub fn capture() -> std::result::Result<Self, ServiceError> {
+		use tokio::signal::unix::{signal, SignalKind};
+
+		let mut stream_int = signal(SignalKind::interrupt()).map_err(ServiceError::Io)?;
+		let mut stream_term = signal(SignalKind::terminate()).map_err(ServiceError::Io)?;
+
+		Ok(Signals(
+			async move {
+				future::select(stream_int.recv().boxed(), stream_term.recv().boxed()).await;
+			}
+			.boxed(),
+		))
+	}
+
+	/// Capture the relevant signals to handle shutdown of the node smoothly.
+	///
+	/// Needs to be called in a Tokio context to have access to the tokio reactor.
+	#[cfg(not(unix))]
+	pub fn capture() -> Result<Self, ServiceError> {
+		use tokio::signal::ctrl_c;
+
+		Ok(Signals(
+			async move {
+				let _ = ctrl_c().await;
+			}
+			.boxed(),
+		))
+	}
+
+	/// A dummy signal that never returns.
+	pub fn dummy() -> Self {
+		Self(future::pending().boxed())
+	}
+
+	/// Run a future task until receive a signal.
+	pub async fn run_until_signal<F, E>(self, func: F) -> Result<(), E>
+	where
+		F: Future<Output = Result<(), E>> + future::FusedFuture,
+		E: std::error::Error + Send + Sync + 'static,
+	{
+		let signals = self.future().fuse();
+
+		pin_mut!(func, signals);
+
+		select! {
+			_ = signals => {},
+			res = func => res?,
+		}
+
+		Ok(())
+	}
+}