Fix bitcoind shutdown hang

Previously, the shutdown process could hang when using the bitcoind
backend because the syncing process was not always checking if we had
received the shutdown signal. Now with any future we call during the
sync process we will use a `tokio::select!` to make sure we abort early
if we receive a stop signal.

Author: benthecarman

src/chain/bitcoind.rs

@@ -147,6 +147,12 @@ impl BitcoindChainSource {
 		const MAX_BACKOFF_SECS: u64 = 300;
 
 		loop {
+			// if the stop_sync_sender has been dropped, we should just exit
+			if stop_sync_receiver.has_changed().unwrap_or(true) {
+				log_trace!(self.logger, "Stopping initial chain sync.");
+				return;
+			}
+
 			let channel_manager_best_block_hash = channel_manager.current_best_block().block_hash;
 			let sweeper_best_block_hash = output_sweeper.current_best_block().block_hash;
 			let onchain_wallet_best_block_hash =
@@ -226,7 +232,18 @@ impl BitcoindChainSource {
 									e,
 									backoff
 								);
-						tokio::time::sleep(Duration::from_secs(backoff)).await;
+						// Sleep with stop signal check to allow immediate shutdown
+						tokio::select! {
+							biased;
+							_ = stop_sync_receiver.changed() => {
+								log_trace!(
+									self.logger,
+									"Stopping initial chain sync.",
+								);
+								return;
+							}
+							_ = tokio::time::sleep(Duration::from_secs(backoff)) => {}
+						}
 						backoff = std::cmp::min(backoff * 2, MAX_BACKOFF_SECS);
 					} else {
 						log_error!(
@@ -235,7 +252,18 @@ impl BitcoindChainSource {
 									e,
 									MAX_BACKOFF_SECS
 								);
-						tokio::time::sleep(Duration::from_secs(MAX_BACKOFF_SECS)).await;
+						// Sleep with stop signal check to allow immediate shutdown
+						tokio::select! {
+							biased;
+							_ = stop_sync_receiver.changed() => {
+								log_trace!(
+									self.logger,
+									"Stopping initial chain sync during backoff.",
+								);
+								return;
+							}
+							_ = tokio::time::sleep(Duration::from_secs(MAX_BACKOFF_SECS)) => {}
+						}
 					}
 				},
 			}
@@ -260,6 +288,7 @@ impl BitcoindChainSource {
 		let mut last_best_block_hash = None;
 		loop {
 			tokio::select! {
+				biased;
 				_ = stop_sync_receiver.changed() => {
 					log_trace!(
 						self.logger,
@@ -268,17 +297,38 @@ impl BitcoindChainSource {
 					return;
 				}
 				_ = chain_polling_interval.tick() => {
-					let _ = self.poll_and_update_listeners(
-						Arc::clone(&channel_manager),
-						Arc::clone(&chain_monitor),
-						Arc::clone(&output_sweeper)
-					).await;
+					tokio::select! {
+						biased;
+						_ = stop_sync_receiver.changed() => {
+							log_trace!(
+								self.logger,
+								"Stopping polling for new chain data.",
+							);
+							return;
+						}
+						_ = self.poll_and_update_listeners(
+							Arc::clone(&channel_manager),
+							Arc::clone(&chain_monitor),
+							Arc::clone(&output_sweeper)
+						) => {}
+					}
 				}
 				_ = fee_rate_update_interval.tick() => {
 					if last_best_block_hash != Some(channel_manager.current_best_block().block_hash) {
-						let update_res = self.update_fee_rate_estimates().await;
-						if update_res.is_ok() {
-							last_best_block_hash = Some(channel_manager.current_best_block().block_hash);
+						tokio::select! {
+							biased;
+							_ = stop_sync_receiver.changed() => {
+								log_trace!(
+									self.logger,
+									"Stopping polling for new chain data.",
+								);
+								return;
+							}
+							update_res = self.update_fee_rate_estimates() => {
+								if update_res.is_ok() {
+									last_best_block_hash = Some(channel_manager.current_best_block().block_hash);
+								}
+							}
 						}
 					}
 				}