Reset cancelled wallet sync state

Restore wallet sync status and notify waiting callers when the task
performing a sync is cancelled, allowing later sync attempts to run.

Co-Authored-By: HAL 9000

Author: tnull

src/chain/bitcoind.rs

@@ -31,7 +31,7 @@ use lightning_block_sync::{
 };
 use serde::Serialize;
 
-use super::WalletSyncStatus;
+use super::{WalletSyncGuard, WalletSyncStatus};
 use crate::config::{
 	BitcoindRestClientConfig, Config, DEFAULT_FEE_RATE_CACHE_UPDATE_TIMEOUT_SECS,
 	DEFAULT_TX_BROADCAST_TIMEOUT_SECS,
@@ -152,12 +152,14 @@ impl BitcoindChainSource {
 	) {
 		// First register for the wallet polling status to make sure `Node::sync_wallets` calls
 		// wait on the result before proceeding.
-		{
+		let initial_sync_guard = {
 			let mut status_lock = self.wallet_polling_status.lock().expect("lock");
 			if status_lock.register_or_subscribe_pending_sync().is_some() {
 				debug_assert!(false, "Sync already in progress. This should never happen.");
+				return;
 			}
-		}
+			WalletSyncGuard::new(&self.wallet_polling_status, Error::WalletOperationFailed)
+		};
 
 		log_info!(
 			self.logger,
@@ -285,7 +287,7 @@ impl BitcoindChainSource {
 		}
 
 		// Now propagate the initial result to unblock waiting subscribers.
-		self.wallet_polling_status.lock().expect("lock").propagate_result_to_subscribers(Ok(()));
+		initial_sync_guard.complete(Ok(()));
 
 		let mut chain_polling_interval =
 			tokio::time::interval(Duration::from_secs(CHAIN_POLLING_INTERVAL_SECS));
@@ -396,6 +398,8 @@ impl BitcoindChainSource {
 				Error::WalletOperationFailed
 			})?;
 		}
+		let sync_guard =
+			WalletSyncGuard::new(&self.wallet_polling_status, Error::WalletOperationFailed);
 
 		let res = self
 			.poll_and_update_listeners_inner(
@@ -406,7 +410,7 @@ impl BitcoindChainSource {
 			)
 			.await;
 
-		self.wallet_polling_status.lock().expect("lock").propagate_result_to_subscribers(res);
+		sync_guard.complete(res);
 
 		res
 	}

src/chain/electrum.rs

@@ -25,7 +25,7 @@ use lightning::chain::{Confirm, Filter, WatchedOutput};
 use lightning::util::ser::Writeable;
 use lightning_transaction_sync::ElectrumSyncClient;
 
-use super::WalletSyncStatus;
+use super::{WalletSyncGuard, WalletSyncStatus};
 use crate::config::{
 	clamp_full_scan_stop_gap, Config, ElectrumSyncConfig, MAX_FULL_SCAN_STOP_GAP,
 	MIN_FULL_SCAN_STOP_GAP,
@@ -113,10 +113,12 @@ impl ElectrumChainSource {
 				Error::WalletOperationFailed
 			})?;
 		}
+		let sync_guard =
+			WalletSyncGuard::new(&self.onchain_wallet_sync_status, Error::WalletOperationFailed);
 
 		let res = self.sync_onchain_wallet_inner(onchain_wallet).await;
 
-		self.onchain_wallet_sync_status.lock().expect("lock").propagate_result_to_subscribers(res);
+		sync_guard.complete(res);
 
 		res
 	}
@@ -223,14 +225,13 @@ impl ElectrumChainSource {
 				Error::TxSyncFailed
 			})?;
 		}
+		let sync_guard =
+			WalletSyncGuard::new(&self.lightning_wallet_sync_status, Error::TxSyncFailed);
 
 		let res =
 			self.sync_lightning_wallet_inner(channel_manager, chain_monitor, output_sweeper).await;
 
-		self.lightning_wallet_sync_status
-			.lock()
-			.expect("lock")
-			.propagate_result_to_subscribers(res);
+		sync_guard.complete(res);
 
 		res
 	}

src/chain/esplora.rs

@@ -18,7 +18,7 @@ use lightning::chain::{Confirm, Filter, WatchedOutput};
 use lightning::util::ser::Writeable;
 use lightning_transaction_sync::EsploraSyncClient;
 
-use super::WalletSyncStatus;
+use super::{WalletSyncGuard, WalletSyncStatus};
 use crate::config::{
 	clamp_full_scan_stop_gap, Config, EsploraSyncConfig, BDK_CLIENT_CONCURRENCY,
 	MAX_FULL_SCAN_STOP_GAP, MIN_FULL_SCAN_STOP_GAP,
@@ -125,10 +125,12 @@ impl EsploraChainSource {
 				Error::WalletOperationFailed
 			})?;
 		}
+		let sync_guard =
+			WalletSyncGuard::new(&self.onchain_wallet_sync_status, Error::WalletOperationFailed);
 
 		let res = self.sync_onchain_wallet_inner(onchain_wallet).await;
 
-		self.onchain_wallet_sync_status.lock().expect("lock").propagate_result_to_subscribers(res);
+		sync_guard.complete(res);
 
 		res
 	}
@@ -275,14 +277,13 @@ impl EsploraChainSource {
 				Error::WalletOperationFailed
 			})?;
 		}
+		let sync_guard =
+			WalletSyncGuard::new(&self.lightning_wallet_sync_status, Error::WalletOperationFailed);
 
 		let res =
 			self.sync_lightning_wallet_inner(channel_manager, chain_monitor, output_sweeper).await;
 
-		self.lightning_wallet_sync_status
-			.lock()
-			.expect("lock")
-			.propagate_result_to_subscribers(res);
+		sync_guard.complete(res);
 
 		res
 	}

src/chain/mod.rs

@@ -65,6 +65,34 @@ pub(crate) enum WalletSyncStatus {
 	InProgress { subscribers: tokio::sync::broadcast::Sender<Result<(), Error>> },
 }
 
+pub(crate) struct WalletSyncGuard<'a> {
+	status: &'a Mutex<WalletSyncStatus>,
+	cancellation_error: Error,
+	active: bool,
+}
+
+impl<'a> WalletSyncGuard<'a> {
+	pub(crate) fn new(status: &'a Mutex<WalletSyncStatus>, cancellation_error: Error) -> Self {
+		Self { status, cancellation_error, active: true }
+	}
+
+	pub(crate) fn complete(mut self, res: Result<(), Error>) {
+		self.status.lock().expect("lock").propagate_result_to_subscribers(res);
+		self.active = false;
+	}
+}
+
+impl Drop for WalletSyncGuard<'_> {
+	fn drop(&mut self) {
+		if self.active {
+			self.status
+				.lock()
+				.expect("lock")
+				.propagate_result_to_subscribers(Err(self.cancellation_error));
+		}
+	}
+}
+
 impl WalletSyncStatus {
 	fn register_or_subscribe_pending_sync(
 		&mut self,
@@ -95,16 +123,7 @@ impl WalletSyncStatus {
 				WalletSyncStatus::InProgress { subscribers } => {
 					// A sync is in-progress, we notify subscribers.
 					if subscribers.receiver_count() > 0 {
-						match subscribers.send(res) {
-							Ok(_) => (),
-							Err(e) => {
-								debug_assert!(
-									false,
-									"Failed to send wallet sync result to subscribers: {:?}",
-									e
-								);
-							},
-						}
+						let _ = subscribers.send(res);
 					}
 					*self = WalletSyncStatus::Completed;
 				},
@@ -561,3 +580,28 @@ impl Filter for ChainSource {
 		}
 	}
 }
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+
+	#[test]
+	fn wallet_sync_guard_resets_abandoned_sync() {
+		let status = Mutex::new(WalletSyncStatus::Completed);
+		assert!(status.lock().expect("lock").register_or_subscribe_pending_sync().is_none());
+		let sync_guard = WalletSyncGuard::new(&status, Error::WalletOperationFailed);
+		let mut subscriber = status
+			.lock()
+			.expect("lock")
+			.register_or_subscribe_pending_sync()
+			.expect("sync subscriber");
+
+		drop(sync_guard);
+
+		assert!(
+			matches!(*status.lock().expect("lock"), WalletSyncStatus::Completed),
+			"abandoned wallet sync should reset its status"
+		);
+		assert_eq!(subscriber.try_recv(), Ok(Err(Error::WalletOperationFailed)));
+	}
+}