explicit stop of AsyncImportThread (#360)

substrate/substrate/network/src/import_queue.rs

@@ -37,6 +37,8 @@ use sync::ChainSync;
 pub trait ImportQueue<B: BlockT>: Send + Sync {
 	/// Clear the queue when sync is restarting.
 	fn clear(&self);
+	/// Clears the import queue and stops importing.
+	fn stop(&self);
 	/// Get queue status.
 	fn status(&self) -> ImportQueueStatus<B>;
 	/// Is block with given hash is currently in the queue.
@@ -109,6 +111,16 @@ impl<B: BlockT> ImportQueue<B> for AsyncImportQueue<B> {
 		*best_importing_number = Zero::zero();
 	}
 
+	fn stop(&self) {
+		self.clear();
+		if let Some(handle) = self.handle.lock().take() {
+			self.data.is_stopping.store(true, Ordering::SeqCst);
+			self.data.signal.notify_one();
+
+			let _ = handle.join();
+		}
+	}
+
 	fn status(&self) -> ImportQueueStatus<B> {
 		ImportQueueStatus {
 			importing_count: self.data.queue_blocks.read().len(),
@@ -138,12 +150,7 @@ impl<B: BlockT> ImportQueue<B> for AsyncImportQueue<B> {
 
 impl<B: BlockT> Drop for AsyncImportQueue<B> {
 	fn drop(&mut self) {
-		if let Some(handle) = self.handle.lock().take() {
-			self.data.is_stopping.store(true, Ordering::SeqCst);
-			self.data.signal.notify_one();
-
-			let _ = handle.join();
-		}
+		self.stop();
 	}
 }
 
@@ -433,6 +440,8 @@ pub mod tests {
 	impl<B: 'static + BlockT> ImportQueue<B> for SyncImportQueue {
 		fn clear(&self) { }
 
+		fn stop(&self) { }
+
 		fn status(&self) -> ImportQueueStatus<B> {
 			ImportQueueStatus {
 				importing_count: 0,

substrate/substrate/network/src/protocol.rs

@@ -536,6 +536,15 @@ impl<B: BlockT, S: Specialization<B>> Protocol<B, S> {
 		handshaking_peers.clear();
 	}
 
+	pub fn stop(&self) {
+		// stop processing import requests first (without holding a sync lock)
+		let import_queue = self.sync.read().import_queue();
+		import_queue.stop();
+
+		// and then clear all the sync data
+		self.abort();
+	}
+
 	pub fn on_block_announce(&self, io: &mut SyncIo, peer_id: PeerId, announce: message::BlockAnnounce<B::Header>) {
 		let header = announce.header;
 		let hash = header.hash();

substrate/substrate/network/src/service.rs

@@ -213,7 +213,7 @@ impl<B: BlockT + 'static, S: Specialization<B>> Service<B, S> {
 	}
 
 	fn stop(&self) {
-		self.handler.protocol.abort();
+		self.handler.protocol.stop();
 		self.network.stop();
 	}
 }

substrate/substrate/network/src/sync.rs

@@ -100,7 +100,12 @@ impl<B: BlockT> ChainSync<B> {
 		self.peers.values().max_by_key(|p| p.best_number).map(|p| p.best_number)
 	}
 
-	/// Returns sync status
+	/// Returns import queue reference.
+	pub(crate) fn import_queue(&self) -> Arc<ImportQueue<B>> {
+		self.import_queue.clone()
+	}
+
+	/// Returns sync status.
 	pub(crate) fn status(&self) -> Status<B> {
 		let best_seen = self.best_seen_block();
 		let state = match &best_seen {