From 8aef81c58e1c82a0d18b3631727acd8b90befa4e Mon Sep 17 00:00:00 2001
From: Svyatoslav Nikolsky <svyatonik@gmail.com>
Date: Tue, 20 Sep 2022 17:26:24 +0300
Subject: [PATCH] Do not wait for tx status forever (#1578)

* do not wait for tx status forever

* more logging
---
 .../src/transaction_tracker.rs                | 81 +++++++++++++++----
 1 file changed, 64 insertions(+), 17 deletions(-)

diff --git a/bridges/relays/client-substrate/src/transaction_tracker.rs b/bridges/relays/client-substrate/src/transaction_tracker.rs
index b85e859017f7e..a84a46240a4ab 100644
--- a/bridges/relays/client-substrate/src/transaction_tracker.rs
+++ b/bridges/relays/client-substrate/src/transaction_tracker.rs
@@ -19,7 +19,7 @@
 use crate::{Chain, HashOf, Subscription, TransactionStatusOf};
 
 use async_trait::async_trait;
-use futures::{Stream, StreamExt};
+use futures::{future::Either, Future, FutureExt, Stream, StreamExt};
 use relay_utils::TrackedTransactionStatus;
 use std::time::Duration;
 
@@ -61,28 +61,50 @@ impl<C: Chain> TransactionTracker<C> {
 
 	/// Wait for final transaction status and return it along with last known internal invalidation
 	/// status.
-	async fn do_wait(self) -> (TrackedTransactionStatus, InvalidationStatus) {
-		let invalidation_status = watch_transaction_status::<C, _>(
+	async fn do_wait(
+		self,
+		wait_for_stall_timeout: impl Future<Output = ()>,
+		wait_for_stall_timeout_rest: impl Future<Output = ()>,
+	) -> (TrackedTransactionStatus, Option<InvalidationStatus>) {
+		// sometimes we want to wait for the rest of the stall timeout even if
+		// `wait_for_invalidation` has been "select"ed first => it is shared
+		let wait_for_invalidation = watch_transaction_status::<C, _>(
 			self.transaction_hash,
 			self.subscription.into_stream(),
-		)
-		.await;
-		match invalidation_status {
-			InvalidationStatus::Finalized =>
-				(TrackedTransactionStatus::Finalized, invalidation_status),
-			InvalidationStatus::Invalid => (TrackedTransactionStatus::Lost, invalidation_status),
-			InvalidationStatus::Lost => {
-				async_std::task::sleep(self.stall_timeout).await;
-				// if someone is still watching for our transaction, then we're reporting
-				// an error here (which is treated as "transaction lost")
+		);
+		futures::pin_mut!(wait_for_stall_timeout, wait_for_invalidation);
+
+		match futures::future::select(wait_for_stall_timeout, wait_for_invalidation).await {
+			Either::Left((_, _)) => {
 				log::trace!(
 					target: "bridge",
-					"{} transaction {:?} is considered lost after timeout",
+					"{} transaction {:?} is considered lost after timeout (no status response from the node)",
 					C::NAME,
 					self.transaction_hash,
 				);
 
-				(TrackedTransactionStatus::Lost, invalidation_status)
+				(TrackedTransactionStatus::Lost, None)
+			},
+			Either::Right((invalidation_status, _)) => match invalidation_status {
+				InvalidationStatus::Finalized =>
+					(TrackedTransactionStatus::Finalized, Some(invalidation_status)),
+				InvalidationStatus::Invalid =>
+					(TrackedTransactionStatus::Lost, Some(invalidation_status)),
+				InvalidationStatus::Lost => {
+					// wait for the rest of stall timeout - this way we'll be sure that the
+					// transaction is actually dead if it has been crafted properly
+					wait_for_stall_timeout_rest.await;
+					// if someone is still watching for our transaction, then we're reporting
+					// an error here (which is treated as "transaction lost")
+					log::trace!(
+						target: "bridge",
+						"{} transaction {:?} is considered lost after timeout",
+						C::NAME,
+						self.transaction_hash,
+					);
+
+					(TrackedTransactionStatus::Lost, Some(invalidation_status))
+				},
 			},
 		}
 	}
@@ -91,7 +113,9 @@ impl<C: Chain> TransactionTracker<C> {
 #[async_trait]
 impl<C: Chain> relay_utils::TransactionTracker for TransactionTracker<C> {
 	async fn wait(self) -> TrackedTransactionStatus {
-		self.do_wait().await.0
+		let wait_for_stall_timeout = async_std::task::sleep(self.stall_timeout).shared();
+		let wait_for_stall_timeout_rest = wait_for_stall_timeout.clone();
+		self.do_wait(wait_for_stall_timeout, wait_for_stall_timeout_rest).await.0
 	}
 }
 
@@ -233,8 +257,13 @@ mod tests {
 			Subscription(async_std::sync::Mutex::new(receiver)),
 		);
 
+		let wait_for_stall_timeout = futures::future::pending();
+		let wait_for_stall_timeout_rest = futures::future::ready(());
 		sender.send(Some(status)).await.unwrap();
-		tx_tracker.do_wait().now_or_never()
+		tx_tracker
+			.do_wait(wait_for_stall_timeout, wait_for_stall_timeout_rest)
+			.now_or_never()
+			.map(|(ts, is)| (ts, is.unwrap()))
 	}
 
 	#[async_std::test]
@@ -319,4 +348,22 @@ mod tests {
 			Some(InvalidationStatus::Lost),
 		);
 	}
+
+	#[async_std::test]
+	async fn lost_on_timeout_when_waiting_for_invalidation_status() {
+		let (_sender, receiver) = futures::channel::mpsc::channel(1);
+		let tx_tracker = TransactionTracker::<TestChain>::new(
+			Duration::from_secs(0),
+			Default::default(),
+			Subscription(async_std::sync::Mutex::new(receiver)),
+		);
+
+		let wait_for_stall_timeout = futures::future::ready(()).shared();
+		let wait_for_stall_timeout_rest = wait_for_stall_timeout.clone();
+		let wait_result = tx_tracker
+			.do_wait(wait_for_stall_timeout, wait_for_stall_timeout_rest)
+			.now_or_never();
+
+		assert_eq!(wait_result, Some((TrackedTransactionStatus::Lost, None)));
+	}
 }