Fix a race conditon in the pool when transactions are imported during pruning. (#2136)

* Store recently pruned tags to avoid re-importing transactions.

* Update core/transaction-pool/graph/src/base_pool.rs

* Update core/transaction-pool/graph/src/base_pool.rs

* Update core/transaction-pool/graph/src/base_pool.rs

* Update base_pool.rs

substrate/core/transaction-pool/graph/src/base_pool.rs

@@ -19,6 +19,7 @@
 //! For a more full-featured pool, have a look at the `pool` module.
 
 use std::{
+	collections::HashSet,
 	fmt,
 	hash,
 	sync::Arc,
@@ -134,6 +135,9 @@ impl<Hash, Extrinsic> fmt::Debug for Transaction<Hash, Extrinsic> where
 	}
 }
 
+/// Store last pruned tags for given number of invocations.
+const RECENTLY_PRUNED_TAGS: usize = 2;
+
 /// Transaction pool.
 ///
 /// Builds a dependency graph for all transactions in the pool and returns
@@ -148,6 +152,12 @@ impl<Hash, Extrinsic> fmt::Debug for Transaction<Hash, Extrinsic> where
 pub struct BasePool<Hash: hash::Hash + Eq, Ex> {
 	future: FutureTransactions<Hash, Ex>,
 	ready: ReadyTransactions<Hash, Ex>,
+	/// Store recently pruned tags (for last two invocations).
+	///
+	/// This is used to make sure we don't accidentally put
+	/// transactions to future in case they were just stuck in verification.
+	recently_pruned: [HashSet<Tag>; RECENTLY_PRUNED_TAGS],
+	recently_pruned_index: usize,
 }
 
 impl<Hash: hash::Hash + Eq, Ex> Default for BasePool<Hash, Ex> {
@@ -155,6 +165,8 @@ impl<Hash: hash::Hash + Eq, Ex> Default for BasePool<Hash, Ex> {
 		BasePool {
 			future: Default::default(),
 			ready: Default::default(),
+			recently_pruned: Default::default(),
+			recently_pruned_index: 0,
 		}
 	}
 }
@@ -175,7 +187,11 @@ impl<Hash: hash::Hash + Member + Serialize, Ex: ::std::fmt::Debug> BasePool<Hash
 			bail!(error::ErrorKind::AlreadyImported(Box::new(tx.hash.clone())))
 		}
 
-		let tx = WaitingTransaction::new(tx, self.ready.provided_tags());
+		let tx = WaitingTransaction::new(
+			tx,
+			self.ready.provided_tags(),
+			&self.recently_pruned,
+		);
 		trace!(target: "txpool", "[{:?}] {:?}", tx.transaction.hash, tx);
 		debug!(target: "txpool", "[{:?}] Importing to {}", tx.transaction.hash, if tx.is_ready() { "ready" } else { "future" });
 
@@ -354,12 +370,17 @@ impl<Hash: hash::Hash + Member + Serialize, Ex: ::std::fmt::Debug> BasePool<Hash
 	pub fn prune_tags(&mut self, tags: impl IntoIterator<Item=Tag>) -> PruneStatus<Hash, Ex> {
 		let mut to_import = vec![];
 		let mut pruned = vec![];
+		let recently_pruned = &mut self.recently_pruned[self.recently_pruned_index];
+		self.recently_pruned_index = (self.recently_pruned_index + 1) % RECENTLY_PRUNED_TAGS;
+		recently_pruned.clear();
 
 		for tag in tags {
 			// make sure to promote any future transactions that could be unlocked
 			to_import.append(&mut self.future.satisfy_tags(::std::iter::once(&tag)));
 			// and actually prune transactions in ready queue
-			pruned.append(&mut self.ready.prune_tags(tag));
+			pruned.append(&mut self.ready.prune_tags(tag.clone()));
+			// store the tags for next submission
+			recently_pruned.insert(tag);
 		}
 
 		let mut promoted = vec![];
@@ -663,7 +684,6 @@ mod tests {
 		assert_eq!(pool.future.len(), 0);
 	}
 
-
 	#[test]
 	fn should_handle_a_cycle_with_low_priority() {
 		// given
@@ -798,7 +818,6 @@ mod tests {
 		assert_eq!(pool.future.len(), 0);
 	}
 
-
 	#[test]
 	fn should_prune_ready_transactions() {
 		// given
@@ -887,5 +906,4 @@ mod tests {
 			r#"Transaction { hash: 4, priority: 1000, valid_till: 64, bytes: 1, requires: [03,02], provides: [04], data: [4]}"#.to_owned()
 		);
 	}
-
 }

substrate/core/transaction-pool/graph/src/future.rs

@@ -71,10 +71,19 @@ impl<Hash, Ex> WaitingTransaction<Hash, Ex> {
 	///
 	/// Computes the set of missing tags based on the requirements and tags that
 	/// are provided by all transactions in the ready queue.
-	pub fn new(transaction: Transaction<Hash, Ex>, provided: &HashMap<Tag, Hash>) -> Self {
+	pub fn new(
+		transaction: Transaction<Hash, Ex>,
+		provided: &HashMap<Tag, Hash>,
+		recently_pruned: &[HashSet<Tag>],
+	) -> Self {
 		let missing_tags = transaction.requires
 			.iter()
-			.filter(|tag| !provided.contains_key(&**tag))
+			.filter(|tag| {
+				// is true if the tag is already satisfied either via transaction in the pool
+				// or one that was recently included.
+				let is_provided = provided.contains_key(&**tag) || recently_pruned.iter().any(|x| x.contains(&**tag));
+				!is_provided
+			})
 			.cloned()
 			.collect();
 

substrate/core/transaction-pool/graph/src/pool.rs

@@ -460,7 +460,9 @@ mod tests {
 	use crate::watcher;
 
 	#[derive(Debug, Default)]
-	struct TestApi;
+	struct TestApi {
+		delay: Mutex<Option<std::sync::mpsc::Receiver<()>>>,
+	}
 
 	impl ChainApi for TestApi {
 		type Block = Block;
@@ -469,9 +471,20 @@ mod tests {
 
 		/// Verify extrinsic at given block.
 		fn validate_transaction(&self, at: &BlockId<Self::Block>, uxt: ExtrinsicFor<Self>) -> Result<TransactionValidity, Self::Error> {
+
 			let block_number = self.block_id_to_number(at)?.unwrap();
 			let nonce = uxt.transfer().nonce;
 
+			// This is used to control the test flow.
+			if nonce > 0 {
+				let opt = self.delay.lock().take();
+				if let Some(delay) = opt {
+					if delay.recv().is_err() {
+						println!("Error waiting for delay!");
+					}
+				}
+			}
+
 			if nonce < block_number {
 				Ok(TransactionValidity::Invalid(0))
 			} else {
@@ -878,5 +891,59 @@ mod tests {
 			assert_eq!(stream.next(), Some(Ok(watcher::Status::Ready)));
 			assert_eq!(stream.next(), Some(Ok(watcher::Status::Dropped)));
 		}
+
+		#[test]
+		fn should_handle_pruning_in_the_middle_of_import() {
+			let _ = env_logger::try_init();
+			// given
+			let (ready, is_ready) = std::sync::mpsc::sync_channel(0);
+			let (tx, rx) = std::sync::mpsc::sync_channel(1);
+			let mut api = TestApi::default();
+			api.delay = Mutex::new(rx.into());
+			let pool = Arc::new(Pool::new(Default::default(), api));
+
+			// when
+			let xt = uxt(Transfer {
+				from: AccountId::from_h256(H256::from_low_u64_be(1)),
+				to: AccountId::from_h256(H256::from_low_u64_be(2)),
+				amount: 5,
+				nonce: 1,
+			});
+
+			// This transaction should go to future, since we use `nonce: 1`
+			let pool2 = pool.clone();
+			std::thread::spawn(move || {
+				pool2.submit_one(&BlockId::Number(0), xt).unwrap();
+				ready.send(()).unwrap();
+			});
+
+			// But now before the previous one is imported we import
+			// the one that it depends on.
+			let xt = uxt(Transfer {
+				from: AccountId::from_h256(H256::from_low_u64_be(1)),
+				to: AccountId::from_h256(H256::from_low_u64_be(2)),
+				amount: 4,
+				nonce: 0,
+			});
+			// The tag the above transaction provides (TestApi is using just nonce as u8)
+			let provides = vec![0_u8];
+			pool.submit_one(&BlockId::Number(0), xt).unwrap();
+			assert_eq!(pool.status().ready, 1);
+
+			// Now block import happens before the second transaction is able to finish verification.
+			pool.prune_tags(&BlockId::Number(1), vec![provides], vec![]).unwrap();
+			assert_eq!(pool.status().ready, 0);
+
+
+			// so when we release the verification of the previous one it will have
+			// something in `requires`, but should go to ready directly, since the previous transaction was imported
+			// correctly.
+			tx.send(()).unwrap();
+
+			// then
+			is_ready.recv().unwrap(); // wait for finish
+			assert_eq!(pool.status().ready, 1);
+			assert_eq!(pool.status().future, 0);
+		}
 	}
 }

substrate/core/transaction-pool/graph/src/ready.rs

@@ -517,18 +517,18 @@ mod tests {
 		tx3.provides = vec![vec![4]];
 
 		// when
-		let x = WaitingTransaction::new(tx2, &ready.provided_tags());
+		let x = WaitingTransaction::new(tx2, &ready.provided_tags(), &[]);
 		ready.import(x).unwrap();
-		let x = WaitingTransaction::new(tx3, &ready.provided_tags());
+		let x = WaitingTransaction::new(tx3, &ready.provided_tags(), &[]);
 		ready.import(x).unwrap();
 		assert_eq!(ready.get().count(), 2);
 
 		// too low priority
-		let x = WaitingTransaction::new(tx1.clone(), &ready.provided_tags());
+		let x = WaitingTransaction::new(tx1.clone(), &ready.provided_tags(), &[]);
 		ready.import(x).unwrap_err();
 
 		tx1.priority = 10;
-		let x = WaitingTransaction::new(tx1.clone(), &ready.provided_tags());
+		let x = WaitingTransaction::new(tx1.clone(), &ready.provided_tags(), &[]);
 		ready.import(x).unwrap();
 
 		// then
@@ -562,15 +562,15 @@ mod tests {
 		};
 
 		// when
-		let x = WaitingTransaction::new(tx1, &ready.provided_tags());
+		let x = WaitingTransaction::new(tx1, &ready.provided_tags(), &[]);
 		ready.import(x).unwrap();
-		let x = WaitingTransaction::new(tx2, &ready.provided_tags());
+		let x = WaitingTransaction::new(tx2, &ready.provided_tags(), &[]);
 		ready.import(x).unwrap();
-		let x = WaitingTransaction::new(tx3, &ready.provided_tags());
+		let x = WaitingTransaction::new(tx3, &ready.provided_tags(), &[]);
 		ready.import(x).unwrap();
-		let x = WaitingTransaction::new(tx4, &ready.provided_tags());
+		let x = WaitingTransaction::new(tx4, &ready.provided_tags(), &[]);
 		ready.import(x).unwrap();
-		let x = WaitingTransaction::new(tx5, &ready.provided_tags());
+		let x = WaitingTransaction::new(tx5, &ready.provided_tags(), &[]);
 		ready.import(x).unwrap();
 
 		// then