Time-based transaction banning (#594) (#602)

* Allow replacing transactions.

* Clear old transactions and ban them temporarily.

* Move to a separate module and add some tests.

* Add bound to banned transactions.

* Remove unnecessary block and double PoolRotator.

substrate/substrate/extrinsic-pool/src/lib.rs

@@ -37,6 +37,7 @@ pub mod watcher;
 mod error;
 mod listener;
 mod pool;
+mod rotator;
 
 pub use listener::Listener;
 pub use pool::{Pool, ChainApi, EventStream, Verified, VerifiedFor, ExtrinsicFor, ExHash, AllExtrinsics};

substrate/substrate/extrinsic-pool/src/pool.rs

@@ -14,15 +14,21 @@
 // You should have received a copy of the GNU General Public License
 // along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
 
-use std::{ collections::HashMap, fmt, sync::Arc, collections::BTreeMap};
+use std::{
+	collections::{BTreeMap, HashMap},
+	fmt,
+	sync::Arc,
+	time,
+};
 use futures::sync::mpsc;
 use parking_lot::{Mutex, RwLock};
 use serde::{Serialize, de::DeserializeOwned};
 use txpool::{self, Scoring, Readiness};
 
-use listener::Listener;
-use watcher::Watcher;
 use error::IntoPoolError;
+use listener::Listener;
+use rotator::PoolRotator;
+use watcher::Watcher;
 
 use runtime_primitives::{generic::BlockId, traits::Block as BlockT};
 
@@ -40,16 +46,18 @@ pub type AllExtrinsics<A> = BTreeMap<<<A as ChainApi>::VEx as txpool::VerifiedTr
 
 /// Verified extrinsic struct. Wraps original extrinsic and verification info.
 #[derive(Debug)]
-pub struct Verified<Ex: ::std::fmt::Debug, VEx: txpool::VerifiedTransaction> {
+pub struct Verified<Ex, VEx> {
 	/// Original extrinsic.
 	pub original: Ex,
 	/// Verification data.
 	pub verified: VEx,
+	/// Pool deadline, after it's reached we remove the extrinsic from the pool.
+	pub valid_till: time::Instant,
 }
 
-impl<Ex, VEx> txpool::VerifiedTransaction for Verified<Ex, VEx> 
-where 
-	Ex: ::std::fmt::Debug,
+impl<Ex, VEx> txpool::VerifiedTransaction for Verified<Ex, VEx>
+where
+	Ex: fmt::Debug,
 	VEx: txpool::VerifiedTransaction,
 {
 	type Hash = <VEx as txpool::VerifiedTransaction>::Hash;
@@ -118,10 +126,17 @@ pub struct Ready<'a, 'b, B: 'a + ChainApi> {
 	api: &'a B,
 	at: &'b BlockId<B::Block>,
 	context: B::Ready,
+	rotator: &'a PoolRotator<B::Hash>,
+	now: time::Instant,
 }
 
 impl<'a, 'b, B: ChainApi> txpool::Ready<VerifiedFor<B>> for Ready<'a, 'b, B> {
 	fn is_ready(&mut self, xt: &VerifiedFor<B>) -> Readiness {
+		if self.rotator.ban_if_stale(&self.now, xt) {
+			debug!(target: "extrinsic-pool", "[{:?}] Banning as stale.", txpool::VerifiedTransaction::hash(xt));
+			return Readiness::Stale;
+		}
+
 		self.api.is_ready(self.at, &mut self.context, xt)
 	}
 }
@@ -155,6 +170,11 @@ impl<T: ChainApi> Scoring<VerifiedFor<T>> for ScoringAdapter<T> {
 	}
 }
 
+/// Maximum time the transaction will be kept in the pool.
+///
+/// Transactions that don't get included within the limit are removed from the pool.
+const POOL_TIME: time::Duration = time::Duration::from_secs(60 * 5);
+
 /// Extrinsics pool.
 pub struct Pool<B: ChainApi> {
 	api: B,
@@ -164,6 +184,7 @@ pub struct Pool<B: ChainApi> {
 		Listener<B::Hash>,
 	>>,
 	import_notification_sinks: Mutex<Vec<mpsc::UnboundedSender<()>>>,
+	rotator: PoolRotator<B::Hash>,
 }
 
 impl<B: ChainApi> Pool<B> {
@@ -173,6 +194,7 @@ impl<B: ChainApi> Pool<B> {
 			pool: RwLock::new(txpool::Pool::new(Listener::default(), ScoringAdapter::<B>(Default::default()), options)),
 			import_notification_sinks: Default::default(),
 			api,
+			rotator: Default::default(),
 		}
 	}
 
@@ -206,9 +228,20 @@ impl<B: ChainApi> Pool<B> {
 	{
 		xts
 			.into_iter()
-			.map(|xt| (self.api.verify_transaction(at, &xt), xt))
+			.map(|xt| {
+				match self.api.verify_transaction(at, &xt) {
+					Ok(ref verified) if self.rotator.is_banned(txpool::VerifiedTransaction::hash(verified)) => {
+						return (Err(txpool::Error::from("Temporarily Banned".to_owned()).into()), xt)
+					},
+					result => (result, xt),
+				}
+			})
 			.map(|(v, xt)| {
-				let xt = Verified { original: xt, verified: v? };
+				let xt = Verified {
+					original: xt,
+					verified: v?,
+					valid_till: time::Instant::now() + POOL_TIME,
+				};
 				Ok(self.pool.write().import(xt)?)
 			})
 			.collect()
@@ -216,9 +249,7 @@ impl<B: ChainApi> Pool<B> {
 
 	/// Imports one unverified extrinsic to the pool
 	pub fn submit_one(&self, at: &BlockId<B::Block>, xt: ExtrinsicFor<B>) -> Result<Arc<VerifiedFor<B>>, B::Error>  {
-		let v = self.api.verify_transaction(at, &xt)?;
-		let xt = Verified { original: xt, verified: v };
-		Ok(self.pool.write().import(xt)?)
+		Ok(self.submit_at(at, ::std::iter::once(xt))?.pop().expect("One extrinsic passed; one result returned; qed"))
 	}
 
 	/// Import a single extrinsic and starts to watch their progress in the pool.
@@ -244,7 +275,8 @@ impl<B: ChainApi> Pool<B> {
 		senders: Option<&[<B::VEx as txpool::VerifiedTransaction>::Sender]>,
 	) -> usize
 	{
-		let ready = Ready { api: &self.api, context: self.api.ready(), at };
+		self.rotator.clear_timeouts(&time::Instant::now());
+		let ready = self.ready(at);
 		self.pool.write().cull(senders, ready)
 	}
 
@@ -284,9 +316,9 @@ impl<B: ChainApi> Pool<B> {
 	pub fn pending<F, T>(&self, at: &BlockId<B::Block>, f: F) -> T where
 		F: FnOnce(txpool::PendingIterator<VerifiedFor<B>, Ready<B>, ScoringAdapter<B>, Listener<B::Hash>>) -> T,
 	{
-		let ready = Ready { api: &self.api, context: self.api.ready(), at };
+		let ready = self.ready(at);
 		f(self.pool.read().pending(ready))
-	}	
+	}
 
 	/// Retry to import all verified transactions from given sender.
 	pub fn retry_verification(&self, at: &BlockId<B::Block>, sender: <B::VEx as txpool::VerifiedTransaction>::Sender) -> Result<(), B::Error> {
@@ -326,6 +358,16 @@ impl<B: ChainApi> Pool<B> {
 			map
 		})
 	}
+
+	fn ready<'a, 'b>(&'a self, at: &'b BlockId<B::Block>) -> Ready<'a, 'b, B> {
+		Ready {
+			api: &self.api,
+			rotator: &self.rotator,
+			context: self.api.ready(),
+			at,
+			now: time::Instant::now(),
+		}
+	}
 }
 
  /// A Readiness implementation that returns `Ready` for all transactions.
@@ -337,7 +379,7 @@ impl<VEx> txpool::Ready<VEx> for AlwaysReady {
 }
 
 #[cfg(test)]
-mod tests {
+pub mod tests {
 	use txpool;
 	use super::{VerifiedFor, ExtrinsicFor};
 	use std::collections::HashMap;
@@ -353,9 +395,9 @@ mod tests {
 
 	#[derive(Clone, Debug)]
 	pub struct VerifiedTransaction {
-		hash: Hash,
-		sender: AccountId,
-		nonce: u64,
+		pub hash: Hash,
+		pub sender: AccountId,
+		pub nonce: u64,
 	}
 
 	impl txpool::VerifiedTransaction for VerifiedTransaction {
@@ -419,7 +461,7 @@ mod tests {
 
 			result
 		}
-		
+
 		fn ready(&self) -> Self::Ready {
 			HashMap::default()
 		}

substrate/substrate/extrinsic-pool/src/rotator.rs

@@ -0,0 +1,177 @@
+// Copyright 2018 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Rotate extrinsic inside the pool.
+//!
+//! Keeps only recent extrinsic and discard the ones kept for a significant amount of time.
+//! Discarded extrinsics are banned so that they don't get re-imported again.
+
+use std::{
+	collections::HashMap,
+	fmt,
+	hash,
+	time::{Duration, Instant},
+};
+use parking_lot::RwLock;
+use txpool::VerifiedTransaction;
+use Verified;
+
+/// Expected size of the banned extrinsics cache.
+const EXPECTED_SIZE: usize = 2048;
+
+/// Pool rotator is responsible to only keep fresh extrinsics in the pool.
+///
+/// Extrinsics that occupy the pool for too long are culled and temporarily banned from entering
+/// the pool again.
+pub struct PoolRotator<Hash> {
+	/// How long the extrinsic is banned for.
+	ban_time: Duration,
+	/// Currently banned extrinsics.
+	banned_until: RwLock<HashMap<Hash, Instant>>,
+}
+
+impl<Hash: hash::Hash + Eq> Default for PoolRotator<Hash> {
+	fn default() -> Self {
+		PoolRotator {
+			ban_time: Duration::from_secs(60 * 30),
+			banned_until: Default::default(),
+		}
+	}
+}
+
+impl<Hash: hash::Hash + Eq + Clone> PoolRotator<Hash> {
+	/// Returns `true` if extrinsic hash is currently banned.
+	pub fn is_banned(&self, hash: &Hash) -> bool {
+		self.banned_until.read().contains_key(hash)
+	}
+
+	/// Bans extrinsic if it's stale.
+	///
+	/// Returns `true` if extrinsic is stale and got banned.
+	pub fn ban_if_stale<Ex, VEx>(&self, now: &Instant, xt: &Verified<Ex, VEx>) -> bool where
+		VEx: VerifiedTransaction<Hash=Hash>,
+		Hash: fmt::Debug + fmt::LowerHex,
+	{
+		if &xt.valid_till > now {
+			return false;
+		}
+
+		let mut banned = self.banned_until.write();
+		banned.insert(xt.verified.hash().clone(), *now + self.ban_time);
+
+		if banned.len() > 2 * EXPECTED_SIZE {
+			while banned.len() > EXPECTED_SIZE {
+				if let Some(key) = banned.keys().next().cloned() {
+					banned.remove(&key);
+				}
+			}
+		}
+
+		true
+	}
+
+	/// Removes timed bans.
+	pub fn clear_timeouts(&self, now: &Instant) {
+		let mut banned = self.banned_until.write();
+
+		let to_remove = banned
+			.iter()
+			.filter_map(|(k, v)| if v < now {
+				Some(k.clone())
+			} else {
+				None
+			}).collect::<Vec<_>>();
+
+		for k in to_remove {
+			banned.remove(&k);
+		}
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+	use pool::tests::VerifiedTransaction;
+	use test_client::runtime::Hash;
+
+	fn rotator() -> PoolRotator<Hash> {
+		PoolRotator {
+			ban_time: Duration::from_millis(10),
+			..Default::default()
+		}
+	}
+
+	fn tx() -> (Hash, Verified<u64, VerifiedTransaction>) {
+		let hash = 5.into();
+		let tx = Verified {
+			original: 5,
+			verified: VerifiedTransaction {
+				hash,
+				sender: Default::default(),
+				nonce: Default::default(),
+			},
+			valid_till: Instant::now(),
+		};
+
+		(hash, tx)
+	}
+
+	#[test]
+	fn should_not_ban_if_not_stale() {
+		// given
+		let (hash, tx) = tx();
+		let rotator = rotator();
+		assert!(!rotator.is_banned(&hash));
+		let past = Instant::now() - Duration::from_millis(1000);
+
+		// when
+		assert!(!rotator.ban_if_stale(&past, &tx));
+
+		// then
+		assert!(!rotator.is_banned(&hash));
+	}
+
+	#[test]
+	fn should_ban_stale_extrinsic() {
+		// given
+		let (hash, tx) = tx();
+		let rotator = rotator();
+		assert!(!rotator.is_banned(&hash));
+
+		// when
+		assert!(rotator.ban_if_stale(&Instant::now(), &tx));
+
+		// then
+		assert!(rotator.is_banned(&hash));
+	}
+
+
+	#[test]
+	fn should_clear_banned() {
+		// given
+		let (hash, tx) = tx();
+		let rotator = rotator();
+		assert!(rotator.ban_if_stale(&Instant::now(), &tx));
+		assert!(rotator.is_banned(&hash));
+
+		// when
+		let future = Instant::now() + rotator.ban_time + rotator.ban_time;
+		rotator.clear_timeouts(&future);
+
+		// then
+		assert!(!rotator.is_banned(&hash));
+	}
+}