ensure proposal evaluation occurs at most once per round

substrate/bft/src/generic/mod.rs

@@ -293,7 +293,7 @@ impl<D, S> Locked<D, S> {
 enum LocalState {
 	Start,
 	Proposed,
-	Prepared,
+	Prepared(bool), // whether we thought it valid.
 	Committed,
 	VoteAdvance,
 }
@@ -582,6 +582,7 @@ impl<C: Context> Strategy<C> {
 				Some(_) => {
 					// don't check validity if we are locked.
 					// this is necessary to preserve the liveness property.
+					self.local_state = LocalState::Prepared(true);
 					prepare_for = Some(digest);
 				}
 				None => {
@@ -591,6 +592,8 @@ impl<C: Context> Strategy<C> {
 
 					if let Async::Ready(valid) = res {
 						self.evaluating_proposal = None;
+						self.local_state = LocalState::Prepared(valid);
+
 						if valid {
 							prepare_for = Some(digest);
 						}
@@ -606,7 +609,6 @@ impl<C: Context> Strategy<C> {
 			).into();
 
 			self.import_and_send_message(message, context, sending);
-			self.local_state = LocalState::Prepared;
 		}
 
 		Ok(())
@@ -657,6 +659,12 @@ impl<C: Context> Strategy<C> {
 		// sent an AdvanceRound message yet, do so.
 		let mut attempt_advance = self.current_accumulator.advance_votes() > self.max_faulty;
 
+		// if we evaluated the proposal and it was bad, vote to advance round.
+		if let LocalState::Prepared(false) = self.local_state {
+			attempt_advance = true;
+		}
+
+		// if the timeout has fired, vote to advance round.
 		if let Async::Ready(_) = self.round_timeout.poll()? {
 			attempt_advance = true;
 		}

substrate/bft/src/generic/tests.rs

@@ -18,6 +18,7 @@
 
 use super::*;
 
+use std::collections::BTreeSet;
 use std::sync::{Arc, Mutex};
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::time::Duration;
@@ -117,6 +118,7 @@ struct TestContext {
 	node_count: usize,
 	current_round: Arc<AtomicUsize>,
 	timer: Timer,
+	evaluated: Mutex<BTreeSet<usize>>,
 }
 
 impl Context for TestContext {
@@ -137,7 +139,7 @@ impl Context for TestContext {
 		let proposal = {
 			let mut p = self.proposal.lock().unwrap();
 			let x = *p;
-			*p = (*p * 2) + 1;
+			*p += self.node_count;
 			x
 		};
 
@@ -175,6 +177,10 @@ impl Context for TestContext {
 	}
 
 	fn proposal_valid(&self, proposal: &Candidate) -> FutureResult<bool, Error> {
+		if !self.evaluated.lock().unwrap().insert(proposal.0) {
+			panic!("Evaluated proposal {:?} twice", proposal.0);
+		}
+
 		Ok(proposal.0 % 3 != 0).into_future()
 	}
 
@@ -230,6 +236,64 @@ fn consensus_completes_with_minimum_good() {
 				proposal: Mutex::new(i),
 				current_round: Arc::new(AtomicUsize::new(0)),
 				timer: timer.clone(),
+				evaluated: Mutex::new(BTreeSet::new()),
+				node_count,
+			};
+
+			agree(
+				ctx,
+				node_count,
+				max_faulty,
+				rx.map_err(|_| Error),
+				tx.sink_map_err(|_| Error).with(move |t| Ok((i, t))),
+			)
+		})
+		.collect::<Vec<_>>();
+
+	let timeout = timeout_in(Duration::from_millis(500)).map_err(|_| Error);
+	let results = ::futures::future::join_all(nodes)
+		.map(Some)
+		.select(timeout.map(|_| None))
+		.wait()
+		.map(|(i, _)| i)
+		.map_err(|(e, _)| e)
+		.expect("to complete")
+		.expect("to not time out");
+
+	for result in &results {
+		assert_eq!(&result.justification.digest, &results[0].justification.digest);
+	}
+}
+
+#[test]
+fn consensus_completes_with_minimum_good_all_initial_proposals_bad() {
+	let node_count = 10;
+	let max_faulty = 3;
+
+	let timer = tokio_timer::wheel().tick_duration(ROUND_DURATION).build();
+
+	let (network, net_send, net_recv) = Network::new(node_count);
+	network.route_on_thread();
+
+	let nodes = net_send
+		.into_iter()
+		.zip(net_recv)
+		.take(node_count - max_faulty)
+		.enumerate()
+		.map(|(i, (tx, rx))| {
+			// the first 5 proposals are going to be bad.
+			let proposal = if i < 5 {
+				i * 3 // proposals considered bad in the tests if they are % 3
+			} else {
+				(i * 3) + 1
+			};
+
+			let ctx = TestContext {
+				local_id: AuthorityId(i),
+				proposal: Mutex::new(proposal),
+				current_round: Arc::new(AtomicUsize::new(0)),
+				timer: timer.clone(),
+				evaluated: Mutex::new(BTreeSet::new()),
 				node_count,
 			};
 
@@ -279,6 +343,7 @@ fn consensus_does_not_complete_without_enough_nodes() {
 				proposal: Mutex::new(i),
 				current_round: Arc::new(AtomicUsize::new(0)),
 				timer: timer.clone(),
+				evaluated: Mutex::new(BTreeSet::new()),
 				node_count,
 			};
 
@@ -335,6 +400,7 @@ fn threshold_plus_one_locked_on_proposal_only_one_with_candidate() {
 				proposal: Mutex::new(i),
 				current_round: Arc::new(AtomicUsize::new(locked_round + 1)),
 				timer: timer.clone(),
+				evaluated: Mutex::new(BTreeSet::new()),
 				node_count,
 			};
 			let mut agreement = agree(
@@ -367,7 +433,7 @@ fn threshold_plus_one_locked_on_proposal_only_one_with_candidate() {
 		})
 		.collect::<Vec<_>>();
 
-	let timeout = timeout_in(Duration::from_millis(500)).map_err(|_| Error);
+	let timeout = timeout_in(Duration::from_millis(1000)).map_err(|_| Error);
 	let results = ::futures::future::join_all(nodes)
 		.map(Some)
 		.select(timeout.map(|_| None))
@@ -404,6 +470,7 @@ fn consensus_completes_even_when_nodes_start_with_a_delay() {
 				proposal: Mutex::new(i),
 				current_round: Arc::new(AtomicUsize::new(0)),
 				timer: timer.clone(),
+				evaluated: Mutex::new(BTreeSet::new()),
 				node_count,
 			};