Reduce consensus gossip spam (#1538)

* core: keep known gossip messages for twice their expiration

* core: test expiration of known gossip messages

* core: only broadcast grandpa votes if authority in current set

* core: only broadcast grandpa commits if authority in current set

substrate/core/finality-grandpa/src/communication.rs

@@ -395,14 +395,16 @@ pub(crate) struct CommitsOut<Block, N> {
 	network: N,
 	set_id: u64,
 	_marker: ::std::marker::PhantomData<Block>,
+	is_voter: bool,
 }
 
 impl<Block, N> CommitsOut<Block, N> {
 	/// Create a new commit output stream.
-	pub(crate) fn new(network: N, set_id: u64) -> Self {
+	pub(crate) fn new(network: N, set_id: u64, is_voter: bool) -> Self {
 		CommitsOut {
 			network,
 			set_id,
+			is_voter,
 			_marker: Default::default(),
 		}
 	}
@@ -413,6 +415,10 @@ impl<Block: BlockT, N: Network> Sink for CommitsOut<Block, N> {
 	type SinkError = Error;
 
 	fn start_send(&mut self, input: (u64, Commit<Block>)) -> StartSend<Self::SinkItem, Error> {
+		if !self.is_voter {
+			return Ok(AsyncSink::Ready);
+		}
+
 		let (round, commit) = input;
 		let (precommits, auth_data) = commit.precommits.into_iter()
 			.map(|signed| (signed.precommit, (signed.signature, signed.id)))

substrate/core/finality-grandpa/src/lib.rs

@@ -528,10 +528,13 @@ impl<B, E, Block: BlockT<Hash=H256>, N, RA> voter::Environment<Block::Hash, Numb
 			self.voters.clone(),
 		);
 
+		let local_key = self.config.local_key.as_ref()
+			.filter(|pair| self.voters.contains_key(&pair.public().into()));
+
 		let (out_rx, outgoing) = ::communication::outgoing_messages::<Block, _>(
 			round,
 			self.set_id,
-			self.config.local_key.clone(),
+			local_key.cloned(),
 			self.voters.clone(),
 			self.network.clone(),
 		);
@@ -1407,6 +1410,7 @@ pub fn block_import<B, E, Block: BlockT<Hash=H256>, RA, PRA>(
 }
 
 fn committer_communication<Block: BlockT<Hash=H256>, B, E, N, RA>(
+	local_key: Option<Arc<ed25519::Pair>>,
 	set_id: u64,
 	voters: &Arc<HashMap<Ed25519AuthorityId, u64>>,
 	client: &Arc<Client<B, E, Block, RA>>,
@@ -1442,9 +1446,14 @@ fn committer_communication<Block: BlockT<Hash=H256>, B, E, N, RA>(
 		commit_in,
 	);
 
+	let is_voter = local_key
+		.map(|pair| voters.contains_key(&pair.public().into()))
+		.unwrap_or(false);
+
 	let commit_out = ::communication::CommitsOut::<Block, _>::new(
 		network.clone(),
 		set_id,
+		is_voter,
 	);
 
 	let commit_in = commit_in.map_err(Into::into);
@@ -1524,6 +1533,7 @@ pub fn run_grandpa<B, E, Block: BlockT<Hash=H256>, N, RA>(
 		);
 
 		let committer_data = committer_communication(
+			config.local_key.clone(),
 			env.set_id,
 			&env.voters,
 			&client,