slots: incrementally backoff claiming slots if finality lags behind

bin/node/cli/Cargo.toml

@@ -65,6 +65,7 @@ sc-chain-spec = { version = "2.0.0", path = "../../../client/chain-spec" }
 sc-consensus = { version = "0.8.0", path = "../../../client/consensus/common" }
 sc-transaction-pool = { version = "2.0.0", path = "../../../client/transaction-pool" }
 sc-network = { version = "0.8.0", path = "../../../client/network" }
+sc-consensus-slots = { version = "0.8.0", path = "../../../client/consensus/slots" }
 sc-consensus-babe = { version = "0.8.0", path = "../../../client/consensus/babe" }
 grandpa = { version = "0.8.0", package = "sc-finality-grandpa", path = "../../../client/finality-grandpa" }
 sc-client-db = { version = "0.8.0", default-features = false, path = "../../../client/db" }

bin/node/cli/src/service.rs

@@ -237,6 +237,12 @@ pub fn new_full_base(
 		let can_author_with =
 			sp_consensus::CanAuthorWithNativeVersion::new(client.executor().clone());
 
+		let backoff_authoring_blocks = Some(sc_consensus_slots::SimpleBackoffAuthoringBlocksStrategy {
+			max_interval: 100,
+			unfinalized_slack: 5,
+			authoring_bias: 2,
+		});
+
 		let babe_config = sc_consensus_babe::BabeParams {
 			keystore: keystore_container.sync_keystore(),
 			client: client.clone(),
@@ -246,6 +252,7 @@ pub fn new_full_base(
 			sync_oracle: network.clone(),
 			inherent_data_providers: inherent_data_providers.clone(),
 			force_authoring,
+			backoff_authoring_blocks,
 			babe_link,
 			can_author_with,
 		};

client/consensus/aura/src/lib.rs

@@ -151,7 +151,7 @@ pub fn start_aura<B, C, SC, E, I, P, SO, CAW, Error>(
 	can_author_with: CAW,
 ) -> Result<impl Future<Output = ()>, sp_consensus::Error> where
 	B: BlockT,
-	C: ProvideRuntimeApi<B> + BlockOf + ProvideCache<B> + AuxStore + Send + Sync,
+	C: ProvideRuntimeApi<B> + BlockOf + ProvideCache<B> + AuxStore + HeaderBackend<B> + Send + Sync,
 	C::Api: AuraApi<B, AuthorityId<P>>,
 	SC: SelectChain<B>,
 	E: Environment<B, Error = Error> + Send + Sync + 'static,
@@ -219,6 +219,7 @@ impl<B, C, E, I, P, Error, SO> sc_consensus_slots::SimpleSlotWorker<B> for AuraW
 	type Proposer = E::Proposer;
 	type Claim = P::Public;
 	type EpochData = Vec<AuthorityId<P>>;
+	type BackoffAuthoringBlocksStrategy = sc_consensus_slots::SimpleBackoffAuthoringBlocksStrategy<B>;
 
 	fn logging_target(&self) -> &'static str {
 		"aura"
@@ -328,7 +329,7 @@ impl<B, C, E, I, P, Error, SO> sc_consensus_slots::SimpleSlotWorker<B> for AuraW
 	fn proposing_remaining_duration(
 		&self,
 		head: &B::Header,
-		slot_info: &SlotInfo,
+		slot_info: &SlotInfo<B>,
 	) -> Option<std::time::Duration> {
 		let slot_remaining = self.slot_remaining_duration(slot_info);
 
@@ -355,7 +356,7 @@ impl<B, C, E, I, P, Error, SO> sc_consensus_slots::SimpleSlotWorker<B> for AuraW
 
 impl<B: BlockT, C, E, I, P, Error, SO> SlotWorker<B> for AuraWorker<C, E, I, P, SO> where
 	B: BlockT,
-	C: ProvideRuntimeApi<B> + BlockOf + ProvideCache<B> + Sync + Send,
+	C: ProvideRuntimeApi<B> + BlockOf + ProvideCache<B> + Sync + Send + HeaderBackend<B>,
 	C::Api: AuraApi<B, AuthorityId<P>>,
 	E: Environment<B, Error = Error> + Send + Sync,
 	E::Proposer: Proposer<B, Error = Error, Transaction = sp_api::TransactionFor<C, B>>,
@@ -368,7 +369,19 @@ impl<B: BlockT, C, E, I, P, Error, SO> SlotWorker<B> for AuraWorker<C, E, I, P,
 {
 	type OnSlot = Pin<Box<dyn Future<Output = Result<(), sp_consensus::Error>> + Send>>;
 
-	fn on_slot(&mut self, chain_head: B::Header, slot_info: SlotInfo) -> Self::OnSlot {
+	fn on_slot(&mut self, chain_head: B::Header, slot_info: SlotInfo<B>) -> Self::OnSlot {
+		// Append SlotInfo with chain info for use by the (optional) BackoffAuthoringBlockStrategy
+		let mut slot_info = slot_info.clone();
+		slot_info.chain_info = find_pre_digest::<B, P>(&chain_head)
+			.map(|chain_head_slot| {
+				sc_consensus_slots::AppendedChainInfo::<B> {
+					chain_head_number: *chain_head.number(),
+					chain_head_slot,
+					finalized_number: self.client.info().finalized_number,
+				}
+			})
+			.ok();
+
 		<Self as sc_consensus_slots::SimpleSlotWorker<B>>::on_slot(self, chain_head, slot_info)
 	}
 }

client/consensus/babe/src/lib.rs

@@ -114,6 +114,7 @@ use log::{debug, info, log, trace, warn};
 use prometheus_endpoint::Registry;
 use sc_consensus_slots::{
 	SlotWorker, SlotInfo, SlotCompatible, StorageChanges, CheckedHeader, check_equivocation,
+	SimpleBackoffAuthoringBlocksStrategy,
 };
 use sc_consensus_epochs::{
 	descendent_query, SharedEpochChanges, EpochChangesFor, Epoch as EpochT, ViableEpochDescriptor,
@@ -353,6 +354,9 @@ pub struct BabeParams<B: BlockT, C, E, I, SO, SC, CAW> {
 	/// Force authoring of blocks even if we are offline
 	pub force_authoring: bool,
 
+	/// Strategy and parameters for backing off block production if finality starts to lag behind.
+	pub backoff_authoring_blocks: Option<SimpleBackoffAuthoringBlocksStrategy<B>>,
+
 	/// The source of timestamps for relative slots
 	pub babe_link: BabeLink<B>,
 
@@ -370,6 +374,7 @@ pub fn start_babe<B, C, SC, E, I, SO, CAW, Error>(BabeParams {
 	sync_oracle,
 	inherent_data_providers,
 	force_authoring,
+	backoff_authoring_blocks,
 	babe_link,
 	can_author_with,
 }: BabeParams<B, C, E, I, SO, SC, CAW>) -> Result<
@@ -398,6 +403,7 @@ pub fn start_babe<B, C, SC, E, I, SO, CAW, Error>(BabeParams {
 		env,
 		sync_oracle: sync_oracle.clone(),
 		force_authoring,
+		backoff_authoring_blocks,
 		keystore,
 		epoch_changes: babe_link.epoch_changes.clone(),
 		slot_notification_sinks: slot_notification_sinks.clone(),
@@ -468,6 +474,7 @@ struct BabeSlotWorker<B: BlockT, C, E, I, SO> {
 	env: E,
 	sync_oracle: SO,
 	force_authoring: bool,
+	backoff_authoring_blocks: Option<SimpleBackoffAuthoringBlocksStrategy<B>>,
 	keystore: SyncCryptoStorePtr,
 	epoch_changes: SharedEpochChanges<B, Epoch>,
 	slot_notification_sinks: SlotNotificationSinks<B>,
@@ -495,6 +502,7 @@ impl<B, C, E, I, Error, SO> sc_consensus_slots::SimpleSlotWorker<B> for BabeSlot
 	>>;
 	type Proposer = E::Proposer;
 	type BlockImport = I;
+	type BackoffAuthoringBlocksStrategy = sc_consensus_slots::SimpleBackoffAuthoringBlocksStrategy<B>;
 
 	fn logging_target(&self) -> &'static str {
 		"babe"
@@ -629,6 +637,10 @@ impl<B, C, E, I, Error, SO> sc_consensus_slots::SimpleSlotWorker<B> for BabeSlot
 		self.force_authoring
 	}
 
+	fn backoff_authoring_blocks_strategy(&self) -> Option<&Self::BackoffAuthoringBlocksStrategy> {
+		self.backoff_authoring_blocks.as_ref()
+	}
+
 	fn sync_oracle(&mut self) -> &mut Self::SyncOracle {
 		&mut self.sync_oracle
 	}
@@ -642,7 +654,7 @@ impl<B, C, E, I, Error, SO> sc_consensus_slots::SimpleSlotWorker<B> for BabeSlot
 	fn proposing_remaining_duration(
 		&self,
 		head: &B::Header,
-		slot_info: &SlotInfo,
+		slot_info: &SlotInfo<B>,
 	) -> Option<std::time::Duration> {
 		let slot_remaining = self.slot_remaining_duration(slot_info);
 
@@ -682,7 +694,20 @@ impl<B, C, E, I, Error, SO> SlotWorker<B> for BabeSlotWorker<B, C, E, I, SO> whe
 {
 	type OnSlot = Pin<Box<dyn Future<Output = Result<(), sp_consensus::Error>> + Send>>;
 
-	fn on_slot(&mut self, chain_head: B::Header, slot_info: SlotInfo) -> Self::OnSlot {
+	fn on_slot(&mut self, chain_head: B::Header, slot_info: SlotInfo<B>) -> Self::OnSlot {
+		// Append SlotInfo with chain info
+		let mut slot_info = slot_info.clone();
+		slot_info.chain_info = find_pre_digest::<B>(&chain_head)
+			.map(|digest| digest.slot_number())
+			.map(|chain_head_slot| {
+				sc_consensus_slots::AppendedChainInfo::<B> {
+					chain_head_number: *chain_head.number(),
+					chain_head_slot,
+					finalized_number: self.client.info().finalized_number,
+				}
+			})
+			.ok();
+
 		<Self as sc_consensus_slots::SimpleSlotWorker<B>>::on_slot(self, chain_head, slot_info)
 	}
 }

client/consensus/babe/src/tests.rs

@@ -434,6 +434,7 @@ fn run_one_test(
 			sync_oracle: DummyOracle,
 			inherent_data_providers: data.inherent_data_providers.clone(),
 			force_authoring: false,
+			backoff_authoring_blocks: None,
 			babe_link: data.link.clone(),
 			keystore,
 			can_author_with: sp_consensus::AlwaysCanAuthor,