slots: incrementally backoff claiming slots if finality lags behind

bin/node-template/node/src/service.rs

@@ -111,6 +111,7 @@ pub fn new_full(config: Configuration) -> Result<TaskManager, ServiceError> {
 
 	let role = config.role.clone();
 	let force_authoring = config.force_authoring;
+	let backoff_authoring_blocks = None;
 	let name = config.network.node_name.clone();
 	let enable_grandpa = !config.disable_grandpa;
 	let prometheus_registry = config.prometheus_registry().cloned();
@@ -164,6 +165,7 @@ pub fn new_full(config: Configuration) -> Result<TaskManager, ServiceError> {
 			network.clone(),
 			inherent_data_providers.clone(),
 			force_authoring,
+			backoff_authoring_blocks,
 			keystore_container.sync_keystore(),
 			can_author_with,
 		)?;

bin/node/cli/Cargo.toml

@@ -64,6 +64,7 @@ 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

@@ -204,6 +204,8 @@ pub fn new_full_base(
 
 	let role = config.role.clone();
 	let force_authoring = config.force_authoring;
+	let backoff_authoring_blocks =
+		Some(sc_consensus_slots::SimpleBackoffAuthoringBlocksStrategy::default());
 	let name = config.network.node_name.clone();
 	let enable_grandpa = !config.disable_grandpa;
 	let prometheus_registry = config.prometheus_registry().cloned();
@@ -249,6 +251,7 @@ 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

@@ -59,7 +59,7 @@ use sp_core::crypto::Public;
 use sp_application_crypto::{AppKey, AppPublic};
 use sp_runtime::{
 	generic::{BlockId, OpaqueDigestItemId},
-	Justification,
+	traits::NumberFor, Justification,
 };
 use sp_runtime::traits::{Block as BlockT, Header, DigestItemFor, Zero, Member};
 use sp_api::ProvideRuntimeApi;
@@ -73,6 +73,7 @@ use sc_telemetry::{telemetry, CONSENSUS_TRACE, CONSENSUS_DEBUG, CONSENSUS_INFO};
 
 use sc_consensus_slots::{
 	CheckedHeader, SlotInfo, SlotCompatible, StorageChanges, check_equivocation,
+	BackoffAuthoringBlocksStrategy, SimpleBackoffAuthoringBlocksStrategy,
 };
 
 use sp_api::ApiExt;
@@ -147,11 +148,12 @@ pub fn start_aura<B, C, SC, E, I, P, SO, CAW, Error>(
 	sync_oracle: SO,
 	inherent_data_providers: InherentDataProviders,
 	force_authoring: bool,
+	backoff_authoring_blocks: Option<SimpleBackoffAuthoringBlocksStrategy<NumberFor<B>>>,
 	keystore: SyncCryptoStorePtr,
 	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,
@@ -171,6 +173,7 @@ pub fn start_aura<B, C, SC, E, I, P, SO, CAW, Error>(
 		keystore,
 		sync_oracle: sync_oracle.clone(),
 		force_authoring,
+		backoff_authoring_blocks,
 		_key_type: PhantomData::<P>,
 	};
 	register_aura_inherent_data_provider(
@@ -188,20 +191,21 @@ pub fn start_aura<B, C, SC, E, I, P, SO, CAW, Error>(
 	))
 }
 
-struct AuraWorker<C, E, I, P, SO> {
+struct AuraWorker<B: BlockT, C, E, I, P, SO> {
 	client: Arc<C>,
 	block_import: Arc<Mutex<I>>,
 	env: E,
 	keystore: SyncCryptoStorePtr,
 	sync_oracle: SO,
 	force_authoring: bool,
+	backoff_authoring_blocks: Option<sc_consensus_slots::SimpleBackoffAuthoringBlocksStrategy<NumberFor<B>>>,
 	_key_type: PhantomData<P>,
 }
 
-impl<B, C, E, I, P, Error, SO> sc_consensus_slots::SimpleSlotWorker<B> for AuraWorker<C, E, I, P, SO>
+impl<B, C, E, I, P, Error, SO> sc_consensus_slots::SimpleSlotWorker<B> for AuraWorker<B, C, E, I, P, SO>
 where
 	B: BlockT,
-	C: ProvideRuntimeApi<B> + BlockOf + ProvideCache<B> + Sync,
+	C: ProvideRuntimeApi<B> + BlockOf + ProvideCache<B> + HeaderBackend<B> + Sync,
 	C::Api: AuraApi<B, AuthorityId<P>>,
 	E: Environment<B, Error = Error>,
 	E::Proposer: Proposer<B, Error = Error, Transaction = sp_api::TransactionFor<C, B>>,
@@ -316,6 +320,20 @@ where
 		self.force_authoring
 	}
 
+	fn should_backoff(&self, slot_number: u64, chain_head: &B::Header) -> bool {
+		if let Some(ref strategy) = self.backoff_authoring_blocks {
+			if let Ok(chain_head_slot) = find_pre_digest::<B, P>(chain_head) {
+				return strategy.should_backoff(
+					*chain_head.number(),
+					chain_head_slot,
+					self.client.info().finalized_number,
+					slot_number,
+				);
+			}
+		}
+		false
+	}
+
 	fn sync_oracle(&mut self) -> &mut Self::SyncOracle {
 		&mut self.sync_oracle
 	}
@@ -1021,6 +1039,7 @@ mod tests {
 				DummyOracle,
 				inherent_data_providers,
 				false,
+				Some(SimpleBackoffAuthoringBlocksStrategy::default()),
 				keystore,
 				sp_consensus::AlwaysCanAuthor,
 			).expect("Starts aura"));
@@ -1081,6 +1100,7 @@ mod tests {
 			keystore: keystore.into(),
 			sync_oracle: DummyOracle.clone(),
 			force_authoring: false,
+			backoff_authoring_blocks: Some(SimpleBackoffAuthoringBlocksStrategy::default()),
 			_key_type: PhantomData::<AuthorityPair>,
 		};
 

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::{
 	SlotInfo, SlotCompatible, StorageChanges, CheckedHeader, check_equivocation,
+	BackoffAuthoringBlocksStrategy, SimpleBackoffAuthoringBlocksStrategy,
 };
 use sc_consensus_epochs::{
 	descendent_query, SharedEpochChanges, EpochChangesFor, Epoch as EpochT, ViableEpochDescriptor,
@@ -381,6 +382,9 @@ 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<NumberFor<B>>>,
+
 	/// The source of timestamps for relative slots
 	pub babe_link: BabeLink<B>,
 
@@ -398,6 +402,7 @@ 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<
@@ -426,6 +431,7 @@ 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(),
@@ -496,6 +502,7 @@ struct BabeSlotWorker<B: BlockT, C, E, I, SO> {
 	env: E,
 	sync_oracle: SO,
 	force_authoring: bool,
+	backoff_authoring_blocks: Option<SimpleBackoffAuthoringBlocksStrategy<NumberFor<B>>>,
 	keystore: SyncCryptoStorePtr,
 	epoch_changes: SharedEpochChanges<B, Epoch>,
 	slot_notification_sinks: SlotNotificationSinks<B>,
@@ -657,6 +664,22 @@ impl<B, C, E, I, Error, SO> sc_consensus_slots::SimpleSlotWorker<B> for BabeSlot
 		self.force_authoring
 	}
 
+	fn should_backoff(&self, slot_number: u64, chain_head: &B::Header) -> bool {
+		if let Some(ref strategy) = self.backoff_authoring_blocks {
+			if let Ok(chain_head_slot) = find_pre_digest::<B>(chain_head)
+				.map(|digest| digest.slot_number())
+			{
+				return strategy.should_backoff(
+					*chain_head.number(),
+					chain_head_slot,
+					self.client.info().finalized_number,
+					slot_number,
+				);
+			}
+		}
+		false
+	}
+
 	fn sync_oracle(&mut self) -> &mut Self::SyncOracle {
 		&mut self.sync_oracle
 	}

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: Some(SimpleBackoffAuthoringBlocksStrategy::default()),
 			babe_link: data.link.clone(),
 			keystore,
 			can_author_with: sp_consensus::AlwaysCanAuthor,

client/consensus/slots/Cargo.toml

@@ -19,6 +19,7 @@ sc-client-api = { version = "2.0.0", path = "../../api" }
 sp-core = { version = "2.0.0", path = "../../../primitives/core" }
 sp-trie = { version = "2.0.0", path = "../../../primitives/trie" }
 sp-application-crypto = { version = "2.0.0", path = "../../../primitives/application-crypto" }
+sp-arithmetic = { version = "2.0.0", path = "../../../primitives/arithmetic" }
 sp-blockchain = { version = "2.0.0", path = "../../../primitives/blockchain" }
 sp-consensus-slots = { version = "0.8.0", path = "../../../primitives/consensus/slots" }
 sp-runtime = { version = "2.0.0", path = "../../../primitives/runtime" }