Move authorities interface from Core to consensus (#1412)

* Move authorities interface from Core to consensus f * notify all caches of block insert + create with up-to-date best_fin * merged authorities_are_cached from light_grandpa_import2 * Add ProvideCache trait * Create helper function for 'get_cache' * Fix some formatting * Bump impl version * Resolve wasm conflicts * Apply review comments * Use try_for_each * Move authorities interface from Core to consensus f * notify all caches of block insert + create with up-to-date best_fin * merged authorities_are_cached from light_grandpa_import2 * Add ProvideCache trait * Create helper function for 'get_cache' * Fix some formatting * Bump impl version * Resolve wasm conflicts * Apply review comments * Use try_for_each * Move authorities interface from Core to consensus f * notify all caches of block insert + create with up-to-date best_fin * merged authorities_are_cached from light_grandpa_import2 * Add ProvideCache trait * Create helper function for 'get_cache' * Fix some formatting * Bump impl version * Resolve wasm conflicts * Apply review comments * Use try_for_each * Increment impl_version * Update lib.rs
2026-05-09 18:47:59 +00:00 · 2019-03-29 18:41:22 +02:00
parent 55788fdf77
commit cbfc36b39f
44 changed files with 650 additions and 409 deletions
@@ -1973,6 +1973,7 @@ dependencies = [
 "srml-treasury 0.1.0",
 "substrate-client 0.1.0",
 "substrate-consensus-aura-primitives 0.1.0",
+ "substrate-consensus-authorities 0.1.0",
 "substrate-keyring 0.1.0",
 "substrate-offchain-primitives 0.1.0",
 "substrate-primitives 0.1.0",
@@ -2030,6 +2031,7 @@ dependencies = [
 "srml-timestamp 0.1.0",
 "substrate-client 0.1.0",
 "substrate-consensus-aura-primitives 0.1.0",
+ "substrate-consensus-authorities 0.1.0",
 "substrate-offchain-primitives 0.1.0",
 "substrate-primitives 0.1.0",
 ]
@@ -3713,6 +3715,7 @@ dependencies = [
 "parking_lot 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)",
 "sr-primitives 0.1.0",
 "substrate-client 0.1.0",
+ "substrate-consensus-common 0.1.0",
 "substrate-executor 0.1.0",
 "substrate-keyring 0.1.0",
 "substrate-primitives 0.1.0",
@@ -3741,6 +3744,7 @@ dependencies = [
 "substrate-client 0.1.0",
 "substrate-consensus-aura-primitives 0.1.0",
 "substrate-consensus-aura-slots 0.1.0",
+ "substrate-consensus-authorities 0.1.0",
 "substrate-consensus-common 0.1.0",
 "substrate-executor 0.1.0",
 "substrate-inherents 0.1.0",
@@ -3779,6 +3783,20 @@ dependencies = [
 "tokio 0.1.15 (registry+https://github.com/rust-lang/crates.io-index)",
 ]

+[[package]]
+name = "substrate-consensus-authorities"
+version = "0.1.0"
+dependencies = [
+ "parity-codec 3.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sr-io 0.1.0",
+ "sr-primitives 0.1.0",
+ "sr-std 0.1.0",
+ "sr-version 0.1.0",
+ "srml-support 0.1.0",
+ "substrate-client 0.1.0",
+ "substrate-primitives 0.1.0",
+]
+
 [[package]]
 name = "substrate-consensus-common"
 version = "0.1.0"
@@ -4251,6 +4269,7 @@ dependencies = [
 "srml-support 0.1.0",
 "substrate-client 0.1.0",
 "substrate-consensus-aura-primitives 0.1.0",
+ "substrate-consensus-authorities 0.1.0",
 "substrate-executor 0.1.0",
 "substrate-inherents 0.1.0",
 "substrate-keyring 0.1.0",
@@ -63,10 +63,6 @@ impl_runtime_apis! {
 			VERSION
 		}

-		fn authorities() -> Vec<SessionKey> {
-			Consensus::authorities()
-		}
-
 		fn execute_block(block: Block) {
 			Executive::execute_block(block)
 		}
@@ -26,6 +26,7 @@ trie = { package = "substrate-trie", path = "../../trie" }
 kvdb-memorydb = { git = "https://github.com/paritytech/parity-common", rev="b0317f649ab2c665b7987b8475878fc4d2e1f81d" }
 substrate-keyring = { path = "../../keyring" }
 test-client = { package = "substrate-test-client", path = "../../test-client" }
+consensus_common = { package = "substrate-consensus-common", path = "../../consensus/common" }
 env_logger = { version = "0.6" }

 [features]
@@ -16,7 +16,7 @@

 //! DB-backed cache of blockchain data.

-use std::sync::Arc;
+use std::{sync::Arc, collections::HashMap};
 use parking_lot::RwLock;

 use kvdb::{KeyValueDB, DBTransaction};
@@ -25,7 +25,7 @@ use client::blockchain::Cache as BlockchainCache;
 use client::error::Result as ClientResult;
 use parity_codec::{Encode, Decode};
 use runtime_primitives::generic::BlockId;
-use runtime_primitives::traits::{Block as BlockT, Header as HeaderT, NumberFor, As, AuthorityIdFor};
+use runtime_primitives::traits::{Block as BlockT, Header as HeaderT, NumberFor, As};
 use crate::utils::{self, COLUMN_META};

 use self::list_cache::ListCache;
@@ -64,7 +64,12 @@ impl<T> CacheItemT for T where T: Clone + Decode + Encode + PartialEq {}

 /// Database-backed blockchain data cache.
 pub struct DbCache<Block: BlockT> {
-	authorities_at: ListCache<Block, Vec<AuthorityIdFor<Block>>, self::list_storage::DbStorage>,
+	cache_at: HashMap<Vec<u8>, ListCache<Block, Vec<u8>, self::list_storage::DbStorage>>,
+	db: Arc<KeyValueDB>,
+	key_lookup_column: Option<u32>,
+	header_column: Option<u32>,
+	authorities_column: Option<u32>,
+	best_finalized_block: ComplexBlockId<Block>,
 }

 impl<Block: BlockT> DbCache<Block> {
@@ -76,19 +81,13 @@ impl<Block: BlockT> DbCache<Block> {
 		authorities_column: Option<u32>,
 		best_finalized_block: ComplexBlockId<Block>,
 	) -> Self {
-		DbCache {
-			authorities_at: ListCache::new(
-				self::list_storage::DbStorage::new(b"auth".to_vec(), db,
-					self::list_storage::DbColumns {
-						meta: COLUMN_META,
-						key_lookup: key_lookup_column,
-						header: header_column,
-						cache: authorities_column,
-					},
-				),
-				As::sa(PRUNE_DEPTH),
-				best_finalized_block,
-			),
+		Self {
+			cache_at: HashMap::new(),
+			db,
+			key_lookup_column,
+			header_column,
+			authorities_column,
+			best_finalized_block,
 		}
 	}

@@ -97,35 +96,82 @@ impl<Block: BlockT> DbCache<Block> {
 		DbCacheTransaction {
 			cache: self,
 			tx,
-			authorities_at_op: None,
+			cache_at_op: HashMap::new(),
+			best_finalized_block: None,
 		}
 	}

 	/// Run post-commit cache operations.
 	pub fn commit(&mut self, ops: DbCacheTransactionOps<Block>) {
-		if let Some(authorities_at_op) = ops.authorities_at_op {
-			self.authorities_at.on_transaction_commit(authorities_at_op);
+		for (name, op) in ops.cache_at_op.into_iter() {
+			self.get_cache(name).on_transaction_commit(op);
+		}
+		if let Some(best_finalized_block) = ops.best_finalized_block {
+			self.best_finalized_block = best_finalized_block;
 		}
 	}
+
+	/// Creates `ListCache` with the given name or returns a reference to the existing.
+	fn get_cache(&mut self, name: Vec<u8>) -> &mut ListCache<Block, Vec<u8>, self::list_storage::DbStorage> {
+		get_cache_helper(
+			&mut self.cache_at,
+			name,
+			&self.db,
+			self.key_lookup_column,
+			self.header_column,
+			self.authorities_column,
+			&self.best_finalized_block
+		)
+	}
+}
+
+// This helper is needed because otherwise the borrow checker will require to
+// clone all parameters outside of the closure.
+fn get_cache_helper<'a, Block: BlockT>(
+	cache_at: &'a mut HashMap<Vec<u8>, ListCache<Block, Vec<u8>, self::list_storage::DbStorage>>,
+	name: Vec<u8>,
+	db: &Arc<KeyValueDB>,
+	key_lookup: Option<u32>,
+	header: Option<u32>,
+	cache: Option<u32>,
+	best_finalized_block: &ComplexBlockId<Block>,
+) -> &'a mut ListCache<Block, Vec<u8>, self::list_storage::DbStorage> {
+	cache_at.entry(name.clone()).or_insert_with(|| {
+		ListCache::new(
+			self::list_storage::DbStorage::new(name, db.clone(),
+				self::list_storage::DbColumns {
+					meta: COLUMN_META,
+					key_lookup,
+					header,
+					cache,
+				},
+			),
+			As::sa(PRUNE_DEPTH),
+			best_finalized_block.clone(),
+		)
+	})
 }

 /// Cache operations that are to be committed after database transaction is committed.
 pub struct DbCacheTransactionOps<Block: BlockT> {
-	authorities_at_op: Option<self::list_cache::CommitOperation<Block, Vec<AuthorityIdFor<Block>>>>,
+	cache_at_op: HashMap<Vec<u8>, self::list_cache::CommitOperation<Block, Vec<u8>>>,
+	best_finalized_block: Option<ComplexBlockId<Block>>,
 }

 /// Database-backed blockchain data cache transaction valid for single block import.
 pub struct DbCacheTransaction<'a, Block: BlockT> {
 	cache: &'a mut DbCache<Block>,
 	tx: &'a mut DBTransaction,
-	authorities_at_op: Option<self::list_cache::CommitOperation<Block, Vec<AuthorityIdFor<Block>>>>,
+	cache_at_op: HashMap<Vec<u8>, self::list_cache::CommitOperation<Block, Vec<u8>>>,
+	best_finalized_block: Option<ComplexBlockId<Block>>,
 }

 impl<'a, Block: BlockT> DbCacheTransaction<'a, Block> {
 	/// Convert transaction into post-commit operations set.
 	pub fn into_ops(self) -> DbCacheTransactionOps<Block> {
 		DbCacheTransactionOps {
-			authorities_at_op: self.authorities_at_op,
+			cache_at_op: self.cache_at_op,
+			best_finalized_block: self.best_finalized_block,
 		}
 	}

@@ -134,21 +180,42 @@ impl<'a, Block: BlockT> DbCacheTransaction<'a, Block> {
 		mut self,
 		parent: ComplexBlockId<Block>,
 		block: ComplexBlockId<Block>,
-		authorities_at: Option<Vec<AuthorityIdFor<Block>>>,
+		data_at: HashMap<Vec<u8>, Vec<u8>>,
 		is_final: bool,
 	) -> ClientResult<Self> {
-		assert!(self.authorities_at_op.is_none());
+		assert!(self.cache_at_op.is_empty());

-		self.authorities_at_op = self.cache.authorities_at.on_block_insert(
-			&mut self::list_storage::DbStorageTransaction::new(
-				self.cache.authorities_at.storage(),
-				&mut self.tx
-			),
-			parent,
-			block,
-			authorities_at,
-			is_final,
-		)?;
+		// prepare list of caches that are not update
+		// (we might still need to do some cache maintenance in this case)
+		let missed_caches = self.cache.cache_at.keys()
+			.filter(|cache| !data_at.contains_key(cache.clone()))
+			.cloned()
+			.collect::<Vec<_>>();
+
+		let mut insert_op = |name: Vec<u8>, value: Option<Vec<u8>>| -> Result<(), client::error::Error> {
+			let cache = self.cache.get_cache(name.clone());
+			let op = cache.on_block_insert(
+				&mut self::list_storage::DbStorageTransaction::new(
+					cache.storage(),
+					&mut self.tx,
+				),
+				parent.clone(),
+				block.clone(),
+				value.or(cache.value_at_block(&parent)?),
+				is_final,
+			)?;
+			if let Some(op) = op {
+				self.cache_at_op.insert(name, op);
+			}
+			Ok(())
+		};
+
+		data_at.into_iter().try_for_each(|(name, data)| insert_op(name, Some(data)))?;
+		missed_caches.into_iter().try_for_each(|name| insert_op(name, None))?;
+
+		if is_final {
+			self.best_finalized_block = Some(block);
+		}

 		Ok(self)
 	}
@@ -159,16 +226,24 @@ impl<'a, Block: BlockT> DbCacheTransaction<'a, Block> {
 		parent: ComplexBlockId<Block>,
 		block: ComplexBlockId<Block>
 	) -> ClientResult<Self> {
-		assert!(self.authorities_at_op.is_none());
+		assert!(self.cache_at_op.is_empty());

-		self.authorities_at_op = self.cache.authorities_at.on_block_finalize(
-			&mut self::list_storage::DbStorageTransaction::new(
-				self.cache.authorities_at.storage(),
-				&mut self.tx
-			),
-			parent,
-			block,
-		)?;
+		for (name, cache_at) in self.cache.cache_at.iter() {
+			let op = cache_at.on_block_finalize(
+				&mut self::list_storage::DbStorageTransaction::new(
+					cache_at.storage(),
+					&mut self.tx
+				),
+				parent.clone(),
+				block.clone(),
+			)?;
+
+			if let Some(op) = op {
+				self.cache_at_op.insert(name.to_owned(), op);
+			}
+		}
+
+		self.best_finalized_block = Some(block);

 		Ok(self)
 	}
@@ -178,12 +253,12 @@ impl<'a, Block: BlockT> DbCacheTransaction<'a, Block> {
 pub struct DbCacheSync<Block: BlockT>(pub RwLock<DbCache<Block>>);

 impl<Block: BlockT> BlockchainCache<Block> for DbCacheSync<Block> {
-	fn authorities_at(&self, at: BlockId<Block>) -> Option<Vec<AuthorityIdFor<Block>>> {
+	fn get_at(&self, key: &[u8], at: &BlockId<Block>) -> Option<Vec<u8>> {
 		let cache = self.0.read();
-		let storage = cache.authorities_at.storage();
+		let storage = cache.cache_at.get(key)?.storage();
 		let db = storage.db();
 		let columns = storage.columns();
-		let at = match at {
+		let at = match *at {
 			BlockId::Hash(hash) => {
 				let header = utils::read_header::<Block>(
 					&**db,
@@ -202,6 +277,7 @@ impl<Block: BlockT> BlockchainCache<Block> for DbCacheSync<Block> {
 			},
 		};

-		cache.authorities_at.value_at_block(&at).ok()?
+		cache.cache_at.get(key)?.value_at_block(&at).ok()?
 	}
 }
+
@@ -33,6 +33,7 @@ mod utils;
 use std::sync::Arc;
 use std::path::PathBuf;
 use std::io;
+use std::collections::HashMap;

 use client::backend::NewBlockState;
 use client::blockchain::HeaderBackend;
@@ -45,7 +46,7 @@ use parking_lot::RwLock;
 use primitives::{H256, Blake2Hasher, ChangesTrieConfiguration, convert_hash};
 use primitives::storage::well_known_keys;
 use runtime_primitives::{generic::BlockId, Justification, StorageOverlay, ChildrenStorageOverlay};
-use runtime_primitives::traits::{Block as BlockT, Header as HeaderT, As, NumberFor, Zero, Digest, DigestItem, AuthorityIdFor};
+use runtime_primitives::traits::{Block as BlockT, Header as HeaderT, As, NumberFor, Zero, Digest, DigestItem};
 use runtime_primitives::BuildStorage;
 use state_machine::backend::Backend as StateBackend;
 use executor::RuntimeInfo;
@@ -243,7 +244,7 @@ impl<Block: BlockT> client::blockchain::Backend<Block> for BlockchainDb<Block> {
 		Ok(self.meta.read().finalized_hash.clone())
 	}

-	fn cache(&self) -> Option<&client::blockchain::Cache<Block>> {
+	fn cache(&self) -> Option<Arc<client::blockchain::Cache<Block>>> {
 		None
 	}

@@ -256,6 +257,12 @@ impl<Block: BlockT> client::blockchain::Backend<Block> for BlockchainDb<Block> {
 	}
 }

+impl<Block: BlockT> client::blockchain::ProvideCache<Block> for BlockchainDb<Block> {
+	fn cache(&self) -> Option<Arc<client::blockchain::Cache<Block>>> {
+		None
+	}
+}
+
 /// Database transaction
 pub struct BlockImportOperation<Block: BlockT, H: Hasher> {
 	old_state: CachingState<Blake2Hasher, DbState, Block>,
@@ -306,8 +313,8 @@ where Block: BlockT<Hash=H256>,
 		Ok(())
 	}

-	fn update_authorities(&mut self, _authorities: Vec<AuthorityIdFor<Block>>) {
-		// currently authorities are not cached on full nodes
+	fn update_cache(&mut self, _cache: HashMap<Vec<u8>, Vec<u8>>) {
+		// Currently cache isn't implemented on full nodes.
 	}

 	fn update_db_storage(&mut self, update: PrefixedMemoryDB<Blake2Hasher>) -> Result<(), client::error::Error> {
@@ -16,7 +16,7 @@

 //! RocksDB-based light client blockchain storage.

-use std::sync::Arc;
+use std::{sync::Arc, collections::HashMap};
 use parking_lot::RwLock;

 use kvdb::{KeyValueDB, DBTransaction};
@@ -32,7 +32,7 @@ use parity_codec::{Decode, Encode};
 use primitives::Blake2Hasher;
 use runtime_primitives::generic::BlockId;
 use runtime_primitives::traits::{Block as BlockT, Header as HeaderT,
-	Zero, One, As, NumberFor, Digest, DigestItem, AuthorityIdFor};
+	Zero, One, As, NumberFor, Digest, DigestItem};
 use crate::cache::{DbCacheSync, DbCache, ComplexBlockId};
 use crate::utils::{self, meta_keys, Meta, db_err, open_database,
 	read_db, block_id_to_lookup_key, read_meta};
@@ -59,7 +59,7 @@ pub struct LightStorage<Block: BlockT> {
 	db: Arc<KeyValueDB>,
 	meta: RwLock<Meta<NumberFor<Block>, Block::Hash>>,
 	leaves: RwLock<LeafSet<Block::Hash, NumberFor<Block>>>,
-	cache: DbCacheSync<Block>,
+	cache: Arc<DbCacheSync<Block>>,
 }

 impl<Block> LightStorage<Block>
@@ -96,7 +96,7 @@ impl<Block> LightStorage<Block>
 		Ok(LightStorage {
 			db,
 			meta: RwLock::new(meta),
-			cache: DbCacheSync(RwLock::new(cache)),
+			cache: Arc::new(DbCacheSync(RwLock::new(cache))),
 			leaves: RwLock::new(leaves),
 		})
 	}
@@ -370,7 +370,7 @@ impl<Block> LightBlockchainStorage<Block> for LightStorage<Block>
 	fn import_header(
 		&self,
 		header: Block::Header,
-		authorities: Option<Vec<AuthorityIdFor<Block>>>,
+		cache_at: HashMap<Vec<u8>, Vec<u8>>,
 		leaf_state: NewBlockState,
 		aux_ops: Vec<(Vec<u8>, Option<Vec<u8>>)>,
 	) -> ClientResult<()> {
@@ -432,7 +432,7 @@ impl<Block> LightBlockchainStorage<Block> for LightStorage<Block>
 				.on_block_insert(
 					ComplexBlockId::new(*header.parent_hash(), if number.is_zero() { Zero::zero() } else { number - One::one() }),
 					ComplexBlockId::new(hash, number),
-					authorities,
+					cache_at,
 					finalized,
 				)?
 				.into_ops();
@@ -521,8 +521,8 @@ impl<Block> LightBlockchainStorage<Block> for LightStorage<Block>
 		Ok(self.meta.read().finalized_hash.clone())
 	}

-	fn cache(&self) -> Option<&BlockchainCache<Block>> {
-		Some(&self.cache)
+	fn cache(&self) -> Option<Arc<BlockchainCache<Block>>> {
+		Some(self.cache.clone())
 	}
 }

@@ -538,6 +538,8 @@ pub(crate) mod tests {
 	use client::cht;
 	use runtime_primitives::generic::DigestItem;
 	use runtime_primitives::testing::{H256 as Hash, Header, Block as RawBlock, ExtrinsicWrapper};
+	use runtime_primitives::traits::AuthorityIdFor;
+	use consensus_common::well_known_cache_keys;
 	use super::*;

 	type Block = RawBlock<ExtrinsicWrapper<u32>>;
@@ -567,41 +569,41 @@ pub(crate) mod tests {

 	pub fn insert_block<F: Fn() -> Header>(
 		db: &LightStorage<Block>,
-		authorities: Option<Vec<AuthorityIdFor<Block>>>,
+		cache: HashMap<Vec<u8>, Vec<u8>>,
 		header: F,
 	) -> Hash {
 		let header = header();
 		let hash = header.hash();
-		db.import_header(header, authorities, NewBlockState::Best, Vec::new()).unwrap();
+		db.import_header(header, cache, NewBlockState::Best, Vec::new()).unwrap();
 		hash
 	}

 	fn insert_final_block<F: Fn() -> Header>(
 		db: &LightStorage<Block>,
-		authorities: Option<Vec<AuthorityIdFor<Block>>>,
+		cache: HashMap<Vec<u8>, Vec<u8>>,
 		header: F,
 	) -> Hash {
 		let header = header();
 		let hash = header.hash();
-		db.import_header(header, authorities, NewBlockState::Final, Vec::new()).unwrap();
+		db.import_header(header, cache, NewBlockState::Final, Vec::new()).unwrap();
 		hash
 	}

 	fn insert_non_best_block<F: Fn() -> Header>(
 		db: &LightStorage<Block>,
-		authorities: Option<Vec<AuthorityIdFor<Block>>>,
+		cache: HashMap<Vec<u8>, Vec<u8>>,
 		header: F,
 	) -> Hash {
 		let header = header();
 		let hash = header.hash();
-		db.import_header(header, authorities, NewBlockState::Normal, Vec::new()).unwrap();
+		db.import_header(header, cache, NewBlockState::Normal, Vec::new()).unwrap();
 		hash
 	}

 	#[test]
 	fn returns_known_header() {
 		let db = LightStorage::new_test();
-		let known_hash = insert_block(&db, None, || default_header(&Default::default(), 0));
+		let known_hash = insert_block(&db, HashMap::new(), || default_header(&Default::default(), 0));
 		let header_by_hash = db.header(BlockId::Hash(known_hash)).unwrap().unwrap();
 		let header_by_number = db.header(BlockId::Number(0)).unwrap().unwrap();
 		assert_eq!(header_by_hash, header_by_number);
@@ -617,12 +619,12 @@ pub(crate) mod tests {
 	#[test]
 	fn returns_info() {
 		let db = LightStorage::new_test();
-		let genesis_hash = insert_block(&db, None, || default_header(&Default::default(), 0));
+		let genesis_hash = insert_block(&db, HashMap::new(), || default_header(&Default::default(), 0));
 		let info = db.info().unwrap();
 		assert_eq!(info.best_hash, genesis_hash);
 		assert_eq!(info.best_number, 0);
 		assert_eq!(info.genesis_hash, genesis_hash);
-		let best_hash = insert_block(&db, None, || default_header(&genesis_hash, 1));
+		let best_hash = insert_block(&db, HashMap::new(), || default_header(&genesis_hash, 1));
 		let info = db.info().unwrap();
 		assert_eq!(info.best_hash, best_hash);
 		assert_eq!(info.best_number, 1);
@@ -632,7 +634,7 @@ pub(crate) mod tests {
 	#[test]
 	fn returns_block_status() {
 		let db = LightStorage::new_test();
-		let genesis_hash = insert_block(&db, None, || default_header(&Default::default(), 0));
+		let genesis_hash = insert_block(&db, HashMap::new(), || default_header(&Default::default(), 0));
 		assert_eq!(db.status(BlockId::Hash(genesis_hash)).unwrap(), BlockStatus::InChain);
 		assert_eq!(db.status(BlockId::Number(0)).unwrap(), BlockStatus::InChain);
 		assert_eq!(db.status(BlockId::Hash(Hash::from_low_u64_be(1))).unwrap(), BlockStatus::Unknown);
@@ -642,7 +644,7 @@ pub(crate) mod tests {
 	#[test]
 	fn returns_block_hash() {
 		let db = LightStorage::new_test();
-		let genesis_hash = insert_block(&db, None, || default_header(&Default::default(), 0));
+		let genesis_hash = insert_block(&db, HashMap::new(), || default_header(&Default::default(), 0));
 		assert_eq!(db.hash(0).unwrap(), Some(genesis_hash));
 		assert_eq!(db.hash(1).unwrap(), None);
 	}
@@ -651,11 +653,11 @@ pub(crate) mod tests {
 	fn import_header_works() {
 		let db = LightStorage::new_test();

-		let genesis_hash = insert_block(&db, None, || default_header(&Default::default(), 0));
+		let genesis_hash = insert_block(&db, HashMap::new(), || default_header(&Default::default(), 0));
 		assert_eq!(db.db.iter(columns::HEADER).count(), 1);
 		assert_eq!(db.db.iter(columns::KEY_LOOKUP).count(), 2);

-		let _ = insert_block(&db, None, || default_header(&genesis_hash, 1));
+		let _ = insert_block(&db, HashMap::new(), || default_header(&genesis_hash, 1));
 		assert_eq!(db.db.iter(columns::HEADER).count(), 2);
 		assert_eq!(db.db.iter(columns::KEY_LOOKUP).count(), 4);
 	}
@@ -666,25 +668,25 @@ pub(crate) mod tests {
 			let db = LightStorage::new_test();

 			// insert genesis block header (never pruned)
-			let mut prev_hash = insert_final_block(&db, None, || header_producer(&Default::default(), 0));
+			let mut prev_hash = insert_final_block(&db, HashMap::new(), || header_producer(&Default::default(), 0));

 			// insert SIZE blocks && ensure that nothing is pruned
 			for number in 0..cht::SIZE {
-				prev_hash = insert_block(&db, None, || header_producer(&prev_hash, 1 + number));
+				prev_hash = insert_block(&db, HashMap::new(), || header_producer(&prev_hash, 1 + number));
 			}
 			assert_eq!(db.db.iter(columns::HEADER).count(), (1 + cht::SIZE) as usize);
 			assert_eq!(db.db.iter(columns::CHT).count(), 0);

 			// insert next SIZE blocks && ensure that nothing is pruned
 			for number in 0..cht::SIZE {
-				prev_hash = insert_block(&db, None, || header_producer(&prev_hash, 1 + cht::SIZE + number));
+				prev_hash = insert_block(&db, HashMap::new(), || header_producer(&prev_hash, 1 + cht::SIZE + number));
 			}
 			assert_eq!(db.db.iter(columns::HEADER).count(), (1 + cht::SIZE + cht::SIZE) as usize);
 			assert_eq!(db.db.iter(columns::CHT).count(), 0);

 			// insert block #{2 * cht::SIZE + 1} && check that new CHT is created + headers of this CHT are pruned
 			// nothing is yet finalized, so nothing is pruned.
-			prev_hash = insert_block(&db, None, || header_producer(&prev_hash, 1 + cht::SIZE + cht::SIZE));
+			prev_hash = insert_block(&db, HashMap::new(), || header_producer(&prev_hash, 1 + cht::SIZE + cht::SIZE));
 			assert_eq!(db.db.iter(columns::HEADER).count(), (2 + cht::SIZE + cht::SIZE) as usize);
 			assert_eq!(db.db.iter(columns::CHT).count(), 0);

@@ -733,9 +735,9 @@ pub(crate) mod tests {
 		let db = LightStorage::new_test();

 		// insert 1 + SIZE + SIZE + 1 blocks so that CHT#0 is created
-		let mut prev_hash = insert_final_block(&db, None, || header_with_changes_trie(&Default::default(), 0));
+		let mut prev_hash = insert_final_block(&db, HashMap::new(), || header_with_changes_trie(&Default::default(), 0));
 		for i in 1..1 + cht::SIZE + cht::SIZE + 1 {
-			prev_hash = insert_block(&db, None, || header_with_changes_trie(&prev_hash, i as u64));
+			prev_hash = insert_block(&db, HashMap::new(), || header_with_changes_trie(&prev_hash, i as u64));
 			db.finalize_header(BlockId::Hash(prev_hash)).unwrap();
 		}

@@ -755,16 +757,16 @@ pub(crate) mod tests {
 	#[test]
 	fn tree_route_works() {
 		let db = LightStorage::new_test();
-		let block0 = insert_block(&db, None, || default_header(&Default::default(), 0));
+		let block0 = insert_block(&db, HashMap::new(), || default_header(&Default::default(), 0));

 		// fork from genesis: 3 prong.
-		let a1 = insert_block(&db, None, || default_header(&block0, 1));
-		let a2 = insert_block(&db, None, || default_header(&a1, 2));
-		let a3 = insert_block(&db, None, || default_header(&a2, 3));
+		let a1 = insert_block(&db, HashMap::new(), || default_header(&block0, 1));
+		let a2 = insert_block(&db, HashMap::new(), || default_header(&a1, 2));
+		let a3 = insert_block(&db, HashMap::new(), || default_header(&a2, 3));

 		// fork from genesis: 2 prong.
-		let b1 = insert_block(&db, None, || header_with_extrinsics_root(&block0, 1, Hash::from([1; 32])));
-		let b2 = insert_block(&db, None, || default_header(&b1, 2));
+		let b1 = insert_block(&db, HashMap::new(), || header_with_extrinsics_root(&block0, 1, Hash::from([1; 32])));
+		let b2 = insert_block(&db, HashMap::new(), || default_header(&b1, 2));

 		{
 			let tree_route = ::client::blockchain::tree_route(
@@ -816,44 +818,64 @@ pub(crate) mod tests {
 	}

 	#[test]
-	fn authorites_are_cached() {
+	fn authorities_are_cached() {
 		let db = LightStorage::new_test();

 		fn run_checks(db: &LightStorage<Block>, max: u64, checks: &[(u64, Option<Vec<AuthorityIdFor<Block>>>)]) {
 			for (at, expected) in checks.iter().take_while(|(at, _)| *at <= max) {
-				let actual = db.cache().authorities_at(BlockId::Number(*at));
+				let actual = get_authorities(db.cache(), BlockId::Number(*at));
 				assert_eq!(*expected, actual);
 			}
 		}

+		fn same_authorities() -> HashMap<Vec<u8>, Vec<u8>> {
+			HashMap::new()
+		}
+
+		fn make_authorities(authorities: Vec<AuthorityId>) -> HashMap<Vec<u8>, Vec<u8>> {
+			let mut map = HashMap::new();
+			map.insert(well_known_cache_keys::AUTHORITIES.to_vec(), authorities.encode());
+			map
+		}
+
+		fn get_authorities(cache: &BlockchainCache<Block>, at: BlockId<Block>) -> Option<Vec<AuthorityId>> {
+			cache.get_at(well_known_cache_keys::AUTHORITIES, &at).and_then(|val| Decode::decode(&mut &val[..]))
+		}
+
+		let auth1 = || AuthorityId::from_raw([1u8; 32]);
+		let auth2 = || AuthorityId::from_raw([2u8; 32]);
+		let auth3 = || AuthorityId::from_raw([3u8; 32]);
+		let auth4 = || AuthorityId::from_raw([4u8; 32]);
+		let auth5 = || AuthorityId::from_raw([5u8; 32]);
+		let auth6 = || AuthorityId::from_raw([6u8; 32]);
+
 		let (hash2, hash6) = {
 			// first few blocks are instantly finalized
-			// B0(None) -> B1(None) -> B2(1) -> B3(1) -> B4(1, 2) -> B5(1, 2) -> B6(None)
+			// B0(None) -> B1(None) -> B2(1) -> B3(1) -> B4(1, 2) -> B5(1, 2) -> B6(1, 2)
 			let checks = vec![
 				(0, None),
 				(1, None),
-				(2, Some(vec![AuthorityId::from_raw([1u8; 32])])),
-				(3, Some(vec![AuthorityId::from_raw([1u8; 32])])),
-				(4, Some(vec![AuthorityId::from_raw([1u8; 32]), AuthorityId::from_raw([2u8; 32])])),
-				(5, Some(vec![AuthorityId::from_raw([1u8; 32]), AuthorityId::from_raw([2u8; 32])])),
-				(6, None),
-				(7, None), // block will work for 'future' block too
+				(2, Some(vec![auth1()])),
+				(3, Some(vec![auth1()])),
+				(4, Some(vec![auth1(), auth2()])),
+				(5, Some(vec![auth1(), auth2()])),
+				(6, Some(vec![auth1(), auth2()])),
 			];

-			let hash0 = insert_final_block(&db, None, || default_header(&Default::default(), 0));
+			let hash0 = insert_final_block(&db, same_authorities(), || default_header(&Default::default(), 0));
 			run_checks(&db, 0, &checks);
-			let hash1 = insert_final_block(&db, None, || default_header(&hash0, 1));
+			let hash1 = insert_final_block(&db, same_authorities(), || default_header(&hash0, 1));
 			run_checks(&db, 1, &checks);
-			let hash2 = insert_final_block(&db, Some(vec![AuthorityId::from_raw([1u8; 32])]), || default_header(&hash1, 2));
+			let hash2 = insert_final_block(&db, make_authorities(vec![auth1()]), || default_header(&hash1, 2));
 			run_checks(&db, 2, &checks);
-			let hash3 = insert_final_block(&db, Some(vec![AuthorityId::from_raw([1u8; 32])]), || default_header(&hash2, 3));
+			let hash3 = insert_final_block(&db, make_authorities(vec![auth1()]), || default_header(&hash2, 3));
 			run_checks(&db, 3, &checks);
-			let hash4 = insert_final_block(&db, Some(vec![AuthorityId::from_raw([1u8; 32]), AuthorityId::from_raw([2u8; 32])]), || default_header(&hash3, 4));
+			let hash4 = insert_final_block(&db, make_authorities(vec![auth1(), auth2()]), || default_header(&hash3, 4));
 			run_checks(&db, 4, &checks);
-			let hash5 = insert_final_block(&db, Some(vec![AuthorityId::from_raw([1u8; 32]), AuthorityId::from_raw([2u8; 32])]), || default_header(&hash4, 5));
+			let hash5 = insert_final_block(&db, make_authorities(vec![auth1(), auth2()]), || default_header(&hash4, 5));
 			run_checks(&db, 5, &checks);
-			let hash6 = insert_final_block(&db, None, || default_header(&hash5, 6));
-			run_checks(&db, 7, &checks);
+			let hash6 = insert_final_block(&db, same_authorities(), || default_header(&hash5, 6));
+			run_checks(&db, 6, &checks);

 			(hash2, hash6)
 		};
@@ -862,10 +884,10 @@ pub(crate) mod tests {
 			// some older non-best blocks are inserted
 			// ... -> B2(1) -> B2_1(1) -> B2_2(2)
 			// => the cache ignores all writes before best finalized block
-			let hash2_1 = insert_non_best_block(&db, Some(vec![AuthorityId::from_raw([1u8; 32])]), || default_header(&hash2, 3));
-			assert_eq!(None, db.cache().authorities_at(BlockId::Hash(hash2_1)));
-			let hash2_2 = insert_non_best_block(&db, Some(vec![AuthorityId::from_raw([1u8; 32]), AuthorityId::from_raw([2u8; 32])]), || default_header(&hash2_1, 4));
-			assert_eq!(None, db.cache().authorities_at(BlockId::Hash(hash2_2)));
+			let hash2_1 = insert_non_best_block(&db, make_authorities(vec![auth1()]), || default_header(&hash2, 3));
+			assert_eq!(None, get_authorities(db.cache(), BlockId::Hash(hash2_1)));
+			let hash2_2 = insert_non_best_block(&db, make_authorities(vec![auth1(), auth2()]), || default_header(&hash2_1, 4));
+			assert_eq!(None, get_authorities(db.cache(), BlockId::Hash(hash2_2)));
 		}

 		let (hash7, hash8, hash6_1, hash6_2, hash6_1_1, hash6_1_2) = {
@@ -875,39 +897,57 @@ pub(crate) mod tests {
 			//                     \> B6_1_1(5)
 			//                     \> B6_1_2(6) -> B6_1_3(7)

-			let hash7 = insert_block(&db, Some(vec![AuthorityId::from_raw([3u8; 32])]), || default_header(&hash6, 7));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6)), None);
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash7)), Some(vec![AuthorityId::from_raw([3u8; 32])]));
-			let hash8 = insert_block(&db, Some(vec![AuthorityId::from_raw([3u8; 32])]), || default_header(&hash7, 8));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6)), None);
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash7)), Some(vec![AuthorityId::from_raw([3u8; 32])]));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash8)), Some(vec![AuthorityId::from_raw([3u8; 32])]));
-			let hash6_1 = insert_block(&db, Some(vec![AuthorityId::from_raw([4u8; 32])]), || default_header(&hash6, 7));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6)), None);
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash7)), Some(vec![AuthorityId::from_raw([3u8; 32])]));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash8)), Some(vec![AuthorityId::from_raw([3u8; 32])]));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6_1)), Some(vec![AuthorityId::from_raw([4u8; 32])]));
-			let hash6_1_1 = insert_non_best_block(&db, Some(vec![AuthorityId::from_raw([5u8; 32])]), || default_header(&hash6_1, 8));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6)), None);
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash7)), Some(vec![AuthorityId::from_raw([3u8; 32])]));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash8)), Some(vec![AuthorityId::from_raw([3u8; 32])]));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6_1)), Some(vec![AuthorityId::from_raw([4u8; 32])]));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6_1_1)), Some(vec![AuthorityId::from_raw([5u8; 32])]));
-			let hash6_1_2 = insert_non_best_block(&db, Some(vec![AuthorityId::from_raw([6u8; 32])]), || default_header(&hash6_1, 8));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6)), None);
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash7)), Some(vec![AuthorityId::from_raw([3u8; 32])]));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash8)), Some(vec![AuthorityId::from_raw([3u8; 32])]));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6_1)), Some(vec![AuthorityId::from_raw([4u8; 32])]));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6_1_1)), Some(vec![AuthorityId::from_raw([5u8; 32])]));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6_1_2)), Some(vec![AuthorityId::from_raw([6u8; 32])]));
-			let hash6_2 = insert_block(&db, Some(vec![AuthorityId::from_raw([4u8; 32])]), || default_header(&hash6_1, 8));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6)), None);
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash7)), Some(vec![AuthorityId::from_raw([3u8; 32])]));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash8)), Some(vec![AuthorityId::from_raw([3u8; 32])]));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6_1)), Some(vec![AuthorityId::from_raw([4u8; 32])]));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6_1_1)), Some(vec![AuthorityId::from_raw([5u8; 32])]));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6_1_2)), Some(vec![AuthorityId::from_raw([6u8; 32])]));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6_2)), Some(vec![AuthorityId::from_raw([4u8; 32])]));
+			let hash7 = insert_block(&db, make_authorities(vec![auth3()]), || default_header(&hash6, 7));
+			assert_eq!(
+				get_authorities(db.cache(), BlockId::Hash(hash6)),
+				Some(vec![auth1(), auth2()]),
+			);
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash7)), Some(vec![auth3()]));
+			let hash8 = insert_block(&db, make_authorities(vec![auth3()]), || default_header(&hash7, 8));
+			assert_eq!(
+				get_authorities(db.cache(), BlockId::Hash(hash6)),
+				Some(vec![auth1(), auth2()]),
+			);
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash7)), Some(vec![auth3()]));
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash8)), Some(vec![auth3()]));
+			let hash6_1 = insert_block(&db, make_authorities(vec![auth4()]), || default_header(&hash6, 7));
+			assert_eq!(
+				get_authorities(db.cache(), BlockId::Hash(hash6)),
+				Some(vec![auth1(), auth2()]),
+			);
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash7)), Some(vec![auth3()]));
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash8)), Some(vec![auth3()]));
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash6_1)), Some(vec![auth4()]));
+			let hash6_1_1 = insert_non_best_block(&db, make_authorities(vec![auth5()]), || default_header(&hash6_1, 8));
+			assert_eq!(
+				get_authorities(db.cache(), BlockId::Hash(hash6)),
+				Some(vec![auth1(), auth2()]),
+			);
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash7)), Some(vec![auth3()]));
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash8)), Some(vec![auth3()]));
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash6_1)), Some(vec![auth4()]));
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash6_1_1)), Some(vec![auth5()]));
+			let hash6_1_2 = insert_non_best_block(&db, make_authorities(vec![auth6()]), || default_header(&hash6_1, 8));
+			assert_eq!(
+				get_authorities(db.cache(), BlockId::Hash(hash6)),
+				Some(vec![auth1(), auth2()]),
+			);
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash7)), Some(vec![auth3()]));
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash8)), Some(vec![auth3()]));
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash6_1)), Some(vec![auth4()]));
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash6_1_1)), Some(vec![auth5()]));
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash6_1_2)), Some(vec![auth6()]));
+			let hash6_2 = insert_block(&db, make_authorities(vec![auth4()]), || default_header(&hash6_1, 8));
+			assert_eq!(
+				get_authorities(db.cache(), BlockId::Hash(hash6)),
+				Some(vec![auth1(), auth2()]),
+			);
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash7)), Some(vec![auth3()]));
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash8)), Some(vec![auth3()]));
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash6_1)), Some(vec![auth4()]));
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash6_1_1)), Some(vec![auth5()]));
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash6_1_2)), Some(vec![auth6()]));
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash6_2)), Some(vec![auth4()]));

 			(hash7, hash8, hash6_1, hash6_2, hash6_1_1, hash6_1_2)
 		};
@@ -915,29 +955,35 @@ pub(crate) mod tests {
 		{
 			// finalize block hash6_1
 			db.finalize_header(BlockId::Hash(hash6_1)).unwrap();
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6)), None);
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash7)), None);
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash8)), None);
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6_1)), Some(vec![AuthorityId::from_raw([4u8; 32])]));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6_1_1)), Some(vec![AuthorityId::from_raw([5u8; 32])]));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6_1_2)), Some(vec![AuthorityId::from_raw([6u8; 32])]));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6_2)), Some(vec![AuthorityId::from_raw([4u8; 32])]));
+			assert_eq!(
+				get_authorities(db.cache(), BlockId::Hash(hash6)),
+				Some(vec![auth1(), auth2()]),
+			);
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash7)), None);
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash8)), None);
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash6_1)), Some(vec![auth4()]));
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash6_1_1)), Some(vec![auth5()]));
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash6_1_2)), Some(vec![auth6()]));
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash6_2)), Some(vec![auth4()]));
 			// finalize block hash6_2
 			db.finalize_header(BlockId::Hash(hash6_2)).unwrap();
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6)), None);
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash7)), None);
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash8)), None);
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6_1)), Some(vec![AuthorityId::from_raw([4u8; 32])]));
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6_1_1)), None);
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6_1_2)), None);
-			assert_eq!(db.cache().authorities_at(BlockId::Hash(hash6_2)), Some(vec![AuthorityId::from_raw([4u8; 32])]));
+			assert_eq!(
+				get_authorities(db.cache(), BlockId::Hash(hash6)),
+				Some(vec![auth1(), auth2()]),
+			);
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash7)), None);
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash8)), None);
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash6_1)), Some(vec![auth4()]));
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash6_1_1)), None);
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash6_1_2)), None);
+			assert_eq!(get_authorities(db.cache(), BlockId::Hash(hash6_2)), Some(vec![auth4()]));
 		}
 	}

 	#[test]
 	fn database_is_reopened() {
 		let db = LightStorage::new_test();
-		let hash0 = insert_final_block(&db, None, || default_header(&Default::default(), 0));
+		let hash0 = insert_final_block(&db, HashMap::new(), || default_header(&Default::default(), 0));
 		assert_eq!(db.info().unwrap().best_hash, hash0);
 		assert_eq!(db.header(BlockId::Hash(hash0)).unwrap().unwrap().hash(), hash0);

@@ -960,7 +1006,7 @@ pub(crate) mod tests {
 		assert_eq!(db.get_aux(&[3]).unwrap(), None);

 		// delete aux1 + insert aux3 using import operation
-		db.import_header(default_header(&Default::default(), 0), None, NewBlockState::Best, vec![
+		db.import_header(default_header(&Default::default(), 0), HashMap::new(), NewBlockState::Best, vec![
 			(vec![3], Some(vec![103])),
 			(vec![1], None),
 		]).unwrap();
@@ -974,17 +1020,17 @@ pub(crate) mod tests {
 	#[test]
 	fn test_leaves_pruned_on_finality() {
 		let db = LightStorage::<Block>::new_test();
-		let block0 = insert_block(&db, None, || default_header(&Default::default(), 0));
+		let block0 = insert_block(&db, HashMap::new(), || default_header(&Default::default(), 0));

-		let block1_a = insert_block(&db, None, || default_header(&block0, 1));
-		let block1_b = insert_block(&db, None, || header_with_extrinsics_root(&block0, 1, [1; 32].into()));
-		let block1_c = insert_block(&db, None, || header_with_extrinsics_root(&block0, 1, [2; 32].into()));
+		let block1_a = insert_block(&db, HashMap::new(), || default_header(&block0, 1));
+		let block1_b = insert_block(&db, HashMap::new(), || header_with_extrinsics_root(&block0, 1, [1; 32].into()));
+		let block1_c = insert_block(&db, HashMap::new(), || header_with_extrinsics_root(&block0, 1, [2; 32].into()));

 		assert_eq!(db.leaves.read().hashes(), vec![block1_a, block1_b, block1_c]);

-		let block2_a = insert_block(&db, None, || default_header(&block1_a, 2));
-		let block2_b = insert_block(&db, None, || header_with_extrinsics_root(&block1_b, 2, [1; 32].into()));
-		let block2_c = insert_block(&db, None, || header_with_extrinsics_root(&block1_b, 2, [2; 32].into()));
+		let block2_a = insert_block(&db, HashMap::new(), || default_header(&block1_a, 2));
+		let block2_b = insert_block(&db, HashMap::new(), || header_with_extrinsics_root(&block1_b, 2, [1; 32].into()));
+		let block2_c = insert_block(&db, HashMap::new(), || header_with_extrinsics_root(&block1_b, 2, [2; 32].into()));

 		assert_eq!(db.leaves.read().hashes(), vec![block2_a, block2_b, block2_c, block1_c]);

@@ -16,10 +16,11 @@

 //! Substrate Client data backend

+use std::collections::HashMap;
 use crate::error;
 use primitives::ChangesTrieConfiguration;
 use runtime_primitives::{generic::BlockId, Justification, StorageOverlay, ChildrenStorageOverlay};
-use runtime_primitives::traits::{AuthorityIdFor, Block as BlockT, NumberFor};
+use runtime_primitives::traits::{Block as BlockT, NumberFor};
 use state_machine::backend::Backend as StateBackend;
 use state_machine::ChangesTrieStorage as StateChangesTrieStorage;
 use hash_db::Hasher;
@@ -73,9 +74,8 @@ pub trait BlockImportOperation<Block, H> where
 		state: NewBlockState,
 	) -> error::Result<()>;

-	/// Append authorities set to the transaction. This is a set of parent block (set which
-	/// has been used to check justification of this block).
-	fn update_authorities(&mut self, authorities: Vec<AuthorityIdFor<Block>>);
+	/// Update cached data.
+	fn update_cache(&mut self, cache: HashMap<Vec<u8>, Vec<u8>>);
 	/// Inject storage data into the database.
 	fn update_db_storage(&mut self, update: <Self::State as StateBackend<H>>::Transaction) -> error::Result<()>;
 	/// Inject storage data into the database replacing any existing data.
@@ -16,7 +16,9 @@

 //! Substrate blockchain trait

-use runtime_primitives::traits::{AuthorityIdFor, Block as BlockT, Header as HeaderT, NumberFor};
+use std::sync::Arc;
+
+use runtime_primitives::traits::{Block as BlockT, Header as HeaderT, NumberFor};
 use runtime_primitives::generic::BlockId;
 use runtime_primitives::Justification;

@@ -78,7 +80,7 @@ pub trait Backend<Block: BlockT>: HeaderBackend<Block> {
 	/// Get last finalized block hash.
 	fn last_finalized(&self) -> Result<Block::Hash>;
 	/// Returns data cache reference, if it is enabled on this backend.
-	fn cache(&self) -> Option<&Cache<Block>>;
+	fn cache(&self) -> Option<Arc<Cache<Block>>>;

 	/// Returns hashes of all blocks that are leaves of the block tree.
 	/// in other words, that have no children, are chain heads.
@@ -89,10 +91,16 @@ pub trait Backend<Block: BlockT>: HeaderBackend<Block> {
 	fn children(&self, parent_hash: Block::Hash) -> Result<Vec<Block::Hash>>;
 }

+/// Provides access to the optional cache.
+pub trait ProvideCache<Block: BlockT> {
+	/// Returns data cache reference, if it is enabled on this backend.
+	fn cache(&self) -> Option<Arc<Cache<Block>>>;
+}
+
 /// Blockchain optional data cache.
 pub trait Cache<Block: BlockT>: Send + Sync {
-	/// Returns the set of authorities, that was active at given block or None if there's no entry in the cache.
-	fn authorities_at(&self, block: BlockId<Block>) -> Option<Vec<AuthorityIdFor<Block>>>;
+	/// Returns cached value by the given key.
+	fn get_at(&self, key: &[u8], block: &BlockId<Block>) -> Option<Vec<u8>>;
 }

 /// Blockchain info
@@ -16,7 +16,7 @@

 //! Substrate Client

-use std::{marker::PhantomData, collections::{HashSet, BTreeMap}, sync::Arc, panic::UnwindSafe, result};
+use std::{marker::PhantomData, collections::{HashSet, BTreeMap, HashMap}, sync::Arc, panic::UnwindSafe, result};
 use crate::error::Error;
 use futures::sync::mpsc;
 use parking_lot::{Mutex, RwLock};
@@ -31,7 +31,7 @@ use consensus::{
 };
 use runtime_primitives::traits::{
 	Block as BlockT, Header as HeaderT, Zero, As, NumberFor, CurrentHeight, BlockNumberToHash,
-	ApiRef, ProvideRuntimeApi, Digest, DigestItem, AuthorityIdFor
+	ApiRef, ProvideRuntimeApi, Digest, DigestItem
 };
 use runtime_primitives::BuildStorage;
 use crate::runtime_api::{CallRuntimeAt, ConstructRuntimeApi};
@@ -49,7 +49,8 @@ use hash_db::Hasher;

 use crate::backend::{self, BlockImportOperation, PrunableStateChangesTrieStorage};
 use crate::blockchain::{
-	self, Info as ChainInfo, Backend as ChainBackend, HeaderBackend as ChainHeaderBackend
+	self, Info as ChainInfo, Backend as ChainBackend, HeaderBackend as ChainHeaderBackend,
+	ProvideCache, Cache,
 };
 use crate::call_executor::{CallExecutor, LocalCallExecutor};
 use executor::{RuntimeVersion, RuntimeInfo};
@@ -342,16 +343,6 @@ impl<B, E, Block, RA> Client<B, E, Block, RA> where
 			.expect("None is returned if there's no value stored for the given key; ':code' key is always defined; qed").0)
 	}

-	/// Get the set of authorities at a given block.
-	pub fn authorities_at(&self, id: &BlockId<Block>) -> error::Result<Vec<AuthorityIdFor<Block>>> {
-		match self.backend.blockchain().cache().and_then(|cache| cache.authorities_at(*id)) {
-			Some(cached_value) => Ok(cached_value),
-			None => self.executor.call(id, "Core_authorities", &[], ExecutionStrategy::NativeElseWasm, NeverOffchainExt::new())
-				.and_then(|r| Vec::<AuthorityIdFor<Block>>::decode(&mut &r[..])
-					.ok_or_else(|| error::ErrorKind::InvalidAuthoritiesSet.into()))
-		}
-	}
-
 	/// Get the RuntimeVersion at a given block.
 	pub fn runtime_version_at(&self, id: &BlockId<Block>) -> error::Result<RuntimeVersion> {
 		self.executor.runtime_version(id)
@@ -681,7 +672,7 @@ impl<B, E, Block, RA> Client<B, E, Block, RA> where
 		&self,
 		operation: &mut ClientImportOperation<Block, Blake2Hasher, B>,
 		import_block: ImportBlock<Block>,
-		new_authorities: Option<Vec<AuthorityIdFor<Block>>>,
+		new_cache: HashMap<Vec<u8>, Vec<u8>>,
 	) -> error::Result<ImportResult> where
 		E: CallExecutor<Block, Blake2Hasher> + Send + Sync + Clone,
 	{
@@ -729,7 +720,7 @@ impl<B, E, Block, RA> Client<B, E, Block, RA> where
 			import_headers,
 			justification,
 			body,
-			new_authorities,
+			new_cache,
 			finalized,
 			auxiliary,
 			fork_choice,
@@ -752,7 +743,7 @@ impl<B, E, Block, RA> Client<B, E, Block, RA> where
 		import_headers: PrePostHeader<Block::Header>,
 		justification: Option<Justification>,
 		body: Option<Vec<Block::Extrinsic>>,
-		authorities: Option<Vec<AuthorityIdFor<Block>>>,
+		new_cache: HashMap<Vec<u8>, Vec<u8>>,
 		finalized: bool,
 		aux: Vec<(Vec<u8>, Option<Vec<u8>>)>,
 		fork_choice: ForkChoiceStrategy,
@@ -810,9 +801,7 @@ impl<B, E, Block, RA> Client<B, E, Block, RA> where
 			leaf_state,
 		)?;

-		if let Some(authorities) = authorities {
-			operation.op.update_authorities(authorities);
-		}
+		operation.op.update_cache(new_cache);
 		if let Some(storage_update) = storage_update {
 			operation.op.update_db_storage(storage_update)?;
 		}
@@ -1324,6 +1313,15 @@ impl<B, E, Block, RA> ChainHeaderBackend<Block> for Client<B, E, Block, RA> wher
 	}
 }

+impl<B, E, Block, RA> ProvideCache<Block> for Client<B, E, Block, RA> where
+	B: backend::Backend<Block, Blake2Hasher>,
+	Block: BlockT<Hash=H256>,
+{
+	fn cache(&self) -> Option<Arc<Cache<Block>>> {
+		self.backend.blockchain().cache()
+	}
+}
+
 impl<B, E, Block, RA> ProvideRuntimeApi for Client<B, E, Block, RA> where
 	B: backend::Backend<Block, Blake2Hasher>,
 	E: CallExecutor<Block, Blake2Hasher> + Clone + Send + Sync,
@@ -1398,10 +1396,10 @@ impl<B, E, Block, RA> consensus::BlockImport<Block> for Client<B, E, Block, RA>
 	fn import_block(
 		&self,
 		import_block: ImportBlock<Block>,
-		new_authorities: Option<Vec<AuthorityIdFor<Block>>>,
+		new_cache: HashMap<Vec<u8>, Vec<u8>>,
 	) -> Result<ImportResult, Self::Error> {
 		self.lock_import_and_run(|operation| {
-			self.apply_block(operation, import_block, new_authorities)
+			self.apply_block(operation, import_block, new_cache)
 		}).map_err(|e| ConsensusErrorKind::ClientImport(e.to_string()).into())
 	}

@@ -1431,17 +1429,6 @@ impl<B, E, Block, RA> consensus::BlockImport<Block> for Client<B, E, Block, RA>
 	}
 }

-impl<B, E, Block, RA> consensus::Authorities<Block> for Client<B, E, Block, RA> where
-	B: backend::Backend<Block, Blake2Hasher>,
-	E: CallExecutor<Block, Blake2Hasher> + Clone,
-	Block: BlockT<Hash=H256>,
-{
-	type Error = Error;
-	fn authorities(&self, at: &BlockId<Block>) -> Result<Vec<AuthorityIdFor<Block>>, Self::Error> {
-		self.authorities_at(at).map_err(|e| e.into())
-	}
-}
-
 impl<B, E, Block, RA> CurrentHeight for Client<B, E, Block, RA> where
 	B: backend::Backend<Block, Blake2Hasher>,
 	E: CallExecutor<Block, Blake2Hasher>,
@@ -1550,7 +1537,7 @@ pub(crate) mod tests {
 	use primitives::twox_128;
 	use runtime_primitives::traits::DigestItem as DigestItemT;
 	use runtime_primitives::generic::DigestItem;
-	use test_client::{self, TestClient, AccountKeyring, AuthorityKeyring};
+	use test_client::{self, TestClient, AccountKeyring};
 	use consensus::BlockOrigin;
 	use test_client::client::backend::Backend as TestBackend;
 	use test_client::BlockBuilderExt;
@@ -1649,18 +1636,6 @@ pub(crate) mod tests {
 		);
 	}

-	#[test]
-	fn authorities_call_works() {
-		let client = test_client::new();
-
-		assert_eq!(client.info().unwrap().chain.best_number, 0);
-		assert_eq!(client.authorities_at(&BlockId::Number(0)).unwrap(), vec![
-			AuthorityKeyring::Alice.into(),
-			AuthorityKeyring::Bob.into(),
-			AuthorityKeyring::Charlie.into()
-		]);
-	}
-
 	#[test]
 	fn block_builder_works_with_no_transactions() {
 		let client = test_client::new();
@@ -1705,15 +1680,6 @@ pub(crate) mod tests {
 		);
 	}

-	#[test]
-	fn client_uses_authorities_from_blockchain_cache() {
-		let client = test_client::new_light();
-		let genesis_hash = client.header(&BlockId::Number(0)).unwrap().unwrap().hash();
-		// authorities cache is first filled in genesis block
-		// => should be read from cache here (remote request will fail in this test)
-		assert!(!client.authorities_at(&BlockId::Hash(genesis_hash)).unwrap().is_empty());
-	}
-
 	#[test]
 	fn block_builder_does_not_include_invalid() {
 		let client = test_client::new();
@@ -62,12 +62,6 @@ error_chain! {
 			display("Blockchain: {}", e),
 		}

-		/// Invalid authorities set received from the runtime.
-		InvalidAuthoritiesSet {
-			description("authorities set is invalid"),
-			display("Current state of blockchain has invalid authorities set"),
-		}
-
 		/// Could not get runtime version.
 		VersionInvalid {
 			description("Runtime version error"),
@@ -22,7 +22,7 @@ use parking_lot::RwLock;
 use primitives::{ChangesTrieConfiguration, storage::well_known_keys};
 use runtime_primitives::generic::BlockId;
 use runtime_primitives::traits::{Block as BlockT, Header as HeaderT, Zero,
-	NumberFor, As, Digest, DigestItem, AuthorityIdFor};
+	NumberFor, As, Digest, DigestItem};
 use runtime_primitives::{Justification, StorageOverlay, ChildrenStorageOverlay};
 use state_machine::backend::{Backend as StateBackend, InMemory, Consolidate};
 use state_machine::{self, InMemoryChangesTrieStorage, ChangesTrieAnchorBlockId};
@@ -104,12 +104,6 @@ struct BlockchainStorage<Block: BlockT> {
 /// In-memory blockchain. Supports concurrent reads.
 pub struct Blockchain<Block: BlockT> {
 	storage: Arc<RwLock<BlockchainStorage<Block>>>,
-	cache: Cache<Block>,
-}
-
-struct Cache<Block: BlockT> {
-	storage: Arc<RwLock<BlockchainStorage<Block>>>,
-	authorities_at: RwLock<HashMap<Block::Hash, Option<Vec<AuthorityIdFor<Block>>>>>,
 }

 impl<Block: BlockT + Clone> Clone for Blockchain<Block> {
@@ -117,10 +111,6 @@ impl<Block: BlockT + Clone> Clone for Blockchain<Block> {
 		let storage = Arc::new(RwLock::new(self.storage.read().clone()));
 		Blockchain {
 			storage: storage.clone(),
-			cache: Cache {
-				storage,
-				authorities_at: RwLock::new(self.cache.authorities_at.read().clone()),
-			},
 		}
 	}
 }
@@ -152,10 +142,6 @@ impl<Block: BlockT> Blockchain<Block> {
 			}));
 		Blockchain {
 			storage: storage.clone(),
-			cache: Cache {
-				storage: storage,
-				authorities_at: Default::default(),
-			},
 		}
 	}

@@ -355,8 +341,8 @@ impl<Block: BlockT> blockchain::Backend<Block> for Blockchain<Block> {
 		Ok(self.storage.read().finalized_hash.clone())
 	}

-	fn cache(&self) -> Option<&blockchain::Cache<Block>> {
-		Some(&self.cache)
+	fn cache(&self) -> Option<Arc<blockchain::Cache<Block>>> {
+		None
 	}

 	fn leaves(&self) -> error::Result<Vec<Block::Hash>> {
@@ -368,6 +354,12 @@ impl<Block: BlockT> blockchain::Backend<Block> for Blockchain<Block> {
 	}
 }

+impl<Block: BlockT> blockchain::ProvideCache<Block> for Blockchain<Block> {
+	fn cache(&self) -> Option<Arc<blockchain::Cache<Block>>> {
+		None
+	}
+}
+
 impl<Block: BlockT> backend::AuxStore for Blockchain<Block> {
 	fn insert_aux<
 		'a,
@@ -398,16 +390,12 @@ impl<Block: BlockT> light::blockchain::Storage<Block> for Blockchain<Block>
 	fn import_header(
 		&self,
 		header: Block::Header,
-		authorities: Option<Vec<AuthorityIdFor<Block>>>,
+		_cache: HashMap<Vec<u8>, Vec<u8>>,
 		state: NewBlockState,
 		aux_ops: Vec<(Vec<u8>, Option<Vec<u8>>)>,
 	) -> error::Result<()> {
 		let hash = header.hash();
-		let parent_hash = *header.parent_hash();
 		self.insert(hash, header, None, None, state)?;
-		if state.is_best() {
-			self.cache.insert(parent_hash, authorities);
-		}

 		self.write_aux(aux_ops);
 		Ok(())
@@ -435,15 +423,15 @@ impl<Block: BlockT> light::blockchain::Storage<Block> for Blockchain<Block>
 			.ok_or_else(|| error::ErrorKind::Backend(format!("Changes trie CHT for block {} not exists", block)).into())
 	}

-	fn cache(&self) -> Option<&blockchain::Cache<Block>> {
-		Some(&self.cache)
+	fn cache(&self) -> Option<Arc<blockchain::Cache<Block>>> {
+		None
 	}
 }

 /// In-memory operation.
 pub struct BlockImportOperation<Block: BlockT, H: Hasher> {
 	pending_block: Option<PendingBlock<Block>>,
-	pending_authorities: Option<Vec<AuthorityIdFor<Block>>>,
+	pending_cache: HashMap<Vec<u8>, Vec<u8>>,
 	old_state: InMemory<H>,
 	new_state: Option<InMemory<H>>,
 	changes_trie_update: Option<MemoryDB<H>>,
@@ -480,8 +468,8 @@ where
 		Ok(())
 	}

-	fn update_authorities(&mut self, authorities: Vec<AuthorityIdFor<Block>>) {
-		self.pending_authorities = Some(authorities);
+	fn update_cache(&mut self, cache: HashMap<Vec<u8>, Vec<u8>>) {
+		self.pending_cache = cache;
 	}

 	fn update_db_storage(&mut self, update: <InMemory<H> as StateBackend<H>>::Transaction) -> error::Result<()> {
@@ -602,7 +590,7 @@ where
 		let old_state = self.state_at(BlockId::Hash(Default::default()))?;
 		Ok(BlockImportOperation {
 			pending_block: None,
-			pending_authorities: None,
+			pending_cache: Default::default(),
 			old_state,
 			new_state: None,
 			changes_trie_update: None,
@@ -629,7 +617,6 @@ where
 			let (header, body, justification) = pending_block.block.into_inner();

 			let hash = header.hash();
-			let parent_hash = *header.parent_hash();

 			self.states.write().insert(hash, operation.new_state.unwrap_or_else(|| old_state.clone()));

@@ -642,10 +629,6 @@ where
 			}

 			self.blockchain.insert(hash, header, justification, body, pending_block.state)?;
-			// dumb implementation - store value for each block
-			if pending_block.state.is_best() {
-				self.blockchain.cache.insert(parent_hash, operation.pending_authorities);
-			}
 		}

 		if !operation.aux.is_empty() {
@@ -710,23 +693,6 @@ where
 	}
 }

-impl<Block: BlockT> Cache<Block> {
-	fn insert(&self, at: Block::Hash, authorities: Option<Vec<AuthorityIdFor<Block>>>) {
-		self.authorities_at.write().insert(at, authorities);
-	}
-}
-
-impl<Block: BlockT> blockchain::Cache<Block> for Cache<Block> {
-	fn authorities_at(&self, block: BlockId<Block>) -> Option<Vec<AuthorityIdFor<Block>>> {
-		let hash = match block {
-			BlockId::Hash(hash) => hash,
-			BlockId::Number(number) => self.storage.read().hashes.get(&number).cloned()?,
-		};
-
-		self.authorities_at.read().get(&hash).cloned().unwrap_or(None)
-	}
-}
-
 /// Prunable in-memory changes trie storage.
 pub struct ChangesTrieStorage<H: Hasher>(InMemoryChangesTrieStorage<H>) where H::Out: HeapSizeOf;
 impl<H: Hasher> backend::PrunableStateChangesTrieStorage<H> for ChangesTrieStorage<H> where H::Out: HeapSizeOf {
@@ -747,15 +713,6 @@ impl<H: Hasher> state_machine::ChangesTrieStorage<H> for ChangesTrieStorage<H> w
 	}
 }

-/// Insert authorities entry into in-memory blockchain cache. Extracted as a separate function to use it in tests.
-pub fn cache_authorities_at<Block: BlockT>(
-	blockchain: &Blockchain<Block>,
-	at: Block::Hash,
-	authorities: Option<Vec<AuthorityIdFor<Block>>>
-) {
-	blockchain.cache.insert(at, authorities);
-}
-
 /// Check that genesis storage is valid.
 pub fn check_genesis_storage(top: &StorageOverlay, children: &ChildrenStorageOverlay) -> error::Result<()> {
 	if top.iter().any(|(k, _)| well_known_keys::is_child_storage_key(k)) {
@@ -24,7 +24,7 @@ use parking_lot::RwLock;

 use runtime_primitives::{generic::BlockId, Justification, StorageOverlay, ChildrenStorageOverlay};
 use state_machine::{Backend as StateBackend, TrieBackend, backend::InMemory as InMemoryState};
-use runtime_primitives::traits::{Block as BlockT, NumberFor, AuthorityIdFor, Zero, Header};
+use runtime_primitives::traits::{Block as BlockT, NumberFor, Zero, Header};
 use crate::in_mem::{self, check_genesis_storage};
 use crate::backend::{AuxStore, Backend as ClientBackend, BlockImportOperation, RemoteBackend, NewBlockState};
 use crate::blockchain::HeaderBackend as BlockchainHeaderBackend;
@@ -46,7 +46,7 @@ pub struct Backend<S, F, H> {
 /// Light block (header and justification) import operation.
 pub struct ImportOperation<Block: BlockT, S, F, H> {
 	header: Option<Block::Header>,
-	authorities: Option<Vec<AuthorityIdFor<Block>>>,
+	cache: HashMap<Vec<u8>, Vec<u8>>,
 	leaf_state: NewBlockState,
 	aux_ops: Vec<(Vec<u8>, Option<Vec<u8>>)>,
 	finalized_blocks: Vec<BlockId<Block>>,
@@ -117,7 +117,7 @@ impl<S, F, Block, H> ClientBackend<Block, H> for Backend<S, F, H> where
 	fn begin_operation(&self) -> ClientResult<Self::BlockImportOperation> {
 		Ok(ImportOperation {
 			header: None,
-			authorities: None,
+			cache: Default::default(),
 			leaf_state: NewBlockState::Normal,
 			aux_ops: Vec::new(),
 			finalized_blocks: Vec::new(),
@@ -146,7 +146,7 @@ impl<S, F, Block, H> ClientBackend<Block, H> for Backend<S, F, H> where
 			let is_genesis_import = header.number().is_zero();
 			self.blockchain.storage().import_header(
 				header,
-				operation.authorities,
+				operation.cache,
 				operation.leaf_state,
 				operation.aux_ops,
 			)?;
@@ -254,8 +254,8 @@ where
 		Ok(())
 	}

-	fn update_authorities(&mut self, authorities: Vec<AuthorityIdFor<Block>>) {
-		self.authorities = Some(authorities);
+	fn update_cache(&mut self, cache: HashMap<Vec<u8>, Vec<u8>>) {
+		self.cache = cache;
 	}

 	fn update_db_storage(&mut self, _update: <Self::State as StateBackend<H>>::Transaction) -> ClientResult<()> {
@@ -17,16 +17,16 @@
 //! Light client blockchin backend. Only stores headers and justifications of recent
 //! blocks. CHT roots are stored for headers of ancient blocks.

-use std::sync::Weak;
+use std::{sync::{Weak, Arc}, collections::HashMap};
 use futures::{Future, IntoFuture};
 use parking_lot::Mutex;

 use runtime_primitives::{Justification, generic::BlockId};
-use runtime_primitives::traits::{Block as BlockT, Header as HeaderT, NumberFor, Zero, AuthorityIdFor};
+use runtime_primitives::traits::{Block as BlockT, Header as HeaderT, NumberFor, Zero};

 use crate::backend::{AuxStore, NewBlockState};
 use crate::blockchain::{Backend as BlockchainBackend, BlockStatus, Cache as BlockchainCache,
-	HeaderBackend as BlockchainHeaderBackend, Info as BlockchainInfo};
+	HeaderBackend as BlockchainHeaderBackend, Info as BlockchainInfo, ProvideCache};
 use crate::cht;
 use crate::error::{ErrorKind as ClientErrorKind, Result as ClientResult};
 use crate::light::fetcher::{Fetcher, RemoteHeaderRequest};
@@ -40,7 +40,7 @@ pub trait Storage<Block: BlockT>: AuxStore + BlockchainHeaderBackend<Block> {
 	fn import_header(
 		&self,
 		header: Block::Header,
-		authorities: Option<Vec<AuthorityIdFor<Block>>>,
+		cache: HashMap<Vec<u8>, Vec<u8>>,
 		state: NewBlockState,
 		aux_ops: Vec<(Vec<u8>, Option<Vec<u8>>)>,
 	) -> ClientResult<()>;
@@ -61,7 +61,7 @@ pub trait Storage<Block: BlockT>: AuxStore + BlockchainHeaderBackend<Block> {
 	fn changes_trie_cht_root(&self, cht_size: u64, block: NumberFor<Block>) -> ClientResult<Block::Hash>;

 	/// Get storage cache.
-	fn cache(&self) -> Option<&BlockchainCache<Block>>;
+	fn cache(&self) -> Option<Arc<BlockchainCache<Block>>>;
 }

 /// Light client blockchain.
@@ -156,7 +156,7 @@ impl<S, F, Block> BlockchainBackend<Block> for Blockchain<S, F> where Block: Blo
 		self.storage.last_finalized()
 	}

-	fn cache(&self) -> Option<&BlockchainCache<Block>> {
+	fn cache(&self) -> Option<Arc<BlockchainCache<Block>>> {
 		self.storage.cache()
 	}

@@ -169,6 +169,12 @@ impl<S, F, Block> BlockchainBackend<Block> for Blockchain<S, F> where Block: Blo
 	}
 }

+impl<S: Storage<Block>, F, Block: BlockT> ProvideCache<Block> for Blockchain<S, F> {
+	fn cache(&self) -> Option<Arc<BlockchainCache<Block>>> {
+		self.storage.cache()
+	}
+}
+
 #[cfg(test)]
 pub mod tests {
 	use std::collections::HashMap;
@@ -246,7 +252,7 @@ pub mod tests {
 		fn import_header(
 			&self,
 			_header: Header,
-			_authorities: Option<Vec<AuthorityIdFor<Block>>>,
+			_cache: HashMap<Vec<u8>, Vec<u8>>,
 			_state: NewBlockState,
 			_aux_ops: Vec<(Vec<u8>, Option<Vec<u8>>)>,
 		) -> ClientResult<()> {
@@ -278,7 +284,7 @@ pub mod tests {
 				).into())
 		}

-		fn cache(&self) -> Option<&BlockchainCache<Block>> {
+		fn cache(&self) -> Option<Arc<BlockchainCache<Block>>> {
 			None
 		}
 	}
@@ -512,7 +512,7 @@ mod tests {
 		}

 		// check method that doesn't requires environment
-		let (remote, local) = execute(&remote_client, 0, "Core_authorities");
+		let (remote, local) = execute(&remote_client, 0, "Core_version");
 		assert_eq!(remote, local);

 		// check method that requires environment
@@ -390,6 +390,7 @@ impl<'a, H, Number, Hash> ChangesTrieRootsStorage<H> for RootsStorage<'a, Number
 pub mod tests {
 	use futures::future::{ok, err, FutureResult};
 	use parking_lot::Mutex;
+	use parity_codec::Decode;
 	use crate::client::tests::prepare_client_with_key_changes;
 	use executor::{self, NativeExecutionDispatch};
 	use crate::error::Error as ClientError;
@@ -436,7 +437,7 @@ pub mod tests {

 	type TestChecker = LightDataChecker<executor::NativeExecutor<test_client::LocalExecutor>, Blake2Hasher, Block, DummyStorage, OkCallFetcher>;

-	fn prepare_for_read_proof_check() -> (TestChecker, Header, Vec<Vec<u8>>, usize) {
+	fn prepare_for_read_proof_check() -> (TestChecker, Header, Vec<Vec<u8>>, u32) {
 		// prepare remote client
 		let remote_client = test_client::new();
 		let remote_block_id = BlockId::Number(0);
@@ -445,7 +446,9 @@ pub mod tests {
 		remote_block_header.state_root = remote_client.state_at(&remote_block_id).unwrap().storage_root(::std::iter::empty()).0.into();

 		// 'fetch' read proof from remote node
-		let authorities_len = remote_client.authorities_at(&remote_block_id).unwrap().len();
+		let authorities_len = remote_client.storage(&remote_block_id, &StorageKey(well_known_keys::AUTHORITY_COUNT.to_vec()))
+			.unwrap()
+			.and_then(|v| Decode::decode(&mut &v.0[..])).unwrap();
 		let remote_read_proof = remote_client.read_proof(&remote_block_id, well_known_keys::AUTHORITY_COUNT).unwrap();

 		// check remote read proof locally
@@ -38,7 +38,6 @@ use rstd::result;
 pub use parity_codec::{Encode, Decode};
 #[cfg(feature = "std")]
 use crate::error;
-use rstd::vec::Vec;
 use sr_api_macros::decl_runtime_apis;
 use primitives::OpaqueMetadata;
 #[cfg(feature = "std")]
@@ -112,13 +111,11 @@ pub trait CallRuntimeAt<Block: BlockT> {
 }

 decl_runtime_apis! {
-	/// The `Core` api trait that is mandantory for each runtime.
+	/// The `Core` api trait that is mandatory for each runtime.
 	#[core_trait]
 	pub trait Core {
 		/// Returns the version of the runtime.
 		fn version() -> RuntimeVersion;
-		/// Returns the authorities.
-		fn authorities() -> Vec<AuthorityIdFor<Block>>;
 		/// Execute the given block.
 		fn execute_block(block: Block);
 		/// Initialize a block with the given header.
@@ -25,6 +25,7 @@ parking_lot = "0.7.1"
 error-chain = "0.12"
 log = "0.4"
 consensus_common = { package = "substrate-consensus-common", path = "../common" }
+authorities = { package = "substrate-consensus-authorities", path = "../authorities" }

 [dev-dependencies]
 keyring = { package = "substrate-keyring", path = "../../keyring" }
@@ -29,21 +29,23 @@
 use std::{sync::Arc, time::Duration, thread, marker::PhantomData, hash::Hash, fmt::Debug};

 use parity_codec::{Encode, Decode};
-use consensus_common::{
-	Authorities, BlockImport, Environment, Proposer, ForkChoiceStrategy
+use consensus_common::{self, Authorities, BlockImport, Environment, Proposer,
+	ForkChoiceStrategy, ImportBlock, BlockOrigin, Error as ConsensusError,
 };
+use consensus_common::well_known_cache_keys;
 use consensus_common::import_queue::{Verifier, BasicQueue, SharedBlockImport, SharedJustificationImport};
 use client::ChainHead;
 use client::block_builder::api::BlockBuilder as BlockBuilderApi;
+use client::blockchain::ProvideCache;
 use client::runtime_api::ApiExt;
-use consensus_common::{ImportBlock, BlockOrigin};
 use aura_primitives::AURA_ENGINE_ID;
 use runtime_primitives::{generic, generic::BlockId, Justification};
 use runtime_primitives::traits::{
-	Block, Header, Digest, DigestItemFor, DigestItem, ProvideRuntimeApi
+	Block, Header, Digest, DigestItemFor, DigestItem, ProvideRuntimeApi, AuthorityIdFor,
 };
 use primitives::Pair;
 use inherents::{InherentDataProviders, InherentData, RuntimeString};
+use authorities::AuthoritiesApi;

 use futures::{Stream, Future, IntoFuture, future};
 use tokio::timer::Timeout;
@@ -179,12 +181,13 @@ pub fn start_aura_thread<B, C, E, I, P, SO, Error, OnExit>(
 	force_authoring: bool,
 ) -> Result<(), consensus_common::Error> where
 	B: Block + 'static,
-	C: Authorities<B> + ChainHead<B> + Send + Sync + 'static,
+	C: ChainHead<B> + ProvideRuntimeApi + ProvideCache<B> + Send + Sync + 'static,
+	C::Api: AuthoritiesApi<B>,
 	E: Environment<B, Error=Error> + Send + Sync + 'static,
 	E::Proposer: Proposer<B, Error=Error> + Send + 'static,
 	<<E::Proposer as Proposer<B>>::Create as IntoFuture>::Future: Send + 'static,
 	I: BlockImport<B> + Send + Sync + 'static,
-	Error: From<C::Error> + From<I::Error> + 'static,
+	Error: From<I::Error> + 'static,
 	P: Pair + Send + Sync + 'static,
 	P::Public: Encode + Decode + Eq + Clone + Debug + Hash + Send + Sync + 'static,
 	P::Signature: Encode,
@@ -226,12 +229,13 @@ pub fn start_aura<B, C, E, I, P, SO, Error, OnExit>(
 	force_authoring: bool,
 ) -> Result<impl Future<Item=(), Error=()>, consensus_common::Error> where
 	B: Block,
-	C: Authorities<B> + ChainHead<B>,
+	C: ChainHead<B> + ProvideRuntimeApi + ProvideCache<B>,
+	C::Api: AuthoritiesApi<B>,
 	E: Environment<B, Error=Error>,
 	E::Proposer: Proposer<B, Error=Error>,
 	<<E::Proposer as Proposer<B>>::Create as IntoFuture>::Future: Send + 'static,
 	I: BlockImport<B> + Send + Sync + 'static,
-	Error: From<C::Error> + From<I::Error>,
+	Error: From<I::Error>,
 	P: Pair + Send + Sync + 'static,
 	P::Public: Hash + Eq + Send + Sync + Clone + Debug + Encode + Decode + 'static,
 	P::Signature: Encode,
@@ -270,7 +274,8 @@ struct AuraWorker<C, E, I, P, SO> {
 }

 impl<B: Block, C, E, I, P, Error, SO> SlotWorker<B> for AuraWorker<C, E, I, P, SO> where
-	C: Authorities<B>,
+	C: ProvideRuntimeApi + ProvideCache<B>,
+	C::Api: AuthoritiesApi<B>,
 	E: Environment<B, Error=Error>,
 	E::Proposer: Proposer<B, Error=Error>,
 	<<E::Proposer as Proposer<B>>::Create as IntoFuture>::Future: Send + 'static,
@@ -278,7 +283,7 @@ impl<B: Block, C, E, I, P, Error, SO> SlotWorker<B> for AuraWorker<C, E, I, P, S
 	P: Pair + Send + Sync + 'static,
 	P::Public: Hash + Eq + Send + Sync + Clone + Debug + Encode + Decode + 'static,
 	P::Signature: Encode,
-	Error: From<C::Error> + From<I::Error>,
+	Error: From<I::Error>,
 	SO: SyncOracle + Send + Clone,
 	DigestItemFor<B>: CompatibleDigestItem<P> + DigestItem<AuthorityId=AuthorityId<P>>,
 	Error: ::std::error::Error + Send + 'static + From<::consensus_common::Error>,
@@ -306,7 +311,7 @@ impl<B: Block, C, E, I, P, Error, SO> SlotWorker<B> for AuraWorker<C, E, I, P, S
 		let (timestamp, slot_num, slot_duration) =
 			(slot_info.timestamp, slot_info.number, slot_info.duration);

-		let authorities = match client.authorities(&BlockId::Hash(chain_head.hash())) {
+		let authorities = match authorities(client.as_ref(), &BlockId::Hash(chain_head.hash())) {
 			Ok(authorities) => authorities,
 			Err(e) => {
 				warn!(
@@ -418,7 +423,7 @@ impl<B: Block, C, E, I, P, Error, SO> SlotWorker<B> for AuraWorker<C, E, I, P, S
 						"hash_previously" => ?pre_hash
 					);

-					if let Err(e) = block_import.import_block(import_block, None) {
+					if let Err(e) = block_import.import_block(import_block, Default::default()) {
 						warn!(target: "aura", "Error with block built on {:?}: {:?}",
 							  parent_hash, e);
 						telemetry!(CONSENSUS_WARN; "aura.err_with_block_built_on";
@@ -573,13 +578,14 @@ impl<B: Block> ExtraVerification<B> for NothingExtra {

 #[forbid(deprecated)]
 impl<B: Block, C, E, P> Verifier<B> for AuraVerifier<C, E, P> where
-	C: Authorities<B> + ProvideRuntimeApi + Send + Sync,
+	C: ProvideRuntimeApi + Send + Sync,
 	C::Api: BlockBuilderApi<B>,
 	DigestItemFor<B>: CompatibleDigestItem<P> + DigestItem<AuthorityId=AuthorityId<P>>,
 	E: ExtraVerification<B>,
 	P: Pair + Send + Sync + 'static,
 	P::Public: Send + Sync + Hash + Eq + Clone + Decode + Encode + Debug + AsRef<P::Public> + 'static,
 	P::Signature: Encode + Decode,
+	Self: Authorities<B>,
 {
 	fn verify(
 		&self,
@@ -593,7 +599,7 @@ impl<B: Block, C, E, P> Verifier<B> for AuraVerifier<C, E, P> where
 			.map_err(|e| format!("Could not extract timestamp and slot: {:?}", e))?;
 		let hash = header.hash();
 		let parent_hash = *header.parent_hash();
-		let authorities = self.client.authorities(&BlockId::Hash(parent_hash))
+		let authorities = self.authorities(&BlockId::Hash(parent_hash))
 			.map_err(|e| format!("Could not fetch authorities at {:?}: {:?}", parent_hash, e))?;

 		let extra_verification = self.extra.verify(
@@ -669,6 +675,31 @@ impl<B: Block, C, E, P> Verifier<B> for AuraVerifier<C, E, P> where
 	}
 }

+impl<B, C, E, P> Authorities<B> for AuraVerifier<C, E, P> where
+	B: Block,
+	C: ProvideRuntimeApi + ProvideCache<B>,
+	C::Api: AuthoritiesApi<B>,
+{
+	type Error = ConsensusError;
+
+	fn authorities(&self, at: &BlockId<B>) -> Result<Vec<AuthorityIdFor<B>>, Self::Error> {
+		authorities(self.client.as_ref(), at)
+	}
+}
+
+fn authorities<B, C>(client: &C, at: &BlockId<B>) -> Result<Vec<AuthorityIdFor<B>>, ConsensusError> where
+	B: Block,
+	C: ProvideRuntimeApi + ProvideCache<B>,
+	C::Api: AuthoritiesApi<B>,
+{
+	client
+		.cache()
+		.and_then(|cache| cache.get_at(well_known_cache_keys::AUTHORITIES, at)
+			.and_then(|v| Decode::decode(&mut &v[..])))
+		.or_else(|| client.runtime_api().authorities(at).ok())
+		.ok_or_else(|| consensus_common::ErrorKind::InvalidAuthoritiesSet.into())
+}
+
 /// The Aura import queue type.
 pub type AuraImportQueue<B> = BasicQueue<B>;

@@ -697,8 +728,8 @@ pub fn import_queue<B, C, E, P>(
 	allow_old_seals: bool,
 ) -> Result<AuraImportQueue<B>, consensus_common::Error> where
 	B: Block,
-	C: 'static + Authorities<B> + ProvideRuntimeApi + Send + Sync,
-	C::Api: BlockBuilderApi<B>,
+	C: 'static + ProvideRuntimeApi + ProvideCache<B> + Send + Sync,
+	C::Api: BlockBuilderApi<B> + AuthoritiesApi<B>,
 	DigestItemFor<B>: CompatibleDigestItem<P> + DigestItem<AuthorityId=AuthorityId<P>>,
 	E: 'static + ExtraVerification<B>,
 	P: Pair + Send + Sync + 'static,
@@ -889,4 +920,16 @@ mod tests {

 		runtime.block_on(wait_for.select(drive_to_completion).map_err(|_| ())).unwrap();
 	}
+
+	#[test]
+	fn authorities_call_works() {
+		let client = test_client::new();
+
+		assert_eq!(client.info().unwrap().chain.best_number, 0);
+		assert_eq!(authorities(&client, &BlockId::Number(0)).unwrap(), vec![
+			Keyring::Alice.into(),
+			Keyring::Bob.into(),
+			Keyring::Charlie.into()
+		]);
+	}
 }
@@ -0,0 +1,29 @@
+[package]
+name = "substrate-consensus-authorities"
+version = "0.1.0"
+authors = ["Parity Technologies <admin@parity.io>"]
+description = "Primitives for Aura consensus"
+edition = "2018"
+
+[dependencies]
+parity-codec = { version = "3.0", default-features = false }
+substrate-client = { path = "../../client", default-features = false }
+primitives = { package = "substrate-primitives", path = "../../primitives", default-features = false }
+runtime_support = { package = "srml-support", path = "../../../srml/support", default-features = false }
+runtime_primitives = { package = "sr-primitives", path = "../../sr-primitives", default-features = false }
+sr-version = { path = "../../sr-version", default-features = false }
+runtime_io = { package = "sr-io", path = "../../sr-io", default-features = false }
+rstd = { package = "sr-std", path = "../../sr-std", default-features = false }
+
+[features]
+default = ["std"]
+std = [
+	"parity-codec/std",
+	"substrate-client/std",
+	"primitives/std",
+	"runtime_support/std",
+	"runtime_primitives/std",
+	"sr-version/std",
+	"runtime_io/std",
+	"rstd/std"
+]
@@ -0,0 +1,31 @@
+// Copyright 2019 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate 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.
+
+// Substrate 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 Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Authorities API.
+
+#![cfg_attr(not(feature = "std"), no_std)]
+
+use substrate_client::decl_runtime_apis;
+use runtime_primitives::traits::AuthorityIdFor;
+use rstd::vec::Vec;
+
+decl_runtime_apis! {
+	/// Authorities API.
+	pub trait AuthoritiesApi {
+		/// Returns the authorities at the given block.
+		fn authorities() -> Vec<AuthorityIdFor<Block>>;
+	}
+}
@@ -16,9 +16,10 @@

 //! Block import helpers.

-use runtime_primitives::traits::{AuthorityIdFor, Block as BlockT, DigestItemFor, Header as HeaderT, NumberFor};
+use runtime_primitives::traits::{Block as BlockT, DigestItemFor, Header as HeaderT, NumberFor};
 use runtime_primitives::Justification;
 use std::borrow::Cow;
+use std::collections::HashMap;

 /// Block import result.
 #[derive(Debug, PartialEq, Eq)]
@@ -175,11 +176,13 @@ pub trait BlockImport<B: BlockT> {
 		parent_hash: B::Hash,
 	) -> Result<ImportResult, Self::Error>;

-	/// Import a Block alongside the new authorities valid from this block forward
+	/// Import a block.
+	///
+	/// Cached data can be accessed through the blockchain cache.
 	fn import_block(
 		&self,
 		block: ImportBlock<B>,
-		new_authorities: Option<Vec<AuthorityIdFor<B>>>,
+		cache: HashMap<Vec<u8>, Vec<u8>>,
 	) -> Result<ImportResult, Self::Error>;
 }

@@ -58,6 +58,12 @@ error_chain! {
 			display("Message signature {:?} by {:?} is invalid.", s, a),
 		}

+		/// Invalid authorities set received from the runtime.
+		InvalidAuthoritiesSet {
+			description("authorities set is invalid"),
+			display("Current state of blockchain has invalid authorities set"),
+		}
+
 		/// Account is not an authority.
 		InvalidAuthority(a: Public) {
 			description("Message sender is not a valid authority"),
@@ -28,6 +28,7 @@ use crate::block_import::{
 	BlockImport, BlockOrigin, ImportBlock, ImportedAux, ImportResult, JustificationImport,
 };
 use crossbeam_channel::{self as channel, Receiver, Sender};
+use parity_codec::Encode;

 use std::sync::Arc;
 use std::thread;
@@ -38,6 +39,7 @@ use runtime_primitives::traits::{
 use runtime_primitives::Justification;

 use crate::error::Error as ConsensusError;
+use parity_codec::alloc::collections::hash_map::HashMap;

 /// Shared block import struct used by the queue.
 pub type SharedBlockImport<B> = Arc<dyn BlockImport<B, Error = ConsensusError> + Send + Sync>;
@@ -566,7 +568,12 @@ pub fn import_single_block<B: BlockT, V: Verifier<B>>(
 			BlockImportError::VerificationFailed(peer.clone(), msg)
 		})?;

-	import_error(import_handle.import_block(import_block, new_authorities))
+	let mut cache = HashMap::new();
+	if let Some(authorities) = new_authorities {
+		cache.insert(crate::well_known_cache_keys::AUTHORITIES.to_vec(), authorities.encode());
+	}
+
+	import_error(import_handle.import_block(import_block, cache))
 }

 #[cfg(test)]
@@ -53,7 +53,9 @@ pub use block_import::{

 /// Trait for getting the authorities at a given block.
 pub trait Authorities<B: Block> {
-	type Error: ::std::error::Error + Send + 'static;	/// Get the authorities at the given block.
+	type Error: std::error::Error + Send + 'static;
+
+	/// Get the authorities at the given block.
 	fn authorities(&self, at: &BlockId<B>) -> Result<Vec<AuthorityIdFor<B>>, Self::Error>;
 }

@@ -115,3 +117,9 @@ impl<T: SyncOracle> SyncOracle for Arc<T> {
 		T::is_offline(&*self)
 	}
 }
+
+/// A list of all well known keys in the cache.
+pub mod well_known_cache_keys {
+	/// A list of authorities.
+	pub const AUTHORITIES: &'static [u8] = b"auth";
+}
@@ -14,7 +14,7 @@
 // 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::sync::Arc;
+use std::{sync::Arc, collections::HashMap};

 use log::{debug, trace, info};
 use parity_codec::Encode;
@@ -388,7 +388,7 @@ impl<B, E, Block: BlockT<Hash=H256>, RA, PRA> BlockImport<Block>
 {
 	type Error = ConsensusError;

-	fn import_block(&self, mut block: ImportBlock<Block>, new_authorities: Option<Vec<AuthorityId>>)
+	fn import_block(&self, mut block: ImportBlock<Block>, new_cache: HashMap<Vec<u8>, Vec<u8>>)
 		-> Result<ImportResult, Self::Error>
 	{
 		let hash = block.post_header().hash();
@@ -406,8 +406,8 @@ impl<B, E, Block: BlockT<Hash=H256>, RA, PRA> BlockImport<Block>

 		// we don't want to finalize on `inner.import_block`
 		let mut justification = block.justification.take();
-		let enacts_consensus_change = new_authorities.is_some();
-		let import_result = self.inner.import_block(block, new_authorities);
+		let enacts_consensus_change = !new_cache.is_empty();
+		let import_result = self.inner.import_block(block, new_cache);

 		let mut imported_aux = {
 			match import_result {
@@ -277,16 +277,6 @@ impl Core<Block> for RuntimeApi {
 		unimplemented!("Not required for testing!")
 	}

-	fn authorities_runtime_api_impl(
-		&self,
-		_: &BlockId<Block>,
-		_: ExecutionContext,
-		_: Option<()>,
-		_: Vec<u8>,
-	) -> Result<NativeOrEncoded<Vec<AuthorityId>>> {
-		unimplemented!("Not required for testing!")
-	}
-
 	fn execute_block_runtime_api_impl(
 		&self,
 		_: &BlockId<Block>,
@@ -992,12 +982,12 @@ fn allows_reimporting_change_blocks() {
 	};

 	assert_eq!(
-		block_import.import_block(block(), None).unwrap(),
+		block_import.import_block(block(), HashMap::new()).unwrap(),
 		ImportResult::Imported(ImportedAux { needs_justification: true, clear_justification_requests: false, bad_justification: false }),
 	);

 	assert_eq!(
-		block_import.import_block(block(), None).unwrap(),
+		block_import.import_block(block(), HashMap::new()).unwrap(),
 		ImportResult::AlreadyInChain
 	);
 }
@@ -1035,12 +1025,12 @@ fn test_bad_justification() {
 	};

 	assert_eq!(
-		block_import.import_block(block(), None).unwrap(),
+		block_import.import_block(block(), HashMap::new()).unwrap(),
 		ImportResult::Imported(ImportedAux { needs_justification: true, clear_justification_requests: false, bad_justification: true }),
 	);

 	assert_eq!(
-		block_import.import_block(block(), None).unwrap(),
+		block_import.import_block(block(), HashMap::new()).unwrap(),
 		ImportResult::AlreadyInChain
 	);
 }
@@ -20,18 +20,13 @@ use client::{self, Client as SubstrateClient, ClientInfo, BlockStatus, CallExecu
 use client::error::Error;
 use client::light::fetcher::ChangesProof;
 use consensus::{BlockImport, Error as ConsensusError};
-use runtime_primitives::traits::{Block as BlockT, Header as HeaderT, AuthorityIdFor};
+use runtime_primitives::traits::{Block as BlockT, Header as HeaderT};
 use runtime_primitives::generic::{BlockId};
-use consensus::{ImportBlock, ImportResult};
 use runtime_primitives::Justification;
 use primitives::{H256, Blake2Hasher, storage::StorageKey};

 /// Local client abstraction for the network.
 pub trait Client<Block: BlockT>: Send + Sync {
-	/// Import a new block. Parent is supposed to be existing in the blockchain.
-	fn import(&self, block: ImportBlock<Block>, new_authorities: Option<Vec<AuthorityIdFor<Block>>>)
-		-> Result<ImportResult, ConsensusError>;
-
 	/// Get blockchain info.
 	fn info(&self) -> Result<ClientInfo<Block>, Error>;

@@ -80,12 +75,6 @@ impl<B, E, Block, RA> Client<Block> for SubstrateClient<B, E, Block, RA> where
 	Block: BlockT<Hash=H256>,
 	RA: Send + Sync
 {
-	fn import(&self, block: ImportBlock<Block>, new_authorities: Option<Vec<AuthorityIdFor<Block>>>)
-		-> Result<ImportResult, ConsensusError>
-	{
-		(self as &SubstrateClient<B, E, Block, RA>).import_block(block, new_authorities)
-	}
-
 	fn info(&self) -> Result<ClientInfo<Block>, Error> {
 		(self as &SubstrateClient<B, E, Block, RA>).info()
 	}
@@ -221,7 +221,7 @@ fn should_return_runtime_version() {

 	assert_eq!(
 		::serde_json::to_string(&api.runtime_version(None.into()).unwrap()).unwrap(),
-		r#"{"specName":"test","implName":"parity-test","authoringVersion":1,"specVersion":1,"implVersion":1,"apis":[["0xdf6acb689907609b",1],["0x37e397fc7c91f5e4",1],["0xd2bc9897eed08f15",1],["0x40fe3ad401f8959a",2],["0xc6e9a76309f39b09",1],["0xdd718d5cc53262d4",1],["0xf78b278be53f454c",1]]}"#
+		r#"{"specName":"test","implName":"parity-test","authoringVersion":1,"specVersion":1,"implVersion":1,"apis":[["0xdf6acb689907609b",1],["0x37e397fc7c91f5e4",1],["0xd2bc9897eed08f15",1],["0x40fe3ad401f8959a",2],["0xc6e9a76309f39b09",1],["0xdd718d5cc53262d4",1],["0xf78b278be53f454c",1],["0x7801759919ee83e5",1]]}"#
 	);
 }

@@ -20,6 +20,7 @@ use std::iter;
 use std::sync::Arc;
 use std::net::Ipv4Addr;
 use std::time::Duration;
+use std::collections::HashMap;
 use log::info;
 use futures::{Future, Stream};
 use tempdir::TempDir;
@@ -227,7 +228,7 @@ where
 				info!("Generating #{}", i);
 			}
 			let import_data = block_factory(&first_service);
-			first_service.client().import_block(import_data, None).expect("Error importing test block");
+			first_service.client().import_block(import_data, HashMap::new()).expect("Error importing test block");
 		}
 		first_service.network().node_id().unwrap()
 	};
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU General Public License
 // along with Substrate.  If not, see <http://www.gnu.org/licenses/>.

-use runtime_primitives::traits::{GetNodeBlockType, Block as BlockT, AuthorityIdFor};
+use runtime_primitives::traits::{GetNodeBlockType, Block as BlockT};
 use runtime_primitives::generic::BlockId;
 use client::runtime_api::{self, RuntimeApiInfo};
 use client::{error::Result, decl_runtime_apis, impl_runtime_apis};
@@ -68,9 +68,6 @@ impl_runtime_apis! {
 		fn version() -> runtime_api::RuntimeVersion {
 			unimplemented!()
 		}
-		fn authorities() -> Vec<AuthorityIdFor<Block>> {
-			unimplemented!()
-		}
 		fn execute_block(_: Block) {
 			unimplemented!()
 		}
@@ -22,6 +22,7 @@ use runtime_primitives::Justification;
 use runtime_primitives::generic::BlockId;
 use primitives::Blake2Hasher;
 use runtime;
+use parity_codec::alloc::collections::hash_map::HashMap;

 /// Extension trait for a test client.
 pub trait TestClient: Sized {
@@ -60,7 +61,7 @@ impl<B, E, RA> TestClient for Client<B, E, runtime::Block, RA>
 			fork_choice: ForkChoiceStrategy::LongestChain,
 		};

-		self.import_block(import, None).map(|_| ())
+		self.import_block(import, HashMap::new()).map(|_| ())
 	}

 	fn import_justified(&self, origin: BlockOrigin, block: runtime::Block, justification: Justification)
@@ -77,7 +78,7 @@ impl<B, E, RA> TestClient for Client<B, E, runtime::Block, RA>
 			fork_choice: ForkChoiceStrategy::LongestChain,
 		};

-		self.import_block(import, None).map(|_| ())
+		self.import_block(import, HashMap::new()).map(|_| ())
 	}

 	fn finalize_block(&self, id: BlockId<runtime::Block>, justification: Option<Justification>) -> client::error::Result<()> {
@@ -23,6 +23,7 @@ runtime_support = { package = "srml-support", path = "../../srml/support", defau
 offchain-primitives = { package = "substrate-offchain-primitives", path = "../offchain/primitives", default-features = false}
 executive = { package = "srml-executive", path = "../../srml/executive", default-features = false }
 cfg-if = "0.1.6"
+consensus_authorities = { package = "substrate-consensus-authorities", path = "../../core/consensus/authorities", default-features = false }

 [dev-dependencies]
 substrate-executor = { path = "../executor" }
@@ -34,7 +34,7 @@ use runtime_primitives::{
 	create_runtime_str,
 	traits::{
 		BlindCheckable, BlakeTwo256, Block as BlockT, Extrinsic as ExtrinsicT,
-		GetNodeBlockType, GetRuntimeBlockType,
+		GetNodeBlockType, GetRuntimeBlockType, AuthorityIdFor,
 	},
 };
 use runtime_version::RuntimeVersion;
@@ -289,10 +289,6 @@ cfg_if! {
 					version()
 				}

-				fn authorities() -> Vec<AuthorityId> {
-					system::authorities()
-				}
-
 				fn execute_block(block: Block) {
 					system::execute_block(block)
 				}
@@ -386,6 +382,12 @@ cfg_if! {
 					runtime_io::submit_extrinsic(&ex)
 				}
 			}
+
+			impl consensus_authorities::AuthoritiesApi<Block> for Runtime {
+				fn authorities() -> Vec<AuthorityIdFor<Block>> {
+					crate::system::authorities()
+				}
+			}
 		}
 	} else {
 		impl_runtime_apis! {
@@ -394,10 +396,6 @@ cfg_if! {
 					version()
 				}

-				fn authorities() -> Vec<AuthorityId> {
-					system::authorities()
-				}
-
 				fn execute_block(block: Block) {
 					system::execute_block(block)
 				}
@@ -496,6 +494,12 @@ cfg_if! {
 					runtime_io::submit_extrinsic(&ex)
 				}
 			}
+
+			impl consensus_authorities::AuthoritiesApi<Block> for Runtime {
+				fn authorities() -> Vec<AuthorityIdFor<Block>> {
+					crate::system::authorities()
+				}
+			}
 		}
 	}
 }
@@ -2284,6 +2284,20 @@ dependencies = [
 "substrate-client 0.1.0",
 ]

+[[package]]
+name = "substrate-consensus-authorities"
+version = "0.1.0"
+dependencies = [
+ "parity-codec 3.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sr-io 0.1.0",
+ "sr-primitives 0.1.0",
+ "sr-std 0.1.0",
+ "sr-version 0.1.0",
+ "srml-support 0.1.0",
+ "substrate-client 0.1.0",
+ "substrate-primitives 0.1.0",
+]
+
 [[package]]
 name = "substrate-consensus-common"
 version = "0.1.0"
@@ -2453,6 +2467,7 @@ dependencies = [
 "srml-support 0.1.0",
 "substrate-client 0.1.0",
 "substrate-consensus-aura-primitives 0.1.0",
+ "substrate-consensus-authorities 0.1.0",
 "substrate-inherents 0.1.0",
 "substrate-keyring 0.1.0",
 "substrate-offchain-primitives 0.1.0",
@@ -26,6 +26,7 @@ runtime-primitives = { package = "sr-primitives", path = "../../core/sr-primitiv
 client = { package = "substrate-client", path = "../../core/client", default_features = false }
 consensus-aura = { package = "substrate-consensus-aura-primitives", path = "../../core/consensus/aura/primitives", default_features = false }
 offchain-primitives = { package = "substrate-offchain-primitives", path = "../../core/offchain/primitives", default-features = false }
+consensus_authorities = { package = "substrate-consensus-authorities", path = "../../core/consensus/authorities", default-features = false }

 [features]
 default = ["std"]
@@ -234,10 +234,6 @@ impl_runtime_apis! {
 			VERSION
 		}

-		fn authorities() -> Vec<AuthorityId> {
-			Consensus::authorities()
-		}
-
 		fn execute_block(block: Block) {
 			Executive::execute_block(block)
 		}
@@ -292,4 +288,10 @@ impl_runtime_apis! {
 			Executive::offchain_worker(n)
 		}
 	}
+
+	impl consensus_authorities::AuthoritiesApi<Block> for Runtime {
+		fn authorities() -> Vec<AuthorityId> {
+			Consensus::authorities()
+		}
+	}
 }
@@ -1273,6 +1273,7 @@ dependencies = [
 "srml-timestamp 0.1.0",
 "substrate-client 0.1.0",
 "substrate-consensus-aura-primitives 0.1.0",
+ "substrate-consensus-authorities 0.1.0",
 "substrate-offchain-primitives 0.1.0",
 "substrate-primitives 0.1.0",
 ]
@@ -2449,6 +2450,20 @@ dependencies = [
 "substrate-client 0.1.0",
 ]

+[[package]]
+name = "substrate-consensus-authorities"
+version = "0.1.0"
+dependencies = [
+ "parity-codec 3.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sr-io 0.1.0",
+ "sr-primitives 0.1.0",
+ "sr-std 0.1.0",
+ "sr-version 0.1.0",
+ "srml-support 0.1.0",
+ "substrate-client 0.1.0",
+ "substrate-primitives 0.1.0",
+]
+
 [[package]]
 name = "substrate-consensus-common"
 version = "0.1.0"
@@ -86,30 +86,32 @@ construct_service_factory! {
 		FullImportQueue = AuraImportQueue<
 			Self::Block,
 		>
-			{ |config: &mut FactoryFullConfiguration<Self> , client: Arc<FullClient<Self>>|
+			{ |config: &mut FactoryFullConfiguration<Self> , client: Arc<FullClient<Self>>| {
 				import_queue::<_, _, _, Pair>(
-					SlotDuration::get_or_compute(&*client)?,
-					client.clone(),
-					None,
-					client,
-					NothingExtra,
-					config.custom.inherent_data_providers.clone(),
+						SlotDuration::get_or_compute(&*client)?,
+						client.clone(),
+						None,
+						client,
+						NothingExtra,
+						config.custom.inherent_data_providers.clone(),
 					true,
-				).map_err(Into::into)
+					).map_err(Into::into)
+				}
 			},
 		LightImportQueue = AuraImportQueue<
 			Self::Block,
 		>
-			{ |config: &mut FactoryFullConfiguration<Self>, client: Arc<LightClient<Self>>|
+			{ |config: &mut FactoryFullConfiguration<Self>, client: Arc<LightClient<Self>>| {
 				import_queue::<_, _, _, Pair>(
-					SlotDuration::get_or_compute(&*client)?,
-					client.clone(),
-					None,
-					client,
-					NothingExtra,
-					config.custom.inherent_data_providers.clone(),
+						SlotDuration::get_or_compute(&*client)?,
+						client.clone(),
+						None,
+						client,
+						NothingExtra,
+						config.custom.inherent_data_providers.clone(),
 					true,
-				).map_err(Into::into)
+					).map_err(Into::into)
+				}
 			},
 	}
 }
@@ -37,6 +37,7 @@ rustc-hex = { version = "2.0", optional = true }
 hex-literal = { version = "0.1.0", optional = true }
 serde = { version = "1.0", optional = true }
 substrate-keyring = { path = "../../core/keyring", optional = true }
+consensus_authorities = { package = "substrate-consensus-authorities", path = "../../core/consensus/authorities", default-features = false }

 [features]
 default = ["std"]
@@ -34,7 +34,8 @@ use client::{
 use runtime_primitives::{ApplyResult, generic, create_runtime_str};
 use runtime_primitives::transaction_validity::TransactionValidity;
 use runtime_primitives::traits::{
-	BlakeTwo256, Block as BlockT, DigestFor, NumberFor, StaticLookup, CurrencyToVoteHandler
+	BlakeTwo256, Block as BlockT, DigestFor, NumberFor, StaticLookup, CurrencyToVoteHandler,
+	AuthorityIdFor,
 };
 use version::RuntimeVersion;
 use council::{motions as council_motions, voting as council_voting};
@@ -58,8 +59,8 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
 	spec_name: create_runtime_str!("node"),
 	impl_name: create_runtime_str!("substrate-node"),
 	authoring_version: 10,
-	spec_version: 52,
-	impl_version: 52,
+	spec_version: 53,
+	impl_version: 53,
 	apis: RUNTIME_API_VERSIONS,
 };

@@ -243,10 +244,6 @@ impl_runtime_apis! {
 			VERSION
 		}

-		fn authorities() -> Vec<AuthorityId> {
-			Consensus::authorities()
-		}
-
 		fn execute_block(block: Block) {
 			Executive::execute_block(block)
 		}
@@ -335,4 +332,10 @@ impl_runtime_apis! {
 			Aura::slot_duration()
 		}
 	}
+
+	impl consensus_authorities::AuthoritiesApi<Block> for Runtime {
+		fn authorities() -> Vec<AuthorityIdFor<Block>> {
+			Consensus::authorities()
+		}
+	}
 }
@@ -1296,6 +1296,7 @@ dependencies = [
 "srml-treasury 0.1.0",
 "substrate-client 0.1.0",
 "substrate-consensus-aura-primitives 0.1.0",
+ "substrate-consensus-authorities 0.1.0",
 "substrate-keyring 0.1.0",
 "substrate-offchain-primitives 0.1.0",
 "substrate-primitives 0.1.0",
@@ -2593,6 +2594,20 @@ dependencies = [
 "substrate-client 0.1.0",
 ]

+[[package]]
+name = "substrate-consensus-authorities"
+version = "0.1.0"
+dependencies = [
+ "parity-codec 3.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sr-io 0.1.0",
+ "sr-primitives 0.1.0",
+ "sr-std 0.1.0",
+ "sr-version 0.1.0",
+ "srml-support 0.1.0",
+ "substrate-client 0.1.0",
+ "substrate-primitives 0.1.0",
+]
+
 [[package]]
 name = "substrate-consensus-common"
 version = "0.1.0"
@@ -470,7 +470,7 @@ impl<T: Trait> Module<T> {
 			// NOTE: this must be the last potential bailer, since it changes state.
 			T::Currency::reserve(&who, Self::voting_bond())?;

-			<Voters<T>>::mutate(|mut v| v.push(who.clone()));
+			<Voters<T>>::mutate(|v| v.push(who.clone()));
 		}
 		<LastActiveOf<T>>::insert(&who, index);
 		<ApprovalsOf<T>>::insert(&who, votes);