Blockchain cache pruning strategy (#3395)

* blockchain cache pruning strategy

* added some internal docs to cache_pruning_strategy

* Update core/client/db/src/cache/mod.rs

Co-Authored-By: DemiMarie-parity <48690212+DemiMarie-parity@users.noreply.github.com>

substrate/core/client/db/src/cache/list_cache.rs

@@ -52,12 +52,21 @@ use crate::cache::{CacheItemT, ComplexBlockId, EntryType};
 use crate::cache::list_entry::{Entry, StorageEntry};
 use crate::cache::list_storage::{Storage, StorageTransaction, Metadata};
 
+/// Pruning strategy.
+#[derive(Debug, Clone, Copy)]
+pub enum PruningStrategy<N> {
+	/// Prune entries when they're too far behind best finalized block.
+	ByDepth(N),
+	/// Do not prune old entries at all.
+	NeverPrune,
+}
+
 /// List-based cache.
 pub struct ListCache<Block: BlockT, T: CacheItemT, S: Storage<Block, T>> {
 	/// Cache storage.
 	storage: S,
-	/// Prune depth.
-	prune_depth: NumberFor<Block>,
+	/// Pruning strategy.
+	pruning_strategy: PruningStrategy<NumberFor<Block>>,
 	/// Best finalized block.
 	best_finalized_block: ComplexBlockId<Block>,
 	/// Best finalized entry (if exists).
@@ -107,7 +116,11 @@ pub enum ForkAppendResult<Block: BlockT> {
 
 impl<Block: BlockT, T: CacheItemT, S: Storage<Block, T>> ListCache<Block, T, S> {
 	/// Create new db list cache entry.
-	pub fn new(storage: S, prune_depth: NumberFor<Block>, best_finalized_block: ComplexBlockId<Block>) -> Self {
+	pub fn new(
+		storage: S,
+		pruning_strategy: PruningStrategy<NumberFor<Block>>,
+		best_finalized_block: ComplexBlockId<Block>,
+	) -> Self {
 		let (best_finalized_entry, unfinalized) = storage.read_meta()
 			.and_then(|meta| read_forks(&storage, meta))
 			.unwrap_or_else(|error| {
@@ -117,7 +130,7 @@ impl<Block: BlockT, T: CacheItemT, S: Storage<Block, T>> ListCache<Block, T, S>
 
 		ListCache {
 			storage,
-			prune_depth,
+			pruning_strategy,
 			best_finalized_block,
 			best_finalized_entry,
 			unfinalized,
@@ -362,9 +375,14 @@ impl<Block: BlockT, T: CacheItemT, S: Storage<Block, T>> ListCache<Block, T, S>
 		tx: &mut Tx,
 		block: &ComplexBlockId<Block>
 	) {
+		let prune_depth = match self.pruning_strategy {
+			PruningStrategy::ByDepth(prune_depth) => prune_depth,
+			PruningStrategy::NeverPrune => return,
+		};
+
 		let mut do_pruning = || -> ClientResult<()> {
 			// calculate last ancient block number
-			let ancient_block = match block.number.checked_sub(&self.prune_depth) {
+			let ancient_block = match block.number.checked_sub(&prune_depth) {
 				Some(number) => match self.storage.read_id(number)? {
 					Some(hash) => ComplexBlockId::new(hash, number),
 					None => return Ok(()),
@@ -669,7 +687,7 @@ pub mod tests {
 		// when block is earlier than best finalized block AND it is not finalized
 		// --- 50 ---
 		// ----------> [100]
-		assert_eq!(ListCache::<_, u64, _>::new(DummyStorage::new(), 1024, test_id(100))
+		assert_eq!(ListCache::<_, u64, _>::new(DummyStorage::new(), PruningStrategy::ByDepth(1024), test_id(100))
 			.value_at_block(&test_id(50)).unwrap(), None);
 		// when block is earlier than best finalized block AND it is finalized AND value is some
 		// [30] ---- 50 ---> [100]
@@ -679,7 +697,7 @@ pub mod tests {
 				.with_id(50, H256::from_low_u64_be(50))
 				.with_entry(test_id(100), StorageEntry { prev_valid_from: Some(test_id(30)), value: 100 })
 				.with_entry(test_id(30), StorageEntry { prev_valid_from: None, value: 30 }),
-			1024, test_id(100)
+			PruningStrategy::ByDepth(1024), test_id(100)
 		).value_at_block(&test_id(50)).unwrap(), Some((test_id(30), Some(test_id(100)), 30)));
 		// when block is the best finalized block AND value is some
 		// ---> [100]
@@ -689,7 +707,7 @@ pub mod tests {
 				.with_id(100, H256::from_low_u64_be(100))
 				.with_entry(test_id(100), StorageEntry { prev_valid_from: Some(test_id(30)), value: 100 })
 				.with_entry(test_id(30), StorageEntry { prev_valid_from: None, value: 30 }),
-			1024, test_id(100)
+			PruningStrategy::ByDepth(1024), test_id(100)
 		).value_at_block(&test_id(100)).unwrap(), Some((test_id(100), None, 100)));
 		// when block is parallel to the best finalized block
 		// ---- 100
@@ -700,7 +718,7 @@ pub mod tests {
 				.with_id(50, H256::from_low_u64_be(50))
 				.with_entry(test_id(100), StorageEntry { prev_valid_from: Some(test_id(30)), value: 100 })
 				.with_entry(test_id(30), StorageEntry { prev_valid_from: None, value: 30 }),
-			1024, test_id(100)
+			PruningStrategy::ByDepth(1024), test_id(100)
 		).value_at_block(&ComplexBlockId::new(H256::from_low_u64_be(2), 100)).unwrap(), None);
 
 		// when block is later than last finalized block AND there are no forks AND finalized value is Some
@@ -710,7 +728,7 @@ pub mod tests {
 				.with_meta(Some(test_id(100)), Vec::new())
 				.with_id(50, H256::from_low_u64_be(50))
 				.with_entry(test_id(100), StorageEntry { prev_valid_from: Some(test_id(30)), value: 100 }),
-			1024, test_id(100)
+			PruningStrategy::ByDepth(1024), test_id(100)
 		).value_at_block(&test_id(200)).unwrap(), Some((test_id(100), None, 100)));
 
 		// when block is later than last finalized block AND there are no matching forks
@@ -726,7 +744,7 @@ pub mod tests {
 				.with_header(test_header(3))
 				.with_header(test_header(4))
 				.with_header(fork_header(0, 2, 3)),
-			1024, test_id(2)
+			PruningStrategy::ByDepth(1024), test_id(2)
 		).value_at_block(&fork_id(0, 2, 3)).unwrap(), Some((correct_id(2), None, 2)));
 		// when block is later than last finalized block AND there are no matching forks
 		// AND block is not connected to finalized block
@@ -743,7 +761,7 @@ pub mod tests {
 				.with_header(test_header(4))
 				.with_header(fork_header(0, 1, 3))
 				.with_header(fork_header(0, 1, 2)),
-			1024, test_id(2)
+			PruningStrategy::ByDepth(1024), test_id(2)
 		).value_at_block(&fork_id(0, 1, 3)).unwrap(), None);
 
 		// when block is later than last finalized block AND it appends to unfinalized fork from the end
@@ -756,7 +774,7 @@ pub mod tests {
 				.with_entry(correct_id(4), StorageEntry { prev_valid_from: Some(correct_id(2)), value: 4 })
 				.with_header(test_header(4))
 				.with_header(test_header(5)),
-			1024, test_id(2)
+			PruningStrategy::ByDepth(1024), test_id(2)
 		).value_at_block(&correct_id(5)).unwrap(), Some((correct_id(4), None, 4)));
 		// when block is later than last finalized block AND it does not fits unfinalized fork
 		// AND it is connected to the finalized block AND finalized value is Some
@@ -771,7 +789,7 @@ pub mod tests {
 				.with_header(test_header(3))
 				.with_header(test_header(4))
 				.with_header(fork_header(0, 2, 3)),
-			1024, test_id(2)
+			PruningStrategy::ByDepth(1024), test_id(2)
 		).value_at_block(&fork_id(0, 2, 3)).unwrap(), Some((correct_id(2), None, 2)));
 	}
 
@@ -781,7 +799,7 @@ pub mod tests {
 		let fin = EntryType::Final;
 
 		// when trying to insert block < finalized number
-		assert!(ListCache::new(DummyStorage::new(), 1024, test_id(100))
+		assert!(ListCache::new(DummyStorage::new(), PruningStrategy::ByDepth(1024), test_id(100))
 			.on_block_insert(
 				&mut DummyTransaction::new(),
 				test_id(49),
@@ -790,7 +808,7 @@ pub mod tests {
 				nfin,
 			).unwrap().is_none());
 		// when trying to insert block @ finalized number
-		assert!(ListCache::new(DummyStorage::new(), 1024, test_id(100))
+		assert!(ListCache::new(DummyStorage::new(), PruningStrategy::ByDepth(1024), test_id(100))
 			.on_block_insert(
 				&mut DummyTransaction::new(),
 				test_id(99),
@@ -805,7 +823,7 @@ pub mod tests {
 			DummyStorage::new()
 				.with_meta(None, vec![test_id(4)])
 				.with_entry(test_id(4), StorageEntry { prev_valid_from: None, value: 4 }),
-			1024, test_id(2)
+			PruningStrategy::ByDepth(1024), test_id(2)
 		);
 		cache.unfinalized[0].best_block = Some(test_id(4));
 		let mut tx = DummyTransaction::new();
@@ -830,7 +848,7 @@ pub mod tests {
 				.with_meta(None, vec![correct_id(4)])
 				.with_entry(correct_id(4), StorageEntry { prev_valid_from: None, value: 4 })
 				.with_header(test_header(4)),
-			1024, test_id(2)
+			PruningStrategy::ByDepth(1024), test_id(2)
 		);
 		let mut tx = DummyTransaction::new();
 		assert_eq!(cache.on_block_insert(&mut tx, correct_id(4), correct_id(5), Some(4), nfin).unwrap(),
@@ -856,7 +874,7 @@ pub mod tests {
 				.with_header(test_header(2))
 				.with_header(test_header(3))
 				.with_header(test_header(4)),
-			1024, correct_id(2)
+			PruningStrategy::ByDepth(1024), correct_id(2)
 		);
 		let mut tx = DummyTransaction::new();
 		assert_eq!(cache.on_block_insert(&mut tx, correct_id(3), fork_id(0, 3, 4), Some(14), nfin).unwrap(),
@@ -871,7 +889,7 @@ pub mod tests {
 			DummyStorage::new()
 				.with_meta(Some(correct_id(2)), vec![])
 				.with_entry(correct_id(2), StorageEntry { prev_valid_from: None, value: 2 }),
-			1024, correct_id(2)
+			PruningStrategy::ByDepth(1024), correct_id(2)
 		);
 		let mut tx = DummyTransaction::new();
 		assert_eq!(cache.on_block_insert(&mut tx, correct_id(2), correct_id(3), Some(2), nfin).unwrap(), None);
@@ -884,7 +902,7 @@ pub mod tests {
 			DummyStorage::new()
 				.with_meta(Some(correct_id(2)), vec![])
 				.with_entry(correct_id(2), StorageEntry { prev_valid_from: None, value: 2 }),
-			1024, correct_id(2)
+			PruningStrategy::ByDepth(1024), correct_id(2)
 		);
 		let mut tx = DummyTransaction::new();
 		assert_eq!(cache.on_block_insert(&mut tx, correct_id(2), correct_id(3), Some(3), nfin).unwrap(),
@@ -894,7 +912,7 @@ pub mod tests {
 		assert_eq!(*tx.updated_meta(), Some(Metadata { finalized: Some(correct_id(2)), unfinalized: vec![correct_id(3)] }));
 
 		// when inserting finalized entry AND there are no previous finalized entries
-		let cache = ListCache::new(DummyStorage::new(), 1024, correct_id(2));
+		let cache = ListCache::new(DummyStorage::new(), PruningStrategy::ByDepth(1024), correct_id(2));
 		let mut tx = DummyTransaction::new();
 		assert_eq!(
 			cache.on_block_insert(&mut tx, correct_id(2), correct_id(3), Some(3), fin).unwrap(),
@@ -912,7 +930,7 @@ pub mod tests {
 			DummyStorage::new()
 				.with_meta(Some(correct_id(2)), vec![])
 				.with_entry(correct_id(2), StorageEntry { prev_valid_from: None, value: 2 }),
-			1024, correct_id(2)
+			PruningStrategy::ByDepth(1024), correct_id(2)
 		);
 		let mut tx = DummyTransaction::new();
 		assert_eq!(cache.on_block_insert(&mut tx, correct_id(2), correct_id(3), Some(2), fin).unwrap(),
@@ -940,7 +958,7 @@ pub mod tests {
 				.with_meta(Some(correct_id(2)), vec![fork_id(0, 1, 3)])
 				.with_entry(correct_id(2), StorageEntry { prev_valid_from: None, value: 2 })
 				.with_entry(fork_id(0, 1, 3), StorageEntry { prev_valid_from: None, value: 13 }),
-			1024, correct_id(2)
+			PruningStrategy::ByDepth(1024), correct_id(2)
 		);
 		let mut tx = DummyTransaction::new();
 		assert_eq!(cache.on_block_insert(&mut tx, correct_id(2), correct_id(3), Some(2), fin).unwrap(),
@@ -955,7 +973,7 @@ pub mod tests {
 				.with_meta(Some(correct_id(2)), vec![correct_id(5)])
 				.with_entry(correct_id(2), StorageEntry { prev_valid_from: None, value: 2 })
 				.with_entry(correct_id(5), StorageEntry { prev_valid_from: Some(correct_id(2)), value: 5 }),
-			1024, correct_id(2)
+			PruningStrategy::ByDepth(1024), correct_id(2)
 		);
 		let mut tx = DummyTransaction::new();
 		assert_eq!(cache.on_block_finalize(&mut tx, correct_id(2), correct_id(3)).unwrap(),
@@ -969,7 +987,7 @@ pub mod tests {
 				.with_meta(Some(correct_id(2)), vec![correct_id(5)])
 				.with_entry(correct_id(2), StorageEntry { prev_valid_from: None, value: 2 })
 				.with_entry(correct_id(5), StorageEntry { prev_valid_from: Some(correct_id(2)), value: 5 }),
-			1024, correct_id(4)
+			PruningStrategy::ByDepth(1024), correct_id(4)
 		);
 		let mut tx = DummyTransaction::new();
 		assert_eq!(
@@ -989,7 +1007,7 @@ pub mod tests {
 				.with_meta(Some(correct_id(2)), vec![fork_id(0, 1, 3)])
 				.with_entry(correct_id(2), StorageEntry { prev_valid_from: None, value: 2 })
 				.with_entry(fork_id(0, 1, 3), StorageEntry { prev_valid_from: None, value: 13 }),
-			1024, correct_id(2)
+			PruningStrategy::ByDepth(1024), correct_id(2)
 		);
 		let mut tx = DummyTransaction::new();
 		assert_eq!(cache.on_block_finalize(&mut tx, correct_id(2), correct_id(3)).unwrap(),
@@ -1004,7 +1022,7 @@ pub mod tests {
 				.with_entry(correct_id(2), StorageEntry { prev_valid_from: None, value: 2 })
 				.with_entry(correct_id(5), StorageEntry { prev_valid_from: Some(correct_id(2)), value: 5 })
 				.with_entry(correct_id(6), StorageEntry { prev_valid_from: Some(correct_id(5)), value: 6 }),
-			1024, correct_id(2)
+			PruningStrategy::ByDepth(1024), correct_id(2)
 		);
 
 		// when new block is appended to unfinalized fork
@@ -1043,7 +1061,7 @@ pub mod tests {
 				.with_header(test_header(3))
 				.with_header(test_header(4))
 				.with_header(test_header(5)),
-			1024, correct_id(0)
+			PruningStrategy::ByDepth(1024), correct_id(0)
 		).find_unfinalized_fork(&correct_id(4)).unwrap().unwrap().head.valid_from, correct_id(5));
 		// --- [2] ---------------> [5]
 		// ----------> [3] ---> 4
@@ -1060,7 +1078,7 @@ pub mod tests {
 				.with_header(fork_header(0, 1, 2))
 				.with_header(fork_header(0, 1, 3))
 				.with_header(fork_header(0, 1, 4)),
-			1024, correct_id(0)
+			PruningStrategy::ByDepth(1024), correct_id(0)
 		).find_unfinalized_fork(&fork_id(0, 1, 4)).unwrap().unwrap().head.valid_from, fork_id(0, 1, 3));
 		// --- [2] ---------------> [5]
 		// ----------> [3]
@@ -1080,7 +1098,7 @@ pub mod tests {
 				.with_header(fork_header(1, 1, 2))
 				.with_header(fork_header(1, 1, 3))
 				.with_header(fork_header(1, 1, 4)),
-			1024, correct_id(0)
+			PruningStrategy::ByDepth(1024), correct_id(0)
 		).find_unfinalized_fork(&fork_id(1, 1, 4)).unwrap().is_none());
 	}
 
@@ -1341,32 +1359,45 @@ pub mod tests {
 	}
 
 	#[test]
-	fn ancient_entries_are_pruned() {
-		let cache = ListCache::new(DummyStorage::new()
-			.with_id(10, H256::from_low_u64_be(10))
-			.with_id(20, H256::from_low_u64_be(20))
-			.with_id(30, H256::from_low_u64_be(30))
-			.with_entry(test_id(10), StorageEntry { prev_valid_from: None, value: 10 })
-			.with_entry(test_id(20), StorageEntry { prev_valid_from: Some(test_id(10)), value: 20 })
-			.with_entry(test_id(30), StorageEntry { prev_valid_from: Some(test_id(20)), value: 30 }),
-		10, test_id(9));
-		let mut tx = DummyTransaction::new();
+	fn ancient_entries_are_pruned_when_pruning_enabled() {
+		fn do_test(strategy: PruningStrategy<u64>) {
+			let cache = ListCache::new(DummyStorage::new()
+				.with_id(10, H256::from_low_u64_be(10))
+				.with_id(20, H256::from_low_u64_be(20))
+				.with_id(30, H256::from_low_u64_be(30))
+				.with_entry(test_id(10), StorageEntry { prev_valid_from: None, value: 10 })
+				.with_entry(test_id(20), StorageEntry { prev_valid_from: Some(test_id(10)), value: 20 })
+				.with_entry(test_id(30), StorageEntry { prev_valid_from: Some(test_id(20)), value: 30 }),
+			strategy, test_id(9));
+			let mut tx = DummyTransaction::new();
 
-		// when finalizing entry #10: no entries pruned
-		cache.prune_finalized_entries(&mut tx, &test_id(10));
-		assert!(tx.removed_entries().is_empty());
-		assert!(tx.inserted_entries().is_empty());
-		// when finalizing entry #19: no entries pruned
-		cache.prune_finalized_entries(&mut tx, &test_id(19));
-		assert!(tx.removed_entries().is_empty());
-		assert!(tx.inserted_entries().is_empty());
-		// when finalizing entry #20: no entries pruned
-		cache.prune_finalized_entries(&mut tx, &test_id(20));
-		assert!(tx.removed_entries().is_empty());
-		assert!(tx.inserted_entries().is_empty());
-		// when finalizing entry #30: entry 10 pruned + entry 20 is truncated
-		cache.prune_finalized_entries(&mut tx, &test_id(30));
-		assert_eq!(*tx.removed_entries(), vec![test_id(10).hash].into_iter().collect());
-		assert_eq!(*tx.inserted_entries(), vec![test_id(20).hash].into_iter().collect());
+			// when finalizing entry #10: no entries pruned
+			cache.prune_finalized_entries(&mut tx, &test_id(10));
+			assert!(tx.removed_entries().is_empty());
+			assert!(tx.inserted_entries().is_empty());
+			// when finalizing entry #19: no entries pruned
+			cache.prune_finalized_entries(&mut tx, &test_id(19));
+			assert!(tx.removed_entries().is_empty());
+			assert!(tx.inserted_entries().is_empty());
+			// when finalizing entry #20: no entries pruned
+			cache.prune_finalized_entries(&mut tx, &test_id(20));
+			assert!(tx.removed_entries().is_empty());
+			assert!(tx.inserted_entries().is_empty());
+			// when finalizing entry #30: entry 10 pruned + entry 20 is truncated (if pruning is enabled)
+			cache.prune_finalized_entries(&mut tx, &test_id(30));
+			match strategy {
+				PruningStrategy::NeverPrune => {
+					assert!(tx.removed_entries().is_empty());
+					assert!(tx.inserted_entries().is_empty());
+				},
+				PruningStrategy::ByDepth(_) => {
+					assert_eq!(*tx.removed_entries(), vec![test_id(10).hash].into_iter().collect());
+					assert_eq!(*tx.inserted_entries(), vec![test_id(20).hash].into_iter().collect());
+				},
+			}
+		}
+
+		do_test(PruningStrategy::ByDepth(10));
+		do_test(PruningStrategy::NeverPrune)
 	}
 }

substrate/core/client/db/src/cache/mod.rs

@@ -21,15 +21,14 @@ use parking_lot::RwLock;
 
 use kvdb::{KeyValueDB, DBTransaction};
 
-use client::blockchain::Cache as BlockchainCache;
+use client::blockchain::{well_known_cache_keys::{self, Id as CacheKeyId}, Cache as BlockchainCache};
 use client::error::Result as ClientResult;
 use codec::{Encode, Decode};
 use sr_primitives::generic::BlockId;
 use sr_primitives::traits::{Block as BlockT, Header as HeaderT, NumberFor, Zero};
-use consensus_common::well_known_cache_keys::Id as CacheKeyId;
 use crate::utils::{self, COLUMN_META, db_err};
 
-use self::list_cache::ListCache;
+use self::list_cache::{ListCache, PruningStrategy};
 
 mod list_cache;
 mod list_entry;
@@ -166,7 +165,7 @@ fn get_cache_helper<'a, Block: BlockT>(
 					cache,
 				},
 			),
-			PRUNE_DEPTH.into(),
+			cache_pruning_strategy(name),
 			best_finalized_block.clone(),
 		)
 	})
@@ -335,3 +334,17 @@ impl<Block: BlockT> BlockchainCache<Block> for DbCacheSync<Block> {
 	}
 }
 
+/// Get pruning strategy for given cache.
+fn cache_pruning_strategy<N: From<u32>>(cache: CacheKeyId) -> PruningStrategy<N> {
+	// the cache is mostly used to store data from consensus engines
+	// this kind of data is only required for non-finalized blocks
+	// => by default we prune finalized cached entries
+
+	match cache {
+		// we need to keep changes tries configurations forever (or at least until changes tries,
+		// that were built using this configuration, are pruned) to make it possible to refer
+		// to old changes tries
+		well_known_cache_keys::CHANGES_TRIE_CONFIG => PruningStrategy::NeverPrune,
+		_ => PruningStrategy::ByDepth(PRUNE_DEPTH.into()),
+	}
+}

substrate/core/client/db/src/lib.rs

@@ -39,7 +39,7 @@ use std::io;
 use std::collections::{HashMap, HashSet};
 
 use client::backend::NewBlockState;
-use client::blockchain::HeaderBackend;
+use client::blockchain::{well_known_cache_keys, HeaderBackend};
 use client::ExecutionStrategies;
 use client::backend::{StorageCollection, ChildStorageCollection};
 use codec::{Decode, Encode};
@@ -65,7 +65,6 @@ use crate::utils::{Meta, db_err, meta_keys, read_db, block_id_to_lookup_key, rea
 use client::leaves::{LeafSet, FinalizationDisplaced};
 use client::children;
 use state_db::StateDb;
-use consensus_common::well_known_cache_keys;
 use crate::storage_cache::{CachingState, SharedCache, new_shared_cache};
 use log::{trace, debug, warn};
 pub use state_db::PruningMode;

substrate/core/client/db/src/light.rs

@@ -23,8 +23,11 @@ use parking_lot::RwLock;
 use kvdb::{KeyValueDB, DBTransaction};
 
 use client::backend::{AuxStore, NewBlockState};
-use client::blockchain::{BlockStatus, Cache as BlockchainCache,
-	HeaderBackend as BlockchainHeaderBackend, Info as BlockchainInfo};
+use client::blockchain::{
+	BlockStatus, Cache as BlockchainCache,
+	HeaderBackend as BlockchainHeaderBackend, Info as BlockchainInfo,
+	well_known_cache_keys,
+};
 use client::cht;
 use client::error::{Error as ClientError, Result as ClientResult};
 use client::light::blockchain::Storage as LightBlockchainStorage;
@@ -32,7 +35,6 @@ use codec::{Decode, Encode};
 use primitives::Blake2Hasher;
 use sr_primitives::generic::{DigestItem, BlockId};
 use sr_primitives::traits::{Block as BlockT, Header as HeaderT, Zero, One, NumberFor};
-use consensus_common::well_known_cache_keys;
 use crate::cache::{DbCacheSync, DbCache, ComplexBlockId, EntryType as CacheEntryType};
 use crate::utils::{self, meta_keys, Meta, db_err, read_db, block_id_to_lookup_key, read_meta};
 use crate::DatabaseSettings;

substrate/core/client/src/backend.rs

@@ -25,7 +25,8 @@ use sr_primitives::{generic::BlockId, Justification, StorageOverlay, ChildrenSto
 use sr_primitives::traits::{Block as BlockT, NumberFor};
 use state_machine::backend::Backend as StateBackend;
 use state_machine::{ChangesTrieStorage as StateChangesTrieStorage, ChangesTrieTransaction};
-use consensus::{well_known_cache_keys, BlockOrigin};
+use crate::blockchain::well_known_cache_keys;
+use consensus::BlockOrigin;
 use hash_db::Hasher;
 use parking_lot::Mutex;
 

substrate/core/client/src/blockchain.rs

@@ -21,7 +21,6 @@ use std::sync::Arc;
 use sr_primitives::traits::{Block as BlockT, Header as HeaderT, NumberFor};
 use sr_primitives::generic::BlockId;
 use sr_primitives::Justification;
-use consensus::well_known_cache_keys;
 
 use crate::error::{Error, Result};
 
@@ -254,3 +253,18 @@ pub fn tree_route<Block: BlockT, F: Fn(BlockId<Block>) -> Result<<Block as Block
 		pivot,
 	})
 }
+
+/// A list of all well known keys in the blockchain cache.
+pub mod well_known_cache_keys {
+	/// The type representing cache keys.
+	pub type Id = consensus::import_queue::CacheKeyId;
+
+	/// A list of authorities.
+	pub const AUTHORITIES: Id = *b"auth";
+
+	/// Current Epoch data.
+	pub const EPOCH: Id = *b"epch";
+
+	/// Changes trie configuration.
+	pub const CHANGES_TRIE_CONFIG: Id = *b"chtr";
+}

substrate/core/client/src/client.rs

@@ -49,7 +49,6 @@ use executor::{RuntimeVersion, RuntimeInfo};
 use consensus::{
 	Error as ConsensusError, BlockImportParams,
 	ImportResult, BlockOrigin, ForkChoiceStrategy,
-	well_known_cache_keys::Id as CacheKeyId,
 	SelectChain, self,
 };
 
@@ -65,6 +64,7 @@ use crate::{
 	blockchain::{
 		self, Info as ChainInfo, Backend as ChainBackend,
 		HeaderBackend as ChainHeaderBackend, ProvideCache, Cache,
+		well_known_cache_keys::Id as CacheKeyId,
 	},
 	call_executor::{CallExecutor, LocalCallExecutor},
 	notifications::{StorageNotifications, StorageEventStream},

substrate/core/client/src/in_mem.rs

@@ -27,13 +27,12 @@ use state_machine::backend::{Backend as StateBackend, InMemory};
 use state_machine::{self, InMemoryChangesTrieStorage, ChangesTrieAnchorBlockId, ChangesTrieTransaction};
 use hash_db::{Hasher, Prefix};
 use trie::MemoryDB;
-use consensus::well_known_cache_keys::Id as CacheKeyId;
 
 use crate::error;
 use crate::backend::{self, NewBlockState, StorageCollection, ChildStorageCollection};
 use crate::light;
 use crate::leaves::LeafSet;
-use crate::blockchain::{self, BlockStatus, HeaderBackend};
+use crate::blockchain::{self, BlockStatus, HeaderBackend, well_known_cache_keys::Id as CacheKeyId};
 
 struct PendingBlock<B: BlockT> {
 	block: StoredBlock<B>,

substrate/core/client/src/lib.rs

@@ -124,6 +124,8 @@ pub use crate::notifications::{StorageEventStream, StorageChangeSet};
 pub use state_machine::ExecutionStrategy;
 #[cfg(feature = "std")]
 pub use crate::leaves::LeafSet;
+#[cfg(feature = "std")]
+pub use crate::blockchain::well_known_cache_keys;
 
 #[doc(inline)]
 pub use sr_api_macros::{decl_runtime_apis, impl_runtime_apis};

substrate/core/client/src/light/backend.rs

@@ -29,12 +29,11 @@ use crate::backend::{
 	AuxStore, Backend as ClientBackend, BlockImportOperation, RemoteBackend, NewBlockState,
 	StorageCollection, ChildStorageCollection,
 };
-use crate::blockchain::HeaderBackend as BlockchainHeaderBackend;
+use crate::blockchain::{HeaderBackend as BlockchainHeaderBackend, well_known_cache_keys};
 use crate::error::{Error as ClientError, Result as ClientResult};
 use crate::light::blockchain::{Blockchain, Storage as BlockchainStorage};
 use hash_db::Hasher;
 use trie::MemoryDB;
-use consensus::well_known_cache_keys;
 
 const IN_MEMORY_EXPECT_PROOF: &str = "InMemory state backend has Void error type and always succeeds; qed";
 

substrate/core/client/src/light/blockchain.rs

@@ -22,11 +22,13 @@ use std::{sync::Arc, collections::HashMap};
 
 use sr_primitives::{Justification, generic::BlockId};
 use sr_primitives::traits::{Block as BlockT, Header as HeaderT, NumberFor, Zero};
-use consensus::well_known_cache_keys;
 
 use crate::backend::{AuxStore, NewBlockState};
-use crate::blockchain::{Backend as BlockchainBackend, BlockStatus, Cache as BlockchainCache,
-	HeaderBackend as BlockchainHeaderBackend, Info as BlockchainInfo, ProvideCache};
+use crate::blockchain::{
+	Backend as BlockchainBackend, BlockStatus, Cache as BlockchainCache,
+	HeaderBackend as BlockchainHeaderBackend, Info as BlockchainInfo, ProvideCache,
+	well_known_cache_keys,
+};
 use crate::cht;
 use crate::error::{Error as ClientError, Result as ClientResult};
 use crate::light::fetcher::{Fetcher, RemoteHeaderRequest};

substrate/core/consensus/aura/src/lib.rs

@@ -33,7 +33,7 @@ use std::{sync::Arc, time::Duration, thread, marker::PhantomData, hash::Hash, fm
 use codec::{Encode, Decode, Codec};
 use consensus_common::{self, BlockImport, Environment, Proposer,
 	ForkChoiceStrategy, BlockImportParams, BlockOrigin, Error as ConsensusError,
-	SelectChain, well_known_cache_keys::{self, Id as CacheKeyId}
+	SelectChain,
 };
 use consensus_common::import_queue::{
 	Verifier, BasicQueue, BoxBlockImport, BoxJustificationImport, BoxFinalityProofImport,
@@ -41,6 +41,7 @@ use consensus_common::import_queue::{
 use client::{
 	block_builder::api::BlockBuilder as BlockBuilderApi, blockchain::ProvideCache,
 	runtime_api::ApiExt, error::Result as CResult, backend::AuxStore, BlockOf,
+	well_known_cache_keys::{self, Id as CacheKeyId},
 };
 
 use sr_primitives::{generic::{BlockId, OpaqueDigestItemId}, Justification};

substrate/core/consensus/babe/src/lib.rs

@@ -65,7 +65,6 @@ use consensus_common::ImportResult;
 use consensus_common::import_queue::{
 	BoxJustificationImport, BoxFinalityProofImport,
 };
-use consensus_common::well_known_cache_keys::Id as CacheKeyId;
 use sr_primitives::{generic::{BlockId, OpaqueDigestItemId}, Justification};
 use sr_primitives::traits::{
 	Block as BlockT, Header, DigestItemFor, NumberFor, ProvideRuntimeApi,
@@ -96,7 +95,7 @@ use srml_babe::{
 	BabeInherentData,
 	timestamp::{TimestampInherentData, InherentType as TimestampInherent}
 };
-use consensus_common::{SelectChain, well_known_cache_keys};
+use consensus_common::SelectChain;
 use consensus_common::import_queue::{Verifier, BasicQueue};
 use client::{
 	block_builder::api::BlockBuilder as BlockBuilderApi,
@@ -104,6 +103,7 @@ use client::{
 	runtime_api::ApiExt, error::Result as ClientResult, backend::{AuxStore, Backend},
 	ProvideUncles,
 	utils::is_descendent_of,
+	well_known_cache_keys::{self, Id as CacheKeyId},
 };
 use fork_tree::ForkTree;
 use slots::{CheckedHeader, check_equivocation};

substrate/core/consensus/common/src/block_import.rs

@@ -21,9 +21,8 @@ use sr_primitives::Justification;
 use std::borrow::Cow;
 use std::collections::HashMap;
 use std::sync::Arc;
-use crate::well_known_cache_keys;
 
-use crate::import_queue::Verifier;
+use crate::import_queue::{Verifier, CacheKeyId};
 
 /// Block import result.
 #[derive(Debug, PartialEq, Eq)]
@@ -182,7 +181,7 @@ pub trait BlockImport<B: BlockT> {
 	fn import_block(
 		&mut self,
 		block: BlockImportParams<B>,
-		cache: HashMap<well_known_cache_keys::Id, Vec<u8>>,
+		cache: HashMap<CacheKeyId, Vec<u8>>,
 	) -> Result<ImportResult, Self::Error>;
 }
 
@@ -202,7 +201,7 @@ where for<'r> &'r T: BlockImport<B, Error = E>
 	fn import_block(
 		&mut self,
 		block: BlockImportParams<B>,
-		cache: HashMap<well_known_cache_keys::Id, Vec<u8>>,
+		cache: HashMap<CacheKeyId, Vec<u8>>,
 	) -> Result<ImportResult, Self::Error> {
 		(&**self).import_block(block, cache)
 	}

substrate/core/consensus/common/src/import_queue.rs

@@ -27,7 +27,7 @@
 
 use std::collections::HashMap;
 use sr_primitives::{Justification, traits::{Block as BlockT, Header as _, NumberFor}};
-use crate::{error::Error as ConsensusError, well_known_cache_keys::Id as CacheKeyId};
+use crate::error::Error as ConsensusError;
 use crate::block_import::{
 	BlockImport, BlockOrigin, BlockImportParams, ImportedAux, JustificationImport, ImportResult,
 	FinalityProofImport,
@@ -65,6 +65,9 @@ pub struct IncomingBlock<B: BlockT> {
 	pub origin: Option<Origin>,
 }
 
+/// Type of keys in the blockchain cache that consensus module could use for its needs.
+pub type CacheKeyId = [u8; 4];
+
 /// Verify a justification of a block
 pub trait Verifier<B: BlockT>: Send + Sync {
 	/// Verify the given data and return the BlockImportParams and an optional

substrate/core/consensus/common/src/lib.rs

@@ -117,15 +117,3 @@ where T: ?Sized, for<'r> &'r T: SyncOracle
 		<&T>::is_offline(&mut &**self)
 	}
 }
-
-/// A list of all well known keys in the cache.
-pub mod well_known_cache_keys {
-	/// The type representing cache keys.
-	pub type Id = [u8; 4];
-
-	/// A list of authorities.
-	pub const AUTHORITIES: Id = *b"auth";
-
-	/// Current Epoch data.
-	pub const EPOCH: Id = *b"epch";
-}

substrate/core/consensus/pow/src/lib.rs

@@ -35,6 +35,7 @@ use std::collections::HashMap;
 use client::{
 	BlockOf, blockchain::{HeaderBackend, ProvideCache},
 	block_builder::api::BlockBuilder as BlockBuilderApi, backend::AuxStore,
+	well_known_cache_keys::Id as CacheKeyId,
 };
 use sr_primitives::Justification;
 use sr_primitives::generic::{BlockId, Digest, DigestItem};
@@ -45,7 +46,7 @@ use primitives::H256;
 use inherents::{InherentDataProviders, InherentData};
 use consensus_common::{
 	BlockImportParams, BlockOrigin, ForkChoiceStrategy,
-	well_known_cache_keys::Id as CacheKeyId, Environment, Proposer,
+	Environment, Proposer,
 };
 use consensus_common::import_queue::{BoxBlockImport, BasicQueue, Verifier};
 use codec::{Encode, Decode};

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

@@ -21,14 +21,14 @@ use codec::Encode;
 use futures::sync::mpsc;
 use parking_lot::RwLockWriteGuard;
 
-use client::{blockchain, CallExecutor, Client};
+use client::{blockchain, CallExecutor, Client, well_known_cache_keys};
 use client::blockchain::HeaderBackend;
 use client::backend::Backend;
 use client::runtime_api::ApiExt;
 use client::utils::is_descendent_of;
 use consensus_common::{
 	BlockImport, Error as ConsensusError,
-	BlockImportParams, ImportResult, JustificationImport, well_known_cache_keys,
+	BlockImportParams, ImportResult, JustificationImport,
 	SelectChain,
 };
 use fg_primitives::GrandpaApi;

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

@@ -24,10 +24,11 @@ use client::{
 	backend::{AuxStore, Backend, Finalizer},
 	blockchain::HeaderBackend,
 	error::Error as ClientError,
+	well_known_cache_keys,
 };
 use codec::{Encode, Decode};
 use consensus_common::{
-	import_queue::Verifier, well_known_cache_keys,
+	import_queue::Verifier,
 	BlockOrigin, BlockImport, FinalityProofImport, BlockImportParams, ImportResult, ImportedAux,
 	Error as ConsensusError,
 };

substrate/core/network/src/test/mod.rs

@@ -28,10 +28,12 @@ use crate::config::build_multiaddr;
 use log::trace;
 use crate::chain::FinalityProofProvider;
 use client::{
-	self, ClientInfo, BlockchainEvents, BlockImportNotification, FinalityNotifications, ImportNotifications,
-	FinalityNotification, LongestChain
+	self, ClientInfo, BlockchainEvents, BlockImportNotification,
+	FinalityNotifications, ImportNotifications,
+	FinalityNotification, LongestChain,
+	error::Result as ClientResult,
+	well_known_cache_keys::{self, Id as CacheKeyId},
 };
-use client::error::Result as ClientResult;
 use client::block_builder::BlockBuilder;
 use client::backend::{AuxStore, Backend, Finalizer};
 use crate::config::Roles;
@@ -40,7 +42,7 @@ use consensus::import_queue::{
 	BoxBlockImport, BoxJustificationImport, Verifier, BoxFinalityProofImport,
 };
 use consensus::block_import::{BlockImport, ImportResult};
-use consensus::{Error as ConsensusError, well_known_cache_keys::{self, Id as CacheKeyId}};
+use consensus::Error as ConsensusError;
 use consensus::{BlockOrigin, ForkChoiceStrategy, BlockImportParams, JustificationImport};
 use futures::prelude::*;
 use futures03::{StreamExt as _, TryStreamExt as _};