Handle reorganizations in the state cache (#2490)

* Handle reorganizations in the state cache

* Renamed and documented a few methods

* Basic test

* Renamed pending to buffered

* Updated cache on sealed block

* More renames and updated documentation

* Minor doc tweaks

ethcore/src/client/client.rs

@@ -304,8 +304,7 @@ impl Client {
 		// Enact Verified Block
 		let parent = chain_has_parent.unwrap();
 		let last_hashes = self.build_last_hashes(header.parent_hash().clone());
-		let is_canon = header.parent_hash() == &chain.best_block_hash();
-		let db = if is_canon { self.state_db.lock().boxed_clone_canon() } else { self.state_db.lock().boxed_clone() };
+		let db = self.state_db.lock().boxed_clone_canon(&header.parent_hash());
 
 		let enact_result = enact_verified(block, engine, self.tracedb.read().tracing_enabled(), db, &parent, last_hashes, self.factories.clone());
 		if let Err(e) = enact_result {
@@ -459,6 +458,8 @@ impl Client {
 			enacted: route.enacted.clone(),
 			retracted: route.retracted.len()
 		});
+		let is_canon = route.enacted.last().map_or(false, |h| h == hash);
+		state.sync_cache(&route.enacted, &route.retracted, is_canon);
 		// Final commit to the DB
 		self.db.read().write_buffered(batch);
 		chain.commit();
@@ -533,9 +534,11 @@ impl Client {
 
 	/// Get a copy of the best block's state.
 	pub fn state(&self) -> State {
+		let header = self.best_block_header();
+		let header = HeaderView::new(&header);
 		State::from_existing(
-			self.state_db.lock().boxed_clone(),
-			HeaderView::new(&self.best_block_header()).state_root(),
+			self.state_db.lock().boxed_clone_canon(&header.hash()),
+			header.state_root(),
 			self.engine.account_start_nonce(),
 			self.factories.clone())
 		.expect("State root of best block header always valid.")
@@ -1128,6 +1131,7 @@ impl MiningBlockChainClient for Client {
 		let block_data = block.rlp_bytes();
 		let route = self.commit_block(block, &h, &block_data);
 		trace!(target: "client", "Imported sealed block #{} ({})", number, h);
+		self.state_db.lock().sync_cache(&route.enacted, &route.retracted, false);
 
 		let (enacted, retracted) = self.calculate_enacted_retracted(&[route]);
 		self.miner.chain_new_blocks(self, &[h.clone()], &[], &enacted, &retracted);

ethcore/src/state/mod.rs

@@ -164,8 +164,8 @@ impl AccountEntry {
 /// use that.
 /// ****************************************************************************
 ///
-/// Upon destruction all the local cache data merged into the global cache.
-/// The merge might be rejected if current state is non-canonical.
+/// Upon destruction all the local cache data propagated into the global cache.
+/// Propagated items might be rejected if current state is non-canonical.
 ///
 /// State snapshotting.
 ///
@@ -318,7 +318,7 @@ impl State {
 
 	/// Destroy the current object and return root and database.
 	pub fn drop(mut self) -> (H256, StateDB) {
-		self.commit_cache();
+		self.propagate_to_global_cache();
 		(self.root, self.db)
 	}
 
@@ -533,11 +533,12 @@ impl State {
 		Ok(())
 	}
 
-	fn commit_cache(&mut self) {
+	/// Propagate local cache into shared canonical state cache.
+	fn propagate_to_global_cache(&mut self) {
 		let mut addresses = self.cache.borrow_mut();
 		trace!("Committing cache {:?} entries", addresses.len());
 		for (address, a) in addresses.drain().filter(|&(_, ref a)| a.state == AccountState::Committed || a.state == AccountState::CleanFresh) {
-			self.db.cache_account(address, a.account);
+			self.db.add_to_account_cache(address, a.account, a.state == AccountState::Committed);
 		}
 	}