Chain scoring (#4218)

* chain scoring

* use current steps

ethcore/src/blockchain/blockchain.rs

@@ -34,7 +34,6 @@ use blockchain::update::ExtrasUpdate;
 use blockchain::{CacheSize, ImportRoute, Config};
 use db::{self, Writable, Readable, CacheUpdatePolicy};
 use cache_manager::CacheManager;
-use engines::Engine;
 use encoded;
 
 const LOG_BLOOMS_LEVELS: usize = 3;
@@ -200,9 +199,6 @@ pub struct BlockChain {
 	pending_block_hashes: RwLock<HashMap<BlockNumber, H256>>,
 	pending_block_details: RwLock<HashMap<H256, BlockDetails>>,
 	pending_transaction_addresses: RwLock<HashMap<H256, Option<TransactionAddress>>>,
-
-	// Used for block ordering.
-	engine: Arc<Engine>,
 }
 
 impl BlockProvider for BlockChain {
@@ -424,8 +420,8 @@ impl<'a> Iterator for AncestryIter<'a> {
 }
 
 impl BlockChain {
-	/// Create new instance of blockchain from given Genesis and block picking rules of Engine.
+	/// Create new instance of blockchain from given Genesis.
-	pub fn new(config: Config, genesis: &[u8], db: Arc<Database>, engine: Arc<Engine>) -> BlockChain {
+	pub fn new(config: Config, genesis: &[u8], db: Arc<Database>) -> BlockChain {
 		// 400 is the avarage size of the key
 		let cache_man = CacheManager::new(config.pref_cache_size, config.max_cache_size, 400);
 
@@ -450,7 +446,6 @@ impl BlockChain {
 			pending_block_hashes: RwLock::new(HashMap::new()),
 			pending_block_details: RwLock::new(HashMap::new()),
 			pending_transaction_addresses: RwLock::new(HashMap::new()),
-			engine: engine,
 		};
 
 		// load best block
@@ -867,7 +862,7 @@ impl BlockChain {
 		let number = header.number();
 		let parent_hash = header.parent_hash();
 		let parent_details = self.block_details(&parent_hash).unwrap_or_else(|| panic!("Invalid parent hash: {:?}", parent_hash));
-		let is_new_best = self.engine.is_new_best_block(self.best_block_total_difficulty(), self.best_block_header().view(), &parent_details, header);
+		let is_new_best = parent_details.total_difficulty + header.difficulty() > self.best_block_total_difficulty();
 
 		BlockInfo {
 			hash: hash,
@@ -1328,7 +1323,6 @@ mod tests {
 	use views::BlockView;
 	use transaction::{Transaction, Action};
 	use log_entry::{LogEntry, LocalizedLogEntry};
-	use spec::Spec;
 	use ethkey::Secret;
 
 	fn new_db(path: &str) -> Arc<Database> {
@@ -1336,7 +1330,7 @@ mod tests {
 	}
 
 	fn new_chain(genesis: &[u8], db: Arc<Database>) -> BlockChain {
-		BlockChain::new(Config::default(), genesis, db, Spec::new_null().engine)
+		BlockChain::new(Config::default(), genesis, db)
 	}
 
 	#[test]

ethcore/src/client/client.rs

@@ -192,7 +192,7 @@ impl Client {
 		}
 
 		let gb = spec.genesis_block();
-		let chain = Arc::new(BlockChain::new(config.blockchain.clone(), &gb, db.clone(), spec.engine.clone()));
+		let chain = Arc::new(BlockChain::new(config.blockchain.clone(), &gb, db.clone()));
 		let tracedb = RwLock::new(TraceDB::new(config.tracing.clone(), db.clone(), chain.clone()));
 
 		trace!("Cleanup journal: DB Earliest = {:?}, Latest = {:?}", state_db.journal_db().earliest_era(), state_db.journal_db().latest_era());
@@ -857,7 +857,7 @@ impl snapshot::DatabaseRestore for Client {
 
 		let cache_size = state_db.cache_size();
 		*state_db = StateDB::new(journaldb::new(db.clone(), self.pruning, ::db::COL_STATE), cache_size);
-		*chain = Arc::new(BlockChain::new(self.config.blockchain.clone(), &[], db.clone(), self.engine.clone()));
+		*chain = Arc::new(BlockChain::new(self.config.blockchain.clone(), &[], db.clone()));
 		*tracedb = TraceDB::new(self.config.tracing.clone(), db.clone(), chain.clone());
 		Ok(())
 	}

ethcore/src/engines/authority_round.rs

@@ -21,15 +21,13 @@ use std::sync::Weak;
 use std::time::{UNIX_EPOCH, Duration};
 use util::*;
 use ethkey::{verify_address, Signature};
-use rlp::{UntrustedRlp, Rlp, View, encode};
+use rlp::{UntrustedRlp, View, encode};
 use account_provider::AccountProvider;
 use block::*;
 use spec::CommonParams;
 use engines::{Engine, Seal, EngineError};
 use header::Header;
 use error::{Error, BlockError};
-use blockchain::extras::BlockDetails;
-use views::HeaderView;
 use evm::Schedule;
 use ethjson;
 use io::{IoContext, IoHandler, TimerToken, IoService};
@@ -208,7 +206,9 @@ impl Engine for AuthorityRound {
 	}
 
 	fn populate_from_parent(&self, header: &mut Header, parent: &Header, gas_floor_target: U256, _gas_ceil_target: U256) {
-		header.set_difficulty(parent.difficulty().clone());
+		// Chain scoring: total weight is sqrt(U256::max_value())*height - step
+		let new_difficulty = U256::from(U128::max_value()) + header_step(parent).expect("Header has been verified; qed").into() - self.step.load(AtomicOrdering::SeqCst).into();
+		header.set_difficulty(new_difficulty);
 		header.set_gas_limit({
 			let gas_limit = parent.gas_limit().clone();
 			let bound_divisor = self.gas_limit_bound_divisor;
@@ -309,19 +309,6 @@ impl Engine for AuthorityRound {
 		Ok(())
 	}
 
-	fn is_new_best_block(&self, _best_total_difficulty: U256, best_header: HeaderView, _parent_details: &BlockDetails, new_header: &HeaderView) -> bool {
-		let new_number = new_header.number();
-		let best_number = best_header.number();
-		if new_number != best_number {
-			new_number > best_number
-		} else {
- 			// Take the oldest step at given height.
- 			let new_step: usize = Rlp::new(&new_header.seal()[0]).as_val();
-			let best_step: usize = Rlp::new(&best_header.seal()[0]).as_val();
-			new_step < best_step
-		}
-	}
-
 	fn register_client(&self, client: Weak<Client>) {
 		*self.client.write() = Some(client.clone());
 		self.validators.register_call_contract(client);

ethcore/src/engines/mod.rs

@@ -41,9 +41,6 @@ use spec::CommonParams;
 use evm::Schedule;
 use header::Header;
 use transaction::{UnverifiedTransaction, SignedTransaction};
-use ethereum::ethash;
-use blockchain::extras::BlockDetails;
-use views::HeaderView;
 use client::Client;
 
 /// Voting errors.
@@ -177,7 +174,7 @@ pub trait Engine : Sync + Send {
 	}
 
 	/// Populate a header's fields based on its parent's header.
-	/// Takes gas floor and ceiling targets.
+	/// Usually implements the chain scoring rule based on weight.
 	/// The gas floor target must not be lower than the engine's minimum gas limit.
 	fn populate_from_parent(&self, header: &mut Header, parent: &Header, _gas_floor_target: U256, _gas_ceil_target: U256) {
 		header.set_difficulty(parent.difficulty().clone());
@@ -203,11 +200,6 @@ pub trait Engine : Sync + Send {
 		self.builtins().get(a).expect("attempted to execute nonexistent builtin").execute(input, output);
 	}
 
-	/// Check if new block should be chosen as the one  in chain.
-	fn is_new_best_block(&self, best_total_difficulty: U256, _best_header: HeaderView, parent_details: &BlockDetails, new_header: &HeaderView) -> bool {
-		ethash::is_new_best_block(best_total_difficulty, parent_details, new_header)
-	}
-
 	/// Find out if the block is a proposal block and should not be inserted into the DB.
 	/// Takes a header of a fully verified block.
 	fn is_proposal(&self, _verified_header: &Header) -> bool { false }

ethcore/src/engines/tendermint/message.rs

@@ -53,7 +53,8 @@ impl VoteStep {
 	}
 }
 
-fn consensus_round(header: &Header) -> Result<Round, ::rlp::DecoderError> {
+/// Header consensus round.
+pub fn consensus_round(header: &Header) -> Result<Round, ::rlp::DecoderError> {
 	let round_rlp = header.seal().get(0).expect("seal passed basic verification; seal has 3 fields; qed");
 	UntrustedRlp::new(round_rlp.as_slice()).as_val()
 }

ethcore/src/engines/tendermint/mod.rs

@@ -41,8 +41,6 @@ use account_provider::AccountProvider;
 use block::*;
 use spec::CommonParams;
 use engines::{Engine, Seal, EngineError};
-use blockchain::extras::BlockDetails;
-use views::HeaderView;
 use evm::Schedule;
 use state::CleanupMode;
 use io::IoService;
@@ -397,7 +395,9 @@ impl Engine for Tendermint {
 	}
 
 	fn populate_from_parent(&self, header: &mut Header, parent: &Header, gas_floor_target: U256, _gas_ceil_target: U256) {
-		header.set_difficulty(parent.difficulty().clone());
+		// Chain scoring: total weight is sqrt(U256::max_value())*height - round
+		let new_difficulty = U256::from(U128::max_value()) + consensus_round(parent).expect("Header has been verified; qed").into() - self.round.load(AtomicOrdering::SeqCst).into();
+		header.set_difficulty(new_difficulty);
 		header.set_gas_limit({
 			let gas_limit = parent.gas_limit().clone();
 			let bound_divisor = self.gas_limit_bound_divisor;
@@ -565,27 +565,6 @@ impl Engine for Tendermint {
 		self.step_service.stop()
 	}
 
-	fn is_new_best_block(&self, _best_total_difficulty: U256, best_header: HeaderView, _parent_details: &BlockDetails, new_header: &HeaderView) -> bool {
-		let new_number = new_header.number();
-		let best_number = best_header.number();
-		trace!(target: "poa", "new_header: {}, best_header: {}", new_number, best_number);
-		if new_number != best_number {
-			new_number > best_number
-		} else {
-			let new_seal = new_header.seal();
-			let best_seal = best_header.seal();
-			let new_signatures = new_seal.get(2).expect("Tendermint seal should have three elements.").len();
-			let best_signatures = best_seal.get(2).expect("Tendermint seal should have three elements.").len();
-			if new_signatures > best_signatures {
-				true
-			} else {
-				let new_round: Round = ::rlp::Rlp::new(&new_seal.get(0).expect("Tendermint seal should have three elements.")).as_val();
-				let best_round: Round = ::rlp::Rlp::new(&best_seal.get(0).expect("Tendermint seal should have three elements.")).as_val();
-				new_round > best_round
-			}
-		}
-	}
-
 	fn is_proposal(&self, header: &Header) -> bool {
 		let signatures_len = header.seal()[2].len();
 		// Signatures have to be an empty list rlp.

ethcore/src/ethereum/ethash.rs

@@ -21,7 +21,6 @@ use builtin::Builtin;
 use env_info::EnvInfo;
 use error::{BlockError, TransactionError, Error};
 use header::Header;
-use views::HeaderView;
 use state::CleanupMode;
 use spec::CommonParams;
 use transaction::UnverifiedTransaction;
@@ -29,7 +28,6 @@ use engines::Engine;
 use evm::Schedule;
 use ethjson;
 use rlp::{self, UntrustedRlp, View};
-use blockchain::extras::BlockDetails;
 
 /// Parity tries to round block.gas_limit to multiple of this constant
 pub const PARITY_GAS_LIMIT_DETERMINANT: U256 = U256([37, 0, 0, 0]);
@@ -335,15 +333,6 @@ impl Engine for Ethash {
 
 		Ok(())
 	}
-
-	fn is_new_best_block(&self, best_total_difficulty: U256, _best_header: HeaderView, parent_details: &BlockDetails, new_header: &HeaderView) -> bool {
-		is_new_best_block(best_total_difficulty, parent_details, new_header)
-	}
-}
-
-/// Check if a new block should replace the best blockchain block.
-pub fn is_new_best_block(best_total_difficulty: U256, parent_details: &BlockDetails, new_header: &HeaderView) -> bool {
-	parent_details.total_difficulty + new_header.difficulty() > best_total_difficulty
 }
 
 // Try to round gas_limit a bit so that:

ethcore/src/snapshot/service.rs

@@ -81,7 +81,6 @@ struct Restoration {
 struct RestorationParams<'a> {
 	manifest: ManifestData, // manifest to base restoration on.
 	pruning: Algorithm, // pruning algorithm for the database.
-	engine: Arc<Engine>, // consensus engine of the chain.
 	db_path: PathBuf, // database path
 	db_config: &'a DatabaseConfig, // configuration for the database.
 	writer: Option<LooseWriter>, // writer for recovered snapshot.
@@ -100,7 +99,7 @@ impl Restoration {
 		let raw_db = Arc::new(Database::open(params.db_config, &*params.db_path.to_string_lossy())
 			.map_err(UtilError::SimpleString)?);
 
-		let chain = BlockChain::new(Default::default(), params.genesis, raw_db.clone(), params.engine);
+		let chain = BlockChain::new(Default::default(), params.genesis, raw_db.clone());
 		let blocks = BlockRebuilder::new(chain, raw_db.clone(), &manifest)?;
 
 		let root = manifest.state_root.clone();
@@ -421,7 +420,6 @@ impl Service {
 		let params = RestorationParams {
 			manifest: manifest,
 			pruning: self.pruning,
-			engine: self.engine.clone(),
 			db_path: self.restoration_db(),
 			db_config: &self.db_config,
 			writer: writer,

ethcore/src/snapshot/tests/blocks.rs

@@ -44,7 +44,7 @@ fn chunk_and_restore(amount: u64) {
 	snapshot_path.push("SNAP");
 
 	let old_db = Arc::new(Database::open(&db_cfg, orig_path.as_str()).unwrap());
-	let bc = BlockChain::new(Default::default(), &genesis, old_db.clone(), engine.clone());
+	let bc = BlockChain::new(Default::default(), &genesis, old_db.clone());
 
 	// build the blockchain.
 	let mut batch = old_db.transaction();
@@ -74,7 +74,7 @@ fn chunk_and_restore(amount: u64) {
 
 	// restore it.
 	let new_db = Arc::new(Database::open(&db_cfg, new_path.as_str()).unwrap());
-	let new_chain = BlockChain::new(Default::default(), &genesis, new_db.clone(), engine.clone());
+	let new_chain = BlockChain::new(Default::default(), &genesis, new_db.clone());
 	let mut rebuilder = BlockRebuilder::new(new_chain, new_db.clone(), &manifest).unwrap();
 	let reader = PackedReader::new(&snapshot_path).unwrap().unwrap();
 	let flag = AtomicBool::new(true);
@@ -87,7 +87,7 @@ fn chunk_and_restore(amount: u64) {
 	rebuilder.finalize(HashMap::new()).unwrap();
 
 	// and test it.
-	let new_chain = BlockChain::new(Default::default(), &genesis, new_db, engine);
+	let new_chain = BlockChain::new(Default::default(), &genesis, new_db);
 	assert_eq!(new_chain.best_block_hash(), best_hash);
 }
 
@@ -122,7 +122,7 @@ fn checks_flag() {
 	let db_cfg = DatabaseConfig::with_columns(::db::NUM_COLUMNS);
 	let db = Arc::new(Database::open(&db_cfg, path.as_str()).unwrap());
 	let engine = Arc::new(::engines::NullEngine::default());
-	let chain = BlockChain::new(Default::default(), &genesis, db.clone(), engine.clone());
+	let chain = BlockChain::new(Default::default(), &genesis, db.clone());
 
 	let manifest = ::snapshot::ManifestData {
 		state_hashes: Vec::new(),

ethcore/src/tests/helpers.rs

@@ -294,7 +294,7 @@ fn new_db(path: &str) -> Arc<Database> {
 pub fn generate_dummy_blockchain(block_number: u32) -> GuardedTempResult<BlockChain> {
 	let temp = RandomTempPath::new();
 	let db = new_db(temp.as_str());
-	let bc = BlockChain::new(BlockChainConfig::default(), &create_unverifiable_block(0, H256::zero()), db.clone(), Spec::new_null().engine);
+	let bc = BlockChain::new(BlockChainConfig::default(), &create_unverifiable_block(0, H256::zero()), db.clone());
 
 	let mut batch = db.transaction();
 	for block_order in 1..block_number {
@@ -312,7 +312,7 @@ pub fn generate_dummy_blockchain(block_number: u32) -> GuardedTempResult<BlockCh
 pub fn generate_dummy_blockchain_with_extra(block_number: u32) -> GuardedTempResult<BlockChain> {
 	let temp = RandomTempPath::new();
 	let db = new_db(temp.as_str());
-	let bc = BlockChain::new(BlockChainConfig::default(), &create_unverifiable_block(0, H256::zero()), db.clone(), Spec::new_null().engine);
+	let bc = BlockChain::new(BlockChainConfig::default(), &create_unverifiable_block(0, H256::zero()), db.clone());
 
 
 	let mut batch = db.transaction();
@@ -331,7 +331,7 @@ pub fn generate_dummy_blockchain_with_extra(block_number: u32) -> GuardedTempRes
 pub fn generate_dummy_empty_blockchain() -> GuardedTempResult<BlockChain> {
 	let temp = RandomTempPath::new();
 	let db = new_db(temp.as_str());
-	let bc = BlockChain::new(BlockChainConfig::default(), &create_unverifiable_block(0, H256::zero()), db.clone(), Spec::new_null().engine);
+	let bc = BlockChain::new(BlockChainConfig::default(), &create_unverifiable_block(0, H256::zero()), db.clone());
 
 	GuardedTempResult::<BlockChain> {
 		_temp: temp,