Merge pull request #3426 from ethcore/auth-round

Authority round consensus engine

ethcore/res/authority_round.json

@@ -0,0 +1,42 @@
+{
+	"name": "TestAuthorityRound",
+	"engine": {
+		"AuthorityRound": {
+			"params": {
+				"gasLimitBoundDivisor": "0x0400",
+				"stepDuration": "1",
+				"authorities" : [
+					"0x7d577a597b2742b498cb5cf0c26cdcd726d39e6e",
+					"0x82a978b3f5962a5b0957d9ee9eef472ee55b42f1"
+				]
+			}
+		}
+	},
+	"params": {
+		"accountStartNonce": "0x0",
+		"maximumExtraDataSize": "0x20",
+		"minGasLimit": "0x1388",
+		"networkID" : "0x69"
+	},
+	"genesis": {
+		"seal": {
+			"generic": {
+				"fields": 1,
+				"rlp": "0x11bbe8db4e347b4e8c937c1c8370e4b5ed33adb3db69cbdb7a38e1e50b1b82fa"
+			}
+		},
+		"difficulty": "0x20000",
+		"author": "0x0000000000000000000000000000000000000000",
+		"timestamp": "0x00",
+		"parentHash": "0x0000000000000000000000000000000000000000000000000000000000000000",
+		"extraData": "0x",
+		"gasLimit": "0x2fefd8"
+	},
+	"accounts": {
+		"0000000000000000000000000000000000000001": { "balance": "1", "nonce": "1048576", "builtin": { "name": "ecrecover", "pricing": { "linear": { "base": 3000, "word": 0 } } } },
+		"0000000000000000000000000000000000000002": { "balance": "1", "nonce": "1048576", "builtin": { "name": "sha256", "pricing": { "linear": { "base": 60, "word": 12 } } } },
+		"0000000000000000000000000000000000000003": { "balance": "1", "nonce": "1048576", "builtin": { "name": "ripemd160", "pricing": { "linear": { "base": 600, "word": 120 } } } },
+		"0000000000000000000000000000000000000004": { "balance": "1", "nonce": "1048576", "builtin": { "name": "identity", "pricing": { "linear": { "base": 15, "word": 3 } } } },
+		"9cce34f7ab185c7aba1b7c8140d620b4bda941d6": { "balance": "1606938044258990275541962092341162602522202993782792835301376", "nonce": "1048576" }
+	}
+}

ethcore/res/basic_authority.json

@@ -1,5 +1,5 @@
 {
-	"name": "TestAuthority",
+	"name": "TestBasicAuthority",
 	"engine": {
 		"BasicAuthority": {
 			"params": {

ethcore/src/client/client.rs

@@ -554,6 +554,7 @@ impl Client {
 
 	/// Import transactions from the IO queue
 	pub fn import_queued_transactions(&self, transactions: &[Bytes]) -> usize {
+		trace!(target: "external_tx", "Importing queued");
 		let _timer = PerfTimer::new("import_queued_transactions");
 		self.queue_transactions.fetch_sub(transactions.len(), AtomicOrdering::SeqCst);
 		let txs = transactions.iter().filter_map(|bytes| UntrustedRlp::new(bytes).as_val().ok()).collect();
@@ -561,6 +562,11 @@ impl Client {
 		results.len()
 	}
 
+	/// Used by PoA to try sealing on period change.
+	pub fn update_sealing(&self) {
+		self.miner.update_sealing(self)
+	}
+
 	/// Attempt to get a copy of a specific block's final state.
 	///
 	/// This will not fail if given BlockID::Latest.
@@ -1193,7 +1199,9 @@ impl BlockChainClient for Client {
 	}
 
 	fn queue_transactions(&self, transactions: Vec<Bytes>) {
-		if self.queue_transactions.load(AtomicOrdering::Relaxed) > MAX_TX_QUEUE_SIZE {
+		let queue_size = self.queue_transactions.load(AtomicOrdering::Relaxed);
+		trace!(target: "external_tx", "Queue size: {}", queue_size);
+		if queue_size > MAX_TX_QUEUE_SIZE {
 			debug!("Ignoring {} transactions: queue is full", transactions.len());
 		} else {
 			let len = transactions.len();

ethcore/src/client/test_client.rs

@@ -119,6 +119,16 @@ impl TestBlockChainClient {
 	/// Creates new test client with specified extra data for each block
 	pub fn new_with_extra_data(extra_data: Bytes) -> Self {
 		let spec = Spec::new_test();
+		TestBlockChainClient::new_with_spec_and_extra(spec, extra_data)
+	}
+
+	/// Create test client with custom spec.
+	pub fn new_with_spec(spec: Spec) -> Self {
+		TestBlockChainClient::new_with_spec_and_extra(spec, Bytes::new())
+	}
+
+	/// Create test client with custom spec and extra data.
+	pub fn new_with_spec_and_extra(spec: Spec, extra_data: Bytes) -> Self {
 		let mut client = TestBlockChainClient {
 			blocks: RwLock::new(HashMap::new()),
 			numbers: RwLock::new(HashMap::new()),

ethcore/src/engines/authority_round.rs

@@ -0,0 +1,429 @@
+// Copyright 2015, 2016 Ethcore (UK) Ltd.
+// This file is part of Parity.
+
+// Parity 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.
+
+// Parity 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 Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+//! A blockchain engine that supports a non-instant BFT proof-of-authority.
+
+use std::sync::atomic::{AtomicUsize, AtomicBool, Ordering as AtomicOrdering};
+use std::sync::Weak;
+use std::time::{UNIX_EPOCH, Duration};
+use util::*;
+use ethkey::{verify_address, Signature};
+use rlp::{UntrustedRlp, View, encode};
+use account_provider::AccountProvider;
+use block::*;
+use spec::CommonParams;
+use engines::Engine;
+use header::Header;
+use error::{Error, BlockError};
+use evm::Schedule;
+use ethjson;
+use io::{IoContext, IoHandler, TimerToken, IoService, IoChannel};
+use service::ClientIoMessage;
+use transaction::SignedTransaction;
+use env_info::EnvInfo;
+use builtin::Builtin;
+
+/// `AuthorityRound` params.
+#[derive(Debug, PartialEq)]
+pub struct AuthorityRoundParams {
+	/// Gas limit divisor.
+	pub gas_limit_bound_divisor: U256,
+	/// Time to wait before next block or authority switching.
+	pub step_duration: Duration,
+	/// Valid authorities.
+	pub authorities: Vec<Address>,
+	/// Number of authorities.
+	pub authority_n: usize,
+}
+
+impl From<ethjson::spec::AuthorityRoundParams> for AuthorityRoundParams {
+	fn from(p: ethjson::spec::AuthorityRoundParams) -> Self {
+		AuthorityRoundParams {
+			gas_limit_bound_divisor: p.gas_limit_bound_divisor.into(),
+			step_duration: Duration::from_secs(p.step_duration.into()),
+			authority_n: p.authorities.len(),
+			authorities: p.authorities.into_iter().map(Into::into).collect::<Vec<_>>(),
+		}
+	}
+}
+
+/// Engine using `AuthorityRound` proof-of-work consensus algorithm, suitable for Ethereum
+/// mainnet chains in the Olympic, Frontier and Homestead eras.
+pub struct AuthorityRound {
+	params: CommonParams,
+	our_params: AuthorityRoundParams,
+	builtins: BTreeMap<Address, Builtin>,
+	transition_service: IoService<BlockArrived>,
+	message_channel: Mutex<Option<IoChannel<ClientIoMessage>>>,
+	step: AtomicUsize,
+	proposed: AtomicBool,
+}
+
+fn header_step(header: &Header) -> Result<usize, ::rlp::DecoderError> {
+	UntrustedRlp::new(&header.seal()[0]).as_val()
+}
+
+fn header_signature(header: &Header) -> Result<Signature, ::rlp::DecoderError> {
+	UntrustedRlp::new(&header.seal()[1]).as_val::<H520>().map(Into::into)
+}
+
+trait AsMillis {
+	fn as_millis(&self) -> u64;
+}
+
+impl AsMillis for Duration {
+	fn as_millis(&self) -> u64 {
+		self.as_secs()*1_000 + (self.subsec_nanos()/1_000_000) as u64
+	}
+}
+
+impl AuthorityRound {
+	/// Create a new instance of AuthorityRound engine.
+	pub fn new(params: CommonParams, our_params: AuthorityRoundParams, builtins: BTreeMap<Address, Builtin>) -> Result<Arc<Self>, Error> {
+		let initial_step = (unix_now().as_secs() / our_params.step_duration.as_secs()) as usize;
+		let engine = Arc::new(
+			AuthorityRound {
+				params: params,
+				our_params: our_params,
+				builtins: builtins,
+				transition_service: try!(IoService::<BlockArrived>::start()),
+				message_channel: Mutex::new(None),
+				step: AtomicUsize::new(initial_step),
+				proposed: AtomicBool::new(false)
+			});
+		let handler = TransitionHandler { engine: Arc::downgrade(&engine) };
+		try!(engine.transition_service.register_handler(Arc::new(handler)));
+		Ok(engine)
+	}
+
+	fn step(&self) -> usize {
+		self.step.load(AtomicOrdering::SeqCst)
+	}
+
+	fn remaining_step_duration(&self) -> Duration {
+		let now = unix_now();
+		let step_end = self.our_params.step_duration * (self.step() as u32 + 1);
+		if step_end > now {
+			step_end - now
+		} else {
+			Duration::from_secs(0)
+		}
+	}
+
+	fn step_proposer(&self, step: usize) -> &Address {
+		let ref p = self.our_params;
+		p.authorities.get(step % p.authority_n).expect("There are authority_n authorities; taking number modulo authority_n gives number in authority_n range; qed")
+	}
+
+	fn is_step_proposer(&self, step: usize, address: &Address) -> bool {
+		self.step_proposer(step) == address
+	}
+}
+
+fn unix_now() -> Duration {
+	UNIX_EPOCH.elapsed().expect("Valid time has to be set in your system.")
+}
+
+struct TransitionHandler {
+	engine: Weak<AuthorityRound>,
+}
+
+#[derive(Clone)]
+struct BlockArrived;
+
+const ENGINE_TIMEOUT_TOKEN: TimerToken = 23;
+
+impl IoHandler<BlockArrived> for TransitionHandler {
+	fn initialize(&self, io: &IoContext<BlockArrived>) {
+		if let Some(engine) = self.engine.upgrade() {
+			io.register_timer_once(ENGINE_TIMEOUT_TOKEN, engine.remaining_step_duration().as_millis())
+				.unwrap_or_else(|e| warn!(target: "poa", "Failed to start consensus step timer: {}.", e))
+		}
+	}
+
+	fn timeout(&self, io: &IoContext<BlockArrived>, timer: TimerToken) {
+		if timer == ENGINE_TIMEOUT_TOKEN {
+			if let Some(engine) = self.engine.upgrade() {
+				engine.step.fetch_add(1, AtomicOrdering::SeqCst);
+				engine.proposed.store(false, AtomicOrdering::SeqCst);
+				if let Some(ref channel) = *engine.message_channel.lock() {
+					match channel.send(ClientIoMessage::UpdateSealing) {
+						Ok(_) => trace!(target: "poa", "timeout: UpdateSealing message sent for step {}.", engine.step.load(AtomicOrdering::Relaxed)),
+						Err(err) => trace!(target: "poa", "timeout: Could not send a sealing message {} for step {}.", err, engine.step.load(AtomicOrdering::Relaxed)),
+					}
+				}
+				io.register_timer_once(ENGINE_TIMEOUT_TOKEN, engine.remaining_step_duration().as_millis())
+					.unwrap_or_else(|e| warn!(target: "poa", "Failed to restart consensus step timer: {}.", e))
+			}
+		}
+	}
+}
+
+impl Engine for AuthorityRound {
+	fn name(&self) -> &str { "AuthorityRound" }
+	fn version(&self) -> SemanticVersion { SemanticVersion::new(1, 0, 0) }
+	/// Two fields - consensus step and the corresponding proposer signature.
+	fn seal_fields(&self) -> usize { 2 }
+
+	fn params(&self) -> &CommonParams { &self.params }
+	fn builtins(&self) -> &BTreeMap<Address, Builtin> { &self.builtins }
+
+	/// Additional engine-specific information for the user/developer concerning `header`.
+	fn extra_info(&self, header: &Header) -> BTreeMap<String, String> {
+		map![
+			"step".into() => header_step(header).as_ref().map(ToString::to_string).unwrap_or("".into()),
+			"signature".into() => header_signature(header).as_ref().map(ToString::to_string).unwrap_or("".into())
+		]
+	}
+
+	fn schedule(&self, _env_info: &EnvInfo) -> Schedule {
+		Schedule::new_post_eip150(true, true, true)
+	}
+
+	fn populate_from_parent(&self, header: &mut Header, parent: &Header, gas_floor_target: U256, _gas_ceil_target: U256) {
+		header.set_difficulty(parent.difficulty().clone());
+		header.set_gas_limit({
+			let gas_limit = parent.gas_limit().clone();
+			let bound_divisor = self.our_params.gas_limit_bound_divisor;
+			if gas_limit < gas_floor_target {
+				min(gas_floor_target, gas_limit + gas_limit / bound_divisor - 1.into())
+			} else {
+				max(gas_floor_target, gas_limit - gas_limit / bound_divisor + 1.into())
+			}
+		});
+	}
+
+	/// Apply the block reward on finalisation of the block.
+	/// This assumes that all uncles are valid uncles (i.e. of at least one generation before the current).
+	fn on_close_block(&self, _block: &mut ExecutedBlock) {}
+
+	fn is_sealer(&self, author: &Address) -> Option<bool> {
+		let ref p = self.our_params;
+		Some(p.authorities.contains(author))
+	}
+
+	/// Attempt to seal the block internally.
+	///
+	/// This operation is synchronous and may (quite reasonably) not be available, in which `false` will
+	/// be returned.
+	fn generate_seal(&self, block: &ExecutedBlock, accounts: Option<&AccountProvider>) -> Option<Vec<Bytes>> {
+		if self.proposed.load(AtomicOrdering::SeqCst) { return None; }
+		let header = block.header();
+		let step = self.step();
+		if self.is_step_proposer(step, header.author()) {
+			if let Some(ap) = accounts {
+				// Account should be permanently unlocked, otherwise sealing will fail.
+				if let Ok(signature) = ap.sign(*header.author(), None, header.bare_hash()) {
+					trace!(target: "poa", "generate_seal: Issuing a block for step {}.", step);
+					self.proposed.store(true, AtomicOrdering::SeqCst);
+					return Some(vec![encode(&step).to_vec(), encode(&(&*signature as &[u8])).to_vec()]);
+				} else {
+					warn!(target: "poa", "generate_seal: FAIL: Accounts secret key unavailable.");
+				}
+			} else {
+				warn!(target: "poa", "generate_seal: FAIL: Accounts not provided.");
+			}
+		}
+		None
+	}
+
+	/// Check the number of seal fields.
+	fn verify_block_basic(&self, header: &Header, _block: Option<&[u8]>) -> Result<(), Error> {
+		if header.seal().len() != self.seal_fields() {
+			trace!(target: "poa", "verify_block_basic: wrong number of seal fields");
+			Err(From::from(BlockError::InvalidSealArity(
+				Mismatch { expected: self.seal_fields(), found: header.seal().len() }
+			)))
+		} else {
+			Ok(())
+		}
+	}
+
+	/// Check if the signature belongs to the correct proposer.
+	fn verify_block_unordered(&self, header: &Header, _block: Option<&[u8]>) -> Result<(), Error> {
+        let header_step = try!(header_step(header));
+        // Give one step slack if step is lagging, double vote is still not possible.
+		if header_step <= self.step() + 1 {
+			let proposer_signature = try!(header_signature(header));
+			let ok_sig = try!(verify_address(self.step_proposer(header_step), &proposer_signature, &header.bare_hash()));
+			if ok_sig {
+				Ok(())
+			} else {
+				trace!(target: "poa", "verify_block_unordered: invalid seal signature");
+				try!(Err(BlockError::InvalidSeal))
+			}
+		} else {
+			trace!(target: "poa", "verify_block_unordered: block from the future");
+			try!(Err(BlockError::InvalidSeal))
+		}
+	}
+
+	fn verify_block_family(&self, header: &Header, parent: &Header, _block: Option<&[u8]>) -> Result<(), Error> {
+		// Don't calculate difficulty for genesis blocks.
+		if header.number() == 0 {
+			return Err(From::from(BlockError::RidiculousNumber(OutOfBounds { min: Some(1), max: None, found: header.number() })));
+		}
+
+		let step = try!(header_step(header));
+		// Check if parent is from a previous step.
+		if step == try!(header_step(parent)) { 
+			trace!(target: "poa", "Multiple blocks proposed for step {}.", step);
+			try!(Err(BlockError::DoubleVote(header.author().clone())));
+		}
+
+		// Check difficulty is correct given the two timestamps.
+		if header.difficulty() != parent.difficulty() {
+			return Err(From::from(BlockError::InvalidDifficulty(Mismatch { expected: *parent.difficulty(), found: *header.difficulty() })))
+		}
+		let gas_limit_divisor = self.our_params.gas_limit_bound_divisor;
+		let min_gas = parent.gas_limit().clone() - parent.gas_limit().clone() / gas_limit_divisor;
+		let max_gas = parent.gas_limit().clone() + parent.gas_limit().clone() / gas_limit_divisor;
+		if header.gas_limit() <= &min_gas || header.gas_limit() >= &max_gas {
+			return Err(From::from(BlockError::InvalidGasLimit(OutOfBounds { min: Some(min_gas), max: Some(max_gas), found: header.gas_limit().clone() })));
+		}
+		Ok(())
+	}
+
+	fn verify_transaction_basic(&self, t: &SignedTransaction, _header: &Header) -> Result<(), Error> {
+		try!(t.check_low_s());
+		Ok(())
+	}
+
+	fn verify_transaction(&self, t: &SignedTransaction, _header: &Header) -> Result<(), Error> {
+		t.sender().map(|_|()) // Perform EC recovery and cache sender
+	}
+
+	fn register_message_channel(&self, message_channel: IoChannel<ClientIoMessage>) {
+		let mut guard = self.message_channel.lock();
+		*guard = Some(message_channel);
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	use util::*;
+	use env_info::EnvInfo;
+	use header::Header;
+	use error::{Error, BlockError};
+	use rlp::encode;
+	use block::*;
+	use tests::helpers::*;
+	use account_provider::AccountProvider;
+	use spec::Spec;
+	use std::time::UNIX_EPOCH;
+
+	#[test]
+	fn has_valid_metadata() {
+		let engine = Spec::new_test_round().engine;
+		assert!(!engine.name().is_empty());
+		assert!(engine.version().major >= 1);
+	}
+
+	#[test]
+	fn can_return_schedule() {
+		let engine = Spec::new_test_round().engine;
+		let schedule = engine.schedule(&EnvInfo {
+			number: 10000000,
+			author: 0.into(),
+			timestamp: 0,
+			difficulty: 0.into(),
+			last_hashes: Arc::new(vec![]),
+			gas_used: 0.into(),
+			gas_limit: 0.into(),
+		});
+
+		assert!(schedule.stack_limit > 0);
+	}
+
+	#[test]
+	fn verification_fails_on_short_seal() {
+		let engine = Spec::new_test_round().engine;
+		let header: Header = Header::default();
+
+		let verify_result = engine.verify_block_basic(&header, None);
+
+		match verify_result {
+			Err(Error::Block(BlockError::InvalidSealArity(_))) => {},
+			Err(_) => { panic!("should be block seal-arity mismatch error (got {:?})", verify_result); },
+			_ => { panic!("Should be error, got Ok"); },
+		}
+	}
+
+	#[test]
+	fn can_do_signature_verification_fail() {
+		let engine = Spec::new_test_round().engine;
+		let mut header: Header = Header::default();
+		header.set_seal(vec![encode(&H520::default()).to_vec()]);
+
+		let verify_result = engine.verify_block_unordered(&header, None);
+		assert!(verify_result.is_err());
+	}
+
+	#[test]
+	fn generates_seal_and_does_not_double_propose() {
+		let tap = AccountProvider::transient_provider();
+		let addr1 = tap.insert_account("1".sha3(), "1").unwrap();
+		tap.unlock_account_permanently(addr1, "1".into()).unwrap();
+		let addr2 = tap.insert_account("2".sha3(), "2").unwrap();
+		tap.unlock_account_permanently(addr2, "2".into()).unwrap();
+
+		let spec = Spec::new_test_round();
+		let engine = &*spec.engine;
+		let genesis_header = spec.genesis_header();
+		let mut db1 = get_temp_state_db().take();
+		spec.ensure_db_good(&mut db1).unwrap();
+		let mut db2 = get_temp_state_db().take();
+		spec.ensure_db_good(&mut db2).unwrap();
+		let last_hashes = Arc::new(vec![genesis_header.hash()]);
+		let b1 = OpenBlock::new(engine, Default::default(), false, db1, &genesis_header, last_hashes.clone(), addr1, (3141562.into(), 31415620.into()), vec![]).unwrap();
+		let b1 = b1.close_and_lock();
+		let b2 = OpenBlock::new(engine, Default::default(), false, db2, &genesis_header, last_hashes, addr2, (3141562.into(), 31415620.into()), vec![]).unwrap();
+		let b2 = b2.close_and_lock();
+
+		if let Some(seal) = engine.generate_seal(b1.block(), Some(&tap)) {
+			assert!(b1.clone().try_seal(engine, seal).is_ok());
+			// Second proposal is forbidden.
+			assert!(engine.generate_seal(b1.block(), Some(&tap)).is_none());
+		}
+
+		if let Some(seal) = engine.generate_seal(b2.block(), Some(&tap)) {
+			assert!(b2.clone().try_seal(engine, seal).is_ok());
+			// Second proposal is forbidden.
+			assert!(engine.generate_seal(b2.block(), Some(&tap)).is_none());
+		}
+	}
+
+	#[test]
+	fn proposer_switching() {
+		let mut header: Header = Header::default();
+		let tap = AccountProvider::transient_provider();
+		let addr = tap.insert_account("0".sha3(), "0").unwrap();
+
+		header.set_author(addr);
+
+		let engine = Spec::new_test_round().engine;
+
+		let signature = tap.sign(addr, Some("0".into()), header.bare_hash()).unwrap();
+		let mut step = UNIX_EPOCH.elapsed().unwrap().as_secs();
+		header.set_seal(vec![encode(&step).to_vec(), encode(&(&*signature as &[u8])).to_vec()]);
+		let first_ok = engine.verify_block_seal(&header).is_ok();
+		step = step + 1;
+		header.set_seal(vec![encode(&step).to_vec(), encode(&(&*signature as &[u8])).to_vec()]);
+		let second_ok = engine.verify_block_seal(&header).is_ok();
+
+		assert!(first_ok ^ second_ok);
+	}
+}

ethcore/src/engines/basic_authority.rs

@@ -181,13 +181,6 @@ impl Engine for BasicAuthority {
 	}
 }
 
-impl Header {
-	/// Get the none field of the header.
-	pub fn signature(&self) -> H520 {
-		::rlp::decode(&self.seal()[0])
-	}
-}
-
 #[cfg(test)]
 mod tests {
 	use util::*;
@@ -201,7 +194,7 @@ mod tests {
 
 	/// Create a new test chain spec with `BasicAuthority` consensus engine.
 	fn new_test_authority() -> Spec {
-		let bytes: &[u8] = include_bytes!("../../res/test_authority.json");
+		let bytes: &[u8] = include_bytes!("../../res/basic_authority.json");
 		Spec::load(bytes).expect("invalid chain spec")
 	}
 

ethcore/src/engines/mod.rs

@@ -19,10 +19,12 @@
 mod null_engine;
 mod instant_seal;
 mod basic_authority;
+mod authority_round;
 
 pub use self::null_engine::NullEngine;
 pub use self::instant_seal::InstantSeal;
 pub use self::basic_authority::BasicAuthority;
+pub use self::authority_round::AuthorityRound;
 
 use util::*;
 use account_provider::AccountProvider;
@@ -32,6 +34,8 @@ use env_info::EnvInfo;
 use error::Error;
 use spec::CommonParams;
 use evm::Schedule;
+use io::IoChannel;
+use service::ClientIoMessage;
 use header::Header;
 use transaction::SignedTransaction;
 
@@ -140,5 +144,7 @@ pub trait Engine : Sync + Send {
 		self.builtins().get(a).expect("attempted to execute nonexistent builtin").execute(input, output);
 	}
 
+	/// Add a channel for communication with Client which can be used for sealing.
+	fn register_message_channel(&self, _message_channel: IoChannel<ClientIoMessage>) {}
 	// TODO: sealing stuff - though might want to leave this for later.
 }

ethcore/src/error.rs

@@ -167,6 +167,8 @@ pub enum BlockError {
 	UnknownParent(H256),
 	/// Uncle parent given is unknown.
 	UnknownUncleParent(H256),
+	/// The same author issued different votes at the same step.
+	DoubleVote(H160),
 }
 
 impl fmt::Display for BlockError {
@@ -200,6 +202,7 @@ impl fmt::Display for BlockError {
 			RidiculousNumber(ref oob) => format!("Implausible block number. {}", oob),
 			UnknownParent(ref hash) => format!("Unknown parent: {}", hash),
 			UnknownUncleParent(ref hash) => format!("Unknown uncle parent: {}", hash),
+			DoubleVote(ref address) => format!("Author {} issued too many blocks.", address),
 		};
 
 		f.write_fmt(format_args!("Block error ({})", msg))

ethcore/src/miner/miner.rs

@@ -212,7 +212,8 @@ pub struct Miner {
 	sealing_block_last_request: Mutex<u64>,
 	// for sealing...
 	options: MinerOptions,
-	seals_internally: bool,
+	/// Does the node perform internal (without work) sealing.
+	pub seals_internally: bool,
 
 	gas_range_target: RwLock<(U256, U256)>,
 	author: RwLock<Address>,
@@ -267,6 +268,11 @@ impl Miner {
 		}
 	}
 
+	/// Creates new instance of miner with accounts and with given spec.
+	pub fn with_spec_and_accounts(spec: &Spec, accounts: Option<Arc<AccountProvider>>) -> Miner {
+		Miner::new_raw(Default::default(), GasPricer::new_fixed(20_000_000_000u64.into()), spec, accounts)
+	}
+
 	/// Creates new instance of miner without accounts, but with given spec.
 	pub fn with_spec(spec: &Spec) -> Miner {
 		Miner::new_raw(Default::default(), GasPricer::new_fixed(20_000_000_000u64.into()), spec, None)
@@ -429,6 +435,7 @@ impl Miner {
 			let last_request = *self.sealing_block_last_request.lock();
 			let should_disable_sealing = !self.forced_sealing()
 				&& !has_local_transactions
+				&& !self.seals_internally
 				&& best_block > last_request
 				&& best_block - last_request > SEALING_TIMEOUT_IN_BLOCKS;
 
@@ -472,9 +479,10 @@ impl Miner {
 
 	/// Uses Engine to seal the block internally and then imports it to chain.
 	fn seal_and_import_block_internally(&self, chain: &MiningBlockChainClient, block: ClosedBlock) -> bool {
-		if !block.transactions().is_empty() {
+		if !block.transactions().is_empty() || self.forced_sealing() {
 			if let Ok(sealed) = self.seal_block_internally(block) {
 				if chain.import_block(sealed.rlp_bytes()).is_ok() {
+					trace!(target: "miner", "import_block_internally: imported internally sealed block");
 					return true
 				}
 			}
@@ -773,7 +781,7 @@ impl MinerService for Miner {
 		chain: &MiningBlockChainClient,
 		transactions: Vec<SignedTransaction>
 	) -> Vec<Result<TransactionImportResult, Error>> {
-
+		trace!(target: "external_tx", "Importing external transactions");
 		let results = {
 			let mut transaction_queue = self.transaction_queue.lock();
 			self.add_transactions_to_queue(

ethcore/src/service.rs

@@ -48,6 +48,8 @@ pub enum ClientIoMessage {
 	FeedBlockChunk(H256, Bytes),
 	/// Take a snapshot for the block with given number.
 	TakeSnapshot(u64),
+	/// Trigger sealing update (useful for internal sealing).
+	UpdateSealing,
 }
 
 /// Client service setup. Creates and registers client and network services with the IO subsystem.
@@ -111,6 +113,8 @@ impl ClientService {
 		});
 		try!(io_service.register_handler(client_io));
 
+		spec.engine.register_message_channel(io_service.channel());
+
 		let stop_guard = ::devtools::StopGuard::new();
 		run_ipc(ipc_path, client.clone(), snapshot.clone(), stop_guard.share());
 
@@ -213,8 +217,11 @@ impl IoHandler<ClientIoMessage> for ClientIoHandler {
 				if let Err(e) = res {
 					debug!(target: "snapshot", "Failed to initialize periodic snapshot thread: {:?}", e);
 				}
-
-			}
+			},
+			ClientIoMessage::UpdateSealing => {
+				trace!(target: "authorityround", "message: UpdateSealing");
+				self.client.update_sealing()
+			},
 			_ => {} // ignore other messages
 		}
 	}

ethcore/src/spec/spec.rs

@@ -18,7 +18,7 @@
 
 use util::*;
 use builtin::Builtin;
-use engines::{Engine, NullEngine, InstantSeal, BasicAuthority};
+use engines::{Engine, NullEngine, InstantSeal, BasicAuthority, AuthorityRound};
 use pod_state::*;
 use account_db::*;
 use header::{BlockNumber, Header};
@@ -150,6 +150,7 @@ impl Spec {
 			ethjson::spec::Engine::InstantSeal => Arc::new(InstantSeal::new(params, builtins)),
 			ethjson::spec::Engine::Ethash(ethash) => Arc::new(ethereum::Ethash::new(params, From::from(ethash.params), builtins)),
 			ethjson::spec::Engine::BasicAuthority(basic_authority) => Arc::new(BasicAuthority::new(params, From::from(basic_authority.params), builtins)),
+			ethjson::spec::Engine::AuthorityRound(authority_round) => AuthorityRound::new(params, From::from(authority_round.params), builtins).expect("Consensus engine could not be started."),
 		}
 	}
 
@@ -280,6 +281,10 @@ impl Spec {
 
 	/// Create a new Spec with InstantSeal consensus which does internal sealing (not requiring work).
 	pub fn new_instant() -> Spec { load_bundled!("instant_seal") }
+
+	/// Create a new Spec with AuthorityRound consensus which does internal sealing (not requiring work).
+	/// Accounts with secrets "1".sha3() and "2".sha3() are the authorities.
+	pub fn new_test_round() -> Self { load_bundled!("authority_round") }
 }
 
 #[cfg(test)]

json/src/spec/authority_round.rs

@@ -0,0 +1,59 @@
+// Copyright 2015, 2016 Ethcore (UK) Ltd.
+// This file is part of Parity.
+
+// Parity 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.
+
+// Parity 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 Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Authority params deserialization.
+
+use uint::Uint;
+use hash::Address;
+
+/// Authority params deserialization.
+#[derive(Debug, PartialEq, Deserialize)]
+pub struct AuthorityRoundParams {
+	/// Gas limit divisor.
+	#[serde(rename="gasLimitBoundDivisor")]
+	pub gas_limit_bound_divisor: Uint,
+	/// Block duration.
+	#[serde(rename="stepDuration")]
+	pub step_duration: Uint,
+	/// Valid authorities
+	pub authorities: Vec<Address>,
+}
+
+/// Authority engine deserialization.
+#[derive(Debug, PartialEq, Deserialize)]
+pub struct AuthorityRound {
+	/// Ethash params.
+	pub params: AuthorityRoundParams,
+}
+
+#[cfg(test)]
+mod tests {
+	use serde_json;
+	use spec::authority_round::AuthorityRound;
+
+	#[test]
+	fn basic_authority_deserialization() {
+		let s = r#"{
+			"params": {
+				"gasLimitBoundDivisor": "0x0400",
+				"stepDuration": "0x02",
+				"authorities" : ["0xc6d9d2cd449a754c494264e1809c50e34d64562b"]
+			}
+		}"#;
+
+		let _deserialized: AuthorityRound = serde_json::from_str(s).unwrap();
+	}
+}

json/src/spec/engine.rs

@@ -18,6 +18,7 @@
 
 use spec::Ethash;
 use spec::BasicAuthority;
+use spec::AuthorityRound;
 
 /// Engine deserialization.
 #[derive(Debug, PartialEq, Deserialize)]
@@ -30,6 +31,8 @@ pub enum Engine {
 	Ethash(Ethash),
 	/// BasicAuthority engine.
 	BasicAuthority(BasicAuthority),
+	/// AuthorityRound engine.
+	AuthorityRound(AuthorityRound),
 }
 
 #[cfg(test)]

json/src/spec/mod.rs

@@ -26,6 +26,7 @@ pub mod engine;
 pub mod state;
 pub mod ethash;
 pub mod basic_authority;
+pub mod authority_round;
 
 pub use self::account::Account;
 pub use self::builtin::{Builtin, Pricing, Linear};
@@ -37,3 +38,4 @@ pub use self::engine::Engine;
 pub use self::state::State;
 pub use self::ethash::{Ethash, EthashParams};
 pub use self::basic_authority::{BasicAuthority, BasicAuthorityParams};
+pub use self::authority_round::{AuthorityRound, AuthorityRoundParams};

util/io/src/service.rs

@@ -56,6 +56,7 @@ pub enum IoMessage<Message> where Message: Send + Clone + Sized {
 		handler_id: HandlerId,
 		token: TimerToken,
 		delay: u64,
+		once: bool,
 	},
 	RemoveTimer {
 		handler_id: HandlerId,
@@ -92,12 +93,24 @@ impl<Message> IoContext<Message> where Message: Send + Clone + Sync + 'static {
 		}
 	}
 
-	/// Register a new IO timer. 'IoHandler::timeout' will be called with the token.
+	/// Register a new recurring IO timer. 'IoHandler::timeout' will be called with the token.
 	pub fn register_timer(&self, token: TimerToken, ms: u64) -> Result<(), IoError> {
 		try!(self.channel.send_io(IoMessage::AddTimer {
 			token: token,
 			delay: ms,
 			handler_id: self.handler,
+			once: false,
+		}));
+		Ok(())
+	}
+
+	/// Register a new IO timer once. 'IoHandler::timeout' will be called with the token.
+	pub fn register_timer_once(&self, token: TimerToken, ms: u64) -> Result<(), IoError> {
+		try!(self.channel.send_io(IoMessage::AddTimer {
+			token: token,
+			delay: ms,
+			handler_id: self.handler,
+			once: true,
 		}));
 		Ok(())
 	}
@@ -163,6 +176,7 @@ impl<Message> IoContext<Message> where Message: Send + Clone + Sync + 'static {
 struct UserTimer {
 	delay: u64,
 	timeout: Timeout,
+	once: bool,
 }
 
 /// Root IO handler. Manages user handlers, messages and IO timers.
@@ -235,8 +249,14 @@ impl<Message> Handler for IoManager<Message> where Message: Send + Clone + Sync
 		let handler_index  = token.0  / TOKENS_PER_HANDLER;
 		let token_id  = token.0  % TOKENS_PER_HANDLER;
 		if let Some(handler) = self.handlers.read().get(handler_index) {
-			if let Some(timer) = self.timers.read().get(&token.0) {
-				event_loop.timeout(token, Duration::from_millis(timer.delay)).expect("Error re-registering user timer");
+			let maybe_timer = self.timers.read().get(&token.0).cloned();
+			if let Some(timer) = maybe_timer {
+				if timer.once {
+					self.timers.write().remove(&token_id);
+					event_loop.clear_timeout(&timer.timeout);
+				} else {
+					event_loop.timeout(token, Duration::from_millis(timer.delay)).expect("Error re-registering user timer");
+				}
 				self.worker_channel.push(Work { work_type: WorkType::Timeout, token: token_id, handler: handler.clone(), handler_id: handler_index });
 				self.work_ready.notify_all();
 			}
@@ -264,10 +284,10 @@ impl<Message> Handler for IoManager<Message> where Message: Send + Clone + Sync
 					event_loop.clear_timeout(&timer.timeout);
 				}
 			},
-			IoMessage::AddTimer { handler_id, token, delay } => {
+			IoMessage::AddTimer { handler_id, token, delay, once } => {
 				let timer_id = token + handler_id * TOKENS_PER_HANDLER;
 				let timeout = event_loop.timeout(Token(timer_id), Duration::from_millis(delay)).expect("Error registering user timer");
-				self.timers.write().insert(timer_id, UserTimer { delay: delay, timeout: timeout });
+				self.timers.write().insert(timer_id, UserTimer { delay: delay, timeout: timeout, once: once });
 			},
 			IoMessage::RemoveTimer { handler_id, token } => {
 				let timer_id = token + handler_id * TOKENS_PER_HANDLER;