Beta: 1.11.6 backports (#9015)

* parity-version: bump beta to 1.11.6 * scripts: remove md5 checksums (#8884) * Add support for --chain tobalaba * Convert indents to tabs :) * Fixes for misbehavior reporting in AuthorityRound (#8998) * aura: only report after checking for repeated skipped primaries * aura: refactor duplicate code for getting epoch validator set * aura: verify_external: report on validator set contract instance * aura: use correct validator set epoch number when reporting * aura: use epoch set when verifying blocks * aura: report skipped primaries when generating seal * aura: handle immediate transitions * aura: don't report skipped steps from genesis to first block * aura: fix reporting test * aura: refactor duplicate code to handle immediate_transitions * aura: let reporting fail on verify_block_basic * aura: add comment about possible failure of reporting * Only return error log for rustls (#9025) * Transaction Pool improvements (#8470) * Don't use ethereum_types in transaction pool. * Hide internal insertion_id. * Fix tests. * Review grumbles. * Improve should_replace on NonceAndGasPrice (#8980) * Additional tests for NonceAndGasPrice::should_replace. * Fix should_replace in the distinct sender case. * Use natural priority ordering to simplify should_replace. * Minimal effective gas price in the queue (#8934) * Minimal effective gas price. * Fix naming, add test * Fix minimal entry score and add test. * Fix worst_transaction. * Remove effective gas price threshold. * Don't leak gas_price decisions out of Scoring. * Never drop local transactions from different senders. (#9002) * Recently rejected cache for transaction queue (#9005) * Store recently rejected transactions. * Don't cache AlreadyImported rejections. * Make the size of transaction verification queue dependent on pool size. * Add a test for recently rejected. * Fix logging for recently rejected. * Make rejection cache smaller. * obsolete test removed * obsolete test removed * Construct cache with_capacity. * Optimize pending transactions filter (#9026) * rpc: return unordered transactions in pending transactions filter * ethcore: use LruCache for nonce cache Only clear the nonce cache when a block is retracted * Revert "ethcore: use LruCache for nonce cache" This reverts commit b382c19abdb9985be1724c3b8cde83906da07d68. * Use only cached nonces when computing pending hashes. * Give filters their own locks, so that they don't block one another. * Fix pending transaction count if not sealing. * Clear cache only when block is enacted. * Fix RPC tests. * Address review comments. * A last bunch of txqueue performance optimizations (#9024) * Clear cache only when block is enacted. * Add tracing for cull. * Cull split. * Cull after creating pending block. * Add constant, remove sync::read tracing. * Reset debug. * Remove excessive tracing. * Use struct for NonceCache. * Fix build * Remove warnings. * Fix build again. * miner: add missing macro use for trace_time * ci: remove md5 merge leftovers
2018-07-09 08:39:46 +02:00 · 2018-07-09 08:39:46 +02:00 · 4ba600fcc4
commit 4ba600fcc4
parent 0487c5b7a7
52 changed files with 1356 additions and 581 deletions
--- a/Cargo.lock
+++ b/Cargo.lock
@ -1963,7 +1963,7 @@ dependencies = [

 [[package]]
 name = "parity"
-version = "1.11.5"
+version = "1.11.6"
 dependencies = [
 "ansi_term 0.10.2 (registry+https://github.com/rust-lang/crates.io-index)",
 "atty 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
@ -2014,7 +2014,7 @@ dependencies = [
 "parity-rpc 1.11.0",
 "parity-rpc-client 1.4.0",
 "parity-updater 1.11.0",
- "parity-version 1.11.5",
+ "parity-version 1.11.6",
 "parity-whisper 0.1.0",
 "parking_lot 0.5.4 (registry+https://github.com/rust-lang/crates.io-index)",
 "path 0.1.0",
@ -2062,7 +2062,7 @@ dependencies = [
 "parity-reactor 0.1.0",
 "parity-ui 1.11.0",
 "parity-ui-deprecation 1.10.0",
- "parity-version 1.11.5",
+ "parity-version 1.11.6",
 "parking_lot 0.5.4 (registry+https://github.com/rust-lang/crates.io-index)",
 "rand 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
 "registrar 0.0.1",
@ -2204,7 +2204,7 @@ dependencies = [
 "order-stat 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
 "parity-reactor 0.1.0",
 "parity-updater 1.11.0",
- "parity-version 1.11.5",
+ "parity-version 1.11.6",
 "parking_lot 0.5.4 (registry+https://github.com/rust-lang/crates.io-index)",
 "patricia-trie 0.1.0",
 "pretty_assertions 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
@ -2325,7 +2325,7 @@ dependencies = [
 "log 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)",
 "matches 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
 "parity-hash-fetch 1.11.0",
- "parity-version 1.11.5",
+ "parity-version 1.11.6",
 "parking_lot 0.5.4 (registry+https://github.com/rust-lang/crates.io-index)",
 "path 0.1.0",
 "rand 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
@ -2336,7 +2336,7 @@ dependencies = [

 [[package]]
 name = "parity-version"
-version = "1.11.5"
+version = "1.11.6"
 dependencies = [
 "ethcore-bytes 0.1.0",
 "rlp 0.2.1",
--- a/Cargo.toml
+++ b/Cargo.toml
@ -2,7 +2,7 @@
 description = "Parity Ethereum client"
 name = "parity"
 # NOTE Make sure to update util/version/Cargo.toml as well
-version = "1.11.5"
+version = "1.11.6"
 license = "GPL-3.0"
 authors = ["Parity Technologies <admin@parity.io>"]

--- a/ethcore/private-tx/src/lib.rs
+++ b/ethcore/private-tx/src/lib.rs
@ -82,7 +82,7 @@ use ethcore::client::{
 	Client, ChainNotify, ChainRoute, ChainMessageType, ClientIoMessage, BlockId, CallContract
 };
 use ethcore::account_provider::AccountProvider;
-use ethcore::miner::{self, Miner, MinerService};
+use ethcore::miner::{self, Miner, MinerService, pool_client::NonceCache};
 use ethcore::trace::{Tracer, VMTracer};
 use rustc_hex::FromHex;

@ -94,6 +94,9 @@ use_contract!(private, "PrivateContract", "res/private.json");
 /// Initialization vector length.
 const INIT_VEC_LEN: usize = 16;

+/// Size of nonce cache
+const NONCE_CACHE_SIZE: usize = 128;
+
 /// Configurtion for private transaction provider
 #[derive(Default, PartialEq, Debug, Clone)]
 pub struct ProviderConfig {
@ -243,7 +246,7 @@ impl Provider where {
 		Ok(original_transaction)
 	}

-	fn pool_client<'a>(&'a self, nonce_cache: &'a RwLock<HashMap<Address, U256>>) -> miner::pool_client::PoolClient<'a, Client> {
+	fn pool_client<'a>(&'a self, nonce_cache: &'a NonceCache) -> miner::pool_client::PoolClient<'a, Client> {
 		let engine = self.client.engine();
 		let refuse_service_transactions = true;
 		miner::pool_client::PoolClient::new(
@ -262,7 +265,7 @@ impl Provider where {
 	/// can be replaced with a single `drain()` method instead.
 	/// Thanks to this we also don't really need to lock the entire verification for the time of execution.
 	fn process_queue(&self) -> Result<(), Error> {
-		let nonce_cache = Default::default();
+		let nonce_cache = NonceCache::new(NONCE_CACHE_SIZE);
 		let mut verification_queue = self.transactions_for_verification.lock();
 		let ready_transactions = verification_queue.ready_transactions(self.pool_client(&nonce_cache));
 		for transaction in ready_transactions {
@ -583,7 +586,7 @@ impl Importer for Arc<Provider> {
 				trace!("Validating transaction: {:?}", original_tx);
 				// Verify with the first account available
 				trace!("The following account will be used for verification: {:?}", validation_account);
-				let nonce_cache = Default::default();
+				let nonce_cache = NonceCache::new(NONCE_CACHE_SIZE);
 				self.transactions_for_verification.lock().add_transaction(
 					original_tx,
 					contract,
--- a/ethcore/res/ethereum/tobalaba.json
+++ b/ethcore/res/ethereum/tobalaba.json
--- a/ethcore/src/client/client.rs
+++ b/ethcore/src/client/client.rs
@ -86,7 +86,6 @@ pub use verification::queue::QueueInfo as BlockQueueInfo;

 use_contract!(registry, "Registry", "res/contracts/registrar.json");

-const MAX_TX_QUEUE_SIZE: usize = 4096;
 const MAX_ANCIENT_BLOCKS_QUEUE_SIZE: usize = 4096;
 // Max number of blocks imported at once.
 const MAX_ANCIENT_BLOCKS_TO_IMPORT: usize = 4;
@ -710,13 +709,12 @@ impl Client {
 			tracedb: tracedb,
 			engine: engine,
 			pruning: config.pruning.clone(),
-			config: config,
-			db: RwLock::new(db),
+			db: RwLock::new(db.clone()),
 			state_db: RwLock::new(state_db),
 			report: RwLock::new(Default::default()),
 			io_channel: Mutex::new(message_channel),
 			notify: RwLock::new(Vec::new()),
-			queue_transactions: IoChannelQueue::new(MAX_TX_QUEUE_SIZE),
+			queue_transactions: IoChannelQueue::new(config.transaction_verification_queue_size),
 			queue_ancient_blocks: IoChannelQueue::new(MAX_ANCIENT_BLOCKS_QUEUE_SIZE),
 			queued_ancient_blocks: Default::default(),
 			ancient_blocks_import_lock: Default::default(),
@ -729,6 +727,7 @@ impl Client {
 			registrar_address,
 			exit_handler: Mutex::new(None),
 			importer,
+			config,
 		});

 		// prune old states.
--- a/ethcore/src/client/config.rs
+++ b/ethcore/src/client/config.rs
@ -71,12 +71,6 @@ pub enum Mode {
 	Off,
 }

-impl Default for Mode {
-	fn default() -> Self {
-		Mode::Active
-	}
-}
-
 impl Display for Mode {
 	fn fmt(&self, f: &mut Formatter) -> Result<(), FmtError> {
 		match *self {
@ -112,7 +106,7 @@ impl From<IpcMode> for Mode {


 /// Client configuration. Includes configs for all sub-systems.
-#[derive(Debug, PartialEq, Default)]
+#[derive(Debug, PartialEq, Clone)]
 pub struct ClientConfig {
 	/// Block queue configuration.
 	pub queue: QueueConfig,
@ -150,11 +144,39 @@ pub struct ClientConfig {
 	pub history_mem: usize,
 	/// Check seal valididity on block import
 	pub check_seal: bool,
+	/// Maximal number of transactions queued for verification in a separate thread.
+	pub transaction_verification_queue_size: usize,
 }

+impl Default for ClientConfig {
+	fn default() -> Self {
+		let mb = 1024 * 1024;
+		ClientConfig {
+			queue: Default::default(),
+			blockchain: Default::default(),
+			tracing: Default::default(),
+			vm_type: Default::default(),
+			fat_db: false,
+			pruning: journaldb::Algorithm::OverlayRecent,
+			name: "default".into(),
+			db_cache_size: None,
+			db_compaction: Default::default(),
+			db_wal: true,
+			mode: Mode::Active,
+			spec_name: "".into(),
+			verifier_type: VerifierType::Canon,
+			state_cache_size: 1 * mb,
+			jump_table_size: 1 * mb,
+			history: 64,
+			history_mem: 32 * mb,
+			check_seal: true,
+			transaction_verification_queue_size: 8192,
+		}
+	}
+}
 #[cfg(test)]
 mod test {
-	use super::{DatabaseCompactionProfile, Mode};
+	use super::{DatabaseCompactionProfile};

 	#[test]
 	fn test_default_compaction_profile() {
@ -167,9 +189,4 @@ mod test {
 		assert_eq!(DatabaseCompactionProfile::SSD, "ssd".parse().unwrap());
 		assert_eq!(DatabaseCompactionProfile::HDD, "hdd".parse().unwrap());
 	}
-
-	#[test]
-	fn test_mode_default() {
-		assert_eq!(Mode::default(), Mode::Active);
-	}
 }
--- a/ethcore/src/engines/authority_round/mod.rs
+++ b/ethcore/src/engines/authority_round/mod.rs
@ -16,12 +16,13 @@

 //! A blockchain engine that supports a non-instant BFT proof-of-authority.

+use std::collections::{BTreeMap, HashSet};
 use std::fmt;
+use std::iter::FromIterator;
+use std::ops::Deref;
 use std::sync::atomic::{AtomicUsize, AtomicBool, Ordering as AtomicOrdering};
 use std::sync::{Weak, Arc};
 use std::time::{UNIX_EPOCH, SystemTime, Duration};
-use std::collections::{BTreeMap, HashSet};
-use std::iter::FromIterator;

 use account_provider::AccountProvider;
 use block::*;
@ -29,7 +30,7 @@ use client::EngineClient;
 use engines::{Engine, Seal, EngineError, ConstructedVerifier};
 use engines::block_reward;
 use engines::block_reward::{BlockRewardContract, RewardKind};
-use error::{Error, BlockError};
+use error::{Error, ErrorKind, BlockError};
 use ethjson;
 use machine::{AuxiliaryData, Call, EthereumMachine};
 use hash::keccak;
@ -575,7 +576,6 @@ fn verify_external(header: &Header, validators: &ValidatorSet, empty_steps_trans

 	if is_invalid_proposer {
 		trace!(target: "engine", "verify_block_external: bad proposer for step: {}", header_step);
-		validators.report_benign(header.author(), header.number(), header.number());
 		Err(EngineError::NotProposer(Mismatch { expected: correct_proposer, found: header.author().clone() }))?
 	} else {
 		Ok(())
@ -607,6 +607,23 @@ impl AsMillis for Duration {
 	}
 }

+// A type for storing owned or borrowed data that has a common type.
+// Useful for returning either a borrow or owned data from a function.
+enum CowLike<'a, A: 'a + ?Sized, B> {
+	Borrowed(&'a A),
+	Owned(B),
+}
+
+impl<'a, A: ?Sized, B> Deref for CowLike<'a, A, B> where B: AsRef<A> {
+	type Target = A;
+	fn deref(&self) -> &A {
+		match self {
+			CowLike::Borrowed(b) => b,
+			CowLike::Owned(o) => o.as_ref(),
+		}
+	}
+}
+
 impl AuthorityRound {
 	/// Create a new instance of AuthorityRound engine.
 	pub fn new(our_params: AuthorityRoundParams, machine: EthereumMachine) -> Result<Arc<Self>, Error> {
@ -656,6 +673,30 @@ impl AuthorityRound {
 		Ok(engine)
 	}

+	// fetch correct validator set for epoch at header, taking into account
+	// finality of previous transitions.
+	fn epoch_set<'a>(&'a self, header: &Header) -> Result<(CowLike<ValidatorSet, SimpleList>, BlockNumber), Error> {
+		Ok(if self.immediate_transitions {
+			(CowLike::Borrowed(&*self.validators), header.number())
+		} else {
+			let mut epoch_manager = self.epoch_manager.lock();
+			let client = match self.client.read().as_ref().and_then(|weak| weak.upgrade()) {
+				Some(client) => client,
+				None => {
+					debug!(target: "engine", "Unable to verify sig: missing client ref.");
+					return Err(EngineError::RequiresClient.into())
+				}
+			};
+
+			if !epoch_manager.zoom_to(&*client, &self.machine, &*self.validators, header) {
+				debug!(target: "engine", "Unable to zoom to epoch.");
+				return Err(EngineError::RequiresClient.into())
+			}
+
+			(CowLike::Owned(epoch_manager.validators().clone()), epoch_manager.epoch_transition_number)
+		})
+	}
+
 	fn empty_steps(&self, from_step: U256, to_step: U256, parent_hash: H256) -> Vec<EmptyStep> {
 		self.empty_steps.lock().iter().filter(|e| {
 			U256::from(e.step) > from_step &&
@ -701,6 +742,28 @@ impl AuthorityRound {
 			}
 		}
 	}
+
+	fn report_skipped(&self, header: &Header, current_step: usize, parent_step: usize, validators: &ValidatorSet, set_number: u64) {
+		// we're building on top of the genesis block so don't report any skipped steps
+		if header.number() == 1 {
+			return;
+		}
+
+		if let (true, Some(me)) = (current_step > parent_step + 1, self.signer.read().address()) {
+			debug!(target: "engine", "Author {} built block with step gap. current step: {}, parent step: {}",
+				   header.author(), current_step, parent_step);
+			let mut reported = HashSet::new();
+			for step in parent_step + 1..current_step {
+				let skipped_primary = step_proposer(validators, header.parent_hash(), step);
+				// Do not report this signer.
+				if skipped_primary != me {
+					// Stop reporting once validators start repeating.
+					if !reported.insert(skipped_primary) { break; }
+					self.validators.report_benign(&skipped_primary, set_number, header.number());
+ 				}
+ 			}
+		}
+	}
 }

 fn unix_now() -> Duration {
@ -880,32 +943,15 @@ impl Engine<EthereumMachine> for AuthorityRound {
 			return Seal::None;
 		}

-		// fetch correct validator set for current epoch, taking into account
-		// finality of previous transitions.
-		let active_set;
-
-		let validators = if self.immediate_transitions {
-			&*self.validators
-		} else {
-			let mut epoch_manager = self.epoch_manager.lock();
-			let client = match self.client.read().as_ref().and_then(|weak| weak.upgrade()) {
-				Some(client) => client,
-				None => {
-					warn!(target: "engine", "Unable to generate seal: missing client ref.");
+		let (validators, set_number) = match self.epoch_set(header) {
+			Err(err) => {
+				warn!(target: "engine", "Unable to generate seal: {}", err);
 				return Seal::None;
-				}
+			},
+			Ok(ok) => ok,
 		};

-			if !epoch_manager.zoom_to(&*client, &self.machine, &*self.validators, header) {
-				debug!(target: "engine", "Unable to zoom to epoch.");
-				return Seal::None;
-			}
-
-			active_set = epoch_manager.validators().clone();
-			&active_set as &_
-		};
-
-		if is_step_proposer(validators, header.parent_hash(), step, header.author()) {
+		if is_step_proposer(&*validators, header.parent_hash(), step, header.author()) {
 			// this is guarded against by `can_propose` unless the block was signed
 			// on the same step (implies same key) and on a different node.
 			if parent_step == step.into() {
@ -936,9 +982,15 @@ impl Engine<EthereumMachine> for AuthorityRound {

 				// only issue the seal if we were the first to reach the compare_and_swap.
 				if self.step.can_propose.compare_and_swap(true, false, AtomicOrdering::SeqCst) {
-
+					// we can drop all accumulated empty step messages that are
+					// older than the parent step since we're including them in
+					// the seal
 					self.clear_empty_steps(parent_step);

+					// report any skipped primaries between the parent block and
+					// the block we're sealing
+					self.report_skipped(header, step, u64::from(parent_step) as usize, &*validators, set_number);
+
 					let mut fields = vec![
 						encode(&step).into_vec(),
 						encode(&(&H520::from(signature) as &[u8])).into_vec(),
@ -1057,13 +1109,21 @@ impl Engine<EthereumMachine> for AuthorityRound {
 			)));
 		}

-		// TODO [ToDr] Should this go from epoch manager?
-		// If yes then probably benign reporting needs to be moved further in the verification.
-		let set_number = header.number();
-
 		match verify_timestamp(&self.step.inner, header_step(header, self.empty_steps_transition)?) {
 			Err(BlockError::InvalidSeal) => {
+				// This check runs in Phase 1 where there is no guarantee that the parent block is
+				// already imported, therefore the call to `epoch_set` may fail. In that case we
+				// won't report the misbehavior but this is not a concern because:
+				// - Only authorities can report and it's expected that they'll be up-to-date and
+				//   importing, therefore the parent header will most likely be available
+				// - Even if you are an authority that is syncing the chain, the contract will most
+				//   likely ignore old reports
+				// - This specific check is only relevant if you're importing (since it checks
+				//   against wall clock)
+				if let Ok((_, set_number)) = self.epoch_set(header) {
 					self.validators.report_benign(header.author(), set_number, header.number());
+				}
+
 				Err(BlockError::InvalidSeal.into())
 			}
 			Err(e) => Err(e.into()),
@ -1075,8 +1135,8 @@ impl Engine<EthereumMachine> for AuthorityRound {
 	fn verify_block_family(&self, header: &Header, parent: &Header) -> Result<(), Error> {
 		let step = header_step(header, self.empty_steps_transition)?;
 		let parent_step = header_step(parent, self.empty_steps_transition)?;
-		// TODO [ToDr] Should this go from epoch manager?
-		let set_number = header.number();
+
+		let (validators, set_number) = self.epoch_set(header)?;

 		// Ensure header is from the step after parent.
 		if step == parent_step
@ -1103,7 +1163,7 @@ impl Engine<EthereumMachine> for AuthorityRound {
 							format!("empty step proof for invalid parent hash: {:?}", empty_step.parent_hash)))?;
 					}

-					if !empty_step.verify(&*self.validators).unwrap_or(false) {
+					if !empty_step.verify(&*validators).unwrap_or(false) {
 						Err(EngineError::InsufficientProof(
 							format!("invalid empty step proof: {:?}", empty_step)))?;
 					}
@ -1117,21 +1177,7 @@ impl Engine<EthereumMachine> for AuthorityRound {
 			}

 		} else {
-			// Report skipped primaries.
-			if let (true, Some(me)) = (step > parent_step + 1, self.signer.read().address()) {
-				debug!(target: "engine", "Author {} built block with step gap. current step: {}, parent step: {}",
-					   header.author(), step, parent_step);
-				let mut reported = HashSet::new();
-				for s in parent_step + 1..step {
-					let skipped_primary = step_proposer(&*self.validators, &parent.hash(), s);
-					// Do not report this signer.
-					if skipped_primary != me {
-						self.validators.report_benign(&skipped_primary, set_number, header.number());
-						// Stop reporting once validators start repeating.
-						if !reported.insert(skipped_primary) { break; }
- 					}
- 				}
-			}
+			self.report_skipped(header, step, parent_step, &*validators, set_number);
 		}

 		Ok(())
@ -1139,37 +1185,21 @@ impl Engine<EthereumMachine> for AuthorityRound {

 	// Check the validators.
 	fn verify_block_external(&self, header: &Header) -> Result<(), Error> {
-		// fetch correct validator set for current epoch, taking into account
-		// finality of previous transitions.
-		let active_set;
-		let validators = if self.immediate_transitions {
-			&*self.validators
-		} else {
-			// get correct validator set for epoch.
-			let client = match self.client.read().as_ref().and_then(|weak| weak.upgrade()) {
-				Some(client) => client,
-				None => {
-					debug!(target: "engine", "Unable to verify sig: missing client ref.");
-					return Err(EngineError::RequiresClient.into())
-				}
-			};
-
-			let mut epoch_manager = self.epoch_manager.lock();
-			if !epoch_manager.zoom_to(&*client, &self.machine, &*self.validators, header) {
-				debug!(target: "engine", "Unable to zoom to epoch.");
-				return Err(EngineError::RequiresClient.into())
-			}
-
-			active_set = epoch_manager.validators().clone();
-			&active_set as &_
-		};
+		let (validators, set_number) = self.epoch_set(header)?;

 		// verify signature against fixed list, but reports should go to the
 		// contract itself.
-		let res = verify_external(header, validators, self.empty_steps_transition);
-		if res.is_ok() {
+		let res = verify_external(header, &*validators, self.empty_steps_transition);
+		match res {
+			Err(Error(ErrorKind::Engine(EngineError::NotProposer(_)), _)) => {
+				self.validators.report_benign(header.author(), set_number, header.number());
+			},
+			Ok(_) => {
+				// we can drop all accumulated empty step messages that are older than this header's step
 				let header_step = header_step(header, self.empty_steps_transition)?;
 				self.clear_empty_steps(header_step.into());
+			},
+			_ => {},
 		}
 		res
 	}
@ -1574,7 +1604,6 @@ mod tests {
 		parent_header.set_seal(vec![encode(&1usize).into_vec()]);
 		parent_header.set_gas_limit("222222".parse::<U256>().unwrap());
 		let mut header: Header = Header::default();
-		header.set_number(1);
 		header.set_gas_limit("222222".parse::<U256>().unwrap());
 		header.set_seal(vec![encode(&3usize).into_vec()]);

@ -1584,8 +1613,15 @@ mod tests {

 		aura.set_signer(Arc::new(AccountProvider::transient_provider()), Default::default(), Default::default());

+		// Do not report on steps skipped between genesis and first block.
+		header.set_number(1);
 		assert!(aura.verify_block_family(&header, &parent_header).is_ok());
-		assert_eq!(last_benign.load(AtomicOrdering::SeqCst), 1);
+		assert_eq!(last_benign.load(AtomicOrdering::SeqCst), 0);
+
+		// Report on skipped steps otherwise.
+		header.set_number(2);
+		assert!(aura.verify_block_family(&header, &parent_header).is_ok());
+		assert_eq!(last_benign.load(AtomicOrdering::SeqCst), 2);
 	}

 	#[test]
--- a/ethcore/src/engines/validator_set/mod.rs
+++ b/ethcore/src/engines/validator_set/mod.rs
@ -53,7 +53,7 @@ pub fn new_validator_set(spec: ValidatorSpec) -> Box<ValidatorSet> {
 }

 /// A validator set.
-pub trait ValidatorSet: Send + Sync {
+pub trait ValidatorSet: Send + Sync + 'static {
 	/// Get the default "Call" helper, for use in general operation.
 	// TODO [keorn]: this is a hack intended to migrate off of
 	// a strict dependency on state always being available.
--- a/ethcore/src/engines/validator_set/simple_list.rs
+++ b/ethcore/src/engines/validator_set/simple_list.rs
@ -104,6 +104,12 @@ impl ValidatorSet for SimpleList {
 	}
 }

+impl AsRef<ValidatorSet> for SimpleList {
+    fn as_ref(&self) -> &ValidatorSet {
+        self
+    }
+}
+
 #[cfg(test)]
 mod tests {
 	use std::str::FromStr;
--- a/ethcore/src/ethereum/mod.rs
+++ b/ethcore/src/ethereum/mod.rs
@ -61,6 +61,11 @@ pub fn new_expanse<'a, T: Into<SpecParams<'a>>>(params: T) -> Spec {
 	load(params.into(), include_bytes!("../../res/ethereum/expanse.json"))
 }

+/// Create a new Tobalaba chain spec.
+pub fn new_tobalaba<'a, T: Into<SpecParams<'a>>>(params: T) -> Spec {
+	load(params.into(), include_bytes!("../../res/ethereum/tobalaba.json"))
+}
+
 /// Create a new Musicoin mainnet chain spec.
 pub fn new_musicoin<'a, T: Into<SpecParams<'a>>>(params: T) -> Spec {
 	load(params.into(), include_bytes!("../../res/ethereum/musicoin.json"))
--- a/ethcore/src/miner/miner.rs
+++ b/ethcore/src/miner/miner.rs
@ -14,8 +14,9 @@
 // You should have received a copy of the GNU General Public License
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.

+use std::cmp;
 use std::time::{Instant, Duration};
-use std::collections::{BTreeMap, HashSet, HashMap};
+use std::collections::{BTreeMap, BTreeSet, HashSet};
 use std::sync::Arc;

 use ansi_term::Colour;
@ -46,7 +47,7 @@ use client::BlockId;
 use executive::contract_address;
 use header::{Header, BlockNumber};
 use miner;
-use miner::pool_client::{PoolClient, CachedNonceClient};
+use miner::pool_client::{PoolClient, CachedNonceClient, NonceCache};
 use receipt::{Receipt, RichReceipt};
 use spec::Spec;
 use state::State;
@ -201,7 +202,7 @@ pub struct Miner {
 	sealing: Mutex<SealingWork>,
 	params: RwLock<AuthoringParams>,
 	listeners: RwLock<Vec<Box<NotifyWork>>>,
-	nonce_cache: RwLock<HashMap<Address, U256>>,
+	nonce_cache: NonceCache,
 	gas_pricer: Mutex<GasPricer>,
 	options: MinerOptions,
 	// TODO [ToDr] Arc is only required because of price updater
@ -227,6 +228,7 @@ impl Miner {
 		let limits = options.pool_limits.clone();
 		let verifier_options = options.pool_verification_options.clone();
 		let tx_queue_strategy = options.tx_queue_strategy;
+		let nonce_cache_size = cmp::max(4096, limits.max_count / 4);

 		Miner {
 			sealing: Mutex::new(SealingWork {
@ -240,7 +242,7 @@ impl Miner {
 			params: RwLock::new(AuthoringParams::default()),
 			listeners: RwLock::new(vec![]),
 			gas_pricer: Mutex::new(gas_pricer),
-			nonce_cache: RwLock::new(HashMap::with_capacity(1024)),
+			nonce_cache: NonceCache::new(nonce_cache_size),
 			options,
 			transaction_queue: Arc::new(TransactionQueue::new(limits, verifier_options, tx_queue_strategy)),
 			accounts,
@ -838,7 +840,40 @@ impl miner::MinerService for Miner {
 		self.transaction_queue.all_transactions()
 	}

-	fn ready_transactions<C>(&self, chain: &C) -> Vec<Arc<VerifiedTransaction>> where
+	fn pending_transaction_hashes<C>(&self, chain: &C) -> BTreeSet<H256> where
+		C: ChainInfo + Sync,
+	{
+		let chain_info = chain.chain_info();
+
+		let from_queue = || self.transaction_queue.pending_hashes(
+			|sender| self.nonce_cache.get(sender),
+		);
+
+		let from_pending = || {
+			self.map_existing_pending_block(|sealing| {
+				sealing.transactions()
+					.iter()
+					.map(|signed| signed.hash())
+					.collect()
+			}, chain_info.best_block_number)
+		};
+
+		match self.options.pending_set {
+			PendingSet::AlwaysQueue => {
+				from_queue()
+			},
+			PendingSet::AlwaysSealing => {
+				from_pending().unwrap_or_default()
+			},
+			PendingSet::SealingOrElseQueue => {
+				from_pending().unwrap_or_else(from_queue)
+			},
+		}
+	}
+
+	fn ready_transactions<C>(&self, chain: &C)
+		-> Vec<Arc<VerifiedTransaction>>
+	where
 		C: ChainInfo + Nonce + Sync,
 	{
 		let chain_info = chain.chain_info();
@ -1043,14 +1078,19 @@ impl miner::MinerService for Miner {
 		// 2. We ignore blocks that are `invalid` because it doesn't have any meaning in terms of the transactions that
 		//    are in those blocks

+		let has_new_best_block = enacted.len() > 0;
+
+		if has_new_best_block {
 			// Clear nonce cache
-		self.nonce_cache.write().clear();
+			self.nonce_cache.clear();
+		}

 		// First update gas limit in transaction queue and minimal gas price.
 		let gas_limit = *chain.best_block_header().gas_limit();
 		self.update_transaction_queue_limits(gas_limit);

-		// Then import all transactions...
+
+		// Then import all transactions from retracted blocks.
 		let client = self.pool_client(chain);
 		{
 			retracted
@ -1069,10 +1109,7 @@ impl miner::MinerService for Miner {
 				});
 		}

-		// ...and at the end remove the old ones
-		self.transaction_queue.cull(client);
-
-		if enacted.len() > 0 || (imported.len() > 0 && self.options.reseal_on_uncle) {
+		if has_new_best_block || (imported.len() > 0 && self.options.reseal_on_uncle) {
 			// Reset `next_allowed_reseal` in case a block is imported.
 			// Even if min_period is high, we will always attempt to create
 			// new pending block.
@ -1086,6 +1123,15 @@ impl miner::MinerService for Miner {
 				self.update_sealing(chain);
 			}
 		}
+
+		if has_new_best_block {
+			// Make sure to cull transactions after we update sealing.
+			// Not culling won't lead to old transactions being added to the block
+			// (thanks to Ready), but culling can take significant amount of time,
+			// so best to leave it after we create some work for miners to prevent increased
+			// uncle rate.
+			self.transaction_queue.cull(client);
+		}
 	}

 	fn pending_state(&self, latest_block_number: BlockNumber) -> Option<Self::State> {
--- a/ethcore/src/miner/mod.rs
+++ b/ethcore/src/miner/mod.rs
@ -28,7 +28,7 @@ pub mod stratum;
 pub use self::miner::{Miner, MinerOptions, Penalization, PendingSet, AuthoringParams};

 use std::sync::Arc;
-use std::collections::BTreeMap;
+use std::collections::{BTreeSet, BTreeMap};

 use bytes::Bytes;
 use ethereum_types::{H256, U256, Address};
@ -164,7 +164,13 @@ pub trait MinerService : Send + Sync {
 	fn next_nonce<C>(&self, chain: &C, address: &Address) -> U256
 		where C: Nonce + Sync;

-	/// Get a list of all ready transactions.
+	/// Get a set of all pending transaction hashes.
+	///
+	/// Depending on the settings may look in transaction pool or only in pending block.
+	fn pending_transaction_hashes<C>(&self, chain: &C) -> BTreeSet<H256> where
+		C: ChainInfo + Sync;
+
+	/// Get a list of all ready transactions either ordered by priority or unordered (cheaper).
 	///
 	/// Depending on the settings may look in transaction pool or only in pending block.
 	fn ready_transactions<C>(&self, chain: &C) -> Vec<Arc<VerifiedTransaction>>
--- a/ethcore/src/miner/pool_client.rs
+++ b/ethcore/src/miner/pool_client.rs
@ -36,10 +36,32 @@ use header::Header;
 use miner;
 use miner::service_transaction_checker::ServiceTransactionChecker;

-type NoncesCache = RwLock<HashMap<Address, U256>>;
+/// Cache for state nonces.
+#[derive(Debug)]
+pub struct NonceCache {
+	nonces: RwLock<HashMap<Address, U256>>,
+	limit: usize
+}

-const MAX_NONCE_CACHE_SIZE: usize = 4096;
-const EXPECTED_NONCE_CACHE_SIZE: usize = 2048;
+impl NonceCache {
+	/// Create new cache with a limit of `limit` entries.
+	pub fn new(limit: usize) -> Self {
+		NonceCache {
+			nonces: RwLock::new(HashMap::with_capacity(limit / 2)),
+			limit,
+		}
+	}
+
+	/// Retrieve a cached nonce for given sender.
+	pub fn get(&self, sender: &Address) -> Option<U256> {
+		self.nonces.read().get(sender).cloned()
+	}
+
+	/// Clear all entries from the cache.
+	pub fn clear(&self) {
+		self.nonces.write().clear();
+	}
+}

 /// Blockchain accesss for transaction pool.
 pub struct PoolClient<'a, C: 'a> {
@ -70,7 +92,7 @@ C: BlockInfo + CallContract,
 	/// Creates new client given chain, nonce cache, accounts and service transaction verifier.
 	pub fn new(
 		chain: &'a C,
-		cache: &'a NoncesCache,
+		cache: &'a NonceCache,
 		engine: &'a EthEngine,
 		accounts: Option<&'a AccountProvider>,
 		refuse_service_transactions: bool,
@ -161,7 +183,7 @@ impl<'a, C: 'a> NonceClient for PoolClient<'a, C> where

 pub(crate) struct CachedNonceClient<'a, C: 'a> {
 	client: &'a C,
-	cache: &'a NoncesCache,
+	cache: &'a NonceCache,
 }

 impl<'a, C: 'a> Clone for CachedNonceClient<'a, C> {
@ -176,13 +198,14 @@ impl<'a, C: 'a> Clone for CachedNonceClient<'a, C> {
 impl<'a, C: 'a> fmt::Debug for CachedNonceClient<'a, C> {
 	fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
 		fmt.debug_struct("CachedNonceClient")
-			.field("cache", &self.cache.read().len())
+			.field("cache", &self.cache.nonces.read().len())
+			.field("limit", &self.cache.limit)
 			.finish()
 	}
 }

 impl<'a, C: 'a> CachedNonceClient<'a, C> {
-	pub fn new(client: &'a C, cache: &'a NoncesCache) -> Self {
+	pub fn new(client: &'a C, cache: &'a NonceCache) -> Self {
 		CachedNonceClient {
 			client,
 			cache,
@ -194,27 +217,29 @@ impl<'a, C: 'a> NonceClient for CachedNonceClient<'a, C> where
 	C: Nonce + Sync,
 {
  fn account_nonce(&self, address: &Address) -> U256 {
-	  if let Some(nonce) = self.cache.read().get(address) {
+	  if let Some(nonce) = self.cache.nonces.read().get(address) {
 		  return *nonce;
 	  }

 	  // We don't check again if cache has been populated.
 	  // It's not THAT expensive to fetch the nonce from state.
-	  let mut cache = self.cache.write();
+	  let mut cache = self.cache.nonces.write();
 	  let nonce = self.client.latest_nonce(address);
 	  cache.insert(*address, nonce);

-	  if cache.len() < MAX_NONCE_CACHE_SIZE {
+	  if cache.len() < self.cache.limit {
 		  return nonce
 	  }

+	  debug!(target: "txpool", "NonceCache: reached limit.");
+	  trace_time!("nonce_cache:clear");
+
 	  // Remove excessive amount of entries from the cache
-	  while cache.len() > EXPECTED_NONCE_CACHE_SIZE {
-		  // Just remove random entry
-		  if let Some(key) = cache.keys().next().cloned() {
-			  cache.remove(&key);
-		  }
+	  let to_remove: Vec<_> = cache.keys().take(self.cache.limit / 2).cloned().collect();
+	  for x in to_remove {
+		cache.remove(&x);
 	  }
+
 	  nonce
  }
 }
--- a/ethcore/src/verification/mod.rs
+++ b/ethcore/src/verification/mod.rs
@ -42,12 +42,6 @@ pub enum VerifierType {
 	Noop,
 }

-impl Default for VerifierType {
-	fn default() -> Self {
-		VerifierType::Canon
-	}
-}
-
 /// Create a new verifier based on type.
 pub fn new<C: BlockInfo + CallContract>(v: VerifierType) -> Box<Verifier<C>> {
 	match v {
--- a/ethcore/sync/src/api.rs
+++ b/ethcore/sync/src/api.rs
@ -376,7 +376,6 @@ impl NetworkProtocolHandler for SyncProtocolHandler {
 	}

 	fn read(&self, io: &NetworkContext, peer: &PeerId, packet_id: u8, data: &[u8]) {
-		trace_time!("sync::read");
 		ChainSync::dispatch_packet(&self.sync, &mut NetSyncIo::new(io, &*self.chain, &*self.snapshot_service, &self.overlay), *peer, packet_id, data);
 	}

--- a/ethcore/sync/src/chain/mod.rs
+++ b/ethcore/sync/src/chain/mod.rs
@ -658,6 +658,18 @@ impl ChainSync {
 				None
 			}
 		).collect();
+
+		trace!(
+			target: "sync",
+			"Syncing with peers: {} active, {} confirmed, {} total",
+			self.active_peers.len(), confirmed_peers.len(), self.peers.len()
+		);
+
+		if self.state == SyncState::Waiting {
+			trace!(target: "sync", "Waiting for the block queue");
+		} else if self.state == SyncState::SnapshotWaiting {
+			trace!(target: "sync", "Waiting for the snapshot restoration");
+		} else {
 			let mut peers: Vec<(PeerId, u8)> = confirmed_peers.iter().filter(|&&(peer_id, _)|
 				self.active_peers.contains(&peer_id)
 			).map(|v| *v).collect();
@ -665,14 +677,11 @@ impl ChainSync {
 			random::new().shuffle(&mut peers); //TODO: sort by rating
 			// prefer peers with higher protocol version
 			peers.sort_by(|&(_, ref v1), &(_, ref v2)| v1.cmp(v2));
-		trace!(
-			target: "sync",
-			"Syncing with peers: {} active, {} confirmed, {} total",
-			self.active_peers.len(), confirmed_peers.len(), self.peers.len()
-		);
+
 			for (peer_id, _) in peers {
 				self.sync_peer(io, peer_id, false);
 			}
+		}

 		if
 			(self.state == SyncState::Blocks || self.state == SyncState::NewBlocks) &&
@ -706,14 +715,6 @@ impl ChainSync {
 					trace!(target: "sync", "Skipping busy peer {}", peer_id);
 					return;
 				}
-				if self.state == SyncState::Waiting {
-					trace!(target: "sync", "Waiting for the block queue");
-					return;
-				}
-				if self.state == SyncState::SnapshotWaiting {
-					trace!(target: "sync", "Waiting for the snapshot restoration");
-					return;
-				}
 				(peer.latest_hash.clone(), peer.difficulty.clone(), peer.snapshot_number.as_ref().cloned().unwrap_or(0), peer.snapshot_hash.as_ref().cloned())
 			} else {
 				return;
--- a/logger/src/lib.rs
+++ b/logger/src/lib.rs
@ -71,7 +71,7 @@ pub fn setup_log(config: &Config) -> Result<Arc<RotatingLogger>, String> {
 	builder.filter(Some("ws"), LogLevelFilter::Warn);
 	builder.filter(Some("reqwest"), LogLevelFilter::Warn);
 	builder.filter(Some("hyper"), LogLevelFilter::Warn);
-	builder.filter(Some("rustls"), LogLevelFilter::Warn);
+	builder.filter(Some("rustls"), LogLevelFilter::Error);
 	// Enable info for others.
 	builder.filter(None, LogLevelFilter::Info);

--- a/mac/Parity.pkgproj
+++ b/mac/Parity.pkgproj
@ -462,7 +462,7 @@
 				<key>OVERWRITE_PERMISSIONS</key>
 				<false/>
 				<key>VERSION</key>
-				<string>1.11.5</string>
+				<string>1.11.6</string>
 			</dict>
 			<key>UUID</key>
 			<string>2DCD5B81-7BAF-4DA1-9251-6274B089FD36</string>
--- a/miner/src/lib.rs
+++ b/miner/src/lib.rs
@ -30,12 +30,13 @@ extern crate linked_hash_map;
 extern crate parking_lot;
 extern crate price_info;
 extern crate rlp;
-extern crate trace_time;
 extern crate transaction_pool as txpool;

 #[macro_use]
 extern crate error_chain;
 #[macro_use]
+extern crate trace_time;
+#[macro_use]
 extern crate log;

 #[cfg(test)]
--- a/miner/src/pool/mod.rs
+++ b/miner/src/pool/mod.rs
@ -46,20 +46,20 @@ pub enum PrioritizationStrategy {
 }

 /// Transaction priority.
-#[derive(Debug, PartialEq, Eq, Clone, Copy)]
+#[derive(Debug, PartialEq, Eq, PartialOrd,  Clone, Copy)]
 pub(crate) enum Priority {
-	/// Local transactions (high priority)
-	///
-	/// Transactions either from a local account or
-	/// submitted over local RPC connection via `eth_sendRawTransaction`
-	Local,
+	/// Regular transactions received over the network. (no priority boost)
+	Regular,
 	/// Transactions from retracted blocks (medium priority)
 	///
 	/// When block becomes non-canonical we re-import the transactions it contains
 	/// to the queue and boost their priority.
 	Retracted,
-	/// Regular transactions received over the network. (no priority boost)
-	Regular,
+	/// Local transactions (high priority)
+	///
+	/// Transactions either from a local account or
+	/// submitted over local RPC connection via `eth_sendRawTransaction`
+	Local,
 }

 impl Priority {
@ -105,6 +105,11 @@ impl VerifiedTransaction {
 		self.priority
 	}

+	/// Gets transaction insertion id.
+	pub(crate) fn insertion_id(&self) -> usize {
+		self.insertion_id
+	}
+
 	/// Gets wrapped `SignedTransaction`
 	pub fn signed(&self) -> &transaction::SignedTransaction {
 		&self.transaction
@ -114,9 +119,13 @@ impl VerifiedTransaction {
 	pub fn pending(&self) -> &transaction::PendingTransaction {
 		&self.transaction
 	}
+
 }

 impl txpool::VerifiedTransaction for VerifiedTransaction {
+	type Hash = H256;
+	type Sender = Address;
+
 	fn hash(&self) -> &H256 {
 		&self.hash
 	}
@ -128,8 +137,4 @@ impl txpool::VerifiedTransaction for VerifiedTransaction {
 	fn sender(&self) -> &Address {
 		&self.sender
 	}
-
-	fn insertion_id(&self) -> u64 {
-		self.insertion_id as u64
-	}
 }
--- a/miner/src/pool/queue.rs
+++ b/miner/src/pool/queue.rs
@ -19,7 +19,7 @@
 use std::{cmp, fmt};
 use std::sync::Arc;
 use std::sync::atomic::{self, AtomicUsize};
-use std::collections::BTreeMap;
+use std::collections::{BTreeMap, BTreeSet, HashMap};

 use ethereum_types::{H256, U256, Address};
 use parking_lot::RwLock;
@ -40,6 +40,14 @@ type Pool = txpool::Pool<pool::VerifiedTransaction, scoring::NonceAndGasPrice, L
 /// since it only affects transaction Condition.
 const TIMESTAMP_CACHE: u64 = 1000;

+/// How many senders at once do we attempt to process while culling.
+///
+/// When running with huge transaction pools, culling can take significant amount of time.
+/// To prevent holding `write()` lock on the pool for this long period, we split the work into
+/// chunks and allow other threads to utilize the pool in the meantime.
+/// This parameter controls how many (best) senders at once will be processed.
+const CULL_SENDERS_CHUNK: usize = 1024;
+
 /// Transaction queue status.
 #[derive(Debug, Clone, PartialEq)]
 pub struct Status {
@ -127,6 +135,50 @@ impl CachedPending {
 	}
 }

+#[derive(Debug)]
+struct RecentlyRejected {
+	inner: RwLock<HashMap<H256, transaction::Error>>,
+	limit: usize,
+}
+
+impl RecentlyRejected {
+	fn new(limit: usize) -> Self {
+		RecentlyRejected {
+			limit,
+			inner: RwLock::new(HashMap::with_capacity(MIN_REJECTED_CACHE_SIZE)),
+		}
+	}
+
+	fn clear(&self) {
+		self.inner.write().clear();
+	}
+
+	fn get(&self, hash: &H256) -> Option<transaction::Error> {
+		self.inner.read().get(hash).cloned()
+	}
+
+	fn insert(&self, hash: H256, err: &transaction::Error) {
+		if self.inner.read().contains_key(&hash) {
+			return;
+		}
+
+		let mut inner = self.inner.write();
+		inner.insert(hash, err.clone());
+
+		// clean up
+		if inner.len() > self.limit {
+			// randomly remove half of the entries
+			let to_remove: Vec<_> = inner.keys().take(self.limit / 2).cloned().collect();
+			for key in to_remove {
+				inner.remove(&key);
+			}
+		}
+	}
+}
+
+/// Minimal size of rejection cache, by default it's equal to queue size.
+const MIN_REJECTED_CACHE_SIZE: usize = 2048;
+
 /// Ethereum Transaction Queue
 ///
 /// Responsible for:
@ -139,6 +191,7 @@ pub struct TransactionQueue {
 	pool: RwLock<Pool>,
 	options: RwLock<verifier::Options>,
 	cached_pending: RwLock<CachedPending>,
+	recently_rejected: RecentlyRejected,
 }

 impl TransactionQueue {
@ -148,11 +201,13 @@ impl TransactionQueue {
 		verification_options: verifier::Options,
 		strategy: PrioritizationStrategy,
 	) -> Self {
+		let max_count = limits.max_count;
 		TransactionQueue {
 			insertion_id: Default::default(),
 			pool: RwLock::new(txpool::Pool::new(Default::default(), scoring::NonceAndGasPrice(strategy), limits)),
 			options: RwLock::new(verification_options),
 			cached_pending: RwLock::new(CachedPending::none()),
+			recently_rejected: RecentlyRejected::new(cmp::max(MIN_REJECTED_CACHE_SIZE, max_count / 4)),
 		}
 	}

@ -176,21 +231,50 @@ impl TransactionQueue {
 		let _timer = ::trace_time::PerfTimer::new("pool::verify_and_import");
 		let options = self.options.read().clone();

-		let verifier = verifier::Verifier::new(client, options, self.insertion_id.clone());
+		let transaction_to_replace = {
+			let pool = self.pool.read();
+			if pool.is_full() {
+				pool.worst_transaction().map(|worst| (pool.scoring().clone(), worst))
+			} else {
+				None
+			}
+		};
+
+		let verifier = verifier::Verifier::new(
+			client,
+			options,
+			self.insertion_id.clone(),
+			transaction_to_replace,
+		);
+
 		let results = transactions
 			.into_iter()
 			.map(|transaction| {
-				if self.pool.read().find(&transaction.hash()).is_some() {
-					bail!(transaction::Error::AlreadyImported)
+				let hash = transaction.hash();
+
+				if self.pool.read().find(&hash).is_some() {
+					return Err(transaction::Error::AlreadyImported);
 				}

-				verifier.verify_transaction(transaction)
+				if let Some(err) = self.recently_rejected.get(&hash) {
+					trace!(target: "txqueue", "[{:?}] Rejecting recently rejected: {:?}", hash, err);
+					return Err(err);
+				}
+
+				let imported = verifier
+					.verify_transaction(transaction)
+					.and_then(|verified| {
+						self.pool.write().import(verified).map_err(convert_error)
+					});
+
+				match imported {
+					Ok(_) => Ok(()),
+					Err(err) => {
+						self.recently_rejected.insert(hash, &err);
+						Err(err)
+					},
+				}
 			})
-			.map(|result| result.and_then(|verified| {
-				self.pool.write().import(verified)
-					.map(|_imported| ())
-					.map_err(convert_error)
-			}))
 			.collect::<Vec<_>>();

 		// Notify about imported transactions.
@ -209,7 +293,20 @@ impl TransactionQueue {
 		self.pool.read().pending(ready).collect()
 	}

-	/// Returns current pneding transactions.
+	/// Computes unordered set of pending hashes.
+	///
+	/// Since strict nonce-checking is not required, you may get some false positive future transactions as well.
+	pub fn pending_hashes<N>(
+		&self,
+		nonce: N,
+	) -> BTreeSet<H256> where
+		N: Fn(&Address) -> Option<U256>,
+	{
+		let ready = ready::OptionalState::new(nonce);
+		self.pool.read().pending(ready).map(|tx| tx.hash).collect()
+	}
+
+	/// Returns current pending transactions ordered by priority.
 	///
 	/// NOTE: This may return a cached version of pending transaction set.
 	/// Re-computing the pending set is possible with `#collect_pending` method,
@ -278,27 +375,38 @@ impl TransactionQueue {
 	}

 	/// Culls all stalled transactions from the pool.
-	pub fn cull<C: client::NonceClient>(
+	pub fn cull<C: client::NonceClient + Clone>(
 		&self,
 		client: C,
 	) {
+		trace_time!("pool::cull");
 		// We don't care about future transactions, so nonce_cap is not important.
 		let nonce_cap = None;
 		// We want to clear stale transactions from the queue as well.
 		// (Transactions that are occuping the queue for a long time without being included)
 		let stale_id = {
-			let current_id = self.insertion_id.load(atomic::Ordering::Relaxed) as u64;
+			let current_id = self.insertion_id.load(atomic::Ordering::Relaxed);
 			// wait at least for half of the queue to be replaced
 			let gap = self.pool.read().options().max_count / 2;
 			// but never less than 100 transactions
-			let gap = cmp::max(100, gap) as u64;
+			let gap = cmp::max(100, gap);

 			current_id.checked_sub(gap)
 		};

-		let state_readiness = ready::State::new(client, stale_id, nonce_cap);
+		self.recently_rejected.clear();

-		let removed = self.pool.write().cull(None, state_readiness);
+		let mut removed = 0;
+		let senders: Vec<_> = {
+			let pool = self.pool.read();
+			let senders = pool.senders().cloned().collect();
+			senders
+		};
+		for chunk in senders.chunks(CULL_SENDERS_CHUNK) {
+			trace_time!("pool::cull::chunk");
+			let state_readiness = ready::State::new(client.clone(), stale_id, nonce_cap);
+			removed += self.pool.write().cull(Some(chunk), state_readiness);
+		}
 		debug!(target: "txqueue", "Removed {} stalled transactions. {}", removed, self.status());
 	}

--- a/miner/src/pool/ready.rs
+++ b/miner/src/pool/ready.rs
@ -54,14 +54,14 @@ pub struct State<C> {
 	nonces: HashMap<Address, U256>,
 	state: C,
 	max_nonce: Option<U256>,
-	stale_id: Option<u64>,
+	stale_id: Option<usize>,
 }

 impl<C> State<C> {
 	/// Create new State checker, given client interface.
 	pub fn new(
 		state: C,
-		stale_id: Option<u64>,
+		stale_id: Option<usize>,
 		max_nonce: Option<U256>,
 	) -> Self {
 		State {
@ -91,10 +91,10 @@ impl<C: NonceClient> txpool::Ready<VerifiedTransaction> for State<C> {
 		match tx.transaction.nonce.cmp(nonce) {
 			// Before marking as future check for stale ids
 			cmp::Ordering::Greater => match self.stale_id {
-				Some(id) if tx.insertion_id() < id => txpool::Readiness::Stalled,
+				Some(id) if tx.insertion_id() < id => txpool::Readiness::Stale,
 				_ => txpool::Readiness::Future,
 			},
-			cmp::Ordering::Less => txpool::Readiness::Stalled,
+			cmp::Ordering::Less => txpool::Readiness::Stale,
 			cmp::Ordering::Equal => {
 				*nonce = *nonce + 1.into();
 				txpool::Readiness::Ready
@ -130,6 +130,43 @@ impl txpool::Ready<VerifiedTransaction> for Condition {
 	}
 }

+/// Readiness checker that only relies on nonce cache (does actually go to state).
+///
+/// Checks readiness of transactions by comparing the nonce to state nonce. If nonce
+/// isn't found in provided state nonce store, defaults to the tx nonce and updates
+/// the nonce store. Useful for using with a state nonce cache when false positives are allowed.
+pub struct OptionalState<C> {
+	nonces: HashMap<Address, U256>,
+	state: C,
+}
+
+impl<C> OptionalState<C> {
+	pub fn new(state: C) -> Self {
+		OptionalState {
+			nonces: Default::default(),
+			state,
+		}
+	}
+}
+
+impl<C: Fn(&Address) -> Option<U256>> txpool::Ready<VerifiedTransaction> for OptionalState<C> {
+	fn is_ready(&mut self, tx: &VerifiedTransaction) -> txpool::Readiness {
+		let sender = tx.sender();
+		let state = &self.state;
+		let nonce = self.nonces.entry(*sender).or_insert_with(|| {
+			state(sender).unwrap_or_else(|| tx.transaction.nonce)
+		});
+		match tx.transaction.nonce.cmp(nonce) {
+			cmp::Ordering::Greater => txpool::Readiness::Future,
+			cmp::Ordering::Less => txpool::Readiness::Stale,
+			cmp::Ordering::Equal => {
+				*nonce = *nonce + 1.into();
+				txpool::Readiness::Ready
+			},
+		}
+	}
+}
+
 #[cfg(test)]
 mod tests {
 	use super::*;
@ -178,7 +215,7 @@ mod tests {
 		let res = State::new(TestClient::new().with_nonce(125), None, None).is_ready(&tx);

 		// then
-		assert_eq!(res, txpool::Readiness::Stalled);
+		assert_eq!(res, txpool::Readiness::Stale);
 	}

 	#[test]
@ -190,7 +227,7 @@ mod tests {
 		let res = State::new(TestClient::new(), Some(1), None).is_ready(&tx);

 		// then
-		assert_eq!(res, txpool::Readiness::Stalled);
+		assert_eq!(res, txpool::Readiness::Stale);
 	}

 	#[test]
--- a/miner/src/pool/scoring.rs
+++ b/miner/src/pool/scoring.rs
@ -28,23 +28,45 @@
 //! from our local node (own transactions).

 use std::cmp;
-use std::sync::Arc;

 use ethereum_types::U256;
-use txpool;
-use super::{PrioritizationStrategy, VerifiedTransaction};
+use txpool::{self, scoring};
+use super::{verifier, PrioritizationStrategy, VerifiedTransaction};

 /// Transaction with the same (sender, nonce) can be replaced only if
 /// `new_gas_price > old_gas_price + old_gas_price >> SHIFT`
 const GAS_PRICE_BUMP_SHIFT: usize = 3; // 2 = 25%, 3 = 12.5%, 4 = 6.25%

+/// Calculate minimal gas price requirement.
+#[inline]
+fn bump_gas_price(old_gp: U256) -> U256 {
+	old_gp.saturating_add(old_gp >> GAS_PRICE_BUMP_SHIFT)
+}
+
 /// Simple, gas-price based scoring for transactions.
 ///
 /// NOTE: Currently penalization does not apply to new transactions that enter the pool.
 /// We might want to store penalization status in some persistent state.
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub struct NonceAndGasPrice(pub PrioritizationStrategy);

+impl NonceAndGasPrice {
+	/// Decide if the transaction should even be considered into the pool (if the pool is full).
+	///
+	/// Used by Verifier to quickly reject transactions that don't have any chance to get into the pool later on,
+	/// and save time on more expensive checks like sender recovery, etc.
+	///
+	/// NOTE The method is never called for zero-gas-price transactions or local transactions
+	/// (such transactions are always considered to the pool and potentially rejected later on)
+	pub fn should_reject_early(&self, old: &VerifiedTransaction, new: &verifier::Transaction) -> bool {
+		if old.priority().is_local() {
+			return true
+		}
+
+		&old.transaction.gas_price > new.gas_price()
+	}
+}
+
 impl txpool::Scoring<VerifiedTransaction> for NonceAndGasPrice {
 	type Score = U256;
 	type Event = ();
@ -53,24 +75,24 @@ impl txpool::Scoring<VerifiedTransaction> for NonceAndGasPrice {
 		old.transaction.nonce.cmp(&other.transaction.nonce)
 	}

-	fn choose(&self, old: &VerifiedTransaction, new: &VerifiedTransaction) -> txpool::scoring::Choice {
+	fn choose(&self, old: &VerifiedTransaction, new: &VerifiedTransaction) -> scoring::Choice {
 		if old.transaction.nonce != new.transaction.nonce {
-			return txpool::scoring::Choice::InsertNew
+			return scoring::Choice::InsertNew
 		}

 		let old_gp = old.transaction.gas_price;
 		let new_gp = new.transaction.gas_price;

-		let min_required_gp = old_gp + (old_gp >> GAS_PRICE_BUMP_SHIFT);
+		let min_required_gp = bump_gas_price(old_gp);

 		match min_required_gp.cmp(&new_gp) {
-			cmp::Ordering::Greater => txpool::scoring::Choice::RejectNew,
-			_ => txpool::scoring::Choice::ReplaceOld,
+			cmp::Ordering::Greater => scoring::Choice::RejectNew,
+			_ => scoring::Choice::ReplaceOld,
 		}
 	}

-	fn update_scores(&self, txs: &[Arc<VerifiedTransaction>], scores: &mut [U256], change: txpool::scoring::Change) {
-		use self::txpool::scoring::Change;
+	fn update_scores(&self, txs: &[txpool::Transaction<VerifiedTransaction>], scores: &mut [U256], change: scoring::Change) {
+		use self::scoring::Change;

 		match change {
 			Change::Culled(_) => {},
@ -79,7 +101,7 @@ impl txpool::Scoring<VerifiedTransaction> for NonceAndGasPrice {
 				assert!(i < txs.len());
 				assert!(i < scores.len());

-				scores[i] = txs[i].transaction.gas_price;
+				scores[i] = txs[i].transaction.transaction.gas_price;
 				let boost = match txs[i].priority() {
 					super::Priority::Local => 15,
 					super::Priority::Retracted => 10,
@ -100,24 +122,26 @@ impl txpool::Scoring<VerifiedTransaction> for NonceAndGasPrice {
 		}
 	}

-	fn should_replace(&self, old: &VerifiedTransaction, new: &VerifiedTransaction) -> bool {
+	fn should_replace(&self, old: &VerifiedTransaction, new: &VerifiedTransaction) -> scoring::Choice {
 		if old.sender == new.sender {
 			// prefer earliest transaction
-			if new.transaction.nonce < old.transaction.nonce {
-				return true
+			match new.transaction.nonce.cmp(&old.transaction.nonce) {
+				cmp::Ordering::Less => scoring::Choice::ReplaceOld,
+				cmp::Ordering::Greater => scoring::Choice::RejectNew,
+				cmp::Ordering::Equal => self.choose(old, new),
+			}
+		} else if old.priority().is_local() && new.priority().is_local() {
+			// accept local transactions over the limit
+			scoring::Choice::InsertNew
+		} else {
+			let old_score = (old.priority(), old.transaction.gas_price);
+			let new_score = (new.priority(), new.transaction.gas_price);
+			if new_score > old_score {
+				scoring::Choice::ReplaceOld
+			} else {
+				scoring::Choice::RejectNew
 			}
 	 	}
-
-		// Always kick out non-local transactions in favour of local ones.
-		if new.priority().is_local() && !old.priority().is_local() {
-			return true;
-		}
-		// And never kick out local transactions in favour of external ones.
-		if !new.priority().is_local() && old.priority.is_local() {
-			return false;
-		}
-
-		self.choose(old, new) == txpool::scoring::Choice::ReplaceOld
 	}
 }

@ -125,22 +149,119 @@ impl txpool::Scoring<VerifiedTransaction> for NonceAndGasPrice {
 mod tests {
 	use super::*;

+	use std::sync::Arc;
+	use ethkey::{Random, Generator};
 	use pool::tests::tx::{Tx, TxExt};
 	use txpool::Scoring;
+	use txpool::scoring::Choice::*;

 	#[test]
-	fn should_replace_non_local_transaction_with_local_one() {
-		// given
+	fn should_replace_same_sender_by_nonce() {
 		let scoring = NonceAndGasPrice(PrioritizationStrategy::GasPriceOnly);
-		let tx1 = Tx::default().signed().verified();
-		let tx2 = {
-			let mut tx = Tx::default().signed().verified();
-			tx.priority = ::pool::Priority::Local;
-			tx
+
+		let tx1 = Tx {
+			nonce: 1,
+			gas_price: 1,
+			..Default::default()
+		};
+		let tx2 = Tx {
+			nonce: 2,
+			gas_price: 100,
+			..Default::default()
+		};
+		let tx3 = Tx {
+			nonce: 2,
+			gas_price: 110,
+			..Default::default()
+		};
+		let tx4 = Tx {
+			nonce: 2,
+			gas_price: 130,
+			..Default::default()
 		};

-		assert!(scoring.should_replace(&tx1, &tx2));
-		assert!(!scoring.should_replace(&tx2, &tx1));
+		let keypair = Random.generate().unwrap();
+		let txs = vec![tx1, tx2, tx3, tx4].into_iter().enumerate().map(|(i, tx)| {
+			let verified = tx.unsigned().sign(keypair.secret(), None).verified();
+			txpool::Transaction {
+				insertion_id: i as u64,
+				transaction: Arc::new(verified),
+			}
+		}).collect::<Vec<_>>();
+
+		assert_eq!(scoring.should_replace(&txs[0], &txs[1]), RejectNew);
+		assert_eq!(scoring.should_replace(&txs[1], &txs[0]), ReplaceOld);
+
+		assert_eq!(scoring.should_replace(&txs[1], &txs[2]), RejectNew);
+		assert_eq!(scoring.should_replace(&txs[2], &txs[1]), RejectNew);
+
+		assert_eq!(scoring.should_replace(&txs[1], &txs[3]), ReplaceOld);
+		assert_eq!(scoring.should_replace(&txs[3], &txs[1]), RejectNew);
+	}
+
+	#[test]
+	fn should_replace_different_sender_by_priority_and_gas_price() {
+		// given
+		let scoring = NonceAndGasPrice(PrioritizationStrategy::GasPriceOnly);
+		let tx_regular_low_gas = {
+			let tx = Tx {
+				nonce: 1,
+				gas_price: 1,
+				..Default::default()
+			};
+			let verified_tx = tx.signed().verified();
+			txpool::Transaction {
+				insertion_id: 0,
+				transaction: Arc::new(verified_tx),
+			}
+		};
+		let tx_regular_high_gas = {
+			let tx = Tx {
+				nonce: 2,
+				gas_price: 10,
+				..Default::default()
+			};
+			let verified_tx = tx.signed().verified();
+			txpool::Transaction {
+				insertion_id: 1,
+				transaction: Arc::new(verified_tx),
+			}
+		};
+		let tx_local_low_gas = {
+			let tx = Tx {
+				nonce: 2,
+				gas_price: 1,
+				..Default::default()
+			};
+			let mut verified_tx = tx.signed().verified();
+			verified_tx.priority = ::pool::Priority::Local;
+			txpool::Transaction {
+				insertion_id: 2,
+				transaction: Arc::new(verified_tx),
+			}
+		};
+		let tx_local_high_gas = {
+			let tx = Tx {
+				nonce: 1,
+				gas_price: 10,
+				..Default::default()
+			};
+			let mut verified_tx = tx.signed().verified();
+			verified_tx.priority = ::pool::Priority::Local;
+			txpool::Transaction {
+				insertion_id: 3,
+				transaction: Arc::new(verified_tx),
+			}
+		};
+
+		assert_eq!(scoring.should_replace(&tx_regular_low_gas, &tx_regular_high_gas), ReplaceOld);
+		assert_eq!(scoring.should_replace(&tx_regular_high_gas, &tx_regular_low_gas), RejectNew);
+
+		assert_eq!(scoring.should_replace(&tx_regular_high_gas, &tx_local_low_gas), ReplaceOld);
+		assert_eq!(scoring.should_replace(&tx_local_low_gas, &tx_regular_high_gas), RejectNew);
+
+		assert_eq!(scoring.should_replace(&tx_local_low_gas, &tx_local_high_gas), InsertNew);
+		assert_eq!(scoring.should_replace(&tx_local_high_gas, &tx_regular_low_gas), RejectNew);
 	}

 	#[test]
@ -155,41 +276,44 @@ mod tests {
 				1 => ::pool::Priority::Retracted,
 				_ => ::pool::Priority::Regular,
 			};
-			Arc::new(verified)
+			txpool::Transaction {
+				insertion_id: 0,
+				transaction: Arc::new(verified),
+			}
 		}).collect::<Vec<_>>();
 		let initial_scores = vec![U256::from(0), 0.into(), 0.into()];

 		// No update required
 		let mut scores = initial_scores.clone();
-		scoring.update_scores(&transactions, &mut *scores, txpool::scoring::Change::Culled(0));
-		scoring.update_scores(&transactions, &mut *scores, txpool::scoring::Change::Culled(1));
-		scoring.update_scores(&transactions, &mut *scores, txpool::scoring::Change::Culled(2));
+		scoring.update_scores(&transactions, &mut *scores, scoring::Change::Culled(0));
+		scoring.update_scores(&transactions, &mut *scores, scoring::Change::Culled(1));
+		scoring.update_scores(&transactions, &mut *scores, scoring::Change::Culled(2));
 		assert_eq!(scores, initial_scores);
 		let mut scores = initial_scores.clone();
-		scoring.update_scores(&transactions, &mut *scores, txpool::scoring::Change::RemovedAt(0));
-		scoring.update_scores(&transactions, &mut *scores, txpool::scoring::Change::RemovedAt(1));
-		scoring.update_scores(&transactions, &mut *scores, txpool::scoring::Change::RemovedAt(2));
+		scoring.update_scores(&transactions, &mut *scores, scoring::Change::RemovedAt(0));
+		scoring.update_scores(&transactions, &mut *scores, scoring::Change::RemovedAt(1));
+		scoring.update_scores(&transactions, &mut *scores, scoring::Change::RemovedAt(2));
 		assert_eq!(scores, initial_scores);

 		// Compute score at given index
 		let mut scores = initial_scores.clone();
-		scoring.update_scores(&transactions, &mut *scores, txpool::scoring::Change::InsertedAt(0));
+		scoring.update_scores(&transactions, &mut *scores, scoring::Change::InsertedAt(0));
 		assert_eq!(scores, vec![32768.into(), 0.into(), 0.into()]);
-		scoring.update_scores(&transactions, &mut *scores, txpool::scoring::Change::InsertedAt(1));
+		scoring.update_scores(&transactions, &mut *scores, scoring::Change::InsertedAt(1));
 		assert_eq!(scores, vec![32768.into(), 1024.into(), 0.into()]);
-		scoring.update_scores(&transactions, &mut *scores, txpool::scoring::Change::InsertedAt(2));
+		scoring.update_scores(&transactions, &mut *scores, scoring::Change::InsertedAt(2));
 		assert_eq!(scores, vec![32768.into(), 1024.into(), 1.into()]);

 		let mut scores = initial_scores.clone();
-		scoring.update_scores(&transactions, &mut *scores, txpool::scoring::Change::ReplacedAt(0));
+		scoring.update_scores(&transactions, &mut *scores, scoring::Change::ReplacedAt(0));
 		assert_eq!(scores, vec![32768.into(), 0.into(), 0.into()]);
-		scoring.update_scores(&transactions, &mut *scores, txpool::scoring::Change::ReplacedAt(1));
+		scoring.update_scores(&transactions, &mut *scores, scoring::Change::ReplacedAt(1));
 		assert_eq!(scores, vec![32768.into(), 1024.into(), 0.into()]);
-		scoring.update_scores(&transactions, &mut *scores, txpool::scoring::Change::ReplacedAt(2));
+		scoring.update_scores(&transactions, &mut *scores, scoring::Change::ReplacedAt(2));
 		assert_eq!(scores, vec![32768.into(), 1024.into(), 1.into()]);

 		// Check penalization
-		scoring.update_scores(&transactions, &mut *scores, txpool::scoring::Change::Event(()));
+		scoring.update_scores(&transactions, &mut *scores, scoring::Change::Event(()));
 		assert_eq!(scores, vec![32768.into(), 128.into(), 0.into()]);
 	}
 }
--- a/miner/src/pool/tests/mod.rs
+++ b/miner/src/pool/tests/mod.rs
@ -41,7 +41,6 @@ fn new_queue() -> TransactionQueue {
 		PrioritizationStrategy::GasPriceOnly,
 	)
 }
-
 #[test]
 fn should_return_correct_nonces_when_dropped_because_of_limit() {
 	// given
@ -62,10 +61,62 @@ fn should_return_correct_nonces_when_dropped_because_of_limit() {
 	let sender = tx1.sender();
 	let nonce = tx1.nonce;

+	// when
+	let r1 = txq.import(TestClient::new(), vec![tx1].retracted());
+	let r2 = txq.import(TestClient::new(), vec![tx2].retracted());
+	assert_eq!(r1, vec![Ok(())]);
+	assert_eq!(r2, vec![Err(transaction::Error::LimitReached)]);
+	assert_eq!(txq.status().status.transaction_count, 1);
+
+	// then
+	assert_eq!(txq.next_nonce(TestClient::new(), &sender), Some(nonce + 1.into()));
+
+	// when
+	let tx1 = Tx::gas_price(2).signed();
+	let tx2 = Tx::gas_price(2).signed();
+	let tx3 = Tx::gas_price(1).signed();
+	let tx4 = Tx::gas_price(3).signed();
+	let res = txq.import(TestClient::new(), vec![tx1, tx2].retracted());
+	let res2 = txq.import(TestClient::new(), vec![tx3, tx4].retracted());
+
+	// then
+	assert_eq!(res, vec![Ok(()), Ok(())]);
+	assert_eq!(res2, vec![
+			   // The error here indicates reaching the limit
+			   // and minimal effective gas price taken into account.
+			   Err(transaction::Error::InsufficientGasPrice { minimal: 2.into(), got: 1.into() }),
+			   Ok(())
+	]);
+	assert_eq!(txq.status().status.transaction_count, 3);
+	// First inserted transacton got dropped because of limit
+	assert_eq!(txq.next_nonce(TestClient::new(), &sender), None);
+}
+
+#[test]
+fn should_never_drop_local_transactions_from_different_senders() {
+	// given
+	let txq = TransactionQueue::new(
+		txpool::Options {
+			max_count: 3,
+			max_per_sender: 1,
+			max_mem_usage: 50
+		},
+		verifier::Options {
+			minimal_gas_price: 1.into(),
+			block_gas_limit: 1_000_000.into(),
+			tx_gas_limit: 1_000_000.into(),
+		},
+		PrioritizationStrategy::GasPriceOnly,
+	);
+	let (tx1, tx2) = Tx::gas_price(2).signed_pair();
+	let sender = tx1.sender();
+	let nonce = tx1.nonce;
+
 	// when
 	let r1 = txq.import(TestClient::new(), vec![tx1].local());
 	let r2 = txq.import(TestClient::new(), vec![tx2].local());
 	assert_eq!(r1, vec![Ok(())]);
+	// max-per-sender is reached, that's ok.
 	assert_eq!(r2, vec![Err(transaction::Error::LimitReached)]);
 	assert_eq!(txq.status().status.transaction_count, 1);

@ -82,10 +133,9 @@ fn should_return_correct_nonces_when_dropped_because_of_limit() {

 	// then
 	assert_eq!(res, vec![Ok(()), Ok(())]);
-	assert_eq!(res2, vec![Err(transaction::Error::LimitReached), Ok(())]);
-	assert_eq!(txq.status().status.transaction_count, 3);
-	// First inserted transacton got dropped because of limit
-	assert_eq!(txq.next_nonce(TestClient::new(), &sender), None);
+	assert_eq!(res2, vec![Ok(()), Ok(())]);
+	assert_eq!(txq.status().status.transaction_count, 5);
+	assert_eq!(txq.next_nonce(TestClient::new(), &sender), Some(nonce + 1.into()));
 }

 #[test]
@ -815,8 +865,8 @@ fn should_avoid_verifying_transaction_already_in_pool() {
 		},
 		PrioritizationStrategy::GasPriceOnly,
 	);
-	let client = TestClient::new();
-	let tx1 = Tx::default().signed().unverified();
+	let client = TestClient::new().with_balance(1_000_000_000);
+	let tx1 = Tx::gas_price(2).signed().unverified();

 	let res = txq.import(client.clone(), vec![tx1.clone()]);
 	assert_eq!(res, vec![Ok(())]);
@ -832,3 +882,82 @@ fn should_avoid_verifying_transaction_already_in_pool() {
 	// then
 	assert_eq!(txq.status().status.transaction_count, 1);
 }
+
+#[test]
+fn should_avoid_reverifying_recently_rejected_transactions() {
+	// given
+	let txq = TransactionQueue::new(
+		txpool::Options {
+			max_count: 1,
+			max_per_sender: 2,
+			max_mem_usage: 50
+		},
+		verifier::Options {
+			minimal_gas_price: 1.into(),
+			block_gas_limit: 1_000_000.into(),
+			tx_gas_limit: 1_000_000.into(),
+		},
+		PrioritizationStrategy::GasPriceOnly,
+	);
+
+	let client = TestClient::new();
+	let tx1 = Tx::gas_price(10_000).signed().unverified();
+
+	let res = txq.import(client.clone(), vec![tx1.clone()]);
+	assert_eq!(res, vec![Err(transaction::Error::InsufficientBalance {
+		balance: 0xf67c.into(),
+		cost: 0xc8458e4.into(),
+	})]);
+	assert_eq!(txq.status().status.transaction_count, 0);
+	assert!(client.was_verification_triggered());
+
+	// when
+	let client = TestClient::new();
+	let res = txq.import(client.clone(), vec![tx1]);
+	assert_eq!(res, vec![Err(transaction::Error::InsufficientBalance {
+		balance: 0xf67c.into(),
+		cost: 0xc8458e4.into(),
+	})]);
+	assert!(!client.was_verification_triggered());
+
+	// then
+	assert_eq!(txq.status().status.transaction_count, 0);
+}
+
+
+fn should_reject_early_in_case_gas_price_is_less_than_min_effective() {
+	// given
+	let txq = TransactionQueue::new(
+		txpool::Options {
+			max_count: 1,
+			max_per_sender: 2,
+			max_mem_usage: 50
+		},
+		verifier::Options {
+			minimal_gas_price: 1.into(),
+			block_gas_limit: 1_000_000.into(),
+			tx_gas_limit: 1_000_000.into(),
+		},
+		PrioritizationStrategy::GasPriceOnly,
+	);
+	let client = TestClient::new().with_balance(1_000_000_000);
+	let tx1 = Tx::gas_price(2).signed().unverified();
+
+	let res = txq.import(client.clone(), vec![tx1]);
+	assert_eq!(res, vec![Ok(())]);
+	assert_eq!(txq.status().status.transaction_count, 1);
+	assert!(client.was_verification_triggered());
+
+	// when
+	let client = TestClient::new();
+	let tx1 = Tx::default().signed().unverified();
+	let res = txq.import(client.clone(), vec![tx1]);
+	assert_eq!(res, vec![Err(transaction::Error::InsufficientGasPrice {
+		minimal: 2.into(),
+		got: 1.into(),
+	})]);
+	assert!(!client.was_verification_triggered());
+
+	// then
+	assert_eq!(txq.status().status.transaction_count, 1);
+}
--- a/miner/src/pool/tests/tx.rs
+++ b/miner/src/pool/tests/tx.rs
@ -23,9 +23,9 @@ use pool::{verifier, VerifiedTransaction};

 #[derive(Clone)]
 pub struct Tx {
-	nonce: u64,
-	gas: u64,
-	gas_price: u64,
+	pub nonce: u64,
+	pub gas: u64,
+	pub gas_price: u64,
 }

 impl Default for Tx {
--- a/miner/src/pool/verifier.rs
+++ b/miner/src/pool/verifier.rs
@ -85,6 +85,15 @@ impl Transaction {
 		}
 	}

+	/// Return transaction gas price
+	pub fn gas_price(&self) -> &U256 {
+		match *self {
+			Transaction::Unverified(ref tx) => &tx.gas_price,
+			Transaction::Retracted(ref tx) => &tx.gas_price,
+			Transaction::Local(ref tx) => &tx.gas_price,
+		}
+	}
+
 	fn gas(&self) -> &U256 {
 		match *self {
 			Transaction::Unverified(ref tx) => &tx.gas,
@ -93,15 +102,6 @@ impl Transaction {
 		}
 	}

-
-	fn gas_price(&self) -> &U256 {
-		match *self {
-			Transaction::Unverified(ref tx) => &tx.gas_price,
-			Transaction::Retracted(ref tx) => &tx.gas_price,
-			Transaction::Local(ref tx) => &tx.gas_price,
-		}
-	}
-
 	fn transaction(&self) -> &transaction::Transaction {
 		match *self {
 			Transaction::Unverified(ref tx) => &*tx,
@ -129,24 +129,31 @@ impl Transaction {
 ///
 /// Verification can be run in parallel for all incoming transactions.
 #[derive(Debug)]
-pub struct Verifier<C> {
+pub struct Verifier<C, S, V> {
 	client: C,
 	options: Options,
 	id: Arc<AtomicUsize>,
+	transaction_to_replace: Option<(S, Arc<V>)>,
 }

-impl<C> Verifier<C> {
+impl<C, S, V> Verifier<C, S, V> {
 	/// Creates new transaction verfier with specified options.
-	pub fn new(client: C, options: Options, id: Arc<AtomicUsize>) -> Self {
+	pub fn new(
+		client: C,
+		options: Options,
+		id: Arc<AtomicUsize>,
+		transaction_to_replace: Option<(S, Arc<V>)>,
+	) -> Self {
 		Verifier {
 			client,
 			options,
 			id,
+			transaction_to_replace,
 		}
 	}
 }

-impl<C: Client> txpool::Verifier<Transaction> for Verifier<C> {
+impl<C: Client> txpool::Verifier<Transaction> for Verifier<C, ::pool::scoring::NonceAndGasPrice, VerifiedTransaction> {
 	type Error = transaction::Error;
 	type VerifiedTransaction = VerifiedTransaction;

@ -165,7 +172,7 @@ impl<C: Client> txpool::Verifier<Transaction> for Verifier<C> {
 		if tx.gas() > &gas_limit {
 			debug!(
 				target: "txqueue",
-				"[{:?}] Dropping transaction above gas limit: {} > min({}, {})",
+				"[{:?}] Rejected transaction above gas limit: {} > min({}, {})",
 				hash,
 				tx.gas(),
 				self.options.block_gas_limit,
@ -180,7 +187,7 @@ impl<C: Client> txpool::Verifier<Transaction> for Verifier<C> {
 		let minimal_gas = self.client.required_gas(tx.transaction());
 		if tx.gas() < &minimal_gas {
 			trace!(target: "txqueue",
-				"[{:?}] Dropping transaction with insufficient gas: {} < {}",
+				"[{:?}] Rejected transaction with insufficient gas: {} < {}",
 				hash,
 				tx.gas(),
 				minimal_gas,
@ -193,11 +200,12 @@ impl<C: Client> txpool::Verifier<Transaction> for Verifier<C> {
 		}

 		let is_own = tx.is_local();
-		// Quick exit for non-service transactions
-		if tx.gas_price() < &self.options.minimal_gas_price
-			&& !tx.gas_price().is_zero()
-			&& !is_own
-		{
+		// Quick exit for non-service and non-local transactions
+		//
+		// We're checking if the transaction is below configured minimal gas price
+		// or the effective minimal gas price in case the pool is full.
+		if  !tx.gas_price().is_zero() && !is_own {
+			if tx.gas_price() < &self.options.minimal_gas_price {
 				trace!(
 					target: "txqueue",
 					"[{:?}] Rejected tx below minimal gas price threshold: {} < {}",
@ -211,6 +219,23 @@ impl<C: Client> txpool::Verifier<Transaction> for Verifier<C> {
 				});
 			}

+			if let Some((ref scoring, ref vtx)) = self.transaction_to_replace {
+				if scoring.should_reject_early(vtx, &tx) {
+					trace!(
+						target: "txqueue",
+						"[{:?}] Rejected tx early, cause it doesn't have any chance to get to the pool: (gas price: {} < {})",
+						hash,
+						tx.gas_price(),
+						vtx.transaction.gas_price,
+					);
+					bail!(transaction::Error::InsufficientGasPrice {
+						minimal: vtx.transaction.gas_price,
+						got: *tx.gas_price(),
+					});
+				}
+			}
+		}
+
 		// Some more heavy checks below.
 		// Actually recover sender and verify that transaction
 		let is_retracted = tx.is_retracted();
--- a/nsis/installer.nsi
+++ b/nsis/installer.nsi
@ -10,7 +10,7 @@
 !define DESCRIPTION "Fast, light, robust Ethereum implementation"
 !define VERSIONMAJOR 1
 !define VERSIONMINOR 11
-!define VERSIONBUILD 5
+!define VERSIONBUILD 6
 !define ARGS ""
 !define FIRST_START_ARGS "--mode=passive ui"

--- a/parity/blockchain.rs
+++ b/parity/blockchain.rs
@ -362,7 +362,7 @@ fn execute_import(cmd: ImportBlockchain) -> Result<(), String> {
 		algorithm,
 		cmd.pruning_history,
 		cmd.pruning_memory,
-		cmd.check_seal
+		cmd.check_seal,
 	);

 	client_config.queue.verifier_settings = cmd.verifier_settings;
--- a/parity/cli/mod.rs
+++ b/parity/cli/mod.rs
@ -294,7 +294,7 @@ usage! {

 			ARG arg_chain: (String) = "foundation", or |c: &Config| c.parity.as_ref()?.chain.clone(),
 			"--chain=[CHAIN]",
-			"Specify the blockchain type. CHAIN may be either a JSON chain specification file or olympic, frontier, homestead, mainnet, morden, ropsten, classic, expanse, musicoin, ellaism, easthub, social, testnet, kovan or dev.",
+			"Specify the blockchain type. CHAIN may be either a JSON chain specification file or olympic, frontier, homestead, mainnet, morden, ropsten, classic, expanse, tobalaba, musicoin, ellaism, easthub, social, testnet, kovan or dev.",

 			ARG arg_keys_path: (String) = "$BASE/keys", or |c: &Config| c.parity.as_ref()?.keys_path.clone(),
 			"--keys-path=[PATH]",
--- a/parity/params.rs
+++ b/parity/params.rs
@ -33,6 +33,7 @@ pub enum SpecType {
 	Foundation,
 	Morden,
 	Ropsten,
+	Tobalaba,
 	Kovan,
 	Olympic,
 	Classic,
@ -61,6 +62,7 @@ impl str::FromStr for SpecType {
 			"morden" | "classic-testnet" => SpecType::Morden,
 			"ropsten" => SpecType::Ropsten,
 			"kovan" | "testnet" => SpecType::Kovan,
+			"tobalaba" => SpecType::Tobalaba,
 			"olympic" => SpecType::Olympic,
 			"expanse" => SpecType::Expanse,
 			"musicoin" => SpecType::Musicoin,
@ -88,6 +90,7 @@ impl fmt::Display for SpecType {
 			SpecType::Easthub => "easthub",
 			SpecType::Social => "social",
 			SpecType::Kovan => "kovan",
+			SpecType::Tobalaba => "tobalaba",
 			SpecType::Dev => "dev",
 			SpecType::Custom(ref custom) => custom,
 		})
@ -108,6 +111,7 @@ impl SpecType {
 			SpecType::Ellaism => Ok(ethereum::new_ellaism(params)),
 			SpecType::Easthub => Ok(ethereum::new_easthub(params)),
 			SpecType::Social => Ok(ethereum::new_social(params)),
+			SpecType::Tobalaba => Ok(ethereum::new_tobalaba(params)),
 			SpecType::Kovan => Ok(ethereum::new_kovan(params)),
 			SpecType::Dev => Ok(Spec::new_instant()),
 			SpecType::Custom(ref filename) => {
--- a/parity/run.rs
+++ b/parity/run.rs
@ -544,6 +544,7 @@ fn execute_impl<Cr, Rr>(cmd: RunCmd, logger: Arc<RotatingLogger>, on_client_rq:
 	// fetch service
 	let fetch = fetch::Client::new().map_err(|e| format!("Error starting fetch client: {:?}", e))?;

+	let txpool_size = cmd.miner_options.pool_limits.max_count;
 	// create miner
 	let miner = Arc::new(Miner::new(
 		cmd.miner_options,
@ -600,6 +601,7 @@ fn execute_impl<Cr, Rr>(cmd: RunCmd, logger: Arc<RotatingLogger>, on_client_rq:
 	);

 	client_config.queue.verifier_settings = cmd.verifier_settings;
+	client_config.transaction_verification_queue_size = ::std::cmp::max(2048, txpool_size / 4);

 	// set up bootnodes
 	let mut net_conf = cmd.net_conf;
--- a/parity/snapshot.rs
+++ b/parity/snapshot.rs
@ -182,7 +182,7 @@ impl SnapshotCommand {
 			algorithm,
 			self.pruning_history,
 			self.pruning_memory,
-			true
+			true,
 		);

 		let client_db = db::open_client_db(&client_path, &client_config)?;
--- a/parity/user_defaults.rs
+++ b/parity/user_defaults.rs
@ -122,7 +122,7 @@ impl Default for UserDefaults {
 	fn default() -> Self {
 		UserDefaults {
 			is_first_launch: true,
-			pruning: Algorithm::default(),
+			pruning: Algorithm::OverlayRecent,
 			tracing: false,
 			fat_db: false,
 			mode: Mode::Active,
--- a/rpc/src/v1/helpers/mod.rs
+++ b/rpc/src/v1/helpers/mod.rs
@ -40,7 +40,7 @@ mod subscription_manager;
 pub use self::dispatch::{Dispatcher, FullDispatcher};
 pub use self::network_settings::NetworkSettings;
 pub use self::poll_manager::PollManager;
-pub use self::poll_filter::{PollFilter, limit_logs};
+pub use self::poll_filter::{PollFilter, SyncPollFilter, limit_logs};
 pub use self::requests::{
 	TransactionRequest, FilledTransactionRequest, ConfirmationRequest, ConfirmationPayload, CallRequest,
 };
--- a/rpc/src/v1/helpers/poll_filter.rs
+++ b/rpc/src/v1/helpers/poll_filter.rs
@ -1,18 +1,40 @@
 //! Helper type with all filter state data.

-use std::collections::HashSet;
+use std::{
+	collections::{BTreeSet, HashSet},
+	sync::Arc,
+};
 use ethereum_types::H256;
+use parking_lot::Mutex;
 use v1::types::{Filter, Log};

 pub type BlockNumber = u64;

+/// Thread-safe filter state.
+#[derive(Clone)]
+pub struct SyncPollFilter(Arc<Mutex<PollFilter>>);
+
+impl SyncPollFilter {
+	/// New `SyncPollFilter`
+	pub fn new(f: PollFilter) -> Self {
+		SyncPollFilter(Arc::new(Mutex::new(f)))
+	}
+
+	/// Modify underlying filter
+	pub fn modify<F, R>(&self, f: F) -> R where
+		F: FnOnce(&mut PollFilter) -> R,
+	{
+		f(&mut self.0.lock())
+	}
+}
+
 /// Filter state.
 #[derive(Clone)]
 pub enum PollFilter {
 	/// Number of last block which client was notified about.
 	Block(BlockNumber),
-	/// Hashes of all transactions which client was notified about.
-	PendingTransaction(Vec<H256>),
+	/// Hashes of all pending transactions the client knows about.
+	PendingTransaction(BTreeSet<H256>),
 	/// Number of From block number, last seen block hash, pending logs and log filter itself.
 	Logs(BlockNumber, Option<H256>, HashSet<Log>, Filter)
 }
--- a/rpc/src/v1/impls/eth.rs
+++ b/rpc/src/v1/impls/eth.rs
@ -608,11 +608,9 @@ impl<C, SN: ?Sized, S: ?Sized, M, EM, T: StateInfo + 'static> Eth for EthClient<
 	}

 	fn block_transaction_count_by_number(&self, num: BlockNumber) -> BoxFuture<Option<RpcU256>> {
-		let block_number = self.client.chain_info().best_block_number;
-
 		Box::new(future::ok(match num {
 			BlockNumber::Pending =>
-				self.miner.pending_transactions(block_number).map(|x| x.len().into()),
+				Some(self.miner.pending_transaction_hashes(&*self.client).len().into()),
 			_ =>
 				self.client.block(block_number_to_id(num)).map(|block| block.transactions_count().into())
 		}))
--- a/rpc/src/v1/impls/eth_filter.rs
+++ b/rpc/src/v1/impls/eth_filter.rs
@ -17,7 +17,7 @@
 //! Eth Filter RPC implementation

 use std::sync::Arc;
-use std::collections::HashSet;
+use std::collections::BTreeSet;

 use ethcore::miner::{self, MinerService};
 use ethcore::filter::Filter as EthcoreFilter;
@ -30,7 +30,7 @@ use jsonrpc_core::futures::{future, Future};
 use jsonrpc_core::futures::future::Either;
 use v1::traits::EthFilter;
 use v1::types::{BlockNumber, Index, Filter, FilterChanges, Log, H256 as RpcH256, U256 as RpcU256};
-use v1::helpers::{errors, PollFilter, PollManager, limit_logs};
+use v1::helpers::{errors, SyncPollFilter, PollFilter, PollManager, limit_logs};
 use v1::impls::eth::pending_logs;

 /// Something which provides data that can be filtered over.
@ -41,8 +41,8 @@ pub trait Filterable {
 	/// Get a block hash by block id.
 	fn block_hash(&self, id: BlockId) -> Option<H256>;

-	/// pending transaction hashes at the given block.
-	fn pending_transactions_hashes(&self) -> Vec<H256>;
+	/// pending transaction hashes at the given block (unordered).
+	fn pending_transaction_hashes(&self) -> BTreeSet<H256>;

 	/// Get logs that match the given filter.
 	fn logs(&self, filter: EthcoreFilter) -> BoxFuture<Vec<Log>>;
@ -51,7 +51,7 @@ pub trait Filterable {
 	fn pending_logs(&self, block_number: u64, filter: &EthcoreFilter) -> Vec<Log>;

 	/// Get a reference to the poll manager.
-	fn polls(&self) -> &Mutex<PollManager<PollFilter>>;
+	fn polls(&self) -> &Mutex<PollManager<SyncPollFilter>>;

 	/// Get removed logs within route from the given block to the nearest canon block, not including the canon block. Also returns how many logs have been traversed.
 	fn removed_logs(&self, block_hash: H256, filter: &EthcoreFilter) -> (Vec<Log>, u64);
@ -61,7 +61,7 @@ pub trait Filterable {
 pub struct EthFilterClient<C, M> {
 	client: Arc<C>,
 	miner: Arc<M>,
-	polls: Mutex<PollManager<PollFilter>>,
+	polls: Mutex<PollManager<SyncPollFilter>>,
 }

 impl<C, M> EthFilterClient<C, M> {
@ -87,11 +87,8 @@ impl<C, M> Filterable for EthFilterClient<C, M> where
 		self.client.block_hash(id)
 	}

-	fn pending_transactions_hashes(&self) -> Vec<H256> {
-		self.miner.ready_transactions(&*self.client)
-			.into_iter()
-			.map(|tx| tx.signed().hash())
-			.collect()
+	fn pending_transaction_hashes(&self) -> BTreeSet<H256> {
+		self.miner.pending_transaction_hashes(&*self.client)
 	}

 	fn logs(&self, filter: EthcoreFilter) -> BoxFuture<Vec<Log>> {
@ -102,7 +99,7 @@ impl<C, M> Filterable for EthFilterClient<C, M> where
 		pending_logs(&*self.miner, block_number, filter)
 	}

-	fn polls(&self) -> &Mutex<PollManager<PollFilter>> { &self.polls }
+	fn polls(&self) -> &Mutex<PollManager<SyncPollFilter>> { &self.polls }

 	fn removed_logs(&self, block_hash: H256, filter: &EthcoreFilter) -> (Vec<Log>, u64) {
 		let inner = || -> Option<Vec<H256>> {
@ -145,29 +142,31 @@ impl<T: Filterable + Send + Sync + 'static> EthFilter for T {
 	fn new_filter(&self, filter: Filter) -> Result<RpcU256> {
 		let mut polls = self.polls().lock();
 		let block_number = self.best_block_number();
-		let id = polls.create_poll(PollFilter::Logs(block_number, None, Default::default(), filter));
+		let id = polls.create_poll(SyncPollFilter::new(PollFilter::Logs(block_number, None, Default::default(), filter)));
 		Ok(id.into())
 	}

 	fn new_block_filter(&self) -> Result<RpcU256> {
 		let mut polls = self.polls().lock();
 		// +1, since we don't want to include the current block
-		let id = polls.create_poll(PollFilter::Block(self.best_block_number() + 1));
+		let id = polls.create_poll(SyncPollFilter::new(PollFilter::Block(self.best_block_number() + 1)));
 		Ok(id.into())
 	}

 	fn new_pending_transaction_filter(&self) -> Result<RpcU256> {
 		let mut polls = self.polls().lock();
-		let pending_transactions = self.pending_transactions_hashes();
-		let id = polls.create_poll(PollFilter::PendingTransaction(pending_transactions));
+		let pending_transactions = self.pending_transaction_hashes();
+		let id = polls.create_poll(SyncPollFilter::new(PollFilter::PendingTransaction(pending_transactions)));
 		Ok(id.into())
 	}

 	fn filter_changes(&self, index: Index) -> BoxFuture<FilterChanges> {
-		let mut polls = self.polls().lock();
-		Box::new(match polls.poll_mut(&index.value()) {
-			None => Either::A(future::err(errors::filter_not_found())),
-			Some(filter) => match *filter {
+		let filter = match self.polls().lock().poll_mut(&index.value()) {
+			Some(filter) => filter.clone(),
+			None => return Box::new(future::err(errors::filter_not_found())),
+		};
+
+		Box::new(filter.modify(|filter| match *filter {
 			PollFilter::Block(ref mut block_number) => {
 				// +1, cause we want to return hashes including current block hash.
 				let current_number = self.best_block_number() + 1;
@ -182,19 +181,14 @@ impl<T: Filterable + Send + Sync + 'static> EthFilter for T {
 			},
 			PollFilter::PendingTransaction(ref mut previous_hashes) => {
 				// get hashes of pending transactions
-					let current_hashes = self.pending_transactions_hashes();
-
-					let new_hashes =
-					{
-						let previous_hashes_set = previous_hashes.iter().collect::<HashSet<_>>();
+				let current_hashes = self.pending_transaction_hashes();

+				let new_hashes = {
 					// find all new hashes
-						current_hashes
-							.iter()
-							.filter(|hash| !previous_hashes_set.contains(hash))
+					current_hashes.difference(previous_hashes)
 						.cloned()
 						.map(Into::into)
-							.collect::<Vec<RpcH256>>()
+						.collect()
 				};

 				// save all hashes of pending transactions
@ -254,18 +248,18 @@ impl<T: Filterable + Send + Sync + 'static> EthFilter for T {
 					.map(move |logs| limit_logs(logs, limit)) // limit the logs
 					.map(FilterChanges::Logs))
 			}
-			}
-		})
+		}))
 	}

 	fn filter_logs(&self, index: Index) -> BoxFuture<Vec<Log>> {
 		let filter = {
 			let mut polls = self.polls().lock();

-			match polls.poll(&index.value()) {
-				Some(&PollFilter::Logs(ref _block_number, ref _last_block_hash, ref _previous_log, ref filter)) => filter.clone(),
-				// just empty array
-				Some(_) => return Box::new(future::ok(Vec::new())),
+			match polls.poll(&index.value()).and_then(|f| f.modify(|filter| match *filter {
+				PollFilter::Logs(.., ref filter) => Some(filter.clone()),
+				_ => None,
+			})) {
+				Some(filter) => filter,
 				None => return Box::new(future::err(errors::filter_not_found())),
 			}
 		};
--- a/rpc/src/v1/impls/light/eth.rs
+++ b/rpc/src/v1/impls/light/eth.rs
@ -16,6 +16,7 @@

 //! Eth RPC interface for the light client.

+use std::collections::BTreeSet;
 use std::sync::Arc;

 use jsonrpc_core::{Result, BoxFuture};
@ -41,7 +42,7 @@ use transaction::SignedTransaction;

 use v1::impls::eth_filter::Filterable;
 use v1::helpers::{errors, limit_logs};
-use v1::helpers::{PollFilter, PollManager};
+use v1::helpers::{SyncPollFilter, PollManager};
 use v1::helpers::light_fetch::{self, LightFetch};
 use v1::traits::Eth;
 use v1::types::{
@ -61,7 +62,7 @@ pub struct EthClient<T> {
 	transaction_queue: Arc<RwLock<TransactionQueue>>,
 	accounts: Arc<AccountProvider>,
 	cache: Arc<Mutex<LightDataCache>>,
-	polls: Mutex<PollManager<PollFilter>>,
+	polls: Mutex<PollManager<SyncPollFilter>>,
 	gas_price_percentile: usize,
 }

@ -533,8 +534,8 @@ impl<T: LightChainClient + 'static> Filterable for EthClient<T> {
 		self.client.block_hash(id)
 	}

-	fn pending_transactions_hashes(&self) -> Vec<::ethereum_types::H256> {
-		Vec::new()
+	fn pending_transaction_hashes(&self) -> BTreeSet<::ethereum_types::H256> {
+		BTreeSet::new()
 	}

 	fn logs(&self, filter: EthcoreFilter) -> BoxFuture<Vec<Log>> {
@ -545,7 +546,7 @@ impl<T: LightChainClient + 'static> Filterable for EthClient<T> {
 		Vec::new() // light clients don't mine.
 	}

-	fn polls(&self) -> &Mutex<PollManager<PollFilter>> {
+	fn polls(&self) -> &Mutex<PollManager<SyncPollFilter>> {
 		&self.polls
 	}

--- a/rpc/src/v1/tests/helpers/miner_service.rs
+++ b/rpc/src/v1/tests/helpers/miner_service.rs
@ -17,7 +17,7 @@
 //! Test implementation of miner service.

 use std::sync::Arc;
-use std::collections::{BTreeMap, HashMap};
+use std::collections::{BTreeMap, BTreeSet, HashMap};

 use bytes::Bytes;
 use ethcore::account_provider::SignError as AccountError;
@ -219,6 +219,10 @@ impl MinerService for TestMinerService {
 		self.queued_transactions()
 	}

+	fn pending_transaction_hashes<C>(&self, _chain: &C) -> BTreeSet<H256> {
+		self.queued_transactions().into_iter().map(|tx| tx.signed().hash()).collect()
+	}
+
 	fn queued_transactions(&self) -> Vec<Arc<VerifiedTransaction>> {
 		self.pending_transactions.lock().values().cloned().map(|tx| {
 			Arc::new(VerifiedTransaction::from_pending_block_transaction(tx))
--- a/scripts/gitlab-build.sh
+++ b/scripts/gitlab-build.sh
@ -22,9 +22,8 @@ echo "Parity version:     " $VER
 echo "Branch:             " $CI_BUILD_REF_NAME
 echo "--------------------"

-# NOTE for md5 and sha256 we want to display filename as well
+# NOTE for sha256 we want to display filename as well
 # hence we use --* instead of -p *
-MD5_BIN="rhash --md5"
 SHA256_BIN="rhash --sha256"

 set_env () {
@ -77,22 +76,16 @@ calculate_checksums () {
  echo "Checksum calculation:"
  rhash --version

-  rm -rf *.md5
  rm -rf *.sha256

  BIN="target/$PLATFORM/release/parity$S3WIN"
  export SHA3="$($BIN tools hash $BIN)"

  echo "Parity file SHA3: $SHA3"
-  $MD5_BIN target/$PLATFORM/release/parity$S3WIN > parity$S3WIN.md5
  $SHA256_BIN target/$PLATFORM/release/parity$S3WIN > parity$S3WIN.sha256
-  $MD5_BIN target/$PLATFORM/release/parity-evm$S3WIN > parity-evm$S3WIN.md5
  $SHA256_BIN target/$PLATFORM/release/parity-evm$S3WIN > parity-evm$S3WIN.sha256
-  $MD5_BIN target/$PLATFORM/release/ethstore$S3WIN > ethstore$S3WIN.md5
  $SHA256_BIN target/$PLATFORM/release/ethstore$S3WIN > ethstore$S3WIN.sha256
-  $MD5_BIN target/$PLATFORM/release/ethkey$S3WIN > ethkey$S3WIN.md5
  $SHA256_BIN target/$PLATFORM/release/ethkey$S3WIN > ethkey$S3WIN.sha256
-  $MD5_BIN target/$PLATFORM/release/whisper$S3WIN > whisper$S3WIN.md5
  $SHA256_BIN target/$PLATFORM/release/whisper$S3WIN > whisper$S3WIN.sha256
 }
 make_deb () {
@ -129,7 +122,6 @@ make_deb () {
  cp target/$PLATFORM/release/ethkey deb/usr/bin/ethkey
  cp target/$PLATFORM/release/whisper deb/usr/bin/whisper
  dpkg-deb -b deb "parity_"$VER"_"$IDENT"_"$ARC".deb"
-  $MD5_BIN "parity_"$VER"_"$IDENT"_"$ARC".deb" > "parity_"$VER"_"$IDENT"_"$ARC".deb.md5"
  $SHA256_BIN "parity_"$VER"_"$IDENT"_"$ARC".deb" > "parity_"$VER"_"$IDENT"_"$ARC".deb.sha256"
 }
 make_rpm () {
@ -144,7 +136,6 @@ make_rpm () {
  rm -rf "parity-"$VER"-1."$ARC".rpm" || true
  fpm -s dir -t rpm -n parity -v $VER --epoch 1 --license GPLv3 -d openssl --provides parity --url https://parity.io --vendor "Parity Technologies" -a x86_64 -m "<devops@parity.io>" --description "Ethereum network client by Parity Technologies" -C /install/
  cp "parity-"$VER"-1."$ARC".rpm" "parity_"$VER"_"$IDENT"_"$ARC".rpm"
-  $MD5_BIN "parity_"$VER"_"$IDENT"_"$ARC".rpm" > "parity_"$VER"_"$IDENT"_"$ARC".rpm.md5"
  $SHA256_BIN "parity_"$VER"_"$IDENT"_"$ARC".rpm" > "parity_"$VER"_"$IDENT"_"$ARC".rpm.sha256"
 }
 make_pkg () {
@ -160,7 +151,6 @@ make_pkg () {
  packagesbuild -v mac/Parity.pkgproj
  productsign --sign 'Developer ID Installer: PARITY TECHNOLOGIES LIMITED (P2PX3JU8FT)' target/release/Parity\ Ethereum.pkg target/release/Parity\ Ethereum-signed.pkg
  mv target/release/Parity\ Ethereum-signed.pkg "parity_"$VER"_"$IDENT"_"$ARC".pkg"
-  $MD5_BIN "parity_"$VER"_"$IDENT"_"$ARC"."$EXT >> "parity_"$VER"_"$IDENT"_"$ARC".pkg.md5"
  $SHA256_BIN "parity_"$VER"_"$IDENT"_"$ARC"."$EXT >> "parity_"$VER"_"$IDENT"_"$ARC".pkg.sha256"
 }
 sign_exe () {
@ -180,7 +170,6 @@ make_exe () {
  cd ..
  cp nsis/installer.exe "parity_"$VER"_"$IDENT"_"$ARC"."$EXT
  ./sign.cmd $keyfile $certpass "parity_"$VER"_"$IDENT"_"$ARC"."$EXT
-  $MD5_BIN "parity_"$VER"_"$IDENT"_"$ARC"."$EXT -p %h > "parity_"$VER"_"$IDENT"_"$ARC"."$EXT".md5"
  $SHA256_BIN "parity_"$VER"_"$IDENT"_"$ARC"."$EXT -p %h > "parity_"$VER"_"$IDENT"_"$ARC"."$EXT".sha256"
 }
 push_binaries () {
@ -195,28 +184,22 @@ push_binaries () {
  fi
  aws s3 rm --recursive s3://$S3_BUCKET/$CI_BUILD_REF_NAME/$BUILD_PLATFORM
  aws s3api put-object --bucket $S3_BUCKET --key $CI_BUILD_REF_NAME/$BUILD_PLATFORM/parity$S3WIN --body target/$PLATFORM/release/parity$S3WIN
-  aws s3api put-object --bucket $S3_BUCKET --key $CI_BUILD_REF_NAME/$BUILD_PLATFORM/parity$S3WIN.md5 --body parity$S3WIN.md5
  aws s3api put-object --bucket $S3_BUCKET --key $CI_BUILD_REF_NAME/$BUILD_PLATFORM/parity$S3WIN.sha256 --body parity$S3WIN.sha256
  aws s3api put-object --bucket $S3_BUCKET --key $CI_BUILD_REF_NAME/$BUILD_PLATFORM/parity-evm$S3WIN --body target/$PLATFORM/release/parity-evm$S3WIN
-  aws s3api put-object --bucket $S3_BUCKET --key $CI_BUILD_REF_NAME/$BUILD_PLATFORM/parity-evm$S3WIN.md5 --body parity-evm$S3WIN.md5
  aws s3api put-object --bucket $S3_BUCKET --key $CI_BUILD_REF_NAME/$BUILD_PLATFORM/parity-evm$S3WIN.sha256 --body parity-evm$S3WIN.sha256
  aws s3api put-object --bucket $S3_BUCKET --key $CI_BUILD_REF_NAME/$BUILD_PLATFORM/ethstore$S3WIN --body target/$PLATFORM/release/ethstore$S3WIN
-  aws s3api put-object --bucket $S3_BUCKET --key $CI_BUILD_REF_NAME/$BUILD_PLATFORM/ethstore$S3WIN.md5 --body ethstore$S3WIN.md5
  aws s3api put-object --bucket $S3_BUCKET --key $CI_BUILD_REF_NAME/$BUILD_PLATFORM/ethstore$S3WIN.sha256 --body ethstore$S3WIN.sha256
  aws s3api put-object --bucket $S3_BUCKET --key $CI_BUILD_REF_NAME/$BUILD_PLATFORM/ethkey$S3WIN --body target/$PLATFORM/release/ethkey$S3WIN
-  aws s3api put-object --bucket $S3_BUCKET --key $CI_BUILD_REF_NAME/$BUILD_PLATFORM/ethkey$S3WIN.md5 --body ethkey$S3WIN.md5
  aws s3api put-object --bucket $S3_BUCKET --key $CI_BUILD_REF_NAME/$BUILD_PLATFORM/ethkey$S3WIN.sha256 --body ethkey$S3WIN.sha256
  aws s3api put-object --bucket $S3_BUCKET --key $CI_BUILD_REF_NAME/$BUILD_PLATFORM/whisper$S3WIN --body target/$PLATFORM/release/whisper$S3WIN
-  aws s3api put-object --bucket $S3_BUCKET --key $CI_BUILD_REF_NAME/$BUILD_PLATFORM/whisper$S3WIN.md5 --body whisper$S3WIN.md5
  aws s3api put-object --bucket $S3_BUCKET --key $CI_BUILD_REF_NAME/$BUILD_PLATFORM/whisper$S3WIN.sha256 --body whisper$S3WIN.sha256
  aws s3api put-object --bucket $S3_BUCKET --key $CI_BUILD_REF_NAME/$BUILD_PLATFORM/"parity_"$VER"_"$IDENT"_"$ARC"."$EXT --body "parity_"$VER"_"$IDENT"_"$ARC"."$EXT
-  aws s3api put-object --bucket $S3_BUCKET --key $CI_BUILD_REF_NAME/$BUILD_PLATFORM/"parity_"$VER"_"$IDENT"_"$ARC"."$EXT".md5" --body "parity_"$VER"_"$IDENT"_"$ARC"."$EXT".md5"
  aws s3api put-object --bucket $S3_BUCKET --key $CI_BUILD_REF_NAME/$BUILD_PLATFORM/"parity_"$VER"_"$IDENT"_"$ARC"."$EXT".sha256" --body "parity_"$VER"_"$IDENT"_"$ARC"."$EXT".sha256"
 }
 make_archive () {
  echo "add artifacts to archive"
  rm -rf parity.zip
-  zip -r parity.zip target/$PLATFORM/release/parity$S3WIN target/$PLATFORM/release/parity-evm$S3WIN target/$PLATFORM/release/ethstore$S3WIN target/$PLATFORM/release/ethkey$S3WIN target/$PLATFORM/release/whisper$S3WIN parity$S3WIN.md5 parity-evm$S3WIN.md5 ethstore$S3WIN.md5 ethkey$S3WIN.md5 whisper$S3WIN.md5 parity$S3WIN.sha256 parity-evm$S3WIN.sha256 ethstore$S3WIN.sha256 ethkey$S3WIN.sha256 whisper$S3WIN.sha256
+  zip -r parity.zip target/$PLATFORM/release/parity$S3WIN target/$PLATFORM/release/parity-evm$S3WIN target/$PLATFORM/release/ethstore$S3WIN target/$PLATFORM/release/ethkey$S3WIN target/$PLATFORM/release/whisper$S3WIN parity$S3WIN.sha256 parity-evm$S3WIN.sha256 ethstore$S3WIN.sha256 ethkey$S3WIN.sha256 whisper$S3WIN.sha256
 }

 updater_push_release () {
@ -347,11 +330,10 @@ case $BUILD_PLATFORM in
    snapcraft push "parity_"$VER"_amd64.snap"
    snapcraft status parity
    snapcraft logout
-    $MD5_BIN "parity_"$VER"_amd64.snap" > "parity_"$VER"_amd64.snap.md5"
    $SHA256_BIN "parity_"$VER"_amd64.snap" > "parity_"$VER"_amd64.snap.sha256"
    echo "add artifacts to archive"
    rm -rf parity.zip
-    zip -r parity.zip "parity_"$VER"_amd64.snap" "parity_"$VER"_amd64.snap.md5" "parity_"$VER"_amd64.snap.sha256"
+    zip -r parity.zip "parity_"$VER"_amd64.snap" "parity_"$VER"_amd64.snap.sha256"
    ;;
  x86_64-pc-windows-msvc)
    set_env_win
--- a/transaction-pool/Cargo.toml
+++ b/transaction-pool/Cargo.toml
@ -10,4 +10,6 @@ error-chain = "0.11"
 log = "0.3"
 smallvec = "0.4"
 trace-time = { path = "../util/trace-time" }
+
+[dev-dependencies]
 ethereum-types = "0.3"
--- a/transaction-pool/src/error.rs
+++ b/transaction-pool/src/error.rs
@ -14,24 +14,26 @@
 // You should have received a copy of the GNU General Public License
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.

-use ethereum_types::H256;
+/// Error chain doesn't let us have generic types.
+/// So the hashes are converted to debug strings for easy display.
+type Hash = String;

 error_chain! {
 	errors {
 		/// Transaction is already imported
-		AlreadyImported(hash: H256) {
+		AlreadyImported(hash: Hash) {
 			description("transaction is already in the pool"),
-			display("[{:?}] already imported", hash)
+			display("[{}] already imported", hash)
 		}
 		/// Transaction is too cheap to enter the queue
-		TooCheapToEnter(hash: H256, min_score: String) {
+		TooCheapToEnter(hash: Hash, min_score: String) {
 			description("the pool is full and transaction is too cheap to replace any transaction"),
-			display("[{:?}] too cheap to enter the pool. Min score: {}", hash, min_score)
+			display("[{}] too cheap to enter the pool. Min score: {}", hash, min_score)
 		}
 		/// Transaction is too cheap to replace existing transaction that occupies the same slot.
-		TooCheapToReplace(old_hash: H256, hash: H256) {
+		TooCheapToReplace(old_hash: Hash, hash: Hash) {
 			description("transaction is too cheap to replace existing transaction in the pool"),
-			display("[{:?}] too cheap to replace: {:?}", hash, old_hash)
+			display("[{}] too cheap to replace: {}", hash, old_hash)
 		}
 	}
 }
--- a/transaction-pool/src/lib.rs
+++ b/transaction-pool/src/lib.rs
@ -69,14 +69,15 @@
 #![warn(missing_docs)]

 extern crate smallvec;
-extern crate ethereum_types;
+extern crate trace_time;

 #[macro_use]
 extern crate error_chain;
 #[macro_use]
 extern crate log;

-extern crate trace_time;
+#[cfg(test)]
+extern crate ethereum_types;

 #[cfg(test)]
 mod tests;
@ -95,27 +96,29 @@ pub mod scoring;
 pub use self::error::{Error, ErrorKind};
 pub use self::listener::{Listener, NoopListener};
 pub use self::options::Options;
-pub use self::pool::{Pool, PendingIterator};
+pub use self::pool::{Pool, PendingIterator, Transaction};
 pub use self::ready::{Ready, Readiness};
 pub use self::scoring::Scoring;
 pub use self::status::{LightStatus, Status};
 pub use self::verifier::Verifier;

 use std::fmt;
-
-use ethereum_types::{H256, Address};
+use std::hash::Hash;

 /// Already verified transaction that can be safely queued.
 pub trait VerifiedTransaction: fmt::Debug {
+	/// Transaction hash type.
+	type Hash: fmt::Debug + fmt::LowerHex + Eq + Clone + Hash;
+
+	/// Transaction sender type.
+	type Sender: fmt::Debug + Eq + Clone + Hash;
+
 	/// Transaction hash
-	fn hash(&self) -> &H256;
+	fn hash(&self) -> &Self::Hash;

 	/// Memory usage
 	fn mem_usage(&self) -> usize;

 	/// Transaction sender
-	fn sender(&self) -> &Address;
-
-	/// Unique index of insertion (lower = older).
-	fn insertion_id(&self) -> u64;
+	fn sender(&self) -> &Self::Sender;
 }
--- a/transaction-pool/src/pool.rs
+++ b/transaction-pool/src/pool.rs
@ -17,33 +17,61 @@
 use std::sync::Arc;
 use std::collections::{HashMap, BTreeSet};

-use ethereum_types::{H160, H256};
-
 use error;
 use listener::{Listener, NoopListener};
 use options::Options;
 use ready::{Ready, Readiness};
-use scoring::{Scoring, ScoreWithRef};
+use scoring::{self, Scoring, ScoreWithRef};
 use status::{LightStatus, Status};
 use transactions::{AddResult, Transactions};

 use {VerifiedTransaction};

-type Sender = H160;
+/// Internal representation of transaction.
+///
+/// Includes unique insertion id that can be used for scoring explictly,
+/// but internally is used to resolve conflicts in case of equal scoring
+/// (newer transactionsa are preferred).
+#[derive(Debug)]
+pub struct Transaction<T> {
+	/// Sequential id of the transaction
+	pub insertion_id: u64,
+	/// Shared transaction
+	pub transaction: Arc<T>,
+}
+
+impl<T> Clone for Transaction<T> {
+	fn clone(&self) -> Self {
+		Transaction {
+			insertion_id: self.insertion_id,
+			transaction: self.transaction.clone(),
+		}
+	}
+}
+
+impl<T> ::std::ops::Deref for Transaction<T> {
+	type Target = Arc<T>;
+
+	fn deref(&self) -> &Self::Target {
+		&self.transaction
+	}
+}

 /// A transaction pool.
 #[derive(Debug)]
-pub struct Pool<T, S: Scoring<T>, L = NoopListener> {
+pub struct Pool<T: VerifiedTransaction, S: Scoring<T>, L = NoopListener> {
 	listener: L,
 	scoring: S,
 	options: Options,
 	mem_usage: usize,

-	transactions: HashMap<Sender, Transactions<T, S>>,
-	by_hash: HashMap<H256, Arc<T>>,
+	transactions: HashMap<T::Sender, Transactions<T, S>>,
+	by_hash: HashMap<T::Hash, Transaction<T>>,

 	best_transactions: BTreeSet<ScoreWithRef<T, S::Score>>,
 	worst_transactions: BTreeSet<ScoreWithRef<T, S::Score>>,
+
+	insertion_id: u64,
 }

 impl<T: VerifiedTransaction, S: Scoring<T> + Default> Default for Pool<T, S> {
@ -89,6 +117,7 @@ impl<T, S, L> Pool<T, S, L> where
 			by_hash,
 			best_transactions: Default::default(),
 			worst_transactions: Default::default(),
+			insertion_id: 0,
 		}

 	}
@ -104,41 +133,52 @@ impl<T, S, L> Pool<T, S, L> where
 	/// If any limit is reached the transaction with the lowest `Score` is evicted to make room.
 	///
 	/// The `Listener` will be informed on any drops or rejections.
-	pub fn import(&mut self, mut transaction: T) -> error::Result<Arc<T>> {
+	pub fn import(&mut self, transaction: T) -> error::Result<Arc<T>> {
 		let mem_usage = transaction.mem_usage();

-		ensure!(!self.by_hash.contains_key(transaction.hash()), error::ErrorKind::AlreadyImported(*transaction.hash()));
+		ensure!(!self.by_hash.contains_key(transaction.hash()), error::ErrorKind::AlreadyImported(format!("{:?}", transaction.hash())));
+
+		self.insertion_id += 1;
+		let transaction = Transaction {
+			insertion_id: self.insertion_id,
+			transaction: Arc::new(transaction),
+		};

 		// TODO [ToDr] Most likely move this after the transaction is inserted.
 		// Avoid using should_replace, but rather use scoring for that.
 		{
 			let remove_worst = |s: &mut Self, transaction| {
-				match s.remove_worst(&transaction) {
+				match s.remove_worst(transaction) {
 					Err(err) => {
-						s.listener.rejected(&Arc::new(transaction), err.kind());
+						s.listener.rejected(transaction, err.kind());
 						Err(err)
 					},
-					Ok(removed) => {
-						s.listener.dropped(&removed, Some(&transaction));
+					Ok(None) => Ok(false),
+					Ok(Some(removed)) => {
+						s.listener.dropped(&removed, Some(transaction));
 						s.finalize_remove(removed.hash());
-						Ok(transaction)
+						Ok(true)
 					},
 				}
 			};

 			while self.by_hash.len() + 1 > self.options.max_count {
 				trace!("Count limit reached: {} > {}", self.by_hash.len() + 1, self.options.max_count);
-				transaction = remove_worst(self, transaction)?;
+				if !remove_worst(self, &transaction)? {
+					break;
+				}
 			}

 			while self.mem_usage + mem_usage > self.options.max_mem_usage {
 				trace!("Mem limit reached: {} > {}", self.mem_usage + mem_usage, self.options.max_mem_usage);
-				transaction = remove_worst(self, transaction)?;
+				if !remove_worst(self, &transaction)? {
+					break;
+				}
 			}
 		}

 		let (result, prev_state, current_state) = {
-			let transactions = self.transactions.entry(*transaction.sender()).or_insert_with(Transactions::default);
+			let transactions = self.transactions.entry(transaction.sender().clone()).or_insert_with(Transactions::default);
 			// get worst and best transactions for comparison
 			let prev = transactions.worst_and_best();
 			let result = transactions.add(transaction, &self.scoring, self.options.max_per_sender);
@ -153,31 +193,31 @@ impl<T, S, L> Pool<T, S, L> where
 			AddResult::Ok(tx) => {
 				self.listener.added(&tx, None);
 				self.finalize_insert(&tx, None);
-				Ok(tx)
+				Ok(tx.transaction)
 			},
 			AddResult::PushedOut { new, old } |
 			AddResult::Replaced { new, old } => {
 				self.listener.added(&new, Some(&old));
 				self.finalize_insert(&new, Some(&old));
-				Ok(new)
+				Ok(new.transaction)
 			},
 			AddResult::TooCheap { new, old } => {
-				let error = error::ErrorKind::TooCheapToReplace(*old.hash(), *new.hash());
-				self.listener.rejected(&Arc::new(new), &error);
+				let error = error::ErrorKind::TooCheapToReplace(format!("{:x}", old.hash()), format!("{:x}", new.hash()));
+				self.listener.rejected(&new, &error);
 				bail!(error)
 			},
 			AddResult::TooCheapToEnter(new, score) => {
-				let error = error::ErrorKind::TooCheapToEnter(*new.hash(), format!("{:?}", score));
-				self.listener.rejected(&Arc::new(new), &error);
+				let error = error::ErrorKind::TooCheapToEnter(format!("{:x}", new.hash()), format!("{:?}", score));
+				self.listener.rejected(&new, &error);
 				bail!(error)
 			}
 		}
 	}

 	/// Updates state of the pool statistics if the transaction was added to a set.
-	fn finalize_insert(&mut self, new: &Arc<T>, old: Option<&Arc<T>>) {
+	fn finalize_insert(&mut self, new: &Transaction<T>, old: Option<&Transaction<T>>) {
 		self.mem_usage += new.mem_usage();
-		self.by_hash.insert(*new.hash(), new.clone());
+		self.by_hash.insert(new.hash().clone(), new.clone());

 		if let Some(old) = old {
 			self.finalize_remove(old.hash());
@ -185,23 +225,23 @@ impl<T, S, L> Pool<T, S, L> where
 	}

 	/// Updates the pool statistics if transaction was removed.
-	fn finalize_remove(&mut self, hash: &H256) -> Option<Arc<T>> {
+	fn finalize_remove(&mut self, hash: &T::Hash) -> Option<Arc<T>> {
 		self.by_hash.remove(hash).map(|old| {
-			self.mem_usage -= old.mem_usage();
-			old
+			self.mem_usage -= old.transaction.mem_usage();
+			old.transaction
 		})
 	}

 	/// Updates best and worst transactions from a sender.
 	fn update_senders_worst_and_best(
 		&mut self,
-		previous: Option<((S::Score, Arc<T>), (S::Score, Arc<T>))>,
-		current: Option<((S::Score, Arc<T>), (S::Score, Arc<T>))>,
+		previous: Option<((S::Score, Transaction<T>), (S::Score, Transaction<T>))>,
+		current: Option<((S::Score, Transaction<T>), (S::Score, Transaction<T>))>,
 	) {
 		let worst_collection = &mut self.worst_transactions;
 		let best_collection = &mut self.best_transactions;

-		let is_same = |a: &(S::Score, Arc<T>), b: &(S::Score, Arc<T>)| {
+		let is_same = |a: &(S::Score, Transaction<T>), b: &(S::Score, Transaction<T>)| {
 			a.0 == b.0 && a.1.hash() == b.1.hash()
 		};

@ -238,32 +278,42 @@ impl<T, S, L> Pool<T, S, L> where
 	}

 	/// Attempts to remove the worst transaction from the pool if it's worse than the given one.
-	fn remove_worst(&mut self, transaction: &T) -> error::Result<Arc<T>> {
+	///
+	/// Returns `None` in case we couldn't decide if the transaction should replace the worst transaction or not.
+	/// In such case we will accept the transaction even though it is going to exceed the limit.
+	fn remove_worst(&mut self, transaction: &Transaction<T>) -> error::Result<Option<Transaction<T>>> {
 		let to_remove = match self.worst_transactions.iter().next_back() {
 			// No elements to remove? and the pool is still full?
 			None => {
 				warn!("The pool is full but there are no transactions to remove.");
-				return Err(error::ErrorKind::TooCheapToEnter(*transaction.hash(), "unknown".into()).into());
+				return Err(error::ErrorKind::TooCheapToEnter(format!("{:?}", transaction.hash()), "unknown".into()).into());
 			},
-			Some(old) => if self.scoring.should_replace(&old.transaction, transaction) {
+			Some(old) => match self.scoring.should_replace(&old.transaction, transaction) {
+				// We can't decide which of them should be removed, so accept both.
+				scoring::Choice::InsertNew => None,
 				// New transaction is better than the worst one so we can replace it.
-				old.clone()
-			} else {
+				scoring::Choice::ReplaceOld => Some(old.clone()),
 				// otherwise fail
-				return Err(error::ErrorKind::TooCheapToEnter(*transaction.hash(), format!("{:?}", old.score)).into())
+				scoring::Choice::RejectNew => {
+					return Err(error::ErrorKind::TooCheapToEnter(format!("{:?}", transaction.hash()), format!("{:?}", old.score)).into())
+				},
 			},
 		};

+		if let Some(to_remove) = to_remove {
 			// Remove from transaction set
 			self.remove_from_set(to_remove.transaction.sender(), |set, scoring| {
 				set.remove(&to_remove.transaction, scoring)
 			});

-		Ok(to_remove.transaction)
+			Ok(Some(to_remove.transaction))
+		} else {
+			Ok(None)
+		}
 	}

 	/// Removes transaction from sender's transaction `HashMap`.
-	fn remove_from_set<R, F: FnOnce(&mut Transactions<T, S>, &S) -> R>(&mut self, sender: &Sender, f: F) -> Option<R> {
+	fn remove_from_set<R, F: FnOnce(&mut Transactions<T, S>, &S) -> R>(&mut self, sender: &T::Sender, f: F) -> Option<R> {
 		let (prev, next, result) = if let Some(set) = self.transactions.get_mut(sender) {
 			let prev = set.worst_and_best();
 			let result = f(set, &self.scoring);
@ -286,14 +336,14 @@ impl<T, S, L> Pool<T, S, L> where
 		self.worst_transactions.clear();

 		for (_hash, tx) in self.by_hash.drain() {
-			self.listener.dropped(&tx, None)
+			self.listener.dropped(&tx.transaction, None)
 		}
 	}

 	/// Removes single transaction from the pool.
 	/// Depending on the `is_invalid` flag the listener
 	/// will either get a `cancelled` or `invalid` notification.
-	pub fn remove(&mut self, hash: &H256, is_invalid: bool) -> Option<Arc<T>> {
+	pub fn remove(&mut self, hash: &T::Hash, is_invalid: bool) -> Option<Arc<T>> {
 		if let Some(tx) = self.finalize_remove(hash) {
 			self.remove_from_set(tx.sender(), |set, scoring| {
 				set.remove(&tx, scoring)
@ -310,7 +360,7 @@ impl<T, S, L> Pool<T, S, L> where
 	}

 	/// Removes all stalled transactions from given sender.
-	fn remove_stalled<R: Ready<T>>(&mut self, sender: &Sender, ready: &mut R) -> usize {
+	fn remove_stalled<R: Ready<T>>(&mut self, sender: &T::Sender, ready: &mut R) -> usize {
 		let removed_from_set = self.remove_from_set(sender, |transactions, scoring| {
 			transactions.cull(ready, scoring)
 		});
@ -329,7 +379,7 @@ impl<T, S, L> Pool<T, S, L> where
 	}

 	/// Removes all stalled transactions from given sender list (or from all senders).
-	pub fn cull<R: Ready<T>>(&mut self, senders: Option<&[Sender]>, mut ready: R) -> usize {
+	pub fn cull<R: Ready<T>>(&mut self, senders: Option<&[T::Sender]>, mut ready: R) -> usize {
 		let mut removed = 0;
 		match senders {
 			Some(senders) => {
@ -349,13 +399,24 @@ impl<T, S, L> Pool<T, S, L> where
 	}

 	/// Returns a transaction if it's part of the pool or `None` otherwise.
-	pub fn find(&self, hash: &H256) -> Option<Arc<T>> {
-		self.by_hash.get(hash).cloned()
+	pub fn find(&self, hash: &T::Hash) -> Option<Arc<T>> {
+		self.by_hash.get(hash).map(|t| t.transaction.clone())
 	}

 	/// Returns worst transaction in the queue (if any).
 	pub fn worst_transaction(&self) -> Option<Arc<T>> {
-		self.worst_transactions.iter().next().map(|x| x.transaction.clone())
+		self.worst_transactions.iter().next_back().map(|x| x.transaction.transaction.clone())
+	}
+
+	/// Returns true if the pool is at it's capacity.
+	pub fn is_full(&self) -> bool {
+		self.by_hash.len() >= self.options.max_count
+			|| self.mem_usage >= self.options.max_mem_usage
+	}
+
+	/// Returns senders ordered by priority of their transactions.
+	pub fn senders(&self) -> impl Iterator<Item=&T::Sender> {
+		self.best_transactions.iter().map(|tx| tx.transaction.sender())
 	}

 	/// Returns an iterator of pending (ready) transactions.
@ -368,7 +429,7 @@ impl<T, S, L> Pool<T, S, L> where
 	}

 	/// Returns pending (ready) transactions from given sender.
-	pub fn pending_from_sender<R: Ready<T>>(&self, ready: R, sender: &Sender) -> PendingIterator<T, R, S, L> {
+	pub fn pending_from_sender<R: Ready<T>>(&self, ready: R, sender: &T::Sender) -> PendingIterator<T, R, S, L> {
 		let best_transactions = self.transactions.get(sender)
 			.and_then(|transactions| transactions.worst_and_best())
 			.map(|(_, best)| ScoreWithRef::new(best.0, best.1))
@ -387,7 +448,7 @@ impl<T, S, L> Pool<T, S, L> where
 	}

 	/// Update score of transactions of a particular sender.
-	pub fn update_scores(&mut self, sender: &Sender, event: S::Event) {
+	pub fn update_scores(&mut self, sender: &T::Sender, event: S::Event) {
 		let res = if let Some(set) = self.transactions.get_mut(sender) {
 			let prev = set.worst_and_best();
 			set.update_scores(&self.scoring, event);
@ -410,7 +471,7 @@ impl<T, S, L> Pool<T, S, L> where
 			let len = transactions.len();
 			for (idx, tx) in transactions.iter().enumerate() {
 				match ready.is_ready(tx) {
-					Readiness::Stalled => status.stalled += 1,
+					Readiness::Stale => status.stalled += 1,
 					Readiness::Ready => status.pending += 1,
 					Readiness::Future => {
 						status.future += len - idx;
@ -442,6 +503,11 @@ impl<T, S, L> Pool<T, S, L> where
 		&self.listener
 	}

+	/// Borrows scoring instance.
+	pub fn scoring(&self) -> &S {
+		&self.scoring
+	}
+
 	/// Borrows listener mutably.
 	pub fn listener_mut(&mut self) -> &mut L {
 		&mut self.listener
@ -485,7 +551,7 @@ impl<'a, T, R, S, L> Iterator for PendingIterator<'a, T, R, S, L> where
 						self.best_transactions.insert(ScoreWithRef::new(score, tx));
 					}

-					return Some(best.transaction)
+					return Some(best.transaction.transaction)
 				},
 				state => trace!("[{:?}] Ignoring {:?} transaction.", best.transaction.hash(), state),
 			}
--- a/transaction-pool/src/ready.rs
+++ b/transaction-pool/src/ready.rs
@ -17,8 +17,8 @@
 /// Transaction readiness.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum Readiness {
-	/// The transaction is stalled (and should/will be removed from the pool).
-	Stalled,
+	/// The transaction is stale (and should/will be removed from the pool).
+	Stale,
 	/// The transaction is ready to be included in pending set.
 	Ready,
 	/// The transaction is not yet ready.
--- a/transaction-pool/src/scoring.rs
+++ b/transaction-pool/src/scoring.rs
@ -17,9 +17,7 @@
 //! A transactions ordering abstraction.

 use std::{cmp, fmt};
-use std::sync::Arc;
-
-use {VerifiedTransaction};
+use pool::Transaction;

 /// Represents a decision what to do with
 /// a new transaction that tries to enter the pool.
@ -98,10 +96,12 @@ pub trait Scoring<T>: fmt::Debug {
 	/// Updates the transaction scores given a list of transactions and a change to previous scoring.
 	/// NOTE: you can safely assume that both slices have the same length.
 	/// (i.e. score at index `i` represents transaction at the same index)
-	fn update_scores(&self, txs: &[Arc<T>], scores: &mut [Self::Score], change: Change<Self::Event>);
+	fn update_scores(&self, txs: &[Transaction<T>], scores: &mut [Self::Score], change: Change<Self::Event>);

 	/// Decides if `new` should push out `old` transaction from the pool.
-	fn should_replace(&self, old: &T, new: &T) -> bool;
+	///
+	/// NOTE returning `InsertNew` here can lead to some transactions being accepted above pool limits.
+	fn should_replace(&self, old: &T, new: &T) -> Choice;
 }

 /// A score with a reference to the transaction.
@ -110,7 +110,14 @@ pub struct ScoreWithRef<T, S> {
 	/// Score
 	pub score: S,
 	/// Shared transaction
-	pub transaction: Arc<T>,
+	pub transaction: Transaction<T>,
+}
+
+impl<T, S> ScoreWithRef<T, S> {
+	/// Creates a new `ScoreWithRef`
+	pub fn new(score: S, transaction: Transaction<T>) -> Self {
+		ScoreWithRef { score, transaction }
+	}
 }

 impl<T, S: Clone> Clone for ScoreWithRef<T, S> {
@ -122,30 +129,23 @@ impl<T, S: Clone> Clone for ScoreWithRef<T, S> {
 	}
 }

-impl<T, S> ScoreWithRef<T, S> {
-	/// Creates a new `ScoreWithRef`
-	pub fn new(score: S, transaction: Arc<T>) -> Self {
-		ScoreWithRef { score, transaction }
-	}
-}
-
-impl<S: cmp::Ord, T: VerifiedTransaction> Ord for ScoreWithRef<T, S> {
+impl<S: cmp::Ord, T> Ord for ScoreWithRef<T, S> {
 	fn cmp(&self, other: &Self) -> cmp::Ordering {
 		other.score.cmp(&self.score)
-			.then(other.transaction.insertion_id().cmp(&self.transaction.insertion_id()))
+			.then(other.transaction.insertion_id.cmp(&self.transaction.insertion_id))
 	}
 }

-impl<S: cmp::Ord, T: VerifiedTransaction> PartialOrd for ScoreWithRef<T, S> {
+impl<S: cmp::Ord, T> PartialOrd for ScoreWithRef<T, S> {
 	fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
 		Some(self.cmp(other))
 	}
 }

-impl<S: cmp::Ord, T: VerifiedTransaction>  PartialEq for ScoreWithRef<T, S> {
+impl<S: cmp::Ord, T>  PartialEq for ScoreWithRef<T, S> {
 	fn eq(&self, other: &Self) -> bool {
-		self.score == other.score && self.transaction.insertion_id() == other.transaction.insertion_id()
+		self.score == other.score && self.transaction.insertion_id == other.transaction.insertion_id
 	}
 }

-impl<S: cmp::Ord, T: VerifiedTransaction> Eq for ScoreWithRef<T, S> {}
+impl<S: cmp::Ord, T> Eq for ScoreWithRef<T, S> {}
--- a/transaction-pool/src/tests/helpers.rs
+++ b/transaction-pool/src/tests/helpers.rs
@ -17,12 +17,22 @@
 use std::cmp;
 use std::collections::HashMap;

-use ethereum_types::U256;
-use {scoring, Scoring, Ready, Readiness, Address as Sender};
-use super::{Transaction, SharedTransaction};
+use ethereum_types::{H160 as Sender, U256};
+use {pool, scoring, Scoring, Ready, Readiness};
+use super::Transaction;

 #[derive(Debug, Default)]
-pub struct DummyScoring;
+pub struct DummyScoring {
+	always_insert: bool,
+}
+
+impl DummyScoring {
+	pub fn always_insert() -> Self {
+		DummyScoring {
+			always_insert: true,
+		}
+	}
+}

 impl Scoring<Transaction> for DummyScoring {
 	type Score = U256;
@ -44,7 +54,7 @@ impl Scoring<Transaction> for DummyScoring {
 		}
 	}

-	fn update_scores(&self, txs: &[SharedTransaction], scores: &mut [Self::Score], change: scoring::Change) {
+	fn update_scores(&self, txs: &[pool::Transaction<Transaction>], scores: &mut [Self::Score], change: scoring::Change) {
 		if let scoring::Change::Event(_) = change {
 			// In case of event reset all scores to 0
 			for i in 0..txs.len() {
@ -58,8 +68,14 @@ impl Scoring<Transaction> for DummyScoring {
 		}
 	}

-	fn should_replace(&self, old: &Transaction, new: &Transaction) -> bool {
-		new.gas_price > old.gas_price
+	fn should_replace(&self, old: &Transaction, new: &Transaction) -> scoring::Choice {
+		if self.always_insert {
+			scoring::Choice::InsertNew
+		} else if new.gas_price > old.gas_price {
+			scoring::Choice::ReplaceOld
+		} else {
+			scoring::Choice::RejectNew
+		}
 	}
 }

@ -84,7 +100,7 @@ impl Ready<Transaction> for NonceReady {
 				*nonce = *nonce + 1.into();
 				Readiness::Ready
 			},
-			cmp::Ordering::Less => Readiness::Stalled,
+			cmp::Ordering::Less => Readiness::Stale,
 		}
 	}
 }
--- a/transaction-pool/src/tests/mod.rs
+++ b/transaction-pool/src/tests/mod.rs
@ -32,21 +32,31 @@ pub struct Transaction {
 	pub gas_price: U256,
 	pub gas: U256,
 	pub sender: Address,
-	pub insertion_id: u64,
 	pub mem_usage: usize,
 }

 impl VerifiedTransaction for Transaction {
+	type Hash = H256;
+	type Sender = Address;
+
 	fn hash(&self) -> &H256 { &self.hash }
 	fn mem_usage(&self) -> usize { self.mem_usage }
 	fn sender(&self) -> &Address { &self.sender }
-	fn insertion_id(&self) -> u64 { self.insertion_id }
 }

 pub type SharedTransaction = Arc<Transaction>;

 type TestPool = Pool<Transaction, DummyScoring>;

+impl TestPool {
+	pub fn with_limit(max_count: usize) -> Self {
+		Self::with_options(Options {
+			max_count,
+			..Default::default()
+		})
+	}
+}
+
 #[test]
 fn should_clear_queue() {
 	// given
@ -123,7 +133,7 @@ fn should_reject_if_above_count() {
 	// Reject second
 	let tx1 = b.tx().nonce(0).new();
 	let tx2 = b.tx().nonce(1).new();
-	let hash = *tx2.hash();
+	let hash = format!("{:?}", tx2.hash());
 	txq.import(tx1).unwrap();
 	assert_eq!(txq.import(tx2).unwrap_err().kind(), &error::ErrorKind::TooCheapToEnter(hash, "0x0".into()));
 	assert_eq!(txq.light_status().transaction_count, 1);
@ -149,7 +159,7 @@ fn should_reject_if_above_mem_usage() {
 	// Reject second
 	let tx1 = b.tx().nonce(1).mem_usage(1).new();
 	let tx2 = b.tx().nonce(2).mem_usage(2).new();
-	let hash = *tx2.hash();
+	let hash = format!("{:?}", tx2.hash());
 	txq.import(tx1).unwrap();
 	assert_eq!(txq.import(tx2).unwrap_err().kind(), &error::ErrorKind::TooCheapToEnter(hash, "0x0".into()));
 	assert_eq!(txq.light_status().transaction_count, 1);
@ -175,7 +185,7 @@ fn should_reject_if_above_sender_count() {
 	// Reject second
 	let tx1 = b.tx().nonce(1).new();
 	let tx2 = b.tx().nonce(2).new();
-	let hash = *tx2.hash();
+	let hash = format!("{:x}", tx2.hash());
 	txq.import(tx1).unwrap();
 	assert_eq!(txq.import(tx2).unwrap_err().kind(), &error::ErrorKind::TooCheapToEnter(hash, "0x0".into()));
 	assert_eq!(txq.light_status().transaction_count, 1);
@ -185,7 +195,7 @@ fn should_reject_if_above_sender_count() {
 	// Replace first
 	let tx1 = b.tx().nonce(1).new();
 	let tx2 = b.tx().nonce(2).gas_price(2).new();
-	let hash = *tx2.hash();
+	let hash = format!("{:x}", tx2.hash());
 	txq.import(tx1).unwrap();
 	// This results in error because we also compare nonces
 	assert_eq!(txq.import(tx2).unwrap_err().kind(), &error::ErrorKind::TooCheapToEnter(hash, "0x0".into()));
@ -444,9 +454,81 @@ fn should_return_worst_transaction() {

 	// when
 	txq.import(b.tx().nonce(0).gas_price(5).new()).unwrap();
+	txq.import(b.tx().sender(1).nonce(0).gas_price(4).new()).unwrap();

 	// then
-	assert!(txq.worst_transaction().is_some());
+	assert_eq!(txq.worst_transaction().unwrap().gas_price, 4.into());
+}
+
+#[test]
+fn should_return_is_full() {
+	// given
+	let b = TransactionBuilder::default();
+	let mut txq = TestPool::with_limit(2);
+	assert!(!txq.is_full());
+
+	// when
+	txq.import(b.tx().nonce(0).gas_price(110).new()).unwrap();
+	assert!(!txq.is_full());
+
+	txq.import(b.tx().sender(1).nonce(0).gas_price(100).new()).unwrap();
+
+	// then
+	assert!(txq.is_full());
+}
+
+#[test]
+fn should_import_even_if_limit_is_reached_and_should_replace_returns_insert_new() {
+	// given
+	let b = TransactionBuilder::default();
+	let mut txq = TestPool::with_scoring(DummyScoring::always_insert(), Options {
+		max_count: 1,
+		..Default::default()
+	});
+	txq.import(b.tx().nonce(0).gas_price(5).new()).unwrap();
+	assert_eq!(txq.light_status(), LightStatus {
+		transaction_count: 1,
+		senders: 1,
+		mem_usage: 0,
+	});
+
+	// when
+	txq.import(b.tx().nonce(1).gas_price(5).new()).unwrap();
+
+	// then
+	assert_eq!(txq.light_status(), LightStatus {
+		transaction_count: 2,
+		senders: 1,
+		mem_usage: 0,
+	});
+}
+
+#[test]
+fn should_not_import_even_if_limit_is_reached_and_should_replace_returns_false() {
+	// given
+	let b = TransactionBuilder::default();
+	let mut txq = TestPool::with_scoring(DummyScoring::default(), Options {
+		max_count: 1,
+		..Default::default()
+	});
+	txq.import(b.tx().nonce(0).gas_price(5).new()).unwrap();
+	assert_eq!(txq.light_status(), LightStatus {
+		transaction_count: 1,
+		senders: 1,
+		mem_usage: 0,
+	});
+
+	// when
+	let err = txq.import(b.tx().nonce(1).gas_price(5).new()).unwrap_err();
+
+	// then
+	assert_eq!(err.kind(),
+	&error::ErrorKind::TooCheapToEnter("0x00000000000000000000000000000000000000000000000000000000000001f5".into(), "0x5".into()));
+	assert_eq!(txq.light_status(), LightStatus {
+		transaction_count: 1,
+		senders: 1,
+		mem_usage: 0,
+	});
 }

 mod listener {
@ -489,7 +571,7 @@ mod listener {
 		let b = TransactionBuilder::default();
 		let listener = MyListener::default();
 		let results = listener.0.clone();
-		let mut txq = Pool::new(listener, DummyScoring, Options {
+		let mut txq = Pool::new(listener, DummyScoring::default(), Options {
 			max_per_sender: 1,
 			max_count: 2,
 			..Default::default()
@ -527,7 +609,7 @@ mod listener {
 		let b = TransactionBuilder::default();
 		let listener = MyListener::default();
 		let results = listener.0.clone();
-		let mut txq = Pool::new(listener, DummyScoring, Options::default());
+		let mut txq = Pool::new(listener, DummyScoring::default(), Options::default());

 		// insert
 		let tx1 = txq.import(b.tx().nonce(1).new()).unwrap();
@ -546,7 +628,7 @@ mod listener {
 		let b = TransactionBuilder::default();
 		let listener = MyListener::default();
 		let results = listener.0.clone();
-		let mut txq = Pool::new(listener, DummyScoring, Options::default());
+		let mut txq = Pool::new(listener, DummyScoring::default(), Options::default());

 		// insert
 		txq.import(b.tx().nonce(1).new()).unwrap();
@ -564,7 +646,7 @@ mod listener {
 		let b = TransactionBuilder::default();
 		let listener = MyListener::default();
 		let results = listener.0.clone();
-		let mut txq = Pool::new(listener, DummyScoring, Options::default());
+		let mut txq = Pool::new(listener, DummyScoring::default(), Options::default());

 		// insert
 		txq.import(b.tx().nonce(1).new()).unwrap();
--- a/transaction-pool/src/tests/tx_builder.rs
+++ b/transaction-pool/src/tests/tx_builder.rs
@ -14,9 +14,6 @@
 // You should have received a copy of the GNU General Public License
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.

-use std::rc::Rc;
-use std::cell::Cell;
-
 use super::{Transaction, U256, Address};

 #[derive(Debug, Default, Clone)]
@ -26,7 +23,6 @@ pub struct TransactionBuilder {
 	gas: U256,
 	sender: Address,
 	mem_usage: usize,
-	insertion_id: Rc<Cell<u64>>,
 }

 impl TransactionBuilder {
@ -55,11 +51,6 @@ impl TransactionBuilder {
 	}

 	pub fn new(self) -> Transaction {
-		let insertion_id = {
-			let id = self.insertion_id.get() + 1;
-			self.insertion_id.set(id);
-			id
-		};
 		let hash = self.nonce ^ (U256::from(100) * self.gas_price) ^ (U256::from(100_000) * U256::from(self.sender.low_u64()));
 		Transaction {
 			hash: hash.into(),
@ -67,7 +58,6 @@ impl TransactionBuilder {
 			gas_price: self.gas_price,
 			gas: 21_000.into(),
 			sender: self.sender,
-			insertion_id,
 			mem_usage: self.mem_usage,
 		}
 	}
--- a/transaction-pool/src/transactions.rs
+++ b/transaction-pool/src/transactions.rs
@ -15,28 +15,28 @@
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.

 use std::{fmt, mem};
-use std::sync::Arc;

 use smallvec::SmallVec;

 use ready::{Ready, Readiness};
 use scoring::{self, Scoring};
+use pool::Transaction;

 #[derive(Debug)]
 pub enum AddResult<T, S> {
-	Ok(Arc<T>),
+	Ok(T),
 	TooCheapToEnter(T, S),
 	TooCheap {
-		old: Arc<T>,
+		old: T,
 		new: T,
 	},
 	Replaced {
-		old: Arc<T>,
-		new: Arc<T>,
+		old: T,
+		new: T,
 	},
 	PushedOut {
-		old: Arc<T>,
-		new: Arc<T>,
+		old: T,
+		new: T,
 	},
 }

@ -45,7 +45,7 @@ const PER_SENDER: usize = 8;
 #[derive(Debug)]
 pub struct Transactions<T, S: Scoring<T>> {
 	// TODO [ToDr] Consider using something that doesn't require shifting all records.
-	transactions: SmallVec<[Arc<T>; PER_SENDER]>,
+	transactions: SmallVec<[Transaction<T>; PER_SENDER]>,
 	scores: SmallVec<[S::Score; PER_SENDER]>,
 }

@ -67,11 +67,11 @@ impl<T: fmt::Debug, S: Scoring<T>> Transactions<T, S> {
 		self.transactions.len()
 	}

-	pub fn iter(&self) -> ::std::slice::Iter<Arc<T>> {
+	pub fn iter(&self) -> ::std::slice::Iter<Transaction<T>> {
 		self.transactions.iter()
 	}

-	pub fn worst_and_best(&self) -> Option<((S::Score, Arc<T>), (S::Score, Arc<T>))> {
+	pub fn worst_and_best(&self) -> Option<((S::Score, Transaction<T>), (S::Score, Transaction<T>))> {
 		let len = self.scores.len();
 		self.scores.get(0).cloned().map(|best| {
 			let worst = self.scores[len - 1].clone();
@ -82,7 +82,7 @@ impl<T: fmt::Debug, S: Scoring<T>> Transactions<T, S> {
 		})
 	}

-	pub fn find_next(&self, tx: &T, scoring: &S) -> Option<(S::Score, Arc<T>)> {
+	pub fn find_next(&self, tx: &T, scoring: &S) -> Option<(S::Score, Transaction<T>)> {
 		self.transactions.binary_search_by(|old| scoring.compare(old, &tx)).ok().and_then(|index| {
 			let index = index + 1;
 			if index < self.scores.len() {
@ -93,18 +93,17 @@ impl<T: fmt::Debug, S: Scoring<T>> Transactions<T, S> {
 		})
 	}

-	fn push_cheapest_transaction(&mut self, tx: T, scoring: &S, max_count: usize) -> AddResult<T, S::Score> {
+	fn push_cheapest_transaction(&mut self, tx: Transaction<T>, scoring: &S, max_count: usize) -> AddResult<Transaction<T>, S::Score> {
 		let index = self.transactions.len();
 		if index == max_count {
 			let min_score = self.scores[index - 1].clone();
 			AddResult::TooCheapToEnter(tx, min_score)
 		} else {
-			let shared = Arc::new(tx);
-			self.transactions.push(shared.clone());
+			self.transactions.push(tx.clone());
 			self.scores.push(Default::default());
 			scoring.update_scores(&self.transactions, &mut self.scores, scoring::Change::InsertedAt(index));

-			AddResult::Ok(shared)
+			AddResult::Ok(tx)
 		}
 	}

@ -112,28 +111,26 @@ impl<T: fmt::Debug, S: Scoring<T>> Transactions<T, S> {
 		scoring.update_scores(&self.transactions, &mut self.scores, scoring::Change::Event(event));
 	}

-	pub fn add(&mut self, tx: T, scoring: &S, max_count: usize) -> AddResult<T, S::Score> {
-		let index = match self.transactions.binary_search_by(|old| scoring.compare(old, &tx)) {
+	pub fn add(&mut self, new: Transaction<T>, scoring: &S, max_count: usize) -> AddResult<Transaction<T>, S::Score> {
+		let index = match self.transactions.binary_search_by(|old| scoring.compare(old, &new)) {
 			Ok(index) => index,
 			Err(index) => index,
 		};

 		// Insert at the end.
 		if index == self.transactions.len() {
-			return self.push_cheapest_transaction(tx, scoring, max_count)
+			return self.push_cheapest_transaction(new, scoring, max_count)
 		}

 		// Decide if the transaction should replace some other.
-		match scoring.choose(&self.transactions[index], &tx) {
+		match scoring.choose(&self.transactions[index], &new) {
 			// New transaction should be rejected
 			scoring::Choice::RejectNew => AddResult::TooCheap {
 				old: self.transactions[index].clone(),
-				new: tx,
+				new,
 			},
 			// New transaction should be kept along with old ones.
 			scoring::Choice::InsertNew => {
-				let new = Arc::new(tx);
-
 				self.transactions.insert(index, new.clone());
 				self.scores.insert(index, Default::default());
 				scoring.update_scores(&self.transactions, &mut self.scores, scoring::Change::InsertedAt(index));
@ -153,7 +150,6 @@ impl<T: fmt::Debug, S: Scoring<T>> Transactions<T, S> {
 			},
 			// New transaction is replacing some other transaction already in the queue.
 			scoring::Choice::ReplaceOld => {
-				let new = Arc::new(tx);
 				let old = mem::replace(&mut self.transactions[index], new.clone());
 				scoring.update_scores(&self.transactions, &mut self.scores, scoring::Change::ReplacedAt(index));

@ -181,7 +177,7 @@ impl<T: fmt::Debug, S: Scoring<T>> Transactions<T, S> {
 		return true;
 	}

-	pub fn cull<R: Ready<T>>(&mut self, ready: &mut R, scoring: &S) -> SmallVec<[Arc<T>; PER_SENDER]> {
+	pub fn cull<R: Ready<T>>(&mut self, ready: &mut R, scoring: &S) -> SmallVec<[Transaction<T>; PER_SENDER]> {
 		let mut result = SmallVec::new();
 		if self.is_empty() {
 			return result;
@ -190,7 +186,7 @@ impl<T: fmt::Debug, S: Scoring<T>> Transactions<T, S> {
 		let mut first_non_stalled = 0;
 		for tx in &self.transactions {
 			match ready.is_ready(tx) {
-				Readiness::Stalled => {
+				Readiness::Stale => {
 					first_non_stalled += 1;
 				},
 				Readiness::Ready | Readiness::Future => break,
--- a/util/journaldb/src/lib.rs
+++ b/util/journaldb/src/lib.rs
@ -80,10 +80,6 @@ pub enum Algorithm {
 	RefCounted,
 }

-impl Default for Algorithm {
-	fn default() -> Algorithm { Algorithm::OverlayRecent }
-}
-
 impl str::FromStr for Algorithm {
 	type Err = String;

@ -181,11 +177,6 @@ mod tests {
 		assert!(!Algorithm::RefCounted.is_stable());
 	}

-	#[test]
-	fn test_journal_algorithm_default() {
-		assert_eq!(Algorithm::default(), Algorithm::OverlayRecent);
-	}
-
 	#[test]
 	fn test_journal_algorithm_all_types() {
 		// compiling should fail if some cases are not covered
--- a/util/version/Cargo.toml
+++ b/util/version/Cargo.toml
@ -3,7 +3,7 @@
 [package]
 name = "parity-version"
 # NOTE: this value is used for Parity version string (via env CARGO_PKG_VERSION)
-version = "1.11.5"
+version = "1.11.6"
 authors = ["Parity Technologies <admin@parity.io>"]
 build = "build.rs"