Collator for the "adder" (formerly basic-add) parachain and various small fixes (#438)

* update basic_add wasm * wasm feature and collator feature * move test parachains around a little * fix wasm build for basic_add * move basic_add to adder, introduce README * minimal basic_add collator * ensure collator messages are sent in the right order * more logging * route consensus statements to all peers * minor bugfixes for parachains * genesis builder accounts for parachain heads * fix parachains tests * targets for txpool * tweak runtime + collator * fix version in adder-collator * consistency for overflowing * adjust comment * fix stable test run * remove dummy registration test * final grumbles
2026-05-01 17:07:56 +00:00 · 2018-08-01 17:04:04 +02:00
parent 503bcb5686
commit bd3890da7e
39 changed files with 608 additions and 342 deletions
@@ -1,3 +1,26 @@
+[[package]]
+name = "adder"
+version = "0.1.0"
+dependencies = [
+ "polkadot-parachain 0.1.0",
+ "tiny-keccak 1.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "adder-collator"
+version = "0.1.0"
+dependencies = [
+ "adder 0.1.0",
+ "ctrlc 1.1.1 (git+https://github.com/paritytech/rust-ctrlc.git)",
+ "ed25519 0.1.0",
+ "exit-future 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "futures 0.1.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parking_lot 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "polkadot-collator 0.1.0",
+ "polkadot-parachain 0.1.0",
+ "polkadot-primitives 0.1.0",
+]
+
 [[package]]
 name = "aho-corasick"
 version = "0.6.4"
@@ -32,6 +32,9 @@ members = [
 	"polkadot/transaction-pool",
 	"polkadot/service",

+	"polkadot/test-parachains/adder",
+	"polkadot/test-parachains/adder/collator",
+
 	"substrate/bft",
 	"substrate/cli",
 	"substrate/client",
@@ -77,6 +80,7 @@ members = [
 ]
 exclude = [
 	"polkadot/runtime/wasm",
+	"polkadot/test-parachains/adder/wasm",
 	"demo/runtime/wasm",
 	"substrate/executor/wasm",
 	"substrate/pwasm-alloc",
@@ -92,4 +96,4 @@ is-it-maintained-open-issues = { repository = "paritytech/polkadot" }

 [profile.release]
 # Substrate runtime requires unwinding.
-panic = "unwind" 
+panic = "unwind"
@@ -8,7 +8,7 @@ SRCS=(
 	"substrate/executor/wasm"
 	"demo/runtime/wasm"
 	"substrate/test-runtime/wasm"
-	"polkadot/parachain/test-chains/basic_add"
+	"polkadot/test-parachains/"
 )

 # Make pushd/popd silent.
@@ -730,7 +730,7 @@ dependencies = [
 "substrate-runtime-std 0.1.0",
 "twox-hash 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
 "uint 0.1.2 (git+https://github.com/rphmeier/primitives.git?branch=compile-for-wasm)",
- "wasmi 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "wasmi 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]

 [[package]]
@@ -846,7 +846,7 @@ dependencies = [
 "substrate-primitives 0.1.0",
 "substrate-runtime-io 0.1.0",
 "substrate-runtime-std 0.1.0",
- "wasmi 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "wasmi 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]

 [[package]]
@@ -1107,7 +1107,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"

 [[package]]
 name = "wasmi"
-version = "0.3.0"
+version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
 "byteorder 1.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1231,7 +1231,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum untrusted 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "f392d7819dbe58833e26872f5f6f0d68b7bbbe90fc3667e98731c4a15ad9a7ae"
 "checksum utf8-ranges 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "662fab6525a98beff2921d7f61a39e7d59e0b425ebc7d0d9e66d316e55124122"
 "checksum void 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "6a02e4885ed3bc0f2de90ea6dd45ebcbb66dacffe03547fadbb0eeae2770887d"
-"checksum wasmi 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "9b4a6d379e9332b1b1f52c5a87f2481c85c7c931d8ec411963dfb8f26b1ec1e3"
+"checksum wasmi 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "522fe3fdd44a56f25cd5ddcd8ccdb1cf2e982ceb28fcb00f41d8a018ae5245a8"
 "checksum winapi 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)" = "04e3bd221fcbe8a271359c04f21a76db7d0c6028862d1bb5512d85e1e2eb5bb3"
 "checksum winapi-i686-pc-windows-gnu 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
 "checksum winapi-x86_64-pc-windows-gnu 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"
@@ -60,6 +60,7 @@ extern crate polkadot_primitives;
 extern crate log;

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

@@ -68,12 +69,36 @@ use client::BlockchainEvents;
 use polkadot_api::PolkadotApi;
 use polkadot_primitives::{AccountId, BlockId, SessionKey};
 use polkadot_primitives::parachain::{self, BlockData, DutyRoster, HeadData, ConsolidatedIngress, Message, Id as ParaId};
-use polkadot_cli::{ServiceComponents, Service, CustomConfiguration, VersionInfo};
+use polkadot_cli::{ServiceComponents, Service, CustomConfiguration};
 use polkadot_cli::{Worker, IntoExit};
 use tokio::timer::Deadline;

+pub use polkadot_cli::VersionInfo;
+
 const COLLATION_TIMEOUT: Duration = Duration::from_secs(30);

+/// Error to return when the head data was invalid.
+#[derive(Clone, Copy, Debug)]
+pub struct InvalidHead;
+
+/// Collation errors.
+#[derive(Debug)]
+pub enum Error<R> {
+	/// Error on the relay-chain side of things.
+	Polkadot(R),
+	/// Error on the collator side of things.
+	Collator(InvalidHead),
+}
+
+impl<R: fmt::Display> fmt::Display for Error<R> {
+	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+		match *self {
+			Error::Polkadot(ref err) => write!(f, "Polkadot node error: {}", err),
+			Error::Collator(_) => write!(f, "Collator node error: Invalid head data"),
+		}
+	}
+}
+
 /// Parachain context needed for collation.
 ///
 /// This can be implemented through an externally attached service or a stub.
@@ -84,7 +109,7 @@ pub trait ParachainContext: Clone {
 		&self,
 		last_head: HeadData,
 		ingress: I,
-	) -> (BlockData, HeadData);
+	) -> Result<(BlockData, HeadData), InvalidHead>;
 }

 /// Relay chain context needed to collate.
@@ -154,18 +179,18 @@ pub fn collate<'a, R, P>(
 	para_context: P,
 	key: Arc<ed25519::Pair>,
 )
-	-> impl Future<Item=parachain::Collation, Error=R::Error> + 'a
+	-> impl Future<Item=parachain::Collation, Error=Error<R::Error>> + 'a
 	where
 		R: RelayChainContext + 'a,
 		R::Error: 'a,
 		R::FutureEgress: 'a,
 		P: ParachainContext + 'a,
 {
-	collate_ingress(relay_context).map(move |ingress| {
+	collate_ingress(relay_context).map_err(Error::Polkadot).and_then(move |ingress| {
 		let (block_data, head_data) = para_context.produce_candidate(
 			last_head,
 			ingress.0.iter().flat_map(|&(id, ref msgs)| msgs.iter().cloned().map(move |msg| (id, msg)))
-		);
+		).map_err(Error::Collator)?;

 		let block_data_hash = block_data.hash();
 		let signature = key.sign(&block_data_hash.0[..]).into();
@@ -181,10 +206,10 @@ pub fn collate<'a, R, P>(
 			block_data_hash,
 		};

-		parachain::Collation {
+		Ok(parachain::Collation {
 			receipt,
 			block_data,
-		}
+		})
 	})
 }

@@ -248,7 +273,7 @@ impl<P, E> Worker for CollationNode<P, E> where
 					($e:expr) => {
 						match $e {
 							Ok(x) => x,
-							Err(e) => return future::Either::A(future::err(e)),
+							Err(e) => return future::Either::A(future::err(Error::Polkadot(e))),
 						}
 					}
 				}
@@ -323,17 +348,19 @@ fn compute_targets(para_id: ParaId, session_keys: &[SessionKey], roster: DutyRos
 ///
 /// Provide a future which resolves when the node should exit.
 /// This function blocks until done.
-pub fn run_collator<P, E>(
+pub fn run_collator<P, E, I, ArgT>(
 	parachain_context: P,
 	para_id: ParaId,
 	exit: E,
 	key: Arc<ed25519::Pair>,
-	args: Vec<::std::ffi::OsString>,
+	args: I,
 	version: VersionInfo,
 ) -> polkadot_cli::error::Result<()> where
 	P: ParachainContext + Send + 'static,
 	E: IntoFuture<Item=(),Error=()>,
 	E::Future: Send + Clone + 'static,
+	I: IntoIterator<Item=ArgT>,
+	ArgT: Into<std::ffi::OsString> + Clone,
 {
 	let node_logic = CollationNode { parachain_context, exit: exit.into_future(), para_id, key };
 	polkadot_cli::run(args, node_logic, version)
@@ -273,8 +273,13 @@ impl<C, N, P> bft::Environment<Block> for ProposerFactory<C, N, P>
 			sign_with.public().into(),
 		)?;

+		info!("Starting consensus session on top of parent {:?}. Local parachain duty is {:?}",
+			parent_hash, local_duty.validation);
+
 		let active_parachains = self.client.active_parachains(&id)?;

+		debug!(target: "consensus", "Active parachains: {:?}", active_parachains);
+
 		let n_parachains = active_parachains.len();
 		let table = Arc::new(SharedTable::new(group_info, sign_with.clone(), parent_hash));
 		let (router, input, output) = self.network.communication_for(
@@ -143,6 +143,7 @@ impl SharedTableInner {
 						fetch_block_data,
 						fetch_extrinsic,
 						evaluate: checking_validity,
+						ensure_available: checking_availability,
 					})
 				}
 			}
@@ -206,6 +207,7 @@ struct Work<D: Future, E: Future> {
 	fetch_block_data: future::Fuse<D>,
 	fetch_extrinsic: Option<future::Fuse<E>>,
 	evaluate: bool,
+	ensure_available: bool,
 }

 /// Primed statement producer.
@@ -235,31 +237,35 @@ impl<D, E, C, Err> Future for PrimedStatementProducer<D, E, C>
 				});

 				let hash = work.candidate_receipt.hash();
+
+				debug!(target: "consensus", "Making validity statement about candidate {}: is_good? {:?}", hash, is_good);
 				self.inner.produced_statements.validity = match is_good {
 					Some(true) => Some(GenericStatement::Valid(hash)),
 					Some(false) => Some(GenericStatement::Invalid(hash)),
 					None => None,
 				};
+
+				work.evaluate = false;
 			}
 		}

-		if let Some(ref mut fetch_extrinsic) = work.fetch_extrinsic {
-			if let Async::Ready(extrinsic) = fetch_extrinsic.poll()? {
+		if let Async::Ready(Some(extrinsic)) = work.fetch_extrinsic.poll()? {
+			if work.ensure_available {
+				let hash = work.candidate_receipt.hash();
+				debug!(target: "consensus", "Claiming candidate {} available.", hash);
+
+				// TODO: actually wait for block data and then ensure availability.
 				self.inner.produced_statements.extrinsic = Some(extrinsic);
+				self.inner.produced_statements.availability =
+					Some(GenericStatement::Available(hash));
+
+				work.ensure_available = false;
 			}
 		}

-		let done = self.inner.produced_statements.block_data.is_some() && {
-			if work.evaluate {
-				true
-			} else if self.inner.produced_statements.extrinsic.is_some() {
-				self.inner.produced_statements.availability =
-					Some(GenericStatement::Available(work.candidate_receipt.hash()));
-
-				true
-			} else {
-				false
-			}
+		let done = match (work.evaluate, work.ensure_available) {
+			(false, false) => true,
+			_ => false,
 		};

 		if done {
@@ -356,10 +362,25 @@ impl SharedTable {
 	}

 	/// Sign and import a local statement.
-	pub fn sign_and_import(&self, statement: table::Statement) -> SignedStatement {
-		let proposed_digest = match statement {
-			GenericStatement::Candidate(ref c) => Some(c.hash()),
-			_ => None,
+	///
+	/// For candidate statements, this may also produce a second signed statement
+	/// concerning the availability of the candidate data.
+	pub fn sign_and_import(&self, statement: table::Statement)
+		-> (SignedStatement, Option<SignedStatement>)
+	{
+		let (proposed_digest, availability) = match statement {
+			GenericStatement::Candidate(ref c) => {
+				let mut availability = None;
+				let hash = c.hash();
+
+				// TODO: actually store the data in an availability store of some kind.
+				if self.context.is_availability_guarantor_of(&self.context.local_id(), &c.parachain_index) {
+					availability = Some(self.context.sign_statement(GenericStatement::Available(hash)));
+				}
+
+				(Some(hash), availability)
+			}
+			_ => (None, None),
 		};

 		let signed_statement = self.context.sign_statement(statement);
@@ -370,7 +391,13 @@ impl SharedTable {
 		}

 		inner.table.import_statement(&*self.context, signed_statement.clone());
-		signed_statement
+
+		// ensure the availability statement is imported after the candidate.
+		if let Some(a) = availability.clone() {
+			inner.table.import_statement(&*self.context, a);
+		}
+
+		(signed_statement, availability)
 	}

 	/// Execute a closure using a specific candidate.
@@ -543,5 +570,6 @@ mod tests {

 		assert!(producer.work.fetch_extrinsic.is_some(), "should fetch extrinsic when guaranteeing availability");
 		assert!(!producer.work.evaluate, "should not evaluate validity");
+		assert!(producer.work.ensure_available);
 	}
 }
@@ -176,6 +176,7 @@ impl<P: LocalPolkadotApi + Send + Sync + 'static> MessageProcessTask<P> {
 				}
 			}
 			ConsensusMessage::ChainSpecific(msg, _) => {
+				debug!(target: "consensus", "Processing consensus statement for live consensus");
 				if let Some(Message::Statement(parent_hash, statement)) = Decode::decode(&mut msg.as_slice()) {
 					if ::polkadot_consensus::check_statement(&statement.statement, &statement.signature, statement.sender, &parent_hash) {
 						self.table_router.import_statement(statement);
@@ -111,10 +111,36 @@ struct BlockDataRequest {
 	sender: oneshot::Sender<BlockData>,
 }

+// ensures collator-protocol messages are sent in correct order.
+// session key must be sent before collator role.
+enum CollatorState {
+	Fresh,
+	RolePending(Role),
+	Primed,
+}
+
+impl CollatorState {
+	fn send_key<F: FnMut(Message)>(&mut self, key: SessionKey, mut f: F) {
+		f(Message::SessionKey(key));
+		if let CollatorState::RolePending(role) = ::std::mem::replace(self, CollatorState::Primed) {
+			f(Message::CollatorRole(role));
+		}
+	}
+
+	fn set_role<F: FnMut(Message)>(&mut self, role: Role, mut f: F) {
+		if let CollatorState::Primed = *self {
+			f(Message::CollatorRole(role));
+		} else {
+			*self = CollatorState::RolePending(role);
+		}
+	}
+}
+
 struct PeerInfo {
 	collating_for: Option<(AccountId, ParaId)>,
 	validator_key: Option<SessionKey>,
 	claimed_validator: bool,
+	collator_state: CollatorState,
 }

 #[derive(Default)]
@@ -281,8 +307,8 @@ impl PolkadotProtocol {
 		}
 	}

-	/// Send a statement to a validator.
-	fn send_statement(&mut self, ctx: &mut Context<Block>, _val: SessionKey, parent_hash: Hash, statement: SignedStatement) {
+	/// Gossip a consensus statement.
+	fn gossip_statement(&mut self, ctx: &mut Context<Block>, parent_hash: Hash, statement: SignedStatement) {
 		// TODO: something more targeted than gossip.
 		let raw = Message::Statement(parent_hash, statement).encode();
 		self.consensus_gossip.multicast_chain_specific(ctx, raw, parent_hash);
@@ -309,14 +335,14 @@ impl PolkadotProtocol {
 		let old_data = self.live_consensus.as_ref().map(|c| (c.parent_hash, c.local_session_key));

 		if Some(&consensus.local_session_key) != old_data.as_ref().map(|&(_, ref key)| key) {
-			for (id, _) in self.peers.iter()
+			for (id, peer_data) in self.peers.iter_mut()
 				.filter(|&(_, ref info)| info.claimed_validator || info.collating_for.is_some())
 			{
-				send_polkadot_message(
+				peer_data.collator_state.send_key(consensus.local_session_key, |msg| send_polkadot_message(
 					ctx,
 					*id,
-					Message::SessionKey(consensus.local_session_key)
-				);
+					msg
+				));
 			}
 		}

@@ -452,12 +478,15 @@ impl PolkadotProtocol {
 			}
 		};

+		debug!(target: "p_net", "New collator role {:?} from {}", role, who);
+
 		match info.validator_key {
 			None => ctx.report_peer(
 				who,
 				Severity::Bad("Sent collator role without registering first as validator"),
 			),
 			Some(key) => for (relay_parent, collation) in self.local_collations.note_validator_role(key, role) {
+				debug!(target: "p_net", "Broadcasting collation on relay parent {:?}", relay_parent);
 				send_polkadot_message(
 					ctx,
 					who,
@@ -481,38 +510,41 @@ impl Specialization<Block> for PolkadotProtocol {
 			}
 		};

+		let validator = status.roles.contains(substrate_network::Roles::AUTHORITY);
+		let send_key = validator || local_status.collating_for.is_some();
+
+		let mut peer_info = PeerInfo {
+			collating_for: local_status.collating_for,
+			validator_key: None,
+			claimed_validator: validator,
+			collator_state: CollatorState::Fresh,
+		};
+
 		if let Some((ref acc_id, ref para_id)) = local_status.collating_for {
-			if self.collator_peer_id(acc_id.clone()).is_some() {
+			if self.collator_peer(acc_id.clone()).is_some() {
 				ctx.report_peer(who, Severity::Useless("Unknown Polkadot-specific reason"));
 				return
 			}

 			let collator_role = self.collators.on_new_collator(acc_id.clone(), para_id.clone());
-			send_polkadot_message(
+
+			peer_info.collator_state.set_role(collator_role, |msg| send_polkadot_message(
 				ctx,
 				who,
-				Message::CollatorRole(collator_role),
-			);
+				msg,
+			));
 		}

-		let validator = status.roles.contains(substrate_network::Roles::AUTHORITY);
-		let send_key = validator || local_status.collating_for.is_some();
-
-		self.peers.insert(who, PeerInfo {
-			collating_for: local_status.collating_for,
-			validator_key: None,
-			claimed_validator: validator,
-		});
-
-		self.consensus_gossip.new_peer(ctx, who, status.roles);
 		if let (true, &Some(ref consensus)) = (send_key, &self.live_consensus) {
-			send_polkadot_message(
+			peer_info.collator_state.send_key(consensus.local_session_key, |msg| send_polkadot_message(
 				ctx,
 				who,
-				Message::SessionKey(consensus.local_session_key)
-			);
+				msg,
+			));
 		}

+		self.peers.insert(who, peer_info);
+		self.consensus_gossip.new_peer(ctx, who, status.roles);
 		self.dispatch_pending_requests(ctx);
 	}

@@ -520,14 +552,14 @@ impl Specialization<Block> for PolkadotProtocol {
 		if let Some(info) = self.peers.remove(&who) {
 			if let Some((acc_id, _)) = info.collating_for {
 				let new_primary = self.collators.on_disconnect(acc_id)
-					.and_then(|new_primary| self.collator_peer_id(new_primary));
+					.and_then(|new_primary| self.collator_peer(new_primary));

-				if let Some(new_primary) = new_primary {
-					send_polkadot_message(
+				if let Some((new_primary, primary_info)) = new_primary {
+					primary_info.collator_state.set_role(Role::Primary, |msg| send_polkadot_message(
 						ctx,
 						new_primary,
-						Message::CollatorRole(Role::Primary),
-					)
+						msg,
+					));
 				}
 			}

@@ -592,12 +624,12 @@ impl Specialization<Block> for PolkadotProtocol {
 		for collator_action in self.collators.maintain_peers() {
 			match collator_action {
 				Action::Disconnect(collator) => self.disconnect_bad_collator(ctx, collator),
-				Action::NewRole(account_id, role) => if let Some(collator) = self.collator_peer_id(account_id) {
-					send_polkadot_message(
+				Action::NewRole(account_id, role) => if let Some((collator, info)) = self.collator_peer(account_id) {
+					info.collator_state.set_role(role, |msg| send_polkadot_message(
 						ctx,
 						collator,
-						Message::CollatorRole(role),
-					)
+						msg,
+					))
 				},
 			}
 		}
@@ -622,6 +654,7 @@ impl PolkadotProtocol {
 				Some((ref acc_id, ref para_id)) => {
 					let structurally_valid = para_id == &collation_para && acc_id == &collated_acc;
 					if structurally_valid && collation.receipt.check_signature().is_ok() {
+						debug!(target: "p_net", "Received collation for parachain {:?} from peer {}", para_id, from);
 						self.collators.on_collation(acc_id.clone(), relay_parent, collation)
 					} else {
 						ctx.report_peer(from, Severity::Bad("Sent malformed collation"))
@@ -633,27 +666,28 @@ impl PolkadotProtocol {

 	fn await_collation(&mut self, relay_parent: Hash, para_id: ParaId) -> oneshot::Receiver<Collation> {
 		let (tx, rx) = oneshot::channel();
+		debug!(target: "p_net", "Attempting to get collation for parachain {:?} on relay parent {:?}", para_id, relay_parent);
 		self.collators.await_collation(relay_parent, para_id, tx);
 		rx
 	}

 	// get connected peer with given account ID for collation.
-	fn collator_peer_id(&self, account_id: AccountId) -> Option<NodeIndex> {
+	fn collator_peer(&mut self, account_id: AccountId) -> Option<(NodeIndex, &mut PeerInfo)> {
 		let check_info = |info: &PeerInfo| info
 			.collating_for
 			.as_ref()
 			.map_or(false, |&(ref acc_id, _)| acc_id == &account_id);

 		self.peers
-			.iter()
-			.filter(|&(_, info)| check_info(info))
-			.map(|(who, _)| *who)
+			.iter_mut()
+			.filter(|&(_, ref info)| check_info(&**info))
+			.map(|(who, info)| (*who, info))
 			.next()
 	}

 	// disconnect a collator by account-id.
-	fn disconnect_bad_collator(&self, ctx: &mut Context<Block>, account_id: AccountId) {
-		if let Some(who) = self.collator_peer_id(account_id) {
+	fn disconnect_bad_collator(&mut self, ctx: &mut Context<Block>, account_id: AccountId) {
+		if let Some((who, _)) = self.collator_peer(account_id) {
 			ctx.report_peer(who, Severity::Bad("Consensus layer determined the given collator misbehaved"))
 		}
 	}
@@ -668,13 +702,19 @@ impl PolkadotProtocol {
 		targets: HashSet<SessionKey>,
 		collation: Collation,
 	) {
+		debug!(target: "p_net", "Importing local collation on relay parent {:?} and parachain {:?}",
+			relay_parent, collation.receipt.parachain_index);
+
 		for (primary, cloned_collation) in self.local_collations.add_collation(relay_parent, targets, collation.clone()) {
 			match self.validators.get(&primary) {
-				Some(who) => send_polkadot_message(
-					ctx,
-					*who,
-					Message::Collation(relay_parent, cloned_collation),
-				),
+				Some(who) => {
+					debug!(target: "p_net", "Sending local collation to {:?}", primary);
+					send_polkadot_message(
+						ctx,
+						*who,
+						Message::Collation(relay_parent, cloned_collation),
+					)
+				},
 				None =>
 					warn!(target: "polkadot_network", "Encountered tracked but disconnected validator {:?}", primary),
 			}
@@ -25,7 +25,7 @@
 use polkadot_api::{PolkadotApi, LocalPolkadotApi};
 use polkadot_consensus::{SharedTable, TableRouter, SignedStatement, GenericStatement, StatementProducer};
 use polkadot_primitives::{Hash, BlockId, SessionKey};
-use polkadot_primitives::parachain::{BlockData, Extrinsic, CandidateReceipt, Id as ParaId};
+use polkadot_primitives::parachain::{BlockData, Extrinsic, CandidateReceipt};

 use futures::prelude::*;
 use tokio::runtime::TaskExecutor;
@@ -89,14 +89,16 @@ impl<P: PolkadotApi> Clone for Router<P> {
 impl<P: LocalPolkadotApi + Send + Sync + 'static> Router<P> {
 	/// Import a statement whose signature has been checked already.
 	pub(crate) fn import_statement(&self, statement: SignedStatement) {
+		trace!(target: "p_net", "importing consensus statement {:?}", statement.statement);
+
 		// defer any statements for which we haven't imported the candidate yet
-		let (c_hash, parachain_index) = {
+		let c_hash = {
 			let candidate_data = match statement.statement {
-				GenericStatement::Candidate(ref c) => Some((c.hash(), c.parachain_index)),
+				GenericStatement::Candidate(ref c) => Some(c.hash()),
 				GenericStatement::Valid(ref hash)
 					| GenericStatement::Invalid(ref hash)
 					| GenericStatement::Available(ref hash)
-					=> self.table.with_candidate(hash, |c| c.map(|c| (*hash, c.parachain_index))),
+					=> self.table.with_candidate(hash, |c| c.map(|_| *hash)),
 			};
 			match candidate_data {
 				Some(x) => x,
@@ -115,6 +117,7 @@ impl<P: LocalPolkadotApi + Send + Sync + 'static> Router<P> {
 		};

 		// prepend the candidate statement.
+		debug!(target: "consensus", "Importing statements about candidate {:?}", c_hash);
 		statements.insert(0, statement);
 		let producers: Vec<_> = self.table.import_remote_statements(
 			self,
@@ -122,17 +125,16 @@ impl<P: LocalPolkadotApi + Send + Sync + 'static> Router<P> {
 		);
 		// dispatch future work as necessary.
 		for (producer, statement) in producers.into_iter().zip(statements) {
-			let producer = match producer {
-				Some(p) => p,
-				None => continue, // statement redundant
-			};
-
 			self.knowledge.lock().note_statement(statement.sender, &statement.statement);
-			self.dispatch_work(c_hash, producer, parachain_index);
+
+			if let Some(producer) = producer {
+				trace!(target: "consensus", "driving statement work to completion");
+				self.dispatch_work(c_hash, producer);
+			}
 		}
 	}

-	fn dispatch_work<D, E>(&self, candidate_hash: Hash, producer: StatementProducer<D, E>, parachain: ParaId) where
+	fn dispatch_work<D, E>(&self, candidate_hash: Hash, producer: StatementProducer<D, E>) where
 		D: Future<Item=BlockData,Error=()> + Send + 'static,
 		E: Future<Item=Extrinsic,Error=()> + Send + 'static,
 	{
@@ -160,13 +162,13 @@ impl<P: LocalPolkadotApi + Send + Sync + 'static> Router<P> {

 			// propagate the statements
 			if let Some(validity) = produced.validity {
-				let signed = table.sign_and_import(validity.clone());
-				route_statement(&*network, &*table, parachain, parent_hash, signed);
+				let signed = table.sign_and_import(validity.clone()).0;
+				network.with_spec(|spec, ctx| spec.gossip_statement(ctx, parent_hash, signed));
 			}

 			if let Some(availability) = produced.availability {
-				let signed = table.sign_and_import(availability);
-				route_statement(&*network, &*table, parachain, parent_hash, signed);
+				let signed = table.sign_and_import(availability).0;
+				network.with_spec(|spec, ctx| spec.gossip_statement(ctx, parent_hash, signed));
 			}
 		});

@@ -182,11 +184,15 @@ impl<P: LocalPolkadotApi + Send> TableRouter for Router<P> {
 	fn local_candidate(&self, receipt: CandidateReceipt, block_data: BlockData, extrinsic: Extrinsic) {
 		// give to network to make available.
 		let hash = receipt.hash();
-		let para_id = receipt.parachain_index;
-		let signed = self.table.sign_and_import(GenericStatement::Candidate(receipt));
+		let (candidate, availability) = self.table.sign_and_import(GenericStatement::Candidate(receipt));

 		self.knowledge.lock().note_candidate(hash, Some(block_data), Some(extrinsic));
-		route_statement(&*self.network, &*self.table, para_id, self.parent_hash, signed);
+		self.network.with_spec(|spec, ctx| {
+			spec.gossip_statement(ctx, self.parent_hash, candidate);
+			if let Some(availability) = availability {
+				spec.gossip_statement(ctx, self.parent_hash, availability);
+			}
+		});
 	}

 	fn fetch_block_data(&self, candidate: &CandidateReceipt) -> BlockDataReceiver {
@@ -217,32 +223,6 @@ impl Future for BlockDataReceiver {
 	}
 }

-// get statement to relevant validators.
-fn route_statement(network: &NetworkService, table: &SharedTable, para_id: ParaId, parent_hash: Hash, statement: SignedStatement) {
-	let broadcast = |i: &mut Iterator<Item=&SessionKey>| {
-		let local_key = table.session_key();
-		network.with_spec(|spec, ctx| {
-			for val in i.filter(|&x| x != &local_key) {
-				spec.send_statement(ctx, *val, parent_hash, statement.clone());
-			}
-		});
-	};
-
-	let g_info = table
-		.group_info()
-		.get(&para_id)
-		.expect("statements only produced about groups which exist");
-
-	match statement.statement {
-		GenericStatement::Candidate(_) =>
-			broadcast(&mut g_info.validity_guarantors.iter().chain(g_info.availability_guarantors.iter())),
-		GenericStatement::Valid(_) | GenericStatement::Invalid(_) =>
-			broadcast(&mut g_info.validity_guarantors.iter()),
-		GenericStatement::Available(_) =>
-			broadcast(&mut g_info.availability_guarantors.iter()),
-	}
-}
-
 // A unique trace for valid statements issued by a validator.
 #[derive(Hash, PartialEq, Eq, Clone, Debug)]
 enum StatementTrace {
@@ -1,25 +0,0 @@
-[package]
-name = "basic_add"
-version = "0.1.0"
-authors = ["Parity Technologies <admin@parity.io>"]
-description = "Test parachain which adds to a number as its state transition"
-
-[lib]
-crate-type = ["cdylib"]
-
-[dependencies]
-polkadot-parachain = { path = "../../", default-features = false }
-wee_alloc = "0.4.1"
-tiny-keccak = "1.4"
-pwasm-libc = "0.2"
-
-[features]
-default = ["std"]
-std = ["polkadot-parachain/std"]
-
-[profile.release]
-panic = "abort"
-lto = true
-
-[workspace]
-members = []
@@ -1,12 +0,0 @@
-#!/usr/bin/env bash
-set -e
-
-# Make LLD produce a binary that imports memory from the outside environment.
-export RUSTFLAGS="-C link-arg=--import-memory"
-
-cargo +nightly build --target=wasm32-unknown-unknown --release --no-default-features
-
-for i in basic_add
-do
-	wasm-gc target/wasm32-unknown-unknown/release/$i.wasm target/wasm32-unknown-unknown/release/$i.compact.wasm
-done
@@ -1,142 +0,0 @@
-// Copyright 2017 Parity Technologies (UK) Ltd.
-// This file is part of Polkadot.
-
-// Polkadot is free software: you can redistribute it and/or modify
-// it under the terms of the GNU General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-
-// Polkadot is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-// GNU General Public License for more details.
-
-// You should have received a copy of the GNU General Public License
-// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
-
-//! Basic parachain that adds a number as part of its state.
-
-#![cfg_attr(not(feature = "std"), no_std)]
-#![cfg_attr(
-	not(feature = "std"),
-	feature(
-		alloc, core_intrinsics, lang_items, panic_implementation, core_panic_info,
-		alloc_error_handler
-	)
-)]
-
-#[cfg(not(feature = "std"))]
-extern crate alloc;
-
-extern crate polkadot_parachain as parachain;
-extern crate wee_alloc;
-extern crate tiny_keccak;
-extern crate pwasm_libc;
-
-use parachain::codec::{Decode, Encode, Input, Output};
-
-#[cfg(not(feature = "std"))]
-mod wasm;
-
-#[cfg(not(feature = "std"))]
-pub use wasm::*;
-
-// Define global allocator.
-#[cfg(not(feature = "std"))]
-#[global_allocator]
-static ALLOC: wee_alloc::WeeAlloc = wee_alloc::WeeAlloc::INIT;
-
-// Head data for this parachain.
-#[derive(Default, Clone)]
-struct HeadData {
-	// Block number
-	number: u64,
-	// parent block keccak256
-	parent_hash: [u8; 32],
-	// hash of post-execution state.
-	post_state: [u8; 32],
-}
-
-impl Encode for HeadData {
-	fn encode_to<T: Output>(&self, dest: &mut T) {
-		dest.push(&self.number);
-		dest.push(&self.parent_hash);
-		dest.push(&self.post_state);
-	}
-}
-
-impl Decode for HeadData {
-	fn decode<I: Input>(input: &mut I) -> Option<Self> {
-		Some(HeadData {
-			number: Decode::decode(input)?,
-			parent_hash: Decode::decode(input)?,
-			post_state: Decode::decode(input)?,
-		})
-	}
-}
-
-// Block data for this parachain.
-#[derive(Default, Clone)]
-struct BlockData {
-	// State to begin from.
-	state: u64,
-	// Amount to add (overflowing)
-	add: u64,
-}
-
-impl Encode for BlockData {
-	fn encode_to<T: Output>(&self, dest: &mut T) {
-		dest.push(&self.state);
-		dest.push(&self.add);
-	}
-}
-
-impl Decode for BlockData {
-	fn decode<I: Input>(input: &mut I) -> Option<Self> {
-		Some(BlockData {
-			state: Decode::decode(input)?,
-			add: Decode::decode(input)?,
-		})
-	}
-}
-
-#[cfg(test)]
-mod tests {
-	use super::*;
-	use parachain::ValidationParams;
-
-	const TEST_CODE: &[u8] = include_bytes!("../wasm/test.wasm");
-
-	fn hash_state(state: u64) -> [u8; 32] {
-		::tiny_keccak::keccak256(state.encode().as_slice())
-	}
-
-	fn hash_head(head: &HeadData) -> [u8; 32] {
-		::tiny_keccak::keccak256(head.encode().as_slice())
-	}
-
-	#[test]
-	fn execute_good_on_parent() {
-		let parent_head = HeadData {
-			number: 0,
-			parent_hash: [0; 32],
-			post_state: hash_state(0),
-		};
-
-		let block_data = BlockData {
-			state: 0,
-			add: 512,
-		};
-
-		let ret = parachain::wasm::validate_candidate(TEST_CODE, ValidationParams {
-			parent_head: parent_head.encode(),
-			block_data: block_data.encode(),
-		}).unwrap();
-
-		let new_head = HeadData::decode(&mut &ret.head_data[..]).unwrap();
-
-		assert_eq!(new_head.number, 1);
-		assert_eq!(new_head.parent_hash, hash_head(&parent_head));
-		assert_eq!(new_head.post_state, hash_state(512));
-	}
-}
@@ -76,7 +76,7 @@ impl Decode for BlockData {
 	}
 }

-const TEST_CODE: &[u8] = include_bytes!("res/basic_add.wasm");
+const TEST_CODE: &[u8] = include_bytes!("res/adder.wasm");

 fn hash_state(state: u64) -> [u8; 32] {
 	::tiny_keccak::keccak256(state.encode().as_slice())
@@ -194,8 +194,8 @@ impl<T: Trait> Executable for Module<T> {
 #[serde(rename_all = "camelCase")]
 #[serde(deny_unknown_fields)]
 pub struct GenesisConfig<T: Trait> {
-	/// The initial parachains, mapped to code.
-	pub parachains: Vec<(Id, Vec<u8>)>,
+	/// The initial parachains, mapped to code and initial head data
+	pub parachains: Vec<(Id, Vec<u8>, Vec<u8>)>,
 	/// Phantom data.
 	#[serde(skip)]
 	pub phantom: PhantomData<T>,
@@ -218,18 +218,21 @@ impl<T: Trait> runtime_primitives::BuildStorage for GenesisConfig<T>
 		use std::collections::HashMap;
 		use codec::Encode;

-		self.parachains.sort_unstable_by_key(|&(ref id, _)| id.clone());
-		self.parachains.dedup_by_key(|&mut (ref id, _)| id.clone());
+		self.parachains.sort_unstable_by_key(|&(ref id, _, _)| id.clone());
+		self.parachains.dedup_by_key(|&mut (ref id, _, _)| id.clone());

-		let only_ids: Vec<_> = self.parachains.iter().map(|&(ref id, _)| id).cloned().collect();
+		let only_ids: Vec<_> = self.parachains.iter().map(|&(ref id, _, _)| id).cloned().collect();

 		let mut map: HashMap<_, _> = map![
 			Self::hash(<Parachains<T>>::key()).to_vec() => only_ids.encode()
 		];

-		for (id, code) in self.parachains {
-			let key = Self::hash(&<Code<T>>::key_for(&id)).to_vec();
-			map.insert(key, code.encode());
+		for (id, code, genesis) in self.parachains {
+			let code_key = Self::hash(&<Code<T>>::key_for(&id)).to_vec();
+			let head_key = Self::hash(&<Heads<T>>::key_for(&id)).to_vec();
+
+			map.insert(code_key, code.encode());
+			map.insert(head_key, genesis.encode());
 		}

 		Ok(map.into())
@@ -280,7 +283,7 @@ mod tests {

 	type Parachains = Module<Test>;

-	fn new_test_ext(parachains: Vec<(Id, Vec<u8>)>) -> runtime_io::TestExternalities {
+	fn new_test_ext(parachains: Vec<(Id, Vec<u8>, Vec<u8>)>) -> runtime_io::TestExternalities {
 		let mut t = system::GenesisConfig::<Test>::default().build_storage().unwrap();
 		t.extend(consensus::GenesisConfig::<Test>{
 			code: vec![],
@@ -301,8 +304,8 @@ mod tests {
 	#[test]
 	fn active_parachains_should_work() {
 		let parachains = vec![
-			(5u32.into(), vec![1,2,3]),
-			(100u32.into(), vec![4,5,6]),
+			(5u32.into(), vec![1,2,3], vec![1]),
+			(100u32.into(), vec![4,5,6], vec![2]),
 		];

 		with_externalities(&mut new_test_ext(parachains), || {
@@ -315,8 +318,8 @@ mod tests {
 	#[test]
 	fn register_deregister() {
 		let parachains = vec![
-			(5u32.into(), vec![1,2,3]),
-			(100u32.into(), vec![4,5,6]),
+			(5u32.into(), vec![1,2,3], vec![1]),
+			(100u32.into(), vec![4,5,6], vec![2,]),
 		];

 		with_externalities(&mut new_test_ext(parachains), || {
@@ -340,8 +343,8 @@ mod tests {
 	#[test]
 	fn duty_roster_works() {
 		let parachains = vec![
-			(0u32.into(), vec![]),
-			(1u32.into(), vec![]),
+			(0u32.into(), vec![], vec![]),
+			(1u32.into(), vec![], vec![]),
 		];

 		with_externalities(&mut new_test_ext(parachains), || {
@@ -730,7 +730,7 @@ dependencies = [
 "substrate-runtime-std 0.1.0",
 "twox-hash 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
 "uint 0.1.2 (git+https://github.com/rphmeier/primitives.git?branch=compile-for-wasm)",
- "wasmi 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "wasmi 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]

 [[package]]
@@ -846,7 +846,7 @@ dependencies = [
 "substrate-primitives 0.1.0",
 "substrate-runtime-io 0.1.0",
 "substrate-runtime-std 0.1.0",
- "wasmi 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "wasmi 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]

 [[package]]
@@ -1107,7 +1107,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"

 [[package]]
 name = "wasmi"
-version = "0.3.0"
+version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
 "byteorder 1.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1231,7 +1231,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum untrusted 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "f392d7819dbe58833e26872f5f6f0d68b7bbbe90fc3667e98731c4a15ad9a7ae"
 "checksum utf8-ranges 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "662fab6525a98beff2921d7f61a39e7d59e0b425ebc7d0d9e66d316e55124122"
 "checksum void 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "6a02e4885ed3bc0f2de90ea6dd45ebcbb66dacffe03547fadbb0eeae2770887d"
-"checksum wasmi 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "9b4a6d379e9332b1b1f52c5a87f2481c85c7c931d8ec411963dfb8f26b1ec1e3"
+"checksum wasmi 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "522fe3fdd44a56f25cd5ddcd8ccdb1cf2e982ceb28fcb00f41d8a018ae5245a8"
 "checksum winapi 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)" = "04e3bd221fcbe8a271359c04f21a76db7d0c6028862d1bb5512d85e1e2eb5bb3"
 "checksum winapi-i686-pc-windows-gnu 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
 "checksum winapi-x86_64-pc-windows-gnu 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"
@@ -212,7 +212,7 @@ pub fn new_full(config: Configuration, executor: TaskExecutor)
 			consensus_net,
 			service.extrinsic_pool(),
 			executor,
-			::std::time::Duration::from_millis(4000), // TODO: dynamic
+			::std::time::Duration::from_secs(4), // TODO: dynamic
 			key,
 		))
 	} else {
@@ -302,13 +302,13 @@ impl<B, E, A> network::TransactionPool<Block> for TransactionPoolAdapter<B, E, A
 				Err(e) => match *e.kind() {
 					transaction_pool::ErrorKind::AlreadyImported(hash) => Some(hash[..].into()),
 					_ => {
-						debug!("Error adding transaction to the pool: {:?}", e);
+						debug!(target: "txpool", "Error adding transaction to the pool: {:?}", e);
 						None
 					},
 				}
 			}
 		} else {
-			debug!("Error decoding transaction");
+			debug!(target: "txpool", "Error decoding transaction");
 			None
 		}
 	}
@@ -0,0 +1,5 @@
+# Test Parachains
+
+Each parachain consists of three parts: a `#![no_std]` library with the main execution logic, a WASM crate which wraps this logic, and a collator node.
+
+Run `build.sh` in this directory to build all registered test parachains and copy the generated WASM to the `parachain/tests/res` folder.
@@ -0,0 +1,9 @@
+[package]
+name = "adder"
+version = "0.1.0"
+authors = ["Parity Technologies <admin@parity.io>"]
+description = "Test parachain which adds to a number as its state transition"
+
+[dependencies]
+polkadot-parachain = { path = "../../parachain/", default-features = false }
+tiny-keccak = "1.4"
@@ -0,0 +1,15 @@
+[package]
+name = "adder-collator"
+version = "0.1.0"
+authors = ["Parity Technologies <admin@parity.io>"]
+
+[dependencies]
+adder = { path = ".." }
+polkadot-parachain = { path = "../../../parachain" }
+polkadot-collator = { path = "../../../collator" }
+polkadot-primitives = { path = "../../../primitives" }
+ed25519 = { path = "../../../../substrate/ed25519" }
+parking_lot = "0.4"
+ctrlc = { git = "https://github.com/paritytech/rust-ctrlc.git" }
+futures = "0.1"
+exit-future = "0.1.2"
@@ -0,0 +1,145 @@
+// Copyright 2018 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Collator for polkadot
+
+extern crate adder;
+extern crate polkadot_parachain as parachain;
+extern crate polkadot_primitives as primitives;
+extern crate polkadot_collator as collator;
+extern crate ed25519;
+extern crate parking_lot;
+extern crate ctrlc;
+extern crate futures;
+extern crate exit_future;
+
+use std::cell::RefCell;
+use std::collections::HashMap;
+use std::sync::Arc;
+
+use adder::{HeadData as AdderHead, BlockData as AdderBody};
+use ed25519::Pair;
+use parachain::codec::{Encode, Decode};
+use primitives::parachain::{HeadData, BlockData, Id as ParaId, Message};
+use collator::{InvalidHead, ParachainContext, VersionInfo};
+use parking_lot::Mutex;
+
+const GENESIS: AdderHead = AdderHead {
+	number: 0,
+	parent_hash: [0; 32],
+	post_state: [1, 27, 77, 3, 221, 140, 1, 241, 4, 145, 67, 207, 156, 76, 129, 126, 75, 22, 127, 29, 27, 131, 229, 198, 240, 241, 13, 137, 186, 30, 123, 206],
+};
+
+const GENESIS_BODY: AdderBody = AdderBody {
+	state: 0,
+	add: 0,
+};
+
+#[derive(Clone)]
+struct AdderContext {
+	db: Arc<Mutex<HashMap<AdderHead, AdderBody>>>,
+}
+
+/// The parachain context.
+impl ParachainContext for AdderContext {
+	fn produce_candidate<I: IntoIterator<Item=(ParaId, Message)>>(
+		&self,
+		last_head: HeadData,
+		_ingress: I,
+	) -> Result<(BlockData, HeadData), InvalidHead>
+	{
+		let adder_head = AdderHead::decode(&mut &last_head.0[..])
+			.ok_or(InvalidHead)?;
+
+		let mut db = self.db.lock();
+
+		let last_body = if adder_head == GENESIS {
+			GENESIS_BODY
+		} else {
+			db.get(&adder_head)
+				.expect("All past bodies stored since this is the only collator")
+				.clone()
+		};
+
+		let next_body = AdderBody {
+			state: last_body.state.overflowing_add(last_body.add).0,
+			add: adder_head.number % 100,
+		};
+
+		let next_head = ::adder::execute(adder_head.hash(), adder_head, &next_body)
+			.expect("good execution params; qed");
+
+		let encoded_head = HeadData(next_head.encode());
+		let encoded_body = BlockData(next_body.encode());
+
+		println!("Created collation for #{}, post-state={}",
+			next_head.number, next_body.state.overflowing_add(next_body.add).0);
+
+		db.insert(next_head.clone(), next_body);
+		Ok((encoded_body, encoded_head))
+	}
+}
+
+fn main() {
+	let key = Arc::new(Pair::from_seed(&[1; 32]));
+	let id: ParaId = 100.into();
+
+	println!("Starting adder collator with genesis: ");
+
+	{
+		let encoded = GENESIS.encode();
+		println!("Dec: {:?}", encoded);
+		print!("Hex: 0x");
+		for byte in encoded {
+			print!("{:02x}", byte);
+		}
+
+		println!();
+	}
+
+	// can't use signal directly here because CtrlC takes only `Fn`.
+	let (exit_send, exit) = exit_future::signal();
+
+	let exit_send_cell = RefCell::new(Some(exit_send));
+	ctrlc::CtrlC::set_handler(move || {
+		if let Some(exit_send) = exit_send_cell.try_borrow_mut().expect("signal handler not reentrant; qed").take() {
+			exit_send.fire();
+		}
+	});
+
+	let context = AdderContext {
+		db: Arc::new(Mutex::new(HashMap::new())),
+	};
+
+	let res = ::collator::run_collator(
+		context,
+		id,
+		exit,
+		key,
+		::std::env::args(),
+		VersionInfo {
+			version: "<unknown>",
+			commit: "<unknown>",
+			executable_name: "adder-collator",
+			description: "collator for adder parachain",
+			author: "parity technologies",
+		}
+	);
+
+	if let Err(e) = res {
+		println!("{}", e);
+	}
+}
@@ -0,0 +1,110 @@
+// Copyright 2017 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Basic parachain that adds a number as part of its state.
+
+#![no_std]
+
+extern crate polkadot_parachain as parachain;
+extern crate tiny_keccak;
+
+use parachain::codec::{Decode, Encode, Input, Output};
+
+/// Head data for this parachain.
+#[derive(Default, Clone, Hash, Eq, PartialEq)]
+pub struct HeadData {
+	/// Block number
+	pub number: u64,
+	/// parent block keccak256
+	pub parent_hash: [u8; 32],
+	/// hash of post-execution state.
+	pub post_state: [u8; 32],
+}
+
+impl HeadData {
+	pub fn hash(&self) -> [u8; 32] {
+		::tiny_keccak::keccak256(&self.encode())
+	}
+}
+
+impl Encode for HeadData {
+	fn encode_to<T: Output>(&self, dest: &mut T) {
+		dest.push(&self.number);
+		dest.push(&self.parent_hash);
+		dest.push(&self.post_state);
+	}
+}
+
+impl Decode for HeadData {
+	fn decode<I: Input>(input: &mut I) -> Option<Self> {
+		Some(HeadData {
+			number: Decode::decode(input)?,
+			parent_hash: Decode::decode(input)?,
+			post_state: Decode::decode(input)?,
+		})
+	}
+}
+
+/// Block data for this parachain.
+#[derive(Default, Clone)]
+pub struct BlockData {
+	/// State to begin from.
+	pub state: u64,
+	/// Amount to add (overflowing)
+	pub add: u64,
+}
+
+impl Encode for BlockData {
+	fn encode_to<T: Output>(&self, dest: &mut T) {
+		dest.push(&self.state);
+		dest.push(&self.add);
+	}
+}
+
+impl Decode for BlockData {
+	fn decode<I: Input>(input: &mut I) -> Option<Self> {
+		Some(BlockData {
+			state: Decode::decode(input)?,
+			add: Decode::decode(input)?,
+		})
+	}
+}
+
+pub fn hash_state(state: u64) -> [u8; 32] {
+	::tiny_keccak::keccak256(state.encode().as_slice())
+}
+
+/// Start state mismatched with parent header's state hash.
+#[derive(Debug)]
+pub struct StateMismatch;
+
+/// Execute a block body on top of given parent head, producing new parent head
+/// if valid.
+pub fn execute(parent_hash: [u8; 32], parent_head: HeadData, block_data: &BlockData) -> Result<HeadData, StateMismatch> {
+	debug_assert_eq!(parent_hash, parent_head.hash());
+
+	if hash_state(block_data.state) != parent_head.post_state {
+		return Err(StateMismatch);
+	}
+
+	let new_state = block_data.state.overflowing_add(block_data.add).0;
+
+	Ok(HeadData {
+		number: parent_head.number + 1,
+		parent_hash,
+		post_state: hash_state(new_state),
+	})
+}
@@ -0,0 +1,20 @@
+[package]
+name = "adder-wasm"
+version = "0.1.0"
+authors = ["Parity Technologies <admin@parity.io>"]
+
+[dependencies]
+adder = { path = ".." }
+polkadot-parachain = { path = "../../../parachain", default-features = false }
+wee_alloc = { version = "0.4.1" }
+pwasm-libc = { version = "0.2" }
+tiny-keccak = "1.4"
+
+[lib]
+crate-type = ["cdylib"]
+
+[target.release]
+panic = "abort"
+lto = true
+
+[workspace]
@@ -14,12 +14,30 @@
 // You should have received a copy of the GNU General Public License
 // along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.

-//! Defines WASM module logic.
+//! WASM validation for adder parachain.

-use core::{intrinsics, panic, alloc};
-use parachain::{self, ValidationResult};
+#![no_std]
+
+#![feature(
+	alloc, core_intrinsics, lang_items, panic_implementation, core_panic_info,
+	alloc_error_handler
+)]
+
+extern crate alloc;
+extern crate wee_alloc;
+extern crate pwasm_libc;
+extern crate adder;
+extern crate polkadot_parachain as parachain;
+extern crate tiny_keccak;
+
+// Define global allocator.
+#[global_allocator]
+static ALLOC: wee_alloc::WeeAlloc = wee_alloc::WeeAlloc::INIT;
+
+use core::{intrinsics, panic};
+use parachain::ValidationResult;
 use parachain::codec::{Encode, Decode};
-use super::{HeadData, BlockData};
+use adder::{HeadData, BlockData};

 #[panic_implementation]
 #[no_mangle]
@@ -31,7 +49,7 @@ pub fn panic(_info: &panic::PanicInfo) -> ! {

 #[alloc_error_handler]
 #[no_mangle]
-pub fn oom(_: alloc::Layout) -> ! {
+pub fn oom(_: ::core::alloc::Layout) -> ! {
 	unsafe {
 		intrinsics::abort();
 	}
@@ -39,8 +57,6 @@ pub fn oom(_: alloc::Layout) -> ! {

 #[no_mangle]
 pub extern fn validate(offset: usize, len: usize) -> usize {
-	let hash_state = |state: u64| ::tiny_keccak::keccak256(state.encode().as_slice());
-
 	let params = unsafe { ::parachain::load_params(offset, len) };
 	let parent_head = HeadData::decode(&mut &params.parent_head[..])
 		.expect("invalid parent head format.");
@@ -48,14 +64,10 @@ pub extern fn validate(offset: usize, len: usize) -> usize {
 	let block_data = BlockData::decode(&mut &params.block_data[..])
 		.expect("invalid block data format.");

-	assert_eq!(hash_state(block_data.state), parent_head.post_state, "wrong post-state proof");
-	let new_state = block_data.state.saturating_add(block_data.add);
+	let parent_hash = ::tiny_keccak::keccak256(&params.parent_head[..]);

-	let new_head = HeadData {
-		number: parent_head.number + 1,
-		parent_hash: ::tiny_keccak::keccak256(&params.parent_head[..]),
-		post_state: hash_state(new_state),
-	};
-
-	parachain::write_result(ValidationResult { head_data: new_head.encode() })
+	match ::adder::execute(parent_hash, parent_head, &block_data) {
+		Ok(new_head) => parachain::write_result(ValidationResult { head_data: new_head.encode() }),
+		Err(_) => panic!("execution failure"),
+	}
 }
@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+set -e
+
+# Make LLD produce a binary that imports memory from the outside environment.
+export RUSTFLAGS="-C link-arg=--import-memory -C lto=fat -C panic=abort"
+
+for i in adder
+do
+	cd $i/wasm
+	cargo +nightly build --target=wasm32-unknown-unknown --release --no-default-features --target-dir target
+	wasm-gc target/wasm32-unknown-unknown/release/$i'_'wasm.wasm target/wasm32-unknown-unknown/release/$i.wasm
+	cp target/wasm32-unknown-unknown/release/$i.wasm ../../../parachain/tests/res/
+	rm -rf target
+	cd ../..
+done
@@ -124,7 +124,9 @@ impl<B: BlockT> ConsensusGossip<B> where B::Header: HeaderT<Number=u64> {

 	/// Handles incoming chain-specific message and repropagates
 	pub fn on_chain_specific(&mut self, protocol: &mut Context<B>, who: NodeIndex, message: Vec<u8>, parent_hash: B::Hash) {
+		debug!(target: "gossip", "received chain-specific gossip message");
 		if let Some((hash, message)) = self.handle_incoming(protocol, who, ConsensusMessage::ChainSpecific(message, parent_hash)) {
+			debug!(target: "gossip", "handled incoming chain-specific message");
 			// propagate to other peers.
 			self.multicast(protocol, message, Some(hash));
 		}
@@ -245,6 +247,7 @@ impl<B: BlockT> ConsensusGossip<B> where B::Header: HeaderT<Number=u64> {
 			peer.known_messages.insert(hash);
 			if let Some((sink, parent_hash)) = self.message_sink.take() {
 				if parent == parent_hash {
+					debug!(target: "gossip", "Pushing relevant consensus message to sink.");
 					if let Err(e) = sink.unbounded_send(message.clone()) {
 						trace!(target:"gossip", "Error broadcasting message notification: {:?}", e);
 					}
@@ -678,7 +678,7 @@ dependencies = [
 "substrate-runtime-std 0.1.0",
 "twox-hash 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
 "uint 0.1.2 (git+https://github.com/rphmeier/primitives.git?branch=compile-for-wasm)",
- "wasmi 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "wasmi 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]

 [[package]]
@@ -910,7 +910,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"

 [[package]]
 name = "wasmi"
-version = "0.3.0"
+version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
 "byteorder 1.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1034,7 +1034,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum untrusted 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "f392d7819dbe58833e26872f5f6f0d68b7bbbe90fc3667e98731c4a15ad9a7ae"
 "checksum utf8-ranges 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "662fab6525a98beff2921d7f61a39e7d59e0b425ebc7d0d9e66d316e55124122"
 "checksum void 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "6a02e4885ed3bc0f2de90ea6dd45ebcbb66dacffe03547fadbb0eeae2770887d"
-"checksum wasmi 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "9b4a6d379e9332b1b1f52c5a87f2481c85c7c931d8ec411963dfb8f26b1ec1e3"
+"checksum wasmi 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "522fe3fdd44a56f25cd5ddcd8ccdb1cf2e982ceb28fcb00f41d8a018ae5245a8"
 "checksum winapi 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)" = "04e3bd221fcbe8a271359c04f21a76db7d0c6028862d1bb5512d85e1e2eb5bb3"
 "checksum winapi-i686-pc-windows-gnu 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
 "checksum winapi-x86_64-pc-windows-gnu 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"