Millau -> Rialto headers relay (paritytech#398)

* working-millau-to-rialto-relay

* fix Millau state root

* properly fix synced+incomplete headers for sub2sub

* removed wrong TODO

* fmt + clippy

* Update relays/headers-relay/src/headers.rs

Co-authored-by: Hernando Castano <HCastano@users.noreply.github.com>

* moved SubstrateTransactionMaker definition

* removed M from phantomdata

* removed prune_synced_children

* methods names as consts

Co-authored-by: Hernando Castano <HCastano@users.noreply.github.com>

bin/rialto/runtime/src/lib.rs

@@ -62,6 +62,7 @@ pub use frame_support::{
 pub use pallet_balances::Call as BalancesCall;
 pub use pallet_bridge_currency_exchange::Call as BridgeCurrencyExchangeCall;
 pub use pallet_bridge_eth_poa::Call as BridgeEthPoACall;
+pub use pallet_substrate_bridge::Call as BridgeMillauCall;
 pub use pallet_timestamp::Call as TimestampCall;
 
 #[cfg(any(feature = "std", test))]

bin/rialto/runtime/src/millau.rs

@@ -36,7 +36,7 @@ pub fn initial_header() -> Header {
 	Header {
 		parent_hash: Default::default(),
 		number: Default::default(),
-		state_root: hex!("bb65e8ba99408ebfefea9d28f74403d41da6858fa075c51fcc71dc383455c530").into(),
+		state_root: hex!("e901070e3bb061a6ae9ea8e4ba5417bf4c4642f9e75af9d372861c170ba7a9a3").into(),
 		extrinsics_root: hex!("03170a2e7597b7b7e3d84c05391d139a62b157e78786d8c082f29dcf4c111314").into(),
 		digest: Default::default(),
 	}

primitives/millau/src/lib.rs

@@ -49,6 +49,13 @@ impl Chain for Millau {
 	type Header = Header;
 }
 
+/// Name of the `MillauHeaderApi::best_block` runtime method.
+pub const BEST_MILLAU_BLOCK_METHOD: &str = "MillauHeaderApi_best_block";
+/// Name of the `MillauHeaderApi::is_known_block` runtime method.
+pub const IS_KNOWN_MILLAU_BLOCK_METHOD: &str = "MillauHeaderApi_is_known_block";
+/// Name of the `MillauHeaderApi::incomplete_headers` runtime method.
+pub const INCOMPLETE_MILLAU_HEADERS_METHOD: &str = "MillauHeaderApi_incomplete_headers";
+
 sp_api::decl_runtime_apis! {
 	/// API for querying information about Millau headers from the Bridge Pallet instance.
 	///

relays/headers-relay/src/headers.rs

@@ -32,6 +32,8 @@ use std::{
 
 type HeadersQueue<P> =
 	BTreeMap<<P as HeadersSyncPipeline>::Number, HashMap<<P as HeadersSyncPipeline>::Hash, QueuedHeader<P>>>;
+type SyncedChildren<P> =
+	BTreeMap<<P as HeadersSyncPipeline>::Number, HashMap<<P as HeadersSyncPipeline>::Hash, HashSet<HeaderIdOf<P>>>>;
 type KnownHeaders<P> =
 	BTreeMap<<P as HeadersSyncPipeline>::Number, HashMap<<P as HeadersSyncPipeline>::Hash, HeaderStatus>>;
 
@@ -63,6 +65,9 @@ pub struct QueuedHeaders<P: HeadersSyncPipeline> {
 	/// Headers that are (we believe) currently submitted to target node by our,
 	/// not-yet mined transactions.
 	submitted: HeadersQueue<P>,
+	/// Synced headers childrens. We need it to support case when header is synced, but some of
+	/// its parents are incomplete.
+	synced_children: SyncedChildren<P>,
 	/// Pointers to all headers that we ever seen and we believe we can touch in the future.
 	known_headers: KnownHeaders<P>,
 	/// Headers that are waiting for completion data from source node. Mapped (and auto-sorted
@@ -96,6 +101,7 @@ impl<P: HeadersSyncPipeline> Default for QueuedHeaders<P> {
 			ready: HeadersQueue::new(),
 			incomplete: HeadersQueue::new(),
 			submitted: HeadersQueue::new(),
+			synced_children: SyncedChildren::<P>::new(),
 			known_headers: KnownHeaders::<P>::new(),
 			incomplete_headers: LinkedHashMap::new(),
 			completion_data: LinkedHashMap::new(),
@@ -419,13 +425,17 @@ impl<P: HeadersSyncPipeline> QueuedHeaders<P> {
 				self.header_synced(&new_incomplete_header);
 			}
 
-			move_header_descendants::<P>(
-				&mut [&mut self.ready, &mut self.submitted],
-				&mut self.incomplete,
-				&mut self.known_headers,
-				HeaderStatus::Incomplete,
-				&new_incomplete_header,
-			);
+			let move_origins = select_synced_children::<P>(&self.synced_children, &new_incomplete_header);
+			let move_origins = move_origins.into_iter().chain(std::iter::once(new_incomplete_header));
+			for move_origin in move_origins {
+				move_header_descendants::<P>(
+					&mut [&mut self.ready, &mut self.submitted],
+					&mut self.incomplete,
+					&mut self.known_headers,
+					HeaderStatus::Incomplete,
+					&move_origin,
+				);
+			}
 
 			if make_header_incomplete {
 				log::debug!(
@@ -460,13 +470,20 @@ impl<P: HeadersSyncPipeline> QueuedHeaders<P> {
 			.cloned()
 			.collect::<Vec<_>>();
 		for just_completed_header in just_completed_headers {
-			move_header_descendants::<P>(
-				&mut [&mut self.incomplete],
-				&mut self.ready,
-				&mut self.known_headers,
-				HeaderStatus::Ready,
-				&just_completed_header,
-			);
+			// sub2eth rejects H if H.Parent is incomplete
+			// sub2sub allows 'syncing' headers like that
+			// => let's check if there are some synced children of just completed header
+			let move_origins = select_synced_children::<P>(&self.synced_children, &just_completed_header);
+			let move_origins = move_origins.into_iter().chain(std::iter::once(just_completed_header));
+			for move_origin in move_origins {
+				move_header_descendants::<P>(
+					&mut [&mut self.incomplete],
+					&mut self.ready,
+					&mut self.known_headers,
+					HeaderStatus::Ready,
+					&move_origin,
+				);
+			}
 
 			log::debug!(
 				target: "bridge",
@@ -514,6 +531,7 @@ impl<P: HeadersSyncPipeline> QueuedHeaders<P> {
 		prune_queue(&mut self.ready, prune_border);
 		prune_queue(&mut self.submitted, prune_border);
 		prune_queue(&mut self.incomplete, prune_border);
+		self.synced_children = self.synced_children.split_off(&prune_border);
 		prune_known_headers::<P>(&mut self.known_headers, prune_border);
 		self.prune_border = prune_border;
 	}
@@ -527,6 +545,7 @@ impl<P: HeadersSyncPipeline> QueuedHeaders<P> {
 		self.ready.clear();
 		self.incomplete.clear();
 		self.submitted.clear();
+		self.synced_children.clear();
 		self.known_headers.clear();
 		self.best_synced_number = Zero::zero();
 		self.prune_border = Zero::zero();
@@ -568,6 +587,7 @@ impl<P: HeadersSyncPipeline> QueuedHeaders<P> {
 		// queues
 		let mut current = *id;
 		let mut id_processed = false;
+		let mut previous_current = None;
 		loop {
 			let header = match self.status(&current) {
 				HeaderStatus::Unknown => break,
@@ -582,8 +602,42 @@ impl<P: HeadersSyncPipeline> QueuedHeaders<P> {
 			}
 			.expect("header has a given status; given queue has the header; qed");
 
+			// remember ids of all the children of the current header
+			let synced_children_entry = self
+				.synced_children
+				.entry(current.0)
+				.or_default()
+				.entry(current.1)
+				.or_default();
+			let all_queues = [
+				&self.maybe_orphan,
+				&self.orphan,
+				&self.maybe_extra,
+				&self.extra,
+				&self.ready,
+				&self.incomplete,
+				&self.submitted,
+			];
+			for queue in &all_queues {
+				let children_from_queue = queue
+					.get(&(current.0 + One::one()))
+					.map(|potential_children| {
+						potential_children
+							.values()
+							.filter(|potential_child| potential_child.header().parent_id() == current)
+							.map(|child| child.id())
+							.collect::<Vec<_>>()
+					})
+					.unwrap_or_default();
+				synced_children_entry.extend(children_from_queue);
+			}
+			if let Some(previous_current) = previous_current {
+				synced_children_entry.insert(previous_current);
+			}
+
 			set_header_status::<P>(&mut self.known_headers, &current, HeaderStatus::Synced);
 
+			previous_current = Some(current);
 			current = header.parent_id();
 			id_processed = true;
 		}
@@ -706,6 +760,35 @@ fn move_header_descendants<P: HeadersSyncPipeline>(
 	}
 }
 
+/// Selects (recursive) all synced children of given header.
+fn select_synced_children<P: HeadersSyncPipeline>(
+	synced_children: &SyncedChildren<P>,
+	id: &HeaderIdOf<P>,
+) -> Vec<HeaderIdOf<P>> {
+	let mut result = Vec::new();
+	let mut current_parents = HashSet::new();
+	current_parents.insert(*id);
+
+	while !current_parents.is_empty() {
+		let mut next_parents = HashSet::new();
+		for current_parent in &current_parents {
+			let current_parent_synced_children = synced_children
+				.get(&current_parent.0)
+				.and_then(|by_number_entry| by_number_entry.get(&current_parent.1));
+			if let Some(current_parent_synced_children) = current_parent_synced_children {
+				for current_parent_synced_child in current_parent_synced_children {
+					result.push(*current_parent_synced_child);
+					next_parents.insert(*current_parent_synced_child);
+				}
+			}
+		}
+
+		let _ = std::mem::replace(&mut current_parents, next_parents);
+	}
+
+	result
+}
+
 /// Return oldest header from the queue.
 fn oldest_header<P: HeadersSyncPipeline>(queue: &HeadersQueue<P>) -> Option<&QueuedHeader<P>> {
 	queue.values().flat_map(|h| h.values()).next()
@@ -1050,6 +1133,37 @@ pub(crate) mod tests {
 			.known_headers
 			.values()
 			.all(|s| s.values().all(|s| *s == HeaderStatus::Synced)));
+
+		// children of synced headers are stored
+		assert_eq!(
+			vec![id(97)],
+			queue.synced_children[&96][&hash(96)]
+				.iter()
+				.cloned()
+				.collect::<Vec<_>>()
+		);
+		assert_eq!(
+			vec![id(98)],
+			queue.synced_children[&97][&hash(97)]
+				.iter()
+				.cloned()
+				.collect::<Vec<_>>()
+		);
+		assert_eq!(
+			vec![id(99)],
+			queue.synced_children[&98][&hash(98)]
+				.iter()
+				.cloned()
+				.collect::<Vec<_>>()
+		);
+		assert_eq!(
+			vec![id(100)],
+			queue.synced_children[&99][&hash(99)]
+				.iter()
+				.cloned()
+				.collect::<Vec<_>>()
+		);
+		assert_eq!(0, queue.synced_children[&100][&hash(100)].len());
 	}
 
 	#[test]
@@ -1463,6 +1577,16 @@ pub(crate) mod tests {
 			.or_default()
 			.insert(hash(100), HeaderStatus::Ready);
 		queue.ready.entry(100).or_default().insert(hash(100), header(100));
+		queue
+			.synced_children
+			.entry(100)
+			.or_default()
+			.insert(hash(100), vec![id(101)].into_iter().collect());
+		queue
+			.synced_children
+			.entry(102)
+			.or_default()
+			.insert(hash(102), vec![id(102)].into_iter().collect());
 
 		queue.prune(102);
 
@@ -1472,6 +1596,7 @@ pub(crate) mod tests {
 		assert_eq!(queue.orphan.len(), 1);
 		assert_eq!(queue.maybe_orphan.len(), 1);
 		assert_eq!(queue.incomplete.len(), 1);
+		assert_eq!(queue.synced_children.len(), 1);
 		assert_eq!(queue.known_headers.len(), 4);
 
 		queue.prune(110);
@@ -1482,6 +1607,7 @@ pub(crate) mod tests {
 		assert_eq!(queue.orphan.len(), 0);
 		assert_eq!(queue.maybe_orphan.len(), 0);
 		assert_eq!(queue.incomplete.len(), 0);
+		assert_eq!(queue.synced_children.len(), 0);
 		assert_eq!(queue.known_headers.len(), 0);
 
 		queue.header_response(header(109).header().clone());
@@ -1537,4 +1663,47 @@ pub(crate) mod tests {
 		assert_eq!(queue.status(&id(103)), HeaderStatus::Incomplete);
 		assert_eq!(queue.status(&id(104)), HeaderStatus::Incomplete);
 	}
+
+	#[test]
+	fn incomplete_headers_response_moves_synced_headers() {
+		let mut queue = QueuedHeaders::<TestHeadersSyncPipeline>::default();
+
+		// we have submitted two headers - 100 and 101. 102 is ready
+		queue.submitted.entry(100).or_default().insert(hash(100), header(100));
+		queue.submitted.entry(101).or_default().insert(hash(101), header(101));
+		queue.ready.entry(102).or_default().insert(hash(102), header(102));
+		queue
+			.known_headers
+			.entry(100)
+			.or_default()
+			.insert(hash(100), HeaderStatus::Submitted);
+		queue
+			.known_headers
+			.entry(101)
+			.or_default()
+			.insert(hash(101), HeaderStatus::Submitted);
+		queue
+			.known_headers
+			.entry(102)
+			.or_default()
+			.insert(hash(102), HeaderStatus::Ready);
+
+		// both headers are accepted
+		queue.target_best_header_response(&id(101));
+
+		// but header 100 is incomplete
+		queue.incomplete_headers_response(vec![id(100)].into_iter().collect());
+		assert_eq!(queue.status(&id(100)), HeaderStatus::Synced);
+		assert_eq!(queue.status(&id(101)), HeaderStatus::Synced);
+		assert_eq!(queue.status(&id(102)), HeaderStatus::Incomplete);
+		assert!(queue.incomplete_headers.contains_key(&id(100)));
+		assert!(queue.incomplete[&102].contains_key(&hash(102)));
+
+		// when header 100 is completed, 101 is synced and 102 is ready
+		queue.incomplete_headers_response(HashSet::new());
+		assert_eq!(queue.status(&id(100)), HeaderStatus::Synced);
+		assert_eq!(queue.status(&id(101)), HeaderStatus::Synced);
+		assert_eq!(queue.status(&id(102)), HeaderStatus::Ready);
+		assert!(queue.ready[&102].contains_key(&hash(102)));
+	}
 }

relays/headers-relay/src/sync_loop.rs

@@ -277,7 +277,7 @@ pub fn run<P: HeadersSyncPipeline, TC: TargetClient<P>>(
 						},
 						&mut target_go_offline_future,
 						|delay| async_std::task::sleep(delay),
-						|| format!("Error retrieving best known header from {} node", P::TARGET_NAME),
+						|| format!("Error retrieving best known {} header from {} node", P::SOURCE_NAME, P::TARGET_NAME),
 					).is_ok();
 				},
 				incomplete_headers_ids = target_incomplete_headers_future => {

relays/headers-relay/src/sync_types.rs

@@ -43,7 +43,7 @@ pub enum HeaderStatus {
 }
 
 /// Headers synchronization pipeline.
-pub trait HeadersSyncPipeline: Clone + Copy + Send + Sync {
+pub trait HeadersSyncPipeline: Clone + Send + Sync {
 	/// Name of the headers source.
 	const SOURCE_NAME: &'static str;
 	/// Name of the headers target.

relays/millau-client/src/lib.rs

@@ -60,12 +60,18 @@ impl From<millau_runtime::Header> for SyncHeader {
 	}
 }
 
+impl From<SyncHeader> for millau_runtime::Header {
+	fn from(header: SyncHeader) -> Self {
+		header.0
+	}
+}
+
 impl SourceHeader<millau_runtime::Hash, millau_runtime::BlockNumber> for SyncHeader {
 	fn id(&self) -> HeaderId {
 		relay_utils::HeaderId(*self.number(), self.hash())
 	}
 
 	fn parent_id(&self) -> HeaderId {
-		relay_utils::HeaderId(*self.number(), *self.parent_hash())
+		relay_utils::HeaderId(*self.number() - 1, *self.parent_hash())
 	}
 }

relays/rialto-client/src/lib.rs

@@ -25,6 +25,8 @@ use sp_runtime::{
 	traits::{Header as HeaderT, IdentifyAccount},
 };
 
+pub use rialto_runtime::BridgeMillauCall;
+
 /// Rialto header id.
 pub type HeaderId = relay_utils::HeaderId<rialto_runtime::Hash, rialto_runtime::BlockNumber>;
 

relays/substrate-client/src/client.rs

@@ -33,6 +33,9 @@ const SUB_API_GRANDPA_AUTHORITIES: &str = "GrandpaApi_grandpa_authorities";
 pub type OpaqueGrandpaAuthoritiesSet = Vec<u8>;
 
 /// Substrate client type.
+///
+/// Cloning Client is a cheap operation.
+#[derive(Clone)]
 pub struct Client<C: Chain> {
 	/// Substrate RPC client.
 	client: RpcClient,