past-session validator discovery APIs

node/core/runtime-api/src/lib.rs

@@ -134,7 +134,7 @@ fn make_runtime_api_request<Client>(
 		Request::CandidatePendingAvailability(para, sender) =>
 			query!(candidate_pending_availability(para), sender),
 		Request::CandidateEvents(sender) => query!(candidate_events(), sender),
-		Request::ValidatorDiscovery(ids, sender) => query!(validator_discovery(ids), sender),
+		Request::SessionInfo(index, sender) => query!(session_info(index), sender),
 		Request::DmqContents(id, sender) => query!(dmq_contents(id), sender),
 		Request::InboundHrmpChannelsContents(id, sender) => query!(inbound_hrmp_channels_contents(id), sender),
 	}
@@ -201,8 +201,8 @@ mod tests {
 	use polkadot_primitives::v1::{
 		ValidatorId, ValidatorIndex, GroupRotationInfo, CoreState, PersistedValidationData,
 		Id as ParaId, OccupiedCoreAssumption, ValidationData, SessionIndex, ValidationCode,
-		CommittedCandidateReceipt, CandidateEvent, AuthorityDiscoveryId, InboundDownwardMessage,
-		BlockNumber, InboundHrmpMessage,
+		CommittedCandidateReceipt, CandidateEvent, InboundDownwardMessage,
+		BlockNumber, InboundHrmpMessage, SessionInfo,
 	};
 	use polkadot_node_subsystem_test_helpers as test_helpers;
 	use sp_core::testing::TaskExecutor;
@@ -216,6 +216,7 @@ mod tests {
 		availability_cores: Vec<CoreState>,
 		validation_data: HashMap<ParaId, ValidationData>,
 		session_index_for_child: SessionIndex,
+		session_info: HashMap<SessionIndex, SessionInfo>,
 		validation_code: HashMap<ParaId, ValidationCode>,
 		historical_validation_code: HashMap<ParaId, Vec<(BlockNumber, ValidationCode)>>,
 		validation_outputs_results: HashMap<ParaId, bool>,
@@ -289,6 +290,10 @@ mod tests {
 				self.session_index_for_child.clone()
 			}
 
+			fn session_info(&self, index: SessionIndex) -> Option<SessionInfo> {
+				self.session_info.get(&index).cloned()
+			}
+
 			fn validation_code(
 				&self,
 				para: ParaId,
@@ -321,10 +326,6 @@ mod tests {
 				self.candidate_events.clone()
 			}
 
-			fn validator_discovery(ids: Vec<ValidatorId>) -> Vec<Option<AuthorityDiscoveryId>> {
-				vec![None; ids.len()]
-			}
-
 			fn dmq_contents(
 				&self,
 				recipient: ParaId,

node/network/collator-protocol/src/collator_side.rs

@@ -738,6 +738,7 @@ mod tests {
 	use polkadot_primitives::v1::{
 		BlockData, CandidateDescriptor, CollatorPair, ScheduledCore,
 		ValidatorIndex, GroupRotationInfo, AuthorityDiscoveryId,
+		SessionInfo,
 	};
 	use polkadot_subsystem::{ActiveLeavesUpdate, messages::{RuntimeApiMessage, RuntimeApiRequest}};
 	use polkadot_node_subsystem_util::TimeoutExt;
@@ -870,20 +871,6 @@ mod tests {
 				.collect()
 		}
 
-		fn next_group_validator_ids(&self) -> Vec<ValidatorId> {
-			self.next_group_validator_indices()
-				.iter()
-				.map(|i| self.validator_public[*i as usize].clone())
-				.collect()
-		}
-
-		/// Returns the unique count of validators in the current and next group.
-		fn current_and_next_group_unique_validator_count(&self) -> usize {
-			let mut indices = self.next_group_validator_indices().iter().collect::<HashSet<_>>();
-			indices.extend(self.current_group_validator_indices());
-			indices.len()
-		}
-
 		/// Generate a new relay parent and inform the subsystem about the new view.
 		///
 		/// If `merge_views == true` it means the subsystem will be informed that we working on the old `relay_parent`
@@ -1085,25 +1072,40 @@ mod tests {
 			}
 		);
 
+		let current_index = 1;
+
 		// obtain the validator_id to authority_id mapping
 		assert_matches!(
 			overseer_recv(virtual_overseer).await,
 			AllMessages::RuntimeApi(RuntimeApiMessage::Request(
 				relay_parent,
-				RuntimeApiRequest::ValidatorDiscovery(validators, tx),
+				RuntimeApiRequest::SessionIndexForChild(tx),
 			)) => {
 				assert_eq!(relay_parent, test_state.relay_parent);
-				assert_eq!(validators.len(), test_state.current_and_next_group_unique_validator_count());
+				tx.send(Ok(current_index)).unwrap();
+			}
+		);
 
-				let current_validators = test_state.current_group_validator_ids();
-				let next_validators = test_state.next_group_validator_ids();
+		assert_matches!(
+			overseer_recv(virtual_overseer).await,
+			AllMessages::RuntimeApi(RuntimeApiMessage::Request(
+				relay_parent,
+				RuntimeApiRequest::SessionInfo(index, tx),
+			)) => {
+				assert_eq!(relay_parent, test_state.relay_parent);
+				assert_eq!(index, current_index);
 
-				assert!(validators.iter().all(|v| current_validators.contains(&v) || next_validators.contains(&v)));
+				let validators = test_state.current_group_validator_ids();
+				let current_discovery_keys = test_state.current_group_validator_authority_ids();
+				let next_discovery_keys = test_state.next_group_validator_authority_ids();
 
-				let current_validators = test_state.current_group_validator_authority_ids();
-				let next_validators = test_state.next_group_validator_authority_ids();
+				let discovery_keys = [&current_discovery_keys[..], &next_discovery_keys[..]].concat();
 
-				tx.send(Ok(current_validators.into_iter().chain(next_validators).map(Some).collect())).unwrap();
+				tx.send(Ok(Some(SessionInfo {
+					validators,
+					discovery_keys,
+					..Default::default()
+				}))).unwrap();
 			}
 		);
 

node/network/collator-protocol/src/lib.rs

@@ -60,16 +60,6 @@ enum Error {
 	Prometheus(#[from] prometheus::PrometheusError),
 }
 
-impl From<util::validator_discovery::Error> for Error {
-	fn from(me: util::validator_discovery::Error) -> Self {
-		match me {
-			util::validator_discovery::Error::Subsystem(s) => Error::Subsystem(s),
-			util::validator_discovery::Error::RuntimeApi(ra) => Error::RuntimeApi(ra),
-			util::validator_discovery::Error::Oneshot(c) => Error::Oneshot(c),
-		}
-	}
-}
-
 type Result<T> = std::result::Result<T, Error>;
 
 /// What side of the collator protocol is being engaged

node/subsystem-util/src/lib.rs

@@ -37,6 +37,7 @@ use polkadot_primitives::v1::{
 	CandidateEvent, CommittedCandidateReceipt, CoreState, EncodeAs, PersistedValidationData,
 	GroupRotationInfo, Hash, Id as ParaId, ValidationData, OccupiedCoreAssumption,
 	SessionIndex, Signed, SigningContext, ValidationCode, ValidatorId, ValidatorIndex,
+	SessionInfo,
 };
 use sp_core::{
 	traits::SpawnNamed,
@@ -274,6 +275,7 @@ specialize_requests_ctx! {
 	fn request_validation_code_ctx(para_id: ParaId, assumption: OccupiedCoreAssumption) -> Option<ValidationCode>; ValidationCode;
 	fn request_candidate_pending_availability_ctx(para_id: ParaId) -> Option<CommittedCandidateReceipt>; CandidatePendingAvailability;
 	fn request_candidate_events_ctx() -> Vec<CandidateEvent>; CandidateEvents;
+	fn request_session_info_ctx(index: SessionIndex) -> Option<SessionInfo>; SessionInfo;
 }
 
 /// From the given set of validators, find the first key we can sign with, if any.

node/subsystem-util/src/validator_discovery.rs

@@ -20,52 +20,53 @@ use std::collections::HashMap;
 use std::pin::Pin;
 
 use futures::{
-	channel::{mpsc, oneshot},
+	channel::mpsc,
 	task::{Poll, self},
 	stream,
 };
 use streamunordered::{StreamUnordered, StreamYield};
-use thiserror::Error;
 
 use polkadot_node_subsystem::{
-	errors::RuntimeApiError, SubsystemError,
-	messages::{AllMessages, RuntimeApiMessage, RuntimeApiRequest, NetworkBridgeMessage},
+	errors::RuntimeApiError,
+	messages::{AllMessages, NetworkBridgeMessage},
 	SubsystemContext,
 };
 use polkadot_primitives::v1::{Hash, ValidatorId, AuthorityDiscoveryId};
 use sc_network::PeerId;
-
-/// Error when making a request to connect to validators.
-#[derive(Debug, Error)]
-pub enum Error {
-	/// Attempted to send or receive on a oneshot channel which had been canceled
-	#[error(transparent)]
-	Oneshot(#[from] oneshot::Canceled),
-	/// A subsystem error.
-	#[error(transparent)]
-	Subsystem(#[from] SubsystemError),
-	/// An error in the Runtime API.
-	#[error(transparent)]
-	RuntimeApi(#[from] RuntimeApiError),
-}
+use crate::Error;
 
 /// Utility function to make it easier to connect to validators.
 pub async fn connect_to_validators<Context: SubsystemContext>(
 	ctx: &mut Context,
 	relay_parent: Hash,
 	validators: Vec<ValidatorId>,
 ) -> Result<ConnectionRequest, Error> {
-	// ValidatorId -> AuthorityDiscoveryId
-	let (tx, rx) = oneshot::channel();
-
-	ctx.send_message(AllMessages::RuntimeApi(
-		RuntimeApiMessage::Request(
-			relay_parent,
-			RuntimeApiRequest::ValidatorDiscovery(validators.clone(), tx),
-		)
-	)).await;
+	let current_index = crate::request_session_index_for_child_ctx(relay_parent, ctx).await?.await??;
+	let session_info = crate::request_session_info_ctx(
+		relay_parent,
+		current_index,
+		ctx,
+	).await?.await??;
+
+	let (session_validators, discovery_keys) = match session_info {
+		Some(info) => (info.validators, info.discovery_keys),
+		None => return Err(RuntimeApiError::from(
+			"No session_info found for the current index".to_owned()
+		).into()),
+	};
+
+	let id_to_index = session_validators.iter()
+		.zip(0usize..)
+		.collect::<HashMap<_, _>>();
+
+	// We assume the same ordering in authorities as in validators so we can do an index search
+	let maybe_authorities: Vec<_> = validators.iter()
+		.map(|id| {
+			let validator_index = id_to_index.get(&id);
+			validator_index.and_then(|i| discovery_keys.get(*i).cloned())
+		})
+		.collect();
 
-	let maybe_authorities = rx.await??;
 	let authorities: Vec<_> = maybe_authorities.iter()
 		.cloned()
 		.filter_map(|id| id)

node/subsystem/src/messages.rs

@@ -31,7 +31,7 @@ use polkadot_node_primitives::{
 	CollationGenerationConfig, MisbehaviorReport, SignedFullStatement, ValidationResult,
 };
 use polkadot_primitives::v1::{
-	AuthorityDiscoveryId, AvailableData, BackedCandidate, BlockNumber,
+	AuthorityDiscoveryId, AvailableData, BackedCandidate, BlockNumber, SessionInfo,
 	Header as BlockHeader, CandidateDescriptor, CandidateEvent, CandidateReceipt,
 	CollatorId, CommittedCandidateReceipt, CoreState, ErasureChunk,
 	GroupRotationInfo, Hash, Id as ParaId, OccupiedCoreAssumption,
@@ -434,14 +434,8 @@ pub enum RuntimeApiRequest {
 	/// Get all events concerning candidates (backing, inclusion, time-out) in the parent of
 	/// the block in whose state this request is executed.
 	CandidateEvents(RuntimeApiSender<Vec<CandidateEvent>>),
-	/// Get the `AuthorityDiscoveryId`s corresponding to the given `ValidatorId`s.
-	/// Currently this request is limited to validators in the current session.
-	///
-	/// Returns `None` for validators not found in the current session.
-	ValidatorDiscovery(
-		Vec<ValidatorId>,
-		RuntimeApiSender<Vec<Option<AuthorityDiscoveryId>>>,
-	),
+	/// Get the session info for the given session, if stored.
+	SessionInfo(SessionIndex, RuntimeApiSender<Option<SessionInfo>>),
 	/// Get all the pending inbound messages in the downward message queue for a para.
 	DmqContents(
 		ParaId,

primitives/src/v1.rs

@@ -671,6 +671,37 @@ pub enum CandidateEvent<H = Hash> {
 	CandidateTimedOut(CandidateReceipt<H>, HeadData),
 }
 
+/// Information about validator sets of a session.
+#[derive(Clone, Encode, Decode, RuntimeDebug)]
+#[cfg_attr(feature = "std", derive(PartialEq, Default))]
+pub struct SessionInfo {
+	/// Validators in canonical ordering.
+	pub validators: Vec<ValidatorId>,
+	/// Validators' authority discovery keys for the session in canonical ordering.
+	pub discovery_keys: Vec<AuthorityDiscoveryId>,
+	/// The assignment and approval keys for validators.
+	// FIXME: implement this
+	#[codec(skip)]
+	pub approval_keys: Vec<()>,
+	/// Validators in shuffled ordering - these are the validator groups as produced
+	/// by the `Scheduler` module for the session and are typically referred to by
+	/// `GroupIndex`.
+	pub validator_groups: Vec<Vec<ValidatorIndex>>,
+	/// The number of availability cores used by the protocol during this session.
+	pub n_cores: u32,
+	/// The zeroth delay tranche width.
+	pub zeroth_delay_tranche_width: u32,
+	/// The number of samples we do of relay_vrf_modulo.
+	pub relay_vrf_modulo_samples: u32,
+	/// The number of delay tranches in total.
+	pub n_delay_tranches: u32,
+	/// How many slots (BABE / SASSAFRAS) must pass before an assignment is considered a
+	/// no-show.
+	pub no_show_slots: u32,
+	/// The number of validators needed to approve a block.
+	pub needed_approvals: u32,
+}
+
 sp_api::decl_runtime_apis! {
 	/// The API for querying the state of parachains on-chain.
 	pub trait ParachainHost<H: Decode = Hash, N: Encode + Decode = BlockNumber> {
@@ -710,6 +741,9 @@ sp_api::decl_runtime_apis! {
 		/// This can be used to instantiate a `SigningContext`.
 		fn session_index_for_child() -> SessionIndex;
 
+		/// Get the session info for the given session, if stored.
+		fn session_info(index: SessionIndex) -> Option<SessionInfo>;
+
 		/// Fetch the validation code used by a para, making the given `OccupiedCoreAssumption`.
 		///
 		/// Returns `None` if either the para is not registered or the assumption is `Freed`
@@ -735,13 +769,6 @@ sp_api::decl_runtime_apis! {
 		#[skip_initialize_block]
 		fn candidate_events() -> Vec<CandidateEvent<H>>;
 
-		/// Get the `AuthorityDiscoveryId`s corresponding to the given `ValidatorId`s.
-		/// Currently this request is limited to validators in the current session.
-		///
-		/// We assume that every validator runs authority discovery,
-		/// which would allow us to establish point-to-point connection to given validators.
-		fn validator_discovery(validators: Vec<ValidatorId>) -> Vec<Option<AuthorityDiscoveryId>>;
-
 		/// Get all the pending inbound messages in the downward message queue for a para.
 		fn dmq_contents(
 			recipient: Id,

roadmap/implementers-guide/src/runtime/initializer.md

@@ -23,7 +23,7 @@ The other parachains modules are initialized in this order:
 1. Paras
 1. Scheduler
 1. Inclusion
-1. Validity
+1. SessionInfo
 1. DMP
 1. UMP
 1. HRMP

roadmap/implementers-guide/src/runtime/session_info.md

@@ -30,11 +30,11 @@ struct SessionInfo {
     // no-show.
     no_show_slots: u32,
     /// The number of validators needed to approve a block.
-	needed_approvals: u32,
+    needed_approvals: u32,
 }
 ```
 
-Storage Layout: 
+Storage Layout:
 
 ```rust
 /// The earliest session for which previous session info is stored.
@@ -45,11 +45,10 @@ Sessions: map SessionIndex => Option<SessionInfo>,
 
 ## Session Change
 
-1. Update the `CurrentSessionIndex`.
 1. Update `EarliestStoredSession` based on `config.dispute_period` and remove all entries from `Sessions` from the previous value up to the new value.
 1. Create a new entry in `Sessions` with information about the current session.
 
 ## Routines
 
 * `earliest_stored_session() -> SessionIndex`: Yields the earliest session for which we have information stored.
-* `session_info(session: SessionIndex) -> Option<SessionInfo>`: Yields the session info for the given session, if stored.
+* `session_info(session: SessionIndex) -> Option<SessionInfo>`: Yields the session info for the given session, if stored.