Offline fallback for GRANDPA

Cargo.toml

@@ -67,6 +67,7 @@ members = [
 	"srml/example",
 	"srml/executive",
 	"srml/fees",
+	"srml/finality-tracker",
 	"srml/grandpa",
 	"srml/indices",
 	"srml/metadata",

core/client/src/client.rs

@@ -27,7 +27,7 @@ use runtime_primitives::{
 };
 use consensus::{
 	Error as ConsensusError, ErrorKind as ConsensusErrorKind, ImportBlock, ImportResult,
-	BlockOrigin, ForkChoiceStrategy
+	BlockOrigin, ForkChoiceStrategy,
 };
 use runtime_primitives::traits::{
 	Block as BlockT, Header as HeaderT, Zero, As, NumberFor, CurrentHeight, BlockNumberToHash,
@@ -619,9 +619,10 @@ impl<B, E, Block, RA> Client<B, E, Block, RA> where
 	}
 
 	/// Lock the import lock, and run operations inside.
-	pub fn lock_import_and_run<R, F: FnOnce(&mut ClientImportOperation<Block, Blake2Hasher, B>) -> error::Result<R>>(
-		&self, f: F
-	) -> error::Result<R> {
+	pub fn lock_import_and_run<R, Err, F>(&self, f: F) -> Result<R, Err> where
+		F: FnOnce(&mut ClientImportOperation<Block, Blake2Hasher, B>) -> Result<R, Err>,
+		Err: From<error::Error>,
+	{
 		let inner = || {
 			let _import_lock = self.import_lock.lock();
 
@@ -827,7 +828,7 @@ impl<B, E, Block, RA> Client<B, E, Block, RA> where
 			operation.notify_imported = Some((hash, origin, import_headers.into_post(), is_new_best, storage_changes));
 		}
 
-		Ok(ImportResult::Queued)
+		Ok(ImportResult::imported())
 	}
 
 	fn block_execution(
@@ -1391,13 +1392,15 @@ impl<B, E, Block, RA> consensus::BlockImport<Block> for Client<B, E, Block, RA>
 			blockchain::BlockStatus::InChain => {},
 			blockchain::BlockStatus::Unknown => return Ok(ImportResult::UnknownParent),
 		}
+
 		match self.backend.blockchain().status(BlockId::Hash(hash))
 			.map_err(|e| ConsensusError::from(ConsensusErrorKind::ClientImport(e.to_string())))?
 		{
 			blockchain::BlockStatus::InChain => return Ok(ImportResult::AlreadyInChain),
 			blockchain::BlockStatus::Unknown => {},
 		}
-		Ok(ImportResult::Queued)
+
+		Ok(ImportResult::imported())
 	}
 }
 
@@ -1414,7 +1417,7 @@ impl<B, E, Block, RA> consensus::Authorities<Block> for Client<B, E, Block, RA>
 
 impl<B, E, Block, RA> CurrentHeight for Client<B, E, Block, RA> where
 	B: backend::Backend<Block, Blake2Hasher>,
-	E: CallExecutor<Block, Blake2Hasher> + Clone,
+	E: CallExecutor<Block, Blake2Hasher>,
 	Block: BlockT<Hash=H256>,
 {
 	type BlockNumber = <Block::Header as HeaderT>::Number;
@@ -1425,7 +1428,7 @@ impl<B, E, Block, RA> CurrentHeight for Client<B, E, Block, RA> where
 
 impl<B, E, Block, RA> BlockNumberToHash for Client<B, E, Block, RA> where
 	B: backend::Backend<Block, Blake2Hasher>,
-	E: CallExecutor<Block, Blake2Hasher> + Clone,
+	E: CallExecutor<Block, Blake2Hasher>,
 	Block: BlockT<Hash=H256>,
 {
 	type BlockNumber = <Block::Header as HeaderT>::Number;

core/consensus/common/src/block_import.rs

@@ -23,19 +23,40 @@ use std::borrow::Cow;
 /// Block import result.
 #[derive(Debug, PartialEq, Eq)]
 pub enum ImportResult {
-	/// Added to the import queue.
-	Queued,
-	/// Already in the import queue.
-	AlreadyQueued,
+	/// Block imported.
+	Imported(ImportedAux),
 	/// Already in the blockchain.
 	AlreadyInChain,
 	/// Block or parent is known to be bad.
 	KnownBad,
 	/// Block parent is not in the chain.
 	UnknownParent,
-	/// Added to the import queue but must be justified
-	/// (usually required to safely enact consensus changes).
-	NeedsJustification,
+}
+
+/// Auxiliary data associated with an imported block result.
+#[derive(Debug, PartialEq, Eq)]
+pub struct ImportedAux {
+	/// Clear all pending justification requests.
+	pub clear_justification_requests: bool,
+	/// Request a justification for the given block.
+	pub needs_justification: bool,
+}
+
+impl Default for ImportedAux {
+	fn default() -> ImportedAux {
+		ImportedAux {
+			clear_justification_requests: false,
+			needs_justification: false,
+		}
+	}
+}
+
+impl ImportResult {
+	/// Returns default value for `ImportResult::Imported` with both
+	/// `clear_justification_requests` and `needs_justification` set to false.
+	pub fn imported() -> ImportResult {
+		ImportResult::Imported(ImportedAux::default())
+	}
 }
 
 /// Block data origin.

core/consensus/common/src/import_queue.rs

@@ -24,7 +24,9 @@
 //! The `BasicQueue` and `BasicVerifier` traits allow serial queues to be
 //! instantiated simply.
 
-use crate::block_import::{ImportBlock, BlockImport, JustificationImport, ImportResult, BlockOrigin};
+use crate::block_import::{
+	BlockImport, BlockOrigin, ImportBlock, ImportedAux, ImportResult, JustificationImport,
+};
 use crossbeam_channel::{self as channel, Receiver, Sender};
 
 use std::collections::HashSet;
@@ -361,31 +363,37 @@ impl<B: BlockT> BlockImporter<B> {
 
 			match result {
 				Ok(BlockImportResult::ImportedKnown(number)) => link.block_imported(&hash, number),
-				Ok(BlockImportResult::ImportedUnknown(number)) => {
-					link.block_imported(&hash, number)
-				}
-				Ok(BlockImportResult::ImportedUnjustified(number)) => {
+				Ok(BlockImportResult::ImportedUnknown(number, aux)) => {
 					link.block_imported(&hash, number);
-					link.request_justification(&hash, number);
+
+					if aux.clear_justification_requests {
+						trace!(target: "sync", "Block imported clears all pending justification requests {}: {:?}", number, hash);
+						link.clear_justification_requests();
+					}
+
+					if aux.needs_justification {
+						trace!(target: "sync", "Block imported but requires justification {}: {:?}", number, hash);
+						link.request_justification(&hash, number);
+					}
 				},
 				Err(BlockImportError::IncompleteHeader(who)) => {
 					if let Some(peer) = who {
 						link.note_useless_and_restart_sync(peer, "Sent block with incomplete header to import");
 					}
-				}
+				},
 				Err(BlockImportError::VerificationFailed(who, e)) => {
 					if let Some(peer) = who {
 						link.note_useless_and_restart_sync(peer, &format!("Verification failed: {}", e));
 					}
-				}
+				},
 				Err(BlockImportError::BadBlock(who)) => {
 					if let Some(peer) = who {
 						link.note_useless_and_restart_sync(peer, "Sent us a bad block");
 					}
-				}
+				},
 				Err(BlockImportError::UnknownParent) | Err(BlockImportError::Error) => {
-					link.restart()
-				}
+					link.restart();
+				},
 			};
 		}
 		if let Some(link) = self.link.as_ref() {
@@ -529,11 +537,13 @@ impl<B: BlockT, V: 'static + Verifier<B>> BlockImportWorker<B, V> {
 /// algorithm.
 pub trait Link<B: BlockT>: Send {
 	/// Block imported.
-	fn block_imported(&self, _hash: &B::Hash, _number: NumberFor<B>) { }
+	fn block_imported(&self, _hash: &B::Hash, _number: NumberFor<B>) {}
 	/// Justification import result.
-	fn justification_imported(&self, _who: Origin, _hash: &B::Hash, _number: NumberFor<B>, _success: bool) { }
+	fn justification_imported(&self, _who: Origin, _hash: &B::Hash, _number: NumberFor<B>, _success: bool) {}
+	/// Clear all pending justification requests.
+	fn clear_justification_requests(&self) {}
 	/// Request a justification for the given block.
-	fn request_justification(&self, _hash: &B::Hash, _number: NumberFor<B>) { }
+	fn request_justification(&self, _hash: &B::Hash, _number: NumberFor<B>) {}
 	/// Maintain sync.
 	fn maintain_sync(&self) {}
 	/// Disconnect from peer.
@@ -550,9 +560,7 @@ pub enum BlockImportResult<N: ::std::fmt::Debug + PartialEq> {
 	/// Imported known block.
 	ImportedKnown(N),
 	/// Imported unknown block.
-	ImportedUnknown(N),
-	/// Imported unjustified block that requires one.
-	ImportedUnjustified(N),
+	ImportedUnknown(N, ImportedAux),
 }
 
 /// Block import error.
@@ -601,17 +609,7 @@ pub fn import_single_block<B: BlockT, V: Verifier<B>>(
 				trace!(target: "sync", "Block already in chain {}: {:?}", number, hash);
 				Ok(BlockImportResult::ImportedKnown(number))
 			},
-			Ok(ImportResult::AlreadyQueued) => {
-				trace!(target: "sync", "Block already queued {}: {:?}", number, hash);
-				Ok(BlockImportResult::ImportedKnown(number))
-			},
-			Ok(ImportResult::Queued) => {
-				Ok(BlockImportResult::ImportedUnknown(number))
-			},
-			Ok(ImportResult::NeedsJustification) => {
-				trace!(target: "sync", "Block queued but requires justification {}: {:?}", number, hash);
-				Ok(BlockImportResult::ImportedUnjustified(number))
-			},
+			Ok(ImportResult::Imported(aux)) => Ok(BlockImportResult::ImportedUnknown(number, aux)),
 			Ok(ImportResult::UnknownParent) => {
 				debug!(target: "sync", "Block with unknown parent {}: {:?}, parent: {:?}", number, hash, parent);
 				Err(BlockImportError::UnknownParent)
@@ -628,7 +626,7 @@ pub fn import_single_block<B: BlockT, V: Verifier<B>>(
 	};
 
 	match import_error(import_handle.check_block(hash, parent))? {
-		BlockImportResult::ImportedUnknown(_) => (),
+		BlockImportResult::ImportedUnknown { .. } => (),
 		r @ _ => return Ok(r), // Any other successfull result means that the block is already imported.
 	}
 
@@ -713,7 +711,7 @@ mod tests {
 		assert_eq!(link_port.recv(), Ok(LinkMsg::BlockImported));
 
 		// Send an unknown
-		let results = vec![(Ok(BlockImportResult::ImportedUnknown(Default::default())), Default::default())];
+		let results = vec![(Ok(BlockImportResult::ImportedUnknown(Default::default(), Default::default())), Default::default())];
 		let _ = result_sender.send(BlockImportWorkerMsg::Imported(results)).ok().unwrap();
 		assert_eq!(link_port.recv(), Ok(LinkMsg::BlockImported));
 

core/consensus/common/src/lib.rs

@@ -47,7 +47,9 @@ pub mod evaluation;
 const MAX_BLOCK_SIZE: usize = 4 * 1024 * 1024 + 512;
 
 pub use self::error::{Error, ErrorKind};
-pub use block_import::{BlockImport, JustificationImport, ImportBlock, BlockOrigin, ImportResult, ForkChoiceStrategy};
+pub use block_import::{
+	BlockImport, BlockOrigin, ForkChoiceStrategy, ImportedAux, ImportBlock, ImportResult, JustificationImport,
+};
 
 /// Trait for getting the authorities at a given block.
 pub trait Authorities<B: Block> {

core/finality-grandpa/Cargo.toml

@@ -17,8 +17,10 @@ runtime_primitives = { package = "sr-primitives", path = "../sr-primitives" }
 consensus_common = { package = "substrate-consensus-common", path = "../consensus/common" }
 substrate-primitives = { path = "../primitives" }
 client = { package = "substrate-client", path = "../client" }
+inherents = { package = "substrate-inherents", path = "../../core/inherents" }
 network = { package = "substrate-network", path = "../network" }
 service = { package = "substrate-service", path = "../service", optional = true }
+srml-finality-tracker = { path = "../../srml/finality-tracker" }
 fg_primitives = { package = "substrate-finality-grandpa-primitives", path = "primitives" }
 grandpa = { package = "finality-grandpa", version = "0.6.0", features = ["derive-codec"] }
 

core/finality-grandpa/primitives/src/lib.rs

@@ -61,6 +61,7 @@ decl_runtime_apis! {
 	/// applied in the runtime after those N blocks have passed.
 	///
 	/// The consensus protocol will coordinate the handoff externally.
+	#[api_version(2)]
 	pub trait GrandpaApi {
 		/// Check a digest for pending changes.
 		/// Return `None` if there are no pending changes.
@@ -77,6 +78,28 @@ decl_runtime_apis! {
 		fn grandpa_pending_change(digest: &DigestFor<Block>)
 			-> Option<ScheduledChange<NumberFor<Block>>>;
 
+		/// Check a digest for forced changes.
+		/// Return `None` if there are no forced changes. Otherwise, return a
+		/// tuple containing the pending change and the median last finalized
+		/// block number at the time the change was signalled.
+		///
+		/// Added in version 2.
+		///
+		/// Forced changes are applied after a delay of _imported_ blocks,
+		/// while pending changes are applied after a delay of _finalized_ blocks.
+		///
+		/// Precedence towards earlier or later digest items can be given
+		/// based on the rules of the chain.
+		///
+		/// No change should be scheduled if one is already and the delay has not
+		/// passed completely.
+		///
+		/// This should be a pure function: i.e. as long as the runtime can interpret
+		/// the digest type it should return the same result regardless of the current
+		/// state.
+		fn grandpa_forced_change(digest: &DigestFor<Block>)
+			-> Option<(NumberFor<Block>, ScheduledChange<NumberFor<Block>>)>;
+
 		/// Get the current GRANDPA authorities and weights. This should not change except
 		/// for when changes are scheduled and the corresponding delay has passed.
 		///