grandpa: Re-add Grandpa runtime API for genesis authority set.

Author: jimpo

Cargo.lock

@@ -44,7 +44,7 @@
 //!    4. Adds the retrieved external addresses as priority nodes to the peerset.
 
 use authority_discovery_primitives::{AuthorityDiscoveryApi, AuthorityId, Signature};
-use client::{blockchain::HeaderBackend, runtime_api::StorageProof};
+use client::blockchain::HeaderBackend;
 use error::{Error, Result};
 use futures::{prelude::*, sync::mpsc::Receiver};
 use log::{debug, error, log_enabled, warn};

core/authority-discovery/src/lib.rs

@@ -5,6 +5,7 @@ authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
+client = { package = "substrate-client", path = "../../client", default-features = false }
 app-crypto = { package = "substrate-application-crypto", path = "../../application-crypto", default-features = false }
 codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 sr-primitives = { path = "../../sr-primitives", default-features = false }
@@ -14,6 +15,7 @@ serde = { version = "1.0.101", optional = true, features = ["derive"] }
 [features]
 default = ["std"]
 std = [
+	"client/std",
 	"codec/std",
 	"sr-primitives/std",
 	"rstd/std",

core/finality-grandpa/primitives/Cargo.toml

@@ -25,6 +25,7 @@ extern crate alloc;
 use serde::Serialize;
 use codec::{Encode, Decode, Input, Codec};
 use sr_primitives::{ConsensusEngineId, RuntimeDebug};
+use client::decl_runtime_apis;
 use rstd::borrow::Cow;
 use rstd::vec::Vec;
 
@@ -209,3 +210,25 @@ impl<'a> Decode for VersionedAuthorityList<'a> {
 		Ok(authorities.into())
 	}
 }
+
+decl_runtime_apis! {
+	/// APIs for integrating the GRANDPA finality gadget into runtimes.
+	/// This should be implemented on the runtime side.
+	///
+	/// This is primarily used for negotiating authority-set changes for the
+	/// gadget. GRANDPA uses a signaling model of changing authority sets:
+	/// changes should be signaled with a delay of N blocks, and then automatically
+	/// applied in the runtime after those N blocks have passed.
+	///
+	/// The consensus protocol will coordinate the handoff externally.
+	#[api_version(2)]
+	pub trait GrandpaApi {
+		/// Get the current GRANDPA authorities and weights. This should not change except
+		/// for when changes are scheduled and the corresponding delay has passed.
+		///
+		/// When called at block B, it will return the set of authorities that should be
+		/// used to finalize descendants of this block (B+1, B+2, ...). The block B itself
+		/// is finalized by the authorities from block B-1.
+		fn grandpa_authorities() -> AuthorityList;
+	}
+}

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

@@ -57,9 +57,10 @@ use log::{debug, error, info};
 use futures::sync::mpsc;
 use client::{
 	BlockchainEvents, CallExecutor, Client, backend::Backend, error::Error as ClientError,
+	ExecutionStrategy,
 };
 use client::blockchain::HeaderBackend;
-use codec::Encode;
+use codec::{Decode, Encode};
 use sr_primitives::generic::BlockId;
 use sr_primitives::traits::{NumberFor, Block as BlockT, DigestFor, Zero};
 use keystore::KeyStorePtr;
@@ -377,9 +378,20 @@ impl<B, E, Block: BlockT<Hash=H256>, RA> GenesisAuthoritySetProvider<Block> for
 		RA: Send + Sync,
 {
 	fn get(&self) -> Result<AuthorityList, ClientError> {
-		use finality_proof::AuthoritySetForFinalityProver;
-
-		self.authorities(&BlockId::Number(Zero::zero()))
+		self.executor()
+			.call(
+				&BlockId::Number(Zero::zero()),
+				"GrandpaApi_grandpa_authorities",
+				&[],
+				ExecutionStrategy::NativeElseWasm,
+				None,
+			)
+			.and_then(|call_result| {
+				Decode::decode(&mut &call_result[..])
+					.map_err(|err| ClientError::CallResultDecode(
+						"failed to decode GRANDPA authorities set proof".into(), err
+					))
+			})
 	}
 }
 

core/finality-grandpa/src/lib.rs

@@ -39,7 +39,7 @@ use codec::Decode;
 use sr_primitives::traits::{ApiRef, ProvideRuntimeApi, Header as HeaderT};
 use sr_primitives::generic::{BlockId, DigestItem};
 use primitives::{NativeOrEncoded, ExecutionContext, crypto::Public};
-use fg_primitives::{GRANDPA_ENGINE_ID, AuthorityList};
+use fg_primitives::{GRANDPA_ENGINE_ID, AuthorityList, GrandpaApi};
 use state_machine::{backend::InMemory, prove_read, read_proof_check};
 
 use authorities::AuthoritySet;
@@ -199,13 +199,15 @@ impl TestApi {
 	}
 }
 
-pub(crate) struct RuntimeApi;
+pub(crate) struct RuntimeApi {
+	inner: TestApi,
+}
 
 impl ProvideRuntimeApi for TestApi {
 	type Api = RuntimeApi;
 
 	fn runtime_api<'a>(&'a self) -> ApiRef<'a, Self::Api> {
-		RuntimeApi.into()
+		RuntimeApi { inner: self.clone() }.into()
 	}
 }
 
@@ -262,6 +264,18 @@ impl ApiExt<Block> for RuntimeApi {
 	}
 }
 
+impl GrandpaApi<Block> for RuntimeApi {
+	fn GrandpaApi_grandpa_authorities_runtime_api_impl(
+		&self,
+		_: &BlockId<Block>,
+		_: ExecutionContext,
+		_: Option<()>,
+		_: Vec<u8>,
+	) -> Result<NativeOrEncoded<AuthorityList>> {
+		Ok(self.inner.genesis_authorities.clone()).map(NativeOrEncoded::Native)
+	}
+}
+
 impl GenesisAuthoritySetProvider<Block> for TestApi {
 	fn get(&self) -> Result<AuthorityList> {
 		Ok(self.genesis_authorities.clone())

core/finality-grandpa/src/tests.rs

@@ -23,7 +23,8 @@ use client::{
 	runtime_api as client_api, impl_runtime_apis
 };
 use aura_primitives::sr25519::AuthorityId as AuraId;
-use grandpa::AuthorityId as GrandpaId;
+use grandpa::AuthorityList as GrandpaAuthorityList;
+use grandpa::fg_primitives;
 use version::RuntimeVersion;
 #[cfg(feature = "std")]
 use version::NativeVersion;
@@ -352,4 +353,10 @@ impl_runtime_apis! {
 			opaque::SessionKeys::generate(seed)
 		}
 	}
+
+	impl fg_primitives::GrandpaApi<Block> for Runtime {
+		fn grandpa_authorities() -> GrandpaAuthorityList {
+			Grandpa::grandpa_authorities()
+		}
+	}
 }

node-template/runtime/src/lib.rs

@@ -45,7 +45,8 @@ use version::RuntimeVersion;
 #[cfg(any(feature = "std", test))]
 use version::NativeVersion;
 use primitives::OpaqueMetadata;
-use grandpa::AuthorityId as GrandpaId;
+use grandpa::AuthorityList as GrandpaAuthorityList;
+use grandpa::fg_primitives;
 use im_online::sr25519::{AuthorityId as ImOnlineId};
 use transaction_payment_rpc_runtime_api::RuntimeDispatchInfo;
 use contracts_rpc_runtime_api::ContractExecResult;
@@ -610,6 +611,12 @@ impl_runtime_apis! {
 		}
 	}
 
+	impl fg_primitives::GrandpaApi<Block> for Runtime {
+		fn grandpa_authorities() -> GrandpaAuthorityList {
+			Grandpa::grandpa_authorities()
+		}
+	}
+
 	impl babe_primitives::BabeApi<Block> for Runtime {
 		fn configuration() -> babe_primitives::BabeConfiguration {
 			// The choice of `c` parameter (where `1 - c` represents the

node/runtime/src/lib.rs

@@ -21,6 +21,9 @@
 //!
 //! In the future, it will also handle misbehavior reports, and on-chain
 //! finality notifications.
+//!
+//! For full integration with GRANDPA, the `GrandpaApi` should be implemented.
+//! The necessary items are re-exported via the `fg_primitives` crate.
 
 #![cfg_attr(not(feature = "std"), no_std)]