Companion for: pallet-mmr: move offchain logic to client-side gadget (#6321)

* Spawn MMR gadget when offchain indexing is enabled

* companion PR code review changes: 1st iteration

* Code review changes: 2nd iteration

* update lockfile for {"substrate"}

Co-authored-by: acatangiu <adrian@parity.io>
Co-authored-by: parity-processbot <>

polkadot/node/service/Cargo.toml

@@ -13,6 +13,8 @@ beefy-primitives = { git = "https://github.com/paritytech/substrate", branch = "
 beefy-gadget = { git = "https://github.com/paritytech/substrate", branch = "master" }
 frame-support = { git = "https://github.com/paritytech/substrate", branch = "master" }
 grandpa = { package = "sc-finality-grandpa", git = "https://github.com/paritytech/substrate", branch = "master" }
+mmr-gadget = { git = "https://github.com/paritytech/substrate", branch = "master" }
+sp-mmr-primitives = { git = "https://github.com/paritytech/substrate", branch = "master"}
 sc-block-builder = { git = "https://github.com/paritytech/substrate", branch = "master" }
 sc-chain-spec = { git = "https://github.com/paritytech/substrate", branch = "master" }
 sc-client-api = { git = "https://github.com/paritytech/substrate", branch = "master" }

polkadot/node/service/src/lib.rs

@@ -95,6 +95,7 @@ pub use polkadot_client::PolkadotExecutorDispatch;
 
 pub use chain_spec::{KusamaChainSpec, PolkadotChainSpec, RococoChainSpec, WestendChainSpec};
 pub use consensus_common::{block_validation::Chain, Proposal, SelectChain};
+use mmr_gadget::MmrGadget;
 #[cfg(feature = "full-node")]
 pub use polkadot_client::{
 	AbstractClient, Client, ClientHandle, ExecuteWithClient, FullBackend, FullClient,
@@ -758,6 +759,7 @@ where
 {
 	use polkadot_node_network_protocol::request_response::IncomingRequest;
 
+	let is_offchain_indexing_enabled = config.offchain_worker.indexing_enabled;
 	let role = config.role.clone();
 	let force_authoring = config.force_authoring;
 	let backoff_authoring_blocks = {
@@ -1219,6 +1221,18 @@ where
 		} else {
 			task_manager.spawn_handle().spawn_blocking("beefy-gadget", None, gadget);
 		}
+
+		if is_offchain_indexing_enabled {
+			task_manager.spawn_handle().spawn_blocking(
+				"mmr-gadget",
+				None,
+				MmrGadget::start(
+					client.clone(),
+					backend.clone(),
+					sp_mmr_primitives::INDEXING_PREFIX.to_vec(),
+				),
+			);
+		}
 	}
 
 	let config = grandpa::Config {

polkadot/runtime/kusama/src/lib.rs

@@ -1694,6 +1694,10 @@ sp_api::impl_runtime_apis! {
 			Err(mmr::Error::PalletNotIncluded)
 		}
 
+		fn mmr_leaf_count() -> Result<mmr::LeafIndex, mmr::Error> {
+			Err(mmr::Error::PalletNotIncluded)
+		}
+
 		fn generate_proof(
 			_block_numbers: Vec<BlockNumber>,
 			_best_known_block_number: Option<BlockNumber>,

polkadot/runtime/polkadot/src/lib.rs

@@ -1851,6 +1851,10 @@ sp_api::impl_runtime_apis! {
 			Err(mmr::Error::PalletNotIncluded)
 		}
 
+		fn mmr_leaf_count() -> Result<mmr::LeafIndex, mmr::Error> {
+			Err(mmr::Error::PalletNotIncluded)
+		}
+
 		fn generate_proof(
 			_block_numbers: Vec<BlockNumber>,
 			_best_known_block_number: Option<BlockNumber>,

polkadot/runtime/rococo/src/lib.rs

@@ -1224,7 +1224,7 @@ impl pallet_beefy::Config for Runtime {
 type MmrHash = <Keccak256 as sp_runtime::traits::Hash>::Output;
 
 impl pallet_mmr::Config for Runtime {
-	const INDEXING_PREFIX: &'static [u8] = b"mmr";
+	const INDEXING_PREFIX: &'static [u8] = mmr::INDEXING_PREFIX;
 	type Hashing = Keccak256;
 	type Hash = MmrHash;
 	type OnNewRoot = pallet_beefy_mmr::DepositBeefyDigest<Runtime>;
@@ -1715,6 +1715,10 @@ sp_api::impl_runtime_apis! {
 			Ok(Mmr::mmr_root())
 		}
 
+		fn mmr_leaf_count() -> Result<mmr::LeafIndex, mmr::Error> {
+			Ok(Mmr::mmr_leaves())
+		}
+
 		fn generate_proof(
 			block_numbers: Vec<BlockNumber>,
 			best_known_block_number: Option<BlockNumber>,

polkadot/runtime/test-runtime/src/lib.rs

@@ -930,6 +930,10 @@ sp_api::impl_runtime_apis! {
 			Err(mmr::Error::PalletNotIncluded)
 		}
 
+		fn mmr_leaf_count() -> Result<mmr::LeafIndex, mmr::Error> {
+			Err(mmr::Error::PalletNotIncluded)
+		}
+
 		fn generate_proof(
 			_block_numbers: Vec<BlockNumber>,
 			_best_known_block_number: Option<BlockNumber>,

polkadot/runtime/westend/src/lib.rs

@@ -1450,7 +1450,10 @@ sp_api::impl_runtime_apis! {
 
 	impl mmr::MmrApi<Block, Hash, BlockNumber> for Runtime {
 		fn mmr_root() -> Result<Hash, mmr::Error> {
+			Err(mmr::Error::PalletNotIncluded)
+		}
 
+		fn mmr_leaf_count() -> Result<mmr::LeafIndex, mmr::Error> {
 			Err(mmr::Error::PalletNotIncluded)
 		}