Make offchain tx pool creation reusable (paritytech#14230)

* Make offchain tx pool creation reusable

Introduces an `OffchainTransactionPoolFactory` for creating offchain transactions pools that can be
registered in the runtime externalities context. This factory will be required for a later pr to
make the creation of offchain transaction pools easier.

* Update client/transaction-pool/api/src/lib.rs

Co-authored-by: Anton <[email protected]>

---------

Co-authored-by: Anton <[email protected]>

client/api/src/execution_extensions.rs

@@ -22,20 +22,16 @@
 //! strategy for the runtime calls and provide the right `Externalities`
 //! extensions to support APIs for particular execution context & capabilities.
 
-use codec::Decode;
 use parking_lot::RwLock;
-use sc_transaction_pool_api::OffchainSubmitTransaction;
+use sc_transaction_pool_api::OffchainTransactionPoolFactory;
 use sp_core::{
-	offchain::{self, OffchainDbExt, OffchainWorkerExt, TransactionPoolExt},
+	offchain::{self, OffchainDbExt, OffchainWorkerExt},
 	traits::{ReadRuntimeVersion, ReadRuntimeVersionExt},
 	ExecutionContext,
 };
 use sp_externalities::{Extension, Extensions};
 use sp_keystore::{KeystoreExt, KeystorePtr};
-use sp_runtime::{
-	generic::BlockId,
-	traits::{Block as BlockT, NumberFor},
-};
+use sp_runtime::traits::{Block as BlockT, NumberFor};
 pub use sp_state_machine::ExecutionStrategy;
 use sp_state_machine::{DefaultHandler, ExecutionManager};
 use std::{
@@ -168,11 +164,7 @@ pub struct ExecutionExtensions<Block: BlockT> {
 	offchain_db: Option<Box<dyn DbExternalitiesFactory>>,
 	// FIXME: these three are only RwLock because of https://github.com/paritytech/substrate/issues/4587
 	//        remove when fixed.
-	// To break retain cycle between `Client` and `TransactionPool` we require this
-	// extension to be a `Weak` reference.
-	// That's also the reason why it's being registered lazily instead of
-	// during initialization.
-	transaction_pool: RwLock<Option<Weak<dyn OffchainSubmitTransaction<Block>>>>,
+	transaction_pool_factory: RwLock<Option<OffchainTransactionPoolFactory<Block>>>,
 	extensions_factory: RwLock<Box<dyn ExtensionsFactory<Block>>>,
 	statement_store: RwLock<Option<Weak<dyn sp_statement_store::StatementStore>>>,
 	read_runtime_version: Arc<dyn ReadRuntimeVersion>,
@@ -194,7 +186,7 @@ impl<Block: BlockT> ExecutionExtensions<Block> {
 			keystore,
 			offchain_db,
 			extensions_factory: RwLock::new(extensions_factory),
-			transaction_pool,
+			transaction_pool_factory: transaction_pool,
 			statement_store,
 			read_runtime_version,
 		}
@@ -211,11 +203,11 @@ impl<Block: BlockT> ExecutionExtensions<Block> {
 	}
 
 	/// Register transaction pool extension.
-	pub fn register_transaction_pool<T>(&self, pool: &Arc<T>)
-	where
-		T: OffchainSubmitTransaction<Block> + 'static,
-	{
-		*self.transaction_pool.write() = Some(Arc::downgrade(pool) as _);
+	pub fn register_transaction_pool_factory(
+		&self,
+		factory: OffchainTransactionPoolFactory<Block>,
+	) {
+		*self.transaction_pool_factory.write() = Some(factory);
 	}
 
 	/// Register statement store extension.
@@ -245,11 +237,8 @@ impl<Block: BlockT> ExecutionExtensions<Block> {
 		}
 
 		if capabilities.contains(offchain::Capabilities::TRANSACTION_POOL) {
-			if let Some(pool) = self.transaction_pool.read().as_ref().and_then(|x| x.upgrade()) {
-				extensions.register(TransactionPoolExt(Box::new(TransactionPoolAdapter {
-					at: BlockId::Hash(block_hash),
-					pool,
-				}) as _));
+			if let Some(pool) = self.transaction_pool_factory.read().as_ref() {
+				extensions.register(pool.offchain_transaction_pool(block_hash));
 			}
 		}
 
@@ -303,23 +292,3 @@ impl<Block: BlockT> ExecutionExtensions<Block> {
 		(manager, self.extensions(block_hash, block_number, context))
 	}
 }
-
-/// A wrapper type to pass `BlockId` to the actual transaction pool.
-struct TransactionPoolAdapter<Block: BlockT> {
-	at: BlockId<Block>,
-	pool: Arc<dyn OffchainSubmitTransaction<Block>>,
-}
-
-impl<Block: BlockT> offchain::TransactionPool for TransactionPoolAdapter<Block> {
-	fn submit_transaction(&mut self, data: Vec<u8>) -> Result<(), ()> {
-		let xt = match Block::Extrinsic::decode(&mut &*data) {
-			Ok(xt) => xt,
-			Err(e) => {
-				log::warn!("Unable to decode extrinsic: {:?}: {}", data, e);
-				return Err(())
-			},
-		};
-
-		self.pool.submit_at(&self.at, xt)
-	}
-}

client/offchain/src/lib.rs

@@ -247,16 +247,15 @@ mod tests {
 	use sc_block_builder::BlockBuilderProvider as _;
 	use sc_client_api::Backend as _;
 	use sc_network::{config::MultiaddrWithPeerId, types::ProtocolName, ReputationChange};
-	use sc_transaction_pool::{BasicPool, FullChainApi};
+	use sc_transaction_pool::BasicPool;
 	use sc_transaction_pool_api::{InPoolTransaction, TransactionPool};
 	use sp_consensus::BlockOrigin;
-	use sp_runtime::generic::BlockId;
 	use std::{collections::HashSet, sync::Arc};
 	use substrate_test_runtime_client::{
 		runtime::{
-			substrate_test_pallet::pallet::Call as PalletCall, Block, ExtrinsicBuilder, RuntimeCall,
+			substrate_test_pallet::pallet::Call as PalletCall, ExtrinsicBuilder, RuntimeCall,
 		},
-		ClientBlockImportExt, DefaultTestClientBuilderExt, TestClient, TestClientBuilderExt,
+		ClientBlockImportExt, DefaultTestClientBuilderExt, TestClientBuilderExt,
 	};
 
 	struct TestNetwork();
@@ -337,34 +336,14 @@ mod tests {
 		}
 	}
 
-	struct TestPool(Arc<BasicPool<FullChainApi<TestClient, Block>, Block>>);
-
-	impl sc_transaction_pool_api::OffchainSubmitTransaction<Block> for TestPool {
-		fn submit_at(
-			&self,
-			at: &BlockId<Block>,
-			extrinsic: <Block as traits::Block>::Extrinsic,
-		) -> Result<(), ()> {
-			let source = sc_transaction_pool_api::TransactionSource::Local;
-			futures::executor::block_on(self.0.submit_one(&at, source, extrinsic))
-				.map(|_| ())
-				.map_err(|_| ())
-		}
-	}
-
 	#[test]
 	fn should_call_into_runtime_and_produce_extrinsic() {
 		sp_tracing::try_init_simple();
 
 		let client = Arc::new(substrate_test_runtime_client::new());
 		let spawner = sp_core::testing::TaskExecutor::new();
-		let pool = TestPool(BasicPool::new_full(
-			Default::default(),
-			true.into(),
-			None,
-			spawner,
-			client.clone(),
-		));
+		let pool =
+			BasicPool::new_full(Default::default(), true.into(), None, spawner, client.clone());
 		let network = Arc::new(TestNetwork());
 		let header = client.header(client.chain_info().genesis_hash).unwrap().unwrap();
 
@@ -373,9 +352,9 @@ mod tests {
 		futures::executor::block_on(offchain.on_block_imported(&header, network, false));
 
 		// then
-		assert_eq!(pool.0.status().ready, 1);
+		assert_eq!(pool.status().ready, 1);
 		assert!(matches!(
-			pool.0.ready().next().unwrap().data().function,
+			pool.ready().next().unwrap().data().function,
 			RuntimeCall::SubstrateTest(PalletCall::storage_change { .. })
 		));
 	}

client/transaction-pool/api/Cargo.toml

@@ -10,11 +10,13 @@ description = "Transaction pool client facing API."
 
 [dependencies]
 async-trait = "0.1.57"
+codec = { package = "parity-scale-codec", version = "3.2.2" }
 futures = "0.3.21"
 log = "0.4.17"
 serde = { version = "1.0.136", features = ["derive"] }
 thiserror = "1.0.30"
 sp-blockchain = { version = "4.0.0-dev", path = "../../../primitives/blockchain" }
+sp-core = { version = "8.0.0", default-features = false, path = "../../../primitives/core" }
 sp-runtime = { version = "8.0.0", default-features = false, path = "../../../primitives/runtime" }
 
 [dev-dependencies]

client/transaction-pool/api/src/lib.rs

@@ -24,11 +24,17 @@ pub mod error;
 use async_trait::async_trait;
 use futures::{Future, Stream};
 use serde::{de::DeserializeOwned, Deserialize, Serialize};
+use sp_core::offchain::TransactionPoolExt;
 use sp_runtime::{
 	generic::BlockId,
 	traits::{Block as BlockT, Member, NumberFor},
 };
-use std::{collections::HashMap, hash::Hash, pin::Pin, sync::Arc};
+use std::{
+	collections::HashMap,
+	hash::Hash,
+	pin::Pin,
+	sync::{Arc, Weak},
+};
 
 const LOG_TARGET: &str = "txpool::api";
 
@@ -329,29 +335,27 @@ pub trait LocalTransactionPool: Send + Sync {
 	/// `TransactionSource::Local`.
 	fn submit_local(
 		&self,
-		at: &BlockId<Self::Block>,
+		at: <Self::Block as BlockT>::Hash,
 		xt: LocalTransactionFor<Self>,
 	) -> Result<Self::Hash, Self::Error>;
 }
 
-/// An abstraction for transaction pool.
+/// An abstraction for [`LocalTransactionPool`]
 ///
-/// This trait is used by offchain calls to be able to submit transactions.
-/// The main use case is for offchain workers, to feed back the results of computations,
-/// but since the transaction pool access is a separate `ExternalitiesExtension` it can
-/// be also used in context of other offchain calls. For one may generate and submit
-/// a transaction for some misbehavior reports (say equivocation).
-pub trait OffchainSubmitTransaction<Block: BlockT>: Send + Sync {
+/// We want to use a transaction pool in [`OffchainTransactionPoolFactory`] in a `Arc` without
+/// bleeding the associated types besides the `Block`. Thus, this abstraction here exists to achieve
+/// the wrapping in a `Arc`.
+trait OffchainSubmitTransaction<Block: BlockT>: Send + Sync {
 	/// Submit transaction.
 	///
 	/// The transaction will end up in the pool and be propagated to others.
-	fn submit_at(&self, at: &BlockId<Block>, extrinsic: Block::Extrinsic) -> Result<(), ()>;
+	fn submit_at(&self, at: Block::Hash, extrinsic: Block::Extrinsic) -> Result<(), ()>;
 }
 
 impl<TPool: LocalTransactionPool> OffchainSubmitTransaction<TPool::Block> for TPool {
 	fn submit_at(
 		&self,
-		at: &BlockId<TPool::Block>,
+		at: <TPool::Block as BlockT>::Hash,
 		extrinsic: <TPool::Block as BlockT>::Extrinsic,
 	) -> Result<(), ()> {
 		log::debug!(
@@ -372,6 +376,56 @@ impl<TPool: LocalTransactionPool> OffchainSubmitTransaction<TPool::Block> for TP
 	}
 }
 
+/// Factory for creating [`TransactionPoolExt`]s.
+///
+/// This provides an easy way for creating [`TransactionPoolExt`] extensions for registering them in
+/// the wasm execution environment to send transactions from an offchain call to the  runtime.
+#[derive(Clone)]
+pub struct OffchainTransactionPoolFactory<Block: BlockT> {
+	// To break retain cycle between `Client` and `TransactionPool` we require this
+	// extension to be a `Weak` reference.
+	pool: Weak<dyn OffchainSubmitTransaction<Block>>,
+}
+
+impl<Block: BlockT> OffchainTransactionPoolFactory<Block> {
+	/// Creates a new instance using the given `tx_pool`.
+	pub fn new<T: LocalTransactionPool<Block = Block> + 'static>(tx_pool: &Arc<T>) -> Self {
+		Self { pool: Arc::downgrade(tx_pool) as Weak<_> }
+	}
+
+	/// Returns an instance of [`TransactionPoolExt`] bound to the given `block_hash`.
+	///
+	/// Transactions that are being submitted by this instance will be submitted with `block_hash`
+	/// as context for validation.
+	pub fn offchain_transaction_pool(&self, block_hash: Block::Hash) -> TransactionPoolExt {
+		TransactionPoolExt::new(OffchainTransactionPool { pool: self.pool.clone(), block_hash })
+	}
+}
+
+/// Wraps a `pool` and `block_hash` to implement [`sp_core::offchain::TransactionPool`].
+struct OffchainTransactionPool<Block: BlockT> {
+	block_hash: Block::Hash,
+	pool: Weak<dyn OffchainSubmitTransaction<Block>>,
+}
+
+impl<Block: BlockT> sp_core::offchain::TransactionPool for OffchainTransactionPool<Block> {
+	fn submit_transaction(&mut self, extrinsic: Vec<u8>) -> Result<(), ()> {
+		let extrinsic = match codec::Decode::decode(&mut &extrinsic[..]) {
+			Ok(t) => t,
+			Err(e) => {
+				log::error!(
+					target: LOG_TARGET,
+					"Failed to decode extrinsic in `OffchainTransactionPool::submit_transaction`: {e:?}"
+				);
+
+				return Err(())
+			},
+		};
+
+		self.pool.upgrade().ok_or(())?.submit_at(self.block_hash, extrinsic)
+	}
+}
+
 /// Wrapper functions to keep the API backwards compatible over the wire for the old RPC spec.
 mod v1_compatible {
 	use serde::{Deserialize, Deserializer, Serialize, Serializer};

client/transaction-pool/src/lib.rs

@@ -52,8 +52,8 @@ use std::{
 use graph::{ExtrinsicHash, IsValidator};
 use sc_transaction_pool_api::{
 	error::Error as TxPoolError, ChainEvent, ImportNotificationStream, MaintainedTransactionPool,
-	PoolFuture, PoolStatus, ReadyTransactions, TransactionFor, TransactionPool, TransactionSource,
-	TransactionStatusStreamFor, TxHash,
+	OffchainTransactionPoolFactory, PoolFuture, PoolStatus, ReadyTransactions, TransactionFor,
+	TransactionPool, TransactionSource, TransactionStatusStreamFor, TxHash,
 };
 use sp_core::traits::SpawnEssentialNamed;
 use sp_runtime::{
@@ -397,7 +397,9 @@ where
 		));
 
 		// make transaction pool available for off-chain runtime calls.
-		client.execution_extensions().register_transaction_pool(&pool);
+		client
+			.execution_extensions()
+			.register_transaction_pool_factory(OffchainTransactionPoolFactory::new(&pool));
 
 		pool
 	}
@@ -421,7 +423,7 @@ where
 
 	fn submit_local(
 		&self,
-		at: &BlockId<Self::Block>,
+		at: Block::Hash,
 		xt: sc_transaction_pool_api::LocalTransactionFor<Self>,
 	) -> Result<Self::Hash, Self::Error> {
 		use sp_runtime::{
@@ -430,7 +432,11 @@ where
 
 		let validity = self
 			.api
-			.validate_transaction_blocking(at, TransactionSource::Local, xt.clone())?
+			.validate_transaction_blocking(
+				&BlockId::hash(at),
+				TransactionSource::Local,
+				xt.clone(),
+			)?
 			.map_err(|e| {
 				Self::Error::Pool(match e {
 					TransactionValidityError::Invalid(i) => TxPoolError::InvalidTransaction(i),
@@ -441,7 +447,7 @@ where
 		let (hash, bytes) = self.pool.validated_pool().api().hash_and_length(&xt);
 		let block_number = self
 			.api
-			.block_id_to_number(at)?
+			.block_id_to_number(&BlockId::hash(at))?
 			.ok_or_else(|| error::Error::BlockIdConversion(format!("{:?}", at)))?;
 
 		let validated = ValidatedTransaction::valid_at(