Make transaction pool prune transactions only of canonical blocks (#6123)

* Make tx pool aware of retracted fork blocks

* Make it compile

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

Co-authored-by: Nikolay Volf <nikvolf@gmail.com>

* Fix doc test

* Simplify the implementation

* Send tree route as arc to prevent heavy clones

* Switch to use `ExtrinsicHash` to make it more clear

* Fix benchmark

Co-authored-by: Nikolay Volf <nikvolf@gmail.com>

substrate/primitives/blockchain/Cargo.toml

@@ -12,7 +12,6 @@ documentation = "https://docs.rs/sp-blockchain"
 [package.metadata.docs.rs]
 targets = ["x86_64-unknown-linux-gnu"]
 
-
 [dependencies]
 log = "0.4.8"
 lru = "0.4.0"

substrate/primitives/blockchain/src/header_metadata.rs

@@ -137,7 +137,8 @@ pub fn tree_route<Block: BlockT, T: HeaderMetadata<Block>>(
 		from = backend.header_metadata(from.parent)?;
 	}
 
-	// add the pivot block. and append the reversed to-branch (note that it's reverse order originals)
+	// add the pivot block. and append the reversed to-branch
+	// (note that it's reverse order originals)
 	let pivot = from_branch.len();
 	from_branch.push(HashAndNumber {
 		number: to.number,
@@ -182,18 +183,24 @@ pub struct HashAndNumber<Block: BlockT> {
 /// Tree route from C to E2. Retracted empty. Common is C, enacted [E1, E2]
 /// C -> E1 -> E2
 /// ```
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub struct TreeRoute<Block: BlockT> {
 	route: Vec<HashAndNumber<Block>>,
 	pivot: usize,
 }
 
 impl<Block: BlockT> TreeRoute<Block> {
-	/// Get a slice of all retracted blocks in reverse order (towards common ancestor)
+	/// Get a slice of all retracted blocks in reverse order (towards common ancestor).
 	pub fn retracted(&self) -> &[HashAndNumber<Block>] {
 		&self.route[..self.pivot]
 	}
 
+	/// Convert into all retracted blocks in reverse order (towards common ancestor).
+	pub fn into_retracted(mut self) -> Vec<HashAndNumber<Block>> {
+		self.route.truncate(self.pivot);
+		self.route
+	}
+
 	/// Get the common ancestor block. This might be one of the two blocks of the
 	/// route.
 	pub fn common_block(&self) -> &HashAndNumber<Block> {
@@ -213,8 +220,15 @@ pub trait HeaderMetadata<Block: BlockT> {
 	/// Error used in case the header metadata is not found.
 	type Error;
 
-	fn header_metadata(&self, hash: Block::Hash) -> Result<CachedHeaderMetadata<Block>, Self::Error>;
-	fn insert_header_metadata(&self, hash: Block::Hash, header_metadata: CachedHeaderMetadata<Block>);
+	fn header_metadata(
+		&self,
+		hash: Block::Hash,
+	) -> Result<CachedHeaderMetadata<Block>, Self::Error>;
+	fn insert_header_metadata(
+		&self,
+		hash: Block::Hash,
+		header_metadata: CachedHeaderMetadata<Block>,
+	);
 	fn remove_header_metadata(&self, hash: Block::Hash);
 }
 

substrate/primitives/transaction-pool/Cargo.toml

@@ -20,6 +20,7 @@ futures = { version = "0.3.1", optional = true }
 log = { version = "0.4.8", optional = true }
 serde = { version = "1.0.101", features = ["derive"], optional = true}
 sp-api = { version = "2.0.0-rc2", default-features = false, path = "../api" }
+sp-blockchain = { version = "2.0.0-rc2", optional = true, path = "../blockchain" }
 sp-runtime = { version = "2.0.0-rc2", default-features = false, path = "../runtime" }
 sp-utils = { version = "2.0.0-rc2", default-features = false, path = "../utils" }
 
@@ -32,5 +33,6 @@ std = [
 	"log",
 	"serde",
 	"sp-api/std",
+	"sp-blockchain",
 	"sp-runtime/std",
 ]

substrate/primitives/transaction-pool/src/pool.rs

@@ -255,8 +255,10 @@ pub enum ChainEvent<B: BlockT> {
 		id: BlockId<B>,
 		/// Header of the just imported block
 		header: B::Header,
-		/// List of retracted blocks ordered by block number.
-		retracted: Vec<B::Hash>,
+		/// Tree route from old best to new best that was calculated on import.
+		///
+		/// If `None`, no re-org happened on import.
+		tree_route: Option<Arc<sp_blockchain::TreeRoute<B>>>,
 	},
 	/// An existing block has been finalized.
 	Finalized {