BABE's revert procedure (#11022)

* First rough draft for BABE revert * Proper babe revert test * Cleanup * Test trivial cleanup * Fix to make clippy happy * Check polkadot companion * Check cumulus companion * Remove babe's blocks weight on revert * Handle "empty" blockchain edge case * Run companions * Simplify the filter predicate * Saturating sub is not required * Run pipeline * Run pipeline again...
2026-06-09 20:11:09 +00:00 · 2022-03-24 09:51:55 +01:00
parent 208be86934
commit c534e00ffc
7 changed files with 314 additions and 22 deletions
@@ -92,8 +92,8 @@ use retain_mut::RetainMut;
 use schnorrkel::SignatureError;

 use sc_client_api::{
-	backend::AuxStore, AuxDataOperations, BlockchainEvents, FinalityNotification, PreCommitActions,
-	ProvideUncles, UsageProvider,
+	backend::AuxStore, AuxDataOperations, Backend as BackendT, BlockchainEvents,
+	FinalityNotification, PreCommitActions, ProvideUncles, UsageProvider,
 };
 use sc_consensus::{
 	block_import::{
@@ -113,7 +113,9 @@ use sc_telemetry::{telemetry, TelemetryHandle, CONSENSUS_DEBUG, CONSENSUS_TRACE}
 use sp_api::{ApiExt, ProvideRuntimeApi};
 use sp_application_crypto::AppKey;
 use sp_block_builder::BlockBuilder as BlockBuilderApi;
-use sp_blockchain::{Error as ClientError, HeaderBackend, HeaderMetadata, Result as ClientResult};
+use sp_blockchain::{
+	Backend as _, Error as ClientError, HeaderBackend, HeaderMetadata, Result as ClientResult,
+};
 use sp_consensus::{
 	BlockOrigin, CacheKeyId, CanAuthorWith, Environment, Error as ConsensusError, Proposer,
 	SelectChain,
@@ -1830,3 +1832,74 @@ where

 	Ok(BasicQueue::new(verifier, Box::new(block_import), justification_import, spawner, registry))
 }
+
+/// Reverts aux data.
+pub fn revert<Block, Client, Backend>(
+	client: Arc<Client>,
+	backend: Arc<Backend>,
+	blocks: NumberFor<Block>,
+) -> ClientResult<()>
+where
+	Block: BlockT,
+	Client: AuxStore
+		+ HeaderMetadata<Block, Error = sp_blockchain::Error>
+		+ HeaderBackend<Block>
+		+ ProvideRuntimeApi<Block>
+		+ UsageProvider<Block>,
+	Client::Api: BabeApi<Block>,
+	Backend: BackendT<Block>,
+{
+	let best_number = client.info().best_number;
+	let finalized = client.info().finalized_number;
+	let revertible = blocks.min(best_number - finalized);
+
+	let number = best_number - revertible;
+	let hash = client
+		.block_hash_from_id(&BlockId::Number(number))?
+		.ok_or(ClientError::Backend(format!(
+			"Unexpected hash lookup failure for block number: {}",
+			number
+		)))?;
+
+	// Revert epoch changes tree.
+
+	let config = Config::get(&*client)?;
+	let epoch_changes =
+		aux_schema::load_epoch_changes::<Block, Client>(&*client, config.genesis_config())?;
+	let mut epoch_changes = epoch_changes.shared_data();
+
+	if number == Zero::zero() {
+		// Special case, no epoch changes data were present on genesis.
+		*epoch_changes = EpochChangesFor::<Block, Epoch>::default();
+	} else {
+		epoch_changes.revert(descendent_query(&*client), hash, number);
+	}
+
+	// Remove block weights added after the revert point.
+
+	let mut weight_keys = HashSet::with_capacity(revertible.saturated_into());
+	let leaves = backend.blockchain().leaves()?.into_iter().filter(|&leaf| {
+		sp_blockchain::tree_route(&*client, hash, leaf)
+			.map(|route| route.retracted().is_empty())
+			.unwrap_or_default()
+	});
+	for leaf in leaves {
+		let mut hash = leaf;
+		// Insert parent after parent until we don't hit an already processed
+		// branch or we reach a direct child of the rollback point.
+		while weight_keys.insert(aux_schema::block_weight_key(hash)) {
+			let meta = client.header_metadata(hash)?;
+			if meta.number <= number + One::one() {
+				// We've reached a child of the revert point, stop here.
+				break
+			}
+			hash = client.header_metadata(hash)?.parent;
+		}
+	}
+	let weight_keys: Vec<_> = weight_keys.iter().map(|val| val.as_slice()).collect();
+
+	// Write epoch changes and remove weights in one shot.
+	aux_schema::write_epoch_changes::<Block, _, _>(&epoch_changes, |values| {
+		client.insert_aux(values, weight_keys.iter())
+	})
+}
@@ -735,6 +735,88 @@ fn importing_block_one_sets_genesis_epoch() {
 	assert_eq!(epoch_for_second_block, genesis_epoch);
 }

+#[test]
+fn revert_prunes_epoch_changes_and_removes_weights() {
+	let mut net = BabeTestNet::new(1);
+
+	let peer = net.peer(0);
+	let data = peer.data.as_ref().expect("babe link set up during initialization");
+
+	let client = peer.client().as_client();
+	let backend = peer.client().as_backend();
+	let mut block_import = data.block_import.lock().take().expect("import set up during init");
+	let epoch_changes = data.link.epoch_changes.clone();
+
+	let mut proposer_factory = DummyFactory {
+		client: client.clone(),
+		config: data.link.config.clone(),
+		epoch_changes: data.link.epoch_changes.clone(),
+		mutator: Arc::new(|_, _| ()),
+	};
+
+	let mut propose_and_import_blocks_wrap = |parent_id, n| {
+		propose_and_import_blocks(&client, &mut proposer_factory, &mut block_import, parent_id, n)
+	};
+
+	// Test scenario.
+	// Information for epoch 19 is produced on three different forks at block #13.
+	// One branch starts before the revert point (epoch data should be maintained).
+	// One branch starts after the revert point (epoch data should be removed).
+	//
+	//                        *----------------- F(#13) --#18                  < fork #2
+	//                       /
+	// A(#1) ---- B(#7) ----#8----+-----#12----- C(#13) ---- D(#19) ------#21  < canon
+	//   \                        ^       \
+	//    \                    revert      *---- G(#13) ---- H(#19) ---#20     < fork #3
+	//     \                   to #10
+	//      *-----E(#7)---#11                                          < fork #1
+	let canon = propose_and_import_blocks_wrap(BlockId::Number(0), 21);
+	let fork1 = propose_and_import_blocks_wrap(BlockId::Hash(canon[0]), 10);
+	let fork2 = propose_and_import_blocks_wrap(BlockId::Hash(canon[7]), 10);
+	let fork3 = propose_and_import_blocks_wrap(BlockId::Hash(canon[11]), 8);
+
+	// We should be tracking a total of 9 epochs in the fork tree
+	assert_eq!(epoch_changes.shared_data().tree().iter().count(), 8);
+	// And only one root
+	assert_eq!(epoch_changes.shared_data().tree().roots().count(), 1);
+
+	// Revert canon chain to block #10 (best(21) - 11)
+	revert(client.clone(), backend, 11).expect("revert should work for baked test scenario");
+
+	// Load and check epoch changes.
+
+	let actual_nodes = aux_schema::load_epoch_changes::<Block, TestClient>(
+		&*client,
+		data.link.config.genesis_config(),
+	)
+	.expect("load epoch changes")
+	.shared_data()
+	.tree()
+	.iter()
+	.map(|(h, _, _)| *h)
+	.collect::<Vec<_>>();
+
+	let expected_nodes = vec![
+		canon[0], // A
+		canon[6], // B
+		fork2[4], // F
+		fork1[5], // E
+	];
+
+	assert_eq!(actual_nodes, expected_nodes);
+
+	let weight_data_check = |hashes: &[Hash], expected: bool| {
+		hashes.iter().all(|hash| {
+			aux_schema::load_block_weight(&*client, hash).unwrap().is_some() == expected
+		})
+	};
+	assert!(weight_data_check(&canon[..10], true));
+	assert!(weight_data_check(&canon[10..], false));
+	assert!(weight_data_check(&fork1, true));
+	assert!(weight_data_check(&fork2, true));
+	assert!(weight_data_check(&fork3, false));
+}
+
 #[test]
 fn importing_epoch_change_block_prunes_tree() {
 	let mut net = BabeTestNet::new(1);