Adds cli interface to allow reseting chain to a particular block (#9782)

* added BlockChainReset trait, client impl, and cli interface

* show block hashes to be deleted and new best block, update best block in db, better cli interface

* delete BlockNumber from COL_EXTRA

* add TODO comment

* add BlockReciepts to imports

* refactor block_headers_from_best_block, better cli documentation

* exit gracefully if reset arg isn't supplied

* fix cli usage macro

* removed stray int literals

* use Vec::with_capacity

Co-Authored-By: seunlanlege <seunlanlege@gmail.com>

* cast n to usize

* correct imports

* make db reset arg required

ethcore/src/client/client.rs

@@ -21,7 +21,7 @@ use std::sync::atomic::{AtomicUsize, AtomicBool, Ordering as AtomicOrdering};
 use std::sync::{Arc, Weak};
 use std::time::{Instant, Duration};
 
-use blockchain::{BlockReceipts, BlockChain, BlockChainDB, BlockProvider, TreeRoute, ImportRoute, TransactionAddress, ExtrasInsert};
+use blockchain::{BlockReceipts, BlockChain, BlockChainDB, BlockProvider, TreeRoute, ImportRoute, TransactionAddress, ExtrasInsert, BlockNumberKey};
 use bytes::Bytes;
 use ethcore_miner::pool::VerifiedTransaction;
 use ethereum_types::{H256, Address, U256};
@@ -50,7 +50,7 @@ use client::{
 	RegistryInfo, ReopenBlock, PrepareOpenBlock, ScheduleInfo, ImportSealedBlock,
 	BroadcastProposalBlock, ImportBlock, StateOrBlock, StateInfo, StateClient, Call,
 	AccountData, BlockChain as BlockChainTrait, BlockProducer, SealedBlockImporter,
-	ClientIoMessage,
+	ClientIoMessage, BlockChainReset
 };
 use client::{
 	BlockId, TransactionId, UncleId, TraceId, ClientConfig, BlockChainClient,
@@ -77,12 +77,14 @@ use verification::queue::kind::BlockLike;
 use verification::queue::kind::blocks::Unverified;
 use verification::{PreverifiedBlock, Verifier, BlockQueue};
 use verification;
+use ansi_term::Colour;
 
 // re-export
 pub use types::blockchain_info::BlockChainInfo;
 pub use types::block_status::BlockStatus;
 pub use blockchain::CacheSize as BlockChainCacheSize;
 pub use verification::QueueInfo as BlockQueueInfo;
+use db::Writable;
 
 use_contract!(registry, "res/contracts/registrar.json");
 
@@ -469,6 +471,7 @@ impl Importer {
 	// it is for reconstructing the state transition.
 	//
 	// The header passed is from the original block data and is sealed.
+	// TODO: should return an error if ImportRoute is none, issue #9910
 	fn commit_block<B>(&self, block: B, header: &Header, block_data: encoded::Block, client: &Client) -> ImportRoute where B: Drain {
 		let hash = &header.hash();
 		let number = header.number();
@@ -1328,6 +1331,48 @@ impl snapshot::DatabaseRestore for Client {
 	}
 }
 
+impl BlockChainReset for Client {
+	fn reset(&self, num: u32) -> Result<(), String> {
+		if num as u64 > self.pruning_history() {
+			return Err("Attempting to reset to block with pruned state".into())
+		}
+
+		let (blocks_to_delete, best_block_hash) = self.chain.read()
+			.block_headers_from_best_block(num)
+			.ok_or("Attempted to reset past genesis block")?;
+
+		let mut db_transaction = DBTransaction::with_capacity((num + 1) as usize);
+
+		for hash in &blocks_to_delete {
+			db_transaction.delete(::db::COL_HEADERS, &hash.hash());
+			db_transaction.delete(::db::COL_BODIES, &hash.hash());
+			db_transaction.delete(::db::COL_EXTRA, &hash.hash());
+			Writable::delete::<H256, BlockNumberKey>
+				(&mut db_transaction, ::db::COL_EXTRA, &hash.number());
+		}
+
+		// update the new best block hash
+		db_transaction.put(::db::COL_EXTRA, b"best", &*best_block_hash);
+
+		self.db.read()
+			.key_value()
+			.write(db_transaction)
+			.map_err(|err| format!("could not complete reset operation; io error occured: {}", err))?;
+
+		let hashes = blocks_to_delete.iter().map(|b| b.hash()).collect::<Vec<_>>();
+
+		info!("Deleting block hashes {}",
+			Colour::Red
+				.bold()
+				.paint(format!("{:#?}", hashes))
+		);
+
+		info!("New best block hash {}", Colour::Green.bold().paint(format!("{:?}", best_block_hash)));
+
+		Ok(())
+	}
+}
+
 impl Nonce for Client {
 	fn nonce(&self, address: &Address, id: BlockId) -> Option<U256> {
 		self.state_at(id).and_then(|s| s.nonce(address).ok())

ethcore/src/client/mod.rs

@@ -37,7 +37,8 @@ pub use self::test_client::{TestBlockChainClient, EachBlockWith};
 pub use self::chain_notify::{ChainNotify, NewBlocks, ChainRoute, ChainRouteType, ChainMessageType};
 pub use self::traits::{
     Nonce, Balance, ChainInfo, BlockInfo, ReopenBlock, PrepareOpenBlock, CallContract, TransactionInfo, RegistryInfo, ScheduleInfo, ImportSealedBlock, BroadcastProposalBlock, ImportBlock,
-    StateOrBlock, StateClient, Call, EngineInfo, AccountData, BlockChain, BlockProducer, SealedBlockImporter, BadBlocks,
+    StateOrBlock, StateClient, Call, EngineInfo, AccountData, BlockChain, BlockProducer, SealedBlockImporter,
+	BadBlocks, BlockChainReset
 };
 pub use state::StateInfo;
 pub use self::traits::{BlockChainClient, EngineClient, ProvingBlockChainClient, IoClient};

ethcore/src/client/traits.rs

@@ -482,3 +482,9 @@ pub trait ProvingBlockChainClient: BlockChainClient {
 	/// Get an epoch change signal by block hash.
 	fn epoch_signal(&self, hash: H256) -> Option<Vec<u8>>;
 }
+
+/// resets the blockchain
+pub trait BlockChainReset {
+	/// reset to best_block - n
+	fn reset(&self, num: u32) -> Result<(), String>;
+}