snapshot chunk and restore traits

ethcore/src/client/client.rs

@@ -894,7 +894,7 @@ impl Client {
 			},
 		};
 
-		snapshot::take_snapshot(&self.chain.read(), start_hash, db.as_hashdb(), writer, p)?;
+		snapshot::take_snapshot(&*self.engine, &self.chain.read(), start_hash, db.as_hashdb(), writer, p)?;
 
 		Ok(())
 	}

ethcore/src/engines/mod.rs

@@ -45,6 +45,7 @@ use error::{Error, TransactionError};
 use evm::Schedule;
 use header::Header;
 use spec::CommonParams;
+use snapshot::SnapshotComponents;
 use transaction::{UnverifiedTransaction, SignedTransaction};
 use receipt::Receipt;
 
@@ -294,4 +295,10 @@ pub trait Engine : Sync + Send {
 
 	/// Stops any services that the may hold the Engine and makes it safe to drop.
 	fn stop(&self) {}
+
+	/// Create a factory for building snapshot chunks and restoring from them.
+	/// Returning `None` indicates that this engine doesn't support snapshot creation.
+	fn snapshot_components(&self) -> Option<Box<SnapshotComponents>> {
+		None
+	}
 }

ethcore/src/engines/null_engine.rs

@@ -60,4 +60,8 @@ impl Engine for NullEngine {
 	fn schedule(&self, _env_info: &EnvInfo) -> Schedule {
 		Schedule::new_homestead()
 	}
+
+	fn snapshot_components(&self) -> Option<Box<::snapshot::SnapshotComponents>> {
+		Some(Box::new(::snapshot::PowSnapshot))
+	}
 }

ethcore/src/ethereum/ethash.rs

@@ -405,6 +405,10 @@ impl Engine for Arc<Ethash> {
 	fn epoch_verifier(&self, _header: &Header, _proof: &[u8]) -> Result<Box<::engines::EpochVerifier>, Error> {
 		Ok(Box::new(self.clone()))
 	}
+
+	fn snapshot_components(&self) -> Option<Box<::snapshot::SnapshotComponents>> {
+		Some(Box::new(::snapshot::PowSnapshot))
+	}
 }
 
 // Try to round gas_limit a bit so that:

ethcore/src/snapshot/consensus/mod.rs

@@ -0,0 +1,349 @@
+// Copyright 2015-2017 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Secondary chunk creation and restoration, implementations for different consensus
+//! engines.
+
+use std::collections::VecDeque;
+use std::io;
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::Arc;
+
+use blockchain::{BlockChain, BlockProvider};
+use engines::Engine;
+use snapshot::{Error, ManifestData};
+use snapshot::block::AbridgedBlock;
+
+use util::{Bytes, H256};
+use util::kvdb::KeyValueDB;
+use rand::OsRng;
+use rlp::{RlpStream, UntrustedRlp};
+
+
+/// A sink for produced chunks.
+pub type ChunkSink<'a> = FnMut(&[u8]) -> io::Result<()> + 'a;
+
+// How many blocks to include in a snapshot, starting from the head of the chain.
+const SNAPSHOT_BLOCKS: u64 = 30000;
+
+/// Components necessary for snapshot creation and restoration.
+pub trait SnapshotComponents: Send {
+	/// Create secondary snapshot chunks; these corroborate the state data
+	/// in the state chunks.
+	///
+	/// Chunks shouldn't exceed the given preferred size, and should be fed
+	/// uncompressed into the sink.
+	///
+	/// This will vary by consensus engine, so it's exposed as a trait.
+	fn chunk_all(
+		&mut self,
+		chain: &BlockChain,
+		block_at: H256,
+		chunk_sink: &mut ChunkSink,
+		preferred_size: usize,
+	) -> Result<(), Error>;
+
+	/// Create a rebuilder, which will have chunks fed into it in aribtrary
+	/// order and then be finalized.
+	///
+	/// The manifest, a database, and fresh `BlockChain` are supplied.
+	// TODO: supply anything for state?
+	fn rebuilder(
+		&self,
+		chain: BlockChain,
+		db: Arc<KeyValueDB>,
+		manifest: &ManifestData,
+	) -> Result<Box<Rebuilder>, ::error::Error>;
+}
+
+
+/// Restore from secondary snapshot chunks.
+pub trait Rebuilder: Send {
+	/// Feed a chunk, potentially out of order.
+	///
+	/// Check `abort_flag` periodically while doing heavy work. If set to `false`, should bail with
+	/// `Error::RestorationAborted`.
+	fn feed(
+		&mut self,
+		chunk: &[u8],
+		engine: &Engine,
+		abort_flag: &AtomicBool,
+	) -> Result<(), ::error::Error>;
+
+	/// Finalize the restoration. Will be done after all chunks have been
+	/// fed successfully.
+	/// This will apply the necessary "glue" between chunks.
+	fn finalize(&mut self) -> Result<(), Error>;
+}
+
+/// Snapshot creation and restoration for PoW chains.
+/// This includes blocks from the head of the chain as a
+/// loose assurance that the chain is valid.
+pub struct PowSnapshot;
+
+impl SnapshotComponents for PowSnapshot {
+	fn chunk_all(
+		&mut self,
+		chain: &BlockChain,
+		block_at: H256,
+		chunk_sink: &mut ChunkSink,
+		preferred_size: usize,
+	) -> Result<(), Error> {
+		PowWorker {
+			chain: chain,
+			rlps: VecDeque::new(),
+			current_hash: block_at,
+			writer: chunk_sink,
+			preferred_size: preferred_size,
+		}.chunk_all()
+	}
+
+	fn rebuilder(
+		&self,
+		chain: BlockChain,
+		db: Arc<KeyValueDB>,
+		manifest: &ManifestData,
+	) -> Result<Box<Rebuilder>, ::error::Error> {
+		PowRebuilder::new(chain, db, manifest).map(|r| Box::new(r) as Box<_>)
+	}
+}
+
+/// Used to build block chunks.
+struct PowWorker<'a> {
+	chain: &'a BlockChain,
+	// block, receipt rlp pairs.
+	rlps: VecDeque<Bytes>,
+	current_hash: H256,
+	writer: &'a mut ChunkSink<'a>,
+	preferred_size: usize,
+}
+
+impl<'a> PowWorker<'a> {
+	// Repeatedly fill the buffers and writes out chunks, moving backwards from starting block hash.
+	// Loops until we reach the first desired block, and writes out the remainder.
+	fn chunk_all(&mut self) -> Result<(), Error> {
+		let mut loaded_size = 0;
+		let mut last = self.current_hash;
+
+		let genesis_hash = self.chain.genesis_hash();
+
+		for _ in 0..SNAPSHOT_BLOCKS {
+			if self.current_hash == genesis_hash { break }
+
+			let (block, receipts) = self.chain.block(&self.current_hash)
+				.and_then(|b| self.chain.block_receipts(&self.current_hash).map(|r| (b, r)))
+				.ok_or(Error::BlockNotFound(self.current_hash))?;
+
+			let abridged_rlp = AbridgedBlock::from_block_view(&block.view()).into_inner();
+
+			let pair = {
+				let mut pair_stream = RlpStream::new_list(2);
+				pair_stream.append_raw(&abridged_rlp, 1).append(&receipts);
+				pair_stream.out()
+			};
+
+			let new_loaded_size = loaded_size + pair.len();
+
+			// cut off the chunk if too large.
+
+			if new_loaded_size > self.preferred_size && !self.rlps.is_empty() {
+				self.write_chunk(last)?;
+				loaded_size = pair.len();
+			} else {
+				loaded_size = new_loaded_size;
+			}
+
+			self.rlps.push_front(pair);
+
+			last = self.current_hash;
+			self.current_hash = block.header_view().parent_hash();
+		}
+
+		if loaded_size != 0 {
+			self.write_chunk(last)?;
+		}
+
+		Ok(())
+	}
+
+	// write out the data in the buffers to a chunk on disk
+	//
+	// we preface each chunk with the parent of the first block's details,
+	// obtained from the details of the last block written.
+	fn write_chunk(&mut self, last: H256) -> Result<(), Error> {
+		trace!(target: "snapshot", "prepared block chunk with {} blocks", self.rlps.len());
+
+		let (last_header, last_details) = self.chain.block_header(&last)
+			.and_then(|n| self.chain.block_details(&last).map(|d| (n, d)))
+			.ok_or(Error::BlockNotFound(last))?;
+
+		let parent_number = last_header.number() - 1;
+		let parent_hash = last_header.parent_hash();
+		let parent_total_difficulty = last_details.total_difficulty - *last_header.difficulty();
+
+		trace!(target: "snapshot", "parent last written block: {}", parent_hash);
+
+		let num_entries = self.rlps.len();
+		let mut rlp_stream = RlpStream::new_list(3 + num_entries);
+		rlp_stream.append(&parent_number).append(parent_hash).append(&parent_total_difficulty);
+
+		for pair in self.rlps.drain(..) {
+			rlp_stream.append_raw(&pair, 1);
+		}
+
+		let raw_data = rlp_stream.out();
+
+		(self.writer)(&raw_data)?;
+
+		Ok(())
+	}
+}
+
+/// Rebuilder for proof-of-work chains.
+/// Does basic verification for all blocks, but `PoW` verification for some.
+/// Blocks must be fed in-order.
+///
+/// The first block in every chunk is disconnected from the last block in the
+/// chunk before it, as chunks may be submitted out-of-order.
+///
+/// After all chunks have been submitted, we "glue" the chunks together.
+pub struct PowRebuilder {
+	chain: BlockChain,
+	db: Arc<KeyValueDB>,
+	rng: OsRng,
+	disconnected: Vec<(u64, H256)>,
+	best_number: u64,
+	best_hash: H256,
+	best_root: H256,
+	fed_blocks: u64,
+}
+
+impl PowRebuilder {
+	/// Create a new PowRebuilder.
+	fn new(chain: BlockChain, db: Arc<KeyValueDB>, manifest: &ManifestData) -> Result<Self, ::error::Error> {
+		Ok(PowRebuilder {
+			chain: chain,
+			db: db,
+			rng: OsRng::new()?,
+			disconnected: Vec::new(),
+			best_number: manifest.block_number,
+			best_hash: manifest.block_hash,
+			best_root: manifest.state_root,
+			fed_blocks: 0,
+		})
+	}
+}
+
+impl Rebuilder for PowRebuilder {
+	/// Feed the rebuilder an uncompressed block chunk.
+	/// Returns the number of blocks fed or any errors.
+	fn feed(&mut self, chunk: &[u8], engine: &Engine, abort_flag: &AtomicBool) -> Result<(), ::error::Error> {
+		use basic_types::Seal::With;
+		use views::BlockView;
+		use snapshot::verify_old_block;
+		use util::U256;
+		use util::triehash::ordered_trie_root;
+
+		let rlp = UntrustedRlp::new(chunk);
+		let item_count = rlp.item_count()?;
+		let num_blocks = (item_count - 3) as u64;
+
+		trace!(target: "snapshot", "restoring block chunk with {} blocks.", item_count - 3);
+
+		if self.fed_blocks + num_blocks > SNAPSHOT_BLOCKS {
+			return Err(Error::TooManyBlocks(SNAPSHOT_BLOCKS, self.fed_blocks).into())
+		}
+
+		// todo: assert here that these values are consistent with chunks being in order.
+		let mut cur_number = rlp.val_at::<u64>(0)? + 1;
+		let mut parent_hash = rlp.val_at::<H256>(1)?;
+		let parent_total_difficulty = rlp.val_at::<U256>(2)?;
+
+		for idx in 3..item_count {
+			if !abort_flag.load(Ordering::SeqCst) { return Err(Error::RestorationAborted.into()) }
+
+			let pair = rlp.at(idx)?;
+			let abridged_rlp = pair.at(0)?.as_raw().to_owned();
+			let abridged_block = AbridgedBlock::from_raw(abridged_rlp);
+			let receipts: Vec<::receipt::Receipt> = pair.list_at(1)?;
+			let receipts_root = ordered_trie_root(
+				pair.at(1)?.iter().map(|r| r.as_raw().to_owned())
+			);
+
+			let block = abridged_block.to_block(parent_hash, cur_number, receipts_root)?;
+			let block_bytes = block.rlp_bytes(With);
+			let is_best = cur_number == self.best_number;
+
+			if is_best {
+				if block.header.hash() != self.best_hash {
+					return Err(Error::WrongBlockHash(cur_number, self.best_hash, block.header.hash()).into())
+				}
+
+				if block.header.state_root() != &self.best_root {
+					return Err(Error::WrongStateRoot(self.best_root, *block.header.state_root()).into())
+				}
+			}
+
+			verify_old_block(
+				&mut self.rng,
+				&block.header,
+				engine,
+				&self.chain,
+				Some(&block_bytes),
+				is_best
+			)?;
+
+			let mut batch = self.db.transaction();
+
+			// special-case the first block in each chunk.
+			if idx == 3 {
+				if self.chain.insert_unordered_block(&mut batch, &block_bytes, receipts, Some(parent_total_difficulty), is_best, false) {
+					self.disconnected.push((cur_number, block.header.hash()));
+				}
+			} else {
+				self.chain.insert_unordered_block(&mut batch, &block_bytes, receipts, None, is_best, false);
+			}
+			self.db.write_buffered(batch);
+			self.chain.commit();
+
+			parent_hash = BlockView::new(&block_bytes).hash();
+			cur_number += 1;
+		}
+
+		self.fed_blocks += num_blocks;
+
+		Ok(())
+	}
+
+	/// Glue together any disconnected chunks and check that the chain is complete.
+	fn finalize(&mut self) -> Result<(), Error> {
+		let mut batch = self.db.transaction();
+
+		for (first_num, first_hash) in self.disconnected.drain(..) {
+			let parent_num = first_num - 1;
+
+			// check if the parent is even in the chain.
+			// since we don't restore every single block in the chain,
+			// the first block of the first chunks has nothing to connect to.
+			if let Some(parent_hash) = self.chain.block_hash(parent_num) {
+				// if so, add the child to it.
+				self.chain.add_child(&mut batch, parent_hash, first_hash);
+			}
+		}
+		self.db.write_buffered(batch);
+		Ok(())
+	}
+}

ethcore/src/snapshot/error.rs

@@ -57,6 +57,8 @@ pub enum Error {
 	VersionNotSupported(u64),
 	/// Max chunk size is to small to fit basic account data.
 	ChunkTooSmall,
+	/// Snapshots not supported by the consensus engine.
+	SnapshotsUnsupported,
 }
 
 impl fmt::Display for Error {
@@ -79,6 +81,7 @@ impl fmt::Display for Error {
 			Error::Trie(ref err) => err.fmt(f),
 			Error::VersionNotSupported(ref ver) => write!(f, "Snapshot version {} is not supprted.", ver),
 			Error::ChunkTooSmall => write!(f, "Chunk size is too small."),
+			Error::SnapshotsUnsupported => write!(f, "Snapshots unsupported by consensus engine."),
 		}
 	}
 }

ethcore/src/snapshot/mod.rs

@@ -17,9 +17,9 @@
 //! Snapshot creation, restoration, and network service.
 //!
 //! Documentation of the format can be found at
-//! https://github.com/paritytech/parity/wiki/%22PV64%22-Snapshot-Format
+//! https://github.com/paritytech/parity/wiki/Warp-Sync-Snapshot-Format
 
-use std::collections::{HashMap, HashSet, VecDeque};
+use std::collections::{HashMap, HashSet};
 use std::sync::Arc;
 use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
 
@@ -28,7 +28,6 @@ use blockchain::{BlockChain, BlockProvider};
 use engines::Engine;
 use header::Header;
 use ids::BlockId;
-use views::BlockView;
 
 use util::{Bytes, Hashable, HashDB, DBValue, snappy, U256, Uint};
 use util::Mutex;
@@ -40,7 +39,6 @@ use util::sha3::SHA3_NULL_RLP;
 use rlp::{RlpStream, UntrustedRlp};
 use bloom_journal::Bloom;
 
-use self::block::AbridgedBlock;
 use self::io::SnapshotWriter;
 
 use super::state_db::StateDB;
@@ -51,6 +49,7 @@ use rand::{Rng, OsRng};
 
 pub use self::error::Error;
 
+pub use self::consensus::*;
 pub use self::service::{Service, DatabaseRestore};
 pub use self::traits::SnapshotService;
 pub use self::watcher::Watcher;
@@ -63,6 +62,7 @@ pub mod service;
 
 mod account;
 mod block;
+mod consensus;
 mod error;
 mod watcher;
 
@@ -83,9 +83,6 @@ mod traits {
 // Try to have chunks be around 4MB (before compression)
 const PREFERRED_CHUNK_SIZE: usize = 4 * 1024 * 1024;
 
-// How many blocks to include in a snapshot, starting from the head of the chain.
-const SNAPSHOT_BLOCKS: u64 = 30000;
-
 /// A progress indicator for snapshots.
 #[derive(Debug, Default)]
 pub struct Progress {
@@ -122,6 +119,7 @@ impl Progress {
 }
 /// Take a snapshot using the given blockchain, starting block hash, and database, writing into the given writer.
 pub fn take_snapshot<W: SnapshotWriter + Send>(
+	engine: &Engine,
 	chain: &BlockChain,
 	block_at: H256,
 	state_db: &HashDB,
@@ -136,9 +134,11 @@ pub fn take_snapshot<W: SnapshotWriter + Send>(
 	info!("Taking snapshot starting at block {}", number);
 
 	let writer = Mutex::new(writer);
+	let chunker = engine.snapshot_components().ok_or(Error::SnapshotsUnsupported)?;
 	let (state_hashes, block_hashes) = scope(|scope| {
-		let block_guard = scope.spawn(|| chunk_blocks(chain, block_at, &writer, p));
-		let state_res = chunk_state(state_db, state_root, &writer, p);
+		let writer = &writer;
+		let block_guard = scope.spawn(move || chunk_secondary(chunker, chain, block_at, writer, p));
+		let state_res = chunk_state(state_db, state_root, writer, p);
 
 		state_res.and_then(|state_hashes| {
 			block_guard.join().map(|block_hashes| (state_hashes, block_hashes))
@@ -163,128 +163,41 @@ pub fn take_snapshot<W: SnapshotWriter + Send>(
 	Ok(())
 }
 
-/// Used to build block chunks.
-struct BlockChunker<'a> {
-	chain: &'a BlockChain,
-	// block, receipt rlp pairs.
-	rlps: VecDeque<Bytes>,
-	current_hash: H256,
-	hashes: Vec<H256>,
-	snappy_buffer: Vec<u8>,
-	writer: &'a Mutex<SnapshotWriter + 'a>,
-	progress: &'a Progress,
-}
-
-impl<'a> BlockChunker<'a> {
-	// Repeatedly fill the buffers and writes out chunks, moving backwards from starting block hash.
-	// Loops until we reach the first desired block, and writes out the remainder.
-	fn chunk_all(&mut self) -> Result<(), Error> {
-		let mut loaded_size = 0;
-		let mut last = self.current_hash;
-
-		let genesis_hash = self.chain.genesis_hash();
-
-		for _ in 0..SNAPSHOT_BLOCKS {
-			if self.current_hash == genesis_hash { break }
-
-			let (block, receipts) = self.chain.block(&self.current_hash)
-				.and_then(|b| self.chain.block_receipts(&self.current_hash).map(|r| (b, r)))
-				.ok_or(Error::BlockNotFound(self.current_hash))?;
-
-			let abridged_rlp = AbridgedBlock::from_block_view(&block.view()).into_inner();
-
-			let pair = {
-				let mut pair_stream = RlpStream::new_list(2);
-				pair_stream.append_raw(&abridged_rlp, 1).append(&receipts);
-				pair_stream.out()
-			};
-
-			let new_loaded_size = loaded_size + pair.len();
-
-			// cut off the chunk if too large.
-
-			if new_loaded_size > PREFERRED_CHUNK_SIZE && !self.rlps.is_empty() {
-				self.write_chunk(last)?;
-				loaded_size = pair.len();
-			} else {
-				loaded_size = new_loaded_size;
-			}
-
-			self.rlps.push_front(pair);
-
-			last = self.current_hash;
-			self.current_hash = block.header_view().parent_hash();
-		}
-
-		if loaded_size != 0 {
-			self.write_chunk(last)?;
-		}
-
-		Ok(())
-	}
-
-	// write out the data in the buffers to a chunk on disk
-	//
-	// we preface each chunk with the parent of the first block's details,
-	// obtained from the details of the last block written.
-	fn write_chunk(&mut self, last: H256) -> Result<(), Error> {
-		trace!(target: "snapshot", "prepared block chunk with {} blocks", self.rlps.len());
-
-		let (last_header, last_details) = self.chain.block_header(&last)
-			.and_then(|n| self.chain.block_details(&last).map(|d| (n, d)))
-			.ok_or(Error::BlockNotFound(last))?;
-
-		let parent_number = last_header.number() - 1;
-		let parent_hash = last_header.parent_hash();
-		let parent_total_difficulty = last_details.total_difficulty - *last_header.difficulty();
-
-		trace!(target: "snapshot", "parent last written block: {}", parent_hash);
-
-		let num_entries = self.rlps.len();
-		let mut rlp_stream = RlpStream::new_list(3 + num_entries);
-		rlp_stream.append(&parent_number).append(parent_hash).append(&parent_total_difficulty);
-
-		for pair in self.rlps.drain(..) {
-			rlp_stream.append_raw(&pair, 1);
-		}
-
-		let raw_data = rlp_stream.out();
-
-		let size = snappy::compress_into(&raw_data, &mut self.snappy_buffer);
-		let compressed = &self.snappy_buffer[..size];
-		let hash = compressed.sha3();
-
-		self.writer.lock().write_block_chunk(hash, compressed)?;
-		trace!(target: "snapshot", "wrote block chunk. hash: {}, size: {}, uncompressed size: {}", hash.hex(), size, raw_data.len());
-
-		self.progress.size.fetch_add(size, Ordering::SeqCst);
-		self.progress.blocks.fetch_add(num_entries, Ordering::SeqCst);
-
-		self.hashes.push(hash);
-		Ok(())
-	}
-}
-
-/// Create and write out all block chunks to disk, returning a vector of all
-/// the hashes of block chunks created.
+/// Create and write out all secondary chunks to disk, returning a vector of all
+/// the hashes of secondary chunks created.
 ///
-/// The path parameter is the directory to store the block chunks in.
-/// This function assumes the directory exists already.
+/// Secondary chunks are engine-specific, but they intend to corroborate the state data
+/// in the state chunks.
 /// Returns a list of chunk hashes, with the first having the blocks furthest from the genesis.
-pub fn chunk_blocks<'a>(chain: &'a BlockChain, start_hash: H256, writer: &Mutex<SnapshotWriter + 'a>, progress: &'a Progress) -> Result<Vec<H256>, Error> {
-	let mut chunker = BlockChunker {
-		chain: chain,
-		rlps: VecDeque::new(),
-		current_hash: start_hash,
-		hashes: Vec::new(),
-		snappy_buffer: vec![0; snappy::max_compressed_len(PREFERRED_CHUNK_SIZE)],
-		writer: writer,
-		progress: progress,
+pub fn chunk_secondary<'a>(mut chunker: Box<SnapshotComponents>, chain: &'a BlockChain, start_hash: H256, writer: &Mutex<SnapshotWriter + 'a>, progress: &'a Progress) -> Result<Vec<H256>, Error> {
+	let mut chunk_hashes = Vec::new();
+	let mut snappy_buffer = vec![0; snappy::max_compressed_len(PREFERRED_CHUNK_SIZE)];
+
+	{
+		let mut chunk_sink = |raw_data: &[u8]| {
+			let compressed_size = snappy::compress_into(raw_data, &mut snappy_buffer);
+			let compressed = &snappy_buffer[..compressed_size];
+			let hash = compressed.sha3();
+			let size = compressed.len();
+
+			writer.lock().write_block_chunk(hash, compressed)?;
+			trace!(target: "snapshot", "wrote secondary chunk. hash: {}, size: {}, uncompressed size: {}",
+				hash.hex(), size, raw_data.len());
+
+			progress.size.fetch_add(size, Ordering::SeqCst);
+			chunk_hashes.push(hash);
+			Ok(())
 		};
 
-	chunker.chunk_all()?;
+		chunker.chunk_all(
+			chain,
+			start_hash,
+			&mut chunk_sink,
+			PREFERRED_CHUNK_SIZE,
+		)?;
+	}
 
-	Ok(chunker.hashes)
+	Ok(chunk_hashes)
 }
 
 /// State trie chunker.
@@ -564,158 +477,15 @@ const POW_VERIFY_RATE: f32 = 0.02;
 /// the fullest verification possible. If not, it will take a random sample to determine whether it will
 /// do heavy or light verification.
 pub fn verify_old_block(rng: &mut OsRng, header: &Header, engine: &Engine, chain: &BlockChain, body: Option<&[u8]>, always: bool) -> Result<(), ::error::Error> {
+	engine.verify_block_basic(header, body)?;
+
 	if always || rng.gen::<f32>() <= POW_VERIFY_RATE {
+		engine.verify_block_unordered(header, body)?;
 		match chain.block_header(header.parent_hash()) {
 			Some(parent) => engine.verify_block_family(header, &parent, body),
-			None => engine.verify_block_seal(header), // TODO: fetch validation proof as necessary.
+			None => Ok(()),
 		}
 	} else {
-		engine.verify_block_basic(header, body)
-	}
-}
-
-/// Rebuilds the blockchain from chunks.
-///
-/// Does basic verification for all blocks, but `PoW` verification for some.
-/// Blocks must be fed in-order.
-///
-/// The first block in every chunk is disconnected from the last block in the
-/// chunk before it, as chunks may be submitted out-of-order.
-///
-/// After all chunks have been submitted, we "glue" the chunks together.
-pub struct BlockRebuilder {
-	chain: BlockChain,
-	db: Arc<Database>,
-	rng: OsRng,
-	disconnected: Vec<(u64, H256)>,
-	best_number: u64,
-	best_hash: H256,
-	best_root: H256,
-	fed_blocks: u64,
-}
-
-impl BlockRebuilder {
-	/// Create a new BlockRebuilder.
-	pub fn new(chain: BlockChain, db: Arc<Database>, manifest: &ManifestData) -> Result<Self, ::error::Error> {
-		Ok(BlockRebuilder {
-			chain: chain,
-			db: db,
-			rng: OsRng::new()?,
-			disconnected: Vec::new(),
-			best_number: manifest.block_number,
-			best_hash: manifest.block_hash,
-			best_root: manifest.state_root,
-			fed_blocks: 0,
-		})
-	}
-
-	/// Feed the rebuilder an uncompressed block chunk.
-	/// Returns the number of blocks fed or any errors.
-	pub fn feed(&mut self, chunk: &[u8], engine: &Engine, abort_flag: &AtomicBool) -> Result<u64, ::error::Error> {
-		use basic_types::Seal::With;
-		use util::U256;
-		use util::triehash::ordered_trie_root;
-
-		let rlp = UntrustedRlp::new(chunk);
-		let item_count = rlp.item_count()?;
-		let num_blocks = (item_count - 3) as u64;
-
-		trace!(target: "snapshot", "restoring block chunk with {} blocks.", item_count - 3);
-
-		if self.fed_blocks + num_blocks > SNAPSHOT_BLOCKS {
-			return Err(Error::TooManyBlocks(SNAPSHOT_BLOCKS, self.fed_blocks).into())
-		}
-
-		// todo: assert here that these values are consistent with chunks being in order.
-		let mut cur_number = rlp.val_at::<u64>(0)? + 1;
-		let mut parent_hash = rlp.val_at::<H256>(1)?;
-		let parent_total_difficulty = rlp.val_at::<U256>(2)?;
-
-		for idx in 3..item_count {
-			if !abort_flag.load(Ordering::SeqCst) { return Err(Error::RestorationAborted.into()) }
-
-			let pair = rlp.at(idx)?;
-			let abridged_rlp = pair.at(0)?.as_raw().to_owned();
-			let abridged_block = AbridgedBlock::from_raw(abridged_rlp);
-			let receipts: Vec<::receipt::Receipt> = pair.list_at(1)?;
-			let receipts_root = ordered_trie_root(
-				pair.at(1)?.iter().map(|r| r.as_raw().to_owned())
-			);
-
-			let block = abridged_block.to_block(parent_hash, cur_number, receipts_root)?;
-			let block_bytes = block.rlp_bytes(With);
-			let is_best = cur_number == self.best_number;
-
-			if is_best {
-				if block.header.hash() != self.best_hash {
-					return Err(Error::WrongBlockHash(cur_number, self.best_hash, block.header.hash()).into())
-				}
-
-				if block.header.state_root() != &self.best_root {
-					return Err(Error::WrongStateRoot(self.best_root, *block.header.state_root()).into())
-				}
-			}
-
-			verify_old_block(
-				&mut self.rng,
-				&block.header,
-				engine,
-				&self.chain,
-				Some(&block_bytes),
-				is_best
-			)?;
-
-			let mut batch = self.db.transaction();
-
-			// special-case the first block in each chunk.
-			if idx == 3 {
-				if self.chain.insert_unordered_block(&mut batch, &block_bytes, receipts, Some(parent_total_difficulty), is_best, false) {
-					self.disconnected.push((cur_number, block.header.hash()));
-				}
-			} else {
-				self.chain.insert_unordered_block(&mut batch, &block_bytes, receipts, None, is_best, false);
-			}
-			self.db.write_buffered(batch);
-			self.chain.commit();
-
-			parent_hash = BlockView::new(&block_bytes).hash();
-			cur_number += 1;
-		}
-
-		self.fed_blocks += num_blocks;
-
-		Ok(num_blocks)
-	}
-
-	/// Glue together any disconnected chunks and check that the chain is complete.
-	pub fn finalize(self, canonical: HashMap<u64, H256>) -> Result<(), Error> {
-		let mut batch = self.db.transaction();
-
-		for (first_num, first_hash) in self.disconnected {
-			let parent_num = first_num - 1;
-
-			// check if the parent is even in the chain.
-			// since we don't restore every single block in the chain,
-			// the first block of the first chunks has nothing to connect to.
-			if let Some(parent_hash) = self.chain.block_hash(parent_num) {
-				// if so, add the child to it.
-				self.chain.add_child(&mut batch, parent_hash, first_hash);
-			}
-		}
-		self.db.write_buffered(batch);
-
-		let best_number = self.best_number;
-		for num in (0..self.fed_blocks).map(|x| best_number - x) {
-
-			let hash = self.chain.block_hash(num).ok_or(Error::IncompleteChain)?;
-
-			if let Some(canon_hash) = canonical.get(&num).cloned() {
-				if canon_hash != hash {
-					return Err(Error::WrongBlockHash(num, canon_hash, hash));
-				}
-			}
-		}
-
 		Ok(())
 	}
 }

ethcore/src/snapshot/service.rs

@@ -16,14 +16,14 @@
 
 //! Snapshot network service implementation.
 
-use std::collections::{HashMap, HashSet};
+use std::collections::HashSet;
 use std::io::ErrorKind;
 use std::fs;
 use std::path::PathBuf;
 use std::sync::Arc;
 use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
 
-use super::{ManifestData, StateRebuilder, BlockRebuilder, RestorationStatus, SnapshotService};
+use super::{ManifestData, StateRebuilder, Rebuilder, RestorationStatus, SnapshotService};
 use super::io::{SnapshotReader, LooseReader, SnapshotWriter, LooseWriter};
 
 use blockchain::BlockChain;
@@ -69,12 +69,11 @@ struct Restoration {
 	state_chunks_left: HashSet<H256>,
 	block_chunks_left: HashSet<H256>,
 	state: StateRebuilder,
-	blocks: BlockRebuilder,
+	secondary: Box<Rebuilder>,
 	writer: Option<LooseWriter>,
 	snappy_buffer: Bytes,
 	final_state_root: H256,
 	guard: Guard,
-	canonical_hashes: HashMap<u64, H256>,
 	db: Arc<Database>,
 }
 
@@ -86,6 +85,7 @@ struct RestorationParams<'a> {
 	writer: Option<LooseWriter>, // writer for recovered snapshot.
 	genesis: &'a [u8], // genesis block of the chain.
 	guard: Guard, // guard for the restoration directory.
+	engine: &'a Engine,
 }
 
 impl Restoration {
@@ -100,7 +100,10 @@ impl Restoration {
 			.map_err(UtilError::SimpleString)?);
 
 		let chain = BlockChain::new(Default::default(), params.genesis, raw_db.clone());
-		let blocks = BlockRebuilder::new(chain, raw_db.clone(), &manifest)?;
+		let components = params.engine.snapshot_components()
+			.ok_or_else(|| ::snapshot::Error::SnapshotsUnsupported)?;
+
+		let secondary = components.rebuilder(chain, raw_db.clone(), &manifest)?;
 
 		let root = manifest.state_root.clone();
 		Ok(Restoration {
@@ -108,12 +111,11 @@ impl Restoration {
 			state_chunks_left: state_chunks,
 			block_chunks_left: block_chunks,
 			state: StateRebuilder::new(raw_db.clone(), params.pruning),
-			blocks: blocks,
+			secondary: secondary,
 			writer: params.writer,
 			snappy_buffer: Vec::new(),
 			final_state_root: root,
 			guard: params.guard,
-			canonical_hashes: HashMap::new(),
 			db: raw_db,
 		})
 	}
@@ -138,7 +140,7 @@ impl Restoration {
 		if self.block_chunks_left.remove(&hash) {
 			let len = snappy::decompress_into(chunk, &mut self.snappy_buffer)?;
 
-			self.blocks.feed(&self.snappy_buffer[..len], engine, flag)?;
+			self.secondary.feed(&self.snappy_buffer[..len], engine, flag)?;
 			if let Some(ref mut writer) = self.writer.as_mut() {
 				 writer.write_block_chunk(hash, chunk)?;
 			}
@@ -147,13 +149,8 @@ impl Restoration {
 		Ok(())
 	}
 
-	// note canonical hashes.
-	fn note_canonical(&mut self, hashes: &[(u64, H256)]) {
-		self.canonical_hashes.extend(hashes.iter().cloned());
-	}
-
 	// finish up restoration.
-	fn finalize(self) -> Result<(), Error> {
+	fn finalize(mut self) -> Result<(), Error> {
 		use util::trie::TrieError;
 
 		if !self.is_done() { return Ok(()) }
@@ -169,7 +166,7 @@ impl Restoration {
 		self.state.finalize(self.manifest.block_number, self.manifest.block_hash)?;
 
 		// connect out-of-order chunks and verify chain integrity.
-		self.blocks.finalize(self.canonical_hashes)?;
+		self.secondary.finalize()?;
 
 		if let Some(writer) = self.writer {
 			writer.finish(self.manifest)?;
@@ -425,6 +422,7 @@ impl Service {
 			writer: writer,
 			genesis: &self.genesis_block,
 			guard: Guard::new(rest_dir),
+			engine: &*self.engine,
 		};
 
 		let state_chunks = params.manifest.state_hashes.len();
@@ -593,14 +591,6 @@ impl SnapshotService for Service {
 			trace!("Error sending snapshot service message: {:?}", e);
 		}
 	}
-
-	fn provide_canon_hashes(&self, canonical: &[(u64, H256)]) {
-		let mut rest = self.restoration.lock();
-
-		if let Some(ref mut rest) = rest.as_mut() {
-			rest.note_canonical(canonical);
-		}
-	}
 }
 
 impl Drop for Service {

ethcore/src/snapshot/snapshot_service_trait.rs

@@ -48,10 +48,6 @@ pub trait SnapshotService : Sync + Send {
 	/// Feed a raw block chunk to the service to be processed asynchronously.
 	/// no-op if currently restoring.
 	fn restore_block_chunk(&self, hash: H256, chunk: Bytes);
-
-	/// Give the restoration in-progress some canonical block hashes for
-	/// extra verification (performed at the end)
-	fn provide_canon_hashes(&self, canonical: &[(u64, H256)]);
 }
 
 impl IpcConfig for SnapshotService { }

ethcore/src/snapshot/tests/blocks.rs

@@ -21,13 +21,12 @@ use error::Error;
 
 use blockchain::generator::{ChainGenerator, ChainIterator, BlockFinalizer};
 use blockchain::BlockChain;
-use snapshot::{chunk_blocks, BlockRebuilder, Error as SnapshotError, Progress};
+use snapshot::{chunk_secondary, Error as SnapshotError, Progress, SnapshotComponents};
 use snapshot::io::{PackedReader, PackedWriter, SnapshotReader, SnapshotWriter};
 
 use util::{Mutex, snappy};
-use util::kvdb::{Database, DatabaseConfig};
+use util::kvdb::{self, KeyValueDB, DBTransaction};
 
-use std::collections::HashMap;
 use std::sync::Arc;
 use std::sync::atomic::AtomicBool;
 
@@ -35,19 +34,18 @@ fn chunk_and_restore(amount: u64) {
 	let mut canon_chain = ChainGenerator::default();
 	let mut finalizer = BlockFinalizer::default();
 	let genesis = canon_chain.generate(&mut finalizer).unwrap();
-	let db_cfg = DatabaseConfig::with_columns(::db::NUM_COLUMNS);
+	let components = ::snapshot::PowSnapshot;
 
 	let engine = Arc::new(::engines::NullEngine::default());
-	let orig_path = RandomTempPath::create_dir();
 	let new_path = RandomTempPath::create_dir();
 	let mut snapshot_path = new_path.as_path().to_owned();
 	snapshot_path.push("SNAP");
 
-	let old_db = Arc::new(Database::open(&db_cfg, orig_path.as_str()).unwrap());
+	let old_db = Arc::new(kvdb::in_memory(::db::NUM_COLUMNS.unwrap_or(0)));
 	let bc = BlockChain::new(Default::default(), &genesis, old_db.clone());
 
 	// build the blockchain.
-	let mut batch = old_db.transaction();
+	let mut batch = DBTransaction::new();
 	for _ in 0..amount {
 		let block = canon_chain.generate(&mut finalizer).unwrap();
 		bc.insert_block(&mut batch, &block, vec![]);
@@ -56,12 +54,18 @@ fn chunk_and_restore(amount: u64) {
 
 	old_db.write(batch).unwrap();
 
-
 	let best_hash = bc.best_block_hash();
 
 	// snapshot it.
 	let writer = Mutex::new(PackedWriter::new(&snapshot_path).unwrap());
-	let block_hashes = chunk_blocks(&bc, best_hash, &writer, &Progress::default()).unwrap();
+	let block_hashes = chunk_secondary(
+		Box::new(::snapshot::PowSnapshot),
+		&bc,
+		best_hash,
+		&writer,
+		&Progress::default()
+	).unwrap();
+
 	let manifest = ::snapshot::ManifestData {
 		version: 2,
 		state_hashes: Vec::new(),
@@ -74,9 +78,10 @@ fn chunk_and_restore(amount: u64) {
 	writer.into_inner().finish(manifest.clone()).unwrap();
 
 	// restore it.
-	let new_db = Arc::new(Database::open(&db_cfg, new_path.as_str()).unwrap());
+	let new_db = Arc::new(kvdb::in_memory(::db::NUM_COLUMNS.unwrap_or(0)));
 	let new_chain = BlockChain::new(Default::default(), &genesis, new_db.clone());
-	let mut rebuilder = BlockRebuilder::new(new_chain, new_db.clone(), &manifest).unwrap();
+	let mut rebuilder = components.rebuilder(new_chain, new_db.clone(), &manifest).unwrap();
+
 	let reader = PackedReader::new(&snapshot_path).unwrap().unwrap();
 	let flag = AtomicBool::new(true);
 	for chunk_hash in &reader.manifest().block_hashes {
@@ -85,7 +90,8 @@ fn chunk_and_restore(amount: u64) {
 		rebuilder.feed(&chunk, engine.as_ref(), &flag).unwrap();
 	}
 
-	rebuilder.finalize(HashMap::new()).unwrap();
+	rebuilder.finalize().unwrap();
+	drop(rebuilder);
 
 	// and test it.
 	let new_chain = BlockChain::new(Default::default(), &genesis, new_db);
@@ -118,10 +124,8 @@ fn checks_flag() {
 	};
 
 	let chunk = stream.out();
-	let path = RandomTempPath::create_dir();
 
-	let db_cfg = DatabaseConfig::with_columns(::db::NUM_COLUMNS);
-	let db = Arc::new(Database::open(&db_cfg, path.as_str()).unwrap());
+	let db = Arc::new(kvdb::in_memory(::db::NUM_COLUMNS.unwrap_or(0)));
 	let engine = Arc::new(::engines::NullEngine::default());
 	let chain = BlockChain::new(Default::default(), &genesis, db.clone());
 
@@ -134,7 +138,7 @@ fn checks_flag() {
 		block_hash: H256::default(),
 	};
 
-	let mut rebuilder = BlockRebuilder::new(chain, db.clone(), &manifest).unwrap();
+	let mut rebuilder = ::snapshot::PowSnapshot.rebuilder(chain, db.clone(), &manifest).unwrap();
 
 	match rebuilder.feed(&chunk, engine.as_ref(), &AtomicBool::new(false)) {
 		Err(Error::Snapshot(SnapshotError::RestorationAborted)) => {}

rpc/src/v1/tests/helpers/snapshot_service.rs

@@ -47,5 +47,4 @@ impl SnapshotService for TestSnapshotService {
 	fn abort_restore(&self) { }
 	fn restore_state_chunk(&self, _hash: H256, _chunk: Bytes) { }
 	fn restore_block_chunk(&self, _hash: H256, _chunk: Bytes) { }
-	fn provide_canon_hashes(&self, _hashes: &[(u64, H256)]) { }
 }

sync/src/tests/snapshot.rs

@@ -24,7 +24,6 @@ use SyncConfig;
 pub struct TestSnapshotService {
 	manifest: Option<ManifestData>,
 	chunks: HashMap<H256, Bytes>,
-	canon_hashes: Mutex<HashMap<u64, H256>>,
 
 	restoration_manifest: Mutex<Option<ManifestData>>,
 	state_restoration_chunks: Mutex<HashMap<H256, Bytes>>,
@@ -36,7 +35,6 @@ impl TestSnapshotService {
 		TestSnapshotService {
 			manifest: None,
 			chunks: HashMap::new(),
-			canon_hashes: Mutex::new(HashMap::new()),
 			restoration_manifest: Mutex::new(None),
 			state_restoration_chunks: Mutex::new(HashMap::new()),
 			block_restoration_chunks: Mutex::new(HashMap::new()),
@@ -61,7 +59,6 @@ impl TestSnapshotService {
 		TestSnapshotService {
 			manifest: Some(manifest),
 			chunks: chunks,
-			canon_hashes: Mutex::new(HashMap::new()),
 			restoration_manifest: Mutex::new(None),
 			state_restoration_chunks: Mutex::new(HashMap::new()),
 			block_restoration_chunks: Mutex::new(HashMap::new()),
@@ -115,10 +112,6 @@ impl SnapshotService for TestSnapshotService {
 			self.block_restoration_chunks.lock().insert(hash, chunk);
 		}
 	}
-
-	fn provide_canon_hashes(&self, hashes: &[(u64, H256)]) {
-		self.canon_hashes.lock().extend(hashes.iter().cloned());
-	}
 }
 
 #[test]