Merge pull request #5002 from paritytech/lightcli

Quick'n'dirty CLI for the light client

Cargo.lock

@@ -27,6 +27,7 @@ dependencies = [
  "ethsync 1.7.0",
  "evmbin 0.1.0",
  "fdlimit 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "futures 0.1.11 (registry+https://github.com/rust-lang/crates.io-index)",
  "isatty 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "jsonrpc-core 7.0.0 (git+https://github.com/paritytech/jsonrpc.git?branch=parity-1.7)",
  "log 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -533,6 +534,7 @@ name = "ethcore-light"
 version = "1.7.0"
 dependencies = [
  "ethcore 1.7.0",
+ "ethcore-devtools 1.7.0",
  "ethcore-io 1.7.0",
  "ethcore-ipc 1.7.0",
  "ethcore-ipc-codegen 1.7.0",

Cargo.toml

@@ -23,6 +23,7 @@ toml = "0.2"
 serde = "0.9"
 serde_json = "0.9"
 app_dirs = "1.1.1"
+futures = "0.1"
 fdlimit = "0.1"
 ws2_32-sys = "0.2"
 ctrlc = { git = "https://github.com/paritytech/rust-ctrlc.git" }

ethcore/light/Cargo.toml

@@ -17,6 +17,7 @@ ethcore-util = { path = "../../util" }
 ethcore-network = { path = "../../util/network" }
 ethcore-io = { path = "../../util/io" }
 ethcore-ipc = { path = "../../ipc/rpc", optional = true }
+ethcore-devtools = { path = "../../devtools" }
 rlp = { path = "../../util/rlp" }
 time = "0.1"
 smallvec = "0.3.1"

ethcore/light/src/client/header_chain.rs

@@ -23,9 +23,9 @@
 //! This is separate from the `BlockChain` for two reasons:
 //!   - It stores only headers (and a pruned subset of them)
 //!   - To allow for flexibility in the database layout once that's incorporated.
-// TODO: use DB instead of memory. DB Layout: just the contents of `candidates`/`headers`
 
-use std::collections::{BTreeMap, HashMap};
+use std::collections::BTreeMap;
+use std::sync::Arc;
 
 use cht;
 
@@ -34,7 +34,10 @@ use ethcore::error::BlockError;
 use ethcore::encoded;
 use ethcore::header::Header;
 use ethcore::ids::BlockId;
-use util::{H256, U256, HeapSizeOf, Mutex, RwLock};
+
+use rlp::{Encodable, Decodable, DecoderError, RlpStream, Rlp, UntrustedRlp};
+use util::{H256, U256, HeapSizeOf, RwLock};
+use util::kvdb::{DBTransaction, KeyValueDB};
 
 use smallvec::SmallVec;
 
@@ -43,6 +46,9 @@ use smallvec::SmallVec;
 /// relevant to any blocks we've got in memory.
 const HISTORY: u64 = 2048;
 
+/// The best block key. Maps to an RLP list: [best_era, last_era]
+const CURRENT_KEY: &'static [u8] = &*b"best_and_latest";
+
 /// Information about a block.
 #[derive(Debug, Clone)]
 pub struct BlockDescriptor {
@@ -75,42 +81,142 @@ impl HeapSizeOf for Entry {
 	}
 }
 
+impl Encodable for Entry {
+	fn rlp_append(&self, s: &mut RlpStream) {
+		s.begin_list(self.candidates.len());
+
+		for candidate in &self.candidates {
+			s.begin_list(3)
+				.append(&candidate.hash)
+				.append(&candidate.parent_hash)
+				.append(&candidate.total_difficulty);
+		}
+	}
+}
+
+impl Decodable for Entry {
+	fn decode(rlp: &UntrustedRlp) -> Result<Self, DecoderError> {
+
+		let mut candidates = SmallVec::<[Candidate; 3]>::new();
+
+		for item in rlp.iter() {
+			candidates.push(Candidate {
+				hash: item.val_at(0)?,
+				parent_hash: item.val_at(1)?,
+				total_difficulty: item.val_at(2)?,
+			})
+		}
+
+		if candidates.is_empty() { return Err(DecoderError::Custom("Empty candidates vector submitted.")) }
+
+		// rely on the invariant that the canonical entry is always first.
+		let canon_hash = candidates[0].hash;
+		Ok(Entry {
+			candidates: candidates,
+			canonical_hash: canon_hash,
+		})
+	}
+}
+
+fn cht_key(number: u64) -> String {
+	format!("{:08x}_canonical", number)
+}
+
+fn era_key(number: u64) -> String {
+	format!("candidates_{}", number)
+}
+
+/// Pending changes from `insert` to be applied after the database write has finished.
+pub struct PendingChanges {
+	best_block: Option<BlockDescriptor>, // new best block.
+}
+
 /// Header chain. See module docs for more details.
 pub struct HeaderChain {
 	genesis_header: encoded::Header, // special-case the genesis.
 	candidates: RwLock<BTreeMap<u64, Entry>>,
-	headers: RwLock<HashMap<H256, encoded::Header>>,
 	best_block: RwLock<BlockDescriptor>,
-	cht_roots: Mutex<Vec<H256>>,
+	db: Arc<KeyValueDB>,
+	col: Option<u32>,
 }
 
 impl HeaderChain {
-	/// Create a new header chain given this genesis block.
-	pub fn new(genesis: &[u8]) -> Self {
+	/// Create a new header chain given this genesis block and database to read from.
+	pub fn new(db: Arc<KeyValueDB>, col: Option<u32>, genesis: &[u8]) -> Result<Self, String> {
 		use ethcore::views::HeaderView;
 
-		let g_view = HeaderView::new(genesis);
+		let chain = if let Some(current) = db.get(col, CURRENT_KEY)? {
+			let (best_number, highest_number) = {
+				let rlp = Rlp::new(&current);
+				(rlp.val_at(0), rlp.val_at(1))
+			};
 
-		HeaderChain {
-			genesis_header: encoded::Header::new(genesis.to_owned()),
-			best_block: RwLock::new(BlockDescriptor {
-				hash: g_view.hash(),
-				number: 0,
-				total_difficulty: g_view.difficulty(),
-			}),
-			candidates: RwLock::new(BTreeMap::new()),
-			headers: RwLock::new(HashMap::new()),
-			cht_roots: Mutex::new(Vec::new()),
-		}
+			let mut cur_number = highest_number;
+			let mut candidates = BTreeMap::new();
+
+			// load all era entries and referenced headers within them.
+			while let Some(entry) = db.get(col, era_key(cur_number).as_bytes())? {
+				let entry: Entry = ::rlp::decode(&entry);
+				trace!(target: "chain", "loaded header chain entry for era {} with {} candidates",
+					cur_number, entry.candidates.len());
+
+				candidates.insert(cur_number, entry);
+
+				cur_number -= 1;
+			}
+
+			// fill best block block descriptor.
+			let best_block = {
+				let era = match candidates.get(&best_number) {
+					Some(era) => era,
+					None => return Err(format!("Database corrupt: highest block referenced but no data.")),
+				};
+
+				let best = &era.candidates[0];
+				BlockDescriptor {
+					hash: best.hash,
+					number: best_number,
+					total_difficulty: best.total_difficulty,
+				}
+			};
+
+			HeaderChain {
+				genesis_header: encoded::Header::new(genesis.to_owned()),
+				best_block: RwLock::new(best_block),
+				candidates: RwLock::new(candidates),
+				db: db,
+				col: col,
+			}
+		} else {
+			let g_view = HeaderView::new(genesis);
+			HeaderChain {
+				genesis_header: encoded::Header::new(genesis.to_owned()),
+				best_block: RwLock::new(BlockDescriptor {
+					hash: g_view.hash(),
+					number: 0,
+					total_difficulty: g_view.difficulty(),
+				}),
+				candidates: RwLock::new(BTreeMap::new()),
+				db: db,
+				col: col,
+			}
+		};
+
+		Ok(chain)
 	}
 
 	/// Insert a pre-verified header.
 	///
 	/// This blindly trusts that the data given to it is sensible.
-	pub fn insert(&self, header: Header) -> Result<(), BlockError> {
+	/// Returns a set of pending changes to be applied with `apply_pending`
+	/// before the next call to insert and after the transaction has been written.
+	pub fn insert(&self, transaction: &mut DBTransaction, header: Header) -> Result<PendingChanges, BlockError> {
 		let hash = header.hash();
 		let number = header.number();
 		let parent_hash = *header.parent_hash();
+		let mut pending = PendingChanges {
+			best_block: None,
+		};
 
 		// hold candidates the whole time to guard import order.
 		let mut candidates = self.candidates.write();
@@ -128,20 +234,41 @@ impl HeaderChain {
 
 		let total_difficulty = parent_td + *header.difficulty();
 
-		// insert headers and candidates entries.
-		candidates.entry(number).or_insert_with(|| Entry { candidates: SmallVec::new(), canonical_hash: hash })
-			.candidates.push(Candidate {
+		// insert headers and candidates entries and write era to disk.
+		{
+			let cur_era = candidates.entry(number)
+				.or_insert_with(|| Entry { candidates: SmallVec::new(), canonical_hash: hash });
+			cur_era.candidates.push(Candidate {
 				hash: hash,
 				parent_hash: parent_hash,
 				total_difficulty: total_difficulty,
-		});
+			});
 
-		let raw = ::rlp::encode(&header).to_vec();
-		self.headers.write().insert(hash, encoded::Header::new(raw));
+			// fix ordering of era before writing.
+			if total_difficulty > cur_era.candidates[0].total_difficulty {
+				let cur_pos = cur_era.candidates.len() - 1;
+				cur_era.candidates.swap(cur_pos, 0);
+				cur_era.canonical_hash = hash;
+			}
+
+			transaction.put(self.col, era_key(number).as_bytes(), &::rlp::encode(&*cur_era))
+		}
+
+		let raw = ::rlp::encode(&header);
+		transaction.put(self.col, &hash[..], &*raw);
+
+		let (best_num, is_new_best) = {
+			let cur_best = self.best_block.read();
+			if cur_best.total_difficulty < total_difficulty {
+				(number, true)
+			} else {
+				(cur_best.number, false)
+			}
+		};
 
 		// reorganize ancestors so canonical entries are first in their
 		// respective candidates vectors.
-		if self.best_block.read().total_difficulty < total_difficulty {
+		if is_new_best {
 			let mut canon_hash = hash;
 			for (&height, entry) in candidates.iter_mut().rev().skip_while(|&(height, _)| *height > number) {
 				if height != number && entry.canonical_hash == canon_hash { break; }
@@ -160,23 +287,26 @@ impl HeaderChain {
 				// what about reorgs > cht::SIZE + HISTORY?
 				// resetting to the last block of a given CHT should be possible.
 				canon_hash = entry.candidates[0].parent_hash;
+
+				// write altered era to disk
+				if height != number {
+					let rlp_era = ::rlp::encode(&*entry);
+					transaction.put(self.col, era_key(height).as_bytes(), &rlp_era);
+				}
 			}
 
 			trace!(target: "chain", "New best block: ({}, {}), TD {}", number, hash, total_difficulty);
-			*self.best_block.write() = BlockDescriptor {
+			pending.best_block = Some(BlockDescriptor {
 				hash: hash,
 				number: number,
 				total_difficulty: total_difficulty,
-			};
+			});
 
 			// produce next CHT root if it's time.
 			let earliest_era = *candidates.keys().next().expect("at least one era just created; qed");
 			if earliest_era + HISTORY + cht::SIZE <= number {
 				let cht_num = cht::block_to_cht_number(earliest_era)
 					.expect("fails only for number == 0; genesis never imported; qed");
-				debug_assert_eq!(cht_num as usize, self.cht_roots.lock().len());
-
-				let mut headers = self.headers.write();
 
 				let cht_root = {
 					let mut i = earliest_era;
@@ -186,10 +316,12 @@ impl HeaderChain {
 					let iter = || {
 						let era_entry = candidates.remove(&i)
 							.expect("all eras are sequential with no gaps; qed");
+						transaction.delete(self.col, era_key(i).as_bytes());
+
 						i += 1;
 
 						for ancient in &era_entry.candidates {
-							headers.remove(&ancient.hash);
+							transaction.delete(self.col, &ancient.hash);
 						}
 
 						let canon = &era_entry.candidates[0];
@@ -199,28 +331,56 @@ impl HeaderChain {
 						.expect("fails only when too few items; this is checked; qed")
 				};
 
+				// write the CHT root to the database.
 				debug!(target: "chain", "Produced CHT {} root: {:?}", cht_num, cht_root);
-
-				self.cht_roots.lock().push(cht_root);
+				transaction.put(self.col, cht_key(cht_num).as_bytes(), &::rlp::encode(&cht_root));
 			}
 		}
 
-		Ok(())
+		// write the best and latest eras to the database.
+		{
+			let latest_num = *candidates.iter().rev().next().expect("at least one era just inserted; qed").0;
+			let mut stream = RlpStream::new_list(2);
+			stream.append(&best_num).append(&latest_num);
+			transaction.put(self.col, CURRENT_KEY, &stream.out())
+		}
+		Ok(pending)
+	}
+
+	/// Apply pending changes from a previous `insert` operation.
+	/// Must be done before the next `insert` call.
+	pub fn apply_pending(&self, pending: PendingChanges) {
+		if let Some(best_block) = pending.best_block {
+			*self.best_block.write() = best_block;
+		}
 	}
 
 	/// Get a block header. In the case of query by number, only canonical blocks
 	/// will be returned.
 	pub fn block_header(&self, id: BlockId) -> Option<encoded::Header> {
+		let load_from_db = |hash: H256| {
+			match self.db.get(self.col, &hash) {
+				Ok(val) => val.map(|x| x.to_vec()).map(encoded::Header::new),
+				Err(e) => {
+					warn!(target: "chain", "Failed to read from database: {}", e);
+					None
+				}
+			}
+		};
+
 		match id {
 			BlockId::Earliest | BlockId::Number(0) => Some(self.genesis_header.clone()),
-			BlockId::Hash(hash) => self.headers.read().get(&hash).cloned(),
+			BlockId::Hash(hash) => load_from_db(hash),
 			BlockId::Number(num) => {
 				if self.best_block.read().number < num { return None }
 
 				self.candidates.read().get(&num).map(|entry| entry.canonical_hash)
-					.and_then(|hash| self.headers.read().get(&hash).cloned())
+					.and_then(load_from_db)
 			}
 			BlockId::Latest | BlockId::Pending => {
+				// hold candidates hear to prevent deletion of the header
+				// as we read it.
+				let _candidates = self.candidates.read();
 				let hash = {
 					let best = self.best_block.read();
 					if best.number == 0 {
@@ -230,7 +390,7 @@ impl HeaderChain {
 					best.hash
 				};
 
-				self.headers.read().get(&hash).cloned()
+				load_from_db(hash)
 			}
 		}
 	}
@@ -257,7 +417,13 @@ impl HeaderChain {
 	/// This is because it's assumed that the genesis hash is known,
 	/// so including it within a CHT would be redundant.
 	pub fn cht_root(&self, n: usize) -> Option<H256> {
-		self.cht_roots.lock().get(n).map(|h| h.clone())
+		match self.db.get(self.col, cht_key(n as u64).as_bytes()) {
+			Ok(val) => val.map(|x| ::rlp::decode(&x)),
+			Err(e) => {
+				warn!(target: "chain", "Error reading from database: {}", e);
+				None
+			}
+		}
 	}
 
 	/// Get the genesis hash.
@@ -287,7 +453,7 @@ impl HeaderChain {
 
 	/// Get block status.
 	pub fn status(&self, hash: &H256) -> BlockStatus {
-		match self.headers.read().contains_key(hash) {
+		match self.db.get(self.col, &*hash).ok().map_or(false, |x| x.is_some()) {
 			true => BlockStatus::InChain,
 			false => BlockStatus::Unknown,
 		}
@@ -296,9 +462,7 @@ impl HeaderChain {
 
 impl HeapSizeOf for HeaderChain {
 	fn heap_size_of_children(&self) -> usize {
-		self.candidates.read().heap_size_of_children() +
-			self.headers.read().heap_size_of_children() +
-			self.cht_roots.lock().heap_size_of_children()
+		self.candidates.read().heap_size_of_children()
 	}
 }
 
@@ -324,16 +488,23 @@ impl<'a> Iterator for AncestryIter<'a> {
 #[cfg(test)]
 mod tests {
 	use super::HeaderChain;
+	use std::sync::Arc;
+
 	use ethcore::ids::BlockId;
 	use ethcore::header::Header;
 	use ethcore::spec::Spec;
 
+	fn make_db() -> Arc<::util::KeyValueDB> {
+		Arc::new(::util::kvdb::in_memory(0))
+	}
+
 	#[test]
 	fn basic_chain() {
 		let spec = Spec::new_test();
 		let genesis_header = spec.genesis_header();
+		let db = make_db();
 
-		let chain = HeaderChain::new(&::rlp::encode(&genesis_header));
+		let chain = HeaderChain::new(db.clone(), None, &::rlp::encode(&genesis_header)).unwrap();
 
 		let mut parent_hash = genesis_header.hash();
 		let mut rolling_timestamp = genesis_header.timestamp();
@@ -345,7 +516,10 @@ mod tests {
 			header.set_difficulty(*genesis_header.difficulty() * i.into());
 			parent_hash = header.hash();
 
-			chain.insert(header).unwrap();
+			let mut tx = db.transaction();
+			let pending = chain.insert(&mut tx, header).unwrap();
+			db.write(tx).unwrap();
+			chain.apply_pending(pending);
 
 			rolling_timestamp += 10;
 		}
@@ -361,7 +535,8 @@ mod tests {
 		let spec = Spec::new_test();
 		let genesis_header = spec.genesis_header();
 
-		let chain = HeaderChain::new(&::rlp::encode(&genesis_header));
+		let db = make_db();
+		let chain = HeaderChain::new(db.clone(), None, &::rlp::encode(&genesis_header)).unwrap();
 
 		let mut parent_hash = genesis_header.hash();
 		let mut rolling_timestamp = genesis_header.timestamp();
@@ -373,7 +548,10 @@ mod tests {
 			header.set_difficulty(*genesis_header.difficulty() * i.into());
 			parent_hash = header.hash();
 
-			chain.insert(header).unwrap();
+			let mut tx = db.transaction();
+			let pending = chain.insert(&mut tx, header).unwrap();
+			db.write(tx).unwrap();
+			chain.apply_pending(pending);
 
 			rolling_timestamp += 10;
 		}
@@ -389,7 +567,10 @@ mod tests {
 				header.set_difficulty(*genesis_header.difficulty() * i.into());
 				parent_hash = header.hash();
 
-				chain.insert(header).unwrap();
+				let mut tx = db.transaction();
+				let pending = chain.insert(&mut tx, header).unwrap();
+				db.write(tx).unwrap();
+				chain.apply_pending(pending);
 
 				rolling_timestamp += 10;
 			}
@@ -410,7 +591,10 @@ mod tests {
 				header.set_difficulty(*genesis_header.difficulty() * (i * i).into());
 				parent_hash = header.hash();
 
-				chain.insert(header).unwrap();
+				let mut tx = db.transaction();
+				let pending = chain.insert(&mut tx, header).unwrap();
+				db.write(tx).unwrap();
+				chain.apply_pending(pending);
 
 				rolling_timestamp += 11;
 			}
@@ -432,11 +616,101 @@ mod tests {
 	fn earliest_is_latest() {
 		let spec = Spec::new_test();
 		let genesis_header = spec.genesis_header();
+		let db = make_db();
 
-		let chain = HeaderChain::new(&::rlp::encode(&genesis_header));
+		let chain = HeaderChain::new(db.clone(), None, &::rlp::encode(&genesis_header)).unwrap();
 
 		assert!(chain.block_header(BlockId::Earliest).is_some());
 		assert!(chain.block_header(BlockId::Latest).is_some());
 		assert!(chain.block_header(BlockId::Pending).is_some());
 	}
+
+	#[test]
+	fn restore_from_db() {
+		let spec = Spec::new_test();
+		let genesis_header = spec.genesis_header();
+		let db = make_db();
+
+		{
+			let chain = HeaderChain::new(db.clone(), None, &::rlp::encode(&genesis_header)).unwrap();
+			let mut parent_hash = genesis_header.hash();
+			let mut rolling_timestamp = genesis_header.timestamp();
+			for i in 1..10000 {
+				let mut header = Header::new();
+				header.set_parent_hash(parent_hash);
+				header.set_number(i);
+				header.set_timestamp(rolling_timestamp);
+				header.set_difficulty(*genesis_header.difficulty() * i.into());
+				parent_hash = header.hash();
+
+				let mut tx = db.transaction();
+				let pending = chain.insert(&mut tx, header).unwrap();
+				db.write(tx).unwrap();
+				chain.apply_pending(pending);
+
+				rolling_timestamp += 10;
+			}
+		}
+
+		let chain = HeaderChain::new(db.clone(), None, &::rlp::encode(&genesis_header)).unwrap();
+		assert!(chain.block_header(BlockId::Number(10)).is_none());
+		assert!(chain.block_header(BlockId::Number(9000)).is_some());
+		assert!(chain.cht_root(2).is_some());
+		assert!(chain.cht_root(3).is_none());
+		assert_eq!(chain.block_header(BlockId::Latest).unwrap().number(), 9999);
+	}
+
+	#[test]
+	fn restore_higher_non_canonical() {
+		let spec = Spec::new_test();
+		let genesis_header = spec.genesis_header();
+		let db = make_db();
+
+		{
+			let chain = HeaderChain::new(db.clone(), None, &::rlp::encode(&genesis_header)).unwrap();
+			let mut parent_hash = genesis_header.hash();
+			let mut rolling_timestamp = genesis_header.timestamp();
+
+			// push 100 low-difficulty blocks.
+			for i in 1..101 {
+				let mut header = Header::new();
+				header.set_parent_hash(parent_hash);
+				header.set_number(i);
+				header.set_timestamp(rolling_timestamp);
+				header.set_difficulty(*genesis_header.difficulty() * i.into());
+				parent_hash = header.hash();
+
+				let mut tx = db.transaction();
+				let pending = chain.insert(&mut tx, header).unwrap();
+				db.write(tx).unwrap();
+				chain.apply_pending(pending);
+
+				rolling_timestamp += 10;
+			}
+
+			// push fewer high-difficulty blocks.
+			for i in 1..11 {
+				let mut header = Header::new();
+				header.set_parent_hash(parent_hash);
+				header.set_number(i);
+				header.set_timestamp(rolling_timestamp);
+				header.set_difficulty(*genesis_header.difficulty() * i.into() * 1000.into());
+				parent_hash = header.hash();
+
+				let mut tx = db.transaction();
+				let pending = chain.insert(&mut tx, header).unwrap();
+				db.write(tx).unwrap();
+				chain.apply_pending(pending);
+
+				rolling_timestamp += 10;
+			}
+
+			assert_eq!(chain.block_header(BlockId::Latest).unwrap().number(), 10);
+		}
+
+		// after restoration, non-canonical eras should still be loaded.
+		let chain = HeaderChain::new(db.clone(), None, &::rlp::encode(&genesis_header)).unwrap();
+		assert_eq!(chain.block_header(BlockId::Latest).unwrap().number(), 10);
+		assert!(chain.candidates.read().get(&100).is_some())
+	}
 }

ethcore/light/src/client/mod.rs

@@ -32,6 +32,7 @@ use ethcore::encoded;
 use io::IoChannel;
 
 use util::{H256, Mutex, RwLock};
+use util::kvdb::{KeyValueDB, CompactionProfile};
 
 use self::header_chain::{AncestryIter, HeaderChain};
 
@@ -45,6 +46,14 @@ mod service;
 pub struct Config {
 	/// Verification queue config.
 	pub queue: queue::Config,
+	/// Chain column in database.
+	pub chain_column: Option<u32>,
+	/// Database cache size. `None` => rocksdb default.
+	pub db_cache_size: Option<usize>,
+	/// State db compaction profile
+	pub db_compaction: CompactionProfile,
+	/// Should db have WAL enabled?
+	pub db_wal: bool,
 }
 
 /// Trait for interacting with the header chain abstractly.
@@ -106,18 +115,30 @@ pub struct Client {
 	chain: HeaderChain,
 	report: RwLock<ClientReport>,
 	import_lock: Mutex<()>,
+	db: Arc<KeyValueDB>,
 }
 
 impl Client {
 	/// Create a new `Client`.
-	pub fn new(config: Config, spec: &Spec, io_channel: IoChannel<ClientIoMessage>) -> Self {
-		Client {
+	pub fn new(config: Config, db: Arc<KeyValueDB>, chain_col: Option<u32>, spec: &Spec, io_channel: IoChannel<ClientIoMessage>) -> Result<Self, String> {
+		let gh = ::rlp::encode(&spec.genesis_header());
+
+		Ok(Client {
 			queue: HeaderQueue::new(config.queue, spec.engine.clone(), io_channel, true),
 			engine: spec.engine.clone(),
-			chain: HeaderChain::new(&::rlp::encode(&spec.genesis_header())),
+			chain: HeaderChain::new(db.clone(), chain_col, &gh)?,
 			report: RwLock::new(ClientReport::default()),
 			import_lock: Mutex::new(()),
-		}
+			db: db,
+		})
+	}
+
+	/// Create a new `Client` backed purely in-memory.
+	/// This will ignore all database options in the configuration.
+	pub fn in_memory(config: Config, spec: &Spec, io_channel: IoChannel<ClientIoMessage>) -> Self {
+		let db = ::util::kvdb::in_memory(0);
+
+		Client::new(config, Arc::new(db), None, spec, io_channel).expect("New DB creation infallible; qed")
 	}
 
 	/// Import a header to the queue for additional verification.
@@ -201,15 +222,23 @@ impl Client {
 		for verified_header in self.queue.drain(MAX) {
 			let (num, hash) = (verified_header.number(), verified_header.hash());
 
-			match self.chain.insert(verified_header) {
-				Ok(()) => {
+			let mut tx = self.db.transaction();
+			let pending = match self.chain.insert(&mut tx, verified_header) {
+				Ok(pending) => {
 					good.push(hash);
 					self.report.write().blocks_imported += 1;
+					pending
 				}
 				Err(e) => {
 					debug!(target: "client", "Error importing header {:?}: {}", (num, hash), e);
 					bad.push(hash);
+					break;
 				}
+			};
+			self.db.write_buffered(tx);
+			self.chain.apply_pending(pending);
+			if let Err(e) = self.db.flush() {
+				panic!("Database flush failed: {}. Check disk health and space.", e);
 			}
 		}
 

ethcore/light/src/client/service.rs

@@ -17,33 +17,80 @@
 //! Minimal IO service for light client.
 //! Just handles block import messages and passes them to the client.
 
+use std::fmt;
+use std::path::Path;
 use std::sync::Arc;
 
+use ethcore::db;
 use ethcore::service::ClientIoMessage;
 use ethcore::spec::Spec;
 use io::{IoContext, IoError, IoHandler, IoService};
+use util::kvdb::{Database, DatabaseConfig};
 
 use super::{Client, Config as ClientConfig};
 
+/// Errors on service initialization.
+#[derive(Debug)]
+pub enum Error {
+	/// Database error.
+	Database(String),
+	/// I/O service error.
+	Io(IoError),
+}
+
+impl fmt::Display for Error {
+	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+		match *self {
+			Error::Database(ref msg) => write!(f, "Database error: {}", msg),
+			Error::Io(ref err) => write!(f, "I/O service error: {}", err),
+		}
+	}
+}
+
 /// Light client service.
 pub struct Service {
 	client: Arc<Client>,
-	_io_service: IoService<ClientIoMessage>,
+	io_service: IoService<ClientIoMessage>,
 }
 
 impl Service {
 	/// Start the service: initialize I/O workers and client itself.
-	pub fn start(config: ClientConfig, spec: &Spec) -> Result<Self, IoError> {
-		let io_service = try!(IoService::<ClientIoMessage>::start());
-		let client = Arc::new(Client::new(config, spec, io_service.channel()));
-		try!(io_service.register_handler(Arc::new(ImportBlocks(client.clone()))));
+	pub fn start(config: ClientConfig, spec: &Spec, path: &Path) -> Result<Self, Error> {
+		// initialize database.
+		let mut db_config = DatabaseConfig::with_columns(db::NUM_COLUMNS);
 
+		// give all rocksdb cache to the header chain column.
+		if let Some(size) = config.db_cache_size {
+			db_config.set_cache(db::COL_LIGHT_CHAIN, size);
+		}
+
+		db_config.compaction = config.db_compaction;
+		db_config.wal = config.db_wal;
+
+		let db = Arc::new(Database::open(
+			&db_config,
+			&path.to_str().expect("DB path could not be converted to string.")
+		).map_err(Error::Database)?);
+
+		let io_service = IoService::<ClientIoMessage>::start().map_err(Error::Io)?;
+		let client = Arc::new(Client::new(config,
+			db,
+			db::COL_LIGHT_CHAIN,
+			spec,
+			io_service.channel(),
+		).map_err(Error::Database)?);
+		io_service.register_handler(Arc::new(ImportBlocks(client.clone()))).map_err(Error::Io)?;
 		Ok(Service {
 			client: client,
-			_io_service: io_service,
+			io_service: io_service,
 		})
 	}
 
+	/// Register an I/O handler on the service.
+	pub fn register_handler(&self, handler: Arc<IoHandler<ClientIoMessage> + Send>) -> Result<(), IoError> {
+		self.io_service.register_handler(handler)
+	}
+
 	/// Get a handle to the client.
 	pub fn client(&self) -> &Arc<Client> {
 		&self.client
@@ -63,11 +110,13 @@ impl IoHandler<ClientIoMessage> for ImportBlocks {
 #[cfg(test)]
 mod tests {
 	use super::Service;
+	use devtools::RandomTempPath;
 	use ethcore::spec::Spec;
 
 	#[test]
 	fn it_works() {
 		let spec = Spec::new_test();
-		Service::start(Default::default(), &spec).unwrap();
+		let temp_path = RandomTempPath::new();
+		Service::start(Default::default(), &spec, temp_path.as_path()).unwrap();
 	}
 }

ethcore/light/src/lib.rs

@@ -55,6 +55,7 @@ pub mod remote {
 
 mod types;
 
+pub use self::cache::Cache;
 pub use self::provider::Provider;
 pub use self::transaction_queue::TransactionQueue;
 pub use types::request as request;
@@ -76,3 +77,6 @@ extern crate stats;
 
 #[cfg(feature = "ipc")]
 extern crate ethcore_ipc as ipc;
+
+#[cfg(test)]
+extern crate ethcore_devtools as devtools;

ethcore/light/src/net/context.rs

@@ -61,10 +61,12 @@ impl<'a> IoContext for NetworkContext<'a> {
 	}
 
 	fn disconnect_peer(&self, peer: PeerId) {
+		trace!(target: "pip", "Initiating disconnect of peer {}", peer);
 		NetworkContext::disconnect_peer(self, peer);
 	}
 
 	fn disable_peer(&self, peer: PeerId) {
+		trace!(target: "pip", "Initiating disable of peer {}", peer);
 		NetworkContext::disable_peer(self, peer);
 	}
 

ethcore/light/src/net/mod.rs

@@ -27,7 +27,7 @@ use util::hash::H256;
 use util::{DBValue, Mutex, RwLock, U256};
 use time::{Duration, SteadyTime};
 
-use std::collections::HashMap;
+use std::collections::{HashMap, HashSet};
 use std::fmt;
 use std::sync::Arc;
 use std::sync::atomic::{AtomicUsize, Ordering};
@@ -61,6 +61,9 @@ const TIMEOUT_INTERVAL_MS: u64 = 1000;
 const TICK_TIMEOUT: TimerToken = 1;
 const TICK_TIMEOUT_INTERVAL_MS: u64 = 5000;
 
+const PROPAGATE_TIMEOUT: TimerToken = 2;
+const PROPAGATE_TIMEOUT_INTERVAL_MS: u64 = 5000;
+
 // minimum interval between updates.
 const UPDATE_INTERVAL_MS: i64 = 5000;
 
@@ -132,6 +135,7 @@ pub struct Peer {
 	last_update: SteadyTime,
 	pending_requests: RequestSet,
 	failed_requests: Vec<ReqId>,
+	propagated_transactions: HashSet<H256>,
 }
 
 /// A light protocol event handler.
@@ -303,12 +307,18 @@ impl LightProtocol {
 		match peer.remote_flow {
 			None => Err(Error::NotServer),
 			Some((ref mut creds, ref params)) => {
-				// check that enough credits are available.
-				let mut temp_creds: Credits = creds.clone();
-				for request in requests.requests() {
-					temp_creds.deduct_cost(params.compute_cost(request))?;
+				// apply recharge to credits if there's no pending requests.
+				if peer.pending_requests.is_empty() {
+					params.recharge(creds);
 				}
-				*creds = temp_creds;
+
+				// compute and deduct cost.
+				let pre_creds = creds.current();
+				let cost = params.compute_cost_multi(requests.requests());
+				creds.deduct_cost(cost)?;
+
+				trace!(target: "pip", "requesting from peer {}. Cost: {}; Available: {}",
+					peer_id, cost, pre_creds);
 
 				let req_id = ReqId(self.req_id.fetch_add(1, Ordering::SeqCst));
 				io.send(*peer_id, packet::REQUEST, {
@@ -318,7 +328,7 @@ impl LightProtocol {
 				});
 
 				// begin timeout.
-				peer.pending_requests.insert(req_id, requests, SteadyTime::now());
+				peer.pending_requests.insert(req_id, requests, cost, SteadyTime::now());
 				Ok(req_id)
 			}
 		}
@@ -401,20 +411,25 @@ impl LightProtocol {
 		let req_id = ReqId(raw.val_at(0)?);
 		let cur_credits: U256 = raw.val_at(1)?;
 
-		trace!(target: "pip", "pre-verifying response from peer {}", peer);
+		trace!(target: "pip", "pre-verifying response for {} from peer {}", req_id, peer);
 
 		let peers = self.peers.read();
 		let res = match peers.get(peer) {
 			Some(peer_info) => {
 				let mut peer_info = peer_info.lock();
 				let req_info = peer_info.pending_requests.remove(&req_id, SteadyTime::now());
+				let cumulative_cost = peer_info.pending_requests.cumulative_cost();
 				let flow_info = peer_info.remote_flow.as_mut();
 
 				match (req_info, flow_info) {
 					(Some(_), Some(flow_info)) => {
 						let &mut (ref mut c, ref mut flow) = flow_info;
-						let actual_credits = ::std::cmp::min(cur_credits, *flow.limit());
-						c.update_to(actual_credits);
+
+						// only update if the cumulative cost of the request set is zero.
+						if cumulative_cost == 0.into() {
+							let actual_credits = ::std::cmp::min(cur_credits, *flow.limit());
+							c.update_to(actual_credits);
+						}
 
 						Ok(())
 					}
@@ -488,6 +503,47 @@ impl LightProtocol {
 		}
 	}
 
+	// propagate transactions to relay peers.
+	// if we aren't on the mainnet, we just propagate to all relay peers
+	fn propagate_transactions(&self, io: &IoContext) {
+		if self.capabilities.read().tx_relay { return }
+
+		let ready_transactions = self.provider.ready_transactions();
+		if ready_transactions.is_empty() { return }
+
+		trace!(target: "pip", "propagate transactions: {} ready", ready_transactions.len());
+
+		let all_transaction_hashes: HashSet<_> = ready_transactions.iter().map(|tx| tx.hash()).collect();
+		let mut buf = Vec::new();
+
+		let peers = self.peers.read();
+		for (peer_id, peer_info) in peers.iter() {
+			let mut peer_info = peer_info.lock();
+			if !peer_info.capabilities.tx_relay { continue }
+
+			let prop_filter = &mut peer_info.propagated_transactions;
+			*prop_filter = &*prop_filter & &all_transaction_hashes;
+
+			// fill the buffer with all non-propagated transactions.
+			let to_propagate = ready_transactions.iter()
+				.filter(|tx| prop_filter.insert(tx.hash()))
+				.map(|tx| &tx.transaction);
+
+			buf.extend(to_propagate);
+
+			// propagate to the given peer.
+			if buf.is_empty() { continue }
+			io.send(*peer_id, packet::SEND_TRANSACTIONS, {
+				let mut stream = RlpStream::new_list(buf.len());
+				for pending_tx in buf.drain(..) {
+					stream.append(pending_tx);
+				}
+
+				stream.out()
+			})
+		}
+	}
+
 	/// called when a peer connects.
 	pub fn on_connect(&self, peer: &PeerId, io: &IoContext) {
 		let proto_version = match io.protocol_version(*peer).ok_or(Error::WrongNetwork) {
@@ -520,6 +576,7 @@ impl LightProtocol {
 			last_update: SteadyTime::now(),
 		});
 
+		trace!(target: "pip", "Sending status to peer {}", peer);
 		io.send(*peer, packet::STATUS, status_packet);
 	}
 
@@ -601,6 +658,7 @@ impl LightProtocol {
 			last_update: pending.last_update,
 			pending_requests: RequestSet::default(),
 			failed_requests: Vec::new(),
+			propagated_transactions: HashSet::new(),
 		}));
 
 		for handler in &self.handlers {
@@ -683,6 +741,8 @@ impl LightProtocol {
 		trace!(target: "pip", "Received requests (id: {}) from peer {}", req_id, peer_id);
 
 		// deserialize requests, check costs and request validity.
+		self.flow_params.recharge(&mut peer.local_credits);
+
 		peer.local_credits.deduct_cost(self.flow_params.base_cost())?;
 		for request_rlp in raw.at(1)?.iter().take(MAX_REQUESTS) {
 			let request: Request = request_rlp.as_val()?;
@@ -709,6 +769,7 @@ impl LightProtocol {
 		});
 
 		trace!(target: "pip", "Responded to {}/{} requests in packet {}", responses.len(), num_requests, req_id);
+		trace!(target: "pip", "Peer {} has {} credits remaining.", peer_id, peer.local_credits.current());
 
 		io.respond(packet::RESPONSE, {
 			let mut stream = RlpStream::new_list(3);
@@ -782,6 +843,8 @@ impl NetworkProtocolHandler for LightProtocol {
 			.expect("Error registering sync timer.");
 		io.register_timer(TICK_TIMEOUT, TICK_TIMEOUT_INTERVAL_MS)
 			.expect("Error registering sync timer.");
+		io.register_timer(PROPAGATE_TIMEOUT, PROPAGATE_TIMEOUT_INTERVAL_MS)
+			.expect("Error registering sync timer.");
 	}
 
 	fn read(&self, io: &NetworkContext, peer: &PeerId, packet_id: u8, data: &[u8]) {
@@ -800,6 +863,7 @@ impl NetworkProtocolHandler for LightProtocol {
 		match timer {
 			TIMEOUT => self.timeout_check(io),
 			TICK_TIMEOUT => self.tick_handlers(io),
+			PROPAGATE_TIMEOUT => self.propagate_transactions(io),
 			_ => warn!(target: "pip", "received timeout on unknown token {}", timer),
 		}
 	}

ethcore/light/src/net/request_set.rs

@@ -27,22 +27,29 @@ use std::iter::FromIterator;
 use request::Request;
 use request::Requests;
 use net::{timeout, ReqId};
+use util::U256;
 
 use time::{Duration, SteadyTime};
 
+// Request set entry: requests + cost.
+#[derive(Debug)]
+struct Entry(Requests, U256);
+
 /// Request set.
 #[derive(Debug)]
 pub struct RequestSet {
 	counter: u64,
+	cumulative_cost: U256,
 	base: Option<SteadyTime>,
 	ids: HashMap<ReqId, u64>,
-	reqs: BTreeMap<u64, Requests>,
+	reqs: BTreeMap<u64, Entry>,
 }
 
 impl Default for RequestSet {
 	fn default() -> Self {
 		RequestSet {
 			counter: 0,
+			cumulative_cost: 0.into(),
 			base: None,
 			ids: HashMap::new(),
 			reqs: BTreeMap::new(),
@@ -52,10 +59,12 @@ impl Default for RequestSet {
 
 impl RequestSet {
 	/// Push requests onto the stack.
-	pub fn insert(&mut self, req_id: ReqId, req: Requests, now: SteadyTime) {
+	pub fn insert(&mut self, req_id: ReqId, req: Requests, cost: U256, now: SteadyTime) {
 		let counter = self.counter;
+		self.cumulative_cost = self.cumulative_cost + cost;
+
 		self.ids.insert(req_id, counter);
-		self.reqs.insert(counter, req);
+		self.reqs.insert(counter, Entry(req, cost));
 
 		if self.reqs.keys().next().map_or(true, |x| *x == counter) {
 			self.base = Some(now);
@@ -71,7 +80,7 @@ impl RequestSet {
 			None => return None,
 		};
 
-		let req = self.reqs.remove(&id).expect("entry in `ids` implies entry in `reqs`; qed");
+		let Entry(req, cost) = self.reqs.remove(&id).expect("entry in `ids` implies entry in `reqs`; qed");
 
 		match self.reqs.keys().next() {
 			Some(k) if *k > id => self.base = Some(now),
@@ -79,6 +88,7 @@ impl RequestSet {
 			_ => {}
 		}
 
+		self.cumulative_cost = self.cumulative_cost - cost;
 		Some(req)
 	}
 
@@ -93,7 +103,7 @@ impl RequestSet {
 		let first_req = self.reqs.values().next()
 			.expect("base existing implies `reqs` non-empty; qed");
 
-		base + compute_timeout(&first_req) <= now
+		base + compute_timeout(&first_req.0) <= now
 	}
 
 	/// Collect all pending request ids.
@@ -108,6 +118,9 @@ impl RequestSet {
 
 	/// Whether the set is empty.
 	pub fn is_empty(&self) -> bool { self.len() == 0 }
+
+	/// The cumulative cost of all requests in the set.
+	pub fn cumulative_cost(&self) -> U256 { self.cumulative_cost }
 }
 
 // helper to calculate timeout for a specific set of requests.
@@ -141,8 +154,8 @@ mod tests {
 
 		let the_req = RequestBuilder::default().build();
 		let req_time = compute_timeout(&the_req);
-		req_set.insert(ReqId(0), the_req.clone(), test_begin);
-		req_set.insert(ReqId(1), the_req, test_begin + Duration::seconds(1));
+		req_set.insert(ReqId(0), the_req.clone(), 0.into(), test_begin);
+		req_set.insert(ReqId(1), the_req, 0.into(), test_begin + Duration::seconds(1));
 
 		assert_eq!(req_set.base, Some(test_begin));
 
@@ -153,4 +166,22 @@ mod tests {
 		assert!(!req_set.check_timeout(test_end));
 		assert!(req_set.check_timeout(test_end + Duration::seconds(1)));
 	}
+
+	#[test]
+	fn cumulative_cost() {
+		let the_req = RequestBuilder::default().build();
+		let test_begin = SteadyTime::now();
+		let test_end = test_begin + Duration::seconds(1);
+		let mut req_set = RequestSet::default();
+
+		for i in 0..5 {
+			req_set.insert(ReqId(i), the_req.clone(), 1.into(), test_begin);
+			assert_eq!(req_set.cumulative_cost, (i + 1).into());
+		}
+
+		for i in (0..5).rev() {
+			assert!(req_set.remove(&ReqId(i), test_end).is_some());
+			assert_eq!(req_set.cumulative_cost, i.into());
+		}
+	}
 }

ethcore/light/src/net/tests/mod.rs

@@ -600,8 +600,8 @@ fn id_guard() {
 
 	let mut pending_requests = RequestSet::default();
 
-	pending_requests.insert(req_id_1, req.clone(), ::time::SteadyTime::now());
-	pending_requests.insert(req_id_2, req, ::time::SteadyTime::now());
+	pending_requests.insert(req_id_1, req.clone(), 0.into(), ::time::SteadyTime::now());
+	pending_requests.insert(req_id_2, req, 1.into(), ::time::SteadyTime::now());
 
 	proto.peers.write().insert(peer_id, ::util::Mutex::new(Peer {
 		local_credits: flow_params.create_credits(),
@@ -612,6 +612,7 @@ fn id_guard() {
 		last_update: ::time::SteadyTime::now(),
 		pending_requests: pending_requests,
 		failed_requests: Vec::new(),
+		propagated_transactions: Default::default(),
 	}));
 
 	// first, malformed responses.

ethcore/light/src/on_demand/mod.rs

@@ -37,7 +37,7 @@ use rlp::RlpStream;
 use util::{Bytes, RwLock, Mutex, U256, H256};
 use util::sha3::{SHA3_NULL_RLP, SHA3_EMPTY_LIST_RLP};
 
-use net::{Handler, Status, Capabilities, Announcement, EventContext, BasicContext, ReqId};
+use net::{self, Handler, Status, Capabilities, Announcement, EventContext, BasicContext, ReqId};
 use cache::Cache;
 use request::{self as basic_request, Request as NetworkRequest, Response as NetworkResponse};
 
@@ -57,15 +57,15 @@ impl Peer {
 				self.capabilities.serve_headers && self.status.head_num > req.num(),
 			Pending::HeaderByHash(_, _) => self.capabilities.serve_headers,
 			Pending::Block(ref req, _) =>
-				self.capabilities.serve_chain_since.as_ref().map_or(false, |x| *x >= req.header.number()),
+				self.capabilities.serve_chain_since.as_ref().map_or(false, |x| *x <= req.header.number()),
 			Pending::BlockReceipts(ref req, _) =>
-				self.capabilities.serve_chain_since.as_ref().map_or(false, |x| *x >= req.0.number()),
+				self.capabilities.serve_chain_since.as_ref().map_or(false, |x| *x <= req.0.number()),
 			Pending::Account(ref req, _) =>
-				self.capabilities.serve_state_since.as_ref().map_or(false, |x| *x >= req.header.number()),
+				self.capabilities.serve_state_since.as_ref().map_or(false, |x| *x <= req.header.number()),
 			Pending::Code(ref req, _) =>
-				self.capabilities.serve_state_since.as_ref().map_or(false, |x| *x >= req.block_id.1),
+				self.capabilities.serve_state_since.as_ref().map_or(false, |x| *x <= req.block_id.1),
 			Pending::TxProof(ref req, _) =>
-				self.capabilities.serve_state_since.as_ref().map_or(false, |x| *x >= req.header.number()),
+				self.capabilities.serve_state_since.as_ref().map_or(false, |x| *x <= req.header.number()),
 		}
 	}
 }
@@ -210,7 +210,7 @@ impl OnDemand {
 	/// it as easily.
 	pub fn header_by_hash(&self, ctx: &BasicContext, req: request::HeaderByHash) -> Receiver<encoded::Header> {
 		let (sender, receiver) = oneshot::channel();
-		match self.cache.lock().block_header(&req.0) {
+		match { self.cache.lock().block_header(&req.0) } {
 			Some(hdr) => sender.send(hdr).expect(RECEIVER_IN_SCOPE),
 			None => self.dispatch(ctx, Pending::HeaderByHash(req, sender)),
 		}
@@ -232,11 +232,13 @@ impl OnDemand {
 
 			sender.send(encoded::Block::new(stream.out())).expect(RECEIVER_IN_SCOPE);
 		} else {
-			match self.cache.lock().block_body(&req.hash) {
+			match { self.cache.lock().block_body(&req.hash) } {
 				Some(body) => {
 					let mut stream = RlpStream::new_list(3);
+					let body = body.rlp();
 					stream.append_raw(&req.header.into_inner(), 1);
-					stream.append_raw(&body.into_inner(), 2);
+					stream.append_raw(&body.at(0).as_raw(), 1);
+					stream.append_raw(&body.at(1).as_raw(), 1);
 
 					sender.send(encoded::Block::new(stream.out())).expect(RECEIVER_IN_SCOPE);
 				}
@@ -255,7 +257,7 @@ impl OnDemand {
 		if req.0.receipts_root() == SHA3_NULL_RLP {
 			sender.send(Vec::new()).expect(RECEIVER_IN_SCOPE);
 		} else {
-			match self.cache.lock().block_receipts(&req.0.hash()) {
+			match { self.cache.lock().block_receipts(&req.0.hash()) } {
 				Some(receipts) => sender.send(receipts).expect(RECEIVER_IN_SCOPE),
 				None => self.dispatch(ctx, Pending::BlockReceipts(req, sender)),
 			}
@@ -303,23 +305,26 @@ impl OnDemand {
 
 		let complete = builder.build();
 
+		let kind = complete.requests()[0].kind();
 		for (id, peer) in self.peers.read().iter() {
 			if !peer.can_handle(&pending) { continue }
 			match ctx.request_from(*id, complete.clone()) {
 				Ok(req_id) => {
-					trace!(target: "on_demand", "Assigning request to peer {}", id);
+					trace!(target: "on_demand", "{}: Assigned {:?} to peer {}",
+						req_id, kind, id);
+
 					self.pending_requests.write().insert(
 						req_id,
 						pending,
 					);
 					return
 				}
+				Err(net::Error::NoCredits) => {}
 				Err(e) =>
 					trace!(target: "on_demand", "Failed to make request of peer {}: {:?}", id, e),
 			}
 		}
 
-		trace!(target: "on_demand", "No suitable peer for request");
 		self.orphaned_requests.write().push(pending);
 	}
 
@@ -353,6 +358,7 @@ impl OnDemand {
 
 		let to_dispatch = ::std::mem::replace(&mut *self.orphaned_requests.write(), Vec::new());
 
+		trace!(target: "on_demand", "Attempting to dispatch {} orphaned requests.", to_dispatch.len());
 		for mut orphaned in to_dispatch {
 			let hung_up = match orphaned {
 				Pending::HeaderProof(_, ref mut sender) => match *sender {
@@ -397,10 +403,12 @@ impl Handler for OnDemand {
 	}
 
 	fn on_announcement(&self, ctx: &EventContext, announcement: &Announcement) {
-		let mut peers = self.peers.write();
-		if let Some(ref mut peer) = peers.get_mut(&ctx.peer()) {
-			peer.status.update_from(&announcement);
-			peer.capabilities.update_from(&announcement);
+		{
+			let mut peers = self.peers.write();
+			if let Some(ref mut peer) = peers.get_mut(&ctx.peer()) {
+				peer.status.update_from(&announcement);
+				peer.capabilities.update_from(&announcement);
+			}
 		}
 
 		self.dispatch_orphaned(ctx.as_basic());
@@ -422,6 +430,8 @@ impl Handler for OnDemand {
 			}
 		};
 
+		trace!(target: "on_demand", "Handling response for request {}, kind={:?}", req_id, response.kind());
+
 		// handle the response appropriately for the request.
 		// all branches which do not return early lead to disabling of the peer
 		// due to misbehavior.
@@ -441,7 +451,7 @@ impl Handler for OnDemand {
 							}
 							return
 						}
-						Err(e) => warn!("Error handling response for header request: {:?}", e),
+						Err(e) => warn!(target: "on_demand", "Error handling response for header request: {:?}", e),
 					}
 				}
 			}
@@ -454,7 +464,7 @@ impl Handler for OnDemand {
 								let _ = sender.send(header);
 								return
 							}
-							Err(e) => warn!("Error handling response for header request: {:?}", e),
+							Err(e) => warn!(target: "on_demand", "Error handling response for header request: {:?}", e),
 						}
 					}
 				}
@@ -467,7 +477,7 @@ impl Handler for OnDemand {
 							let _ = sender.send(block);
 							return
 						}
-						Err(e) => warn!("Error handling response for block request: {:?}", e),
+						Err(e) => warn!(target: "on_demand", "Error handling response for block request: {:?}", e),
 					}
 				}
 			}
@@ -480,7 +490,7 @@ impl Handler for OnDemand {
 							let _ = sender.send(receipts);
 							return
 						}
-						Err(e) => warn!("Error handling response for receipts request: {:?}", e),
+						Err(e) => warn!(target: "on_demand", "Error handling response for receipts request: {:?}", e),
 					}
 				}
 			}
@@ -493,7 +503,7 @@ impl Handler for OnDemand {
 							let _ = sender.send(maybe_account);
 							return
 						}
-						Err(e) => warn!("Error handling response for state request: {:?}", e),
+						Err(e) => warn!(target: "on_demand", "Error handling response for state request: {:?}", e),
 					}
 				}
 			}
@@ -504,7 +514,7 @@ impl Handler for OnDemand {
 							let _ = sender.send(response.code.clone());
 							return
 						}
-						Err(e) => warn!("Error handling response for code request: {:?}", e),
+						Err(e) => warn!(target: "on_demand", "Error handling response for code request: {:?}", e),
 					}
 				}
 			}
@@ -519,7 +529,7 @@ impl Handler for OnDemand {
 							let _ = sender.send(Err(err));
 							return
 						}
-						ProvedExecution::BadProof => warn!("Error handling response for transaction proof request"),
+						ProvedExecution::BadProof => warn!(target: "on_demand", "Error handling response for transaction proof request"),
 					}
 				}
 			}

ethcore/light/src/on_demand/request.rs

@@ -151,7 +151,8 @@ impl Body {
 		// concatenate the header and the body.
 		let mut stream = RlpStream::new_list(3);
 		stream.append_raw(self.header.rlp().as_raw(), 1);
-		stream.append_raw(&body.rlp().as_raw(), 2);
+		stream.append_raw(body.rlp().at(0).as_raw(), 1);
+		stream.append_raw(body.rlp().at(1).as_raw(), 1);
 
 		Ok(encoded::Block::new(stream.out()))
 	}

ethcore/light/src/types/request/mod.rs

@@ -244,7 +244,8 @@ pub enum CompleteRequest {
 }
 
 impl Request {
-	fn kind(&self) -> Kind {
+	/// Get the request kind.
+	pub fn kind(&self) -> Kind {
 		match *self {
 			Request::Headers(_) => Kind::Headers,
 			Request::HeaderProof(_) => Kind::HeaderProof,
@@ -435,7 +436,8 @@ impl Response {
 		}
 	}
 
-	fn kind(&self) -> Kind {
+	/// Inspect the kind of this response.
+	pub fn kind(&self) -> Kind {
 		match *self {
 			Response::Headers(_) => Kind::Headers,
 			Response::HeaderProof(_) => Kind::HeaderProof,
@@ -726,7 +728,6 @@ pub mod header_proof {
 
 	impl Decodable for Response {
 		fn decode(rlp: &UntrustedRlp) -> Result<Self, DecoderError> {
-
 			Ok(Response {
 				proof: rlp.list_at(0)?,
 				hash: rlp.val_at(1)?,
@@ -737,12 +738,10 @@ pub mod header_proof {
 
 	impl Encodable for Response {
 		fn rlp_append(&self, s: &mut RlpStream) {
-			s.begin_list(3).begin_list(self.proof.len());
-			for item in &self.proof {
-				s.append_list(&item);
-			}
-
-			s.append(&self.hash).append(&self.td);
+			s.begin_list(3)
+				.append_list::<Vec<u8>,_>(&self.proof[..])
+				.append(&self.hash)
+				.append(&self.td);
 		}
 	}
 }
@@ -826,7 +825,6 @@ pub mod block_receipts {
 
 	impl Decodable for Response {
 		fn decode(rlp: &UntrustedRlp) -> Result<Self, DecoderError> {
-
 			Ok(Response {
 				receipts: rlp.as_list()?,
 			})
@@ -923,8 +921,8 @@ pub mod block_body {
 			use ethcore::transaction::UnverifiedTransaction;
 
 			// check body validity.
-			let _: Vec<FullHeader> = rlp.list_at(0)?;
-			let _: Vec<UnverifiedTransaction> = rlp.list_at(1)?;
+			let _: Vec<UnverifiedTransaction> = rlp.list_at(0)?;
+			let _: Vec<FullHeader> = rlp.list_at(1)?;
 
 			Ok(Response {
 				body: encoded::Body::new(rlp.as_raw().to_owned()),
@@ -1063,12 +1061,9 @@ pub mod account {
 
 	impl Encodable for Response {
 		fn rlp_append(&self, s: &mut RlpStream) {
-			s.begin_list(5).begin_list(self.proof.len());
-			for item in &self.proof {
-				s.append_list(&item);
-			}
-
-			s.append(&self.nonce)
+			s.begin_list(5)
+				.append_list::<Vec<u8>,_>(&self.proof[..])
+				.append(&self.nonce)
 				.append(&self.balance)
 				.append(&self.code_hash)
 				.append(&self.storage_root);
@@ -1207,11 +1202,9 @@ pub mod storage {
 
 	impl Encodable for Response {
 		fn rlp_append(&self, s: &mut RlpStream) {
-			s.begin_list(2).begin_list(self.proof.len());
-			for item in &self.proof {
-				s.append_list(&item);
-			}
-			s.append(&self.value);
+			s.begin_list(2)
+				.append_list::<Vec<u8>,_>(&self.proof[..])
+				.append(&self.value);
 		}
 	}
 }
@@ -1486,9 +1479,16 @@ mod tests {
 	fn check_roundtrip<T>(val: T)
 		where T: ::rlp::Encodable + ::rlp::Decodable + PartialEq + ::std::fmt::Debug
 	{
+		// check as single value.
 		let bytes = ::rlp::encode(&val);
 		let new_val: T = ::rlp::decode(&bytes);
 		assert_eq!(val, new_val);
+
+		// check as list containing single value.
+		let list = [val];
+		let bytes = ::rlp::encode_list(&list);
+		let new_list: Vec<T> = ::rlp::decode_list(&bytes);
+		assert_eq!(&list, &new_list[..]);
 	}
 
 	#[test]
@@ -1540,7 +1540,7 @@ mod tests {
 
 		let full_req = Request::HeaderProof(req.clone());
 		let res = HeaderProofResponse {
-			proof: Vec::new(),
+			proof: vec![vec![1, 2, 3], vec![4, 5, 6]],
 			hash: Default::default(),
 			td: 100.into(),
 		};
@@ -1572,6 +1572,7 @@ mod tests {
 
 	#[test]
 	fn body_roundtrip() {
+		use ethcore::transaction::{Transaction, UnverifiedTransaction};
 		let req = IncompleteBodyRequest {
 			hash: Field::Scalar(Default::default()),
 		};
@@ -1579,8 +1580,12 @@ mod tests {
 		let full_req = Request::Body(req.clone());
 		let res = BodyResponse {
 			body: {
+				let header = ::ethcore::header::Header::default();
+				let tx = UnverifiedTransaction::from(Transaction::default().fake_sign(Default::default()));
 				let mut stream = RlpStream::new_list(2);
-				stream.begin_list(0).begin_list(0);
+				stream.begin_list(2).append(&tx).append(&tx)
+					.begin_list(1).append(&header);
+
 				::ethcore::encoded::Body::new(stream.out())
 			},
 		};
@@ -1601,7 +1606,7 @@ mod tests {
 
 		let full_req = Request::Account(req.clone());
 		let res = AccountResponse {
-			proof: Vec::new(),
+			proof: vec![vec![1, 2, 3], vec![4, 5, 6]],
 			nonce: 100.into(),
 			balance: 123456.into(),
 			code_hash: Default::default(),
@@ -1625,7 +1630,7 @@ mod tests {
 
 		let full_req = Request::Storage(req.clone());
 		let res = StorageResponse {
-			proof: Vec::new(),
+			proof: vec![vec![1, 2, 3], vec![4, 5, 6]],
 			value: H256::default(),
 		};
 		let full_res = Response::Storage(res.clone());
@@ -1707,4 +1712,31 @@ mod tests {
 		assert_eq!(rlp.val_at::<usize>(0).unwrap(), 100usize);
 		assert_eq!(rlp.list_at::<Request>(1).unwrap(), reqs);
 	}
+
+	#[test]
+	fn responses_vec() {
+		let mut stream = RlpStream::new_list(2);
+				stream.begin_list(0).begin_list(0);
+
+		let body = ::ethcore::encoded::Body::new(stream.out());
+		let reqs = vec![
+			Response::Headers(HeadersResponse { headers: vec![] }),
+			Response::HeaderProof(HeaderProofResponse { proof: vec![], hash: Default::default(), td: 100.into()}),
+			Response::Receipts(ReceiptsResponse { receipts: vec![Default::default()] }),
+			Response::Body(BodyResponse { body: body }),
+			Response::Account(AccountResponse {
+				proof: vec![],
+				nonce: 100.into(),
+				balance: 123.into(),
+				code_hash: Default::default(),
+				storage_root: Default::default()
+			}),
+			Response::Storage(StorageResponse { proof: vec![], value: H256::default() }),
+			Response::Code(CodeResponse { code: vec![1, 2, 3, 4, 5] }),
+			Response::Execution(ExecutionResponse { items: vec![] }),
+		];
+
+		let raw = ::rlp::encode_list(&reqs);
+		assert_eq!(::rlp::decode_list::<Response>(&raw), reqs);
+	}
 }

ethcore/src/client/config.rs

@@ -26,7 +26,7 @@ use verification::{VerifierType, QueueConfig};
 use util::{journaldb, CompactionProfile};
 
 /// Client state db compaction profile
-#[derive(Debug, PartialEq)]
+#[derive(Debug, PartialEq, Clone)]
 pub enum DatabaseCompactionProfile {
 	/// Try to determine compaction profile automatically
 	Auto,

ethcore/src/db.rs

@@ -38,8 +38,10 @@ pub const COL_TRACE: Option<u32> = Some(4);
 pub const COL_ACCOUNT_BLOOM: Option<u32> = Some(5);
 /// Column for general information from the local node which can persist.
 pub const COL_NODE_INFO: Option<u32> = Some(6);
+/// Column for the light client chain.
+pub const COL_LIGHT_CHAIN: Option<u32> = Some(7);
 /// Number of columns in DB
-pub const NUM_COLUMNS: Option<u32> = Some(7);
+pub const NUM_COLUMNS: Option<u32> = Some(8);
 
 /// Modes for updating caches.
 #[derive(Clone, Copy)]

ethcore/src/migrations/mod.rs

@@ -16,6 +16,8 @@
 
 //! Database migrations.
 
+use util::migration::ChangeColumns;
+
 pub mod state;
 pub mod blocks;
 pub mod extras;
@@ -27,5 +29,18 @@ pub use self::v9::Extract;
 mod v10;
 pub use self::v10::ToV10;
 
-mod v11;
-pub use self::v11::TO_V11;
+/// The migration from v10 to v11.
+/// Adds a column for node info.
+pub const TO_V11: ChangeColumns = ChangeColumns {
+	pre_columns: Some(6),
+	post_columns: Some(7),
+	version: 11,
+};
+
+/// The migration from v11 to v12.
+/// Adds a column for light chain storage.
+pub const TO_V12: ChangeColumns = ChangeColumns {
+	pre_columns: Some(7),
+	post_columns: Some(8),
+	version: 12,
+};

parity/cli/config.full.toml

@@ -39,7 +39,7 @@ warp = true
 allow_ips = "all"
 snapshot_peers = 0
 max_pending_peers = 64
-serve_light = true
+no_serve_light = false
 
 reserved_only = false
 reserved_peers = "./path_to_file"

parity/cli/mod.rs

@@ -94,6 +94,7 @@ usage! {
 		flag_chain: String = "foundation", or |c: &Config| otry!(c.parity).chain.clone(),
 		flag_keys_path: String = "$BASE/keys", or |c: &Config| otry!(c.parity).keys_path.clone(),
 		flag_identity: String = "", or |c: &Config| otry!(c.parity).identity.clone(),
+		flag_light: bool = false, or |c: &Config| otry!(c.parity).light,
 
 		// -- Account Options
 		flag_unlock: Option<String> = None,
@@ -149,6 +150,8 @@ usage! {
 		flag_reserved_only: bool = false,
 			or |c: &Config| otry!(c.network).reserved_only.clone(),
 		flag_no_ancient_blocks: bool = false, or |_| None,
+		flag_no_serve_light: bool = false,
+			or |c: &Config| otry!(c.network).no_serve_light.clone(),
 
 		// -- API and Console Options
 		// RPC
@@ -379,6 +382,7 @@ struct Operating {
 	db_path: Option<String>,
 	keys_path: Option<String>,
 	identity: Option<String>,
+	light: Option<bool>,
 }
 
 #[derive(Default, Debug, PartialEq, RustcDecodable)]
@@ -414,6 +418,7 @@ struct Network {
 	node_key: Option<String>,
 	reserved_peers: Option<String>,
 	reserved_only: Option<bool>,
+	no_serve_light: Option<bool>,
 }
 
 #[derive(Default, Debug, PartialEq, RustcDecodable)]
@@ -639,6 +644,7 @@ mod tests {
 			flag_db_path: Some("$HOME/.parity/chains".into()),
 			flag_keys_path: "$HOME/.parity/keys".into(),
 			flag_identity: "".into(),
+			flag_light: false,
 
 			// -- Account Options
 			flag_unlock: Some("0xdeadbeefcafe0000000000000000000000000000".into()),
@@ -669,6 +675,7 @@ mod tests {
 			flag_reserved_peers: Some("./path_to_file".into()),
 			flag_reserved_only: false,
 			flag_no_ancient_blocks: false,
+			flag_no_serve_light: false,
 
 			// -- API and Console Options
 			// RPC
@@ -844,6 +851,7 @@ mod tests {
 				db_path: None,
 				keys_path: None,
 				identity: None,
+				light: None,
 			}),
 			account: Some(Account {
 				unlock: Some(vec!["0x1".into(), "0x2".into(), "0x3".into()]),
@@ -873,6 +881,7 @@ mod tests {
 				node_key: None,
 				reserved_peers: Some("./path/to/reserved_peers".into()),
 				reserved_only: Some(true),
+				no_serve_light: None,
 			}),
 			rpc: Some(Rpc {
 				disable: Some(true),

parity/cli/usage.txt

@@ -70,6 +70,11 @@ Operating Options:
   --keys-path PATH               Specify the path for JSON key files to be found
                                  (default: {flag_keys_path}).
   --identity NAME                Specify your node's name. (default: {flag_identity})
+  --light                        Experimental: run in light client mode. Light clients
+                                 synchronize a bare minimum of data and fetch necessary
+                                 data on-demand from the network. Much lower in storage,
+                                 potentially higher in bandwidth. Has no effect with
+                                 subcommands (default: {flag_light}).
 
 Account Options:
   --unlock ACCOUNTS              Unlock ACCOUNTS for the duration of the execution.
@@ -129,6 +134,7 @@ Networking Options:
   --max-pending-peers NUM        Allow up to NUM pending connections. (default: {flag_max_pending_peers})
   --no-ancient-blocks            Disable downloading old blocks after snapshot restoration
                                  or warp sync. (default: {flag_no_ancient_blocks})
+  --no-serve-light               Disable serving of light peers. (default: {flag_no_serve_light})
 
 API and Console Options:
   --no-jsonrpc                   Disable the JSON-RPC API server. (default: {flag_no_jsonrpc})

parity/configuration.rs

@@ -382,6 +382,8 @@ impl Configuration {
 				check_seal: !self.args.flag_no_seal_check,
 				download_old_blocks: !self.args.flag_no_ancient_blocks,
 				verifier_settings: verifier_settings,
+				serve_light: !self.args.flag_no_serve_light,
+				light: self.args.flag_light,
 			};
 			Cmd::Run(run_cmd)
 		};
@@ -1201,6 +1203,8 @@ mod tests {
 			check_seal: true,
 			download_old_blocks: true,
 			verifier_settings: Default::default(),
+			serve_light: true,
+			light: false,
 		};
 		expected.secretstore_conf.enabled = cfg!(feature = "secretstore");
 		assert_eq!(conf.into_command().unwrap().cmd, Cmd::Run(expected));

parity/dapps.rs

@@ -18,12 +18,14 @@ use std::path::PathBuf;
 use std::sync::Arc;
 
 use dir::default_data_path;
-use ethcore::client::Client;
-use ethsync::SyncProvider;
+use ethcore::client::{Client, BlockChainClient, BlockId};
+use ethcore::transaction::{Transaction, Action};
 use hash_fetch::fetch::Client as FetchClient;
+use hash_fetch::urlhint::ContractClient;
 use helpers::replace_home;
 use rpc_apis::SignerService;
 use parity_reactor;
+use util::{Bytes, Address, U256};
 
 #[derive(Debug, PartialEq, Clone)]
 pub struct Configuration {
@@ -43,15 +45,53 @@ impl Default for Configuration {
 	}
 }
 
-pub struct Dependencies {
+/// Registrar implementation of the full client.
+pub struct FullRegistrar {
+	/// Handle to the full client.
 	pub client: Arc<Client>,
-	pub sync: Arc<SyncProvider>,
+}
+
+impl ContractClient for FullRegistrar {
+	fn registrar(&self) -> Result<Address, String> {
+		self.client.additional_params().get("registrar")
+			 .ok_or_else(|| "Registrar not defined.".into())
+			 .and_then(|registrar| {
+				 registrar.parse().map_err(|e| format!("Invalid registrar address: {:?}", e))
+			 })
+	}
+
+	fn call(&self, address: Address, data: Bytes) -> Result<Bytes, String> {
+		let from = Address::default();
+		let transaction = Transaction {
+			nonce: self.client.latest_nonce(&from),
+			action: Action::Call(address),
+			gas: U256::from(50_000_000),
+			gas_price: U256::default(),
+			value: U256::default(),
+			data: data,
+		}.fake_sign(from);
+
+		self.client.call(&transaction, BlockId::Latest, Default::default())
+			.map_err(|e| format!("{:?}", e))
+			.map(|executed| {
+				executed.output
+			})
+	}
+}
+
+// TODO: light client implementation forwarding to OnDemand and waiting for future
+// to resolve.
+pub struct Dependencies {
+	pub sync_status: Arc<::parity_dapps::SyncStatus>,
+	pub contract_client: Arc<ContractClient>,
 	pub remote: parity_reactor::TokioRemote,
 	pub fetch: FetchClient,
 	pub signer: Arc<SignerService>,
 }
 
-pub fn new(configuration: Configuration, deps: Dependencies) -> Result<Option<Middleware>, String> {
+pub fn new(configuration: Configuration, deps: Dependencies)
+	-> Result<Option<Middleware>, String>
+{
 	if !configuration.enabled {
 		return Ok(None);
 	}
@@ -96,13 +136,8 @@ mod server {
 	use super::Dependencies;
 	use std::path::PathBuf;
 	use std::sync::Arc;
-	use util::{Bytes, Address, U256};
 
-	use ethcore::transaction::{Transaction, Action};
-	use ethcore::client::{Client, BlockChainClient, BlockId};
-	use ethcore_rpc::is_major_importing;
 	use hash_fetch::fetch::Client as FetchClient;
-	use hash_fetch::urlhint::ContractClient;
 	use parity_dapps;
 	use parity_reactor;
 
@@ -113,12 +148,8 @@ mod server {
 		dapps_path: PathBuf,
 		extra_dapps: Vec<PathBuf>,
 	) -> Result<Middleware, String> {
-		let sync = deps.sync;
 		let signer = deps.signer.clone();
-		let client = deps.client;
 		let parity_remote = parity_reactor::Remote::new(deps.remote.clone());
-		let registrar = Arc::new(Registrar { client: client.clone() });
-		let sync_status = Arc::new(move || is_major_importing(Some(sync.status().state), client.queue_info()));
 		let web_proxy_tokens = Arc::new(move |token| signer.is_valid_web_proxy_access_token(&token));
 
 		Ok(parity_dapps::Middleware::new(
@@ -126,42 +157,10 @@ mod server {
 			deps.signer.address(),
 			dapps_path,
 			extra_dapps,
-			registrar,
-			sync_status,
+			deps.contract_client,
+			deps.sync_status,
 			web_proxy_tokens,
 			deps.fetch.clone(),
 		))
 	}
-
-	struct Registrar {
-		client: Arc<Client>,
-	}
-
-	impl ContractClient for Registrar {
-		fn registrar(&self) -> Result<Address, String> {
-			self.client.additional_params().get("registrar")
-				 .ok_or_else(|| "Registrar not defined.".into())
-				 .and_then(|registrar| {
-					 registrar.parse().map_err(|e| format!("Invalid registrar address: {:?}", e))
-				 })
-		}
-
-		fn call(&self, address: Address, data: Bytes) -> Result<Bytes, String> {
-			let from = Address::default();
-			let transaction = Transaction {
-				nonce: self.client.latest_nonce(&from),
-				action: Action::Call(address),
-				gas: U256::from(50_000_000),
-				gas_price: U256::default(),
-				value: U256::default(),
-				data: data,
-			}.fake_sign(from);
-
-			self.client.call(&transaction, BlockId::Latest, Default::default())
-				.map_err(|e| format!("{:?}", e))
-				.map(|executed| {
-					executed.output
-				})
-		}
-	}
 }

parity/light_helpers/mod.rs

@@ -14,13 +14,8 @@
 // You should have received a copy of the GNU General Public License
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.
 
-//! Adds a seventh column for node information.
+//! Utilities and helpers for the light client.
 
-use util::migration::ChangeColumns;
+mod queue_cull;
 
-/// The migration from v10 to v11.
-pub const TO_V11: ChangeColumns = ChangeColumns {
-	pre_columns: Some(6),
-	post_columns: Some(7),
-	version: 11,
-};
+pub use self::queue_cull::QueueCull;

parity/light_helpers/queue_cull.rs

@@ -0,0 +1,99 @@
+// 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/>.
+
+//! Service for culling the light client's transaction queue.
+
+use std::sync::Arc;
+use std::time::Duration;
+
+use ethcore::service::ClientIoMessage;
+use ethsync::LightSync;
+use io::{IoContext, IoHandler, TimerToken};
+
+use light::client::Client;
+use light::on_demand::{request, OnDemand};
+use light::TransactionQueue;
+
+use futures::{future, stream, Future, Stream};
+
+use parity_reactor::Remote;
+
+use util::RwLock;
+
+// Attepmt to cull once every 10 minutes.
+const TOKEN: TimerToken = 1;
+const TIMEOUT_MS: u64 = 1000 * 60 * 10;
+
+// But make each attempt last only 9 minutes
+const PURGE_TIMEOUT_MS: u64 = 1000 * 60 * 9;
+
+/// Periodically culls the transaction queue of mined transactions.
+pub struct QueueCull {
+	/// A handle to the client, for getting the latest block header.
+	pub client: Arc<Client>,
+	/// A handle to the sync service.
+	pub sync: Arc<LightSync>,
+	/// The on-demand request service.
+	pub on_demand: Arc<OnDemand>,
+	/// The transaction queue.
+	pub txq: Arc<RwLock<TransactionQueue>>,
+	/// Event loop remote.
+	pub remote: Remote,
+}
+
+impl IoHandler<ClientIoMessage> for QueueCull {
+	fn initialize(&self, io: &IoContext<ClientIoMessage>) {
+		io.register_timer(TOKEN, TIMEOUT_MS).expect("Error registering timer");
+	}
+
+	fn timeout(&self, _io: &IoContext<ClientIoMessage>, timer: TimerToken) {
+		if timer != TOKEN { return }
+
+		let senders = self.txq.read().queued_senders();
+		if senders.is_empty() { return }
+
+		let (sync, on_demand, txq) = (self.sync.clone(), self.on_demand.clone(), self.txq.clone());
+		let best_header = self.client.best_block_header();
+		let start_nonce = self.client.engine().account_start_nonce();
+
+		info!(target: "cull", "Attempting to cull queued transactions from {} senders.", senders.len());
+		self.remote.spawn_with_timeout(move || {
+			let maybe_fetching = sync.with_context(move |ctx| {
+				// fetch the nonce of each sender in the queue.
+				let nonce_futures = senders.iter()
+					.map(|&address| request::Account { header: best_header.clone(), address: address })
+					.map(|request| on_demand.account(ctx, request))
+					.map(move |fut| fut.map(move |x| x.map(|acc| acc.nonce).unwrap_or(start_nonce)))
+					.zip(senders.iter())
+					.map(|(fut, &addr)| fut.map(move |nonce| (addr, nonce)));
+
+				// as they come in, update each sender to the new nonce.
+				stream::futures_unordered(nonce_futures)
+					.fold(txq, |txq, (address, nonce)| {
+						txq.write().cull(address, nonce);
+						future::ok(txq)
+					})
+					.map(|_| ()) // finally, discard the txq handle and log errors.
+					.map_err(|_| debug!(target: "cull", "OnDemand prematurely closed channel."))
+			});
+
+			match maybe_fetching {
+				Some(fut) => fut.boxed(),
+				None => future::ok(()).boxed(),
+			}
+		}, Duration::from_millis(PURGE_TIMEOUT_MS), || {})
+	}
+}

parity/main.rs

@@ -28,6 +28,7 @@ extern crate ctrlc;
 extern crate docopt;
 extern crate env_logger;
 extern crate fdlimit;
+extern crate futures;
 extern crate isatty;
 extern crate jsonrpc_core;
 extern crate num_cpus;
@@ -105,6 +106,7 @@ mod deprecated;
 mod dir;
 mod helpers;
 mod informant;
+mod light_helpers;
 mod migration;
 mod modules;
 mod params;

parity/migration.rs

@@ -30,7 +30,7 @@ use ethcore::migrations::Extract;
 /// Database is assumed to be at default version, when no version file is found.
 const DEFAULT_VERSION: u32 = 5;
 /// Current version of database models.
-const CURRENT_VERSION: u32 = 11;
+const CURRENT_VERSION: u32 = 12;
 /// First version of the consolidated database.
 const CONSOLIDATION_VERSION: u32 = 9;
 /// Defines how many items are migrated to the new version of database at once.
@@ -147,6 +147,7 @@ fn consolidated_database_migrations(compaction_profile: &CompactionProfile) -> R
 	let mut manager = MigrationManager::new(default_migration_settings(compaction_profile));
 	manager.add_migration(migrations::ToV10::new()).map_err(|_| Error::MigrationImpossible)?;
 	manager.add_migration(migrations::TO_V11).map_err(|_| Error::MigrationImpossible)?;
+	manager.add_migration(migrations::TO_V12).map_err(|_| Error::MigrationImpossible)?;
 	Ok(manager)
 }
 

parity/rpc.rs

@@ -81,8 +81,8 @@ impl fmt::Display for IpcConfiguration {
 	}
 }
 
-pub struct Dependencies {
-	pub apis: Arc<rpc_apis::Dependencies>,
+pub struct Dependencies<D: rpc_apis::Dependencies> {
+	pub apis: Arc<D>,
 	pub remote: TokioRemote,
 	pub stats: Arc<RpcStats>,
 }
@@ -112,11 +112,17 @@ impl rpc::IpcMetaExtractor<Metadata> for RpcExtractor {
 	}
 }
 
-fn setup_apis(apis: ApiSet, deps: &Dependencies) -> MetaIoHandler<Metadata, Middleware> {
-	rpc_apis::setup_rpc(deps.stats.clone(), deps.apis.clone(), apis)
+fn setup_apis<D>(apis: ApiSet, deps: &Dependencies<D>) -> MetaIoHandler<Metadata, Middleware<D::Notifier>>
+	where D: rpc_apis::Dependencies
+{
+	rpc_apis::setup_rpc(deps.stats.clone(), &*deps.apis, apis)
 }
 
-pub fn new_http(conf: HttpConfiguration, deps: &Dependencies, middleware: Option<dapps::Middleware>) -> Result<Option<HttpServer>, String> {
+pub fn new_http<D: rpc_apis::Dependencies>(
+	conf: HttpConfiguration,
+	deps: &Dependencies<D>,
+	middleware: Option<dapps::Middleware>
+) -> Result<Option<HttpServer>, String> {
 	if !conf.enabled {
 		return Ok(None);
 	}
@@ -157,7 +163,10 @@ pub fn new_http(conf: HttpConfiguration, deps: &Dependencies, middleware: Option
 	}
 }
 
-pub fn new_ipc(conf: IpcConfiguration, dependencies: &Dependencies) -> Result<Option<IpcServer>, String> {
+pub fn new_ipc<D: rpc_apis::Dependencies>(
+	conf: IpcConfiguration,
+	dependencies: &Dependencies<D>
+) -> Result<Option<IpcServer>, String> {
 	if !conf.enabled {
 		return Ok(None);
 	}

parity/rpc_apis.rs

@@ -27,12 +27,14 @@ use ethcore::client::Client;
 use ethcore::miner::{Miner, ExternalMiner};
 use ethcore::snapshot::SnapshotService;
 use ethcore_rpc::{Metadata, NetworkSettings};
-use ethcore_rpc::informant::{Middleware, RpcStats, ClientNotifier};
-use ethcore_rpc::dispatch::FullDispatcher;
-use ethsync::{ManageNetwork, SyncProvider};
+use ethcore_rpc::informant::{ActivityNotifier, Middleware, RpcStats, ClientNotifier};
+use ethcore_rpc::dispatch::{FullDispatcher, LightDispatcher};
+use ethsync::{ManageNetwork, SyncProvider, LightSync};
 use hash_fetch::fetch::Client as FetchClient;
 use jsonrpc_core::{MetaIoHandler};
+use light::{TransactionQueue as LightTransactionQueue, Cache as LightDataCache};
 use updater::Updater;
+use util::{Mutex, RwLock};
 use ethcore_logger::RotatingLogger;
 
 #[derive(Debug, PartialEq, Clone, Eq, Hash)]
@@ -112,25 +114,6 @@ impl FromStr for ApiSet {
 	}
 }
 
-pub struct Dependencies {
-	pub signer_service: Arc<SignerService>,
-	pub client: Arc<Client>,
-	pub snapshot: Arc<SnapshotService>,
-	pub sync: Arc<SyncProvider>,
-	pub net: Arc<ManageNetwork>,
-	pub secret_store: Option<Arc<AccountProvider>>,
-	pub miner: Arc<Miner>,
-	pub external_miner: Arc<ExternalMiner>,
-	pub logger: Arc<RotatingLogger>,
-	pub settings: Arc<NetworkSettings>,
-	pub net_service: Arc<ManageNetwork>,
-	pub updater: Arc<Updater>,
-	pub geth_compatibility: bool,
-	pub dapps_interface: Option<String>,
-	pub dapps_port: Option<u16>,
-	pub fetch: FetchClient,
-}
-
 fn to_modules(apis: &[Api]) -> BTreeMap<String, String> {
 	let mut modules = BTreeMap::new();
 	for api in apis {
@@ -151,6 +134,274 @@ fn to_modules(apis: &[Api]) -> BTreeMap<String, String> {
 	modules
 }
 
+/// RPC dependencies can be used to initialize RPC endpoints from APIs.
+pub trait Dependencies {
+	type Notifier: ActivityNotifier;
+
+	/// Create the activity notifier.
+	fn activity_notifier(&self) -> Self::Notifier;
+
+	/// Extend the given I/O handler with endpoints for each API.
+	fn extend_with_set(&self, handler: &mut MetaIoHandler<Metadata, Middleware<Self::Notifier>>, apis: &[Api]);
+}
+
+/// RPC dependencies for a full node.
+pub struct FullDependencies {
+	pub signer_service: Arc<SignerService>,
+	pub client: Arc<Client>,
+	pub snapshot: Arc<SnapshotService>,
+	pub sync: Arc<SyncProvider>,
+	pub net: Arc<ManageNetwork>,
+	pub secret_store: Option<Arc<AccountProvider>>,
+	pub miner: Arc<Miner>,
+	pub external_miner: Arc<ExternalMiner>,
+	pub logger: Arc<RotatingLogger>,
+	pub settings: Arc<NetworkSettings>,
+	pub net_service: Arc<ManageNetwork>,
+	pub updater: Arc<Updater>,
+	pub geth_compatibility: bool,
+	pub dapps_interface: Option<String>,
+	pub dapps_port: Option<u16>,
+	pub fetch: FetchClient,
+}
+
+impl Dependencies for FullDependencies {
+	type Notifier = ClientNotifier;
+
+	fn activity_notifier(&self) -> ClientNotifier {
+		ClientNotifier {
+			client: self.client.clone(),
+		}
+	}
+
+	fn extend_with_set(&self, handler: &mut MetaIoHandler<Metadata, Middleware>, apis: &[Api]) {
+		use ethcore_rpc::v1::*;
+
+		macro_rules! add_signing_methods {
+			($namespace:ident, $handler:expr, $deps:expr) => {
+				{
+					let deps = &$deps;
+					let dispatcher = FullDispatcher::new(Arc::downgrade(&deps.client), Arc::downgrade(&deps.miner));
+					if deps.signer_service.is_enabled() {
+						$handler.extend_with($namespace::to_delegate(SigningQueueClient::new(&deps.signer_service, dispatcher, &deps.secret_store)))
+					} else {
+						$handler.extend_with($namespace::to_delegate(SigningUnsafeClient::new(&deps.secret_store, dispatcher)))
+					}
+				}
+			}
+		}
+
+		let dispatcher = FullDispatcher::new(Arc::downgrade(&self.client), Arc::downgrade(&self.miner));
+		for api in apis {
+			match *api {
+				Api::Web3 => {
+					handler.extend_with(Web3Client::new().to_delegate());
+				},
+				Api::Net => {
+					handler.extend_with(NetClient::new(&self.sync).to_delegate());
+				},
+				Api::Eth => {
+					let client = EthClient::new(
+						&self.client,
+						&self.snapshot,
+						&self.sync,
+						&self.secret_store,
+						&self.miner,
+						&self.external_miner,
+						EthClientOptions {
+							pending_nonce_from_queue: self.geth_compatibility,
+							allow_pending_receipt_query: !self.geth_compatibility,
+							send_block_number_in_get_work: !self.geth_compatibility,
+						}
+					);
+					handler.extend_with(client.to_delegate());
+
+					let filter_client = EthFilterClient::new(&self.client, &self.miner);
+					handler.extend_with(filter_client.to_delegate());
+
+					add_signing_methods!(EthSigning, handler, self);
+				},
+				Api::Personal => {
+					handler.extend_with(PersonalClient::new(&self.secret_store, dispatcher.clone(), self.geth_compatibility).to_delegate());
+				},
+				Api::Signer => {
+					handler.extend_with(SignerClient::new(&self.secret_store, dispatcher.clone(), &self.signer_service).to_delegate());
+				},
+				Api::Parity => {
+					let signer = match self.signer_service.is_enabled() {
+						true => Some(self.signer_service.clone()),
+						false => None,
+					};
+					handler.extend_with(ParityClient::new(
+						&self.client,
+						&self.miner,
+						&self.sync,
+						&self.updater,
+						&self.net_service,
+						&self.secret_store,
+						self.logger.clone(),
+						self.settings.clone(),
+						signer,
+						self.dapps_interface.clone(),
+						self.dapps_port,
+					).to_delegate());
+
+					add_signing_methods!(EthSigning, handler, self);
+					add_signing_methods!(ParitySigning, handler, self);
+				},
+				Api::ParityAccounts => {
+					handler.extend_with(ParityAccountsClient::new(&self.secret_store).to_delegate());
+				},
+				Api::ParitySet => {
+					handler.extend_with(ParitySetClient::new(
+						&self.client,
+						&self.miner,
+						&self.updater,
+						&self.net_service,
+						self.fetch.clone(),
+					).to_delegate())
+				},
+				Api::Traces => {
+					handler.extend_with(TracesClient::new(&self.client, &self.miner).to_delegate())
+				},
+				Api::Rpc => {
+					let modules = to_modules(&apis);
+					handler.extend_with(RpcClient::new(modules).to_delegate());
+				}
+			}
+		}
+	}
+}
+
+/// Light client notifier. Doesn't do anything yet, but might in the future.
+pub struct LightClientNotifier;
+
+impl ActivityNotifier for LightClientNotifier {
+	fn active(&self) {}
+}
+
+/// RPC dependencies for a light client.
+pub struct LightDependencies {
+	pub signer_service: Arc<SignerService>,
+	pub client: Arc<::light::client::Client>,
+	pub sync: Arc<LightSync>,
+	pub net: Arc<ManageNetwork>,
+	pub secret_store: Arc<AccountProvider>,
+	pub logger: Arc<RotatingLogger>,
+	pub settings: Arc<NetworkSettings>,
+	pub on_demand: Arc<::light::on_demand::OnDemand>,
+	pub cache: Arc<Mutex<LightDataCache>>,
+	pub transaction_queue: Arc<RwLock<LightTransactionQueue>>,
+	pub dapps_interface: Option<String>,
+	pub dapps_port: Option<u16>,
+	pub fetch: FetchClient,
+	pub geth_compatibility: bool,
+}
+
+impl Dependencies for LightDependencies {
+	type Notifier = LightClientNotifier;
+
+	fn activity_notifier(&self) -> Self::Notifier { LightClientNotifier }
+	fn extend_with_set(&self, handler: &mut MetaIoHandler<Metadata, Middleware<Self::Notifier>>, apis: &[Api]) {
+		use ethcore_rpc::v1::*;
+
+		let dispatcher = LightDispatcher::new(
+			self.sync.clone(),
+			self.client.clone(),
+			self.on_demand.clone(),
+			self.cache.clone(),
+			self.transaction_queue.clone(),
+		);
+
+		macro_rules! add_signing_methods {
+			($namespace:ident, $handler:expr, $deps:expr) => {
+				{
+					let deps = &$deps;
+					let dispatcher = dispatcher.clone();
+					let secret_store = Some(deps.secret_store.clone());
+					if deps.signer_service.is_enabled() {
+						$handler.extend_with($namespace::to_delegate(
+							SigningQueueClient::new(&deps.signer_service, dispatcher, &secret_store)
+						))
+					} else {
+						$handler.extend_with(
+							$namespace::to_delegate(SigningUnsafeClient::new(&secret_store, dispatcher))
+						)
+					}
+				}
+			}
+		}
+
+		for api in apis {
+			match *api {
+				Api::Web3 => {
+					handler.extend_with(Web3Client::new().to_delegate());
+				},
+				Api::Net => {
+					handler.extend_with(light::NetClient::new(self.sync.clone()).to_delegate());
+				},
+				Api::Eth => {
+					let client = light::EthClient::new(
+						self.sync.clone(),
+						self.client.clone(),
+						self.on_demand.clone(),
+						self.transaction_queue.clone(),
+						self.secret_store.clone(),
+						self.cache.clone(),
+					);
+					handler.extend_with(client.to_delegate());
+
+					// TODO: filters.
+					add_signing_methods!(EthSigning, handler, self);
+				},
+				Api::Personal => {
+					let secret_store = Some(self.secret_store.clone());
+					handler.extend_with(PersonalClient::new(&secret_store, dispatcher.clone(), self.geth_compatibility).to_delegate());
+				},
+				Api::Signer => {
+					let secret_store = Some(self.secret_store.clone());
+					handler.extend_with(SignerClient::new(&secret_store, dispatcher.clone(), &self.signer_service).to_delegate());
+				},
+				Api::Parity => {
+					let signer = match self.signer_service.is_enabled() {
+						true => Some(self.signer_service.clone()),
+						false => None,
+					};
+					handler.extend_with(light::ParityClient::new(
+						Arc::new(dispatcher.clone()),
+						self.secret_store.clone(),
+						self.logger.clone(),
+						self.settings.clone(),
+						signer,
+						self.dapps_interface.clone(),
+						self.dapps_port,
+					).to_delegate());
+
+					add_signing_methods!(EthSigning, handler, self);
+					add_signing_methods!(ParitySigning, handler, self);
+				},
+				Api::ParityAccounts => {
+					let secret_store = Some(self.secret_store.clone());
+					handler.extend_with(ParityAccountsClient::new(&secret_store).to_delegate());
+				},
+				Api::ParitySet => {
+					handler.extend_with(light::ParitySetClient::new(
+						self.sync.clone(),
+						self.fetch.clone(),
+					).to_delegate())
+				},
+				Api::Traces => {
+					handler.extend_with(light::TracesClient.to_delegate())
+				},
+				Api::Rpc => {
+					let modules = to_modules(&apis);
+					handler.extend_with(RpcClient::new(modules).to_delegate());
+				}
+			}
+		}
+	}
+}
+
 impl ApiSet {
 	pub fn list_apis(&self) -> HashSet<Api> {
 		let mut safe_list = vec![Api::Web3, Api::Net, Api::Eth, Api::Parity, Api::Traces, Api::Rpc]
@@ -172,110 +423,12 @@ impl ApiSet {
 	}
 }
 
-macro_rules! add_signing_methods {
-	($namespace:ident, $handler:expr, $deps:expr) => {
-		{
-			let handler = &mut $handler;
-			let deps = &$deps;
-			let dispatcher = FullDispatcher::new(Arc::downgrade(&deps.client), Arc::downgrade(&deps.miner));
-			if deps.signer_service.is_enabled() {
-				handler.extend_with($namespace::to_delegate(SigningQueueClient::new(&deps.signer_service, dispatcher, &deps.secret_store)))
-			} else {
-				handler.extend_with($namespace::to_delegate(SigningUnsafeClient::new(&deps.secret_store, dispatcher)))
-			}
-		}
-	}
-}
-
-pub fn setup_rpc(stats: Arc<RpcStats>, deps: Arc<Dependencies>, apis: ApiSet) -> MetaIoHandler<Metadata, Middleware> {
-	use ethcore_rpc::v1::*;
-
-	let mut handler = MetaIoHandler::with_middleware(Middleware::new(stats, ClientNotifier {
-		client: deps.client.clone(),
-	}));
-
+pub fn setup_rpc<D: Dependencies>(stats: Arc<RpcStats>, deps: &D, apis: ApiSet) -> MetaIoHandler<Metadata, Middleware<D::Notifier>> {
+	let mut handler = MetaIoHandler::with_middleware(Middleware::new(stats, deps.activity_notifier()));
 	// it's turned into vector, cause ont of the cases requires &[]
 	let apis = apis.list_apis().into_iter().collect::<Vec<_>>();
-	let dispatcher = FullDispatcher::new(Arc::downgrade(&deps.client), Arc::downgrade(&deps.miner));
+	deps.extend_with_set(&mut handler, &apis[..]);
 
-	for api in &apis {
-		match *api {
-			Api::Web3 => {
-				handler.extend_with(Web3Client::new().to_delegate());
-			},
-			Api::Net => {
-				handler.extend_with(NetClient::new(&deps.sync).to_delegate());
-			},
-			Api::Eth => {
-				let client = EthClient::new(
-					&deps.client,
-					&deps.snapshot,
-					&deps.sync,
-					&deps.secret_store,
-					&deps.miner,
-					&deps.external_miner,
-					EthClientOptions {
-						pending_nonce_from_queue: deps.geth_compatibility,
-						allow_pending_receipt_query: !deps.geth_compatibility,
-						send_block_number_in_get_work: !deps.geth_compatibility,
-					}
-				);
-				handler.extend_with(client.to_delegate());
-
-				let filter_client = EthFilterClient::new(&deps.client, &deps.miner);
-				handler.extend_with(filter_client.to_delegate());
-
-				add_signing_methods!(EthSigning, handler, deps);
-			},
-			Api::Personal => {
-				handler.extend_with(PersonalClient::new(&deps.secret_store, dispatcher.clone(), deps.geth_compatibility).to_delegate());
-			},
-			Api::Signer => {
-				handler.extend_with(SignerClient::new(&deps.secret_store, dispatcher.clone(), &deps.signer_service).to_delegate());
-			},
-			Api::Parity => {
-				let signer = match deps.signer_service.is_enabled() {
-					true => Some(deps.signer_service.clone()),
-					false => None,
-				};
-				handler.extend_with(ParityClient::new(
-					&deps.client,
-					&deps.miner,
-					&deps.sync,
-					&deps.updater,
-					&deps.net_service,
-					&deps.secret_store,
-					deps.logger.clone(),
-					deps.settings.clone(),
-					signer,
-					deps.dapps_interface.clone(),
-					deps.dapps_port,
-				).to_delegate());
-
-				add_signing_methods!(EthSigning, handler, deps);
-				add_signing_methods!(ParitySigning, handler, deps);
-			},
-			Api::ParityAccounts => {
-				handler.extend_with(ParityAccountsClient::new(&deps.secret_store).to_delegate());
-			},
-			Api::ParitySet => {
-				handler.extend_with(ParitySetClient::new(
-					&deps.client,
-					&deps.miner,
-					&deps.updater,
-					&deps.net_service,
-					deps.fetch.clone(),
-				).to_delegate())
-			},
-			Api::Traces => {
-				handler.extend_with(TracesClient::new(&deps.client, &deps.miner).to_delegate())
-			},
-			Api::Rpc => {
-				let modules = to_modules(&apis);
-				handler.extend_with(RpcClient::new(modules).to_delegate());
-			}
-		}
-	}
 	handler
 }
 

parity/run.rs

@@ -30,6 +30,7 @@ use ethcore::account_provider::{AccountProvider, AccountProviderSettings};
 use ethcore::miner::{Miner, MinerService, ExternalMiner, MinerOptions};
 use ethcore::snapshot;
 use ethcore::verification::queue::VerifierSettings;
+use light::Cache as LightDataCache;
 use ethsync::SyncConfig;
 use informant::Informant;
 use updater::{UpdatePolicy, Updater};
@@ -60,6 +61,10 @@ const SNAPSHOT_PERIOD: u64 = 10000;
 // how many blocks to wait before starting a periodic snapshot.
 const SNAPSHOT_HISTORY: u64 = 100;
 
+// Number of minutes before a given gas price corpus should expire.
+// Light client only.
+const GAS_CORPUS_EXPIRATION_MINUTES: i64 = 60 * 6;
+
 // Pops along with error messages when a password is missing or invalid.
 const VERIFY_PASSWORD_HINT: &'static str = "Make sure valid password is present in files passed using `--password` or in the configuration file.";
 
@@ -107,6 +112,8 @@ pub struct RunCmd {
 	pub check_seal: bool,
 	pub download_old_blocks: bool,
 	pub verifier_settings: VerifierSettings,
+	pub serve_light: bool,
+	pub light: bool,
 }
 
 pub fn open_ui(signer_conf: &signer::Configuration) -> Result<(), String> {
@@ -148,6 +155,171 @@ impl ::local_store::NodeInfo for FullNodeInfo {
 	}
 }
 
+// helper for light execution.
+fn execute_light(cmd: RunCmd, can_restart: bool, logger: Arc<RotatingLogger>) -> Result<(bool, Option<String>), String> {
+	use light::client as light_client;
+	use ethsync::{LightSyncParams, LightSync, ManageNetwork};
+	use util::RwLock;
+
+	let panic_handler = PanicHandler::new_in_arc();
+
+	// load spec
+	let spec = cmd.spec.spec()?;
+
+	// load genesis hash
+	let genesis_hash = spec.genesis_header().hash();
+
+	// database paths
+	let db_dirs = cmd.dirs.database(genesis_hash, cmd.spec.legacy_fork_name(), spec.data_dir.clone());
+
+	// user defaults path
+	let user_defaults_path = db_dirs.user_defaults_path();
+
+	// load user defaults
+	let user_defaults = UserDefaults::load(&user_defaults_path)?;
+
+	// select pruning algorithm
+	let algorithm = cmd.pruning.to_algorithm(&user_defaults);
+
+	let compaction = cmd.compaction.compaction_profile(db_dirs.db_root_path().as_path());
+
+	// execute upgrades
+	execute_upgrades(&cmd.dirs.base, &db_dirs, algorithm, compaction.clone())?;
+
+	// create dirs used by parity
+	cmd.dirs.create_dirs(cmd.dapps_conf.enabled, cmd.signer_conf.enabled, cmd.secretstore_conf.enabled)?;
+
+	info!("Starting {}", Colour::White.bold().paint(version()));
+	info!("Running in experimental {} mode.", Colour::Blue.bold().paint("Light Client"));
+
+	// start client and create transaction queue.
+	let mut config = light_client::Config {
+		queue: Default::default(),
+		chain_column: ::ethcore::db::COL_LIGHT_CHAIN,
+		db_cache_size: Some(cmd.cache_config.blockchain() as usize * 1024 * 1024),
+		db_compaction: compaction,
+		db_wal: cmd.wal,
+	};
+
+	config.queue.max_mem_use = cmd.cache_config.queue() as usize * 1024 * 1024;
+	config.queue.verifier_settings = cmd.verifier_settings;
+
+	let service = light_client::Service::start(config, &spec, &db_dirs.client_path(algorithm))
+		.map_err(|e| format!("Error starting light client: {}", e))?;
+	let txq = Arc::new(RwLock::new(::light::transaction_queue::TransactionQueue::default()));
+	let provider = ::light::provider::LightProvider::new(service.client().clone(), txq.clone());
+
+	// start network.
+	// set up bootnodes
+	let mut net_conf = cmd.net_conf;
+	if !cmd.custom_bootnodes {
+		net_conf.boot_nodes = spec.nodes.clone();
+	}
+
+	// TODO: configurable cache size.
+	let cache = LightDataCache::new(Default::default(), ::time::Duration::minutes(GAS_CORPUS_EXPIRATION_MINUTES));
+	let cache = Arc::new(::util::Mutex::new(cache));
+
+	// start on_demand service.
+	let on_demand = Arc::new(::light::on_demand::OnDemand::new(cache.clone()));
+
+	// set network path.
+	net_conf.net_config_path = Some(db_dirs.network_path().to_string_lossy().into_owned());
+	let sync_params = LightSyncParams {
+		network_config: net_conf.into_basic().map_err(|e| format!("Failed to produce network config: {}", e))?,
+		client: Arc::new(provider),
+		network_id: cmd.network_id.unwrap_or(spec.network_id()),
+		subprotocol_name: ::ethsync::LIGHT_PROTOCOL,
+		handlers: vec![on_demand.clone()],
+	};
+	let light_sync = LightSync::new(sync_params).map_err(|e| format!("Error starting network: {}", e))?;
+	let light_sync = Arc::new(light_sync);
+
+	// spin up event loop
+	let event_loop = EventLoop::spawn();
+
+	// queue cull service.
+	let queue_cull = Arc::new(::light_helpers::QueueCull {
+		client: service.client().clone(),
+		sync: light_sync.clone(),
+		on_demand: on_demand.clone(),
+		txq: txq.clone(),
+		remote: event_loop.remote(),
+	});
+
+	service.register_handler(queue_cull).map_err(|e| format!("Error attaching service: {:?}", e))?;
+
+	// start the network.
+	light_sync.start_network();
+
+	// fetch service
+	let fetch = FetchClient::new().map_err(|e| format!("Error starting fetch client: {:?}", e))?;
+	let passwords = passwords_from_files(&cmd.acc_conf.password_files)?;
+
+	// prepare account provider
+	let account_provider = Arc::new(prepare_account_provider(&cmd.spec, &cmd.dirs, &spec.data_dir, cmd.acc_conf, &passwords)?);
+	let rpc_stats = Arc::new(informant::RpcStats::default());
+	let signer_path = cmd.signer_conf.signer_path.clone();
+
+	// start RPCs
+	let deps_for_rpc_apis = Arc::new(rpc_apis::LightDependencies {
+		signer_service: Arc::new(rpc_apis::SignerService::new(move || {
+			signer::generate_new_token(signer_path.clone()).map_err(|e| format!("{:?}", e))
+		}, cmd.ui_address)),
+		client: service.client().clone(),
+		sync: light_sync.clone(),
+		net: light_sync.clone(),
+		secret_store: account_provider,
+		logger: logger,
+		settings: Arc::new(cmd.net_settings),
+		on_demand: on_demand,
+		cache: cache,
+		transaction_queue: txq,
+		dapps_interface: match cmd.dapps_conf.enabled {
+			true => Some(cmd.http_conf.interface.clone()),
+			false => None,
+		},
+		dapps_port: match cmd.dapps_conf.enabled {
+			true => Some(cmd.http_conf.port),
+			false => None,
+		},
+		fetch: fetch,
+		geth_compatibility: cmd.geth_compatibility,
+	});
+
+	let dependencies = rpc::Dependencies {
+		apis: deps_for_rpc_apis.clone(),
+		remote: event_loop.raw_remote(),
+		stats: rpc_stats.clone(),
+	};
+
+	// start rpc servers
+	let _http_server = rpc::new_http(cmd.http_conf, &dependencies, None)?;
+	let _ipc_server = rpc::new_ipc(cmd.ipc_conf, &dependencies)?;
+
+	// the signer server
+	let signer_deps = signer::Dependencies {
+		apis: deps_for_rpc_apis.clone(),
+		remote: event_loop.raw_remote(),
+		rpc_stats: rpc_stats.clone(),
+	};
+	let signing_queue = deps_for_rpc_apis.signer_service.queue();
+	let _signer_server = signer::start(cmd.signer_conf.clone(), signing_queue, signer_deps)?;
+
+	// TODO: Dapps
+
+	// minimal informant thread. Just prints block number every 5 seconds.
+	// TODO: integrate with informant.rs
+	let informant_client = service.client().clone();
+	::std::thread::spawn(move || loop {
+		info!("#{}", informant_client.best_block_header().number());
+		::std::thread::sleep(::std::time::Duration::from_secs(5));
+	});
+
+	// wait for ctrl-c.
+	Ok(wait_for_exit(panic_handler, None, None, can_restart))
+}
+
 pub fn execute(cmd: RunCmd, can_restart: bool, logger: Arc<RotatingLogger>) -> Result<(bool, Option<String>), String> {
 	if cmd.ui && cmd.dapps_conf.enabled {
 		// Check if Parity is already running
@@ -157,12 +329,17 @@ pub fn execute(cmd: RunCmd, can_restart: bool, logger: Arc<RotatingLogger>) -> R
 		}
 	}
 
-	// set up panic handler
-	let panic_handler = PanicHandler::new_in_arc();
-
 	// increase max number of open files
 	raise_fd_limit();
 
+	// run as light client.
+	if cmd.light {
+		return execute_light(cmd, can_restart, logger);
+	}
+
+	// set up panic handler
+	let panic_handler = PanicHandler::new_in_arc();
+
 	// load spec
 	let spec = cmd.spec.spec()?;
 
@@ -244,6 +421,7 @@ pub fn execute(cmd: RunCmd, can_restart: bool, logger: Arc<RotatingLogger>) -> R
 	sync_config.fork_block = spec.fork_block();
 	sync_config.warp_sync = cmd.warp_sync;
 	sync_config.download_old_blocks = cmd.download_old_blocks;
+	sync_config.serve_light = cmd.serve_light;
 
 	let passwords = passwords_from_files(&cmd.acc_conf.password_files)?;
 
@@ -407,7 +585,8 @@ pub fn execute(cmd: RunCmd, can_restart: bool, logger: Arc<RotatingLogger>) -> R
 		true => None,
 		false => Some(account_provider.clone())
 	};
-	let deps_for_rpc_apis = Arc::new(rpc_apis::Dependencies {
+
+	let deps_for_rpc_apis = Arc::new(rpc_apis::FullDependencies {
 		signer_service: Arc::new(rpc_apis::SignerService::new(move || {
 			signer::generate_new_token(signer_path.clone()).map_err(|e| format!("{:?}", e))
 		}, cmd.ui_address)),
@@ -440,13 +619,18 @@ pub fn execute(cmd: RunCmd, can_restart: bool, logger: Arc<RotatingLogger>) -> R
 		stats: rpc_stats.clone(),
 	};
 
-	// the dapps middleware
-	let dapps_deps = dapps::Dependencies {
-		client: client.clone(),
-		sync: sync_provider.clone(),
-		remote: event_loop.raw_remote(),
-		fetch: fetch.clone(),
-		signer: deps_for_rpc_apis.signer_service.clone(),
+	// the dapps server
+	let dapps_deps = {
+		let (sync, client) = (sync_provider.clone(), client.clone());
+		let contract_client = Arc::new(::dapps::FullRegistrar { client: client.clone() });
+
+		dapps::Dependencies {
+			sync_status: Arc::new(move || is_major_importing(Some(sync.status().state), client.queue_info())),
+			contract_client: contract_client,
+			remote: event_loop.raw_remote(),
+			fetch: fetch.clone(),
+			signer: deps_for_rpc_apis.signer_service.clone(),
+		}
 	};
 	let dapps_middleware = dapps::new(cmd.dapps_conf.clone(), dapps_deps)?;
 
@@ -460,7 +644,8 @@ pub fn execute(cmd: RunCmd, can_restart: bool, logger: Arc<RotatingLogger>) -> R
 		remote: event_loop.raw_remote(),
 		rpc_stats: rpc_stats.clone(),
 	};
-	let signer_server = signer::start(cmd.signer_conf.clone(), signer_deps)?;
+	let signing_queue = deps_for_rpc_apis.signer_service.queue();
+	let signer_server = signer::start(cmd.signer_conf.clone(), signing_queue, signer_deps)?;
 
 	// secret store key server
 	let secretstore_deps = secretstore::Dependencies {

parity/signer.rs

@@ -23,7 +23,7 @@ pub use ethcore_signer::Server as SignerServer;
 use ansi_term::Colour;
 use dir::default_data_path;
 use ethcore_rpc::informant::RpcStats;
-use ethcore_rpc;
+use ethcore_rpc::{self, ConfirmationsQueue};
 use ethcore_signer as signer;
 use helpers::replace_home;
 use parity_reactor::TokioRemote;
@@ -55,8 +55,8 @@ impl Default for Configuration {
 	}
 }
 
-pub struct Dependencies {
-	pub apis: Arc<rpc_apis::Dependencies>,
+pub struct Dependencies<D: rpc_apis::Dependencies> {
+	pub apis: Arc<D>,
 	pub remote: TokioRemote,
 	pub rpc_stats: Arc<RpcStats>,
 }
@@ -77,11 +77,15 @@ impl signer::MetaExtractor<ethcore_rpc::Metadata> for StandardExtractor {
 	}
 }
 
-pub fn start(conf: Configuration, deps: Dependencies) -> Result<Option<SignerServer>, String> {
+pub fn start<D: rpc_apis::Dependencies>(
+	conf: Configuration,
+	queue: Arc<ConfirmationsQueue>,
+	deps: Dependencies<D>,
+) -> Result<Option<SignerServer>, String> {
 	if !conf.enabled {
 		Ok(None)
 	} else {
-		Ok(Some(do_start(conf, deps)?))
+		Ok(Some(do_start(conf, queue, deps)?))
 	}
 }
 
@@ -125,14 +129,18 @@ pub fn generate_new_token(path: String) -> io::Result<String> {
 	Ok(code)
 }
 
-fn do_start(conf: Configuration, deps: Dependencies) -> Result<SignerServer, String> {
+fn do_start<D: rpc_apis::Dependencies>(
+	conf: Configuration,
+	queue: Arc<ConfirmationsQueue>,
+	deps: Dependencies<D>
+) -> Result<SignerServer, String> {
 	let addr = format!("{}:{}", conf.interface, conf.port)
 		.parse()
 		.map_err(|_| format!("Invalid port specified: {}", conf.port))?;
 
 	let start_result = {
 		let server = signer::ServerBuilder::new(
-			deps.apis.signer_service.queue(),
+			queue,
 			codes_path(conf.signer_path),
 		);
 		if conf.skip_origin_validation {
@@ -141,7 +149,7 @@ fn do_start(conf: Configuration, deps: Dependencies) -> Result<SignerServer, Str
 		}
 		let server = server.skip_origin_validation(conf.skip_origin_validation);
 		let server = server.stats(deps.rpc_stats.clone());
-		let handler = rpc_apis::setup_rpc(deps.rpc_stats, deps.apis, rpc_apis::ApiSet::SafeContext);
+		let handler = rpc_apis::setup_rpc(deps.rpc_stats, &*deps.apis, rpc_apis::ApiSet::SafeContext);
 		let remote = deps.remote.clone();
 		server.start_with_extractor(addr, handler, remote, StandardExtractor)
 	};

rpc/src/v1/helpers/dispatch.rs

@@ -207,7 +207,6 @@ pub fn fetch_gas_price_corpus(
 }
 
 /// Dispatcher for light clients -- fetches default gas price, next nonce, etc. from network.
-/// Light client `ETH` RPC.
 #[derive(Clone)]
 pub struct LightDispatcher {
 	/// Sync service.

rpc/src/v1/impls/light/eth.rs

@@ -166,7 +166,6 @@ impl EthClient {
 	fn proved_execution(&self, req: CallRequest, num: Trailing<BlockNumber>) -> BoxFuture<ExecutionResult, Error> {
 		const DEFAULT_GAS_PRICE: U256 = U256([0, 0, 0, 21_000_000]);
 
-
 		let (sync, on_demand, client) = (self.sync.clone(), self.on_demand.clone(), self.client.clone());
 		let req: CRequest = req.into();
 		let id = num.0.into();
@@ -245,7 +244,22 @@ impl Eth for EthClient {
 	}
 
 	fn syncing(&self) -> Result<SyncStatus, Error> {
-		rpc_unimplemented!()
+		if self.sync.is_major_importing() {
+			let chain_info = self.client.chain_info();
+			let current_block = U256::from(chain_info.best_block_number);
+			let highest_block = self.sync.highest_block().map(U256::from)
+				.unwrap_or_else(|| current_block.clone());
+
+			Ok(SyncStatus::Info(SyncInfo {
+				starting_block: U256::from(self.sync.start_block()).into(),
+				current_block: current_block.into(),
+				highest_block: highest_block.into(),
+				warp_chunks_amount: None,
+				warp_chunks_processed: None,
+			}))
+		} else {
+			Ok(SyncStatus::None)
+		}
 	}
 
 	fn author(&self, _meta: Self::Metadata) -> BoxFuture<RpcH160, Error> {

rpc/src/v1/impls/light/mod.rs

@@ -23,7 +23,10 @@ pub mod eth;
 pub mod parity;
 pub mod parity_set;
 pub mod trace;
+pub mod net;
 
 pub use self::eth::EthClient;
 pub use self::parity::ParityClient;
 pub use self::parity_set::ParitySetClient;
+pub use self::net::NetClient;
+pub use self::trace::TracesClient;

rpc/src/v1/impls/light/net.rs

@@ -0,0 +1,49 @@
+// 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/>.
+
+//! Net rpc implementation.
+use std::sync::Arc;
+use jsonrpc_core::Error;
+use ethsync::LightSyncProvider;
+use v1::traits::Net;
+
+/// Net rpc implementation.
+pub struct NetClient<S: ?Sized> {
+	sync: Arc<S>
+}
+
+impl<S: ?Sized> NetClient<S> where S: LightSyncProvider {
+	/// Creates new NetClient.
+	pub fn new(sync: Arc<S>) -> Self {
+		NetClient {
+			sync: sync,
+		}
+	}
+}
+
+impl<S: ?Sized + Sync + Send + 'static> Net for NetClient<S> where S: LightSyncProvider {
+	fn version(&self) -> Result<String, Error> {
+		Ok(format!("{}", self.sync.network_id()).to_owned())
+	}
+
+	fn peer_count(&self) -> Result<String, Error> {
+		Ok(format!("0x{:x}", self.sync.peer_numbers().connected as u64).to_owned())
+	}
+
+	fn is_listening(&self) -> Result<bool, Error> {
+		Ok(true)
+	}
+}

rpc/src/v1/impls/net.rs

@@ -21,7 +21,7 @@ use ethsync::SyncProvider;
 use v1::traits::Net;
 
 /// Net rpc implementation.
-pub struct NetClient<S: ?Sized> where S: SyncProvider {
+pub struct NetClient<S: ?Sized> {
 	sync: Weak<S>
 }
 

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

@@ -83,7 +83,7 @@ impl SyncProvider for TestSyncProvider {
 					difficulty: Some(40.into()),
 					head: 50.into(),
 				}),
-				les_info: None,
+				pip_info: None,
 			},
 			PeerInfo {
 				id: None,
@@ -96,7 +96,7 @@ impl SyncProvider for TestSyncProvider {
 					difficulty: None,
 					head: 60.into()
 				}),
-				les_info: None,
+				pip_info: None,
 			}
 		]
 	}

rpc/src/v1/tests/mocked/parity.rs

@@ -304,7 +304,7 @@ fn rpc_parity_net_peers() {
 	let io = deps.default_client();
 
 	let request = r#"{"jsonrpc": "2.0", "method": "parity_netPeers", "params":[], "id": 1}"#;
-	let response = r#"{"jsonrpc":"2.0","result":{"active":0,"connected":120,"max":50,"peers":[{"caps":["eth/62","eth/63"],"id":"node1","name":"Parity/1","network":{"localAddress":"127.0.0.1:8888","remoteAddress":"127.0.0.1:7777"},"protocols":{"eth":{"difficulty":"0x28","head":"0000000000000000000000000000000000000000000000000000000000000032","version":62},"les":null}},{"caps":["eth/63","eth/64"],"id":null,"name":"Parity/2","network":{"localAddress":"127.0.0.1:3333","remoteAddress":"Handshake"},"protocols":{"eth":{"difficulty":null,"head":"000000000000000000000000000000000000000000000000000000000000003c","version":64},"les":null}}]},"id":1}"#;
+	let response = r#"{"jsonrpc":"2.0","result":{"active":0,"connected":120,"max":50,"peers":[{"caps":["eth/62","eth/63"],"id":"node1","name":"Parity/1","network":{"localAddress":"127.0.0.1:8888","remoteAddress":"127.0.0.1:7777"},"protocols":{"eth":{"difficulty":"0x28","head":"0000000000000000000000000000000000000000000000000000000000000032","version":62},"pip":null}},{"caps":["eth/63","eth/64"],"id":null,"name":"Parity/2","network":{"localAddress":"127.0.0.1:3333","remoteAddress":"Handshake"},"protocols":{"eth":{"difficulty":null,"head":"000000000000000000000000000000000000000000000000000000000000003c","version":64},"pip":null}}]},"id":1}"#;
 
 	assert_eq!(io.handle_request_sync(request), Some(response.to_owned()));
 }

rpc/src/v1/types/mod.rs

@@ -65,7 +65,7 @@ pub use self::receipt::Receipt;
 pub use self::rpc_settings::RpcSettings;
 pub use self::sync::{
 	SyncStatus, SyncInfo, Peers, PeerInfo, PeerNetworkInfo, PeerProtocolsInfo,
-	TransactionStats, ChainStatus, EthProtocolInfo, LesProtocolInfo,
+	TransactionStats, ChainStatus, EthProtocolInfo, PipProtocolInfo,
 };
 pub use self::trace::{LocalizedTrace, TraceResults};
 pub use self::trace_filter::TraceFilter;

rpc/src/v1/types/sync.rs

@@ -83,8 +83,8 @@ pub struct PeerNetworkInfo {
 pub struct PeerProtocolsInfo {
 	/// Ethereum protocol information
 	pub eth: Option<EthProtocolInfo>,
-	/// LES protocol information.
-	pub les: Option<LesProtocolInfo>,
+	/// PIP protocol information.
+	pub pip: Option<PipProtocolInfo>,
 }
 
 /// Peer Ethereum protocol information
@@ -108,10 +108,10 @@ impl From<ethsync::EthProtocolInfo> for EthProtocolInfo {
 	}
 }
 
-/// Peer LES protocol information
+/// Peer PIP protocol information
 #[derive(Default, Debug, Serialize)]
-pub struct LesProtocolInfo {
-	/// Negotiated LES protocol version
+pub struct PipProtocolInfo {
+	/// Negotiated PIP protocol version
 	pub version: u32,
 	/// Peer total difficulty
 	pub difficulty: U256,
@@ -119,9 +119,9 @@ pub struct LesProtocolInfo {
 	pub head: String,
 }
 
-impl From<ethsync::LesProtocolInfo> for LesProtocolInfo {
-	fn from(info: ethsync::LesProtocolInfo) -> Self {
-		LesProtocolInfo {
+impl From<ethsync::PipProtocolInfo> for PipProtocolInfo {
+	fn from(info: ethsync::PipProtocolInfo) -> Self {
+		PipProtocolInfo {
 			version: info.version,
 			difficulty: info.difficulty.into(),
 			head: info.head.hex(),
@@ -171,7 +171,7 @@ impl From<SyncPeerInfo> for PeerInfo {
 			},
 			protocols: PeerProtocolsInfo {
 				eth: p.eth_info.map(Into::into),
-				les: p.les_info.map(Into::into),
+				pip: p.pip_info.map(Into::into),
 			},
 		}
 	}

sync/src/api.rs

@@ -43,7 +43,7 @@ pub const WARP_SYNC_PROTOCOL_ID: ProtocolId = *b"par";
 /// Ethereum sync protocol
 pub const ETH_PROTOCOL: ProtocolId = *b"eth";
 /// Ethereum light protocol
-pub const LIGHT_PROTOCOL: ProtocolId = *b"plp";
+pub const LIGHT_PROTOCOL: ProtocolId = *b"pip";
 
 /// Sync configuration
 #[derive(Debug, Clone, Copy)]
@@ -126,7 +126,7 @@ pub struct PeerInfo {
 	/// Eth protocol info.
 	pub eth_info: Option<EthProtocolInfo>,
 	/// Light protocol info.
-	pub les_info: Option<LesProtocolInfo>,
+	pub pip_info: Option<PipProtocolInfo>,
 }
 
 /// Ethereum protocol info.
@@ -141,10 +141,10 @@ pub struct EthProtocolInfo {
 	pub difficulty: Option<U256>,
 }
 
-/// LES protocol info.
+/// PIP protocol info.
 #[derive(Debug)]
 #[cfg_attr(feature = "ipc", derive(Binary))]
-pub struct LesProtocolInfo {
+pub struct PipProtocolInfo {
 	/// Protocol version
 	pub version: u32,
 	/// SHA3 of peer best block hash
@@ -153,9 +153,9 @@ pub struct LesProtocolInfo {
 	pub difficulty: U256,
 }
 
-impl From<light_net::Status> for LesProtocolInfo {
+impl From<light_net::Status> for PipProtocolInfo {
 	fn from(status: light_net::Status) -> Self {
-		LesProtocolInfo {
+		PipProtocolInfo {
 			version: status.protocol_version,
 			head: status.head_hash,
 			difficulty: status.head_td,
@@ -184,7 +184,7 @@ pub struct EthSync {
 	network: NetworkService,
 	/// Main (eth/par) protocol handler
 	eth_handler: Arc<SyncProtocolHandler>,
-	/// Light (les) protocol handler
+	/// Light (pip) protocol handler
 	light_proto: Option<Arc<LightProtocol>>,
 	/// The main subprotocol name
 	subprotocol_name: [u8; 3],
@@ -264,7 +264,7 @@ impl SyncProvider for EthSync {
 					remote_address: session_info.remote_address,
 					local_address: session_info.local_address,
 					eth_info: eth_sync.peer_info(&peer_id),
-					les_info: light_proto.as_ref().and_then(|lp| lp.peer_status(&peer_id)).map(Into::into),
+					pip_info: light_proto.as_ref().and_then(|lp| lp.peer_status(&peer_id)).map(Into::into),
 				})
 			}).collect()
 		}).unwrap_or_else(Vec::new)
@@ -408,13 +408,13 @@ impl ChainNotify for EthSync {
 	}
 }
 
-/// LES event handler.
+/// PIP event handler.
 /// Simply queues transactions from light client peers.
 struct TxRelay(Arc<BlockChainClient>);
 
 impl LightHandler for TxRelay {
 	fn on_transactions(&self, ctx: &EventContext, relay: &[::ethcore::transaction::UnverifiedTransaction]) {
-		trace!(target: "les", "Relaying {} transactions from peer {}", relay.len(), ctx.peer());
+		trace!(target: "pip", "Relaying {} transactions from peer {}", relay.len(), ctx.peer());
 		self.0.queue_transactions(relay.iter().map(|tx| ::rlp::encode(tx).to_vec()).collect(), ctx.peer())
 	}
 }
@@ -642,6 +642,9 @@ pub trait LightSyncProvider {
 	/// Get peers information
 	fn peers(&self) -> Vec<PeerInfo>;
 
+	/// Get network id.
+	fn network_id(&self) -> u64;
+
 	/// Get the enode if available.
 	fn enode(&self) -> Option<String>;
 
@@ -659,13 +662,17 @@ pub struct LightSyncParams<L> {
 	pub network_id: u64,
 	/// Subprotocol name.
 	pub subprotocol_name: [u8; 3],
+	/// Other handlers to attach.
+	pub handlers: Vec<Arc<LightHandler>>,
 }
 
 /// Service for light synchronization.
 pub struct LightSync {
 	proto: Arc<LightProtocol>,
+	sync: Arc<::light_sync::SyncInfo + Sync + Send>,
 	network: NetworkService,
 	subprotocol_name: [u8; 3],
+	network_id: u64,
 }
 
 impl LightSync {
@@ -676,7 +683,7 @@ impl LightSync {
 		use light_sync::LightSync as SyncHandler;
 
 		// initialize light protocol handler and attach sync module.
-		let light_proto = {
+		let (sync, light_proto) = {
 			let light_params = LightParams {
 				network_id: params.network_id,
 				flow_params: Default::default(), // or `None`?
@@ -689,18 +696,24 @@ impl LightSync {
 			};
 
 			let mut light_proto = LightProtocol::new(params.client.clone(), light_params);
-			let sync_handler = try!(SyncHandler::new(params.client.clone()));
-			light_proto.add_handler(Arc::new(sync_handler));
+			let sync_handler = Arc::new(try!(SyncHandler::new(params.client.clone())));
+			light_proto.add_handler(sync_handler.clone());
 
-			Arc::new(light_proto)
+			for handler in params.handlers {
+				light_proto.add_handler(handler);
+			}
+
+			(sync_handler, Arc::new(light_proto))
 		};
 
 		let service = try!(NetworkService::new(params.network_config));
 
 		Ok(LightSync {
 			proto: light_proto,
+			sync: sync,
 			network: service,
 			subprotocol_name: params.subprotocol_name,
+			network_id: params.network_id,
 		})
 	}
 
@@ -715,6 +728,12 @@ impl LightSync {
 	}
 }
 
+impl ::std::ops::Deref for LightSync {
+	type Target = ::light_sync::SyncInfo;
+
+	fn deref(&self) -> &Self::Target { &*self.sync }
+}
+
 impl ManageNetwork for LightSync {
 	fn accept_unreserved_peers(&self) {
 		self.network.set_non_reserved_mode(NonReservedPeerMode::Accept);
@@ -786,7 +805,7 @@ impl LightSyncProvider for LightSync {
 					remote_address: session_info.remote_address,
 					local_address: session_info.local_address,
 					eth_info: None,
-					les_info: self.proto.peer_status(&peer_id).map(Into::into),
+					pip_info: self.proto.peer_status(&peer_id).map(Into::into),
 				})
 			}).collect()
 		}).unwrap_or_else(Vec::new)
@@ -796,6 +815,10 @@ impl LightSyncProvider for LightSync {
 		self.network.external_url()
 	}
 
+	fn network_id(&self) -> u64 {
+		self.network_id
+	}
+
 	fn transactions_stats(&self) -> BTreeMap<H256, TransactionStats> {
 		Default::default() // TODO
 	}

sync/src/light_sync/mod.rs

@@ -32,7 +32,7 @@
 //!   announced blocks.
 //! - On bad block/response, punish peer and reset.
 
-use std::collections::HashMap;
+use std::collections::{HashMap, HashSet};
 use std::mem;
 use std::sync::Arc;
 
@@ -150,6 +150,19 @@ impl AncestorSearch {
 		}
 	}
 
+	fn requests_abandoned(self, req_ids: &[ReqId]) -> AncestorSearch {
+		match self {
+			AncestorSearch::Awaiting(id, start, req) => {
+				if req_ids.iter().find(|&x| x == &id).is_some() {
+					AncestorSearch::Queued(start)
+				} else {
+					AncestorSearch::Awaiting(id, start, req)
+				}
+			}
+			other => other,
+		}
+	}
+
 	fn dispatch_request<F>(self, mut dispatcher: F) -> AncestorSearch
 		where F: FnMut(HeadersRequest) -> Option<ReqId>
 	{
@@ -206,8 +219,10 @@ impl<'a> ResponseContext for ResponseCtx<'a> {
 
 /// Light client synchronization manager. See module docs for more details.
 pub struct LightSync<L: AsLightClient> {
+	start_block_number: u64,
 	best_seen: Mutex<Option<ChainInfo>>, // best seen block on the network.
 	peers: RwLock<HashMap<PeerId, Mutex<Peer>>>, // peers which are relevant to synchronization.
+	pending_reqs: Mutex<HashSet<ReqId>>, // requests from this handler.
 	client: Arc<L>,
 	rng: Mutex<OsRng>,
 	state: Mutex<SyncState>,
@@ -270,7 +285,8 @@ impl<L: AsLightClient + Send + Sync> Handler for LightSync<L> {
 
 			*state = match mem::replace(&mut *state, SyncState::Idle) {
 				SyncState::Idle => SyncState::Idle,
-				SyncState::AncestorSearch(search) => SyncState::AncestorSearch(search),
+				SyncState::AncestorSearch(search) =>
+					SyncState::AncestorSearch(search.requests_abandoned(unfulfilled)),
 				SyncState::Rounds(round) => SyncState::Rounds(round.requests_abandoned(unfulfilled)),
 			};
 		}
@@ -320,6 +336,10 @@ impl<L: AsLightClient + Send + Sync> Handler for LightSync<L> {
 			return
 		}
 
+		if !self.pending_reqs.lock().remove(&req_id) {
+			return
+		}
+
 		let headers = match responses.get(0) {
 			Some(&request::Response::Headers(ref response)) => &response.headers[..],
 			Some(_) => {
@@ -418,8 +438,10 @@ impl<L: AsLightClient> LightSync<L> {
 			let best_td = chain_info.pending_total_difficulty;
 			let sync_target = match *self.best_seen.lock() {
 				Some(ref target) if target.head_td > best_td => (target.head_num, target.head_hash),
-				_ => {
-					trace!(target: "sync", "No target to sync to.");
+				ref other => {
+					let network_score = other.as_ref().map(|target| target.head_td);
+					trace!(target: "sync", "No target to sync to. Network score: {:?}, Local score: {:?}",
+						network_score, best_td);
 					*state = SyncState::Idle;
 					return;
 				}
@@ -493,6 +515,7 @@ impl<L: AsLightClient> LightSync<L> {
 				for peer in &peer_ids {
 					match ctx.request_from(*peer, request.clone()) {
 						Ok(id) => {
+							self.pending_reqs.lock().insert(id.clone());
 							return Some(id)
 						}
 						Err(NetError::NoCredits) => {}
@@ -523,11 +546,48 @@ impl<L: AsLightClient> LightSync<L> {
 	/// so it can act on events.
 	pub fn new(client: Arc<L>) -> Result<Self, ::std::io::Error> {
 		Ok(LightSync {
+			start_block_number: client.as_light_client().chain_info().best_block_number,
 			best_seen: Mutex::new(None),
 			peers: RwLock::new(HashMap::new()),
+			pending_reqs: Mutex::new(HashSet::new()),
 			client: client,
 			rng: Mutex::new(try!(OsRng::new())),
 			state: Mutex::new(SyncState::Idle),
 		})
 	}
 }
+
+/// Trait for erasing the type of a light sync object and exposing read-only methods.
+pub trait SyncInfo {
+	/// Get the highest block advertised on the network.
+	fn highest_block(&self) -> Option<u64>;
+
+	/// Get the block number at the time of sync start.
+	fn start_block(&self) -> u64;
+
+	/// Whether major sync is underway.
+	fn is_major_importing(&self) -> bool;
+}
+
+impl<L: AsLightClient> SyncInfo for LightSync<L> {
+	fn highest_block(&self) -> Option<u64> {
+		self.best_seen.lock().as_ref().map(|x| x.head_num)
+	}
+
+	fn start_block(&self) -> u64 {
+		self.start_block_number
+	}
+
+	fn is_major_importing(&self) -> bool {
+		const EMPTY_QUEUE: usize = 3;
+
+		if self.client.as_light_client().queue_info().unverified_queue_size > EMPTY_QUEUE {
+			return true;
+		}
+
+		match *self.state.lock() {
+			SyncState::Idle => false,
+			_ => true,
+		}
+	}
+}

sync/src/light_sync/tests/test_net.rs

@@ -207,7 +207,7 @@ impl TestNet<Peer> {
 	pub fn light(n_light: usize, n_full: usize) -> Self {
 		let mut peers = Vec::with_capacity(n_light + n_full);
 		for _ in 0..n_light {
-			let client = LightClient::new(Default::default(), &Spec::new_test(), IoChannel::disconnected());
+			let client = LightClient::in_memory(Default::default(), &Spec::new_test(), IoChannel::disconnected());
 			peers.push(Arc::new(Peer::new_light(Arc::new(client))))
 		}