handle events, minimal state machine

ethcore/light/src/net/context.rs

@@ -105,6 +105,9 @@ pub trait EventContext: BasicContext {
 	/// Get the peer relevant to the event e.g. message sender,
 	/// disconnected/connected peer.
 	fn peer(&self) -> PeerId;
+
+	/// Treat the event context as a basic context.
+	fn as_basic(&self) -> &BasicContext;
 }
 
 /// Basic context.
@@ -182,4 +185,8 @@ impl<'a> EventContext for Ctx<'a> {
 	fn peer(&self) -> PeerId {
 		self.peer
 	}
+
+	fn as_basic(&self) -> &BasicContext {
+		&*self
+	}
 }

sync/src/lib.rs

@@ -54,11 +54,12 @@ extern crate ethcore_ipc as ipc;
 mod chain;
 mod blocks;
 mod block_sync;
-mod light_sync;
 mod sync_io;
 mod snapshot;
 mod transactions_stats;
 
+pub mod light_sync;
+
 #[cfg(test)]
 mod tests;
 

sync/src/light_sync/mod.rs

@@ -25,18 +25,22 @@
 //! in the same binary; unlike a full node which might communicate via IPC.
 
 use std::collections::HashMap;
-use std::fmt;
+use std::mem;
 use std::sync::Arc;
 
 use ethcore::header::Header;
 
 use light::client::LightChainClient;
-use light::net::{Announcement, Error as NetError, Handler, EventContext, Capabilities, ReqId, Status};
+use light::net::{
+	Announcement, Handler, BasicContext, EventContext,
+	Capabilities, ReqId, Status
+};
 use light::request;
 use network::PeerId;
-use rlp::{DecoderError, UntrustedRlp, View};
 use util::{Bytes, U256, H256, Mutex, RwLock};
 
+use self::sync_round::{SyncRound, ResponseContext};
+
 mod response;
 mod sync_round;
 
@@ -49,7 +53,6 @@ struct ChainInfo {
 }
 
 struct Peer {
-	first_status: ChainInfo,
 	status: ChainInfo,
 }
 
@@ -57,17 +60,48 @@ impl Peer {
 	/// Create a peer object.
 	fn new(chain_info: ChainInfo) -> Self {
 		Peer {
-			first_status: chain_info.clone(),
 			status: chain_info.clone(),
 		}
 	}
 }
 
+// Search for a common ancestor.
+struct AncestorSearch {
+	last_batched: u64,
+	req_id: ReqId,
+}
+
+// synchronization state machine.
+enum SyncState {
+	// Idle (waiting for peers)
+	Idle,
+	// searching for common ancestor with best chain.
+	// queue should be cleared at this phase.
+	AncestorSearch(AncestorSearch),
+	// Doing sync rounds.
+	Rounds(SyncRound),
+}
+
+struct ResponseCtx<'a> {
+	peer: PeerId,
+	req_id: ReqId,
+	ctx: &'a BasicContext,
+	data: &'a [Bytes],
+}
+
+impl<'a> ResponseContext for ResponseCtx<'a> {
+	fn responder(&self) -> PeerId { self.peer }
+	fn req_id(&self) -> &ReqId { &self.req_id }
+	fn data(&self) -> &[Bytes] { self.data }
+	fn punish_responder(&self) { self.ctx.disable_peer(self.peer) }
+}
+
 /// Light client synchronization manager. See module docs for more details.
 pub struct LightSync<L: LightChainClient> {
 	best_seen: Mutex<Option<(H256, U256)>>, // best seen block on the network.
 	peers: RwLock<HashMap<PeerId, Mutex<Peer>>>, // peers which are relevant to synchronization.
 	client: Arc<L>,
+	state: Mutex<SyncState>,
 }
 
 impl<L: LightChainClient> Handler for LightSync<L> {
@@ -75,7 +109,8 @@ impl<L: LightChainClient> Handler for LightSync<L> {
 		let our_best = self.client.chain_info().best_block_number;
 
 		if !capabilities.serve_headers || status.head_num <= our_best {
-			trace!(target: "sync", "Ignoring irrelevant peer: {}", ctx.peer());
+			trace!(target: "sync", "Disconnecting irrelevant peer: {}", ctx.peer());
+			ctx.disconnect_peer(ctx.peer());
 			return;
 		}
 
@@ -85,27 +120,130 @@ impl<L: LightChainClient> Handler for LightSync<L> {
 			head_num: status.head_num,
 		};
 
-		self.peers.write().insert(ctx.peer(), Mutex::new(Peer::new(chain_info)));
+		let mut best = self.best_seen.lock();
+		if best.as_ref().map_or(true, |b| status.head_td > b.1) {
+			*best = Some((status.head_hash, status.head_td));
 		}
 
-	fn on_disconnect(&self, ctx: &EventContext, _unfulfilled: &[ReqId]) {
+		self.peers.write().insert(ctx.peer(), Mutex::new(Peer::new(chain_info)));
+		self.maintain_sync(ctx.as_basic());
+	}
+
+	fn on_disconnect(&self, ctx: &EventContext, unfulfilled: &[ReqId]) {
 		let peer_id = ctx.peer();
 
+		let peer = match self.peers.write().remove(&peer_id).map(|p| p.into_inner()) {
+			Some(peer) => peer,
+			None => return,
+		};
+
+		let new_best = {
+			let mut best = self.best_seen.lock();
+			let peer_best = (peer.status.head_hash, peer.status.head_td);
+
+			if best.as_ref().map_or(false, |b| b == &peer_best) {
+				// search for next-best block.
+				let next_best: Option<(H256, U256)> = self.peers.read().values()
+					.map(|p| p.lock())
+					.map(|p| (p.status.head_hash, p.status.head_td))
+					.fold(None, |acc, x| match acc {
+						Some(acc) => if x.1 > acc.1 { Some(x) } else { Some(acc) },
+						None => Some(x),
+					});
+
+				*best = next_best;
+			}
+
+			best.clone()
+		};
+
+		if new_best.is_none() {
+			debug!(target: "sync", "No peers remain. Reverting to idle");
+			*self.state.lock() = SyncState::Idle;
+		} else {
+			let mut state = self.state.lock();
+
+			*state = match mem::replace(&mut *state, SyncState::Idle) {
+				SyncState::Idle => SyncState::Idle,
+				SyncState::AncestorSearch(search) => SyncState::AncestorSearch(search),
+				SyncState::Rounds(round) => SyncState::Rounds(round.requests_abandoned(unfulfilled)),
+			};
+		}
+
+		self.maintain_sync(ctx.as_basic());
 	}
 
 	fn on_announcement(&self, ctx: &EventContext, announcement: &Announcement) {
-		// restart search for common ancestor if necessary.
-		// restart download if necessary.
-		// if this is a peer we found irrelevant earlier, we may want to
-		// re-evaluate their usefulness.
-		if !self.peers.read().contains_key(&ctx.peer()) { return }
+		let last_td = {
+			let peers = self.peers.read();
+			match peers.get(&ctx.peer()){
+				None => return,
+				Some(peer) => {
+					let mut peer = peer.lock();
+					let last_td = peer.status.head_td;
+					peer.status = ChainInfo {
+						head_td: announcement.head_td,
+						head_hash: announcement.head_hash,
+						head_num: announcement.head_num,
+					};
+					last_td
+				}
+			}
+		};
 
 		trace!(target: "sync", "Announcement from peer {}: new chain head {:?}, reorg depth {}",
 			ctx.peer(), (announcement.head_hash, announcement.head_num), announcement.reorg_depth);
+
+		if last_td < announcement.head_td {
+			trace!(target: "sync", "Peer {} moved backwards.", ctx.peer());
+			self.peers.write().remove(&ctx.peer());
+			ctx.disconnect_peer(ctx.peer());
+		}
+
+		let mut best = self.best_seen.lock();
+		if best.as_ref().map_or(true, |b| announcement.head_td > b.1) {
+			*best = Some((announcement.head_hash, announcement.head_td));
+		}
+
+		self.maintain_sync(ctx.as_basic());
 	}
 
 	fn on_block_headers(&self, ctx: &EventContext, req_id: ReqId, headers: &[Bytes]) {
-		let peer_id = ctx.peer();
+		if !self.peers.read().contains_key(&ctx.peer()) {
+			return;
+		}
+
+		{
+			let mut state = self.state.lock();
+
+			*state = match mem::replace(&mut *state, SyncState::Idle) {
+				SyncState::Idle => SyncState::Idle,
+				SyncState::AncestorSearch(search) => SyncState::AncestorSearch(search),
+				SyncState::Rounds(round) => {
+					SyncState::Rounds(round.process_response(&ResponseCtx {
+						peer: ctx.peer(),
+						req_id: req_id,
+						ctx: ctx.as_basic(),
+						data: headers,
+					}))
+				}
+			};
+		}
+
+		self.maintain_sync(ctx.as_basic());
+	}
+
+	fn tick(&self, ctx: &BasicContext) {
+		self.maintain_sync(ctx);
+	}
+}
+
+// private helpers
+impl<L: LightChainClient> LightSync<L> {
+	fn maintain_sync(&self, ctx: &BasicContext) {
+		const DRAIN_AMOUNT: usize = 256;
+
+		unimplemented!()
 	}
 }
 
@@ -120,6 +258,7 @@ impl<L: LightChainClient> LightSync<L> {
 			best_seen: Mutex::new(None),
 			peers: RwLock::new(HashMap::new()),
 			client: client,
+			state: Mutex::new(SyncState::Idle),
 		}
 	}
 }

sync/src/light_sync/sync_round.rs

@@ -18,17 +18,14 @@
 
 use std::cmp::Ordering;
 use std::collections::{BinaryHeap, HashMap, HashSet, VecDeque};
-use std::mem;
 
 use ethcore::header::Header;
 
-use light::client::LightChainClient;
-use light::net::{EventContext, ReqId};
+use light::net::ReqId;
 use light::request::Headers as HeadersRequest;
 
 use network::PeerId;
-use rlp::{UntrustedRlp, View};
-use util::{Bytes, H256, Mutex};
+use util::{Bytes, H256};
 
 use super::response;
 
@@ -47,7 +44,7 @@ pub trait ResponseContext {
 	/// Get the peer who sent this response.
 	fn responder(&self) ->	PeerId;
 	/// Get the request ID this response corresponds to.
-	fn req_id(&self) -> ReqId;
+	fn req_id(&self) -> &ReqId;
 	/// Get the (unverified) response data.
 	fn data(&self) -> &[Bytes];
 	/// Punish the responder.
@@ -173,7 +170,7 @@ impl Fetcher {
 	}
 
 	fn process_response<R: ResponseContext>(mut self, ctx: &R) -> SyncRound {
-		let mut request = match self.pending.remove(&ctx.req_id()) {
+		let mut request = match self.pending.remove(ctx.req_id()) {
 			Some(request) => request,
 			None => return SyncRound::Fetch(self),
 		};
@@ -267,8 +264,8 @@ impl Fetcher {
 		SyncRound::Fetch(self)
 	}
 
-	fn drain(mut self, headers: &mut Vec<Header>, max: usize) -> SyncRound {
-		let max = ::std::cmp::min(max, self.ready.len());
+	fn drain(mut self, headers: &mut Vec<Header>, max: Option<usize>) -> SyncRound {
+		let max = ::std::cmp::min(max.unwrap_or(usize::max_value()), self.ready.len());
 		headers.extend(self.ready.drain(0..max));
 
 		if self.sparse.is_empty() && self.ready.is_empty() {
@@ -321,7 +318,7 @@ impl RoundStart {
 
 	fn process_response<R: ResponseContext>(mut self, ctx: &R) -> SyncRound {
 		let req = match self.pending_req.take() {
-			Some((id, ref req)) if ctx.req_id() == id => { req.clone() }
+			Some((id, ref req)) if ctx.req_id() == &id => { req.clone() }
 			other => {
 				self.pending_req = other;
 				return SyncRound::Start(self);
@@ -445,9 +442,9 @@ impl SyncRound {
 		}
 	}
 
-	/// Drain up to a maximum number of headers (continuous, starting with a child of
+	/// Drain up to a maximum number (None -> all) of headers (continuous, starting with a child of
 	/// the round start block) from the round, starting a new one once finished.
-	pub fn drain(self, v: &mut Vec<Header>, max: usize) -> Self {
+	pub fn drain(self, v: &mut Vec<Header>, max: Option<usize>) -> Self {
 		match self {
 			SyncRound::Fetch(fetcher) => fetcher.drain(v, max),
 			other => other,