dispatch header requests

Cargo.lock

@@ -522,6 +522,7 @@ dependencies = [
  "ethcore-util 1.5.0",
  "futures 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand 0.3.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "rlp 0.1.0",
  "smallvec 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "time 0.1.35 (registry+https://github.com/rust-lang/crates.io-index)",

ethcore/light/Cargo.toml

@@ -21,6 +21,7 @@ rlp = { path = "../../util/rlp" }
 time = "0.1"
 smallvec = "0.3.1"
 futures = "0.1"
+rand = "0.3"
 
 [features]
 default = []

ethcore/light/src/lib.rs

@@ -66,6 +66,7 @@ extern crate rlp;
 extern crate smallvec;
 extern crate time;
 extern crate futures;
+extern crate rand;
 
 #[cfg(feature = "ipc")]
 extern crate ethcore_ipc as ipc;

ethcore/light/src/on_demand/mod.rs

@@ -20,22 +20,65 @@
 
 use std::collections::HashMap;
 
-use ethcore::ids::BlockId;
-use ethcore::block::Block;
 use ethcore::encoded;
-use ethcore::header::Header;
 use ethcore::receipt::Receipt;
 
-use futures::Future;
+use futures::{Async, Poll, Future};
-use futures::sync::oneshot::{self, Sender, Receiver};
+use futures::sync::oneshot;
 use network::PeerId;
 
 use client::Client;
 use net::{Handler, Status, Capabilities, Announcement, EventContext, BasicContext, ReqId};
-use util::{Address, H256, RwLock};
+use util::{Address, H256, U256, RwLock};
+use request as les_request;
 
-/// Dummy type for "basic account"
+/// Basic account data.
-pub struct Account;
+// TODO: [rob] unify with similar struct in `snapshot`.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Account {
+	/// Balance in Wei
+	pub balance: U256,
+	/// Storage trie root.
+	pub storage_root: H256,
+	/// Code hash
+	pub code_hash: H256,
+	/// Nonce
+	pub nonce: U256,
+}
+
+/// Errors which can occur while trying to fulfill a request.
+pub enum Error {
+	/// Request was canceled.
+	Canceled,
+	/// No suitable peers available to serve the request.
+	NoPeersAvailable,
+	/// Request timed out.
+	TimedOut,
+}
+
+impl From<oneshot::Canceled> for Error {
+	fn from(_: oneshot::Canceled) -> Self {
+		Error::Canceled
+	}
+}
+
+/// Future which awaits a response to an on-demand request.
+pub struct Response<T>(oneshot::Receiver<Result<T, Error>>);
+
+impl<T> Future for Response<T> {
+	type Item = T;
+	type Error = Error;
+
+	fn poll(&mut self) -> Poll<T, Error> {
+		match self.0.poll().map_err(Into::into) {
+			Ok(Async::Ready(val)) => val.map(Async::Ready),
+			Ok(Async::NotReady) => Ok(Async::NotReady),
+			Err(e) => Err(e),
+		}
+	}
+}
+
+type Sender<T> = oneshot::Sender<Result<T, Error>>;
 
 // relevant peer info.
 struct Peer {
@@ -68,60 +111,146 @@ impl Handler for OnDemand {
 
 	fn on_disconnect(&self, ctx: &EventContext, unfulfilled: &[ReqId]) {
 		self.peers.write().remove(&ctx.peer());
+
+		for unfulfilled in unfulfilled {
+			if let Some(pending) = self.pending_requests.write().remove(unfulfilled) {
+				trace!(target: "on_demand", "Attempting to reassign dropped request");
+				self.dispatch_request(ctx.as_basic(), pending);
+			}
+		}
+	}
+
+	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);
+		}
 	}
 }
 
 impl OnDemand {
 	/// Request a header by block number and CHT root hash.
-	pub fn header_by_number(&self, ctx: &BasicContext, num: u64, cht_root: H256) -> Receiver<encoded::Header> {
+	pub fn header_by_number(&self, ctx: &BasicContext, num: u64, cht_root: H256) -> Response<encoded::Header> {
 		let (sender, receiver) = oneshot::channel();
 		self.dispatch_request(ctx, Request::HeaderByNumber(num, cht_root, sender));
-		receiver
+		Response(receiver)
 	}
 
 	/// Request a header by hash. This is less accurate than by-number because we don't know
 	/// where in the chain this header lies, and therefore can't find a peer who is supposed to have
 	/// it as easily.
-	pub fn header_by_hash(&self, ctx: &BasicContext, hash: H256) -> Receiver<encoded::Header> {
+	pub fn header_by_hash(&self, ctx: &BasicContext, hash: H256) -> Response<encoded::Header> {
 		let (sender, receiver) = oneshot::channel();
 		self.dispatch_request(ctx, Request::HeaderByHash(hash, sender));
-		receiver
+		Response(receiver)
 	}
 
 	/// Request a block, given its header. Block bodies are requestable by hash only,
 	/// and the header is required anyway to verify and complete the block body
 	/// -- this just doesn't obscure the network query.
-	pub fn block(&self, ctx: &BasicContext, header: encoded::Header) -> Receiver<encoded::Block> {
+	pub fn block(&self, ctx: &BasicContext, header: encoded::Header) -> Response<encoded::Block> {
 		let (sender, receiver) = oneshot::channel();
 		self.dispatch_request(ctx, Request::Block(header, sender));
-		receiver
+		Response(receiver)
 	}
 
 	/// Request the receipts for a block. The header serves two purposes:
 	/// provide the block hash to fetch receipts for, and for verification of the receipts root.
-	pub fn block_receipts(&self, ctx: &BasicContext, header: encoded::Header) -> Receiver<Vec<Receipt>> {
+	pub fn block_receipts(&self, ctx: &BasicContext, header: encoded::Header) -> Response<Vec<Receipt>> {
 		let (sender, receiver) = oneshot::channel();
 		self.dispatch_request(ctx, Request::BlockReceipts(header, sender));
-		receiver
+		Response(receiver)
 	}
 
 	/// Request an account by address and block header -- which gives a hash to query and a state root
 	/// to verify against.
-	pub fn account(&self, ctx: &BasicContext, header: encoded::Header, address: Address) -> Receiver<Account> {
+	pub fn account(&self, ctx: &BasicContext, header: encoded::Header, address: Address) -> Response<Account> {
 		let (sender, receiver) = oneshot::channel();
 		self.dispatch_request(ctx, Request::Account(header, address, sender));
-		receiver
+		Response(receiver)
 	}
 
 	/// Request account storage value by block header, address, and key.
-	pub fn storage(&self, ctx: &BasicContext, header: encoded::Header, address: Address, key: H256) -> Receiver<H256> {
+	pub fn storage(&self, ctx: &BasicContext, header: encoded::Header, address: Address, key: H256) -> Response<H256> {
 		let (sender, receiver) = oneshot::channel();
 		self.dispatch_request(ctx, Request::Storage(header, address, key, sender));
-		receiver
+		Response(receiver)
 	}
 
 	// dispatch a request to a suitable peer.
 	fn dispatch_request(&self, ctx: &BasicContext, request: Request) {
-		unimplemented!()
+		match request {
+			Request::HeaderByNumber(num, cht_hash, sender) => {
+				let cht_num = ::client::cht::block_to_cht_number(num);
+				let req = les_request::Request::HeaderProofs(les_request::HeaderProofs {
+					requests: vec![les_request::HeaderProof {
+						cht_number: cht_num,
+						block_number: num,
+						from_level: 0,
+					}],
+				});
+
+				// we're looking for a peer with serveHeaders who's far enough along in the
+				// chain.
+				for (id, peer) in self.peers.read().iter() {
+					if peer.capabilities.serve_headers && peer.status.head_num >= num {
+						match ctx.request_from(*id, req.clone()) {
+							Ok(req_id) => {
+								trace!(target: "on_demand", "Assigning request to peer {}", id);
+								self.pending_requests.write().insert(
+									req_id,
+									Request::HeaderByNumber(num, cht_hash, sender)
+								);
+								return;
+							},
+							Err(e) =>
+								trace!(target: "on_demand", "Failed to make request of peer {}: {:?}", id, e),
+						}
+					}
+				}
+
+				// TODO: retrying.
+				trace!(target: "on_demand", "No suitable peer for request");
+				sender.complete(Err(Error::NoPeersAvailable));
+			}
+			Request::HeaderByHash(hash, sender) => {
+				let req = les_request::Request::Headers(les_request::Headers {
+					start: hash.into(),
+					max: 1,
+					skip: 0,
+					reverse: false,
+				});
+
+				// all we've got is a hash, so we'll just guess at peers who might have
+				// it randomly.
+				let mut potential_peers = self.peers.read().iter()
+					.filter(|&(_, peer)| peer.capabilities.serve_headers)
+					.map(|(id, _)| *id)
+					.collect::<Vec<_>>();
+
+				let mut rng = ::rand::thread_rng();
+
+				::rand::Rng::shuffle(&mut rng, &mut potential_peers);
+
+				for id in potential_peers {
+					match ctx.request_from(id, req.clone()) {
+						Ok(req_id) => {
+							trace!(target: "on_demand", "Assigning request to peer {}", id);
+							self.pending_requests.write().insert(
+								req_id,
+								Request::HeaderByHash(hash, sender),
+							);
+							return;
+						}
+						Err(e) =>
+							trace!(target: "on_demand", "Failed to make request of peer {}: {:?}", id, e),
+					}
+				}
+
+				sender.complete(Err(Error::NoPeersAvailable));
+			}
+			_ => unimplemented!()
+		}
 	}
 }