Refactor price_info (#6003)

* refactor PriceInfo to use Fetch and reuse the client

* forget Fetch future to keep it running in the background

* update Debug message for price_info::Client

* wrap underlying errors in price_info client

* use debug_struct in price_info client debug implementation

* use global fetch service in price_info client

* rename gas_pricer parameter in RunCmd

* move price_info to its own crate

* fix price_info tests

* replace rustc_serialize with serde_json in price_info

* add documentation for price_info

* remove unused rustc-serialize dependency from ethcore

* fix price_info formatting

* re-export fetch crate in price_info

* remove unused cfg attributes in price_info

* add tests for price_info

Cargo.lock

@@ -475,11 +475,11 @@ dependencies = [
  "native-contracts 0.1.0",
  "num 0.1.32 (registry+https://github.com/rust-lang/crates.io-index)",
  "num_cpus 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "price-info 1.7.0",
  "rand 0.3.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "rlp 0.2.0",
  "rust-crypto 0.2.36 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-hex 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "rustc-serialize 0.3.19 (registry+https://github.com/rust-lang/crates.io-index)",
  "semver 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "stats 0.1.0",
  "time 0.1.35 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -667,7 +667,7 @@ dependencies = [
  "ethcrypto 0.1.0",
  "ethkey 0.2.0",
  "futures 0.1.11 (registry+https://github.com/rust-lang/crates.io-index)",
- "futures-cpupool 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "futures-cpupool 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "hyper 0.10.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "native-contracts 0.1.0",
@@ -900,7 +900,7 @@ name = "fetch"
 version = "0.1.0"
 dependencies = [
  "futures 0.1.11 (registry+https://github.com/rust-lang/crates.io-index)",
- "futures-cpupool 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "futures-cpupool 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "mime 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -933,10 +933,9 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "futures-cpupool"
-version = "0.1.2"
+version = "0.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "crossbeam 0.2.10 (registry+https://github.com/rust-lang/crates.io-index)",
  "futures 0.1.11 (registry+https://github.com/rust-lang/crates.io-index)",
  "num_cpus 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1741,7 +1740,7 @@ dependencies = [
  "ethsync 1.8.0",
  "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)",
- "futures-cpupool 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "futures-cpupool 0.1.5 (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 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1785,7 +1784,7 @@ dependencies = [
  "ethcore-util 1.8.0",
  "fetch 0.1.0",
  "futures 0.1.11 (registry+https://github.com/rust-lang/crates.io-index)",
- "futures-cpupool 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "futures-cpupool 0.1.5 (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)",
  "jsonrpc-http-server 7.0.0 (git+https://github.com/paritytech/jsonrpc.git?branch=parity-1.7)",
  "linked-hash-map 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1897,7 +1896,7 @@ dependencies = [
  "evm 0.1.0",
  "fetch 0.1.0",
  "futures 0.1.11 (registry+https://github.com/rust-lang/crates.io-index)",
- "futures-cpupool 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "futures-cpupool 0.1.5 (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)",
  "jsonrpc-http-server 7.0.0 (git+https://github.com/paritytech/jsonrpc.git?branch=parity-1.7)",
  "jsonrpc-ipc-server 7.0.0 (git+https://github.com/paritytech/jsonrpc.git?branch=parity-1.7)",
@@ -2131,6 +2130,17 @@ dependencies = [
  "difference 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "price-info"
+version = "1.7.0"
+dependencies = [
+ "ethcore-util 1.7.0",
+ "fetch 0.1.0",
+ "futures 0.1.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "log 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde_json 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "primal"
 version = "0.2.3"
@@ -3164,7 +3174,7 @@ dependencies = [
 "checksum fnv 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)" = "6cc484842f1e2884faf56f529f960cc12ad8c71ce96cc7abba0a067c98fee344"
 "checksum foreign-types 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "3e4056b9bd47f8ac5ba12be771f77a0dae796d1bbaaf5fd0b9c2d38b69b8a29d"
 "checksum futures 0.1.11 (registry+https://github.com/rust-lang/crates.io-index)" = "8e51e7f9c150ba7fd4cee9df8bf6ea3dea5b63b68955ddad19ccd35b71dcfb4d"
-"checksum futures-cpupool 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "bb982bb25cd8fa5da6a8eb3a460354c984ff1113da82bcb4f0b0862b5795db82"
+"checksum futures-cpupool 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "a283c84501e92cade5ea673a2a7ca44f71f209ccdd302a3e0896f50083d2c5ff"
 "checksum gcc 0.3.51 (registry+https://github.com/rust-lang/crates.io-index)" = "120d07f202dcc3f72859422563522b66fe6463a4c513df062874daad05f85f0a"
 "checksum gdi32-sys 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "0912515a8ff24ba900422ecda800b52f4016a56251922d397c576bf92c690518"
 "checksum getopts 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)" = "d9047cfbd08a437050b363d35ef160452c5fe8ea5187ae0a624708c91581d685"

ethcore/Cargo.toml

@@ -44,11 +44,11 @@ lru-cache = "0.1.0"
 native-contracts = { path = "native_contracts" }
 num = "0.1"
 num_cpus = "1.2"
+price-info = { path = "../price-info" }
 rand = "0.3"
 rlp = { path = "../util/rlp" }
 rust-crypto = "0.2.34"
 rustc-hex = "1.0"
-rustc-serialize = "0.3"
 semver = "0.6"
 stats = { path = "../util/stats" }
 time = "0.1"

ethcore/src/lib.rs

@@ -98,10 +98,10 @@ extern crate lru_cache;
 extern crate native_contracts;
 extern crate num_cpus;
 extern crate num;
+extern crate price_info;
 extern crate rand;
 extern crate rlp;
 extern crate rustc_hex;
-extern crate rustc_serialize;
 extern crate semver;
 extern crate stats;
 extern crate time;

ethcore/src/miner/miner.rs

@@ -33,9 +33,10 @@ use miner::{MinerService, MinerStatus, TransactionQueue, RemovalReason, Transact
 	AccountDetails, TransactionOrigin};
 use miner::banning_queue::{BanningTransactionQueue, Threshold};
 use miner::work_notify::{WorkPoster, NotifyWork};
-use miner::price_info::PriceInfo;
 use miner::local_transactions::{Status as LocalTransactionStatus};
 use miner::service_transaction_checker::ServiceTransactionChecker;
+use price_info::{Client as PriceInfoClient, PriceInfo};
+use price_info::fetch::Client as FetchClient;
 use header::BlockNumber;
 
 /// Different possible definitions for pending transaction set.
@@ -154,6 +155,7 @@ pub struct GasPriceCalibratorOptions {
 pub struct GasPriceCalibrator {
 	options: GasPriceCalibratorOptions,
 	next_calibration: Instant,
+	price_info: PriceInfoClient,
 }
 
 impl GasPriceCalibrator {
@@ -163,7 +165,7 @@ impl GasPriceCalibrator {
 			let usd_per_tx = self.options.usd_per_tx;
 			trace!(target: "miner", "Getting price info");
 
-			PriceInfo::get(move |price: PriceInfo| {
+			self.price_info.get(move |price: PriceInfo| {
 				trace!(target: "miner", "Price info arrived: {:?}", price);
 				let usd_per_eth = price.ethusd;
 				let wei_per_usd: f32 = 1.0e18 / usd_per_eth;
@@ -189,10 +191,11 @@ pub enum GasPricer {
 
 impl GasPricer {
 	/// Create a new Calibrated `GasPricer`.
-	pub fn new_calibrated(options: GasPriceCalibratorOptions) -> GasPricer {
+	pub fn new_calibrated(options: GasPriceCalibratorOptions, fetch: FetchClient) -> GasPricer {
 		GasPricer::Calibrated(GasPriceCalibrator {
 			options: options,
 			next_calibration: Instant::now(),
+			price_info: PriceInfoClient::new(fetch),
 		})
 	}
 

ethcore/src/miner/mod.rs

@@ -45,7 +45,6 @@ mod banning_queue;
 mod external;
 mod local_transactions;
 mod miner;
-mod price_info;
 mod service_transaction_checker;
 mod transaction_queue;
 mod work_notify;

ethcore/src/miner/price_info.rs

@@ -1,125 +0,0 @@
-// 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/>.
-
-use rustc_serialize::json::Json;
-use std::thread;
-use std::io::Read;
-use std::time::Duration;
-use std::str::FromStr;
-use std::sync::mpsc;
-use hyper::client::{Handler, Request, Response, Client};
-use hyper::{Url, Next, Encoder, Decoder};
-use hyper::net::HttpStream;
-
-#[derive(Debug)]
-pub struct PriceInfo {
-	pub ethusd: f32,
-}
-
-pub struct SetPriceHandler<F> {
-	set_price: F,
-	channel: mpsc::Sender<()>,
-}
-
-impl<F> Drop for SetPriceHandler<F> {
-	fn drop(&mut self) {
-		let _ = self.channel.send(());
-	}
-}
-
-impl<F: Fn(PriceInfo) + Sync + Send + 'static> Handler<HttpStream> for SetPriceHandler<F> {
-	fn on_request(&mut self, _: &mut Request) -> Next { Next::read().timeout(Duration::from_secs(3)) }
-	fn on_request_writable(&mut self, _: &mut Encoder<HttpStream>) -> Next { Next::read().timeout(Duration::from_secs(3)) }
-	fn on_response(&mut self, _: Response) -> Next { Next::read().timeout(Duration::from_secs(3)) }
-
-	fn on_response_readable(&mut self, r: &mut Decoder<HttpStream>) -> Next {
-		let mut body = String::new();
-		let info = r.read_to_string(&mut body)
-			.map_err(|e| format!("Unable to read response: {:?}", e))
-			.and_then(|_| self.process_response(&body));
-
-		if let Err(e) = info {
-			warn!("Failed to auto-update latest ETH price: {:?}", e);
-		}
-		Next::end()
-	}
-}
-
-impl<F: Fn(PriceInfo) + Sync + Send + 'static> SetPriceHandler<F> {
-	fn process_response(&self, body: &str) -> Result<(), String> {
-		let json = Json::from_str(body).map_err(|e| format!("Invalid JSON returned: {:?}", e))?;
-		let obj = json.find_path(&["result", "ethusd"]).ok_or("USD price not found".to_owned())?;
-		let ethusd = match *obj {
-			Json::String(ref s) => FromStr::from_str(s).ok(),
-			_ => None,
-		}.ok_or("Unexpected price format.".to_owned())?;
-
-		(self.set_price)(PriceInfo {
-			ethusd: ethusd,
-		});
-		Ok(())
-	}
-}
-
-impl PriceInfo {
-	pub fn get<F: Fn(PriceInfo) + Sync + Send + 'static>(set_price: F) {
-		thread::spawn(move || {
-			let url = FromStr::from_str("http://api.etherscan.io/api?module=stats&action=ethprice")
-				.expect("string known to be a valid URL; qed");
-
-			if let Err(e) = Self::request(url, set_price) {
-				warn!("Failed to auto-update latest ETH price: {:?}", e);
-			}
-		});
-	}
-
-	fn request<F: Fn(PriceInfo) + Send + Sync + 'static>(url: Url, set_price: F) -> Result<(), String> {
-		let (tx, rx) = mpsc::channel();
-		let client = Client::new().map_err(|e| format!("Unable to start client: {:?}", e))?;
-
-		client.request(
-			url,
-			SetPriceHandler {
-				set_price: set_price,
-				channel: tx,
-			},
-		).map_err(|_| "Request failed.".to_owned())?;
-
-		// Wait for exit
-		let _ = rx.recv().map_err(|e| format!("Request interrupted: {:?}", e))?;
-		client.close();
-
-		Ok(())
-	}
-}
-
-#[test] #[ignore]
-fn should_get_price_info() {
-	use std::sync::Arc;
-	use std::time::Duration;
-	use ethcore_logger::init_log;
-	use util::{Condvar, Mutex};
-
-	init_log();
-	let done = Arc::new((Mutex::new(PriceInfo { ethusd: 0f32 }), Condvar::new()));
-	let rdone = done.clone();
-
-	PriceInfo::get(move |price| { let mut p = rdone.0.lock(); *p = price; rdone.1.notify_one(); });
-	let mut p = done.0.lock();
-	let t = done.1.wait_for(&mut p, Duration::from_millis(10000));
-	assert!(!t.timed_out());
-	assert!(p.ethusd != 0f32);
-}

parity/configuration.rs

@@ -333,7 +333,7 @@ impl Configuration {
 			let verifier_settings = self.verifier_settings();
 
 			// Special presets are present for the dev chain.
-			let (gas_pricer, miner_options) = match spec {
+			let (gas_pricer_conf, miner_options) = match spec {
 				SpecType::Dev => (GasPricerConfig::Fixed(0.into()), self.miner_options(0)?),
 				_ => (self.gas_pricer_config()?, self.miner_options(self.args.flag_reseal_min_period)?),
 			};
@@ -356,7 +356,7 @@ impl Configuration {
 				net_conf: net_conf,
 				network_id: network_id,
 				acc_conf: self.accounts_config()?,
-				gas_pricer: gas_pricer,
+				gas_pricer_conf: gas_pricer_conf,
 				miner_extras: self.miner_extras()?,
 				stratum: self.stratum_options()?,
 				update_policy: update_policy,
@@ -1309,7 +1309,7 @@ mod tests {
 			public_node: false,
 			warp_sync: true,
 			acc_conf: Default::default(),
-			gas_pricer: Default::default(),
+			gas_pricer_conf: Default::default(),
 			miner_extras: Default::default(),
 			update_policy: UpdatePolicy { enable_downloading: true, require_consensus: true, filter: UpdateFilter::Critical, track: ReleaseTrack::Unknown, path: default_hypervisor_path() },
 			mode: Default::default(),
@@ -1604,7 +1604,7 @@ mod tests {
 		let conf = parse(&args);
 		match conf.into_command().unwrap().cmd {
 			Cmd::Run(c) => {
-				assert_eq!(c.gas_pricer, GasPricerConfig::Fixed(0.into()));
+				assert_eq!(c.gas_pricer_conf, GasPricerConfig::Fixed(0.into()));
 				assert_eq!(c.miner_options.reseal_min_period, Duration::from_millis(0));
 			},
 			_ => panic!("Should be Cmd::Run"),

parity/main.rs

@@ -366,4 +366,3 @@ fn main() {
 		process::exit(main_direct(can_restart));
 	}
 }
-

parity/params.rs

@@ -22,6 +22,7 @@ use ethcore::spec::Spec;
 use ethcore::ethereum;
 use ethcore::client::Mode;
 use ethcore::miner::{GasPricer, GasPriceCalibratorOptions};
+use hash_fetch::fetch::Client as FetchClient;
 use user_defaults::UserDefaults;
 
 #[derive(Debug, PartialEq)]
@@ -226,15 +227,18 @@ impl Default for GasPricerConfig {
 	}
 }
 
-impl Into<GasPricer> for GasPricerConfig {
+impl GasPricerConfig {
-	fn into(self) -> GasPricer {
+	pub fn to_gas_pricer(&self, fetch: FetchClient) -> GasPricer {
-		match self {
+		match *self {
 			GasPricerConfig::Fixed(u) => GasPricer::Fixed(u),
 			GasPricerConfig::Calibrated { usd_per_tx, recalibration_period, .. } => {
-				GasPricer::new_calibrated(GasPriceCalibratorOptions {
+				GasPricer::new_calibrated(
-					usd_per_tx: usd_per_tx,
+					GasPriceCalibratorOptions {
-					recalibration_period: recalibration_period,
+						usd_per_tx: usd_per_tx,
-				})
+						recalibration_period: recalibration_period,
+					},
+					fetch
+				)
 			}
 		}
 	}

parity/run.rs

@@ -88,7 +88,7 @@ pub struct RunCmd {
 	pub warp_sync: bool,
 	pub public_node: bool,
 	pub acc_conf: AccountsConfig,
-	pub gas_pricer: GasPricerConfig,
+	pub gas_pricer_conf: GasPricerConfig,
 	pub miner_extras: MinerExtras,
 	pub update_policy: UpdatePolicy,
 	pub mode: Option<Mode>,
@@ -480,9 +480,12 @@ pub fn execute(cmd: RunCmd, can_restart: bool, logger: Arc<RotatingLogger>) -> R
 	// prepare account provider
 	let account_provider = Arc::new(prepare_account_provider(&cmd.spec, &cmd.dirs, &spec.data_dir, cmd.acc_conf, &passwords)?);
 
+	// fetch service
+	let fetch = FetchClient::new().map_err(|e| format!("Error starting fetch client: {:?}", e))?;
+
 	// create miner
-	let initial_min_gas_price = cmd.gas_pricer.initial_min();
+	let initial_min_gas_price = cmd.gas_pricer_conf.initial_min();
-	let miner = Miner::new(cmd.miner_options, cmd.gas_pricer.into(), &spec, Some(account_provider.clone()));
+	let miner = Miner::new(cmd.miner_options, cmd.gas_pricer_conf.to_gas_pricer(fetch.clone()), &spec, Some(account_provider.clone()));
 	miner.set_author(cmd.miner_extras.author);
 	miner.set_gas_floor_target(cmd.miner_extras.gas_floor_target);
 	miner.set_gas_ceil_target(cmd.miner_extras.gas_ceil_target);
@@ -637,9 +640,6 @@ pub fn execute(cmd: RunCmd, can_restart: bool, logger: Arc<RotatingLogger>) -> R
 	// spin up event loop
 	let event_loop = EventLoop::spawn();
 
-	// fetch service
-	let fetch = FetchClient::new().map_err(|e| format!("Error starting fetch client: {:?}", e))?;
-
 	// the updater service
 	let updater = Updater::new(
 		Arc::downgrade(&(service.client() as Arc<BlockChainClient>)),

price-info/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+description = "Fetch current ETH price"
+homepage = "http://parity.io"
+license = "GPL-3.0"
+name = "price-info"
+version = "1.7.0"
+authors = ["Parity Technologies <admin@parity.io>"]
+
+[dependencies]
+fetch = { path = "../util/fetch" }
+futures = "0.1"
+log = "0.3"
+serde_json = "1.0"
+
+[dev-dependencies]
+ethcore-util = { path = "../util" }

price-info/src/lib.rs

@@ -0,0 +1,31 @@
+// 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/>.
+
+#![warn(missing_docs)]
+
+//! A simple client to get the current ETH price using an external API.
+
+extern crate futures;
+extern crate serde_json;
+
+#[macro_use]
+extern crate log;
+
+pub extern crate fetch;
+
+mod price_info;
+
+pub use price_info::*;

price-info/src/price_info.rs

@@ -0,0 +1,222 @@
+// 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/>.
+
+use std::cmp;
+use std::fmt;
+use std::io;
+use std::io::Read;
+use std::str::FromStr;
+
+use fetch;
+use fetch::{Client as FetchClient, Fetch};
+use futures::Future;
+use serde_json;
+use serde_json::Value;
+
+/// Current ETH price information.
+#[derive(Debug)]
+pub struct PriceInfo {
+	/// Current ETH price in USD.
+	pub ethusd: f32,
+}
+
+/// Price info error.
+#[derive(Debug)]
+pub enum Error {
+	/// The API returned an unexpected status code or content.
+	UnexpectedResponse(&'static str, String),
+	/// There was an error when trying to reach the API.
+	Fetch(fetch::Error),
+	/// IO error when reading API response.
+	Io(io::Error),
+}
+
+impl From<io::Error> for Error {
+	fn from(err: io::Error) -> Self { Error::Io(err) }
+}
+
+impl From<fetch::Error> for Error {
+	fn from(err: fetch::Error) -> Self { Error::Fetch(err) }
+}
+
+/// A client to get the current ETH price using an external API.
+pub struct Client<F = FetchClient> {
+	api_endpoint: String,
+	fetch: F,
+}
+
+impl<F> fmt::Debug for Client<F> {
+	fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+		fmt.debug_struct("price_info::Client")
+		   .field("api_endpoint", &self.api_endpoint)
+		   .finish()
+	}
+}
+
+impl<F> cmp::PartialEq for Client<F> {
+	fn eq(&self, other: &Client<F>) -> bool {
+		self.api_endpoint == other.api_endpoint
+	}
+}
+
+impl<F: Fetch> Client<F> {
+	/// Creates a new instance of the `Client` given a `fetch::Client`.
+	pub fn new(fetch: F) -> Client<F> {
+		let api_endpoint = "http://api.etherscan.io/api?module=stats&action=ethprice".to_owned();
+		Client { api_endpoint, fetch }
+	}
+
+	/// Gets the current ETH price and calls `set_price` with the result.
+	pub fn get<G: Fn(PriceInfo) + Sync + Send + 'static>(&self, set_price: G) {
+		self.fetch.forget(self.fetch.fetch(&self.api_endpoint)
+			.map_err(|err| Error::Fetch(err))
+			.and_then(move |mut response| {
+				let mut result = String::new();
+				response.read_to_string(&mut result)?;
+
+				if response.is_success() {
+					let value: Result<Value, _> = serde_json::from_str(&result);
+					if let Ok(v) = value {
+						let obj = v.pointer("/result/ethusd").and_then(|obj| {
+							match *obj {
+								Value::String(ref s) => FromStr::from_str(s).ok(),
+								_ => None,
+							}
+						});
+
+						if let Some(ethusd) = obj {
+							set_price(PriceInfo { ethusd });
+							return Ok(());
+						}
+					}
+				}
+
+				let status = response.status().canonical_reason().unwrap_or("unknown");
+				Err(Error::UnexpectedResponse(status, result))
+			})
+			.map_err(|err| {
+				warn!("Failed to auto-update latest ETH price: {:?}", err);
+				err
+			})
+		);
+	}
+}
+
+#[cfg(test)]
+mod test {
+	extern crate ethcore_util as util;
+
+	use self::util::Mutex;
+	use std::sync::Arc;
+	use std::sync::atomic::{AtomicBool, Ordering};
+	use fetch;
+	use fetch::Fetch;
+	use futures;
+	use futures::future::{Future, FutureResult};
+	use price_info::Client;
+
+	#[derive(Clone)]
+	struct FakeFetch(Option<String>, Arc<Mutex<u64>>);
+	impl Fetch for FakeFetch {
+		type Result = FutureResult<fetch::Response, fetch::Error>;
+		fn new() -> Result<Self, fetch::Error> where Self: Sized { Ok(FakeFetch(None, Default::default())) }
+		fn fetch_with_abort(&self, url: &str, _abort: fetch::Abort) -> Self::Result {
+			assert_eq!(url, "http://api.etherscan.io/api?module=stats&action=ethprice");
+			let mut val = self.1.lock();
+			*val = *val + 1;
+			if let Some(ref response) = self.0 {
+				let data = ::std::io::Cursor::new(response.clone());
+				futures::future::ok(fetch::Response::from_reader(data))
+			} else {
+				futures::future::ok(fetch::Response::not_found())
+			}
+		}
+
+		// this guarantees that the calls to price_info::Client::get will block for execution
+		fn forget<F, I, E>(&self, f: F) where
+			F: Future<Item=I, Error=E> + Send + 'static,
+			I: Send + 'static,
+			E: Send + 'static {
+			let _ = f.wait();
+		}
+	}
+
+	fn price_info_ok(response: &str) -> Client<FakeFetch> {
+		Client::new(FakeFetch(Some(response.to_owned()), Default::default()))
+	}
+
+	fn price_info_not_found() -> Client<FakeFetch> {
+		Client::new(FakeFetch::new().unwrap())
+	}
+
+	#[test]
+	fn should_get_price_info() {
+		// given
+		let response = r#"{
+			"status": "1",
+			"message": "OK",
+			"result": {
+				"ethbtc": "0.0891",
+				"ethbtc_timestamp": "1499894236",
+				"ethusd": "209.55",
+				"ethusd_timestamp": "1499894229"
+			}
+		}"#;
+
+		let price_info = price_info_ok(response);
+
+		// when
+		price_info.get(|price| {
+
+			// then
+			assert_eq!(price.ethusd, 209.55);
+		});
+	}
+
+	#[test]
+	fn should_not_call_set_price_if_response_is_malformed() {
+		// given
+		let response = "{}";
+
+		let price_info = price_info_ok(response);
+		let b = Arc::new(AtomicBool::new(false));
+
+		// when
+		let bb = b.clone();
+		price_info.get(move |_| {
+			bb.store(true, Ordering::Relaxed);
+		});
+
+		// then
+		assert_eq!(b.load(Ordering::Relaxed), false);
+	}
+
+	#[test]
+	fn should_not_call_set_price_if_response_is_invalid() {
+		// given
+		let price_info = price_info_not_found();
+		let b = Arc::new(AtomicBool::new(false));
+
+		// when
+		let bb = b.clone();
+		price_info.get(move |_| {
+			bb.store(true, Ordering::Relaxed);
+		});
+
+		// then
+		assert_eq!(b.load(Ordering::Relaxed), false);
+	}
+}

util/fetch/src/client.rs

@@ -61,6 +61,14 @@ pub trait Fetch: Clone + Send + Sync + 'static {
 		f.boxed()
 	}
 
+	/// Spawn the future in context of this `Fetch` thread pool as "fire and forget", i.e. dropping this future without
+	/// canceling the underlying future.
+	/// Implementation is optional.
+	fn forget<F, I, E>(&self, _: F) where
+		F: Future<Item=I, Error=E> + Send + 'static,
+		I: Send + 'static,
+		E: Send + 'static {}
+
 	/// Fetch URL and get a future for the result.
 	/// Supports aborting the request in the middle of execution.
 	fn fetch_with_abort(&self, url: &str, abort: Abort) -> Self::Result;
@@ -149,6 +157,14 @@ impl Fetch for Client {
 		self.pool.spawn(f).boxed()
 	}
 
+	fn forget<F, I, E>(&self, f: F) where
+		F: Future<Item=I, Error=E> + Send + 'static,
+		I: Send + 'static,
+		E: Send + 'static,
+	{
+		self.pool.spawn(f).forget()
+	}
+
 	fn fetch_with_abort(&self, url: &str, abort: Abort) -> Self::Result {
 		debug!(target: "fetch", "Fetching from: {:?}", url);