refactor(fetch) : light use only one DNS thread (#9647)

* refactor(fetch) : light use only one `DNS` thread

* grumbles(fetch) : pass number of threads directly

parity/run.rs

@@ -77,7 +77,13 @@ const SNAPSHOT_HISTORY: u64 = 100;
 const GAS_CORPUS_EXPIRATION_MINUTES: u64 = 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.";
+const VERIFY_PASSWORD_HINT: &str = "Make sure valid password is present in files passed using `--password` or in the configuration file.";
+
+// Full client number of DNS threads
+const FETCH_FULL_NUM_DNS_THREADS: usize = 4;
+
+// Light client number of DNS threads
+const FETCH_LIGHT_NUM_DNS_THREADS: usize = 1;
 
 #[derive(Debug, PartialEq)]
 pub struct RunCmd {
@@ -283,7 +289,7 @@ fn execute_light_impl(cmd: RunCmd, logger: Arc<RotatingLogger>) -> Result<Runnin
 	let cpu_pool = CpuPool::new(4);
 
 	// fetch service
-	let fetch = fetch::Client::new().map_err(|e| format!("Error starting fetch client: {:?}", e))?;
+	let fetch = fetch::Client::new(FETCH_LIGHT_NUM_DNS_THREADS).map_err(|e| format!("Error starting fetch client: {:?}", e))?;
 	let passwords = passwords_from_files(&cmd.acc_conf.password_files)?;
 
 	// prepare account provider
@@ -477,7 +483,7 @@ fn execute_impl<Cr, Rr>(cmd: RunCmd, logger: Arc<RotatingLogger>, on_client_rq:
 	let event_loop = EventLoop::spawn();
 
 	// fetch service
-	let fetch = fetch::Client::new().map_err(|e| format!("Error starting fetch client: {:?}", e))?;
+	let fetch = fetch::Client::new(FETCH_FULL_NUM_DNS_THREADS).map_err(|e| format!("Error starting fetch client: {:?}", e))?;
 
 	let txpool_size = cmd.miner_options.pool_limits.max_count;
 	// create miner

util/fetch/src/client.rs

@@ -170,11 +170,11 @@ impl Drop for Client {
 
 impl Client {
 	/// Create a new fetch client.
-	pub fn new() -> Result<Self, Error> {
+	pub fn new(num_dns_threads: usize) -> Result<Self, Error> {
 		let (tx_start, rx_start) = std::sync::mpsc::sync_channel(1);
 		let (tx_proto, rx_proto) = mpsc::channel(64);
 
-		Client::background_thread(tx_start, rx_proto)?;
+		Client::background_thread(tx_start, rx_proto, num_dns_threads)?;
 
 		match rx_start.recv_timeout(Duration::from_secs(10)) {
 			Err(RecvTimeoutError::Timeout) => {
@@ -199,7 +199,7 @@ impl Client {
 		})
 	}
 
-	fn background_thread(tx_start: TxStartup, rx_proto: mpsc::Receiver<ChanItem>) -> io::Result<thread::JoinHandle<()>> {
+	fn background_thread(tx_start: TxStartup, rx_proto: mpsc::Receiver<ChanItem>, num_dns_threads: usize) -> io::Result<thread::JoinHandle<()>> {
 		thread::Builder::new().name("fetch".into()).spawn(move || {
 			let mut core = match reactor::Core::new() {
 				Ok(c) => c,
@@ -208,7 +208,7 @@ impl Client {
 
 			let handle = core.handle();
 			let hyper = hyper::Client::configure()
-				.connector(hyper_rustls::HttpsConnector::new(4, &core.handle()))
+				.connector(hyper_rustls::HttpsConnector::new(num_dns_threads, &core.handle()))
 				.build(&core.handle());
 
 			let future = rx_proto.take_while(|item| Ok(item.is_some()))
@@ -640,7 +640,18 @@ mod test {
 	#[test]
 	fn it_should_fetch() {
 		let server = TestServer::run();
-		let client = Client::new().unwrap();
+		let client = Client::new(4).unwrap();
+		let future = client.get(&format!("http://{}?123", server.addr()), Default::default());
+		let resp = future.wait().unwrap();
+		assert!(resp.is_success());
+		let body = resp.concat2().wait().unwrap();
+		assert_eq!(&body[..], b"123")
+	}
+
+	#[test]
+	fn it_should_fetch_in_light_mode() {
+		let server = TestServer::run();
+		let client = Client::new(1).unwrap();
 		let future = client.get(&format!("http://{}?123", server.addr()), Default::default());
 		let resp = future.wait().unwrap();
 		assert!(resp.is_success());
@@ -651,7 +662,7 @@ mod test {
 	#[test]
 	fn it_should_timeout() {
 		let server = TestServer::run();
-		let client = Client::new().unwrap();
+		let client = Client::new(4).unwrap();
 		let abort = Abort::default().with_max_duration(Duration::from_secs(1));
 		match client.get(&format!("http://{}/delay?3", server.addr()), abort).wait() {
 			Err(Error::Timeout) => {}
@@ -662,7 +673,7 @@ mod test {
 	#[test]
 	fn it_should_follow_redirects() {
 		let server = TestServer::run();
-		let client = Client::new().unwrap();
+		let client = Client::new(4).unwrap();
 		let abort = Abort::default();
 		let future = client.get(&format!("http://{}/redirect?http://{}/", server.addr(), server.addr()), abort);
 		assert!(future.wait().unwrap().is_success())
@@ -671,7 +682,7 @@ mod test {
 	#[test]
 	fn it_should_follow_relative_redirects() {
 		let server = TestServer::run();
-		let client = Client::new().unwrap();
+		let client = Client::new(4).unwrap();
 		let abort = Abort::default().with_max_redirects(4);
 		let future = client.get(&format!("http://{}/redirect?/", server.addr()), abort);
 		assert!(future.wait().unwrap().is_success())
@@ -680,7 +691,7 @@ mod test {
 	#[test]
 	fn it_should_not_follow_too_many_redirects() {
 		let server = TestServer::run();
-		let client = Client::new().unwrap();
+		let client = Client::new(4).unwrap();
 		let abort = Abort::default().with_max_redirects(3);
 		match client.get(&format!("http://{}/loop", server.addr()), abort).wait() {
 			Err(Error::TooManyRedirects) => {}
@@ -691,7 +702,7 @@ mod test {
 	#[test]
 	fn it_should_read_data() {
 		let server = TestServer::run();
-		let client = Client::new().unwrap();
+		let client = Client::new(4).unwrap();
 		let abort = Abort::default();
 		let future = client.get(&format!("http://{}?abcdefghijklmnopqrstuvwxyz", server.addr()), abort);
 		let resp = future.wait().unwrap();
@@ -702,7 +713,7 @@ mod test {
 	#[test]
 	fn it_should_not_read_too_much_data() {
 		let server = TestServer::run();
-		let client = Client::new().unwrap();
+		let client = Client::new(4).unwrap();
 		let abort = Abort::default().with_max_size(3);
 		let resp = client.get(&format!("http://{}/?1234", server.addr()), abort).wait().unwrap();
 		assert!(resp.is_success());
@@ -715,7 +726,7 @@ mod test {
 	#[test]
 	fn it_should_not_read_too_much_data_sync() {
 		let server = TestServer::run();
-		let client = Client::new().unwrap();
+		let client = Client::new(4).unwrap();
 		let abort = Abort::default().with_max_size(3);
 		let resp = client.get(&format!("http://{}/?1234", server.addr()), abort).wait().unwrap();
 		assert!(resp.is_success());