feat(client): change GaiResolver to use a global blocking threadpool

BREAKING CHANGE: Calls to `GaiResolver::new` and `HttpConnector::new` no
  longer should pass an integer argument for the number of threads.

Author: seanmonstar

Cargo.toml

@@ -38,7 +38,7 @@ pin-utils = "=0.1.0-alpha.4"
 time = "0.1"
 tokio = { version = "=0.2.0-alpha.4", optional = true, default-features = false, features = ["rt-full"] }
 tower-service = "=0.3.0-alpha.1"
-tokio-executor = "=0.2.0-alpha.4"
+tokio-executor = { version = "=0.2.0-alpha.4", features = ["blocking"] }
 tokio-io = "=0.2.0-alpha.4"
 tokio-sync = "=0.2.0-alpha.4"
 tokio-net = { version = "=0.2.0-alpha.4", optional = true, features = ["tcp"] }

benches/end_to_end.rs

@@ -179,7 +179,7 @@ impl Opts {
 
         let addr = spawn_server(&mut rt, &self);
 
-        let connector = HttpConnector::new(1);
+        let connector = HttpConnector::new();
         let client = hyper::Client::builder()
             .http2_only(self.http2)
             .http2_initial_stream_window_size(self.http2_stream_window)

src/client/connect/dns.rs

@@ -15,7 +15,6 @@ use std::net::{
 };
 use std::str::FromStr;
 
-use futures_util::{FutureExt, StreamExt};
 use tokio_sync::{mpsc, oneshot};
 
 use crate::common::{Future, Never, Pin, Poll, Unpin, task};
@@ -39,10 +38,7 @@ pub struct Name {
 /// A resolver using blocking `getaddrinfo` calls in a threadpool.
 #[derive(Clone)]
 pub struct GaiResolver {
-    tx: tokio_executor::threadpool::Sender,
-    /// A handle to keep the threadpool alive until all `GaiResolver` clones
-    /// have been dropped.
-    _threadpool_keep_alive: ThreadPoolKeepAlive,
+    _priv: (),
 }
 
 #[derive(Clone)]
@@ -55,8 +51,7 @@ pub struct GaiAddrs {
 
 /// A future to resole a name returned by `GaiResolver`.
 pub struct GaiFuture {
-    rx: oneshot::Receiver<Result<IpAddrs, io::Error>>,
-    _threadpool_keep_alive: ThreadPoolKeepAlive,
+    inner: tokio_executor::blocking::Blocking<Result<IpAddrs, io::Error>>,
 }
 
 impl Name {
@@ -108,40 +103,9 @@ impl Error for InvalidNameError {}
 
 impl GaiResolver {
     /// Construct a new `GaiResolver`.
-    ///
-    /// Takes number of DNS worker threads.
-    pub fn new(threads: usize) -> Self {
-        let pool = tokio_executor::threadpool::Builder::new()
-            .name_prefix("hyper-dns-gai-resolver")
-            // not for CPU tasks, so only spawn workers
-            // in blocking mode
-            .pool_size(1)
-            .max_blocking(threads)
-            .build();
-
-        let tx = pool.sender().clone();
-
-        // The pool will start to shutdown once `pool` is dropped,
-        // so to keep it alive, we spawn a future onto the pool itself
-        // that will only resolve once all `GaiResolver` requests
-        // are finished.
-        let (shutdown_tx, shutdown_rx) = mpsc::channel(1);
-
-        let on_shutdown = shutdown_rx
-            .into_future()
-            .map(move |(next, _rx)| {
-                match next {
-                    Some(never) => match never {},
-                    None => (),
-                }
-
-                drop(pool)
-            });
-        tx.spawn(on_shutdown).expect("can spawn on self");
-
+    pub fn new() -> Self {
         GaiResolver {
-            tx,
-            _threadpool_keep_alive: ThreadPoolKeepAlive(shutdown_tx),
+            _priv: (),
         }
     }
 }
@@ -151,14 +115,14 @@ impl Resolve for GaiResolver {
     type Future = GaiFuture;
 
     fn resolve(&self, name: Name) -> Self::Future {
-        let (tx, rx) = oneshot::channel();
-        self.tx.spawn(GaiBlocking {
-            host: name.host,
-            tx: Some(tx),
-        }).expect("spawn GaiBlocking");
+        let blocking = tokio_executor::blocking::run(move || {
+            debug!("resolving host={:?}", name.host);
+            (&*name.host, 0).to_socket_addrs()
+                .map(|i| IpAddrs { iter: i })
+        });
+
         GaiFuture {
-            rx,
-            _threadpool_keep_alive: self._threadpool_keep_alive.clone(),
+            inner: blocking,
         }
     }
 }
@@ -173,10 +137,9 @@ impl Future for GaiFuture {
     type Output = Result<GaiAddrs, io::Error>;
 
     fn poll(mut self: Pin<&mut Self>, cx: &mut task::Context<'_>) -> Poll<Self::Output> {
-        Pin::new(&mut self.rx).poll(cx).map(|res| match res {
-            Ok(Ok(addrs)) => Ok(GaiAddrs { inner: addrs }),
-            Ok(Err(err)) => Err(err),
-            Err(_canceled) => unreachable!("GaiResolver threadpool shutdown"),
+        Pin::new(&mut self.inner).poll(cx).map(|res| match res {
+            Ok(addrs) => Ok(GaiAddrs { inner: addrs }),
+            Err(err) => Err(err),
         })
     }
 }

src/client/connect/http.rs

@@ -77,9 +77,8 @@ impl HttpConnector {
     /// Construct a new HttpConnector.
     ///
     /// Takes number of DNS worker threads.
-    #[inline]
-    pub fn new(threads: usize) -> HttpConnector {
-        HttpConnector::new_with_resolver(GaiResolver::new(threads))
+    pub fn new() -> HttpConnector {
+        HttpConnector::new_with_resolver(GaiResolver::new())
     }
 }
 

src/client/mod.rs

@@ -1023,7 +1023,7 @@ impl Builder {
         B: Payload + Send,
         B::Data: Send,
     {
-        let mut connector = HttpConnector::new(4);
+        let mut connector = HttpConnector::new();
         if self.pool_config.enabled {
             connector.set_keepalive(self.pool_config.keep_alive_timeout);
         }

tests/client.rs

@@ -213,7 +213,7 @@ macro_rules! test {
         let addr = server.local_addr().expect("local_addr");
         let rt = $runtime;
 
-        let connector = ::hyper::client::HttpConnector::new(1);
+        let connector = ::hyper::client::HttpConnector::new();
         let client = Client::builder()
             .set_host($set_host)
             .http1_title_case_headers($title_case_headers)
@@ -781,7 +781,7 @@ mod dispatch_impl {
         let mut rt = Runtime::new().unwrap();
         let (closes_tx, closes) = mpsc::channel(10);
         let client = Client::builder()
-            .build(DebugConnector::with_http_and_closes(HttpConnector::new(1), closes_tx));
+            .build(DebugConnector::with_http_and_closes(HttpConnector::new(), closes_tx));
 
         let (tx1, rx1) = oneshot::channel();
 
@@ -837,7 +837,7 @@ mod dispatch_impl {
 
         let res = {
             let client = Client::builder()
-                .build(DebugConnector::with_http_and_closes(HttpConnector::new(1), closes_tx));
+                .build(DebugConnector::with_http_and_closes(HttpConnector::new(), closes_tx));
 
             let req = Request::builder()
                 .uri(&*format!("http://{}/a", addr))
@@ -889,7 +889,7 @@ mod dispatch_impl {
         });
 
         let client = Client::builder()
-            .build(DebugConnector::with_http_and_closes(HttpConnector::new(1), closes_tx));
+            .build(DebugConnector::with_http_and_closes(HttpConnector::new(), closes_tx));
 
         let req = Request::builder()
             .uri(&*format!("http://{}/a", addr))
@@ -948,7 +948,7 @@ mod dispatch_impl {
 
         let res = {
             let client = Client::builder()
-                .build(DebugConnector::with_http_and_closes(HttpConnector::new(1), closes_tx));
+                .build(DebugConnector::with_http_and_closes(HttpConnector::new(), closes_tx));
 
             let req = Request::builder()
                 .uri(&*format!("http://{}/a", addr))
@@ -996,7 +996,7 @@ mod dispatch_impl {
 
         let res = {
             let client = Client::builder()
-                .build(DebugConnector::with_http_and_closes(HttpConnector::new(1), closes_tx));
+                .build(DebugConnector::with_http_and_closes(HttpConnector::new(), closes_tx));
 
             let req = Request::builder()
                 .uri(&*format!("http://{}/a", addr))
@@ -1046,7 +1046,7 @@ mod dispatch_impl {
 
         let client = Client::builder()
             .keep_alive(false)
-            .build(DebugConnector::with_http_and_closes(HttpConnector::new(1), closes_tx));
+            .build(DebugConnector::with_http_and_closes(HttpConnector::new(), closes_tx));
 
         let req = Request::builder()
             .uri(&*format!("http://{}/a", addr))
@@ -1090,7 +1090,7 @@ mod dispatch_impl {
         });
 
         let client = Client::builder()
-            .build(DebugConnector::with_http_and_closes(HttpConnector::new(1), closes_tx));
+            .build(DebugConnector::with_http_and_closes(HttpConnector::new(), closes_tx));
 
         let req = Request::builder()
             .uri(&*format!("http://{}/a", addr))
@@ -1527,7 +1527,7 @@ mod dispatch_impl {
 
     impl DebugConnector {
         fn new() -> DebugConnector {
-            let http = HttpConnector::new(1);
+            let http = HttpConnector::new();
             let (tx, _) = mpsc::channel(10);
             DebugConnector::with_http_and_closes(http, tx)
         }

tests/support/mod.rs

@@ -313,7 +313,7 @@ pub fn __run_test(cfg: __TestConfig) {
         Version::HTTP_11
     };
 
-    let connector = HttpConnector::new(1);
+    let connector = HttpConnector::new();
     let client = Client::builder()
         .keep_alive_timeout(Duration::from_secs(10))
         .http2_only(cfg.client_version == 2)