feat(client): implement connection pooling for Client

Closes #830
Closes #848

tests/server.rs

@@ -72,7 +72,7 @@ impl Drop for Serve {
 
 struct TestHandler {
     tx: mpsc::Sender<Msg>,
-    rx: mpsc::Receiver<Reply>,
+    reply: Vec<Reply>,
     peeked: Option<Vec<u8>>,
     timeout: Option<Duration>,
 }
@@ -123,28 +123,26 @@ impl Handler<HttpStream> for TestHandler {
     }
 
     fn on_response(&mut self, res: &mut Response) -> Next {
-        loop {
-            match self.rx.try_recv() {
-                Ok(Reply::Status(s)) => {
+        for reply in self.reply.drain(..) {
+            match reply {
+                Reply::Status(s) => {
                     res.set_status(s);
                 },
-                Ok(Reply::Headers(headers)) => {
+                Reply::Headers(headers) => {
                     use std::iter::Extend;
                     res.headers_mut().extend(headers.iter());
                 },
-                Ok(Reply::Body(body)) => {
+                Reply::Body(body) => {
                     self.peeked = Some(body);
                 },
-                Err(..) => {
-                    return if self.peeked.is_some() {
-                        self.next(Next::write())
-                    } else {
-                        self.next(Next::end())
-                    };
-                },
             }
         }
 
+        if self.peeked.is_some() {
+            self.next(Next::write())
+        } else {
+            self.next(Next::end())
+        }
     }
 
     fn on_response_writable(&mut self, encoder: &mut Encoder<HttpStream>) -> Next {
@@ -167,13 +165,18 @@ fn serve_with_timeout(dur: Option<Duration>) -> Serve {
 
     let (msg_tx, msg_rx) = mpsc::channel();
     let (reply_tx, reply_rx) = mpsc::channel();
-    let mut reply_rx = Some(reply_rx);
     let (listening, server) = Server::http(&"127.0.0.1:0".parse().unwrap()).unwrap()
-        .handle(move |_| TestHandler {
-            tx: msg_tx.clone(),
-            timeout: dur,
-            rx: reply_rx.take().unwrap(),
-            peeked: None,
+        .handle(move |_| {
+            let mut replies = Vec::new();
+            while let Ok(reply) = reply_rx.try_recv() {
+                replies.push(reply);
+            }
+            TestHandler {
+                tx: msg_tx.clone(),
+                timeout: dur,
+                reply: replies,
+                peeked: None,
+            }
         }).unwrap();
 
 
@@ -377,3 +380,62 @@ fn server_empty_response_chunked_without_calling_write() {
     assert_eq!(lines.next(), Some(""));
     assert_eq!(lines.next(), None);
 }
+
+#[test]
+fn server_keep_alive() {
+    extern crate env_logger;
+    env_logger::init().unwrap();
+
+    let foo_bar = b"foo bar baz";
+    let server = serve();
+    server.reply()
+        .status(hyper::Ok)
+        .header(hyper::header::ContentLength(foo_bar.len() as u64))
+        .body(foo_bar);
+    let mut req = TcpStream::connect(server.addr()).unwrap();
+    req.set_read_timeout(Some(Duration::from_secs(5))).unwrap();
+    req.set_write_timeout(Some(Duration::from_secs(5))).unwrap();
+    req.write_all(b"\
+        GET / HTTP/1.1\r\n\
+        Host: example.domain\r\n\
+        Connection: keep-alive\r\n\
+        \r\n\
+    ").expect("writing 1");
+
+    let mut buf = [0; 1024 * 8];
+    loop {
+        let n = req.read(&mut buf[..]).expect("reading 1");
+        if n < buf.len() {
+            if &buf[n - foo_bar.len()..n] == foo_bar {
+                break;
+            } else {
+                println!("{:?}", ::std::str::from_utf8(&buf[..n]));
+            }
+        }
+    }
+
+    // try again!
+
+    let quux = b"zar quux";
+    server.reply()
+        .status(hyper::Ok)
+        .header(hyper::header::ContentLength(quux.len() as u64))
+        .body(quux);
+    req.write_all(b"\
+        GET /quux HTTP/1.1\r\n\
+        Host: example.domain\r\n\
+        Connection: close\r\n\
+        \r\n\
+    ").expect("writing 2");
+
+    let mut buf = [0; 1024 * 8];
+    loop {
+        let n = req.read(&mut buf[..]).expect("reading 2");
+        assert!(n > 0, "n = {}", n);
+        if n < buf.len() {
+            if &buf[n - quux.len()..n] == quux {
+                break;
+            }
+        }
+    }
+}