feat(server): add http1_half_close(bool) option

This option determines whether a read EOF should close the connection
automatically. The behavior was to always allow read EOF while waiting
to respond, so this option has a default of `true`.

Setting this option to `false` will allow Service futures to be canceled
as soon as disconnect is noticed.

Closes #1716

src/server/conn.rs

@@ -45,6 +45,7 @@ pub(super) use self::upgrades::UpgradeableConnection;
 #[derive(Clone, Debug)]
 pub struct Http<E = Exec> {
     exec: E,
+    h1_half_close: bool,
     h1_writev: bool,
     mode: ConnectionMode,
     keep_alive: bool,
@@ -163,6 +164,7 @@ impl Http {
     pub fn new() -> Http {
         Http {
             exec: Exec::Default,
+            h1_half_close: true,
             h1_writev: true,
             mode: ConnectionMode::Fallback,
             keep_alive: true,
@@ -195,6 +197,20 @@ impl<E> Http<E> {
         self
     }
 
+    /// Set whether HTTP/1 connections should support half-closures.
+    ///
+    /// Clients can chose to shutdown their write-side while waiting
+    /// for the server to respond. Setting this to `false` will
+    /// automatically close any connection immediately if `read`
+    /// detects an EOF.
+    ///
+    /// Default is `true`.
+    #[inline]
+    pub fn http1_half_close(&mut self, val: bool) -> &mut Self {
+        self.h1_half_close = val;
+        self
+    }
+
     /// Set whether HTTP/1 connections should try to use vectored writes,
     /// or always flatten into a single buffer.
     ///
@@ -261,6 +277,7 @@ impl<E> Http<E> {
     pub fn with_executor<E2>(self, exec: E2) -> Http<E2> {
         Http {
             exec,
+            h1_half_close: self.h1_half_close,
             h1_writev: self.h1_writev,
             mode: self.mode,
             keep_alive: self.keep_alive,
@@ -319,6 +336,9 @@ impl<E> Http<E> {
                 if !self.keep_alive {
                     conn.disable_keep_alive();
                 }
+                if !self.h1_half_close {
+                    conn.set_disable_half_close();
+                }
                 if !self.h1_writev {
                     conn.set_write_strategy_flatten();
                 }