feat(http1): Add http1_writev(bool) to client and server Builders

Restore a way to force queue writing strategy.

Closes #2676

src/client/client.rs

@@ -1022,6 +1022,23 @@ impl Builder {
         self
     }
 
+    /// Set whether HTTP/1 connections should try to use vectored writes,
+    /// or always flatten into a single buffer.
+    ///
+    /// Note that setting this to false may mean more copies of body data,
+    /// but may also improve performance when an IO transport doesn't
+    /// support vectored writes well, such as most TLS implementations.
+    ///
+    /// Setting this to true will force hyper to use queued strategy
+    /// which may eliminate unnecessary cloning on some TLS backends
+    ///
+    /// Default is `auto`. In this mode hyper will try to guess which
+    /// mode to use
+    pub fn http1_writev(&mut self, enabled: bool) -> &mut Builder {
+        self.conn_builder.http1_writev(enabled);
+        self
+    }
+
     /// Set whether HTTP/1 connections will write header names as title case at
     /// the socket level.
     ///

src/client/conn.rs

@@ -153,6 +153,7 @@ pub struct Builder {
     pub(super) exec: Exec,
     h09_responses: bool,
     h1_parser_config: ParserConfig,
+    h1_writev: Option<bool>,
     h1_title_case_headers: bool,
     h1_preserve_header_case: bool,
     h1_read_buf_exact_size: Option<usize>,
@@ -535,6 +536,7 @@ impl Builder {
         Builder {
             exec: Exec::Default,
             h09_responses: false,
+            h1_writev: None,
             h1_read_buf_exact_size: None,
             h1_parser_config: Default::default(),
             h1_title_case_headers: false,
@@ -596,6 +598,23 @@ impl Builder {
         self
     }
 
+    /// Set whether HTTP/1 connections should try to use vectored writes,
+    /// or always flatten into a single buffer.
+    ///
+    /// Note that setting this to false may mean more copies of body data,
+    /// but may also improve performance when an IO transport doesn't
+    /// support vectored writes well, such as most TLS implementations.
+    ///
+    /// Setting this to true will force hyper to use queued strategy
+    /// which may eliminate unnecessary cloning on some TLS backends
+    ///
+    /// Default is `auto`. In this mode hyper will try to guess which
+    /// mode to use
+    pub fn http1_writev(&mut self, enabled: bool) -> &mut Builder {
+        self.h1_writev = Some(enabled);
+        self
+    }
+
     /// Set whether HTTP/1 connections will write header names as title case at
     /// the socket level.
     ///
@@ -837,6 +856,13 @@ impl Builder {
                 Proto::Http1 => {
                     let mut conn = proto::Conn::new(io);
                     conn.set_h1_parser_config(opts.h1_parser_config);
+                    if let Some(writev) = opts.h1_writev {
+                        if writev {
+                            conn.set_write_strategy_queue();
+                        } else {
+                            conn.set_write_strategy_flatten();
+                        }
+                    }
                     if opts.h1_title_case_headers {
                         conn.set_title_case_headers();
                     }

src/proto/h1/conn.rs

@@ -71,7 +71,6 @@ where
         self.io.set_flush_pipeline(enabled);
     }
 
-    #[cfg(test)]
     pub(crate) fn set_write_strategy_queue(&mut self) {
         self.io.set_write_strategy_queue();
     }
@@ -85,6 +84,10 @@ where
         self.io.set_read_buf_exact_size(sz);
     }
 
+    pub(crate) fn set_write_strategy_flatten(&mut self) {
+        self.io.set_write_strategy_flatten();
+    }
+
     #[cfg(feature = "client")]
     pub(crate) fn set_h1_parser_config(&mut self, parser_config: ParserConfig) {
         self.state.h1_parser_config = parser_config;

src/proto/h1/io.rs

@@ -97,16 +97,17 @@ where
         self.read_buf_strategy = ReadStrategy::Exact(sz);
     }
 
-    #[cfg(feature = "server")]
+    pub(crate) fn set_write_strategy_flatten(&mut self) {
-    fn set_write_strategy_flatten(&mut self) {
         // this should always be called only at construction time,
         // so this assert is here to catch myself
         debug_assert!(self.write_buf.queue.bufs_cnt() == 0);
         self.write_buf.set_strategy(WriteStrategy::Flatten);
     }
 
-    #[cfg(test)]
     pub(crate) fn set_write_strategy_queue(&mut self) {
+        // this should always be called only at construction time,
+        // so this assert is here to catch myself
+        debug_assert!(self.write_buf.queue.bufs_cnt() == 0);
         self.write_buf.set_strategy(WriteStrategy::Queue);
     }
 
@@ -520,7 +521,6 @@ impl<B> WriteBuf<B>
 where
     B: Buf,
 {
-    #[cfg(feature = "server")]
     fn set_strategy(&mut self, strategy: WriteStrategy) {
         self.strategy = strategy;
     }

src/server/conn.rs

@@ -103,6 +103,7 @@ pub struct Http<E = Exec> {
     h1_keep_alive: bool,
     h1_title_case_headers: bool,
     h1_preserve_header_case: bool,
+    h1_writev: Option<bool>,
     #[cfg(feature = "http2")]
     h2_builder: proto::h2::server::Config,
     mode: ConnectionMode,
@@ -284,6 +285,7 @@ impl Http {
             h1_keep_alive: true,
             h1_title_case_headers: false,
             h1_preserve_header_case: false,
+            h1_writev: None,
             #[cfg(feature = "http2")]
             h2_builder: Default::default(),
             mode: ConnectionMode::default(),
@@ -363,6 +365,26 @@ impl<E> Http<E> {
         self
     }
 
+    /// Set whether HTTP/1 connections should try to use vectored writes,
+    /// or always flatten into a single buffer.
+    ///
+    /// Note that setting this to false may mean more copies of body data,
+    /// but may also improve performance when an IO transport doesn't
+    /// support vectored writes well, such as most TLS implementations.
+    ///
+    /// Setting this to true will force hyper to use queued strategy
+    /// which may eliminate unnecessary cloning on some TLS backends
+    ///
+    /// Default is `auto`. In this mode hyper will try to guess which
+    /// mode to use
+    #[inline]
+    #[cfg(feature = "http1")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "http1")))]
+    pub fn http1_writev(&mut self, val: bool) -> &mut Self {
+        self.h1_writev = Some(val);
+        self
+    }
+
     /// Sets whether HTTP2 is required.
     ///
     /// Default is false
@@ -538,6 +560,7 @@ impl<E> Http<E> {
             h1_keep_alive: self.h1_keep_alive,
             h1_title_case_headers: self.h1_title_case_headers,
             h1_preserve_header_case: self.h1_preserve_header_case,
+            h1_writev: self.h1_writev,
             #[cfg(feature = "http2")]
             h2_builder: self.h2_builder,
             mode: self.mode,
@@ -599,6 +622,13 @@ impl<E> Http<E> {
                 if self.h1_preserve_header_case {
                     conn.set_preserve_header_case();
                 }
+                if let Some(writev) = self.h1_writev {
+                    if writev {
+                        conn.set_write_strategy_queue();
+                    } else {
+                        conn.set_write_strategy_flatten();
+                    }
+                }
                 conn.set_flush_pipeline(self.pipeline_flush);
                 if let Some(max) = self.max_buf_size {
                     conn.set_max_buf_size(max);

src/server/server.rs

@@ -258,6 +258,24 @@ impl<I, E> Builder<I, E> {
         self
     }
 
+    /// Set whether HTTP/1 connections should try to use vectored writes,
+    /// or always flatten into a single buffer.
+    ///
+    /// Note that setting this to false may mean more copies of body data,
+    /// but may also improve performance when an IO transport doesn't
+    /// support vectored writes well, such as most TLS implementations.
+    ///
+    /// Setting this to true will force hyper to use queued strategy
+    /// which may eliminate unnecessary cloning on some TLS backends
+    ///
+    /// Default is `auto`. In this mode hyper will try to guess which
+    /// mode to use
+    #[cfg(feature = "http1")]
+    pub fn http1_writev(mut self, enabled: bool) -> Self {
+        self.protocol.http1_writev(enabled);
+        self
+    }
+
     /// Set whether HTTP/1 connections will write header names as title case at
     /// the socket level.
     ///