From 29a48490240534ae985adea9fed4007ed4570414 Mon Sep 17 00:00:00 2001
From: Vinnie Falco <vinnie.falco@gmail.com>
Date: Mon, 7 Mar 2016 16:29:45 -0500
Subject: [PATCH] Improve socket writes in BaseHTTPPeer

---
 src/ripple/server/impl/BaseHTTPPeer.h | 104 ++++++++++++--------------
 1 file changed, 49 insertions(+), 55 deletions(-)

diff --git a/src/ripple/server/impl/BaseHTTPPeer.h b/src/ripple/server/impl/BaseHTTPPeer.h
index 490a4ab582..5183d4a312 100644
--- a/src/ripple/server/impl/BaseHTTPPeer.h
+++ b/src/ripple/server/impl/BaseHTTPPeer.h
@@ -38,10 +38,10 @@
 #include <cassert>
 #include <chrono>
 #include <functional>
-#include <list>
 #include <memory>
 #include <mutex>
 #include <type_traits>
+#include <vector>
 
 namespace ripple {
 
@@ -97,7 +97,8 @@ protected:
     boost::asio::streambuf read_buf_;
     beast::http::message message_;
     beast::http::body body_;
-    std::list <buffer> write_queue_;
+    std::vector<buffer> wq_;
+    std::vector<buffer> wq2_;
     std::mutex mutex_;
     bool graceful_ = false;
     bool complete_ = false;
@@ -150,7 +151,8 @@ protected:
     do_read (yield_context yield);
 
     void
-    do_write (yield_context yield);
+    on_write(error_code const& ec,
+        std::size_t bytes_transferred);
 
     void
     do_writer (std::shared_ptr <Writer> const& writer,
@@ -379,54 +381,41 @@ BaseHTTPPeer<Impl>::do_read (yield_context yield)
 
 // Send everything in the write queue.
 // The write queue must not be empty upon entry.
-template <class Impl>
+template<class Impl>
 void
-BaseHTTPPeer<Impl>::do_write (yield_context yield)
+BaseHTTPPeer<Impl>::on_write(error_code const& ec,
+    std::size_t bytes_transferred)
 {
-    error_code ec;
-    std::size_t bytes = 0;
-    for(;;)
+    cancel_timer();
+    if(ec)
+        return fail(ec, "write");
+    bytes_out_ += bytes_transferred;
     {
-        bytes_out_ += bytes;
-        void const* data;
-        {
-            std::lock_guard <std::mutex> lock (mutex_);
-            assert(! write_queue_.empty());
-            buffer& b1 = write_queue_.front();
-            b1.used += bytes;
-            if (b1.used >= b1.bytes)
-            {
-                write_queue_.pop_front();
-                if (write_queue_.empty())
-                    break;
-                buffer& b2 = write_queue_.front();
-                data = b2.data.get();
-                bytes = b2.bytes;
-            }
-            else
-            {
-                data = b1.data.get() + b1.used;
-                bytes = b1.bytes - b1.used;
-            }
-        }
-
-        start_timer();
-        bytes = boost::asio::async_write (impl().stream_,
-            boost::asio::buffer (data, bytes),
-                boost::asio::transfer_at_least(1), yield[ec]);
-        cancel_timer();
-        if (ec)
-            return fail (ec, "write");
+        std::lock_guard<std::mutex> lock(mutex_);
+        wq2_.clear();
+        wq2_.reserve(wq_.size());
+        std::swap(wq2_, wq_);
+    }
+    if(! wq2_.empty())
+    {
+        std::vector<boost::asio::const_buffer> v;
+        v.reserve(wq2_.size());
+        for(auto const& b : wq2_)
+            v.emplace_back(b.data.get(), b.bytes);
+        start_timer();
+        using namespace beast::asio;
+        return boost::asio::async_write(impl().stream_, v,
+            strand_.wrap(std::bind(&BaseHTTPPeer::on_write,
+                impl().shared_from_this(), placeholders::error,
+                    placeholders::bytes_transferred)));
     }
-
     if (! complete_)
         return;
-
     if (graceful_)
         return do_close();
-
-    boost::asio::spawn (strand_, std::bind (&BaseHTTPPeer<Impl>::do_read,
-        impl().shared_from_this(), std::placeholders::_1));
+    boost::asio::spawn(strand_,
+        std::bind (&BaseHTTPPeer<Impl>::do_read,
+            impl().shared_from_this(), std::placeholders::_1));
 }
 
 template <class Impl>
@@ -473,21 +462,26 @@ BaseHTTPPeer<Impl>::do_writer (std::shared_ptr <Writer> const& writer,
 // Send a copy of the data.
 template <class Impl>
 void
-BaseHTTPPeer<Impl>::write (void const* buffer, std::size_t bytes)
+BaseHTTPPeer<Impl>::write(
+    void const* buffer, std::size_t bytes)
 {
     if (bytes == 0)
         return;
-
-    bool empty;
+    if([&]
+        {
+            std::lock_guard<std::mutex> lock(mutex_);
+            wq_.emplace_back(buffer, bytes);
+            return wq_.size() == 1 && wq2_.size() == 0;
+        }())
     {
-        std::lock_guard <std::mutex> lock (mutex_);
-        empty = write_queue_.empty();
-        write_queue_.emplace_back (buffer, bytes);
+        if (strand_.running_in_this_thread())
+            return strand_.post(std::bind(
+                &BaseHTTPPeer::on_write,
+                    impl().shared_from_this(),
+                        error_code{}, 0));
+        else
+            return on_write(error_code{}, 0);
     }
-
-    if (empty)
-        boost::asio::spawn (strand_, std::bind (&BaseHTTPPeer<Impl>::do_write,
-            impl().shared_from_this(), std::placeholders::_1));
 }
 
 template <class Impl>
@@ -524,7 +518,7 @@ BaseHTTPPeer<Impl>::complete()
 
     {
         std::lock_guard<std::mutex> lock(mutex_);
-        if (! write_queue_.empty())
+        if (! wq_.empty() && ! wq2_.empty())
             return;
     }
 
@@ -550,7 +544,7 @@ BaseHTTPPeer<Impl>::close (bool graceful)
         graceful_ = true;
         {
             std::lock_guard<std::mutex> lock(mutex_);
-            if (! write_queue_.empty())
+            if (! wq_.empty() || ! wq2_.empty())
                 return;
         }
         return do_close();