Add http_listener configuration for the backlog, the maximum length of the queue of pending connections on the port.

Author: garethsb

Release/include/cpprest/http_listener.h

@@ -46,6 +46,7 @@ class http_listener_config
     /// </summary>
     http_listener_config()
         : m_timeout(utility::seconds(120))
+        , m_backlog(0)
     {}
 
     /// <summary>
@@ -54,6 +55,7 @@ class http_listener_config
     /// <param name="other">http_listener_config to copy.</param>
     http_listener_config(const http_listener_config &other)
         : m_timeout(other.m_timeout)
+        , m_backlog(other.m_backlog)
 #if !defined(_WIN32) || defined(CPPREST_FORCE_HTTP_LISTENER_ASIO)
         , m_ssl_context_callback(other.m_ssl_context_callback)
 #endif
@@ -65,6 +67,7 @@ class http_listener_config
     /// <param name="other">http_listener_config to move from.</param>
     http_listener_config(http_listener_config &&other)
         : m_timeout(std::move(other.m_timeout))
+        , m_backlog(std::move(other.m_backlog))
 #if !defined(_WIN32) || defined(CPPREST_FORCE_HTTP_LISTENER_ASIO)
         , m_ssl_context_callback(std::move(other.m_ssl_context_callback))
 #endif
@@ -79,6 +82,7 @@ class http_listener_config
         if(this != &rhs)
         {
             m_timeout = rhs.m_timeout;
+            m_backlog = rhs.m_backlog;
 #if !defined(_WIN32) || defined(CPPREST_FORCE_HTTP_LISTENER_ASIO)
             m_ssl_context_callback = rhs.m_ssl_context_callback;
 #endif
@@ -95,6 +99,7 @@ class http_listener_config
         if(this != &rhs)
         {
             m_timeout = std::move(rhs.m_timeout);
+            m_backlog = std::move(rhs.m_backlog);
 #if !defined(_WIN32) || defined(CPPREST_FORCE_HTTP_LISTENER_ASIO)
             m_ssl_context_callback = std::move(rhs.m_ssl_context_callback);
 #endif
@@ -120,6 +125,26 @@ class http_listener_config
         m_timeout = std::move(timeout);
     }
 
+    /// <summary>
+    /// Get the listen backlog
+    /// </summary>
+    /// <returns>The maximum length of the queue of pending connections, or zero for the implementation default.</returns>
+    /// <remarks>The implementation may not honour this value.</remarks>
+    int backlog() const
+    {
+        return m_backlog;
+    }
+
+    /// <summary>
+    /// Set the listen backlog
+    /// </summary>
+    /// <param name="backlog">The maximum length of the queue of pending connections, or zero for the implementation default.</param>
+    /// <remarks>The implementation may not honour this value.</remarks>
+    void set_backlog(int backlog)
+    {
+        m_backlog = backlog;
+    }
+
 #if !defined(_WIN32) || defined(CPPREST_FORCE_HTTP_LISTENER_ASIO)
     /// <summary>
     /// Get the callback of ssl context
@@ -143,6 +168,7 @@ class http_listener_config
 private:
 
     utility::seconds m_timeout;
+    int m_backlog;
 #if !defined(_WIN32) || defined(CPPREST_FORCE_HTTP_LISTENER_ASIO)
     std::function<void(boost::asio::ssl::context&)> m_ssl_context_callback;
 #endif

Release/src/http/listener/http_server_asio.cpp

@@ -122,6 +122,7 @@ namespace
     class hostport_listener
     {
     private:
+        int m_backlog;
         std::unique_ptr<boost::asio::ip::tcp::acceptor> m_acceptor;
         std::map<std::string, http_listener_impl* > m_listeners;
         pplx::extensibility::reader_writer_lock_t m_listeners_lock;
@@ -140,7 +141,8 @@ namespace
 
     public:
         hostport_listener(http_linux_server* server, const std::string& hostport, bool is_https, const http_listener_config& config)
-            : m_acceptor()
+            : m_backlog(config.backlog())
+            , m_acceptor()
             , m_listeners()
             , m_listeners_lock()
             , m_connections_lock()
@@ -482,8 +484,11 @@ void hostport_listener::start()
 
     tcp::endpoint endpoint = *resolver.resolve(query);
 
-    m_acceptor.reset(new tcp::acceptor(service, endpoint));
-    m_acceptor->set_option(tcp::acceptor::reuse_address(true));
+    m_acceptor.reset(new tcp::acceptor(service));
+    m_acceptor->open(endpoint.protocol());
+    m_acceptor->set_option(socket_base::reuse_address(true));
+    m_acceptor->bind(endpoint);
+    m_acceptor->listen(0 != m_backlog ? m_backlog : socket_base::max_connections);
 
     auto socket = new ip::tcp::socket(service);
     m_acceptor->async_accept(*socket, [this, socket](const boost::system::error_code& ec)