asio: Add http2::backlog API function

src/asio_http2_impl.cc

@@ -68,9 +68,15 @@ void http2::num_concurrent_tasks(size_t num_concurrent_tasks)
   impl_->num_concurrent_tasks(num_concurrent_tasks);
 }
 
+void http2::backlog(int backlog)
+{
+  impl_->backlog(backlog);
+}
+
 http2_impl::http2_impl()
   : num_threads_(1),
-    num_concurrent_tasks_(1)
+    num_concurrent_tasks_(1),
+    backlog_(-1)
 {}
 
 namespace {
@@ -134,7 +140,7 @@ void http2_impl::listen(const std::string& address, uint16_t port,
   }
 
   server(address, port, num_threads_, num_concurrent_tasks_,
-         std::move(cb), std::move(ssl_ctx)).run();
+         std::move(cb), std::move(ssl_ctx), backlog_).run();
 }
 
 void http2_impl::num_threads(size_t num_threads)
@@ -154,6 +160,11 @@ void http2_impl::num_concurrent_tasks(size_t num_concurrent_tasks)
   num_concurrent_tasks_ = num_concurrent_tasks;
 }
 
+void http2_impl::backlog(int backlog)
+{
+  backlog_ = backlog;
+}
+
 } // namespace server
 
 template<typename T, typename F>

src/asio_http2_impl.h

@@ -45,12 +45,14 @@ public:
   void num_threads(size_t num_threads);
   void tls(std::string private_key_file, std::string certificate_file);
   void num_concurrent_tasks(size_t num_concurrent_tasks);
+  void backlog(int backlog);
 private:
   std::string private_key_file_;
   std::string certificate_file_;
   std::unique_ptr<server> server_;
   std::size_t num_threads_;
   std::size_t num_concurrent_tasks_;
+  int backlog_;
 };
 
 } // namespace server

src/asio_server.cc

@@ -46,7 +46,8 @@ server::server(const std::string& address, uint16_t port,
                std::size_t io_service_pool_size,
                std::size_t thread_pool_size,
                request_cb cb,
-               std::unique_ptr<boost::asio::ssl::context> ssl_ctx)
+               std::unique_ptr<boost::asio::ssl::context> ssl_ctx,
+               int backlog)
   : io_service_pool_(io_service_pool_size, thread_pool_size),
     signals_(io_service_pool_.get_io_service()),
     tick_timer_(io_service_pool_.get_io_service(),
@@ -76,7 +77,11 @@ server::server(const std::string& address, uint16_t port,
   acceptor_.open(endpoint.protocol());
   acceptor_.set_option(boost::asio::ip::tcp::acceptor::reuse_address(true));
   acceptor_.bind(endpoint);
-  acceptor_.listen();
+  if(backlog == -1) {
+    acceptor_.listen();
+  } else {
+    acceptor_.listen(backlog);
+  }
 
   start_accept();
 

src/asio_server.h

@@ -68,7 +68,8 @@ public:
                   std::size_t io_service_pool_size,
                   std::size_t thread_pool_size,
                   request_cb cb,
-                  std::unique_ptr<boost::asio::ssl::context> ssl_ctx);
+                  std::unique_ptr<boost::asio::ssl::context> ssl_ctx,
+                  int backlog = -1);
 
   /// Run the server's io_service loop.
   void run();

src/includes/nghttp2/asio_http2.h

@@ -208,6 +208,10 @@ public:
   // of thread to handle incoming HTTP request.  For this purpose, see
   // num_threads().
   void num_concurrent_tasks(size_t num_concurrent_tasks);
+
+  // Sets the maximum length to which the queue of pending
+  // connections.
+  void backlog(int backlog);
 private:
   std::unique_ptr<http2_impl> impl_;
 };