From 686b415fb7808a11a696d72c08124ca90df607ae Mon Sep 17 00:00:00 2001
From: Chunting Gu <sprinfall@gmail.com>
Date: Fri, 7 Sep 2018 13:34:33 +0800
Subject: [PATCH] Refine the initialization of server's acceptor.

---
 webcc/http_server.cc | 76 ++++++++++++++++++++++++++++++--------------
 webcc/http_server.h  | 14 ++++----
 2 files changed, 61 insertions(+), 29 deletions(-)

diff --git a/webcc/http_server.cc b/webcc/http_server.cc
index 78a8da1..15032b0 100644
--- a/webcc/http_server.cc
+++ b/webcc/http_server.cc
@@ -13,31 +13,52 @@ using tcp = boost::asio::ip::tcp;
 namespace webcc {
 
 HttpServer::HttpServer(std::uint16_t port, std::size_t workers)
-    : signals_(io_context_) , workers_(workers) {
-  // Register to handle the signals that indicate when the server should exit.
-  // It is safe to register for the same signal multiple times in a program,
-  // provided all registration for the specified signal is made through asio.
-  signals_.add(SIGINT);  // Ctrl+C
-  signals_.add(SIGTERM);
-#if defined(SIGQUIT)
-  signals_.add(SIGQUIT);
-#endif
-
-  // NOTE:
-  // "reuse_addr=true" means option SO_REUSEADDR will be set.
-  // For more details about SO_REUSEADDR, see:
-  // https://msdn.microsoft.com/en-us/library/windows/desktop/ms740621(v=vs.85).aspx
-  // https://stackoverflow.com/a/3233022
-  // http://www.andy-pearce.com/blog/posts/2013/Feb/so_reuseaddr-on-windows/
-  // When |reuse_addr| is true, multiple servers can listen on the same port.
-  acceptor_.reset(new tcp::acceptor(io_context_,
-                                    tcp::endpoint(tcp::v4(), port),
-                                    true));  // reuse_addr
+    : acceptor_(io_context_), signals_(io_context_), workers_(workers) {
+  RegisterSignals();
+
+  boost::system::error_code ec;
+  tcp::endpoint endpoint(tcp::v4(), port);
+
+  // Open the acceptor.
+  acceptor_.open(endpoint.protocol(), ec);
+  if (ec) {
+    LOG_ERRO("Acceptor open error: %s", ec.message().c_str());
+    return;
+  }
+
+  // Set option SO_REUSEADDR on.
+  // When SO_REUSEADDR is set, multiple servers can listen on the same port.
+  // This is necessary for restarting the server on the same port.
+  // More details:
+  // - https://stackoverflow.com/a/3233022
+  // - http://www.andy-pearce.com/blog/posts/2013/Feb/so_reuseaddr-on-windows/
+  acceptor_.set_option(tcp::acceptor::reuse_address(true));
+
+  // Bind to the server address.
+  acceptor_.bind(endpoint, ec);
+  if (ec) {
+    LOG_ERRO("Acceptor bind error: %s", ec.message().c_str());
+    return;
+  }
+
+  // Start listening for connections.
+  // After listen, the client is able to connect to the server even the server
+  // has not started to accept the connection yet.
+  acceptor_.listen(boost::asio::socket_base::max_listen_connections, ec);
+  if (ec) {
+    LOG_ERRO("Acceptor listen error: %s", ec.message().c_str());
+    return;
+  }
 }
 
 void HttpServer::Run() {
   assert(GetRequestHandler() != nullptr);
 
+  if (!acceptor_.is_open()) {
+    LOG_ERRO("Server is NOT going to run.");
+    return;
+  }
+
   LOG_INFO("Server is going to run...");
 
   AsyncAwaitStop();
@@ -54,12 +75,21 @@ void HttpServer::Run() {
   io_context_.run();
 }
 
+void HttpServer::RegisterSignals() {
+  signals_.add(SIGINT);  // Ctrl+C
+  signals_.add(SIGTERM);
+
+#if defined(SIGQUIT)
+  signals_.add(SIGQUIT);
+#endif
+}
+
 void HttpServer::AsyncAccept() {
-  acceptor_->async_accept(
+  acceptor_.async_accept(
       [this](boost::system::error_code ec, tcp::socket socket) {
         // Check whether the server was stopped by a signal before this
         // completion handler had a chance to run.
-        if (!acceptor_->is_open()) {
+        if (!acceptor_.is_open()) {
           return;
         }
 
@@ -83,7 +113,7 @@ void HttpServer::AsyncAwaitStop() {
         // operations. Once all operations have finished the io_context::run()
         // call will exit.
         LOG_INFO("On signal %d, stopping the server...", signo);
-        acceptor_->close();
+        acceptor_.close();
         GetRequestHandler()->Stop();
       });
 }
diff --git a/webcc/http_server.h b/webcc/http_server.h
index 2997376..977c035 100644
--- a/webcc/http_server.h
+++ b/webcc/http_server.h
@@ -6,7 +6,6 @@
 #include "boost/asio/io_context.hpp"
 #include "boost/asio/ip/tcp.hpp"
 #include "boost/asio/signal_set.hpp"
-#include "boost/scoped_ptr.hpp"
 
 #include "webcc/globals.h"
 #include "webcc/http_connection.h"
@@ -29,6 +28,9 @@ class HttpServer {
   void Run();
 
  private:
+  // Register to handle the signals that indicate when the server should exit.
+  void RegisterSignals();
+
   // Initiate an asynchronous accept operation.
   void AsyncAccept();
 
@@ -38,17 +40,17 @@ class HttpServer {
   // Get the handler for incoming requests.
   virtual HttpRequestHandler* GetRequestHandler() = 0;
 
-  // The number of worker threads.
-  std::size_t workers_;
-
   // The io_context used to perform asynchronous operations.
   boost::asio::io_context io_context_;
 
+  // Acceptor used to listen for incoming connections.
+  boost::asio::ip::tcp::acceptor acceptor_;
+
   // The signal_set is used to register for process termination notifications.
   boost::asio::signal_set signals_;
 
-  // Acceptor used to listen for incoming connections.
-  boost::scoped_ptr<boost::asio::ip::tcp::acceptor> acceptor_;
+  // The number of worker threads.
+  std::size_t workers_;
 };
 
 }  // namespace webcc