Add the reuse_port option (#634)

config.example.json

@@ -217,7 +217,9 @@
         "client_max_memory_body_size": "64K",
         //client_max_websocket_message_size: Set the maximum size of messages sent by WebSocket client. The default value is "128K".
         //One can set it to "1024", "1k", "10M", "1G", etc. Setting it to "" means no limit.
-        "client_max_websocket_message_size": "128K"
+        "client_max_websocket_message_size": "128K",
+        //reuse_port: Defaults to false, users can run multiple processes listening on the same port at the same time.
+        "reuse_port": false
     },
     //plugins: Define all plugins running in the application
     "plugins": [{

drogon_ctl/templates/config.csp

@@ -217,7 +217,9 @@
         "client_max_memory_body_size": "64K",
         //client_max_websocket_message_size: Set the maximum size of messages sent by WebSocket client. The default value is "128K".
         //One can set it to "1024", "1k", "10M", "1G", etc. Setting it to "" means no limit.
-        "client_max_websocket_message_size": "128K"
+        "client_max_websocket_message_size": "128K",
+        //reuse_port: Defaults to false, users can run multiple processes listening on the same port at the same time.
+        "reuse_port": false
     },
     //plugins: Define all plugins running in the application
     "plugins": [{

examples/simple_example/TimeFilter.cc

@@ -20,7 +20,10 @@ void TimeFilter::doFilter(const HttpRequestPtr &req,
     {
         auto lastDate = req->session()->get<trantor::Date>(VDate);
         LOG_TRACE << "last:" << lastDate.toFormattedString(false);
-        req->session()->insert(VDate, now);
+        req->session()->modify<trantor::Date>(VDate,
+                                              [now](trantor::Date &vdate) {
+                                                  vdate = now;
+                                              });
         LOG_TRACE << "update visitDate";
         if (now > lastDate.after(10))
         {

lib/inc/drogon/HttpAppFramework.h

@@ -1172,6 +1172,21 @@ class HttpAppFramework : public trantor::NonCopyable
      */
     virtual std::vector<trantor::InetAddress> getListeners() const = 0;
 
+    /**
+     * @brief Enable ReusePort mode or not. If the mode is enabled, one can run
+     * multiple processes listening to the same port at the same time. If this
+     * method is not called, the feature is disabled.
+     *
+     * @note
+     * This operation can be performed by an option in the configuration file.
+     */
+    virtual void enableReusePort(bool enable = true) = 0;
+
+    /**
+     * @brief Return if the ReusePort mode is enabled.
+     */
+    virtual bool reusePort() const = 0;
+
   private:
     virtual void registerHttpController(
         const std::string &pathPattern,

lib/inc/drogon/Session.h

@@ -1,7 +1,7 @@
 /**
  *
  *  @file Session.h
- *  An Tao
+ *  @author An Tao
  *
  *  Copyright 2018, An Tao.  All rights reserved.
  *  https://github.com/an-tao/drogon
@@ -117,6 +117,7 @@ class Session
      * @code
        sessionPtr->insert("user name", userNameString);
        @endcode
+     * @note If the key already exists, the element is not inserted.
      */
     void insert(const std::string &key, const any &obj)
     {
@@ -130,6 +131,7 @@ class Session
      * @code
        sessionPtr->insert("user name", userNameString);
        @endcode
+     * @note If the key already exists, the element is not inserted.
      */
     void insert(const std::string &key, any &&obj)
     {

lib/src/ConfigLoader.cc

@@ -452,6 +452,7 @@ static void loadApp(const Json::Value &app)
                   << std::endl;
         exit(1);
     }
+    drogon::app().enableReusePort(app.get("reuse_port", false).asBool());
     drogon::app().setHomePage(app.get("home_page", "index.html").asString());
 }
 static void loadDbClients(const Json::Value &dbClients)

lib/src/HttpAppFrameworkImpl.h

@@ -488,6 +488,14 @@ class HttpAppFrameworkImpl : public HttpAppFramework
     {
         return usingCustomErrorHandler_;
     }
+    virtual void enableReusePort(bool enable = true) override
+    {
+        reusePort_ = enable;
+    }
+    virtual bool reusePort() const override
+    {
+        return reusePort_;
+    }
 
   private:
     virtual void registerHttpController(
@@ -581,6 +589,7 @@ class HttpAppFrameworkImpl : public HttpAppFramework
     static InitBeforeMainFunction initFirst_;
     bool enableServerHeader_{true};
     bool enableDateHeader_{true};
+    bool reusePort_{false};
     std::vector<std::function<void()>> beginningAdvices_;
     std::vector<std::function<bool(const trantor::InetAddress &,
                                    const trantor::InetAddress &)>>

lib/src/HttpServer.cc

@@ -1,7 +1,7 @@
 /**
  *
  *  @file HttpServer.cc
- *  An Tao
+ *  @author An Tao
  *
  *  Copyright 2018, An Tao.  All rights reserved.
  *  https://github.com/an-tao/drogon
@@ -158,7 +158,7 @@ HttpServer::HttpServer(
 #ifdef __linux__
     : server_(loop, listenAddr, name.c_str()),
 #else
-    : server_(loop, listenAddr, name.c_str(), true, false),
+    : server_(loop, listenAddr, name.c_str(), true, app().reusePort()),
 #endif
       httpAsyncCallback_(defaultHttpAsyncCallback),
       newWebsocketCallback_(defaultWebSockAsyncCallback),

lib/src/ListenerManager.cc

@@ -91,7 +91,7 @@ std::vector<trantor::EventLoop *> ListenerManager::createListeners(
             auto const &ip = listener.ip_;
             bool isIpv6 = ip.find(':') == std::string::npos ? false : true;
             std::shared_ptr<HttpServer> serverPtr;
-            if (i == 0)
+            if (i == 0 && !app().reusePort())
             {
                 DrogonFileLocker lock;
                 // Check whether the port is in use.