Session lazy creation

lib/inc/drogon/HttpAppFramework.h

@@ -79,6 +79,12 @@ using DefaultHandler =
                        std::function<void(const HttpResponsePtr &)> &&)>;
 using HttpHandlerInfo = std::tuple<std::string, HttpMethod, std::string>;
 
+enum class SessionMode
+{
+    kAuto = 0,
+    kManual = 1
+};
+
 #ifdef __cpp_impl_coroutine
 class HttpAppFramework;
 
@@ -913,6 +919,16 @@ class DROGON_EXPORT HttpAppFramework : public trantor::NonCopyable
                              idGeneratorCallback);
     }
 
+    /// Set session mode.
+    /**
+     * @param mode The number of seconds which is the timeout of a session
+     *
+     * @note
+     *
+     * This operation can be performed by an option in the configuration file.
+     */
+    virtual HttpAppFramework &setSessionMode(SessionMode mode) = 0;
+
     /// Register an advice called when starting a new session.
     /**
      * @param advice is called with the session id.

lib/inc/drogon/HttpRequest.h

@@ -292,6 +292,9 @@ class DROGON_EXPORT HttpRequest
         return session();
     }
 
+    /// Get the session to which the request belongs, create if not exists
+    virtual const SessionPtr &getOrCreateSession() = 0;
+
     /// Get the attributes store, users can add/get any type of data to/from
     /// this store
     virtual const AttributesPtr &attributes() const = 0;

lib/src/ConfigLoader.cc

@@ -276,7 +276,19 @@ static void loadApp(const Json::Value &app)
                                     maxAge);
     }
     else
+    {
         drogon::app().disableSession();
+    }
+    auto sessionMode = app.get("session_mode", "auto").asString();
+    if (sessionMode == "auto" || sessionMode == "AUTO")
+    {
+        drogon::app().setSessionMode(SessionMode::kAuto);
+    }
+    else
+    {
+        drogon::app().setSessionMode(SessionMode::kManual);
+    }
+
     // document root
     auto documentRoot = app.get("document_root", "").asString();
     if (documentRoot != "")

lib/src/HttpAppFrameworkImpl.cc

@@ -712,6 +712,10 @@ void HttpAppFrameworkImpl::findSessionForRequest(const HttpRequestImplPtr &req)
         bool needSetSessionid = false;
         if (sessionId.empty())
         {
+            if (sessionMode_ != SessionMode::kAuto)
+            {
+                return;
+            }
             sessionId = sessionIdGeneratorCallback_();
             needSetSessionid = true;
         }
@@ -720,6 +724,15 @@ void HttpAppFrameworkImpl::findSessionForRequest(const HttpRequestImplPtr &req)
     }
 }
 
+void HttpAppFrameworkImpl::createSessionForRequest(HttpRequestImpl *req)
+{
+    if (useSession_)
+    {
+        std::string sessionId = sessionIdGeneratorCallback_();
+        req->setSession(sessionManagerPtr_->getSession(sessionId, true));
+    }
+}
+
 std::vector<HttpHandlerInfo> HttpAppFrameworkImpl::getHandlersInfo() const
 {
     return HttpControllersRouter::instance().getHandlersInfo();

lib/src/HttpAppFrameworkImpl.h

@@ -215,6 +215,11 @@ class HttpAppFrameworkImpl final : public HttpAppFramework
         return *this;
     }
 
+    HttpAppFramework &setSessionMode(SessionMode mode) override
+    {
+        sessionMode_ = mode;
+    }
+
     HttpAppFramework &registerSessionStartAdvice(
         const AdviceStartSessionCallback &advice) override
     {
@@ -656,8 +661,8 @@ class HttpAppFrameworkImpl final : public HttpAppFramework
     // should return unsigned type!
     int64_t getConnectionCount() const override;
 
-    // TODO: move session related codes to its own singleton class
     void findSessionForRequest(const HttpRequestImplPtr &req);
+    void createSessionForRequest(HttpRequestImpl *req);
     HttpResponsePtr handleSessionForResponse(const HttpRequestImplPtr &req,
                                              const HttpResponsePtr &resp);
 
@@ -693,6 +698,7 @@ class HttpAppFrameworkImpl final : public HttpAppFramework
     int sessionMaxAge_{-1};
     size_t idleConnectionTimeout_{60};
     bool useSession_{false};
+    SessionMode sessionMode_{SessionMode::kAuto};
     std::string serverHeader_{"server: drogon/" + drogon::getVersion() +
                               "\r\n"};
 

lib/src/HttpRequestImpl.cc

@@ -1114,3 +1114,12 @@ void HttpRequestImpl::quitStreamMode()
     assert(!streamReaderPtr_);
     streamStatus_ = ReqStreamStatus::None;
 }
+
+const SessionPtr &HttpRequestImpl::getOrCreateSession()
+{
+    if (sessionPtr_)
+        return sessionPtr_;
+
+    HttpAppFrameworkImpl::instance().createSessionForRequest(this);
+    return sessionPtr_;
+}

lib/src/HttpRequestImpl.h

@@ -470,6 +470,8 @@ class HttpRequestImpl : public HttpRequest
         return sessionPtr_;
     }
 
+    const SessionPtr &getOrCreateSession() override;
+
     void setSession(const SessionPtr &session)
     {
         sessionPtr_ = session;

lib/src/HttpServer.cc

@@ -426,7 +426,6 @@ void HttpServer::onHttpRequest(
         return;
     }
 
-    // TODO: move session related codes to its own singleton class
     HttpAppFrameworkImpl::instance().findSessionForRequest(req);
     // pre-routing aop
     auto &aop = AopAdvice::instance();