Core/Networking: Rewrite networking threading model

Each network thread has its own io_service - this means that all operations on a given socket except queueing packets run from a single thread, removing the need for locking
Sending packets now writes to a lockfree intermediate queue directly, encryption is applied in network thread if it was required at the time of sending the packet

(cherry picked from commit 97a79af)

src/common/Threading/MPSCQueue.h

@@ -0,0 +1,83 @@
+/*
+ * Copyright (C) 2008-2016 TrinityCore <http://www.trinitycore.org/>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef MPSCQueue_h__
+#define MPSCQueue_h__
+
+#include <atomic>
+#include <utility>
+
+// C++ implementation of Dmitry Vyukov's lock free MPSC queue
+// http://www.1024cores.net/home/lock-free-algorithms/queues/non-intrusive-mpsc-node-based-queue
+template<typename T>
+class MPSCQueue
+{
+public:
+    MPSCQueue() : _head(new Node()), _tail(_head.load(std::memory_order_relaxed))
+    {
+        Node* front = _head.load(std::memory_order_relaxed);
+        front->Next.store(nullptr, std::memory_order_relaxed);
+    }
+
+    ~MPSCQueue()
+    {
+        T* output;
+        while (this->Dequeue(output))
+            ;
+
+        Node* front = _head.load(std::memory_order_relaxed);
+        delete front;
+    }
+
+    void Enqueue(T* input)
+    {
+        Node* node = new Node(input);
+        Node* prevHead = _head.exchange(node, std::memory_order_acq_rel);
+        prevHead->Next.store(node, std::memory_order_release);
+    }
+
+    bool Dequeue(T*& result)
+    {
+        Node* tail = _tail.load(std::memory_order_relaxed);
+        Node* next = tail->Next.load(std::memory_order_acquire);
+        if (!next)
+            return false;
+
+        result = next->Data;
+        _tail.store(next, std::memory_order_release);
+        delete tail;
+        return true;
+    }
+
+private:
+    struct Node
+    {
+        Node() = default;
+        explicit Node(T* data) : Data(data) { Next.store(nullptr, std::memory_order_relaxed); }
+
+        T* Data;
+        std::atomic<Node*> Next;
+    };
+
+    std::atomic<Node*> _head;
+    std::atomic<Node*> _tail;
+
+    MPSCQueue(MPSCQueue const&) = delete;
+    MPSCQueue& operator=(MPSCQueue const&) = delete;
+};
+
+#endif // MPSCQueue_h__

src/server/authserver/Server/AuthSession.cpp

@@ -274,10 +274,7 @@ void AuthSession::SendPacket(ByteBuffer& packet)
     {
         MessageBuffer buffer;
         buffer.Write(packet.contents(), packet.size());
-
-        std::unique_lock<std::mutex> guard(_writeLock);
-
-        QueuePacket(std::move(buffer), guard);
+        QueuePacket(std::move(buffer));
     }
 }
 

src/server/authserver/Server/AuthSocketMgr.h

@@ -21,8 +21,6 @@
 #include "SocketMgr.h"
 #include "AuthSession.h"
 
-void OnSocketAccept(tcp::socket&& sock);
-
 class AuthSocketMgr : public SocketMgr<AuthSession>
 {
     typedef SocketMgr<AuthSession> BaseSocketMgr;
@@ -39,7 +37,7 @@ class AuthSocketMgr : public SocketMgr<AuthSession>
         if (!BaseSocketMgr::StartNetwork(service, bindIp, port))
             return false;
 
-        _acceptor->AsyncAcceptManaged(&OnSocketAccept);
+        _acceptor->AsyncAcceptWithCallback<&AuthSocketMgr::OnSocketAccept>();
         return true;
     }
 
@@ -48,14 +46,13 @@ class AuthSocketMgr : public SocketMgr<AuthSession>
     {
         return new NetworkThread<AuthSession>[1];
     }
+
+    static void OnSocketAccept(tcp::socket&& sock, uint32 threadIndex)
+    {
+        Instance().OnSocketOpen(std::forward<tcp::socket>(sock), threadIndex);
+    }
 };
 
 #define sAuthSocketMgr AuthSocketMgr::Instance()
 
-void OnSocketAccept(tcp::socket&& sock)
-{
-    sAuthSocketMgr.OnSocketOpen(std::forward<tcp::socket>(sock));
-}
-
-
 #endif // AuthSocketMgr_h__

src/server/game/Server/WorldSocket.cpp

@@ -25,6 +25,17 @@
 
 #include <memory>
 
+class EncryptablePacket : public WorldPacket
+{
+public:
+    EncryptablePacket(WorldPacket const& packet, bool encrypt) : WorldPacket(packet), _encrypt(encrypt) { }
+
+    bool NeedsEncryption() const { return _encrypt; }
+
+private:
+    bool _encrypt;
+};
+
 using boost::asio::ip::tcp;
 
 WorldSocket::WorldSocket(tcp::socket&& socket)
@@ -40,11 +51,8 @@ void WorldSocket::Start()
     stmt->setString(0, ip_address);
     stmt->setUInt32(1, inet_addr(ip_address.c_str()));
 
-    {
-        std::lock_guard<std::mutex> guard(_queryLock);
-        _queryCallback = io_service().wrap(std::bind(&WorldSocket::CheckIpCallback, this, std::placeholders::_1));
-        _queryFuture = LoginDatabase.AsyncQuery(stmt);
-    }
+    _queryCallback = std::bind(&WorldSocket::CheckIpCallback, this, std::placeholders::_1);
+    _queryFuture = LoginDatabase.AsyncQuery(stmt);
 }
 
 void WorldSocket::CheckIpCallback(PreparedQueryResult result)
@@ -78,17 +86,50 @@ void WorldSocket::CheckIpCallback(PreparedQueryResult result)
 
 bool WorldSocket::Update()
 {
+    EncryptablePacket* queued;
+    MessageBuffer buffer;
+    while (_bufferQueue.Dequeue(queued))
+    {
+        ServerPktHeader header(queued->size() + 2, queued->GetOpcode());
+        if (queued->NeedsEncryption())
+            _authCrypt.EncryptSend(header.header, header.getHeaderLength());
+
+        if (buffer.GetRemainingSpace() < queued->size() + header.getHeaderLength())
+        {
+            QueuePacket(std::move(buffer));
+            buffer.Resize(4096);
+        }
+
+        if (buffer.GetRemainingSpace() >= queued->size() + header.getHeaderLength())
+        {
+            buffer.Write(header.header, header.getHeaderLength());
+            if (!queued->empty())
+                buffer.Write(queued->contents(), queued->size());
+        }
+        else    // single packet larger than 4096 bytes
+        {
+            MessageBuffer packetBuffer(queued->size() + header.getHeaderLength());
+            packetBuffer.Write(header.header, header.getHeaderLength());
+            if (!queued->empty())
+                packetBuffer.Write(queued->contents(), queued->size());
+
+            QueuePacket(std::move(packetBuffer));
+        }
+
+        delete queued;
+    }
+
+    if (buffer.GetActiveSize() > 0)
+        QueuePacket(std::move(buffer));
+
     if (!BaseSocket::Update())
         return false;
 
+    if (_queryFuture.valid() && _queryFuture.wait_for(std::chrono::seconds(0)) == std::future_status::ready)
     {
-        std::lock_guard<std::mutex> guard(_queryLock);
-        if (_queryFuture.valid() && _queryFuture.wait_for(std::chrono::seconds(0)) == std::future_status::ready)
-        {
-            auto callback = std::move(_queryCallback);
-            _queryCallback = nullptr;
-            callback(_queryFuture.get());
-        }
+        auto callback = _queryCallback;
+        _queryCallback = nullptr;
+        callback(_queryFuture.get());
     }
 
     return true;
@@ -351,29 +392,7 @@ void WorldSocket::SendPacket(WorldPacket const& packet)
     if (sPacketLog->CanLogPacket())
         sPacketLog->LogPacket(packet, SERVER_TO_CLIENT, GetRemoteIpAddress(), GetRemotePort());
 
-    ServerPktHeader header(packet.size() + 2, packet.GetOpcode());
-
-    std::unique_lock<std::mutex> guard(_writeLock);
-
-    _authCrypt.EncryptSend(header.header, header.getHeaderLength());
-
-#ifndef TC_SOCKET_USE_IOCP
-    if (_writeQueue.empty() && _writeBuffer.GetRemainingSpace() >= header.getHeaderLength() + packet.size())
-    {
-        _writeBuffer.Write(header.header, header.getHeaderLength());
-        if (!packet.empty())
-            _writeBuffer.Write(packet.contents(), packet.size());
-    }
-    else
-#endif
-    {
-        MessageBuffer buffer(header.getHeaderLength() + packet.size());
-        buffer.Write(header.header, header.getHeaderLength());
-        if (!packet.empty())
-            buffer.Write(packet.contents(), packet.size());
-
-        QueuePacket(std::move(buffer), guard);
-    }
+    _bufferQueue.Enqueue(new EncryptablePacket(packet, _authCrypt.IsInitialized()));
 }
 
 void WorldSocket::HandleAuthSession(WorldPacket& recvPacket)
@@ -398,11 +417,8 @@ void WorldSocket::HandleAuthSession(WorldPacket& recvPacket)
     stmt->setInt32(0, int32(realmID));
     stmt->setString(1, authSession->Account);
 
-    {
-        std::lock_guard<std::mutex> guard(_queryLock);
-        _queryCallback = io_service().wrap(std::bind(&WorldSocket::HandleAuthSessionCallback, this, authSession, std::placeholders::_1));
-        _queryFuture = LoginDatabase.AsyncQuery(stmt);
-    }
+    _queryCallback = std::bind(&WorldSocket::HandleAuthSessionCallback, this, authSession, std::placeholders::_1);
+    _queryFuture = LoginDatabase.AsyncQuery(stmt);
 }
 
 void WorldSocket::HandleAuthSessionCallback(std::shared_ptr<AuthSession> authSession, PreparedQueryResult result)
@@ -559,7 +575,7 @@ void WorldSocket::HandleAuthSessionCallback(std::shared_ptr<AuthSession> authSes
     if (wardenActive)
         _worldSession->InitWarden(&account.SessionKey, account.OS);
 
-    _queryCallback = io_service().wrap(std::bind(&WorldSocket::LoadSessionPermissionsCallback, this, std::placeholders::_1));
+    _queryCallback = std::bind(&WorldSocket::LoadSessionPermissionsCallback, this, std::placeholders::_1);
     _queryFuture = _worldSession->LoadPermissionsAsync();
     AsyncRead();
 }

src/server/game/Server/WorldSocket.h

@@ -26,11 +26,13 @@
 #include "Util.h"
 #include "WorldPacket.h"
 #include "WorldSession.h"
+#include "MPSCQueue.h"
 #include <chrono>
 #include <boost/asio/ip/tcp.hpp>
 #include <boost/asio/buffer.hpp>
 
 using boost::asio::ip::tcp;
+class EncryptablePacket;
 
 #pragma pack(push, 1)
 
@@ -104,8 +106,8 @@ class WorldSocket : public Socket<WorldSocket>
 
     MessageBuffer _headerBuffer;
     MessageBuffer _packetBuffer;
+    MPSCQueue<EncryptablePacket> _bufferQueue;
 
-    std::mutex _queryLock;
     PreparedQueryResultFuture _queryFuture;
     std::function<void(PreparedQueryResult&&)> _queryCallback;
     std::string _ipCountry;

src/server/game/Server/WorldSocketMgr.cpp

@@ -24,9 +24,9 @@
 
 #include <boost/system/error_code.hpp>
 
-static void OnSocketAccept(tcp::socket&& sock)
+static void OnSocketAccept(tcp::socket&& sock, uint32 threadIndex)
 {
-    sWorldSocketMgr.OnSocketOpen(std::forward<tcp::socket>(sock));
+    sWorldSocketMgr.OnSocketOpen(std::forward<tcp::socket>(sock), threadIndex);
 }
 
 class WorldSocketThread : public NetworkThread<WorldSocket>
@@ -67,7 +67,9 @@ bool WorldSocketMgr::StartNetwork(boost::asio::io_service& service, std::string
 
     BaseSocketMgr::StartNetwork(service, bindIp, port);
 
-    _acceptor->AsyncAcceptManaged(&OnSocketAccept);
+    _acceptor->SetSocketFactory(std::bind(&BaseSocketMgr::GetSocketForAccept, this));
+
+    _acceptor->AsyncAcceptWithCallback<&OnSocketAccept>();
 
     sScriptMgr->OnNetworkStart();
     return true;
@@ -80,7 +82,7 @@ void WorldSocketMgr::StopNetwork()
     sScriptMgr->OnNetworkStop();
 }
 
-void WorldSocketMgr::OnSocketOpen(tcp::socket&& sock)
+void WorldSocketMgr::OnSocketOpen(tcp::socket&& sock, uint32 threadIndex)
 {
     // set some options here
     if (_socketSendBufferSize >= 0)
@@ -108,7 +110,7 @@ void WorldSocketMgr::OnSocketOpen(tcp::socket&& sock)
 
     //sock->m_OutBufferSize = static_cast<size_t> (m_SockOutUBuff);
 
-    BaseSocketMgr::OnSocketOpen(std::forward<tcp::socket>(sock));
+    BaseSocketMgr::OnSocketOpen(std::forward<tcp::socket>(sock), threadIndex);
 }
 
 NetworkThread<WorldSocket>* WorldSocketMgr::CreateThreads() const

src/server/game/Server/WorldSocketMgr.h

@@ -47,7 +47,7 @@ class WorldSocketMgr : public SocketMgr<WorldSocket>
     /// Stops all network threads, It will wait for all running threads .
     void StopNetwork() override;
 
-    void OnSocketOpen(tcp::socket&& sock) override;
+    void OnSocketOpen(tcp::socket&& sock, uint32 threadIndex) override;
 
 protected:
     WorldSocketMgr();