Core/DBLayer: Implement async transaction completion callbacks

src/server/database/Database/DatabaseEnvFwd.h

@@ -24,9 +24,9 @@
 class Field;
 
 class ResultSet;
-typedef std::shared_ptr<ResultSet> QueryResult;
-typedef std::future<QueryResult> QueryResultFuture;
-typedef std::promise<QueryResult> QueryResultPromise;
+using QueryResult = std::shared_ptr<ResultSet>;
+using QueryResultFuture = std::future<QueryResult>;
+using QueryResultPromise = std::promise<QueryResult>;
 
 class CharacterDatabaseConnection;
 class HotfixDatabaseConnection;
@@ -44,17 +44,27 @@ using LoginDatabasePreparedStatement = PreparedStatement<LoginDatabaseConnection
 using WorldDatabasePreparedStatement = PreparedStatement<WorldDatabaseConnection>;
 
 class PreparedResultSet;
-typedef std::shared_ptr<PreparedResultSet> PreparedQueryResult;
-typedef std::future<PreparedQueryResult> PreparedQueryResultFuture;
-typedef std::promise<PreparedQueryResult> PreparedQueryResultPromise;
+using PreparedQueryResult = std::shared_ptr<PreparedResultSet>;
+using PreparedQueryResultFuture = std::future<PreparedQueryResult>;
+using PreparedQueryResultPromise = std::promise<PreparedQueryResult>;
 
 class QueryCallback;
 
+template<typename T>
+class AsyncCallbackProcessor;
+
+using QueryCallbackProcessor = AsyncCallbackProcessor<QueryCallback>;
+
 class TransactionBase;
 
+using TransactionFuture = std::future<bool>;
+using TransactionPromise = std::promise<bool>;
+
 template<typename T>
 class Transaction;
 
+class TransactionCallback;
+
 template<typename T>
 using SQLTransaction = std::shared_ptr<Transaction<T>>;
 
@@ -64,8 +74,8 @@ using LoginDatabaseTransaction = SQLTransaction<LoginDatabaseConnection>;
 using WorldDatabaseTransaction = SQLTransaction<WorldDatabaseConnection>;
 
 class SQLQueryHolderBase;
-typedef std::future<SQLQueryHolderBase*> QueryResultHolderFuture;
-typedef std::promise<SQLQueryHolderBase*> QueryResultHolderPromise;
+using QueryResultHolderFuture = std::future<SQLQueryHolderBase*>;
+using QueryResultHolderPromise = std::promise<SQLQueryHolderBase*>;
 
 template<typename T>
 class SQLQueryHolder;

src/server/database/Database/DatabaseWorkerPool.cpp

@@ -261,6 +261,32 @@ void DatabaseWorkerPool<T>::CommitTransaction(SQLTransaction<T> transaction)
     Enqueue(new TransactionTask(transaction));
 }
 
+template <class T>
+TransactionCallback DatabaseWorkerPool<T>::AsyncCommitTransaction(SQLTransaction<T> transaction)
+{
+#ifdef TRINITY_DEBUG
+    //! Only analyze transaction weaknesses in Debug mode.
+    //! Ideally we catch the faults in Debug mode and then correct them,
+    //! so there's no need to waste these CPU cycles in Release mode.
+    switch (transaction->GetSize())
+    {
+        case 0:
+            TC_LOG_DEBUG("sql.driver", "Transaction contains 0 queries. Not executing.");
+            return;
+        case 1:
+            TC_LOG_DEBUG("sql.driver", "Warning: Transaction only holds 1 query, consider removing Transaction context in code.");
+            break;
+        default:
+            break;
+    }
+#endif // TRINITY_DEBUG
+
+    TransactionWithResultTask* task = new TransactionWithResultTask(transaction);
+    TransactionFuture result = task->GetFuture();
+    Enqueue(task);
+    return TransactionCallback(std::move(result));
+}
+
 template <class T>
 void DatabaseWorkerPool<T>::DirectCommitTransaction(SQLTransaction<T>& transaction)
 {

src/server/database/Database/DatabaseWorkerPool.h

@@ -173,6 +173,10 @@ class DatabaseWorkerPool
         //! were appended to the transaction will be respected during execution.
         void CommitTransaction(SQLTransaction<T> transaction);
 
+        //! Enqueues a collection of one-way SQL operations (can be both adhoc and prepared). The order in which these operations
+        //! were appended to the transaction will be respected during execution.
+        TransactionCallback AsyncCommitTransaction(SQLTransaction<T> transaction);
+
         //! Directly executes a collection of one-way SQL operations (can be both adhoc and prepared). The order in which these operations
         //! were appended to the transaction will be respected during execution.
         void DirectCommitTransaction(SQLTransaction<T>& transaction);

src/server/database/Database/QueryCallback.cpp

@@ -175,7 +175,7 @@ void QueryCallback::SetNextQuery(QueryCallback&& next)
     MoveFrom(this, std::move(next));
 }
 
-QueryCallback::Status QueryCallback::InvokeIfReady()
+bool QueryCallback::InvokeIfReady()
 {
     QueryCallbackData& callback = _callbacks.front();
     auto checkStateAndReturnCompletion = [this]()
@@ -185,15 +185,15 @@ QueryCallback::Status QueryCallback::InvokeIfReady()
         if (_callbacks.empty())
         {
             ASSERT(!hasNext);
-            return Completed;
+            return true;
         }
 
         // abort chain
         if (!hasNext)
-            return Completed;
+            return true;
 
         ASSERT(_isPrepared == _callbacks.front()._isPrepared);
-        return NextStep;
+        return false;
     };
 
     if (!_isPrepared)
@@ -217,5 +217,5 @@ QueryCallback::Status QueryCallback::InvokeIfReady()
         }
     }
 
-    return NotReady;
+    return false;
 }

src/server/database/Database/QueryCallback.h

@@ -44,14 +44,8 @@ public:
     // Moves std::future from next to this object
     void SetNextQuery(QueryCallback&& next);
 
-    enum Status
-    {
-        NotReady,
-        NextStep,
-        Completed
-    };
-
-    Status InvokeIfReady();
+    // returns true when completed
+    bool InvokeIfReady();
 
 private:
     QueryCallback(QueryCallback const& right) = delete;

src/server/database/Database/QueryCallbackProcessor.cpp

@@ -1,48 +0,0 @@
-/*
- * This file is part of the TrinityCore Project. See AUTHORS file for Copyright information
- *
- * 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/>.
- */
-
-#include "QueryCallbackProcessor.h"
-#include "QueryCallback.h"
-#include <algorithm>
-
-QueryCallbackProcessor::QueryCallbackProcessor()
-{
-}
-
-QueryCallbackProcessor::~QueryCallbackProcessor()
-{
-}
-
-void QueryCallbackProcessor::AddQuery(QueryCallback&& query)
-{
-    _callbacks.emplace_back(std::move(query));
-}
-
-void QueryCallbackProcessor::ProcessReadyQueries()
-{
-    if (_callbacks.empty())
-        return;
-
-    std::vector<QueryCallback> updateCallbacks{ std::move(_callbacks) };
-
-    updateCallbacks.erase(std::remove_if(updateCallbacks.begin(), updateCallbacks.end(), [](QueryCallback& callback)
-    {
-        return callback.InvokeIfReady() == QueryCallback::Completed;
-    }), updateCallbacks.end());
-
-    _callbacks.insert(_callbacks.end(), std::make_move_iterator(updateCallbacks.begin()), std::make_move_iterator(updateCallbacks.end()));
-}

src/server/database/Database/QueryCallbackProcessor.h

@@ -1,42 +0,0 @@
-/*
- * This file is part of the TrinityCore Project. See AUTHORS file for Copyright information
- *
- * 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 QueryCallbackProcessor_h__
-#define QueryCallbackProcessor_h__
-
-#include "Define.h"
-#include <vector>
-
-class QueryCallback;
-
-class TC_DATABASE_API QueryCallbackProcessor
-{
-public:
-    QueryCallbackProcessor();
-    ~QueryCallbackProcessor();
-
-    void AddQuery(QueryCallback&& query);
-    void ProcessReadyQueries();
-
-private:
-    QueryCallbackProcessor(QueryCallbackProcessor const&) = delete;
-    QueryCallbackProcessor& operator=(QueryCallbackProcessor const&) = delete;
-
-    std::vector<QueryCallback> _callbacks;
-};
-
-#endif // QueryCallbackProcessor_h__

src/server/database/Database/Transaction.cpp

@@ -70,7 +70,7 @@ void TransactionBase::Cleanup()
 
 bool TransactionTask::Execute()
 {
-    int errorCode = m_conn->ExecuteTransaction(m_trans);
+    int errorCode = TryExecute();
     if (!errorCode)
         return true;
 
@@ -85,7 +85,7 @@ bool TransactionTask::Execute()
 
         for (uint32 loopDuration = 0, startMSTime = getMSTime(); loopDuration <= DEADLOCK_MAX_RETRY_TIME_MS; loopDuration = GetMSTimeDiffToNow(startMSTime))
         {
-            if (!m_conn->ExecuteTransaction(m_trans))
+            if (!TryExecute())
                 return true;
 
             TC_LOG_WARN("sql.sql", "Deadlocked SQL Transaction, retrying. Loop timer: %u ms, Thread Id: %s", loopDuration, threadId.c_str());
@@ -95,7 +95,60 @@ bool TransactionTask::Execute()
     }
 
     // Clean up now.
-    m_trans->Cleanup();
+    CleanupOnFailure();
 
     return false;
 }
+
+int TransactionTask::TryExecute()
+{
+    return m_conn->ExecuteTransaction(m_trans);
+}
+
+void TransactionTask::CleanupOnFailure()
+{
+    m_trans->Cleanup();
+}
+
+bool TransactionWithResultTask::Execute()
+{
+    int errorCode = TryExecute();
+    if (!errorCode)
+    {
+        m_result.set_value(true);
+        return true;
+    }
+
+    if (errorCode == ER_LOCK_DEADLOCK)
+    {
+        // Make sure only 1 async thread retries a transaction so they don't keep dead-locking each other
+        std::lock_guard<std::mutex> lock(_deadlockLock);
+        uint8 loopBreaker = 5;  // Handle MySQL Errno 1213 without extending deadlock to the core itself
+        for (uint8 i = 0; i < loopBreaker; ++i)
+        {
+            if (!TryExecute())
+            {
+                m_result.set_value(true);
+                return true;
+            }
+        }
+    }
+
+    // Clean up now.
+    CleanupOnFailure();
+    m_result.set_value(false);
+
+    return false;
+}
+
+bool TransactionCallback::InvokeIfReady()
+{
+    if (m_future.valid() && m_future.wait_for(std::chrono::seconds(0)) == std::future_status::ready)
+    {
+        m_callback(m_future.get());
+        return true;
+    }
+
+    return false;
+}
+

src/server/database/Database/Transaction.h

@@ -22,6 +22,7 @@
 #include "DatabaseEnvFwd.h"
 #include "SQLOperation.h"
 #include "StringFormat.h"
+#include <functional>
 #include <mutex>
 #include <vector>
 
@@ -73,6 +74,7 @@ class TC_DATABASE_API TransactionTask : public SQLOperation
 {
     template <class T> friend class DatabaseWorkerPool;
     friend class DatabaseWorker;
+    friend class TransactionCallback;
 
     public:
         TransactionTask(std::shared_ptr<TransactionBase> trans) : m_trans(trans) { }
@@ -80,9 +82,43 @@ class TC_DATABASE_API TransactionTask : public SQLOperation
 
     protected:
         bool Execute() override;
+        int TryExecute();
+        void CleanupOnFailure();
 
         std::shared_ptr<TransactionBase> m_trans;
         static std::mutex _deadlockLock;
 };
 
+class TC_DATABASE_API TransactionWithResultTask : public TransactionTask
+{
+public:
+    TransactionWithResultTask(std::shared_ptr<TransactionBase> trans) : TransactionTask(trans) { }
+
+    TransactionFuture GetFuture() { return m_result.get_future(); }
+
+protected:
+    bool Execute() override;
+
+    TransactionPromise m_result;
+};
+
+class TC_DATABASE_API TransactionCallback
+{
+public:
+    TransactionCallback(TransactionFuture&& future) : m_future(std::move(future)) { }
+    TransactionCallback(TransactionCallback&&) = default;
+
+    TransactionCallback& operator=(TransactionCallback&&) = default;
+
+    void AfterComplete(std::function<void(bool)> callback) &
+    {
+        m_callback = std::move(callback);
+    }
+
+    bool InvokeIfReady();
+
+    TransactionFuture m_future;
+    std::function<void(bool)> m_callback;
+};
+
 #endif