[Bug Fix] Fix for undefined MySQL library behavior. (#2834)

* MYSQL objects cannot be copied in a well defined way, this removes the copy and replaces it with another connection

* Change to share underlying pointers.

* Push up mutex changes

* Post rebase

* Formatting

---------

Co-authored-by: KimLS <KimLS@peqtgc.com>
Co-authored-by: Akkadius <akkadius1@gmail.com>

world/cli/database_concurrency.cpp

@@ -0,0 +1,73 @@
+#include <thread>
+#include "../../common/repositories/zone_repository.h"
+#include "../../common/eqemu_config.h"
+#include <signal.h>
+
+Database db;
+Database db2;
+
+volatile sig_atomic_t stop;
+void inthand(int signum) {
+	stop = 1;
+}
+
+[[noreturn]] void DatabaseTest()
+{
+	while (true) {
+		LogInfo("DatabaseTest Query");
+		db.QueryDatabase("SELECT 1");
+	}
+}
+
+[[noreturn]] void DatabaseTestSecondConnection()
+{
+	while (true) {
+		LogInfo("DatabaseTest Query");
+		db2.QueryDatabase("SELECT 1");
+	}
+}
+
+
+void WorldserverCLI::TestDatabaseConcurrency(int argc, char **argv, argh::parser &cmd, std::string &description)
+{
+	description = "Test command to test database concurrency";
+
+	if (cmd[{"-h", "--help"}]) {
+		return;
+	}
+
+	signal(SIGINT, inthand);
+
+	LogInfo("Database test");
+
+	auto mutex = new Mutex;
+
+	auto c = EQEmuConfig::get();
+	LogInfo("Connecting to MySQL");
+	if (!db.Connect(
+		c->DatabaseHost.c_str(),
+		c->DatabaseUsername.c_str(),
+		c->DatabasePassword.c_str(),
+		c->DatabaseDB.c_str(),
+		c->DatabasePort
+	)) {
+		LogError("Cannot continue without a database connection");
+		return;
+	}
+
+	db.SetMutex(mutex);
+
+	db2.SetMySQL(db);
+
+	db2.SetMutex(mutex);
+
+	std::thread(DatabaseTest).detach();
+	std::thread(DatabaseTest).detach();
+	std::thread(DatabaseTestSecondConnection).detach();
+
+	while (!stop) {
+
+	}
+
+	safe_delete(mutex);
+}

world/main.cpp

@@ -478,6 +478,8 @@ int main(int argc, char **argv)
 	LogInfo("Signaling HTTP service to stop");
 	LogSys.CloseFileLogs();
 
+	WorldBoot::Shutdown();
+
 	return 0;
 }
 

world/world_boot.cpp

@@ -30,6 +30,8 @@
 extern ZSList      zoneserver_list;
 extern WorldConfig Config;
 
+auto mutex = new Mutex;
+
 void WorldBoot::GMSayHookCallBackProcessWorld(uint16 log_category, const char *func, std::string message)
 {
 	// we don't want to loop up with chat messages
@@ -136,9 +138,7 @@ bool WorldBoot::LoadDatabaseConnections()
 		return false;
 	}
 
-	/**
-	 * Multi-tenancy: Content database
-	 */
+	// Multi-tenancy - content database
 	if (!c->ContentDbHost.empty()) {
 		if (!content_db.Connect(
 			c->ContentDbHost.c_str(),
@@ -153,7 +153,12 @@ bool WorldBoot::LoadDatabaseConnections()
 		}
 	}
 	else {
-		content_db.SetMysql(database.getMySQL());
+		content_db.SetMySQL(database);
+		// when database and content_db share the same underlying mysql connection
+		// it needs to be protected by a shared mutex otherwise we produce concurrency issues
+		// when database actions are occurring in different threads
+		database.SetMutex(mutex);
+		content_db.SetMutex(mutex);
 	}
 
 	return true;
@@ -652,3 +657,8 @@ void WorldBoot::CheckForPossibleConfigurationIssues()
 	}
 }
 
+void WorldBoot::Shutdown()
+{
+	safe_delete(mutex);
+}
+

world/world_boot.h

@@ -15,6 +15,7 @@ public:
 	static void RegisterLoginservers();
 	static bool DatabaseLoadRoutines(int argc, char **argv);
 	static void CheckForPossibleConfigurationIssues();
+	static void Shutdown();
 };
 
 

world/world_server_cli.cpp

@@ -31,10 +31,12 @@ void WorldserverCLI::CommandHandler(int argc, char **argv)
 	function_map["test:expansion"]              = &WorldserverCLI::ExpansionTestCommand;
 	function_map["test:repository"]             = &WorldserverCLI::TestRepository;
 	function_map["test:repository2"]            = &WorldserverCLI::TestRepository2;
+	function_map["test:db-concurrency"]         = &WorldserverCLI::TestDatabaseConcurrency;
 
 	EQEmuCommand::HandleMenu(function_map, cmd, argc, argv);
 }
 
+#include "cli/database_concurrency.cpp"
 #include "cli/copy_character.cpp"
 #include "cli/database_dump.cpp"
 #include "cli/database_get_schema.cpp"

world/world_server_cli.h

@@ -18,6 +18,7 @@ public:
 	static void ExpansionTestCommand(int argc, char **argv, argh::parser &cmd, std::string &description);
 	static void TestRepository(int argc, char **argv, argh::parser &cmd, std::string &description);
 	static void TestRepository2(int argc, char **argv, argh::parser &cmd, std::string &description);
+	static void TestDatabaseConcurrency(int argc, char **argv, argh::parser &cmd, std::string &description);
 };