我已经构建了一个简单的日志记录类,并希望确认它是线程安全的.基本上,将从不同的线程调用Log,RegisterLogger和UnRegisterLogger.日志将很少被调用(来自许多不同的线程)和RegisterLogger和UnRegisterLogger很少.
基本上我的问题可归结为：“读取TList< x>线程是否安全？”,也就是说我可以让多个线程同时访问TList.
IExecutionCounterLogger是一个带有Log方法的接口(与TExecutionCounterServer.Log具有相同的签名)
Type
TExecutionCounterServer = class
private
Loggers : TList<IExecutionCounterLogger>;
Synchronizer : TMultiReadExclusiveWriteSynchronizer;
public
procedure RegisterLogger(Logger : IExecutionCounterLogger);
procedure UnRegisterLogger(Logger : IExecutionCounterLogger);
procedure Log(const ClassName,MethodName : string; ExecutionTime_ms : integer);
constructor Create;
destructor Destroy; override;
end;
constructor TExecutionCounterServer.Create;
begin
Loggers := TList<IExecutionCounterLogger>.Create;
Synchronizer := TMultiReadExclusiveWriteSynchronizer.Create;
end;
destructor TExecutionCounterServer.Destroy;
begin
Loggers.Free;
Synchronizer.Free;
inherited;
end;
procedure TExecutionCounterServer.Log(const ClassName,MethodName: string; ExecutionTime_ms: integer);
var
Logger: IExecutionCounterLogger;
begin
Synchronizer.BeginRead;
try
for Logger in Loggers do
Logger.Log(ClassName,MethodName,ExecutionTime_ms);
finally
Synchronizer.EndRead;
end;
end;
procedure TExecutionCounterServer.RegisterLogger(Logger: IExecutionCounterLogger);
begin
Synchronizer.BeginWrite;
try
Loggers.Add(Logger);
finally
Synchronizer.EndWrite;
end;
end;
procedure TExecutionCounterServer.UnRegisterLogger(Logger: IExecutionCounterLogger);
var
i : integer;
begin
Synchronizer.BeginWrite;
try
i := Loggers.IndexOf(Logger);
if i = -1 then
raise Exception.Create('Logger not present');
Loggers.Delete(i);
finally
Synchronizer.EndWrite;
end;
end;
作为更多背景,这是从this question开始的.我基本上已经为(DCOM)DataSnap服务器的每个方法添加了一些工具,我也已经连接到每个TDataSnapProvider OnGetData和OnUpdateData事件.
解决方法
Are reads on
TList<T>thread safe? That is to say can I have multiple threads accessing aTList<T>at the same time?
这是线程安全的,不需要同步.多个线程可以安全地同时读取.这相当于(并且实际上实现为)从数组中读取.只有当您的某个线程修改了需要同步的列表时.
您的代码比此方案稍微复杂一些.您似乎需要满足修改列表的线程.但是你已经使用TMultiReadExclusiveWriteSynchronizer这样做了,这是一个非常好的解决方案.它允许多个读取线程同时操作,但任何写入线程都相对于所有其他线程进行序列化.
