Question

我感兴趣的是计时调用数据库+其他函数来为我的应用程序的性能构建一些指标。我使用了秒表和一个指标对象，但似乎并不总是给出正确的值。有时调用函数所用的时间与所有调用完全相同，这是不现实的......

我发现问题的原因是由Metrics对象属性值引起的。当其他线程生成的度量标准的其他实例被赋值时，将覆盖一个Metrics对象的值。虽然每个线程创建一个新实例，但似乎属性值是每个引用。

在多个线程共享的对象中实现唯一性的最佳方法是什么？

以下代码：

private Metrics Metrics;
private Stopwatch Stopwatch;
private int DegreeOfParallelism { get { return Convert.ToInt32(ConfigurationManager.AppSettings["DegreeOfParallelism"].ToString()); } }

var lOptions = new ParallelOptions() { MaxDegreeOfParallelism = DegreeOfParallelism };
Parallel.ForEach(RequestBag, lOptions, (lItem, loopState) =>
{
    if (!string.IsNullOrEmpty(lItem.XmlRequest))
    {
        try
        {
            Metrics = new Metrics();
            Stopwatch = new Stopwatch();
            Stopwatch.Start();
            ObjRef = new Object();
            lItem.XmlRequest = ObjRef.GetDecision(Username, Password);
            Stopwatch.Stop();
            Metrics.ElapsedTime = string.Format("{0:0.00}", Stopwatch.Elapsed.TotalSeconds);

            Stopwatch.Restart();
            if (!string.IsNullOrEmpty(DBConnectionString))
            {
                DataAccess = new DataAccess2(DBConnectionString);
                DataAccess.WriteToDB(lItem.XmlRequest);  
            }
            Stopwatch.Stop();
            Metrics.DbFuncCallTime = string.Format("{0:0.00}", Stopwatch.Elapsed.TotalSeconds); 
        }
        catch (Exception pEx)
        { 
            KeepLog(pEx);
            Metrics.HasFailed = true;
        }
        finally
        {
            ProcessedIdsBag.Add(lItem.OrderId);
            Metrics.ProcessedOrderId = lItem.OrderId;
            Metrics.DegreeOfParallelism = DegreeOfParallelism;
            Metrics.TotalNumOfOrders = NumberOfOrders;
            Metrics.TotalNumOfOrdersProcessed = ProcessedIdsBag.Count;
            pBackgroundWorker.ReportProgress(Metrics.GetProgressPercentage(NumberOfOrders, ProcessedIdsBag.Count), Metrics);

            RequestBag.TryTake(out lItem);
        }
    }
});

非常感谢任何帮助。谢谢， [R

Answer 1

您希望做的是为每次迭代创建一个指标对象，然后在最后聚合它们：

private ConcurrentBag<Metrics> allMetrics = new ConcurrentBag<Metrics>();
private int DegreeOfParallelism { get { return Convert.ToInt32(ConfigurationManager.AppSettings["DegreeOfParallelism"].ToString()); } }

var lOptions = new ParallelOptions() { MaxDegreeOfParallelism = DegreeOfParallelism };
Parallel.ForEach(RequestBag, lOptions, (lItem, loopState) =>
{
    if (!string.IsNullOrEmpty(lItem.XmlRequest))
    {
        try
        {
            var Metrics = new Metrics();
            var Stopwatch = new Stopwatch();
            Stopwatch.Start();
            ObjRef = new Object();
            lItem.XmlRequest = ObjRef.GetDecision(Username, Password);
            Stopwatch.Stop();
            Metrics.ElapsedTime = string.Format("{0:0.00}", Stopwatch.Elapsed.TotalSeconds);

            Stopwatch.Restart();
            if (!string.IsNullOrEmpty(DBConnectionString))
            {
                DataAccess = new DataAccess2(DBConnectionString);
                DataAccess.WriteToDB(lItem.XmlRequest);  
            }
            Stopwatch.Stop();
            Metrics.DbFuncCallTime = string.Format("{0:0.00}", Stopwatch.Elapsed.TotalSeconds); 
        }
        catch (Exception pEx)
        { 
            KeepLog(pEx);
            Metrics.HasFailed = true;
        }
        finally
        {
            ProcessedIdsBag.Add(lItem.OrderId);
            Metrics.ProcessedOrderId = lItem.OrderId;
            Metrics.DegreeOfParallelism = DegreeOfParallelism;
            Metrics.TotalNumOfOrders = NumberOfOrders;
            Metrics.TotalNumOfOrdersProcessed = ProcessedIdsBag.Count;
            pBackgroundWorker.ReportProgress(Metrics.GetProgressPercentage(NumberOfOrders, ProcessedIdsBag.Count), Metrics);

            RequestBag.TryTake(out lItem);
            allMetrics.add(Metrics);
        }
    }
});

// Aggregate everything in AllMetrics here

Answer 2

您需要更改秒表和指标变量的范围。

目前，每个线程共享相同的Metrics变量。一旦线程进入try块，它就会创建一个新的Metrics实例（正确），但会将其作为共享变量（错误地）。所有其他线程在读取共享变量时将看到新实例，直到下一个线程出现并开始整个过程。

移动

private Metrics Metrics;
private Stopwatch Stopwatch;

到你的循环里面

Parallel.ForEach(RequestBag, lOptions, (lItem, loopState) =>
{
    private Metrics Metrics;
    private Stopwatch Stopwatch;
...

这将通过循环给每个迭代它自己的变量，在该变量中存储它自己的对象实例。

在多个线程共享的对象中实现唯一性的最佳方法是什么？

2 个答案: