调用基于异步任务的WCF方法是否利用I/O完成端口或线程池线程来调用延续?
本文关键字：线程 调用 延续 异步 于异步 任务 是否 方法 WCF | 更新日期: 2023-09-27 17:50:45
我有以下WCF合同:
[ServiceContract(Namespace = "http://abc/Services/AdminService")]
public interface IAdminService
{
[OperationContract]
string GetServiceVersion();
// More methods here
}
GetServiceVersion是一个返回字符串的简单方法。它被用作ping来检查服务是否可达。
现在我想异步调用它，认为这将比使用。net线程在后台调用它更有效。
所以，我想出了下面这个接口:
[ServiceContract(Namespace = "http://abc/Services/AdminService")]
public interface IMiniAdminService
{
[OperationContract(Action = "http://abc/Services/AdminService/IAdminService/GetServiceVersion", ReplyAction = "http://abc/Services/AdminService/IAdminService/GetServiceVersionResponse")]
Task<string> GetServiceVersionAsync();
}
这使得异步调用GetServiceVersion API成为可能:
var tmp = new ChannelFactory<IAdminService>("AdminServiceClientEndpoint");
var channelFactory = new ChannelFactory<IMiniAdminService>(tmp.Endpoint.Binding, tmp.Endpoint.Address);
var miniAdminService = channelFactory.CreateChannel();
return miniAdminService.GetServiceVersionAsync().ContinueWith(t =>
{
if (t.Exception != null)
{
// The Admin Service seems to be unavailable
}
else
{
// The Admin Service is available
}
});
代码可以工作。
我的问题是-它利用IOCP调用延续?
一般来说，是否有一种方法可以知道是否通过IOCP调用延续(在调试器中，如果需要)?
注:
这是我的异步WCF方法延续的堆栈跟踪:
> *** My Code *** Line 195 C#
mscorlib.dll!System.Threading.Tasks.ContinuationTaskFromResultTask<string>.InnerInvoke() + 0x111 bytes
mscorlib.dll!System.Threading.Tasks.Task.Execute() + 0x69 bytes
mscorlib.dll!System.Threading.Tasks.Task.ExecutionContextCallback(object obj) + 0x4f bytes
mscorlib.dll!System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) + 0x28d bytes
mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) + 0x47 bytes
mscorlib.dll!System.Threading.Tasks.Task.ExecuteWithThreadLocal(ref System.Threading.Tasks.Task currentTaskSlot) + 0x3b5 bytes
mscorlib.dll!System.Threading.Tasks.Task.ExecuteEntry(bool bPreventDoubleExecution) + 0x104 bytes
mscorlib.dll!System.Threading.Tasks.Task.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem() + 0x2a bytes
mscorlib.dll!System.Threading.ThreadPoolWorkQueue.Dispatch() + 0x249 bytes
mscorlib.dll!System.Threading._ThreadPoolWaitCallback.PerformWaitCallback() + 0x1e bytes
[Native to Managed Transition]
现在，这个堆栈跟踪看起来非常类似于我从Task.Factory.StartNew调用的方法，这确实是基于线程池:
> *** My Code *** Line 35 C#
mscorlib.dll!System.Threading.Tasks.Task<int>.InnerInvoke() + 0x59 bytes
mscorlib.dll!System.Threading.Tasks.Task.Execute() + 0x60 bytes
mscorlib.dll!System.Threading.Tasks.Task.ExecutionContextCallback(object obj) + 0x37 bytes
mscorlib.dll!System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) + 0x1a2 bytes
mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) + 0x33 bytes
mscorlib.dll!System.Threading.Tasks.Task.ExecuteWithThreadLocal(ref System.Threading.Tasks.Task currentTaskSlot) + 0x2ff bytes
mscorlib.dll!System.Threading.Tasks.Task.ExecuteEntry(bool bPreventDoubleExecution) + 0xd3 bytes
mscorlib.dll!System.Threading.Tasks.Task.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem() + 0x22 bytes
mscorlib.dll!System.Threading.ThreadPoolWorkQueue.Dispatch() + 0x22e bytes
mscorlib.dll!System.Threading._ThreadPoolWaitCallback.PerformWaitCallback() + 0x18 bytes
[Native to Managed Transition]
首先，您需要添加TaskContinuationOptions.ExecuteSynchronously，以确保在异步IO操作完成的同一线程上调用continuation回调:
return miniAdminService.GetServiceVersionAsync().ContinueWith(t =>
{
if (t.Exception != null)
{
// The Admin Service seems to be unavailable
}
else
{
// The Admin Service is available
}
}, TaskContinuationOptions.ExecuteSynchronously);
显然，在。net中没有API来告诉线程是否是IOCP池线程。你只能判断线程是否为线程池线程(Thread.CurrentThread.IsThreadPoolThread)，对于IOCP线程也是true。
在Win32中，一个IOCP线程池是用CreateIoCompletionPort API创建的，但是我找不到一个Win32 API来检查线程是否属于这样的池。
所以，这里有一个有点人为的例子来检验这个理论在实践中，使用HtppClient作为测试载体。首先，我们确保所有非iocp线程都用-1填充了ThreadStatic变量s_mark。然后我们启动一个io绑定操作，并在io绑定操作完成的线程上检查s_mark:
using System;
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;
namespace ConsoleApplication_22465346
{
public class Program
{
[ThreadStatic]
static volatile int s_mark;
// Main
public static void Main(string[] args)
{
const int THREADS = 50;
// init the thread pool
ThreadPool.SetMaxThreads(
workerThreads: THREADS, completionPortThreads: THREADS);
ThreadPool.SetMinThreads(
workerThreads: THREADS, completionPortThreads: THREADS);
// populate s_max for non-IOCP threads
for (int i = 0; i < THREADS; i++)
{
ThreadPool.QueueUserWorkItem(_ =>
{
s_mark = -1;
Thread.Sleep(1000);
});
}
Thread.Sleep(2000);
// non-IOCP test
Task.Run(() =>
{
// by now all non-IOCP threads have s_mark == -1
Console.WriteLine("Task.Run, s_mark: " + s_mark);
Console.WriteLine("IsThreadPoolThread: " + Thread.CurrentThread.IsThreadPoolThread);
}).Wait();
// IOCP test
var httpClient = new HttpClient();
httpClient.GetStringAsync("http://example.com").ContinueWith(t =>
{
// all IOCP threads have s_mark == 0
Console.WriteLine("GetStringAsync.ContinueWith, s_mark: " + s_mark);
Console.WriteLine("IsThreadPoolThread: " + Thread.CurrentThread.IsThreadPoolThread);
}, TaskContinuationOptions.ExecuteSynchronously).Wait();
Console.WriteLine("Enter to exit...");
Console.ReadLine();
}
}
}
我认为这可能是足够的证据来证实iobound延续确实发生在IOCP线程上。
一本好书，相关的:斯蒂芬·克利里的《没有线索》