Volatile IEnlistmentNotification and TransactionScope.AsyncF

本文关键字：AsyncF TransactionScope and IEnlistmentNotification Volatile | 更新日期: 2023-09-27 18:32:55

除了.NET 4.5.1之外，TransactionScope上还有一个新选项，可以使用异步流。这允许编写以下客户端代码

using(var txt = new TransactionScope(..., TransactionScopeAsyncFlowOption.Enabled)
{
   await sender.SendAsync();
}

目前为止，一切都好。但是当我需要实现一个易失性的IEnlistmentNotice时，我正在努力做到这一点。让我们想象一下以下场景，假设：我的底层基础架构从下到上完全异步

public class MessageSender : ISendMessages
{
    public async Task SendAsync(TransportMessage message, SendOptions options)
    {
        await sender.SendAsync(message);
    }
}

因此，我想要实现的是引入一个易失性的IEnlistmentNotification，如下所示：

internal class SendResourceManager : IEnlistmentNotification
{
    private readonly Func<Task> onCommit;
    public SendResourceManager(Func<Task> onCommit)
    {
        this.onCommit = onCommit;
    }
    public void Prepare(PreparingEnlistment preparingEnlistment)
    {
        preparingEnlistment.Prepared();
    }
    public void Commit(Enlistment enlistment)
    {
        await this.onCommit();
        enlistment.Done();
    }
    public void Rollback(Enlistment enlistment)
    {
        enlistment.Done();
    }
    public void InDoubt(Enlistment enlistment)
    {
        enlistment.Done();
    }
}

和新发件人

public class MessageSender : ISendMessages
{
    public async Task SendAsync(TransportMessage message, SendOptions options)
    {
        // Dirty: Let's assume Transaction.Current is never null
        Transaction.Current.EnlistVolatile(new SendResourceManager(async () => { await sender.SendAsync(message) }));
    }
}

注意：当然，此代码无法编译。这将要求我声明提交方法异步无效。这是令人敬畏的。

所以我的问题是：如何编写可以在内部等待异步操作的登记？

Volatile IEnlistmentNotification and TransactionScope.AsyncF

只要EnlistVolatile不是繁重的 CPU 密集型耗时操作，您就可以使用 Task.FromResult 在 EnlistVolatile 上创建一个基于 Task 的瘦包装器：

public static class TranscationExtensions
{
    public static Task EnlistVolatileAsync(this Transaction transaction, 
                                           IEnlistmentNotification 
                                           enlistmentNotification, 
                                           EnlistmentOptions enlistmentOptions)
    {
        return Task.FromResult(transaction.EnlistVolatile
                                           (enlistmentNotification, 
                                            enlistmentOptions));
    }
}

然后在您的方法中使用它：

public class MessageSender : ISendMessages
{
    public Task SendAsync(TransportMessage message, SendOptions options)
    {
        return Transaction.Current.EnlistVolatileAsync
               (new SendResourceManager(async () => 
                                       { await sender.SendAsync(message) }));
    }
}

可以在调用堆栈中等待更高的位置：

MessageSender sender = new MessageSender();
await sender.SendAsync(message, options);
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