使用 `ContinueWith` 时的简单注入器 "instance is requested outside the context of an active (Async Scoped) scope"

Question

我有一段代码抛出：

is registered using the 'Async Scoped' lifestyle, but the instance is requested outside the context of an active (Async Scoped) scope`

当我对 Task 使用 return 时会抛出上述问题（在较高的处理量下，但在较低的处理量下没问题）
然而，当我 await Task 时，无论直通请求量如何，它都可以正常工作，Simple Injector 不会抛出。

我很欣赏这可能更像是一个以异步为中心的问题，而不是简单的注入器，但是任何将 return 替换为 await 的见解解决了 这个问题？

提前致谢，我担心使用 await“工作”时是否可能隐藏了更大的问题。

背景：

我有以下循环，由工作人员对项目（要分派的任务）进行双端队列处理：

void Loop()
{
    while (cancellationToken.IsCancellationRequested == false)
    {
        item = await this.queue.Reader.ReadAsync(cancellationToken);
        
        await DispatchItemAsync(item, (item, dispatcher) =>
        {
            return dispatcher
                .SendAsync(((ISendItem)item).GetHandler, item.Message, item.CancellationToken)
                .ContinueWith(t => item.TaskCompletionSourceWrapper.SetResult(t.Result), TaskContinuationOptions.RunContinuationsAsynchronously);
        });
    }
}

上面循环的DispatchItemAsync如下：

protected override async Task DispatchItemAsync(
    IQueueItem item, Func<IQueueItem, IThreadStrategy, Task> dispatchFunc)
{
    // cast the passed item from channel queue
    var queueItemWithStack = item as IQueueItemWithStack;

    using (AsyncScopedLifestyle.BeginScope(this.container))
    {
        var dispatcher = container.GetInstance<InParallel>();
        // the above is an interface of delegates that is used to call functions
        
        // return throws SimpleInjector outside of scope exception (intermittent,
        // always for high request volume)
        return dispatchFunc(queueItemWithStack, dispatcher);

        // using await no exception is thrown
        // await dispatchFunc(queueItemWithStack, dispatcher);
    }
}

InParallel 包含由 dispatchFunc 行调用的函数，下面是（最终通过链）调用的：

public Task<object> SendAsync(
    Func<SendFunction> getHandler,
    object request,
    CancellationToken cancellationToken = default)
{
    return this
        .inCaller
        .SendAsync(getHandler, request, cancellationToken)
        .ContinueWith(t =>
        { 
            // snip some code
            // the below throws if DispatchItemAsync call us with return
            // but is OK if DispatchItemAsync called us with await instead
            return t.Result;
        });
}

上面ContinueWith访问t.Result时出现异常：

CommandHandler is registered using the 'Async Scoped' lifestyle, but the instance is requested outside the context of an active (Async Scoped) scope. Please see https://simpleinjector.org/scoped for more information about how apply lifestyles and manage scopes.

Answer 1

通过不等待Task，您正在执行Task 与主要操作并行 .并行意味着代码变为多线程。

这意味着原始 Scope 可能会在 Task 完成执行之前被处理掉。这会导致您遇到异常。但在其他情况下，Scope 可能会在 Task 执行期间被处理掉。这将导致对象在 Task 为运行时被处理掉。这可能会导致奇怪的 multi-threading 问题。

这意味着，在您的情况下，您应该绝对等待从 dispatchFunc.

返回的 Task

使用 `ContinueWith` 时的简单注入器 "instance is requested outside the context of an active (Async Scoped) scope"

Simple Injector "instance is requested outside the context of an active (Async Scoped) scope" when using `ContinueWith`

c#

multithreading

async-await

simple-injector