什么是异步Web服务的好处时，没有代码的所有部分是异步 [英] What are the benefits of async webservices when not all parts of the code is async

问题描述

我想知道你使用异步HTTP请求，如果不是你的代码的所有部分是异步多少好处获得

I am wondering how much benefit you get from using async http requests if not all parts of your code is async.

让我们考虑到的情况：1）异步HTTP请求阻塞同步数据库调用，以及2）同步HTTP请求等待异步调用数据库。

Lets consider to scenarios: 1) async http requests blocking on sync database calls, and 2) sync http requests awaiting async database calls.

1）的Web API支持异步操作的方法，但如果我做一个同步数据库调用处理请求时，然后在调用的线程块，我不会得到更好的线程经济的异步能给我还是什么好处？

1) Web Api supports async action methods, but if I do a sync database call when handling the request, then the thread blocks on the call, and I will not get the benefits of better thread economy that async could give me or what?

2）如果我有一个同步ServiceStack服务呼叫等待着一个异步数据库调用，那么会发生什么？我假定一个线程被保留用于处理整个同步http请求，并且当该线程等待一个异步呼叫则它仍保留给web请求或什么？

2) If I have a synchronous ServiceStack service call that awaits an async database call, then what happens? I assume a thread is reserved for handling the entire sync http request, and when this thread awaits an async call then it is still reserved to the web request or what ?

Basicallly我的问题可以归结为：是否有任何理由使用异步如果不是所有的IO调用都是异步

Basicallly my question can be boiled down to this: Is there any reason to use async if not all IO calls are async?

推荐答案

在服务器端，有一个部分通常是没有任何好处。 - 异步解决方案

On the server side, there is usually no benefit in a partially-async solution.

1）的Web API支持异步操作的方法，但如果我做一个同步数据库调用处理请求时，则在电话会议上的线程块，我就没有得到更好的线程经济的异步能给我还是什么好处？

1) Web Api supports async action methods, but if I do a sync database call when handling the request, then the thread blocks on the call, and I will not get the benefits of better thread economy that async could give me or what?

正确的。只要你做一个同步（阻塞）数据库调用，你占用一个线程该呼叫的持续时间。所以，你会从得到异步的好处不适用。

Correct. As soon as you do a synchronous (blocking) database call, you are tying up a thread for the duration of that call. So the benefits that you would have gotten from async do not apply.

2 ）如果我有一个同步ServiceStack服务呼叫等待着一个异步数据库调用，那么会发生什么？我假设一个线程被保留用于处理整个同步http请求，而当这个线程等待一个异步调用，然后它仍然保留web请求还是什么？

2) If I have a synchronous ServiceStack service call that awaits an async database call, then what happens? I assume a thread is reserved for handling the entire sync http request, and when this thread awaits an async call then it is still reserved to the web request or what ?

这仅仅是一样的同步数据库调用。在幕后，同步数据库调用异步执行，然后实际调用块调用线程，直到它完成。所以，你仍然有阻塞呼叫的持续时间线程，你没有得到任何异步收益。

This is just the same as a synchronous database call. Under the covers, a synchronous database call executes the actual call asynchronously and then blocks the calling thread until it completes. So you still have a thread blocked for the duration of the call, and you don't get any async benefits.

Basicallly我的问题可以归结为：是否有任何理由使用异步如果不是所有的IO调用都是异步

Basicallly my question can be boiled down to this: Is there any reason to use async if not all IO calls are async?

有一些比较模糊的场景。您可以使用 Task.WhenAll 做了有限型并发，这与比其他形式的更容易异步异步并发。但是，这是我能想到的，如果你没有一个完全的唯一的好处 - 异步栈

There are a few more obscure scenarios. You can use Task.WhenAll to do a limited type of concurrency, which is much easier with async than other forms of asynchronous concurrency. But that's the only benefit I can think of if you don't have a fully-async stack.

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