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异步/等待最大并发http请求数

[英]Async/Await maximum number of concurrent http requests

原文 2015-05-01 00:07:35 4 1 c#/ async-await

When Async/Await to make http requests (using HttpClient for example), is there any throttling built in by default? 当Async / Await发出http请求时（例如使用HttpClient ），默认情况下是否内置了任何限制？

Questions like this imply that an unlimited number of connections will be opened. 这样的问题这意味着连接无限数量的将被打开。 My app, which performs a batch of http requests in a loop, seems to be stay capped at around 50 TCP connections. 我的应用程序在一个循环中执行一批http请求，似乎保持在大约50个TCP连接上限。

I was initially concerned that I would need to add SemaphoreSlim for throttling, but .NET seems to doing this for me. 我最初担心我需要添加SemaphoreSlim进行限制，但.NET似乎是为我做这个。 Can anyone shed some light on this? 任何人都可以对此有所了解吗？

1 个解决方案

There are limitations on connections in the .Net framework. .Net框架中的连接存在限制。 For example this ServicePointManager has DefaultConnectionLimit That allows you to limit concurrent operations. 例如，此ServicePointManager具有DefaultConnectionLimit ，允许您限制并发操作。

However, I wouldn't recommend using it for throttling. 但是，我不建议将其用于限制。 If you need control over your requests you should use SemaphoreSlim , specifically with WaitAsync as you're in an async-await environment and these requests are IO bound (and long). 如果您需要控制您的请求，您应该使用SemaphoreSlim ，特别是WaitAsync因为您处于async-await环境中，并且这些请求是IO绑定的（并且很长）。

Using SemaphoreSlim.WaitAsync means that you don't block and you wait asynchronously which can't be the case for any other non- async throttling mechanism. 使用SemaphoreSlim.WaitAsync意味着您不会阻塞并等待异步，这对于任何其他非async限制机制都不是这种情况。 Also, you don't want to start the operation before you are able to complete it. 此外，您不希望在能够完成操作之前启动该操作。