阻止Akka Actors中的呼叫 [英] Blocking calls in Akka Actors

问题描述

作为一个新手，我想了解演员如何工作。并且，从文档，我想我明白，演员是在同步模式下执行的对象，并且actor执行可以包含阻塞/同步方法调用，例如。 db请求

As a newbie, I am trying to understand how actors work. And, from the documentation, I think I understand that actors are objects which gets executed in sync mode and also that actor execution can contain blocking/sync method calls, e.g. db requests

但是，我不明白的是，如果你写一个在其中有一些阻塞调用（如阻塞查询执行）的actor，整个线程池（在某种意义上cpu的利用率会下降等等），对吧？我的意思是，从我的理解，没有办法JVM理解是否可以切换到别人，如果/当演员进行阻塞调用时。

But, what I don't understand is that if you write an actor that has some blocking invocations inside (like a blocking query execution), it will mess up the whole thread pool (in the sense that cpu utilization will go down, etc.), right ? I mean, from my understanding, there is no way for JVM to understand whether it can switch that thread to someone else, if/when the actor makes a blocking call.

所以，考虑到并发的性质，应该不是很明显，演员不应该做任何阻塞调用，永远？

So, given the nature of concurrency, shouldn't it be obvious that Actors should not be doing any blocking calls, ever?

如果是这种情况，建议使用非阻塞/异步调用的方法，假设一个Web服务调用获取一些东西并发送消息另一个actor何时该请求完成？我们应该简单地使用像actor中的东西：

If that is the case, what is the recommended way of doing a non-blocking/async call, let's say a web service call that fetches something and sends a message to another actor when that request is completed? Should we simply use something like within the actor:

future map {response => x！ response.body}

future map { response => x ! response.body }

这是正确的处理方式吗？

Is this the proper way of handling this?

这对我来说。

推荐答案

这真的取决于用例。如果查询不需要序列化，那么您可以以后执行查询并将结果发送回发件人，如下所示：

It really depends on the use-case. If the queries do not need to be serialized, then you can execute the query in a future and send the results back to the sender as follows:

import scala.concurrent.{ future, blocking}
import akka.pattern.pipe

val resFut = future {
  blocking {
    executeQuery()
  }
}

resFut pipeTo sender

您还可以为DB调用专门创建专用分派器，并使用路由器创建actor。这样，您也可以轻松地限制并发数据库请求的数量。

You could also create a dedicated dispatcher exclusively for the DB calls and use a router for actor creation. This way you can also easily limit the number of concurrent DB requests.

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