akka：共享可变状态

发布于 2024-12-03 06:13:11 字数 580 浏览 1 评论 0原文

我需要有一个很少改变的全局变量（单例）。实际上它只会在 actor 重新启动并重新初始化变量时发生变化。由于我无法在伴生对象中使用 singleton val 来执行此操作，因此我必须将其声明为 var （可变）。

object UserDatabase {
    var dbConnection = "" // initializing db connection
}

我读到的许多指南总是反对共享可变状态。因此，我将变量移至类并使用消息传递来检索变量。

class UserDatabase extends Actor{
    val dbConnection = "" // initializing db connection locally
    def receive = {case GetConnection => self.reply(dbConnection)}
}

问题是，dbConnection 被许多..许多参与者非常频繁地访问，并且连续发送消息会降低性能（因为 akka 会一一处理邮箱）。

我不知道如何在不牺牲性能的情况下做到这一点。有什么想法吗？

原文

I need to have one global variable (singleton) that will change very infrequently. Actually it only changes when the actor restarts, and reinitialize the variable. Since I cannot do this with singleton val in companion object, I have to declare it as a var (mutable).

object UserDatabase {
    var dbConnection = "" // initializing db connection
}

Many guidelines that I read always go against sharing a mutable state. So I move the variable to class and use message passing to retrieve the variable.

class UserDatabase extends Actor{
    val dbConnection = "" // initializing db connection locally
    def receive = {case GetConnection => self.reply(dbConnection)}
}

Problem is, dbConnection is accessed very frequently by many .. many actors, and continuously sending message will reduce performance (since akka process mailbox one by one).

I don't see how I can do this without sacrificing performance. Any idea?

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天气好吗我好吗 2024-12-10 06:13:11

也许改用代理？ http://akka.io/docs/akka/1.2-RC6/scala /agents.html

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深海夜未眠 2024-12-10 06:13:11

首先，您是否真正测量/注意到性能下降？由于消息传递是轻量级的，因此对于您的应用程序来说可能足够快。

那么，一个可能的解决方案是：如果“全局”状态很少写入，但访问很频繁，则可以选择推送策略。每次更改时，UserDatabase actor 都会将更新后的值发送给感兴趣的 actor。然后，您可以使用发布/订阅方法、依赖参与者注册、使用参与者池等。

class UserDatabase extends Actor{
    var dbConnection = "" // initializing db connection locally
    def receive = {
      case SetConnection( newConnection ) if dbConnection != newConnection => {
        dbConnection = newConnection
        sendUpdatedConnection(); // sends the change to every relevant actor
      }
    }
}

First of all, have you actually measure/notice performance reduction ? Since messaging is lightweight, perhaps it's fast enough for your application.

Then, a possible solution: If the "global" state is written rarely, but accessed very often, you can choose a push strategy. Every time it changes, the UserDatabase actor will send the updated value to interested actors. You can then use a publish/subscribe approach, rely on the actor register, use a pool of actors, etc.

class UserDatabase extends Actor{
    var dbConnection = "" // initializing db connection locally
    def receive = {
      case SetConnection( newConnection ) if dbConnection != newConnection => {
        dbConnection = newConnection
        sendUpdatedConnection(); // sends the change to every relevant actor
      }
    }
}

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