玩流畅和异步 - 这是竞争条件吗?

问题描述

阅读Play-Slick DBAction 代码，我认为此代码可能包含竞争条件:

Reading Play-Slick DBAction code, I thought that this code might contain a race condition:

object DBAction{
  // snip

  def apply(r: (RequestWithDbSession) => Result)(implicit app:Application) = {
    Action { implicit request =>
      AsyncResult {
        DB.withSession{ s:scala.slick.session.Session =>
          Future(r( RequestWithDbSession(request,s) ))(executionContext)
      }
    }
  }
}

函数 r 在未来时间运行，在 withSession 返回一个 Future[Result] 之后，并调用 session.close().这段代码中是否存在竞争条件?

The function r runs at a future time, after withSession has returned a Future[Result], and called session.close(). Is there a race condition in this code?

推荐答案

我不确定这是否称为竞争条件.但是在我看来，您认为这里出了点问题是正确的.将来执行代码时，会话可能不再有效.

I am not sure if that is called a race condition. However to me it seems that you are correct that something is wrong here. The session might no longer be valid when the future executes the code.

最好在将来反转执行并请求数据库会话:

It would be better to invert the execution and request a database session from within the future:

Async {
  Future {
    DB.withSession{ s:scala.slick.session.Session =>
      r( RequestWithDbSession(request, s) )
    }
  }
}

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