如何在scalaz任务中关闭AsyncHttpClient

Question

我正在尝试将AsyncHttpClient和Scalaz任务组合在一起。通常，如果我使用AsyncHttpClient，我可以调用client.close来停止客户机。

val asyncHttpClient = new AsyncHttpClient()
println(asyncHttpClient.prepareGet("http://www.google.com"))

asyncHttpClient.close()

所以电流就会停止。但是，如果我将api调用包装到任务中。我不知道怎么阻止它。

  def get(s: String) = Task.async[Int](k => {
    asyncHttpClient.prepareGet(s).execute(toHandler)
    Thread.sleep(5000)
    asyncHttpClient.closeAsynchronously()
  } )

  def toHandler[A] = new AsyncCompletionHandler[Response] {
    def onCompleted(r: Response) = {
      println("get response ", r.getResponseBody)
      r
    }
    def onError(e: Throwable) = {
      println("some error")
      e
    }
  }

println(get("http://www.google.com").run)

当前进程仍在运行。我认为原因是任务和AsynClient都是异步的。我不知道该怎么办才能关闭它

事先非常感谢

Answer 1

问题是Task.async接受一个可以注册回调的函数。这有点让人困惑，而且类型没有多大帮助，因为里面有那么多该死的Unit，但是这里的意思是，您需要更多这样的东西：

import com.ning.http.client._
import scalaz.syntax.either._
import scalaz.concurrent.Task

val asyncHttpClient = new AsyncHttpClient()

def get(s: String): Task[Response] = Task.async[Response](callback =>
  asyncHttpClient.prepareGet(s).execute(
    new AsyncCompletionHandler[Unit] {
      def onCompleted(r: Response): Unit = callback(r.right)
      def onError(e: Throwable): Unit = callback(e.left)
    }
  )
)

这并不能处理关闭客户端的问题--它只是为了展示一般的想法。您可以在处理程序中关闭客户端，但我建议如下所示：

import com.ning.http.client._
import scalaz.syntax.either._
import scalaz.concurrent.Task

def get(client: AsyncHttpClient)(s: String): Task[Response] =
  Task.async[Response](callback =>
    client.prepareGet(s).execute(
      new AsyncCompletionHandler[Unit] {
        def onCompleted(r: Response): Unit = callback(r.right)
        def onError(e: Throwable): Unit = callback(e.left)
      }
    )
  )

def initClient: Task[AsyncHttpClient] = Task(new AsyncHttpClient())
def closeClient(client: AsyncHttpClient): Task[Unit] = Task(client.close())

然后：

val res = for {
  c <- initClient
  r <- get(c)("http://www.google.com")
  _ <- closeClient(c)
} yield r

res.unsafePerformAsync(
  _.fold(
    _ => println("some error"),
    r => println("get response " + r.getResponseBody)
  )
)

这避免了closeAsynchronously (无论如何，它似乎是going away )。