在 Akka 中应该如何限制存储容量

Question

我正在尝试验证何时在Actor with Stash中抛出StashOverflowException。为此，我将stash-capacity设置为某个上限，如下所示：

akka.actor.deployment.default-mailbox.stash-capacity = 10

并实现了一个简单的Actor，用于存储它收到的所有消息。然后，Actor 向发送者发出信号，如果存储成功与否：

import akka.actor.{ Actor, ActorSystem, Props, Stash, StashOverflowException }
object StashExample {
  val SUCCESS        = "success"
  val FAILURE        = "failure"
  val STASH_CAPACITY = 10
}
final class StashExample extends Actor with Stash {
  import StashExample._
  var count = 0
  override def receive = {
    case _: String =>
      count += 1
      System.out.println(s"Received ${count} messages.")
      try {
        stash()
        sender ! SUCCESS
      } catch {
        case _: StashOverflowException => sender ! FAILURE
      }
  }
}

问题是，无论向该参与者发送多少条消息，都不会抛出StashOverflowException。

下面是一个尝试验证这一点的简单测试：

import akka.testkit.{ ImplicitSender, TestKit }
import org.scalatest.{ BeforeAndAfterAll, Matchers, WordSpecLike }
final class Test
    extends TestKit(ActorSystem("Test"))
    with ImplicitSender
    with WordSpecLike
    with Matchers
    with BeforeAndAfterAll {
  import StashExample._
  "stash operation" should {
    "throw overflow exception when the stash is full" in {
      val actorRef = system.actorOf(Props(new StashExample()))
      // ensure stash-capacity is configured as expected.
      system.settings.config
        .getInt("akka.actor.deployment.default-mailbox.stash-capacity") shouldBe STASH_CAPACITY
      // make the stash full.
      (0 until STASH_CAPACITY).foreach(_ => {
        actorRef ! "ping"
        expectMsg(SUCCESS)
      })
      actorRef ! "ping"
      expectMsg(FAILURE)
    }
  }
}

下面是测试失败：

Received 1 messages.
Received 2 messages.
Received 3 messages.
Received 4 messages.
Received 5 messages.
Received 6 messages.
Received 7 messages.
Received 8 messages.
Received 9 messages.
Received 10 messages.
Received 11 messages.
assertion failed: expected failure, found success
java.lang.AssertionError: assertion failed: expected failure, found success

Answer 1

删除配置键中的deployment：

akka.actor.default-mailbox.stash-capacity = 10