pekko/akka-remote/src/main/scala/akka/remote/AddressUidExtension.scala

/*
 * Copyright (C) 2009-2018 Lightbend Inc. <https://www.lightbend.com>
 */

package akka.remote

import java.util.concurrent.ThreadLocalRandom
import akka.actor.ActorSystem
import akka.actor.ExtendedActorSystem
import akka.actor.Extension
import akka.actor.ExtensionId
import akka.actor.ExtensionIdProvider

/**
 * Extension that holds a uid that is assigned as a random `Long` or `Int` depending
 * on which version of remoting that is used.
 *
 * The uid is intended to be used together with an [[akka.actor.Address]]
 * to be able to distinguish restarted actor system using the same host
 * and port.
 */
object AddressUidExtension extends ExtensionId[AddressUidExtension] with ExtensionIdProvider {
  override def get(system: ActorSystem): AddressUidExtension = super.get(system)

  override def lookup = AddressUidExtension

  override def createExtension(system: ExtendedActorSystem): AddressUidExtension = new AddressUidExtension(system)

}

class AddressUidExtension(val system: ExtendedActorSystem) extends Extension {

  private def arteryEnabled = system.provider.asInstanceOf[RemoteActorRefProvider].remoteSettings.Artery.Enabled

  val longAddressUid: Long = {
    val tlr = ThreadLocalRandom.current
    if (arteryEnabled) tlr.nextLong()
    // with the old remoting we need to make toInt.toLong return the same number
    // to keep wire compatibility
    else tlr.nextInt().toLong
  }

  // private because GenJavaDoc fails on deprecated annotated lazy val
  private lazy val _addressUid: Int = {
    if (arteryEnabled) {
      throw new IllegalStateException("Int UID must never be used with Artery")
    } else longAddressUid.toInt
  }

  // used by old remoting and part of public api
  @deprecated("Use longAddressUid instead", "2.4.x")
  def addressUid: Int = _addressUid
}