Migration Guide 2.0.x to 2.1.x

The 2.1 release contains several structural changes that require some simple, mechanical source-level changes in client code. Several things have been moved to Scala standard library, such as Future, and some package names have been changed in Remoting and Durable Mailboxes.

When migrating from 1.3.x to 2.1.x you should first follow the instructions for migrating 1.3.x to 2.0.x.

Scala Version

Change your project build and dependencies to Scala version 2.10.0-RC1.

Config Dependency

Typesafe config library is a normal dependency of akka-actor and it is no longer embedded in akka-actor.jar. If your are using a build tool with dependency resolution, such as sbt or maven you will not notice the difference, but if you have manually constructed classpaths you need to add config-0.5.0.jar.

Pieces Moved to Scala Standard Library

Change the following import statements.

Search	Replace with
`akka.dispatch.Await`	`scala.concurrent.Await`
`akka.dispatch.Future`	`scala.concurrent.Future`
`akka.dispatch.Promise`	`scala.concurrent.Promise`
`akka.dispatch.ExecutionContext`	`scala.concurrent.ExecutionContext`
`akka.util.Duration`	`scala.concurrent.duration.Duration`
`akka.util.duration`	`scala.concurrent.duration`
`akka.util.Deadline`	`scala.concurrent.duration.Deadline`
`akka.util.NonFatal`	`scala.util.control.NonFatal`
`akka.japi.Util.manifest`	`akka.japi.Util.classTag`

Scheduler Dispatcher

The ExecutionContext to use for running scheduled tasks must be specified.

Scala:

import context.dispatcher // Use this Actors' Dispatcher as ExecutionContext
context.system.scheduler.scheduleOnce(10 seconds, self, Reconnect)

import system.dispatcher // Use ActorSystem's default Dispatcher as ExecutionContext
system.scheduler.scheduleOnce(50 milliseconds) {
  testActor ! System.currentTimeMillis
}

Java:

// Use this Actors' Dispatcher as ExecutionContext
getContext().system().scheduler().scheduleOnce(Duration.create("10 seconds",
  getSelf(), new Reconnect(), getContext().getDispatcher());

// Use ActorSystem's default Dispatcher as ExecutionContext
system.scheduler().scheduleOnce(Duration.create(50, TimeUnit.MILLISECONDS),
  new Runnable() {
    @Override
    public void run() {
      testActor.tell(System.currentTimeMillis());
    }
  }, system.dispatcher());

API Changes of Future - Scala

v2.0:

def square(i: Int): Future[Int] = Promise successful i * i

v2.1:

def square(i: Int): Future[Int] = Future successful i * i

v2.0:

val failedFilter = future1.filter(_ % 2 == 1).recover {
  case m: MatchError => //When filter fails, it will have a MatchError
}

v2.1:

val failedFilter = future1.filter(_ % 2 == 1).recover {
  // When filter fails, it will have a java.util.NoSuchElementException
  case m: NoSuchElementException =>
}

API Changes of Future - Java

v2.0:

ExecutorService yourExecutorServiceGoesHere = Executors.newSingleThreadExecutor();
ExecutionContextExecutorService ec =
  ExecutionContexts.fromExecutorService(yourExecutorServiceGoesHere);

// Use ec with your Futures
Future<String> f1 = Futures.successful("foo", ec);

// Then you shut the ec down somewhere at the end of your application.
ec.shutdown();

v2.1:

ExecutorService yourExecutorServiceGoesHere = Executors.newSingleThreadExecutor();
ExecutionContext ec =
  ExecutionContexts.fromExecutorService(yourExecutorServiceGoesHere);

//No need to pass the ExecutionContext here
Future<String> f1 = Futures.successful("foo");

// Then you shut the ExecutorService down somewhere at the end of your application.
yourExecutorServiceGoesHere.shutdown();

v2.0:

Future<String> f1 = future(new Callable<String>() {
  public String call() {
    return "Hello" + "World";
  }
}, system.dispatcher());

v2.1:

final ExecutionContext ec = system.dispatcher();

Future<String> f1 = future(new Callable<String>() {
  public String call() {
    return "Hello" + "World";
  }
}, ec);

v2.0:

Future<String> future1 = Futures.successful("value", system.dispatcher()).andThen(
  new OnComplete<String>() {
    public void onComplete(Throwable failure, String result) {
      if (failure != null)
          sendToIssueTracker(failure);
    }
}).andThen(new OnComplete<String>() {
  public void onComplete(Throwable failure, String result) {
    if (result != null)
      sendToTheInternetz(result);
  }
});

v2.1:

final ExecutionContext ec = system.dispatcher();
Future<String> future1 = Futures.successful("value").andThen(
  new OnComplete<String>() {
    public void onComplete(Throwable failure, String result) {
        if (failure != null)
            sendToIssueTracker(failure);
    }
}, ec).andThen(new OnComplete<String>() {
  public void onComplete(Throwable failure, String result) {
    if (result != null)
      sendToTheInternetz(result);
  }
}, ec);

API changes of DynamicAccess

All methods with scala.Either[Throwable, X] have been changed to used scala.util.Try[X].

DynamicAccess.withErrorHandling has been removed since scala.util.Try now fulfills that role.

API changes of Serialization

All methods with scala.Either[Throwable, X] have been changed to used scala.util.Try[X].

Empty Props

v2.0 Scala:

val router2 = system.actorOf(Props().withRouter(
  RoundRobinRouter(routees = routees)))

v2.1 Scala:

val router2 = system.actorOf(Props.empty.withRouter(
  RoundRobinRouter(routees = routees)))

v2.0 Java:

ActorRef router2 = system.actorOf(new Props().withRouter(
  RoundRobinRouter.create(routees)));

v2.1 Java:

ActorRef router2 = system.actorOf(Props.empty().withRouter(
  RoundRobinRouter.create(routees)));

Props: Function-based creation

v2.0 Scala:

Props(context => { case someMessage => context.sender ! someMessage })

v2.1 Scala:

Props(new Actor { def receive = { case someMessage => sender ! someMessage } })

Failing Send

When failing to send to a remote actor or actor with bounded or durable mailbox the message will silently be delivered to ActorSystem.deadletters instead of throwing an exception.

Graceful Stop Exception

If the target actor of akka.pattern.gracefulStop isn't terminated within the timeout the Future is completed with failure akka.pattern.AskTimeoutException. In 2.0 it was akka.actor.ActorTimeoutException.

getInstance for Singletons - Java

v2.0:

import static akka.actor.Actors.*;

if (msg.equals("done")) {
  myActor.tell(poisonPill());
} else if (msg == Actors.receiveTimeout()) {

v2.1:

import akka.actor.PoisonPill;
import akka.actor.ReceiveTimeout;

if (msg.equals("done")) {
  myActor.tell(PoisonPill.getInstance());
} else if (msg == ReceiveTimeout.getInstance()) {

Testkit Probe Reply

v2.0:

probe.sender ! "world"

v2.1:

probe.reply("world")

log-remote-lifecycle-events

Default value of akka.remote.log-remote-lifecycle-events has changed to on. If you don't want these in the log you need to add this to your configuration:

akka.remote.log-remote-lifecycle-events = off

Stash postStop

Both Actors and UntypedActors using Stash now overrides postStop to make sure that stashed messages are put into the dead letters when the actor stops, make sure you call super.postStop if you override it.

Forward of Terminated message

Forward of Terminated message is no longer supported. Instead, if you forward Terminated you should send the information in you own message.

v2.0:

context.watch(subject)

def receive = {
  case t @ Terminated => someone forward t
}

v2.1:

case class MyTerminated(subject: ActorRef)

context.watch(subject)

def receive = {
  case Terminated(s) => someone forward MyTerminated(s)
}

Custom Router or Resizer

The API of RouterConfig, RouteeProvider and Resizer has been cleaned up. If you use these to build your own router functionality the compiler will tell you you to do some adjustments.

v2.0:

class MyRouter(target: ActorRef) extends RouterConfig {
  override def createRoute(p: Props, prov: RouteeProvider): Route = {
    prov.createAndRegisterRoutees(p, 1, Nil)

v2.1:

class MyRouter(target: ActorRef) extends RouterConfig {
  override def createRoute(provider: RouteeProvider): Route = {
    provider.createRoutees(1)

v2.0:

def resize(props: Props, routeeProvider: RouteeProvider): Unit = {
  val currentRoutees = routeeProvider.routees
  val requestedCapacity = capacity(currentRoutees)

  if (requestedCapacity > 0) {
    val newRoutees = routeeProvider.createRoutees(props, requestedCapacity, Nil)
    routeeProvider.registerRoutees(newRoutees)
  } else if (requestedCapacity < 0) {
    val (keep, abandon) = currentRoutees.splitAt(currentRoutees.length +
      requestedCapacity)
    routeeProvider.unregisterRoutees(abandon)
    delayedStop(routeeProvider.context.system.scheduler, abandon)(
      routeeProvider.context.dispatcher)
  }

v2.1:

def resize(routeeProvider: RouteeProvider): Unit = {
  val currentRoutees = routeeProvider.routees
  val requestedCapacity = capacity(currentRoutees)

  if (requestedCapacity > 0) routeeProvider.createRoutees(requestedCapacity)
  else if (requestedCapacity < 0) routeeProvider.removeRoutees(
    -requestedCapacity, stopDelay)

Duration and Timeout

The Duration class in the scala library is an improved version of the previous akka.util.Duration. Among others it keeps the static type of FiniteDuration more consistently, which has been used to tighten APIs. The advantage is that instead of runtime exceptions you’ll get compiler errors telling you if you try to pass a possibly non-finite duration where it does not belong.

The main source incompatibility is that you may have to change the declared type of fields from Duration to FiniteDuration (factory methods already return the more precise type wherever possible).

Another change is that Duration.parse was not accepted by the scala-library maintainers, use Duration.create instead.

v2.0:

final Duration d = Duration.parse("1 second");
final Timeout t = new Timeout(d);

v2.1:

final FiniteDuration d = Duration.create("1 second");
final Timeout t = new Timeout(d); // always required finite duration, now enforced

Package Name Changes in Remoting

The package name of all classes in the akka-remote.jar artifact now starts with akka.remote. This has been done to enable OSGi bundles that don't have conflicting package names.

Change the following import statements. Please note that the serializers are often referenced from configuration.

Search	Replace with
`akka.routing.RemoteRouterConfig`	`akka.remote.routing.RemoteRouterConfig`
`akka.serialization.ProtobufSerializer`	`akka.remote.serialization.ProtobufSerializer`
`akka.serialization.DaemonMsgCreateSerializer`	`akka.remote.serialization.DaemonMsgCreateSerializer`

Package Name Changes in Durable Mailboxes

The package name of all classes in the akka-file-mailbox.jar artifact now starts with akka.actor.mailbox.filebased. This has been done to enable OSGi bundles that don't have conflicting package names.

Change the following import statements. Please note that the FileBasedMailboxType is often referenced from configuration.

Search	Replace with
`akka.actor.mailbox.FileBasedMailboxType`	`akka.actor.mailbox.filebased.FileBasedMailboxType`
`akka.actor.mailbox.FileBasedMailboxSettings`	`akka.actor.mailbox.filebased.FileBasedMailboxSettings`
`akka.actor.mailbox.FileBasedMessageQueue`	`akka.actor.mailbox.filebased.FileBasedMessageQueue`
`akka.actor.mailbox.filequeue.*`	`akka.actor.mailbox.filebased.filequeue.*`

Actor Receive Timeout

The API for setting and querying the receive timeout has been made more consisten in always taking and returning a Duration, the wrapping in Option has been removed.

(Samples for Java, Scala sources are affected in exactly the same way.)

v2.0:

getContext().setReceiveTimeout(Duration.create(10, SECONDS));
final Option<Duration> timeout = getContext().receiveTimeout();
final isSet = timeout.isDefined();
resetReceiveTimeout();

v2.1:

getContext().setReceiveTimeout(Duration.create(10, SECONDS));
final Duration timeout = getContext().receiveTimeout();
final isSet = timeout.isFinite();
getContext().setReceiveTimeout(Duration.Undefined());

ConsistentHash

akka.routing.ConsistentHash has been changed to an immutable data structure.

v2.0:

val consistentHash = new ConsistentHash(Seq(a1, a2, a3), replicas = 10)
consistentHash += a4
val a = consistentHash.nodeFor(data)

v2.1:

var consistentHash = ConsistentHash(Seq(a1, a2, a3), replicas = 10)
consistentHash = consistentHash :+ a4
val a = consistentHash.nodeFor(data)

Contents

Migration Guide 2.0.x to 2.1.x

Scala Version

Config Dependency

Pieces Moved to Scala Standard Library

Scheduler Dispatcher

API Changes of Future - Scala

API Changes of Future - Java

API changes of DynamicAccess

API changes of Serialization

Empty Props

Props: Function-based creation

Failing Send

Graceful Stop Exception

getInstance for Singletons - Java

Testkit Probe Reply

log-remote-lifecycle-events

Stash postStop

Forward of Terminated message

Custom Router or Resizer

Duration and Timeout

Package Name Changes in Remoting

Package Name Changes in Durable Mailboxes

Actor Receive Timeout

ConsistentHash

Akka

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