akka-js / akka.js Goto Github PK

Hi, when you write a communication mechanism that allows WebWorkers to talk to each other, watch out for communication that would require opaque objects to be transferred. I can't use the scalajs-rx-idb library because it uses lihaoi's upickle which transforms everything to a string . See l15k4/scalajs-rx-idb#3

Implement timeout in akka.concurrent.Await

We must follow Akka ones where presents and do not diverge from the original signatures as highlighted in #43

Do you have a gitter channel to discuss things?

AKKA-ACTOR

• actor/
• dispatch/
• event/
• pattern/
• routing/
• serialization/
• util/

TODO

• allow ovewriting of context by rewriting IR in ActorCell.scala
• remove dependencies from akka.util.JS*
• Strategies are mostly missing
• add support for Workers + routing in ActorPath (partial, will be refactored in akka-remote)
• IMPORTANT refactor out Java API, maybe with a mixin? We could share this approach with JS (see #6) and provide Java || JS api if we're calling from Scala or Scala.js
• port typesafe.config.Config (it's 100% Java, so we can't cross-compile. alternatives? see @mfirry 's suggestion in #5 )
• sun.misc.Unsafe (stub implementation vs mixin with traits JS/JVM specific methods?)
• JVM data structures (see #8)

DONE

• move JSMap to TreeMap
• some System.getEnv and System.getProperty calls to remove (eg: ActorSystem.scala)
• mailboxTypes are missing
• refactor out references to Thread (eg: Thread.currentThread().interrupt())
• implement event/ (and therefore Logging)
• clean up setActorFields in Actor.scala
• remove Java imports
• remove Java (ThreadLocal, etc) from ActorCell.scala and add lookupAndSetField
• MalformedUrlException in ActorPath
• Deployer doesn't exist yet
• ActorFor in ActorRefProvider.scala
• Implement constructor for Props
• some code depends on DynamicAccess, it needs to be refactored out
• terminationCallbacks in ActorSystem
• fix override def in the EventLoopScheduler (they override final methods, had to fix by hand)
• dispatch/AbstractDispatcher.scala contains some thread-specific logic, refactor it out?

AKKA-REMOTE

Currently blocked by:

• Lack of a pickling library capable of serializing Any (scala pickling should help solve the issue: @phaller @heathermiller )
• Reflection in Scala.js (partial support being discussed here)

Hi,
is this library could be used in node.js and programming be done using JavaScript or TypeScript instead of scala.js?
As I imagine it would be possible to do require('akka.js') and use its facilities.
I've downloaded a latest release, but cannot find any file like "akka.js"
Would be possible to export this library to npm package?

There are a few constructs in akka http that are quite high level and don't depend on a lot of the streaming stuff such as the Akka.http.model.Uri which I ported a year ago and all of the header parsing code. Those I think could already be very useful for everyday scala.js http development.

Like we did for Logs we need to realize if this is feasible or have an acceptable alternative that can be pushed back to akka master

call stack size exceeded

[error] TypeError: Cannot read property 'prototype' of undefined
[error]   at $newJSObjectWithVarargs([stdin]:497:45)
[error]   at akka.actor.JsReflectable$class.instantiate([stdin]:2191:15)
[error]   at akka.actor.NoArgsReflectConstructor.produce([stdin]:34630:32)
[error]   at akka.actor.ActorCell.newActor([stdin]:73305:77)
[error]   at akka.actor.ActorCell.create([stdin]:73243:24)
[error]   at akka.actor.ActorCell.invokeAll$1([stdin]:73439:18)
[error]   at akka.actor.ActorCell.systemInvoke([stdin]:73197:8)
[error]   at akka.dispatch.Mailbox.processAllSystemMessages([stdin]:35141:18)
[error]   at akka.dispatch.Mailbox.run([stdin]:35091:12)
[error]   at {anonymous}()([stdin]:34967:19)

It cannot instantiate because it is a nested class (@JSExport doesn't work)

Has the project considered support networking features through Node with https://github.com/scalajs-io/scalajs.io?

Avoid the commits of generated files and reproduce akka build chain to use sbt-boilerplate directly.

Some data structures, which are heavily used in Akka, are currently missing in Akka.js/Scala.js
Most notably:

TODO

• java.util.TreeSet
• java.util.Locale
  (https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/BlockingQueue.html)

DONE

• java.util.ConcurrentHashMap
• java.util.ConcurrentSkipListSet
• akka.util.Index (mutable.HashMap with mutable.MultiMap is enough for this, we need a generic Index to be implemented in JS/JVM code)
• java.net.MalformedUrlException
• java.util.AbstractQueue
• java.util.Queue
• java.util.LinkedList
• java.util.concurrent.atomic.AtomicArrayReference
• java.util.concurrent.CopyOnWriteArrayList
• java.util.concurrent.ConcurrentLinkedQueue
• java.util.PriorityQueue
• java.util.Deque

To allow for 100% Java interoperability we should also implement the DS' supertypes, but it's a pretty big task, maybe we could just do with the basic methods for now?

Akka.JVM uses (I'm assuming for performance reasons) some JVM data structures, which are not available in Scala-js (eg: Deque)

Akka currently only uses a small subset of methods from each class.

There are two ways we can fix this: either we completely port the required data structures to Scala-js OR we can do something like this:

in jvm/src/main/akka/util/

class AkkaDeque[A] extends Deque[V] {
  def methodWeNeed = threadLocalMethod()
}

in js/src/main/akka/util/

class AkkaDeque[A] {
  var value: A = _
  def methodWeNeed = ???
}

On one hand, solution 1 requires a lot of effort on the Scala-js side, but it doesn't require any changes to Akka itself.

On the other hand, solution 2 would require some changes and it might be a bit more clumsy in case you need new methods from the underlying collection (you need to manually add the method to AkkaDeque), but it doesn't require nearly as much effort on the Scala-js side

Thoughts?

@rkuhn @andreaTP @andreaferretti

When I try to run my Scala.js tests (that work with Akka on the JVM) I'm getting the following at fast opt:

[error] Referring to non-existent method scala.concurrent.impl.Promise$CompletionLatch.releaseShared(scala.Int)scala.Boolean
[error]   called from scala.concurrent.impl.Promise$CompletionLatch.apply(scala.util.Try)scala.Unit
[error]   called from scala.concurrent.impl.Promise$CompletionLatch.apply(java.lang.Object)java.lang.Object
[error]   called from scala.Function1.apply$mcVD$sp(scala.Double)scala.Unit
[error]   called from scala.collection.AbstractSeq.apply$mcVD$sp(scala.Double)scala.Unit

Is there something I'm doing wrong or is this a missing feature?

Minor issue.

In the common settings the use of EclipseKeys means that sbt won't run on my system. I suppose one has to import them somewhere else. I use IntelliJ.

Removing the two lines gets it to work

--- a/build.sbt
+++ b/build.sbt
@@ -1,6 +1,6 @@
 val commonSettings = Seq(
-    EclipseKeys.useProjectId := true,
-    EclipseKeys.skipParents in ThisBuild := false,
+//    EclipseKeys.useProjectId := true,
+//    EclipseKeys.skipParents in ThisBuild := false,

Common Issues

1. There are many test classes where some tests pass but yet are excluded , indeed some test classes are excluded because of one failure. If we can find a means to non-invasively exclude (mark as pending or provide a tag) just those tests that fail, the number of passing tests in actor-tests would increase from just under 100 to over 400. We would continue to benefit from this as we fix more tests.
2. The manner in which the Await link issue was fixed has given rise to other issues.

• An call to a method in Await occurring transitively may be bound the non existing version resulting in a link error such as in ActorDSLSpec calling an Inbox method with calls receive.
• Placing Await in akka.event causes link error for all specs similar to the below
  '''link Referring to non-existent method akka.event.Await$.result(scala.Function0,scala.concurrent.duration.Duration)java.lang.Object
  [error] called from akka.event.LoggingBus.addLogger(akka.actor.ActorSystemImpl,java.lang.Class,scala.Int,java.lang.String)akka.actor.ActorRef
  [error] called from akka.event.EventStream.addLogger(akka.actor.ActorSystemImpl,java.lang.Class,scala.Int,java.lang.String)akka.actor.ActorRef
  [error] called from akka.event.LoggingBus.$$anonfun$startDefaultLoggers$4(akka.actor.ActorSystemImpl,java.lang.String,scala.Int,java.lang.Class)akka.actor.ActorRef
  [error] called from akka.event.EventStream.$$anonfun$startDefaultLoggers$4(akka.actor.ActorSystemImpl,java.lang.String,scala.Int,java.lang.Class)akka.actor.ActorRef
  [error] called from akka.event.LoggingBus.$$anonfun$startDefaultLoggers$3(akka.actor.ActorSystemImpl,java.lang.String,scala.Int,java.lang.String)akka.actor.ActorRef
  [error] called from akka.event.EventStream.$$anonfun$startDefaultLoggers$3(akka.actor.ActorSystemImpl,java.lang.String,scala.Int,java.lang.String)akka.actor.ActorRef
  [error] called from akka.event.LoggingBus.startDefaultLoggers(akka.actor.ActorSystemImpl)scala.Unit
  [error] called from akka.event.EventStream.startDefaultLoggers(akka.actor.ActorSystemImpl)scala.Unit
  [error] called from akka.event.EventStreamSpec.$$anonfun$new$10()scala.Unit’’’

3. The manner in which the Thread.sleep link issue was fixed leaves the following unresolved..

• Other methods in thread not implemented such as current, interrupted
• The implicit ActorSystem parameter is not available in test suites which do not extend AkkaSpec e.g Bench.scala

4. Props[Typename]Does not work when the class is in a module (must be top level) must rewrite to Props[new Typename(…)]```

5. Typesafe Config

• No arg defaultReference() not available
• com.typesafe.config.ConfigParseOptions
• com.typesafe.config.ConfigException
• ConfigFactory.parseMap signature needs change
• found java.util.Map[String,Boolean]
  required: java.util.Map[String,Any]

6. Bounded mailbox impl classes

• BoundedControlAwareMessageQueueSemantics
• BoundedMailbox.MessageQueue
• BoundedMessageQueueSemantics
• BoundedDequeBasedMailbox

7. Java classes

• org.scalatest.junit.JUnitSuiteLike

8. java.time.LocalDateTime

• Must refer to akka.testkit.CountdownLatch

9. Akka metrics not ported

• akka.testkit.metrics
• com.codahale.metrics.{ Histogram }
• MetricsKit

10. Java collections

• java.util.concurrent.ConcurrentLinkedQueue
• LinkedBlockingQueue

11. Priority Mailbox

• UnboundedPriorityMailbox
• BoundedPriorityMailboxStablePriorityDispatcherSpec
• UnboundedStablePriorityMailbox
• BoundedStablePriorityMailbox

12. Config file reader has errors reading embedded strings. See examples

• akka.routing.ConfiguredLocalRoutingSpec
• akka.routing.ResizerSpec
• akka.routing.RoutingSpec
• akka.routing.ConsistentHashingRouterSpec

13. Test Failure in akka.actor.dispatch.DispatcherActorsSpec

• Dispatcher apparently drains one actor queue then the other
  there is no concurrency.

14. scala.compat.java8.FutureConverters link error

Specific Actor Test Issues

akka

1. AkkaExceptionSpec

• link error AkkaExceptionSpec.verify clazz.getConstructor(Array(classOf[String]): _*)
  actor.actor

2. ActorRefSpec

• Java NonPublicClass.createProps must be rewritten from Props.create(MyNonPublicActorClass.class)
  to Props.create(classOf[MyNonPublicActorClass])

3. FMSActorSpec

• Logging imported twice in the same scope must be imported specifically

4. PropsCreatorSpec

• Java API OneParamActorCreator needed

5. ConsistencySpec

• import akka.dispatch.{ ThreadPoolConfig }

6. SchedulerSpec

• akka.actor.LightArrayRevolverScheduler.TickDuration

akka.actor.dispatch
7. ExecutionContextSpec.scala

• akka.util.SerializedSuspendableExecutionContext

akka.pattern
8. PatternSpec

• FutureTimeoutSupport

9. CircuitBreakerMTSpec

• overloaded method value onHalfOpen with alternatives:
  (callback: Runnable)akka.pattern.CircuitBreaker
  (callback: => Unit)akka.pattern.CircuitBreaker
  cannot be applied to (Any)
  breaker.onHalfOpen(halfOpenLatch.countDown())

10. CircuitBreakerSpec

• overloaded method value onClose with alternatives:
  akka.pattern.CircuitBreaker
  (callback: => Unit)akka.pattern.CircuitBreaker
  cannot be applied to (Any) instance.onClose(closedLatch.countDown()).onHalfOpen(halfOpenLatch.countDown()).onOpen(openLatch.countDown())

akka.routing
11. BalancingSpec

• classes in actor unimplemented, BalancingPool->BalancingDispatcherConfigurator->ThreadFactory
  akka.util

12. ByteStringSpec

• org.apache.commons.codec.binary.Hex.encodeHex

13. LineNumberSpec

• LineNumberSpecCodeForJava

akka.event
14. AddressTerminatedTopicBenchSpec

• Large number of actors 20,0000 cause runtime errors

15. EventStreamSpec

• Logger specified in config can't be loaded [akka.event.EventStreamSpec$MyLog] due to [java.util.NoSuchElementException: key not found: akka.event.EventStreamSpec$MyLog]

Specific Stream Test Issues

akka.stream.impl

1. StreamLayoutSpec

• deep recursion val tooDeepForStack = 50000

akka.stream
2. akka.stream.scaladsl.SubstreamSubscriptionTimeoutSpec

• Issue extending with StreamSpec(conf)

Right now we do not have a check of uniqueness of extensions.
This could be done with a WeakMap[ActorSystem, HashMap[ExtensionName, ExtensionInstance]]

just TBD

For discussion:

the project reactive-stream-scalajs provides only few interfaces to be implemented.
Since here they say there are problems publishing the project I think we can simply include the related sources into the akka-stream-js project without having it as a dependency.

This will be an hook for future reference on decisions taken about the reliable reuse of Akka sources.

We have different kind of problems and we get to face them differently:

1- Semantic differences:
if in a file there are implementations that do not conform to js-vm semantics we will split implementations and interfaces in different files, use just the interfaces and PR the modification to upstream Akka.

2- Java API:
Since it is hard-wired into interfaces it will be dropped at compile time via a compiler plugin (basically we remove the related AST based on configuration files)

3- Scala.Js needed annotations:
We will apply them between typer and jsinterop using a compiler plugin

4- Inner class substitutions:
In order to save the huge amount of code on some singletons(i.e. ActorSystem) we will replace inner classes after the parser based on a config file.

5- context reflection workaround:
Actor context field is subject to reflection hacking to keep developer Api clean, the bheaviour could be replicated manipulating the IR (as suggested by @sjrd https://github.com/sjrd/scala-js-example-app/tree/hack-set-val)

Hope this will cover 100% of the use cases.

Ideas or suggestions that will simplify this huge work are very much welcome!

right now assembleAkkaLibrary is entirely defined every time.
We need to factor it out to keep it easier to use and debug in case.

Though I will not expect running a HTTP server on Scala.js, some data structures from akka-http like Path and Uri are useful in Scala.js .

Another usage of akka-http.js is creating an in-memory mock server to handler fake HTTP requests (for testing purpose).

Actor.cell

I'm getting an error just starting up an ActorSystem.
Referring to non-existant method java.text.SimpleDateFormat.format(java.util.Date)
called from akka.event.Logging...timestamp(...)
Using scalajs 0.6.14 and akkajs 0.2.4.16

Most of the code can be shared between Akka.JVM and Akka.js so my proposal is, for akka-actor, to adopt the standard layout of cross-compilable Scala-js modules which is the following

• one shared/ directory with shared code
• one js/ directory with JS specific implementations
• one jvm/ directory with JVM specific implementations

@rkuhn @andreaTP @andreaferretti

in ActorSystem.scala

I ported my application to use akka.js and found an increase of size from 251KB to 394KB.
The original application produces the following files with fullOptJs

-rw-r--r--  1 hjs  staff   1.0M 20 Jun 17:18 rww-scala-js-opt.js
-rw-r--r--  1 hjs  staff   251K 20 Jun 17:18 rww-scala-js-opt.js.gz

whereas my ported application produces this:

-rw-r--r--  1 hjs  staff   1.6M 20 Jun 15:24 rww-scala-js-opt.js
-rw-r--r--  1 hjs  staff   394K 20 Jun 15:24 rww-scala-js-opt.js.gz

Is this due to the weak typing of actors as Any => Unit ?

Using scala.js linker we can for example register classes of actors to be loaded at runtime.

starting from a clean install ( and after removing the Eclipse plugins ) if I try to run package I
get the errors below. I tried compiling scalatest-2.3x but that produced differents jars such as .ivy2/local/org.scalatest/scalatest_2.11/3.0.0-M1/bundles/scalatest_2.11.jar - eg no scalatestjs but just scalatest. Using those did not help.

> clean
[success] Total time: 0 s, completed 16-Jun-2015 18:44:21
> package
[info] Updating {file:/Volumes/Dev/Programming/ScalaJS/akka.js/}root...
[info] Updating {file:/Volumes/Dev/Programming/ScalaJS/akka.js/}akkaActorJS...
[info] Resolving org.scalatest#scalatestjs_sjs0.6_2.11;2.3.0-SNAP2 ...
[warn]  module not found: org.scalatest#scalatestjs_sjs0.6_2.11;2.3.0-SNAP2
[warn] ==== local: tried
[warn]   /Users/hjs/.ivy2/local/org.scalatest/scalatestjs_sjs0.6_2.11/2.3.0-SNAP2/ivys/ivy.xml
[warn] ==== public: tried
[warn]   https://repo1.maven.org/maven2/org/scalatest/scalatestjs_sjs0.6_2.11/2.3.0-SNAP2/scalatestjs_sjs0.6_2.11-2.3.0-SNAP2.pom
[warn] ==== Typesafe repository: tried
[warn]   http://repo.typesafe.com/typesafe/releases/org/scalatest/scalatestjs_sjs0.6_2.11/2.3.0-SNAP2/scalatestjs_sjs0.6_2.11-2.3.0-SNAP2.pom
[warn] ==== sonatype-snapshots: tried
[warn]   https://oss.sonatype.org/content/repositories/snapshots/org/scalatest/scalatestjs_sjs0.6_2.11/2.3.0-SNAP2/scalatestjs_sjs0.6_2.11-2.3.0-SNAP2.pom
[info] Resolving org.eclipse.jetty#jetty-continuation;8.1.16.v20140903 ...
[warn]  ::::::::::::::::::::::::::::::::::::::::::::::
[warn]  ::          UNRESOLVED DEPENDENCIES         ::
[warn]  ::::::::::::::::::::::::::::::::::::::::::::::
[warn]  :: org.scalatest#scalatestjs_sjs0.6_2.11;2.3.0-SNAP2: not found

It would be helpful to have a SNAPSHOT release so that I could mere rww-scala-js actor branch into the main branch.

Due to enable GC works properly we need to reshape Unsafe HashMap in something like:
WeakMap[ObjectRef, HashMap[Int, Any]].

this should be easy, it needs the implementation of some methods within our akka.util.Unsafe, probably a little bit of copy paste should do the trick ;-)
The build is already configured within the branch typed

Some parts of Akka.JVM are designed to be run synchronously, but unfortunately we cannot block in JS.

For instance, some points that come to mind

• Initialization of logging
• TestKit

TestKit is the toughest one because it really is 100% blocking. So far I've been able to make it work by using a custom event loop which is able to block, but I wouldn't call it a reliable solution. Ideally the test suite should be refactored to use futures.
I do understand however this is a huge undertaking

@rkuhn @andreaTP @andreaferretti

Integrate download of akka sources using jgit as scala.js and scala-native do.

To reproduce change the last line in the Run.run in the stream demo class to
Streams.complexFlow(true)

This causes the val toStringActorPublisherSource in method Streams.complexFlow to be assigned to the expression Source.actorPublisher[String](Props[ToStringActorPublisher])

Exception stack trace below

ERROR] [Tue Jul 22:13:42 GMT+0100 2016] [main] [akka://streams/user/StreamSupervisor-1/flow-1-1-actorPublisherSource] null akka.actor.ActorInitializationException: akka://streams/user/StreamSupervisor-1/flow-1-1-actorPublisherSource: exception during creation at $c_Lakka_actor_ActorInitializationException.$c_jl_Throwable.fillInStackTrace__jl_Throwable(/Users/solomono/Development/Repository/Git/akka.js-fork/akka-stream-demo/js/target/scala-2.11/demo-fastopt.js:27427:14) at $c_Lakka_actor_ActorInitializationException.$c_jl_Throwable.init___T__jl_Throwable(/Users/solomono/Development/Repository/Git/akka.js-fork/akka-stream-demo/js/target/scala-2.11/demo-fastopt.js:27516:8) at akka.actor.ActorInitializationException.<init>(/Users/solomono/Development/Repository/Git/akka.js-fork/akka-stream-demo/js/target/scala-2.11/demo-fastopt.js:63826:52) at akka.actor.ActorCell.create(/Users/solomono/Development/Repository/Git/akka.js-fork/akka-stream-demo/js/target/scala-2.11/demo-fastopt.js:78844:69) at akka.actor.ActorCell.invokeAll$1(/Users/solomono/Development/Repository/Git/akka.js-fork/akka-stream-demo/js/target/scala-2.11/demo-fastopt.js:78895:18) at $c_Lakka_dispatch_Dispatcher$$anon$1.$c_Lakka_dispatch_Mailbox.processAllSystemMessages__V(/Users/solomono/Development/Repository/Git/akka.js-fork/akka-stream-demo/js/target/scala-2.11/demo-fastopt.js:30826:12) at $c_Lakka_dispatch_Dispatcher$$anon$1.$c_Lakka_dispatch_Mailbox.run__V(/Users/solomono/Development/Repository/Git/akka.js-fork/akka-stream-demo/js/target/scala-2.11/demo-fastopt.js:30776:12) at null._onTimeout(/Users/solomono/Development/Repository/Git/akka.js-fork/akka-stream-demo/js/target/scala-2.11/demo-fastopt.js:30653:19) at Timer.listOnTimeout(timers.js:119:15) Caused by: TypeError: Cannot read property 'prototype' of undefined at $newJSObjectWithVarargs(/Users/solomono/Development/Repository/Git/akka.js-fork/akka-stream-demo/js/target/scala-2.11/demo-fastopt.js:449:45) at akka.util.Reflect$.instantiate(/Users/solomono/Development/Repository/Git/akka.js-fork/akka-stream-demo/js/target/scala-2.11/demo-fastopt.js:13835:12) at akka.util.Reflect$.instantiate(/Users/solomono/Development/Repository/Git/akka.js-fork/akka-stream-demo/js/target/scala-2.11/demo-fastopt.js:13848:17) at akka.actor.NoArgsReflectConstructor.produce(/Users/solomono/Development/Repository/Git/akka.js-fork/akka-stream-demo/js/target/scala-2.11/demo-fastopt.js:21589:57) at akka.actor.ActorCell.newActor(/Users/solomono/Development/Repository/Git/akka.js-fork/akka-stream-demo/js/target/scala-2.11/demo-fastopt.js:79009:73) at akka.actor.ActorCell.create(/Users/solomono/Development/Repository/Git/akka.js-fork/akka-stream-demo/js/target/scala-2.11/demo-fastopt.js:78814:24) at akka.actor.ActorCell.invokeAll$1(/Users/solomono/Development/Repository/Git/akka.js-fork/akka-stream-demo/js/target/scala-2.11/demo-fastopt.js:78895:18) at $c_Lakka_dispatch_Dispatcher$$anon$1.$c_Lakka_dispatch_Mailbox.processAllSystemMessages__V(/Users/solomono/Development/Repository/Git/akka.js-fork/akka-stream-demo/js/target/scala-2.11/demo-fastopt.js:30826:12) at $c_Lakka_dispatch_Dispatcher$$anon$1.$c_Lakka_dispatch_Mailbox.run__V(/Users/solomono/Development/Repository/Git/akka.js-fork/akka-stream-demo/js/target/scala-2.11/demo-fastopt.js:30776:12) at null._onTimeout(/Users/solomono/Development/Repository/Git/akka.js-fork/akka-stream-demo/js/target/scala-2.11/demo-fastopt.js:30653:19)

I'm collecting some potential use cases for akka.js, if anyone has ideas please do feel free to contribute!

Distributed chat application

In this example we have multiple clients (browsers) on which an actor system is running and for each actor system 1-n actors taking care of the UI of the chat. Communication would be done through akka-remote with WebRTC as a transport layer.
The interesting part here is that the existing Akka infrastructure for message delivery can be leveraged to allow the programmer to be completely oblivious about the inner workings of WebRTC

Browser UI Framework

In this example we have an Actor which is listening for DOM events and reacts to them. By composing actor behaviour and encapsulate each element's status inside an actor, we can create reactive dead-simple UIs.
This approach is interesting because it frees the programmer from the constraints of the DOM model and could potentially be a platform on top of which one can build DOM optimizations (diff'ing etc)

example:
https://github.com/unicredit/akka.js-examples/tree/master/calculator

Cross-compilable libraries

In this example we have two projects: a Scala one ("server.scala") and a client one ("client.scala"). Once they are compiled they run in their respective environments (JVM for Akka.JVM, JS VM for Akka.js) but they can still communicate transparently through WebSockets.
This is interesting because it would allow to use one single abstraction for all communications, in a sense it's the complementary of what Play already does in handling WebSockets with Akka actors in the backend.

Visualization Tool

In this example we have a code ("algorithm.scala") implementing an algorithm which runs on a JVM backend ("SERVER"), but which if need be, can also run in the frontend through Akka.js. A visualization interface can easily be built which plugs into the algorithm in a step-by-step fashion and shows each step, thus making the explanation much easier.
The interesting thing is, we could leverage all the existing algorithms already implemented in Akka!

example:
https://github.com/unicredit/akka.js-examples/tree/master/raft

Multicore Computing

JS has historically being a single threaded language and it remains so to this date, however Web Workers provide a way for the "main" thread to spawn more JS VMs and interact with them through message passing. This mechanism allows to perform heavy computation off the UI thread which is thus still responsive to user events.
Unfortunately the message passing API only supports few data structures and Akka.js (through it's built-in serialization) would be able to make working with Web Workers a much more seamless experience. It could also potentially evolve into an optimization if the serialization were to be done into ArrayBuffers which are then sent as Transferable Objects

I think that the idea behind these projects is that a higher level abstraction in the browser, combined with Akka's maturity would open up doors to a bunch of new applications which were previously very cumbersome to develop in vanilla JS

In case you have any questions about the above, please do feel free to ask :D

@rkuhn @andreaTP @andreaferretti

We need to implement this interface since it's heavily used in Akka internally, especially in the various Configurator

Playing around with akka.js at https://scalafiddle.io I noticed a problem with actor instantiation.

This one works fine. Link to fiddle: https://scalafiddle.io/sf/h8XVHMe/0

import akka.actor._

object ShoutBox  {
  def props: Props = Props(new ShoutBox)
}

final class ShoutBox extends Actor {

  override def receive: Receive = {
    case x: String  => println(x.toUpperCase)
  }

}

val system = ActorSystem()

val shout = system.actorOf(ShoutBox.props)
println("Shoutbox created")

shout ! "hello"
shout ! "world"

This one doesn't work. Link to fiddle: https://scalafiddle.io/sf/luBGLkI/1

import akka.actor._

object ShoutBox  {
  def props: Props = Props(classOf[ShoutBox])
}

final class ShoutBox extends Actor {

  override def receive: Receive = {
    case x: String  => println(x.toUpperCase)
  }

}

val system = ActorSystem()

val shout = system.actorOf(ShoutBox.props)
println("Shoutbox created")

shout ! "hello"
shout ! "world"

Can somebody clarify, is this behaviour right, or both ways should work?

Thanks to @solomono we get a great number of tests that already work.
Unfortunately they diverge from akka original sources and this force us to manually realign things.
This is bad an not affordable in the slices of time where akka.js is developed.

At the moment I'm going to evict every failure test but I need a better solution for the future.

find a way to provide a default meaningful configuration that let user use ActorSystem("name") without providing the custom one.

The only missing feature of Akka respect Erlang is dynamic code change.
JS is a very dynamic VM and re-evaluating code using eval could do the trick.
This should be explored.
After a POC stripping down the code to be reloaded to a single actor behavior should be evaluated.

There are many pickling libs and scalajs-pickling is definitely not the best one. I suggest to make websocket implementation pickler-agnostic (like it is with autowire) so people will be able to choose favourite pickling libs, like BooPickler, Prickle, UPickler and so on.

ScalaPB seems to be available on both platforms, probably we can dig a bit on usign Protobuf for messages exchange.

we need first to port to scala.js

• java.util.Optional
• java.net.URLEncoder

should be fun :-)

typesafe.config.Config is written in Java, aka no cross compile.. gotta figure out what to do

@andreaTP @andreaferretti

https://beetta.scalafiddle.io/sf/t9S8d6/0

import fiddle.Fiddle, Fiddle.println
import akka.actor.ActorSystem
import akka.stream._
import akka.stream.scaladsl._
import akka.stream.stage.{GraphStage, GraphStageLogic, InHandler}

implicit val system = ActorSystem("pi")
implicit val dispatcher = system.dispatcher
implicit val materializer = ActorMaterializer()

final class PrintlnSink(prefix: String) extends GraphStage[SinkShape[Any]] {
  val in = Inlet[Any]("PrintlnSink.in")
  override def shape = SinkShape(in)

  override def createLogic(inheritedAttributes: Attributes) = 
    new GraphStageLogic(shape) {
      // a new GraphStageLogic will be created each time we materialize the sink
      // so all state that we want to keep for the stage should be withing the logic.
      // 
      // here we maintain a counter of 
      private var count = 0L

      setHandler(in, new InHandler {
        /**
         * Called when the input port has a new element available. 
         * The actual element can be retrieved via the [[GraphStageLogic.grab()]] method.
         */
        override def onPush(): Unit = {
          val element = grab(in)
          count += 1 // the GraphStage maintains the Actor-like single-threaded illusion
          println(s"[$prefix:$count] $element")
          pull(in)
        }
      })

      // we start the flow of data by an initial pull
      pull(in)
    }
}

Source(1 to 10).runWith(new PrintlnSink("hello"))

Blows up with ERROR: Cannot read property 'portState$1' of null

We could @JSExport some functions to provide entry point from JS, this would allow to use akka.js from JS and other JS-compiled languages

Documentation or examples should show how to use the basic config with a single value override. Like set the loglevel to WARN. Would be nice to see that in documentation. The examples only show parsing a full config from a string.
ConfigFactory.load() doesn't work.

It seems that Logging loading is changed and custom loggers are not loaded.
Not sure if this refer to the entier configuration...