Support Scala closure serialization

[asarkar]

See https://stackoverflow.com/q/47806670/839733 for details

case class TestRequest[T](app: String, locker: MeatLocker[T])

val factory: Stats => Unit = stats => {
  stats.app shouldBe (app)
  stats.unit shouldBe (SECONDS)
  stats.startupDurations should have length (10)
}

val locker: MeatLocker[Stats => Unit] = MeatLocker(factory)

val file = SerializationUtil.write(TestRequest[Stats => Unit](app, locker))
val state = SerializationUtil.read[TestRequest[Stats => Unit]](file)

(state.locker.get) (newStats())

Could not serialize lambda
java.lang.RuntimeException: Could not serialize lambda
at com.esotericsoftware.kryo.serializers.ClosureSerializer.write(ClosureSerializer.java:67)
at com.esotericsoftware.kryo.Kryo.writeClassAndObject(Kryo.java:651)
at com.twitter.chill.SerDeState.writeClassAndObject(SerDeState.java:64)
at com.twitter.chill.KryoPool.toBytesWithClass(KryoPool.java:116)
at com.twitter.chill.MeatLocker.(MeatLocker.scala:32)
at com.twitter.chill.MeatLocker$.apply(MeatLocker.scala:21)

[johnynek]

What version of kryo and scala are you using. This should work. we do it all the time in scalding.

[johnynek]

Actually it isn’t magic. Not everything can be serialized (things like Threads or file handles for instance). I have found that test frameworks often have such things and your example seems to capture one. I am not surprised this does not work.

[asarkar]

I'll post here the same update I did on SO.

Perhaps I should clarify the actual use case that is running into this issue to provide more context. The function is a callback from Akka HTTP route like the following:

path("stats") {
  logRequest("/stats") {
    completeWith(instanceOf[List[Stats]]) { callback =>
      requestHandler ! GetStatsRequest(callback)
    }
  }
}

The handler actor persists the request until it gets a response. It may take more than one response to construct the final output.

I did some digging and it appears that the callback implementation is a CallbackRunnable.

[johnynek]

Can you post also the version of chill you were using and the scala version (2.11, 2.12?)

[asarkar]

chill-akka_2.12:0.9.2, Scala 2.12.4. I've since reverted that code, so you won't find it in the project I linked above.