Doctor, I ended up using thrift + twitter's scrooge for messaging and
snapshoting. Scrooge generated pretty nice case classes for thrift structs.
The downside is that I have to list all the generated classes in my
serializer and the serialization config file, as show below.
If anyone knows how to write a generalized serializer for thrift+scrooge,
please share.
import akka.serialization.Serializer
import com.twitter.bijection.scrooge.BinaryScalaCodec
import autogen.data._
class EventSerializer extends Serializer {
val includeManifest: Boolean = true
val identifier = 870725
def toBinary(obj: AnyRef): Array[Byte] = obj match {
case m: Message1 => BinaryScalaCodec(Message1)(m)
case m: Message2 => BinaryScalaCodec(Message2)(m)
case m => throw new IllegalArgumentException("Cannot serialize object:
" + m)
}
def fromBinary(bytes: Array[Byte],
clazz: Option[Class[_]]): AnyRef = clazz match {
case Some(c) if c == classOf[Message1.Immutable] =>
BinaryScalaCodec(Message1).invert(bytes).get
case Some(c) if c == classOf[Message2.Immutable] =>
BinaryScalaCodec(Message2).invert(bytes).get
case Some(c) => throw new IllegalArgumentException("Cannot deserialize
class: " + c.getCanonicalName)
case None => throw new IllegalArgumentException("No class found in
EventSerializer when deserializing array: " + bytes.mkString(""))
}
}
The config is like:
akka {
actor {
serializers {
event = "com.my.EventSerializer"
}
serialization-bindings {
"com.coinport.coinex.data.Message1" = event
"com.coinport.coinex.data.Message2" = event
}
}
}
On Friday, March 14, 2014 5:32:13 AM UTC+8, rkuhn wrote:
>
> Hi Daniel,
>
> 11 mar 2014 kl. 09:13 skrev Daniel Wang <[email protected] <javascript:>
> >:
>
> Akka core developers, congratulations for the 2.3.0 release. My team are
> using it to develop our product right now. Thank you.
>
> One thing we are discussing (and still haven't come to an conclusion) is
> how to make sure all persistent events (commands if we use
> command-sourcing) will be backward compatible. We can certainly use
> protobuf WDL to defined all events/commands (and I did try), but it turns
> out working with Java POJO classes with Akka is so unnature as we are all
> spoiled by pattern matching. I also tried to use Twitter's scrooge to
> compile thrift files into scala code (so all thrift structs are case
> classes), but I didn't manage to come up with a general serializer (by
> 'general' I mean there is no need to serialized each event/command type
> case-by-case as the protobuf serializer). I'm going to try Kryo serializer
> soon. I wish I can have some luck.
>
>
> What we do with our own messages is to use the generated protobuf Java
> classes only as an intermediate step during serialization/deserialization
> so that we can work with case classes (for the reasons you state as well).
> This conversion will also help you decouple the versioning logic from the
> business logic, i.e. when you deserialize an old version of an event the
> conversion into a case class can synthesize defaults for those fields which
> are missing.
>
> Processor's in-memory state snapshots are also need to be backward
> compatible, otherwise each upgrade of events/commands will reply all
> history events/commands, given events/commands persistence are backward
> copyable. The idea on my mind is to 1) convert the scala-collection based
> memory snapshot into a huge thrift/protobuf strutter, then 2) serialize the
> thrift/protobuf structure to byte arrays. To make the conversion async (not
> to block processor event loop), I may have to write a customer serializer.
>
>
> Yes, this sounds about right.
>
> Regards,
>
> Roland
>
>
> It will be great if someone from the Akka dev team can comment and share
> their thoughts.
>
>
>
> --
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>
>
>
> *Dr. Roland Kuhn*
> *Akka Tech Lead*
> Typesafe <http://typesafe.com/> – Reactive apps on the JVM.
> twitter: @rolandkuhn
> <http://twitter.com/#!/rolandkuhn>
>
>
--
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