Hi Odd,
why have you chosen this versioning approach instead of a protobuf based
one, for example? What are the advantages?
On 19.05.14 14:08, Odd Möller wrote:
Hi!
We have a versioning extension that we are experimenting with at the
moment (it is quite experimental at this point and completely without
tests):
https://github.com/odd/akka/tree/wip-persistence-odd/akka-contrib/src/main/scala/akka/contrib/persistence/versioning
The basic idea is to attach a version to the actual data to be
persisted and then when saving the data, instead of serializing the
data class as is, save a tuple containing the data of the fields of
the class. Then at load time you can transform historic versions of
the saved data to the latest version (based on the attached version).
For example:
import akka.contrib.persistence.versioning._
// Version 1 -- present in the event log but no longer available at
runtime
// case class Name(first: String, last: String) extends Versioned[Name]
// Version 2 -- current version of the class at runtime
case class Name(first: String, last: String, title: Option[String] =
None) extends Versioned[Name]
object Name extends Versioned.Companion[Name] {
override def apply(data: (Version, Any)): Name = {
case (Version.Major(1), (first: String, last: String)) =>
Name(first, last)
case (Version.Major(2), (first: String, last: String, title:
Option[String])) => Name(first, last, title)
case (v, d) => throw new IllegalStateException(s"Unknown version
encountered [version: $v, data: $d]")
}
}
The versioned serializer needs to be present in the akka config:
serializers {
versioned = "akka.contrib.persistence.versioning.VersionedSerializer"
}
serialization-bindings {
"akka.contrib.persistence.versioning.Versioned" = versioned
}
On Thu, May 15, 2014 at 7:41 PM, Per Johansson
<[email protected] <mailto:[email protected]>> wrote:
What about using "versioned" objects (like Foo_v01, Foo_v02) and
convert to the latest version when reading a snapshot?
Anyone with experience of that approach?
Was thinking it might be less work if you want to have e.g. maps
after derserialization? (maps not supported in protobuf)
/Per
On Thursday, 8 May 2014 09:47:46 UTC+1, Martin Krasser wrote:
On 08.05.14 10:43, Tim Pigden wrote:
Hi
I've found a new thing to worry about :-)
If I use an eventsource model and content myself with the
default serialization and akka persistence, what's the
likelihood of my serialized objects becoming unreadable in
the future? What's the long-term stability of the default
akka serialization mechanism?
By default, events are serialized with Akka's Java serializer.
Is there a recommendation?
Use a custom
<http://doc.akka.io/docs/akka/2.3.2/scala/persistence.html#custom-serialization>
protobuf (or similar) serializer to serialize your events.
This will support backwards compatible changes to your event
schema.
Tim
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