make entries with legacy class names backwards compatible

[bdoyle0182]

fixes the issue where features of akka / pekko that are dependent on the persistence module and will potentially store the class name of an akka / pekko class as a part of the persisted data.

[thjaeckle]

I would adjust the replacement of "akka" in classnames to make it more bulletproof

[bdoyle0182]

I cleaned it up and followed your suggestion good catch there to replaceFirst. I also realized we need to backport this to the old plugin to support roll backs, see this comment on the issue #10

[thjaeckle]

Thanks for the contribution @bdoyle0182 👍
Will release a 1.0.2 containing this fix.

[SakulK]

PSA for anyone that might hit the same issue as me: this fix unfortunately doesn't seem to address a similar issue with PersistentFSM snapshots. Here is the interesting part of the stacktrace that shows up in logs:

java.util.NoSuchElementException: None.get
     at scala.None$.get(Option.scala:627)
     at scala.None$.get(Option.scala:626)
     at pekko.contrib.persistence.mongodb.driver.ScalaDriverPersistenceSnapshotter$.deserializeSnapshot(ScalaDriverPersistenceSnapshotter.scala:43)
     at pekko.contrib.persistence.mongodb.driver.ScalaDriverPersistenceSnapshotter.$anonfun$findYoungestSnapshotByMaxSequence$5(ScalaDriverPersistenceSnapshotter.scala:82)

After digging deeper I found out that deserialize call here:

pekko-persistence-mongo/scala/src/main/scala/pekko/contrib/persistence/mongodb/driver/ScalaDriverPersistenceSnapshotter.scala

Line 44 in b8127da

snap <- serialization.deserialize(content, classOf[Snapshot]).toOption

returns:

Failure(java.io.NotSerializableException: Cannot find manifest class [akka.persistence.fsm.PersistentFSM$PersistentFSMSnapshot] for serializer with id [7].)

Which is thrown from https://github.com/apache/incubator-pekko/blob/main/actor/src/main/scala/org/apache/pekko/serialization/Serialization.scala#L246

Theory: a replacement of akka. => org.apache.pekko. might work if applied to the manifest here:
https://github.com/apache/incubator-pekko/blob/f6af100531e037b4f245f564d7be8c70f0093a4f/persistence/src/main/scala/org/apache/pekko/persistence/serialization/SnapshotSerializer.scala#L113-L115
But that's unfortunately in the main pekko persistence project. I will share a workaround if I find one 😉

[SakulK]

Ok, a hacky workaround that I came up with:

1. Make a copy of org.apache.pekko.persistence.serialization.SnapshotSerializer class from pekko persistence (here called CustomSnapshotSerializer)
2. In snapshotFromBinary replace the last line with:

    serialization
      .deserialize(snapshotBytes, serializerId, manifest)
      .recoverWith {
        case _: NotSerializableException if manifest.startsWith("akka") =>
          serialization.deserialize(snapshotBytes, serializerId, manifest.replaceFirst("akka", "org.apache.pekko"))
      }
      .get

3. Register the serializer in the config, something like this:

pekko.actor {
  serialization-identifiers {
    "org.apache.pekko.persistence.serialization.SnapshotSerializer" = -8
    "org.apache.pekko.persistence.serialization.CustomSnapshotSerializer" = 8
  }
  serializers.customSnapshotSerializer = "org.apache.pekko.persistence.serialization.CustomSnapshotSerializer"
  serialization-bindings {
    "org.apache.pekko.persistence.serialization.Snapshot" = customSnapshotSerializer
  }
}

I'm not sure if it makes sense to propose the change from point 2. to the main pekko repo 🤔

[pjfanning]

@SakulK could you create a discussion at https://github.com/apache/incubator-pekko ?

It seems like we might need doc or code changes in core pekko to help here.

One thing though - have you tried just having the akka jars on your classpath? Akka and Pekko use different package names so they shouldn't affect each other. In theory having the akka jars on your classpath should stop you getting class not found errors.

[SakulK]

@pjfanning I did a quick test with akka-actor and akka-persistance on the classpath and it didn't help, the error did change though:

java.io.NotSerializableException: Can't deserialize object of type class akka.persistence.fsm.PersistentFSM$PersistentFSMSnapshot