Hi, I was using the new state processor api to read a savepoint produced by Flink 1.5.3, and got an StateMigrationException with message “For heap backends, the new namespace serializer must be compatible”.
Concretely, the state I was trying to read is a MapState<String, Long> within a WindowOperator(TriggerContext) which is keyed by a string field, so the key & value data types and the corresponding serializers should be the basic one here (POJOSerializer). However, the error indicates the problem is about namespace serializer which I have not much knowledge about. So I dig a bit into the source code to find that the namespace serializer is not a highly configurable one, and both state processor api and the state to be read seem to use the same namespace serializer, `VoidNamespaceSerializer` (please correct me if I’m wrong). It still doesn’t explain why the error happened. Please point me to the right direction. Thanks a lot! Best, Paul Lam
