Yeah, except if we do that we do not pass the TCK. Looking at Cassandra, we need to store the writerUuid.
So now we need another bit of state ... essentially we need to record the position at which the writerUuid changes. Then we need to remap them during adaptation.
As noted in CONTROLLER-2044 and , we have repeating writerUuid in the journal.
Perusing akka.persistence, this value is used only for sanity checking in a filter – and that filter will happily live with just empty strings.
On the write side, write a null String instead of writerUuid.
On the read side, read the uuid, bump always report empty string.
This should be a completely ABI compatible change.