Using wrong compareTo function for TimeBasedUUIDs in eventsByTag

[SebastianMax]

Hi,

I am using akka-persistence-inmemory not only for unit-testing, but also for a proof-of-concept application that runs longer than some seconds. The application "writes" events to the inmemory-journal and synchronizes them via PersistenceQuery using readJournal.eventsByTag. The offset-mode is set to uuid.

During testing I stumbled over the problem that after a (random) amount of time the eventsByTag source stops emitting events that are persisted. I currently assume this is because the InMemoryJournalStorage.eventsByTag uses > to compare two TimeBasedUUIDs, which uses the java.util.UUID.compareTo (InMemoryJournalStorage)

However, this compareTo function does not use the same ordering as the TimeBasedUUIDs which are generated in UUIDS.timeBased().

Therefore, it may happen that a current timeBasedUUID is less than an older timeBasedUUID, and thus the eventsByTag does not return the old (but not yet delivered) event.

A small failing test confirms this behaviour:

    import java.time.{OffsetDateTime, ZoneOffset}
    import akka.persistence.inmemory.util.UUIDs
    import akka.persistence.query.TimeBasedUUID
    import org.scalatest.{Matchers, WordSpecLike}

    class TimeBasedUUIDSpec
      extends WordSpecLike with Matchers {

      "The TimeBasedUUID" when {
        "comparing two TimeBasedUUIDs that differ by a second using '<' " should {
          "compare correctly" in {

            val one = TimeBasedUUID(UUIDs.startOf(OffsetDateTime.of(2002, 1, 1, 0, 0, 0, 0, ZoneOffset.UTC).toEpochSecond * 1000))
            val two = TimeBasedUUID(UUIDs.startOf(OffsetDateTime.of(2002, 1, 1, 0, 0, 1, 0, ZoneOffset.UTC).toEpochSecond * 1000))

            one.value.timestamp() < two.value.timestamp() shouldBe true
            one < two shouldBe true
          }
        }
      }
    }

A possible fix could be to use a different compare function, like it is done here.

[dnvriend]

Hi, could you please test 2.4.18.2-SNAPSHOT (the master branch) and check if you still have the issue. I've made some small changes.

[SebastianMax]

Hi, sorry for the late reply, I did not see your improvements until now. Looks very good and works for me, thank you!

[toerni]

Can the same bug also be fixed for the 2.5 version of akka?