migesok commented on code in PR #2027:
URL: https://github.com/apache/pekko/pull/2027#discussion_r2272743628
##########
persistence/src/main/scala/org/apache/pekko/persistence/journal/AsyncWriteJournal.scala:
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@@ -67,9 +67,21 @@ trait AsyncWriteJournal extends Actor with WriteJournalBase
with AsyncRecovery {
final val receiveWriteJournal: Actor.Receive = {
// cannot be a val in the trait due to binary compatibility
val replayDebugEnabled: Boolean = config.getBoolean("replay-filter.debug")
+ val enableGlobalWriteResponseOrder: Boolean =
config.getBoolean("write-response-global-order")
+
val eventStream = context.system.eventStream // used from Future callbacks
implicit val ec: ExecutionContext = context.dispatcher
+ // should be a private method in the trait, but it needs the
enableGlobalWriteResponseOrder field which can't be
+ // moved to the trait level because adding any fields there breaks
bincompat
+ def sendWriteResponse(msg: Any, snr: Long, target: ActorRef, sender:
ActorRef): Unit = {
Review Comment:
Unfortunately, no amount of annotations would save me from runtime class
errors here.
This method needs access to the "memoized" config option, which has to be a
val/var/lazy val - enableGlobalWriteResponseOrder. Which I currently put under
` final val receiveWriteJournal: Actor.Receive = {...}` scope. My first version
had the field on the trait level as a private val - right under here:
https://github.com/apache/pekko/blob/e7e71a3adffdd8b19d800b22843780b54f56d4b8/persistence/src/main/scala/org/apache/pekko/persistence/journal/AsyncWriteJournal.scala#L60
Then it lead to runtime issues:
- you have a concrete plugin class extending AsyncWriteJournal built against
the old version, without the new private val
- you try to run it against the new AsyncWriteJournal version
- adding a new private/packag-private/private[this] val to trait results in
new abstract methods in the generated interface
- classloading of the plugin class fails in runtime because an interface it
implements has new abstract methods which the concrete class does not implement
It seems I was not the first one to hit this issue in this trait:
```
final val receiveWriteJournal: Actor.Receive = {
// cannot be a val in the trait due to binary compatibility
val replayDebugEnabled: Boolean =
config.getBoolean("replay-filter.debug")
```
TBH before this ordeal I wasn't aware that adding private fields to a trait
breaks bincompat but I was able to confirm it on small examples:
https://gist.github.com/migesok/71c5e5feb1ba4fff8c6515f42922df11
Please let me know if there is a better way to structure it without breaking
bincompat.
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