He-Pin opened a new issue, #3243: URL: https://github.com/apache/pekko/issues/3243
### Description `ActorGraphInterpreter` holds a strong reference to its initial `GraphInterpreterShell` via the `_initial` constructor val. When the actor outlives the initial shell (e.g., while hosting subfused interpreters registered via `registerShell`), the initial shell and all its `GraphStageLogic` instances cannot be garbage collected for the actor's lifetime. ### Affected code `stream/src/main/scala/org/apache/pekko/stream/impl/fusing/ActorGraphInterpreter.scala`: - Line 732: `_initial` is a constructor **val** (not a `var`), stored as a private final field - Line 792: `preStart()` calls `tryInit(_initial)` but never releases the reference - Line 848: `postStop()` clears `activeInterpreters` but does not null out `_initial` ### Reproduction scenario The `SubFusingActorMaterializerImpl` (line 739) reuses the same `ActorGraphInterpreter` actor to host additional shells via `registerShell` (line 768). When the initial shell's stream completes, it is removed from `activeInterpreters` (line 822), but `_initial` still holds a reference to it. Any operator that uses subfusing (e.g., `flatMapConcat`, `PrefixAndTail`-derived operators) will trigger this pattern. ### Impact In long-running streams with subfused operators, the initial shell and all its graph stage logics remain pinned in memory for the actor's entire lifetime, even after the initial stream completes. This is a memory leak in subfusing scenarios. ### Suggested fix 1. Convert `_initial` from a constructor val to `private var _initial` 2. Set `_initial = null` at the end of `preStart()` after `tryInit` completes 3. Update any references to `_initial` in debug logging to use the `shell` parameter instead -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
