TraditionalWorkQueue.finalizeWorkQueue never cancels queued operations: removeAll(empty list) is a no-op

[vharseko]

Problem

TraditionalWorkQueue.finalizeWorkQueue() is supposed to send a "server shutting down" cancel response to every operation still sitting in the queue:

    // Send responses to any operations in the pending queue to indicate that
    // they won't be processed because the server is shutting down.
    CancelRequest cancelRequest = new CancelRequest(true, reason);
    ArrayList<Operation> pendingOperations = new ArrayList<>();
    opQueue.removeAll(pendingOperations);
    for (Operation o : pendingOperations)
    {
      ...
      o.abort(cancelRequest);
      ...
    }

Collection.removeAll(collection) removes from the queue the elements contained in the argument — and pendingOperations is a freshly created empty list, so the call removes nothing and leaves pendingOperations empty. The abort loop below never executes.

The intended call is clearly opQueue.drainTo(pendingOperations) (move all queued operations into the list, then abort each one).

Impact

Operations still queued at shutdown never receive the UNAVAILABLE/cancelled response promised by the surrounding code and the WARN_QUEUE_UNABLE_TO_CANCEL handling; clients block waiting for a response until their connection is torn down. Low severity in practice (shutdown path, queue is usually empty), but the code as written is a no-op.

Notes

This is a long-standing upstream bug: the same removeAll(new ArrayList<>()) pattern is already present in the OpenDS-era TraditionalWorkQueue (before the OpenDJ 3 rewrite), so it dates back to the original implementation.

Found while auditing the slow TestNG group (follow-up to #684/#688).