@Override
    public void toData(final DataOutput out) throws IOException {
      filter.incNumToDataInvocations();
      DataSerializer.writeString(id, out);
    }
Regression test for TRAC #50366: NullPointerException with AsyncEventQueue#size() when number
of dispatchers is more than 1
geode-core/src/distributedTest/java/org/apache/geode/internal/cache/wan/asyncqueue/ConcurrentAsyncEventListenerDistributedTest.java