One of the recent integration had a failed Storage test: http://jenkins.inspectit.rocks/job/inspectIT%20-%20Integration/67/.
After detailed investigation it was concluded that there is possibility that indexing tree saving fails with AsynchronousCloseException when storage is being finalized/closed. Problem is that this write creates one additional write task and we are not waiting for the task to be finished. As immediately after we are closing all the related channels we might be faster in closing then writing. Thus, the exception occurs:
As defined on Java API: