The firehose needs to return that it doesn't have any more rows in
order to achieve that. Unfortunately, the firehoses that are
currently bundled don't have an external mechanism to trigger it.
Technically, if your topic goes dry and you use systemTime for your
rejectionPolicy, then it will eventually hand off the data and just
have nothing else to do.
Given that we generally deploy in an environment where things get
reprocessed from batch, this is one of those things that hasn't gotten
the attention it really should. Would make a lot of sense to have an
HTTP endpoint or something where you could gracefully shutdown the