Feature Request: Stateless Mode

[moll-dev]

Hey all,

I use Jetstream for a couple of services that I wrote for indexing likes / posts / etc. I was wondering if it's possible to have a stateless config for Jetstream that uses a consumer that doesn't write events to disk for replay. Might be nice to quickly scale up a bunch of instances that are just live tailing.

It should be pretty easy to do:

1. Add a field (single flag or custom config struct) to the firehose Consumer, skip event persists in the RunSequencer goroutine.
2. Add logic to bounce any clients that request a cursor before the current time.

Alternatively a "retention" config could be added to periodically clean the local RocksDB instance. And if the retention was set to 0 (seconds/minutes/days or events) it would skip the consumer DB entirely.

This should be a good start. As there's only one FH consumer per Server instance, I don't think the current code could support transparent subscriber requests to backfill.

I've got some cycles to work on this shortly, I don't have any urgent need for stateless, more of a performance experiment.
Let me know what you think!