Makes get_queued_events FIFO or LIFO

[cbeaujoin-stellar]

Sometime when connectivity brokes it's more interesting to retrieve the fresh data first and not the oldest ones. A simple improvment would be to have choice between LIFO or FIFO in the DatabaseCache.get_queued_events method.

• FIFO (current) :

      query_fetch = '''
          SELECT `event_id`, `event_text` FROM `event` WHERE `pending_delete` = 0 LIMIT ?;'''

• LIFO (should be):

      query_fetch = '''
          SELECT `event_id`, `event_text` FROM `event` WHERE `pending_delete` = 0 ORDER BY `event_id` DESC LIMIT ?;'''

It could be enabled/disabled using a constant, ie: constants.QUEUED_EVENTS_FLUSH_LIFO = True

Call hierarchy is : LogProcessingWorker._fetch_queued_events_for_flush >DatabaseCache.get_queued_events

[eht16]

Assuming that on subsequent push attempts, all events will be pushed shortly, I don't think it makes a big difference.

Though if you want, create a PR.