Poloniex backfill not retrieving all possible trades

[bradrisse]

Currently the poloniex trade history api says "Returns the past 200 trades for a given market, or up to 50,000 trades between a range specified in UNIX timestamps by the "start" and "end" GET parameters."

Zenbot currently adds or subtracts 12 hours when backfilling https://github.com/DeviaVir/zenbot/blob/unstable/extensions/exchanges/poloniex/exchange.js#L62.

The issue if more than 50k trades occurred within the timeframe of 12 hours, then trades are missed.

To fix a check should be in place to check if 50k or greater is returned. If true then re-call the previous trade history in smaller intervals until less than 50k is reached. Once complete resume 12 hour ranges.