Consumer: allow manually setting offset

[jameshaydon]

Currently Kafka.Consumer.Subscription.offsetReset only allows setting to Earliest or Latest. Could an explicit offset be added? Implementation would presumably follow:

https://github.com/edenhill/librdkafka/wiki/Manually-setting-the-consumer-start-offset

[AlexeyRaga]

To implement it in a way that offsets could be provided with subscription we need to re-design the subscription API. Need to think about how to make it conveniently.
And we don't provide the access to the "raw" rebalance callback where you could alter the topic/partition/offset properties. Which can be changed/updated as well, for example instead of

RebalanceEvent -> IO ()

we could accept something like

RebalanceEvent -> IO (Maybe [TopicPartition])

but then it is inconvenient because this sort of a callback doesn't really make sense for, say, BeforeRevoke event...

Something can be done with careful thinking, but in the meantime, you can use seek within your AfterRebalance callback to get the same effect.

Would it solve your immediate issue?