log retention and rolling behaviors

[Jay Guo <gu...@gmail.com>]

Dear Kafka gurus,

I'm trying to confirm following behaviors in Kafka 0.10.x:

- `log.roll.x` and `log.segment.bytes` are checked only when new message
comes in. In another word, there's no scheduled job to roll out new segment
files
- `log.retention.time` is checked by scheduled job, and when in-use segment
file expires, new segment file is forced to be created, and the old one is
marked as deleted
- `log.retention.bytes` is does NOT force a new segment file to be created
though. Also, it is only checked against closed segment files.

I'd appreciate your comments! Thanks in advance!
- J