I think of it as default.offset :) Realistically though, changing the configuration name will probably cause more confusion than leaving a bad name as is.
On Tue, Apr 14, 2015 at 11:10 AM, James Cheng <jch...@tivo.com> wrote: > "What to do when there is no initial offset in ZooKeeper or if an offset is > out of range" > > I personally find the name "auto.offset.reset" to be somewhat confusing. > That's mostly because I only knew of it as the "no initial offset" setting. > > An alternate name could be "auto.offset.initial", to handle the "no initial > offset in Zookeeper" case. But that doesn't describe the "offset out of > range" case. > > -James > > On Apr 13, 2015, at 10:28 PM, Ewen Cheslack-Postava <e...@confluent.io> wrote: > >> On Mon, Apr 13, 2015 at 10:10 PM, bit1...@163.com <bit1...@163.com> wrote: >> >>> Hi, Kafka experts: >>> >>> I got serveral questions about auto.offset.reset. This configuration >>> parameter governs how consumer read the message from Kafka when there is >>> no initial offset in ZooKeeper or if an offset is out of range. >>> >>> Q1. "no initial offset in zookeeper " means that there isn't any consumer >>> to consume the message yet(The offset is set once the consumer starts to >>> consume)? >>> >> >> Yes, or if you consumed messages, but auto offset commit is disabled and >> you haven't explicitly committed any offsets. >> >> >>> Q2: What does "offset is out of range" mean? Can you eleborate one >>> scenario when "offset is out of range" could happen? >>> >> >> Kafka uses a retention policy for topics to expire data and clean it up. If >> some messages expire and your consumer hasn't run in awhile, the last >> committed offset may no longer exist. >> >> >>> >>> auto.offset.reset has two values:smallest and largest. >>> Assume one scenario: A producer has produced 10 messages to kafka, and >>> there is no consumer yet to consume it. >>> Q3: If auto.offset.reset is set to "smallest", does it mean that the >>> consumer will read the message from the offset 0?(0 is smallest here) >>> >> >> Yes. >> >> >>> Q4: If auto.offset.reset is set to "largest", does it mean that the >>> consumer will not read any message but wait until new messages come? >>> >> >> Also correct. This is why in the quickstart you need to use the >> --from-beginning flag on the console consumer. Since the consumer is >> executed after the console producer it wouldn't see any messages unless it >> set auto.offset.reset to smallest, which is what --from-beginning does. >> >> >>> >>> >>> >>> bit1...@163.com >>> >> >> >> >> -- >> Thanks, >> Ewen >
