I think this is less of an issue: we can use the same patterns as in the
request protocol, i.e.:
write(Map[TP, Long]) // write the checkout point in v0 format
write(Map[TP, Pair[Long, Long]]) // write the checkout point in v1 format
CheckpointedOffsets read() // read the file relying on its version id
class CheckpointedOffsets {
Integer getVersion();
Long getFirstOffset();
Long getSecondOffset(); // would return NO_AVAILABLE with v0 format
}
As I think of it, another benefit is that we wont have a partition that
only have one of the watermarks in case of a failure in between writing two
files.
Guozhang
On Sun, Jan 22, 2017 at 12:03 AM, Dong Lin <lindon...@gmail.com> wrote:
> Hey Guozhang,
>
> Thanks for the review:) Yes it is possible to combine them. Both solution
> will have the same performance. But I think the current solution will give
> us simpler Java class design. Note that we will have to change Java API
> (e.g. read() and write()) of OffsetCheckpoint class in order to provide a
> map from TopicPartition to a pair of integers when we write to checkpoint
> file. This makes this class less generic since this API is not used by log
> recovery checkpoint and log cleaner checkpoint which are also using
> OffsetCheckpoint class.
>
> Dong
>
>
>
>
>
>
>
> On Sat, Jan 21, 2017 at 12:28 PM, Guozhang Wang <wangg...@gmail.com>
> wrote:
>
> > Hi Dong,
> >
> > Sorry for being late on reviewing this KIP. It LGTM overall, but I'm
> > wondering if we can save adding the "replication-low-watermark-
> checkpoint"
> > file by just bumping up the version number of "replication-offset-
> > checkpoint"
> > to let it have two values for each partition, i.e.:
> >
> > 1 // version number
> > [number of partitions]
> > [topic name] [partition id] [lwm] [hwm]
> >
> >
> > This will affects the upgrade path a bit, but I think not by large, and
> all
> > other logic will not be affected.
> >
> >
> > Guozhang
> >
> >
> >
> > On Wed, Jan 18, 2017 at 6:12 PM, Dong Lin <lindon...@gmail.com> wrote:
> >
> > > Thanks to everyone who voted and provided feedback!
> > >
> > > This KIP is now adopted with 3 binding +1s (Jun, Joel, Becket) and 2
> > > non-binding +1s (Radai, Mayuresh).
> > >
> > > Thanks,
> > > Dong
> > >
> > > On Wed, Jan 18, 2017 at 6:05 PM, Jun Rao <j...@confluent.io> wrote:
> > >
> > > > Hi, Dong,
> > > >
> > > > Thanks for the update. +1
> > > >
> > > > Jun
> > > >
> > > > On Wed, Jan 18, 2017 at 1:44 PM, Dong Lin <lindon...@gmail.com>
> wrote:
> > > >
> > > > > Hi Jun,
> > > > >
> > > > > After some more thinking, I agree with you that it is better to
> > simply
> > > > > throw OffsetOutOfRangeException and not update low_watermark if
> > > > > offsetToPurge is larger than high_watermark.
> > > > >
> > > > > My use-case of allowing low_watermark > high_watermark in 2(b) is
> to
> > > > allow
> > > > > user to purge all the data in the log even if that data is not
> fully
> > > > > replicated to followers. An offset higher than high_watermark may
> be
> > > > > returned to user either through producer's RecordMetadata, or
> through
> > > > > ListOffsetResponse if from_consumer option is false. However, this
> > may
> > > > > cause problem in case of unclean leader election or when consumer
> > seeks
> > > > to
> > > > > the largest offset of the partition. It will complicate this KIP if
> > we
> > > > were
> > > > > to address these two problems.
> > > > >
> > > > > At this moment I prefer to keep this KIP simple by requiring
> > > > low_watermark
> > > > > <= high_watermark. The caveat is that if user does want to purge
> > *all*
> > > > the
> > > > > data that is already produced, then he needs to stop all producers
> > that
> > > > are
> > > > > producing into this topic, wait long enough for all followers to
> > catch
> > > > up,
> > > > > and then purge data using the latest offset of this partition, i.e.
> > > > > high_watermark. We can revisit this if some strong use-case comes
> up
> > in
> > > > the
> > > > > future.
> > > > >
> > > > > I also updated the KIP to allow user to use offset -1L to indicate
> > > > > high_watermark in the PurgeRequest. In the future we can allow
> users
> > to
> > > > use
> > > > > offset -2L to indicate that they want to purge all data up to
> > > > logEndOffset.
> > > > >
> > > > > Thanks!
> > > > > Dong
> > > > >
> > > > >
> > > > > On Wed, Jan 18, 2017 at 10:37 AM, Jun Rao <j...@confluent.io>
> wrote:
> > > > >
> > > > > > Hi, Dong,
> > > > > >
> > > > > > For 2(b), it seems a bit weird to allow highWatermark to be
> smaller
> > > > than
> > > > > > lowWatermark. Also, from the consumer's perspective, messages are
> > > > > available
> > > > > > only up to highWatermark. What if we simply throw
> > > > > OffsetOutOfRangeException
> > > > > > if offsetToPurge is larger than highWatermark?
> > > > > >
> > > > > > Thanks,
> > > > > >
> > > > > > Jun
> > > > > >
> > > > > > On Tue, Jan 17, 2017 at 9:54 PM, Dong Lin <lindon...@gmail.com>
> > > wrote:
> > > > > >
> > > > > > > Hi Jun,
> > > > > > >
> > > > > > > Thank you. Please see my answers below. The KIP is updated to
> > > answer
> > > > > > these
> > > > > > > questions (see here
> > > > > > > <https://cwiki.apache.org/confluence/pages/
> > > diffpagesbyversion.action
> > > > ?
> > > > > > > pageId=67636826&selectedPageVersions=5&selectedPageVersions=6>
> > > > > > > ).
> > > > > > >
> > > > > > > 1. Yes, in this KIP we wait for all replicas. This is the same
> as
> > > if
> > > > > > > producer sends a messge with ack=all and isr=all_replicas. So
> it
> > > > seems
> > > > > > that
> > > > > > > the comparison is OK?
> > > > > > >
> > > > > > > 2. Good point! I haven't thought about the case where the
> > > > > user-specified
> > > > > > > offset > logEndOffset. Please see answers below.
> > > > > > >
> > > > > > > a) If offsetToPurge < lowWatermark, the first condition
> > > > > > > of DelayedOperationPurgatory will be satisfied immediately when
> > > > broker
> > > > > > > receives PurgeRequest. Broker will send PurgeResponse to admin
> > > client
> > > > > > > immediately. The response maps this partition to the
> > lowWatermark.
> > > > > > >
> > > > > > > This case is covered as the first condition of
> > > > > DelayedOperationPurgatory
> > > > > > in
> > > > > > > the current KIP.
> > > > > > >
> > > > > > > b) If highWatermark < offsetToPurge < logEndOffset, leader will
> > > send
> > > > > > > FetchResponse with low_watermark=offsetToPurge. Follower
> records
> > > the
> > > > > > > offsetToPurge as low_watermark and sends FetchRequest to the
> > leader
> > > > > with
> > > > > > > the new low_watermark. Leader will then send PurgeResponse to
> > admin
> > > > > > client
> > > > > > > which maps this partition to the new low_watermark. The data in
> > the
> > > > > range
> > > > > > > [highWatermark, offsetToPurge] will still be appended from
> leader
> > > to
> > > > > > > followers but will not be exposed to consumers. And in a short
> > > period
> > > > > of
> > > > > > > time low_watermark on the follower will be higher than their
> > > > > > highWatermark.
> > > > > > >
> > > > > > > This case is also covered in the current KIP so no change is
> > > > required.
> > > > > > >
> > > > > > > c) If logEndOffset < offsetToPurge, leader will send
> > PurgeResponse
> > > to
> > > > > > admin
> > > > > > > client immediately. The response maps this partition to
> > > > > > > OffsetOutOfRangeException.
> > > > > > >
> > > > > > > This case is not covered by the current KIP. I just added this
> as
> > > the
> > > > > > > second condition for the PurgeRequest to be removed from
> > > > > > > DelayedOperationPurgatory (in the Proposed Change section).
> Since
> > > the
> > > > > > > PurgeRequest is satisfied immediately when the leader receives
> > it,
> > > it
> > > > > > > actually won't be put into the DelayedOperationPurgatory.
> > > > > > >
> > > > > > > 3. Yes, lowWatermark will be used when smallest_offset is used
> in
> > > the
> > > > > > > ListOffsetRequest. I just updated Proposed Change section to
> > > specify
> > > > > > this.
> > > > > > >
> > > > > > > Thanks,
> > > > > > > Dong
> > > > > > >
> > > > > > > On Tue, Jan 17, 2017 at 6:53 PM, Jun Rao <j...@confluent.io>
> > wrote:
> > > > > > >
> > > > > > > > Hi, Dong,
> > > > > > > >
> > > > > > > > Thanks for the KIP. Looks good overall. Just a few more
> > comments.
> > > > > > > >
> > > > > > > > 1."Note that the way broker handles PurgeRequest is similar
> to
> > > how
> > > > it
> > > > > > > > handles ProduceRequest with ack = -1 and isr=all_replicas".
> It
> > > > seems
> > > > > > that
> > > > > > > > the implementation is a bit different. In this KIP, we wait
> for
> > > all
> > > > > > > > replicas. But in producer, acks=all means waiting for all
> > in-sync
> > > > > > > replicas.
> > > > > > > >
> > > > > > > > 2. Could you describe the behavior when the specified
> > > offsetToPurge
> > > > > is
> > > > > > > (a)
> > > > > > > > smaller than lowWatermark, (b) larger than highWatermark, but
> > > > smaller
> > > > > > > than
> > > > > > > > log end offset, (c) larger than log end offset?
> > > > > > > >
> > > > > > > > 3. In the ListOffsetRequest, will lowWatermark be returned
> when
> > > the
> > > > > > > > smallest_offset option is used?
> > > > > > > >
> > > > > > > > Thanks,
> > > > > > > >
> > > > > > > > Jun
> > > > > > > >
> > > > > > > >
> > > > > > > > On Wed, Jan 11, 2017 at 1:01 PM, Dong Lin <
> lindon...@gmail.com
> > >
> > > > > wrote:
> > > > > > > >
> > > > > > > > > Hi all,
> > > > > > > > >
> > > > > > > > > It seems that there is no further concern with the KIP-107.
> > At
> > > > this
> > > > > > > point
> > > > > > > > > we would like to start the voting process. The KIP can be
> > found
> > > > at
> > > > > > > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-107
> > > > > > > > > %3A+Add+purgeDataBefore%28%29+API+in+AdminClient.
> > > > > > > > >
> > > > > > > > > Thanks,
> > > > > > > > > Dong
> > > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
> >
> >
> > --
> > -- Guozhang
> >
>
--
-- Guozhang
