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From Brett Rann <br...@zendesk.com.INVALID>
Subject Re: [DISCUSS] KIP-354 Time-based log compaction policy
Date Thu, 16 Aug 2018 00:33:38 GMT
We've been looking into this too.

Mailing list:
https://lists.apache.org/thread.html/ed7f6a6589f94e8c2a705553f364ef599cb6915e4c3ba9b561e610e4@%3Cdev.kafka.apache.org%3E
jira wish: https://issues.apache.org/jira/browse/KAFKA-7137
confluent slack discussion:
https://confluentcommunity.slack.com/archives/C49R61XMM/p1530760121000039

A person on my team has started on code so you might want to coordinate:
https://github.com/dongxiaohe/kafka/tree/dongxiaohe/log-cleaner-compaction-max-lifetime-2.0

 He's been working with Jason Gustafson and James Chen around the changes.
You can ping him on confluent slack as Xiaohe Dong.

It's great to know others are thinking on it as well.

You've added the requirement to force a segment roll which we hadn't gotten
to yet, which is great. I was content with it not including the active
segment.

> Adding topic level configuration "max.compaction.lag.ms",  and
corresponding broker configuration "log.cleaner.max.compaction.lag.ms",
which is set to 0 (disabled) by default.

Glancing at some other settings convention seems to me to be -1 for
disabled (or infinite, which is more meaningful here).  0 to me implies
instant, a little quicker than 1.

We've been trying to think about a way to trigger compaction as well
through an API call, which would need to be flagged somewhere (ZK admin/
space?) but we're struggling to think how that would be coordinated across
brokers and partitions.  Have you given any thought to that?






On Thu, Aug 16, 2018 at 8:44 AM xiongqi wu <xiongqiwu@gmail.com> wrote:

> Eno, Dong,
>
> I have updated the KIP. We decide not to address the issue that we might
> have for both compaction and time retention enabled topics (see the
> rejected alternative item 2). This KIP will only ensure log can be
> compacted after a specified time-interval.
>
> As suggested by Dong, we will also enforce "max.compaction.lag.ms" is not
> less than "min.compaction.lag.ms".
>
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-354: Time-based log
> compaction policy
> <https://cwiki.apache.org/confluence/display/KAFKA/KIP-354: Time-based log compaction
policy>
>
>
> On Tue, Aug 14, 2018 at 5:01 PM, xiongqi wu <xiongqiwu@gmail.com> wrote:
>
> >
> > Per discussion with Dong, he made a very good point that if compaction
> > and time based retention are both enabled on a topic, the compaction
> might
> > prevent records from being deleted on time. The reason is when compacting
> > multiple segments into one single segment, the newly created segment will
> > have same lastmodified timestamp as latest original segment. We lose the
> > timestamp of all original segments except the last one. As a result,
> > records might not be deleted as it should be through time based
> retention.
> >
> > With the current KIP proposal, if we want to ensure timely deletion, we
> > have the following configurations:
> > 1) enable time based log compaction only : deletion is done though
> > overriding the same key
> > 2) enable time based log retention only: deletion is done though
> > time-based retention
> > 3) enable both log compaction and time based retention: Deletion is not
> > guaranteed.
> >
> > Not sure if we have use case 3 and also want deletion to happen on time.
> > There are several options to address deletion issue when enable both
> > compaction and retention:
> > A) During log compaction, looking into record timestamp to delete expired
> > records. This can be done in compaction logic itself or use
> > AdminClient.deleteRecords() . But this assumes we have record timestamp.
> > B) retain the lastModifed time of original segments during log
> compaction.
> > This requires extra meta data to record the information or not grouping
> > multiple segments into one during compaction.
> >
> > If we have use case 3 in general, I would prefer solution A and rely on
> > record timestamp.
> >
> >
> > Two questions:
> > Do we have use case 3? Is it nice to have or must have?
> > If we have use case 3 and want to go with solution A, should we introduce
> > a new configuration to enforce deletion by timestamp?
> >
> >
> > On Tue, Aug 14, 2018 at 1:52 PM, xiongqi wu <xiongqiwu@gmail.com> wrote:
> >
> >> Dong,
> >>
> >> Thanks for the comment.
> >>
> >> There are two retention policy: log compaction and time based retention.
> >>
> >> Log compaction:
> >>
> >> we have use cases to keep infinite retention of a topic (only
> >> compaction). GDPR cares about deletion of PII (personal identifiable
> >> information) data.
> >> Since Kafka doesn't know what records contain PII, it relies on upper
> >> layer to delete those records.
> >> For those infinite retention uses uses, kafka needs to provide a way to
> >> enforce compaction on time. This is what we try to address in this KIP.
> >>
> >> Time based retention,
> >>
> >> There are also use cases that users of Kafka might want to expire all
> >> their data.
> >> In those cases, they can use time based retention of their topics.
> >>
> >>
> >> Regarding your first question, if a user wants to delete a key in the
> >> log compaction topic, the user has to send a deletion using the same
> key.
> >> Kafka only makes sure the deletion will happen under a certain time
> >> periods (like 2 days/7 days).
> >>
> >> Regarding your second question. In most cases, we might want to delete
> >> all duplicated keys at the same time.
> >> Compaction might be more efficient since we need to scan the log and
> find
> >> all duplicates. However, the expected use case is to set the time based
> >> compaction interval on the order of days, and be larger than 'min
> >> compaction lag". We don't want log compaction to happen frequently since
> >> it is expensive. The purpose is to help low production rate topic to get
> >> compacted on time. For the topic with "normal" incoming message message
> >> rate, the "min dirty ratio" might have triggered the compaction before
> this
> >> time based compaction policy takes effect.
> >>
> >>
> >> Eno,
> >>
> >> For your question, like I mentioned we have long time retention use case
> >> for log compacted topic, but we want to provide ability to delete
> certain
> >> PII records on time.
> >> Kafka itself doesn't know whether a record contains sensitive
> information
> >> and relies on the user for deletion.
> >>
> >>
> >> On Mon, Aug 13, 2018 at 6:58 PM, Dong Lin <lindong28@gmail.com> wrote:
> >>
> >>> Hey Xiongqi,
> >>>
> >>> Thanks for the KIP. I have two questions regarding the use-case for
> >>> meeting
> >>> GDPR requirement.
> >>>
> >>> 1) If I recall correctly, one of the GDPR requirement is that we can
> not
> >>> keep messages longer than e.g. 30 days in storage (e.g. Kafka). Say
> there
> >>> exists a partition p0 which contains message1 with key1 and message2
> with
> >>> key2. And then user keeps producing messages with key=key2 to this
> >>> partition. Since message1 with key1 is never overridden, sooner or
> later
> >>> we
> >>> will want to delete message1 and keep the latest message with key=key2.
> >>> But
> >>> currently it looks like log compact logic in Kafka will always put
> these
> >>> messages in the same segment. Will this be an issue?
> >>>
> >>> 2) The current KIP intends to provide the capability to delete a given
> >>> message in log compacted topic. Does such use-case also require Kafka
> to
> >>> keep the messages produced before the given message? If yes, then we
> can
> >>> probably just use AdminClient.deleteRecords() or time-based log
> retention
> >>> to meet the use-case requirement. If no, do you know what is the GDPR's
> >>> requirement on time-to-deletion after user explicitly requests the
> >>> deletion
> >>> (e.g. 1 hour, 1 day, 7 day)?
> >>>
> >>> Thanks,
> >>> Dong
> >>>
> >>>
> >>> On Mon, Aug 13, 2018 at 3:44 PM, xiongqi wu <xiongqiwu@gmail.com>
> wrote:
> >>>
> >>> > Hi Eno,
> >>> >
> >>> > The GDPR request we are getting here at linkedin is if we get a
> >>> request to
> >>> > delete a record through a null key on a log compacted topic,
> >>> > we want to delete the record via compaction in a given time period
> >>> like 2
> >>> > days (whatever is required by the policy).
> >>> >
> >>> > There might be other issues (such as orphan log segments under
> certain
> >>> > conditions) that lead to GDPR problem but they are more like
> >>> something we
> >>> > need to fix anyway regardless of GDPR.
> >>> >
> >>> >
> >>> > -- Xiongqi (Wesley) Wu
> >>> >
> >>> > On Mon, Aug 13, 2018 at 2:56 PM, Eno Thereska <
> eno.thereska@gmail.com>
> >>> > wrote:
> >>> >
> >>> > > Hello,
> >>> > >
> >>> > > Thanks for the KIP. I'd like to see a more precise definition
of
> what
> >>> > part
> >>> > > of GDPR you are targeting as well as some sort of verification
that
> >>> this
> >>> > > KIP actually addresses the problem. Right now I find this a bit
> >>> vague:
> >>> > >
> >>> > > "Ability to delete a log message through compaction in a timely
> >>> manner
> >>> > has
> >>> > > become an important requirement in some use cases (e.g., GDPR)"
> >>> > >
> >>> > >
> >>> > > Is there any guarantee that after this KIP the GDPR problem is
> >>> solved or
> >>> > do
> >>> > > we need to do something else as well, e.g., more KIPs?
> >>> > >
> >>> > >
> >>> > > Thanks
> >>> > >
> >>> > > Eno
> >>> > >
> >>> > >
> >>> > >
> >>> > > On Thu, Aug 9, 2018 at 4:18 PM, xiongqi wu <xiongqiwu@gmail.com>
> >>> wrote:
> >>> > >
> >>> > > > Hi Kafka,
> >>> > > >
> >>> > > > This KIP tries to address GDPR concern to fulfill deletion
> request
> >>> on
> >>> > > time
> >>> > > > through time-based log compaction on a compaction enabled
topic:
> >>> > > >
> >>> > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-
> <https://cwiki.apache.org/confluence/display/KAFKA/KIP->
> >>> > > > 354%3A+Time-based+log+compaction+policy
> >>> > > >
> >>> > > > Any feedback will be appreciated.
> >>> > > >
> >>> > > >
> >>> > > > Xiongqi (Wesley) Wu
> >>> > > >
> >>> > >
> >>> >
> >>>
> >>
> >>
> >>
> >> --
> >> Xiongqi (Wesley) Wu
> >>
> >
> >
> >
> > --
> > Xiongqi (Wesley) Wu
> >
>
>
>
> --
> Xiongqi (Wesley) Wu
>


-- 

Brett Rann

Senior DevOps Engineer


Zendesk International Ltd

395 Collins Street, Melbourne VIC 3000 Australia

Mobile: +61 (0) 418 826 017

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