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From Becket Qin <becket....@gmail.com>
Subject Re: [VOTE] KIP-32 Add CreateTime and LogAppendTime to Kafka message.
Date Wed, 06 Jan 2016 15:01:43 GMT
Thanks a lot for the careful reading, Jun.
Please see inline replies.


> On Jan 6, 2016, at 3:24 AM, Jun Rao <jun@confluent.io> wrote:
> 
> Jiangjie,
> 
> Thanks for the updated KIP. Overall, a +1 on the proposal. A few minor
> comments on the KIP.
> 
> KIP-32:
> 50. 6.c says "The log rolling has to depend on the earliest timestamp",
> which is inconsistent with KIP-33.
Corrected.
> 
> 51. 8.b "If the time difference threshold is set to 0. The timestamp in the
> message is equivalent to LogAppendTime." If the time difference is 0 and
> CreateTime is used, all messages will likely be rejected in this proposal.
> So, it's not equivalent to LogAppendTime.
Corrected.
> 
> 52. Could you include the new value of magic byte in message format change?
> Also, do we have a single new message format that includes both the offset
> change (relative offset for inner messages) and the addition of timestamp?
I am actually thinking about this when I am writing the patch. 
The timestamp will be added to the o.a.k.common.record.Record and Kafka.message.Message. The
offset change is in o.a.k.common.record.MemoryRecords and Kafka.message.MessageSet. To avoid
unnecessary changes, my current patch did not merge them together but simply make sure the
version of  Record(Message) and MemoryRecords(MessageSet) matches.

Currently new clients uses classes in o.a.k.common.record, and the broker and old clients
uses classes in kafka.message. 
I am thinking about doing the followings: 
1. Migrate broker to use o.a.k.common.record. 
2. Add message format V0 and V1 to o.a.k.common.protocol.Protocols. Ideally we should be able
to define all the wire protocols in o.a.k.common.protocol.Protocol. So instead of having Record
class to parse byte arrays by itself, we can use Schema to parse the records.

Would that be better?
> 
> 53. Could you document the changes in ProducerRequest V2 and FetchRequest
> V2 (and the responses)?
Done.
> 
> 54. In migration phase 1, step 2, does internal ApiVersion mean
> inter.broker.protocol.version?
Yes.
> 
> 55. In canary step 2.b, it says "It will only see
> ProduceRequest/FetchRequest V1 from other brokers and clietns.". But in
> phase 2, a broker will receive FetchRequest V2 from other brokers.
I meant when we canary a broker in phase 2, there will be only one broker entering phase 2,
the other brokers will remain at phase 1.
> 
> 
> KIP-33:
> 60. The KIP still says maintaining index at "at minute granularity" even
> though the index interval is configurable now.
Corrected.
> 
> 61. In this design, it's possible for a log segment to have an empty time
> index. In the worse case, we may have to scan more than the active segment
> to recover the latest timestamp.
Corrected.
> 
> Thanks,
> 
> Jun
> 
> On Mon, Jan 4, 2016 at 11:37 AM, Aditya Auradkar <
> aauradkar@linkedin.com.invalid> wrote:
> 
>> Hey Becket/Anna -
>> 
>> I have a few comments about the KIP.
>> 
>> 1. (Minor) Can we rename the KIP? It's currently "Add CreateTime and
>> LogAppendTime etc..". This is actually the title of the now rejected Option
>> 1.
>> 2. (Minor) Can we rename the proposed option? It isn't really "option 4"
>> anymore.
>> 3. I'm not clear on what exactly happens to compressed messages
>> when message.timestamp.type=LogAppendTime? Does every batch get
>> recompressed because the inner message gets rewritten with the server
>> timestamp? Or does the message set on disk have the timestamp set to -1. In
>> that case, what do we use as timestamp for the message?
>> 4. Do message.timestamp.type and max.message.time.difference.ms need to be
>> per-topic configs? It seems that this is really a client config i.e. a
>> client is the source of timestamps not a topic. It could also be a
>> broker-level config to keep things simple.
>> 5. The "Proposed Changes" section in the KIP tries to build a time-based
>> index for query but that is a separate proposal (KIP-33). Can we more
>> crisply identify what exactly will change when this KIP (and 31) is
>> implemented? It isn't super clear to me at this point.
>> 
>> Aside from that, I think the "Rejected Alternatives" section of the KIP is
>> excellent. Very good insight into what options were discussed and rejected.
>> 
>> Aditya
>> 
>>> On Mon, Dec 28, 2015 at 3:57 PM, Becket Qin <becket.qin@gmail.com> wrote:
>>> 
>>> Thanks Guozhang, Gwen and Neha for the comments. Sorry for late reply
>>> because I only have occasional gmail access from my phone...
>>> 
>>> I just updated the wiki for KIP-32.
>>> 
>>> Gwen,
>>> 
>>> Yes, the migration plan is what you described.
>>> 
>>> I agree with your comments on the version.
>>> I changed message.format.version to use the release version.
>>> I did not change the internal version, we can discuss this in a separate
>>> thread.
>>> 
>>> Thanks,
>>> 
>>> Jiangjie (Becket) Qin
>>> 
>>> 
>>> 
>>>> On Dec 24, 2015, at 5:38 AM, Guozhang Wang <wangguoz@gmail.com> wrote:
>>>> 
>>>> Also I agree with Gwen that such changes may worth a 0.10 release or
>> even
>>>> 1.0, having it in 0.9.1 would be quite confusing to users.
>>>> 
>>>> Guozhang
>>>> 
>>>>> On Wed, Dec 23, 2015 at 1:36 PM, Guozhang Wang <wangguoz@gmail.com>
>>> wrote:
>>>>> 
>>>>> Becket,
>>>>> 
>>>>> Please let us know once you have updated the wiki page regarding the
>>>>> migration plan. Thanks!
>>>>> 
>>>>> Guozhang
>>>>> 
>>>>>> On Wed, Dec 23, 2015 at 11:52 AM, Gwen Shapira <gwen@confluent.io>
>>> wrote:
>>>>>> 
>>>>>> Thanks Becket, Anne and Neha for responding to my concern.
>>>>>> 
>>>>>> I had an offline discussion with Anne where she helped me understand
>>> the
>>>>>> migration process. It isn't as bad as it looks in the KIP :)
>>>>>> 
>>>>>> If I understand it correctly, the process (for users) will be:
>>>>>> 
>>>>>> 1. Prepare for upgrade (set format.version = 0, ApiVersion = 0.9.0)
>>>>>> 2. Rolling upgrade of brokers
>>>>>> 3. Bump ApiVersion to 0.9.0-1, so fetch requests between brokers
will
>>> use
>>>>>> the new protocol
>>>>>> 4. Start upgrading clients
>>>>>> 5. When "enough" clients are upgraded, bump format.version to 1
>>> (rolling).
>>>>>> 
>>>>>> Becket, can you confirm?
>>>>>> 
>>>>>> Assuming this is the process, I'm +1 on the change.
>>>>>> 
>>>>>> Reminder to coders and reviewers that pull-requests with user-facing
>>>>>> changes should include documentation changes as well as code changes.
>>>>>> And a polite request to try to be helpful to users on when to use
>>>>>> create-time and when to use log-append-time as configuration - this
>> is
>>> not
>>>>>> a trivial decision.
>>>>>> 
>>>>>> A separate point I'm going to raise in a different thread is that
we
>>> need
>>>>>> to streamline our versions a bit:
>>>>>> 1. I'm afraid that 0.9.0-1 will be confusing to users who care about
>>>>>> released versions (what if we forget to change it before the release?
>>> Is
>>>>>> it
>>>>>> meaningful enough to someone running off trunk?), we need to come
up
>>> with
>>>>>> something that will work for both LinkedIn and everyone else.
>>>>>> 2. ApiVersion has real version numbers. message.format.version has
>>>>>> sequence
>>>>>> numbers. This makes us look pretty silly :)
>>>>>> 
>>>>>> My version concerns can be addressed separately and should not hold
>>> back
>>>>>> this KIP.
>>>>>> 
>>>>>> Gwen
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> On Tue, Dec 22, 2015 at 11:01 PM, Becket Qin <becket.qin@gmail.com>
>>>>>> wrote:
>>>>>> 
>>>>>>> Hi Anna,
>>>>>>> 
>>>>>>> Thanks for initiating the voting process. I did not start the
voting
>>>>>>> process because there were still some ongoing discussion with
Jun
>>> about
>>>>>> the
>>>>>>> timestamp regarding compressed messages. That is why the wiki
page
>>>>>> hasn't
>>>>>>> reflected the latest conversation as Guozhang pointed out.
>>>>>>> 
>>>>>>> Like Neha said I think we have reached general agreement on this
>> KIP.
>>> So
>>>>>>> it is probably fine to start the KIP voting. At least we draw
more
>>>>>>> attention to the KIP even if there are some new discussion to
bring
>>> up.
>>>>>>> 
>>>>>>> Regarding the upgrade plan, given we decided to implement KIP-31
and
>>>>>>> KIP-32 in the same patch to avoid change binary protocol twice,
the
>>>>>> upgrade
>>>>>>> plan was mostly discussed on the discussion thread of KIP-31.
>>>>>>> 
>>>>>>> Since the voting has been initiated, I will update the wiki with
>>> latest
>>>>>>> conversation to avoid further confusion.
>>>>>>> 
>>>>>>> BTW, I actually have started coding work on KIP-31 and KIP-32
and
>> will
>>>>>>> focus on the patch before I return from vacation in mid Jan because
>> I
>>>>>> have
>>>>>>> no LInkedIn VPN access in China anyway...
>>>>>>> 
>>>>>>> Thanks,
>>>>>>> 
>>>>>>> Jiangjie
>>>>>>> 
>>>>>>>> On Dec 23, 2015, at 12:31 PM, Anna Povzner <anna@confluent.io>
>>> wrote:
>>>>>>>> 
>>>>>>>> Hi Gwen,
>>>>>>>> 
>>>>>>>> I just wanted to point out that I just started the vote.
Becket
>> wrote
>>>>>> the
>>>>>>>> proposal and led the discussions.
>>>>>>>> 
>>>>>>>> What I understood from reading the discussion thread, the
migration
>>>>>> plan
>>>>>>>> was discussed at the KIP meeting, and not much on the mailing
list
>>>>>>> itself.
>>>>>>>> 
>>>>>>>> My question about the migration plan was same as Guozhang
wrote:
>> The
>>>>>> case
>>>>>>>> when an upgraded broker receives an old producer request.
The
>>>>>> proposal is
>>>>>>>> for the broker to fill in the timestamp field with the current
time
>>> at
>>>>>>> the
>>>>>>>> broker. Cons: it goes against the definition of CreateTime
type of
>>> the
>>>>>>>> timestamp (we are "over-writing" it at the broker). Pros:
It looks
>>>>>> like
>>>>>>>> most of the use-cases would actually want that behavior,
because
>>>>>>> otherwise
>>>>>>>> timestamp is useless and they will need to support an old,
>>>>>> pre-timestamp,
>>>>>>>> behavior. E.g., if we modify log retention policy to use
the
>>>>>> timestamp,
>>>>>>> we
>>>>>>>> would need to support an old implementation (the one that
does not
>>> use
>>>>>>>> timestamps in the message). So I actually have a preference
for the
>>>>>>>> proposed approach.
>>>>>>>> 
>>>>>>>> Thanks,
>>>>>>>> Anna
>>>>>>>> 
>>>>>>>>> On Tue, Dec 22, 2015 at 8:02 PM, Neha Narkhede <neha@confluent.io
>>> 
>>>>>>> wrote:
>>>>>>>>> 
>>>>>>>>> Hey Gwen,
>>>>>>>>> 
>>>>>>>>> Migration plan wasn't really discussed a ton in the previous
>>> threads.
>>>>>>> So it
>>>>>>>>> will be great to dive deep and see if there are gaps
there. I had
>>>>>> some
>>>>>>>>> questions, but the details listed on the KIP are great.
>>>>>>>>> 
>>>>>>>>> It is complex, though the plan outlined in the wiki assumes
a zero
>>>>>>> downtime
>>>>>>>>> upgrade assuming that producers and consumers can't be
upgraded in
>>>>>>> tandem.
>>>>>>>>> This is typical for companies that have a significant
Kafka
>>>>>> footprint,
>>>>>>> like
>>>>>>>>> LinkedIn.
>>>>>>>>> 
>>>>>>>>> Thanks,
>>>>>>>>> Neha
>>>>>>>>> 
>>>>>>>>>> On Tue, Dec 22, 2015 at 7:48 PM, Gwen Shapira <gwen@confluent.io
>>> 
>>>>>>> wrote:
>>>>>>>>>> 
>>>>>>>>>> Hi Anna,
>>>>>>>>>> 
>>>>>>>>>> Thanks for the KIP, especially for the details on
all the
>>>>>> alternatives
>>>>>>>>> and
>>>>>>>>>> how we arrived at the proposal. Its really great!
>>>>>>>>>> 
>>>>>>>>>> Can you point me at where the migration plan was
discussed? It
>>> looks
>>>>>>>>> overly
>>>>>>>>>> complex and I have a bunch of questions, but if there
was a
>>>>>> discussion,
>>>>>>>>> I'd
>>>>>>>>>> like to read up rather than repeating it :)
>>>>>>>>>> 
>>>>>>>>>> Gwen
>>>>>>>>>> 
>>>>>>>>>>> On Tue, Dec 22, 2015 at 12:34 PM, Anna Povzner
<
>> anna@confluent.io
>>>> 
>>>>>>>>>> wrote:
>>>>>>>>>> 
>>>>>>>>>>> Hi,
>>>>>>>>>>> 
>>>>>>>>>>> I am opening the voting thread for KIP-32: Add
CreateTime and
>>>>>>>>>>> LogAppendTime to Kafka message.
>>>>>>>>>>> 
>>>>>>>>>>> For reference, here's the KIP wiki:
>> https://cwiki.apache.org/confluence/display/KAFKA/KIP-32+-+Add+CreateTime+and+LogAppendTime+to+Kafka+message
>>>>>>>>>>> 
>>>>>>>>>>> And the mailing list threads:
>>>>>>>>>>> 
>>>>>>>>>>> September:
>> http://mail-archives.apache.org/mod_mbox/kafka-dev/201509.mbox/%3CCAHrRUm6NMg%3DPh4HAJdxr%3DpmZhfFcD5OEV2yxj3fg%2BXnEBTW%2B3w%40mail.gmail.com%3E
>>>>>>>>>>> 
>>>>>>>>>>> October:
>> http://mail-archives.apache.org/mod_mbox/kafka-dev/201510.mbox/%3CCAHrRUm7RiBAJxwO15s1tztz%3D15oibO-QJ%2B_w8AxafTnuw3jjCw%40mail.gmail.com%3E
>>>>>>>>>>> 
>>>>>>>>>>> December:
>> http://mail-archives.apache.org/mod_mbox/kafka-dev/201512.mbox/%3CCAHrRUm4ugxDYzyy26MGRGKpK4hsjT4EKTuu18M3wztYq4PE%3DaQ%40mail.gmail.com%3E
>>>>>>>>>>> 
>>>>>>>>>>> 
>>>>>>>>>>> Thanks
>>>>>>>>>>> Anna
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> --
>>>>>>>>> Thanks,
>>>>>>>>> Neha
>>>>> 
>>>>> 
>>>>> 
>>>>> --
>>>>> -- Guozhang
>>>> 
>>>> 
>>>> 
>>>> --
>>>> -- Guozhang
>> 

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