Jason,
> I think we would only use this error code when we /know/ that zstd was in
use and the client doesn't support it? This is true if either 1) the
message needs down-conversion and we encounter a zstd compressed message,
or 2) if the topic is explicitly configured to use zstd.
Yes, it is right. And you know, the case 1 includes 1.a) old clients'
request v0, v1 records or 1.b) implicit zstd, the compression type of
"producer" with Zstd compressed data.
> However, if the compression type is set to "producer," then the fetched
data may or may not be compressed with zstd. In this case, we return the
data to the client and expect it to fail parsing. Is that correct?
Exactly.
Following your message, I reviewed the implementation of
`KafkaApis#handleFetchRequest,` which handles the fetch request. And found
that the information we can use is like the following:
1. Client's fetch request version. (`versionId` variable)
2. Log's compression type. (`logConfig` variable)
We can't detect the actual compression type of the data, unless we inspect
the `RecordBatch` included in the `Records` instance (i.e.,
`unconvertedRecords` variable.) Since it requires some performance issue,
it is not our option - in short, we can't be sure if given chunks of data
are compressed with zstd or not.
So, conclusion: we can return an error in the case of 1.a and 2 easily,
with the information above. In the case 1.b (implicit zstd), we can just
return the data by do nothing special and expect it to fail parsing.
Thanks,
Dongjin
On Wed, Aug 22, 2018 at 12:02 PM Ismael Juma <isma...@gmail.com> wrote:
> Jason, that's an interesting point regarding the Java client. Do we know
> what clients in other languages do in these cases?
>
> Ismael
>
> On Tue, 21 Aug 2018, 17:30 Jason Gustafson, <ja...@confluent.io> wrote:
>
> > Hi Dongjin,
> >
> > One of the complications is that old versions of the API will not expect
> a
> > new error code. However, since we expect this to be a fatal error anyway
> > for old clients, it may still be more useful to return the correct error
> > code. For example, the Kafka clients use the following code to convert
> the
> > error code:
> >
> > public static Errors forCode(short code) {
> > Errors error = codeToError.get(code);
> > if (error != null) {
> > return error;
> > } else {
> > log.warn("Unexpected error code: {}.", code);
> > return UNKNOWN_SERVER_ERROR;
> > }
> > }
> >
> > If we return an unsupported error code, it will be converted to an
> UNKNOWN
> > error, but at least we will get the message in the log with the correct
> > code. That seems preferable to returning a misleading error code. So I
> > wonder if we can use the new UNSUPPORTED_COMPRESSION_TYPE error even for
> > older versions.
> >
> > Also, one question just to check my understanding. I think we would only
> > use this error code when we /know/ that zstd was in use and the client
> > doesn't support it? This is true if either 1) the message needs
> > down-conversion and we encounter a zstd compressed message, or 2) if the
> > topic is explicitly configured to use zstd. However, if the compression
> > type is set to "producer," then the fetched data may or may not be
> > compressed with zstd. In this case, we return the data to the client and
> > expect it to fail parsing. Is that correct?
> >
> > Thanks,
> > Jason
> >
> >
> >
> > On Tue, Aug 21, 2018 at 9:08 AM, Dongjin Lee <dong...@apache.org> wrote:
> >
> > > Ismael, Jason and all,
> > >
> > > I rewrote the backward compatibility strategy & its alternatives like
> > > following, based on Ismael & Jason's comments. Since it is not updated
> to
> > > the wiki yet, don't hesitate to give me a message if you have any
> opinion
> > > on it.
> > >
> > > ```
> > > *Backward Compatibility*
> > >
> > > We need to establish some backward-compatibility strategy for the case
> an
> > > old client subscribes a topic using ZStandard implicitly (i.e.,
> > > 'compression.type' configuration of given topic is 'producer' and the
> > > producer compressed the records with ZStandard). We have the following
> > > options for this situation:
> > >
> > > *A. Support ZStandard to the old clients which can understand v0, v1
> > > messages only.*
> > >
> > > This strategy necessarily requires the down-conversion of v2 message
> > > compressed with Zstandard into v0 or v1 messages, which means a
> > > considerable performance degradation. So we rejected this strategy.
> > >
> > > *B. Bump the API version and support only v2-available clients*
> > >
> > > With this approach, we can message the old clients that they are old
> and
> > > should be upgraded. However, there are still several options for the
> > Error
> > > code.
> > >
> > > *B.1. INVALID_REQUEST (42)*
> > >
> > > This option gives the client so little information; the user can be
> > > confused about why the client worked correctly in the past suddenly
> > > encounters a problem. So we rejected this strategy.
> > >
> > > *B.2. CORRUPT_MESSAGE (2)*
> > >
> > > This option gives inaccurate information; the user can be surprised and
> > > misunderstand that the log files are broken in some way. So we rejected
> > > this strategy.
> > >
> > > *B.3 UNSUPPORTED_FOR_MESSAGE_FORMAT (43)*
> > >
> > > The advantage of this approach is we don't need to define a new error
> > code;
> > > we can reuse it and that's all.
> > >
> > > The disadvantage of this approach is that it is also a little bit
> vague;
> > > This error code is defined as a work for KIP-98[^1] and now returned in
> > the
> > > transaction error.
> > >
> > > *B.4. UNSUPPORTED_COMPRESSION_TYPE (new)*
> > >
> > > The advantage of this approach is that it is clear and provides an
> exact
> > > description. The disadvantage is we need to add a new error code.
> > > ```
> > >
> > > *It seems like what we need to choose is now so clear:
> > > UNSUPPORTED_FOR_MESSAGE_FORMAT (B.3) or UNSUPPORTED_COMPRESSION_TYPE
> > > (B.4).*
> > > The first one doesn't need a new error message but the latter is more
> > > explicit. Which one do you prefer? Since all of you have much more
> > > experience and knowledge than me, I will follow your decision. The wiki
> > > page will be updated following the decision also.
> > >
> > > Best,
> > > Dongjin
> > >
> > > [^1]: https://issues.apache.org/jira/browse/KAFKA-4990
> > >
> > > On Sun, Aug 19, 2018 at 4:58 AM Ismael Juma <isma...@gmail.com> wrote:
> > >
> > > > Sounds reasonable to me.
> > > >
> > > > Ismael
> > > >
> > > > On Sat, 18 Aug 2018, 12:20 Jason Gustafson, <ja...@confluent.io>
> > wrote:
> > > >
> > > > > Hey Ismael,
> > > > >
> > > > > Your summary looks good to me. I think it might also be a good idea
> > to
> > > > add
> > > > > a new UNSUPPORTED_COMPRESSION_TYPE error code to go along with the
> > > > version
> > > > > bumps. We won't be able to use it for old api versions since the
> > > clients
> > > > > will not understand it, but we can use it going forward so that
> we're
> > > not
> > > > > stuck in a similar situation with a new message format and a new
> > codec
> > > to
> > > > > support. Another option is to use UNSUPPORTED_FOR_MESSAGE_FORMAT,
> but
> > > it
> > > > is
> > > > > not as explicit.
> > > > >
> > > > > -Jason
> > > > >
> > > > > On Fri, Aug 17, 2018 at 5:19 PM, Ismael Juma <ism...@juma.me.uk>
> > > wrote:
> > > > >
> > > > > > Hi Dongjin and Jason,
> > > > > >
> > > > > > I would agree. My summary:
> > > > > >
> > > > > > 1. Support zstd with message format 2 only.
> > > > > > 2. Bump produce and fetch request versions.
> > > > > > 3. Provide broker errors whenever possible based on the request
> > > version
> > > > > and
> > > > > > rely on clients for the cases where the broker can't validate
> > > > efficiently
> > > > > > (example message format 2 consumer that supports the latest fetch
> > > > version
> > > > > > but doesn't support zstd).
> > > > > >
> > > > > > If there's general agreement on this, I suggest we update the KIP
> > to
> > > > > state
> > > > > > the proposal and to move the rejected options to its own section.
> > And
> > > > > then
> > > > > > start a vote!
> > > > > >
> > > > > > Ismael
> > > > > >
> > > > > > On Fri, Aug 17, 2018 at 4:00 PM Jason Gustafson <
> > ja...@confluent.io>
> > > > > > wrote:
> > > > > >
> > > > > > > Hi Dongjin,
> > > > > > >
> > > > > > > Yes, that's a good summary. For clients which support v2, the
> > > client
> > > > > can
> > > > > > > parse the message format and hopefully raise a useful error
> > message
> > > > > > > indicating the unsupported compression type. For older clients,
> > our
> > > > > > options
> > > > > > > are probably (1) to down-convert to the old format using no
> > > > compression
> > > > > > > type, or (2) to return an error code. I'm leaning toward the
> > latter
> > > > as
> > > > > > the
> > > > > > > simpler solution, but the challenge is finding a good error
> code.
> > > Two
> > > > > > > possibilities might be INVALID_REQUEST or CORRUPT_MESSAGE. The
> > > > downside
> > > > > > is
> > > > > > > that old clients probably won't get a helpful message. However,
> > at
> > > > > least
> > > > > > > the behavior will be consistent in the sense that all clients
> > will
> > > > fail
> > > > > > if
> > > > > > > they do not support zstandard.
> > > > > > >
> > > > > > > What do you think?
> > > > > > >
> > > > > > > Thanks,
> > > > > > > Jason
> > > > > > >
> > > > > > > On Fri, Aug 17, 2018 at 8:08 AM, Dongjin Lee <
> dong...@apache.org
> > >
> > > > > wrote:
> > > > > > >
> > > > > > > > Thanks Jason, I reviewed the down-converting logic following
> > your
> > > > > > > > explanation.[^1] You mean the following routines, right?
> > > > > > > >
> > > > > > > > -
> > > > > > > > https://github.com/apache/kafka/blob/trunk/core/src/
> > > > > > > > main/scala/kafka/server/KafkaApis.scala#L534
> > > > > > > > -
> > > > > > > > https://github.com/apache/kafka/blob/trunk/clients/src/
> > > > > > > > main/java/org/apache/kafka/common/record/
> > > LazyDownConversionRecords.
> > > > > > > > java#L165
> > > > > > > > -
> > > > > > > > https://github.com/apache/kafka/blob/trunk/clients/src/
> > > > > > > > main/java/org/apache/kafka/common/record/RecordsUtil.java#L40
> > > > > > > >
> > > > > > > > It seems like your stance is like following:
> > > > > > > >
> > > > > > > > 1. In principle, Kafka does not change the compression codec
> > when
> > > > > > > > down-converting, since it requires inspecting the fetched
> data,
> > > > which
> > > > > > is
> > > > > > > > expensive.
> > > > > > > > 2. However, there are some cases the fetched data is
> inspected
> > > > > anyway.
> > > > > > In
> > > > > > > > this case, we can provide compression conversion from
> Zstandard
> > > to
> > > > > > > > classical ones[^2].
> > > > > > > >
> > > > > > > > And from what I understand, the cases where the client
> without
> > > > > > ZStandard
> > > > > > > > support receives ZStandard compressed records can be
> organized
> > > into
> > > > > two
> > > > > > > > cases:
> > > > > > > >
> > > > > > > > a. The 'compression.type' configuration of given topic is
> > > > 'producer'
> > > > > > and
> > > > > > > > the producer compressed the records with ZStandard. (that is,
> > > using
> > > > > > > > ZStandard implicitly.)
> > > > > > > > b. The 'compression.type' configuration of given topic is
> > > 'zstd';
> > > > > that
> > > > > > > is,
> > > > > > > > using ZStandard explicitly.
> > > > > > > >
> > > > > > > > As you stated, we don't have to handle the case b specially.
> > So,
> > > It
> > > > > > seems
> > > > > > > > like we can narrow the focus of the problem by joining case 1
> > and
> > > > > case
> > > > > > b
> > > > > > > > like the following:
> > > > > > > >
> > > > > > > > > Given the topic with 'producer' as its 'compression.type'
> > > > > > > configuration,
> > > > > > > > ZStandard compressed records and old client without
> ZStandard,
> > is
> > > > > there
> > > > > > > any
> > > > > > > > case we need to inspect the records and can change the
> > > compression
> > > > > > type?
> > > > > > > If
> > > > > > > > so, can we provide compression type converting?
> > > > > > > >
> > > > > > > > Do I understand correctly?
> > > > > > > >
> > > > > > > > Best,
> > > > > > > > Dongjin
> > > > > > > >
> > > > > > > > [^1]: I'm sorry, I found that I was a little bit
> > misunderstanding
> > > > how
> > > > > > API
> > > > > > > > version works, after reviewing the downconvert logic & the
> > > protocol
> > > > > > > > documentation <https://kafka.apache.org/protocol>.
> > > > > > > > [^2]: None, Gzip, Snappy, Lz4.
> > > > > > > >
> > > > > > > > On Tue, Aug 14, 2018 at 2:16 AM Jason Gustafson <
> > > > ja...@confluent.io>
> > > > > > > > wrote:
> > > > > > > >
> > > > > > > > > >
> > > > > > > > > > But in my opinion, since the client will fail with the
> API
> > > > > version,
> > > > > > > so
> > > > > > > > we
> > > > > > > > > > don't need to down-convert the messages anyway. Isn't it?
> > > So, I
> > > > > > think
> > > > > > > > we
> > > > > > > > > > don't care about this case. (I'm sorry, I am not familiar
> > > with
> > > > > > > > > down-convert
> > > > > > > > > > logic.)
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > Currently the broker down-converts automatically when it
> > > receives
> > > > > an
> > > > > > > old
> > > > > > > > > version of the fetch request (a version which is known to
> > > predate
> > > > > the
> > > > > > > > > message format in use). Typically when down-converting the
> > > > message
> > > > > > > > format,
> > > > > > > > > we use the same compression type, but there is not much
> point
> > > in
> > > > > > doing
> > > > > > > so
> > > > > > > > > when we know the client doesn't support it. So if zstandard
> > is
> > > in
> > > > > > use,
> > > > > > > > and
> > > > > > > > > we have to down-convert anyway, then we can choose to use a
> > > > > different
> > > > > > > > > compression type or no compression type.
> > > > > > > > >
> > > > > > > > > From my perspective, there is no significant downside to
> > > bumping
> > > > > the
> > > > > > > > > protocol version and it has several potential benefits.
> > Version
> > > > > bumps
> > > > > > > are
> > > > > > > > > cheap. The main question mark in my mind is about
> > > > down-conversion.
> > > > > > > > Figuring
> > > > > > > > > out whether down-conversion is needed is hard generally
> > without
> > > > > > > > inspecting
> > > > > > > > > the fetched data, which is expensive. I think we agree in
> > > > principle
> > > > > > > that
> > > > > > > > we
> > > > > > > > > do not want to have to pay this cost generally and prefer
> the
> > > > > clients
> > > > > > > to
> > > > > > > > > fail when they see an unhandled compression type. The
> point I
> > > was
> > > > > > > making
> > > > > > > > is
> > > > > > > > > that there are some cases where we are either inspecting
> the
> > > data
> > > > > > > anyway
> > > > > > > > > (because we have to down-convert the message format), or we
> > > have
> > > > an
> > > > > > > easy
> > > > > > > > > way to tell whether zstandard is in use (the topic has it
> > > > > configured
> > > > > > > > > explicitly). In the latter case, we don't have to handle it
> > > > > > specially.
> > > > > > > > But
> > > > > > > > > we do have to decide how we will handle down-conversion to
> > > older
> > > > > > > formats.
> > > > > > > > >
> > > > > > > > > -Jason
> > > > > > > > >
> > > > > > > > > On Sun, Aug 12, 2018 at 5:15 PM, Dongjin Lee <
> > > dong...@apache.org
> > > > >
> > > > > > > wrote:
> > > > > > > > >
> > > > > > > > > > Colin and Jason,
> > > > > > > > > >
> > > > > > > > > > Thanks for your opinions. In summarizing, the Pros and
> Cons
> > > of
> > > > > > > bumping
> > > > > > > > > > fetch API version are:
> > > > > > > > > >
> > > > > > > > > > Cons:
> > > > > > > > > >
> > > > > > > > > > - The Broker can't know whether a given message batch is
> > > > > compressed
> > > > > > > > with
> > > > > > > > > > zstd or not.
> > > > > > > > > > - Need some additional logic for the topic explicitly
> > > > configured
> > > > > to
> > > > > > > use
> > > > > > > > > > zstd.
> > > > > > > > > >
> > > > > > > > > > Pros:
> > > > > > > > > >
> > > > > > > > > > - The broker doesn't need to conduct expensive
> > > down-conversion.
> > > > > > > > > > - Can message the users to update their client.
> > > > > > > > > >
> > > > > > > > > > So, opinions for the backward-compatibility policy by
> far:
> > > > > > > > > >
> > > > > > > > > > - A: bump the API version - +2 (Colin, Jason)
> > > > > > > > > > - B: leave unchanged - +1 (Viktor)
> > > > > > > > > >
> > > > > > > > > > Here are my additional comments:
> > > > > > > > > >
> > > > > > > > > > @Colin
> > > > > > > > > >
> > > > > > > > > > I greatly appreciate your response. In the case of the
> > > > dictionary
> > > > > > > > > support,
> > > > > > > > > > of course, this issue should be addressed later so we
> don't
> > > > need
> > > > > it
> > > > > > > in
> > > > > > > > > the
> > > > > > > > > > first version. You are right - it is not late to try it
> > after
> > > > > some
> > > > > > > > > > benchmarks. What I mean is, we should keep in mind on
> that
> > > > > > potential
> > > > > > > > > > feature.
> > > > > > > > > >
> > > > > > > > > > @Jason
> > > > > > > > > >
> > > > > > > > > > You wrote,
> > > > > > > > > >
> > > > > > > > > > > Similarly, if we have to down-convert anyway because
> the
> > > > client
> > > > > > > does
> > > > > > > > > not
> > > > > > > > > > understand the message format, then we could also use a
> > > > different
> > > > > > > > > > compression type.
> > > > > > > > > >
> > > > > > > > > > But in my opinion, since the client will fail with the
> API
> > > > > version,
> > > > > > > so
> > > > > > > > we
> > > > > > > > > > don't need to down-convert the messages anyway. Isn't it?
> > > So, I
> > > > > > think
> > > > > > > > we
> > > > > > > > > > don't care about this case. (I'm sorry, I am not familiar
> > > with
> > > > > > > > > down-convert
> > > > > > > > > > logic.)
> > > > > > > > > >
> > > > > > > > > > Please give more opinions. Thanks!
> > > > > > > > > >
> > > > > > > > > > - Dongjin
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > > On Wed, Aug 8, 2018 at 6:41 AM Jason Gustafson <
> > > > > ja...@confluent.io
> > > > > > >
> > > > > > > > > wrote:
> > > > > > > > > >
> > > > > > > > > > > Hey Colin,
> > > > > > > > > > >
> > > > > > > > > > > The problem for the fetch API is that the broker does
> not
> > > > > > generally
> > > > > > > > > know
> > > > > > > > > > if
> > > > > > > > > > > a batch was compressed with zstd unless it parses it. I
> > > think
> > > > > the
> > > > > > > > goal
> > > > > > > > > > here
> > > > > > > > > > > is to avoid the expensive down-conversion that is
> needed
> > to
> > > > > > ensure
> > > > > > > > > > > compatibility because it is only necessary if zstd is
> > > > actually
> > > > > in
> > > > > > > > use.
> > > > > > > > > > But
> > > > > > > > > > > as long as old clients can parse the message format,
> they
> > > > > should
> > > > > > > get
> > > > > > > > a
> > > > > > > > > > > reasonable error if they see an unsupported compression
> > > type
> > > > in
> > > > > > the
> > > > > > > > > > > attributes. Basically the onus is on users to ensure
> that
> > > > their
> > > > > > > > > consumers
> > > > > > > > > > > have been updated prior to using zstd. It seems like a
> > > > > reasonable
> > > > > > > > > > tradeoff
> > > > > > > > > > > to me. There are a couple cases that might be worth
> > > thinking
> > > > > > > through:
> > > > > > > > > > >
> > > > > > > > > > > 1. If a topic is explicitly configured to use zstd,
> then
> > we
> > > > > don't
> > > > > > > > need
> > > > > > > > > to
> > > > > > > > > > > check the fetched data for the compression type to know
> > if
> > > we
> > > > > > need
> > > > > > > > > > > down-conversion. If we did bump the Fetch API version,
> > then
> > > > we
> > > > > > > could
> > > > > > > > > > handle
> > > > > > > > > > > this case by either down-converting using a different
> > > > > compression
> > > > > > > > type
> > > > > > > > > or
> > > > > > > > > > > returning an error.
> > > > > > > > > > > 2. Similarly, if we have to down-convert anyway because
> > the
> > > > > > client
> > > > > > > > does
> > > > > > > > > > not
> > > > > > > > > > > understand the message format, then we could also use a
> > > > > different
> > > > > > > > > > > compression type.
> > > > > > > > > > >
> > > > > > > > > > > For the produce API, I think it's reasonable to bump
> the
> > > api
> > > > > > > version.
> > > > > > > > > > This
> > > > > > > > > > > can be used by clients to check whether a broker
> supports
> > > > zstd.
> > > > > > For
> > > > > > > > > > > example, we might support a list of preferred
> compression
> > > > types
> > > > > > in
> > > > > > > > the
> > > > > > > > > > > producer and we could use the broker to detect which
> > > version
> > > > to
> > > > > > > use.
> > > > > > > > > > >
> > > > > > > > > > > -Jason
> > > > > > > > > > >
> > > > > > > > > > > On Tue, Aug 7, 2018 at 1:32 PM, Colin McCabe <
> > > > > cmcc...@apache.org
> > > > > > >
> > > > > > > > > wrote:
> > > > > > > > > > >
> > > > > > > > > > > > Thanks for bumping this, Dongjin. ZStd is a good
> > > > compression
> > > > > > > codec
> > > > > > > > > > and I
> > > > > > > > > > > > hope we can get this support in soon!
> > > > > > > > > > > >
> > > > > > > > > > > > I would say we can just bump the API version to
> > indicate
> > > > that
> > > > > > > ZStd
> > > > > > > > > > > support
> > > > > > > > > > > > is expected in new clients. We probably need some
> way
> > of
> > > > > > > > indicating
> > > > > > > > > to
> > > > > > > > > > > the
> > > > > > > > > > > > older clients that they can't consume the partitions,
> > as
> > > > > well.
> > > > > > > > > Perhaps
> > > > > > > > > > > we
> > > > > > > > > > > > can use the UNSUPPORTED_FOR_MESSAGE_FORMAT error?
> > > > > > > > > > > >
> > > > > > > > > > > > The license thing seems straightforward -- it's just
> a
> > > > matter
> > > > > > of
> > > > > > > > > adding
> > > > > > > > > > > > the text to the right files as per ASF guidelines.
> > > > > > > > > > > >
> > > > > > > > > > > > With regard to the dictionary support, do we really
> > need
> > > > that
> > > > > > in
> > > > > > > > the
> > > > > > > > > > > first
> > > > > > > > > > > > version? Hopefully message batches are big enough
> that
> > > > this
> > > > > > > isn't
> > > > > > > > > > > needed.
> > > > > > > > > > > > Some benchmarks might help here.
> > > > > > > > > > > >
> > > > > > > > > > > > best,
> > > > > > > > > > > > Colin
> > > > > > > > > > > >
> > > > > > > > > > > >
> > > > > > > > > > > > On Tue, Aug 7, 2018, at 08:02, Dongjin Lee wrote:
> > > > > > > > > > > > > As Kafka 2.0.0 was released, let's reboot this
> issue,
> > > > > KIP-110
> > > > > > > > > > > > > <https://cwiki.apache.org/
> > > confluence/display/KAFKA/KIP-
> > > > > > > > > > > > 110%3A+Add+Codec+for+ZStandard+Compression>
> > > > > > > > > > > > > .
> > > > > > > > > > > > >
> > > > > > > > > > > > > For newcomers, Here is some summary of the history:
> > > > KIP-110
> > > > > > was
> > > > > > > > > > > > originally
> > > > > > > > > > > > > worked for the issue KAFKA-4514 but, it lacked
> > > benchmark
> > > > > > > results
> > > > > > > > to
> > > > > > > > > > get
> > > > > > > > > > > > the
> > > > > > > > > > > > > agreement of the community. Later, Ivan Babrou and
> > some
> > > > > other
> > > > > > > > users
> > > > > > > > > > who
> > > > > > > > > > > > > adopted the patch provided their excellent
> > performance
> > > > > report
> > > > > > > > which
> > > > > > > > > > is
> > > > > > > > > > > > now
> > > > > > > > > > > > > included in the KIP, but it postponed again because
> > of
> > > > the
> > > > > > > > > community
> > > > > > > > > > > was
> > > > > > > > > > > > > busy for 2.0.0 release. It is why I now reboot this
> > > > issue.
> > > > > > > > > > > > >
> > > > > > > > > > > > > The following is the current status of the feature:
> > You
> > > > can
> > > > > > > check
> > > > > > > > > the
> > > > > > > > > > > > > current draft implementation here
> > > > > > > > > > > > > <https://github.com/apache/kafka/pull/2267>. It is
> > > based
> > > > > on
> > > > > > > zstd
> > > > > > > > > > 1.3.5
> > > > > > > > > > > > and
> > > > > > > > > > > > > periodically rebased onto the latest trunk[^1].
> > > > > > > > > > > > >
> > > > > > > > > > > > > The issues that should be addressed is like
> > following:
> > > > > > > > > > > > >
> > > > > > > > > > > > > *1. Backward Compatibility*
> > > > > > > > > > > > >
> > > > > > > > > > > > > To support old consumers, we need to take a
> strategy
> > to
> > > > > > handle
> > > > > > > > the
> > > > > > > > > > old
> > > > > > > > > > > > > consumers. Current candidates are:
> > > > > > > > > > > > >
> > > > > > > > > > > > > - Bump API version
> > > > > > > > > > > > > - Leave unchanged: let the old clients fail.
> > > > > > > > > > > > > - Improve the error messages:
> > > > > > > > > > > > >
> > > > > > > > > > > > > *2. Dictionary Support*
> > > > > > > > > > > > >
> > > > > > > > > > > > > To support zstd's dictionary feature in the future
> > (if
> > > > > > needed),
> > > > > > > > we
> > > > > > > > > > need
> > > > > > > > > > > > to
> > > > > > > > > > > > > sketch how it should be and leave some room for it.
> > As
> > > of
> > > > > > now,
> > > > > > > > > there
> > > > > > > > > > > has
> > > > > > > > > > > > > been no discussion on this topic yet.
> > > > > > > > > > > > >
> > > > > > > > > > > > > *3. License*
> > > > > > > > > > > > >
> > > > > > > > > > > > > To use this feature, we need to add license of zstd
> > and
> > > > > > > zstd-jni
> > > > > > > > to
> > > > > > > > > > the
> > > > > > > > > > > > > project. (Thanks to Viktor Somogyi for raising this
> > > > issue!)
> > > > > > It
> > > > > > > > > seems
> > > > > > > > > > > like
> > > > > > > > > > > > > what Apache Spark did would be a good example but
> > there
> > > > has
> > > > > > > been
> > > > > > > > no
> > > > > > > > > > > > > discussion yet.
> > > > > > > > > > > > >
> > > > > > > > > > > > > You can find the details of the above issues in the
> > KIP
> > > > > > > document.
> > > > > > > > > > > Please
> > > > > > > > > > > > > have a look when you are free, and give me
> feedback.
> > > All
> > > > > > kinds
> > > > > > > of
> > > > > > > > > > > > > participating are welcome.
> > > > > > > > > > > > >
> > > > > > > > > > > > > Best,
> > > > > > > > > > > > > Dongjin
> > > > > > > > > > > > >
> > > > > > > > > > > > > [^1]: At the time of writing, commit 6b4fb8152.
> > > > > > > > > > > > >
> > > > > > > > > > > > > On Sat, Jul 14, 2018 at 10:45 PM Dongjin Lee <
> > > > > > > dong...@apache.org
> > > > > > > > >
> > > > > > > > > > > wrote:
> > > > > > > > > > > > >
> > > > > > > > > > > > > > Sorry for the late reply.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > In short, I could not submit the updated KIP by
> the
> > > > > feature
> > > > > > > > > freeze
> > > > > > > > > > > > > > deadline of 2.0.0. For this reason, it will not
> be
> > > > > included
> > > > > > > in
> > > > > > > > > the
> > > > > > > > > > > > 2.0.0
> > > > > > > > > > > > > > release and all discussion for this issue were
> > > > postponed
> > > > > > > after
> > > > > > > > > the
> > > > > > > > > > > > release
> > > > > > > > > > > > > > of 2.0.0.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > I have been updating the PR following recent
> > updates.
> > > > > Just
> > > > > > > > now, I
> > > > > > > > > > > > rebased
> > > > > > > > > > > > > > it against the latest trunk and updated the zstd
> > > > version
> > > > > > into
> > > > > > > > > > 1.3.5.
> > > > > > > > > > > > If you
> > > > > > > > > > > > > > need some request, don't hesitate to notify me.
> > (But
> > > > not
> > > > > > this
> > > > > > > > > > thread
> > > > > > > > > > > -
> > > > > > > > > > > > just
> > > > > > > > > > > > > > send me the message directly.)
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > Best,
> > > > > > > > > > > > > > Dongjin
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > On Tue, Jul 10, 2018 at 11:57 PM Bobby Evans <
> > > > > > > bo...@apache.org
> > > > > > > > >
> > > > > > > > > > > wrote:
> > > > > > > > > > > > > >
> > > > > > > > > > > > > >> I there any update on this. The performance
> > > > > improvements
> > > > > > > are
> > > > > > > > > > quite
> > > > > > > > > > > > > >> impressive and I really would like to stop
> forking
> > > > kafka
> > > > > > > just
> > > > > > > > to
> > > > > > > > > > get
> > > > > > > > > > > > this
> > > > > > > > > > > > > >> in.
> > > > > > > > > > > > > >>
> > > > > > > > > > > > > >> Thanks,
> > > > > > > > > > > > > >>
> > > > > > > > > > > > > >> Bobby
> > > > > > > > > > > > > >>
> > > > > > > > > > > > > >> On Wed, Jun 13, 2018 at 8:56 PM Dongjin Lee <
> > > > > > > > dong...@apache.org
> > > > > > > > > >
> > > > > > > > > > > > wrote:
> > > > > > > > > > > > > >>
> > > > > > > > > > > > > >> > Ismael,
> > > > > > > > > > > > > >> >
> > > > > > > > > > > > > >> > Oh, I forgot all of you are on working frenzy
> > for
> > > > 2.0!
> > > > > > No
> > > > > > > > > > problem,
> > > > > > > > > > > > take
> > > > > > > > > > > > > >> > your time. I am also working at another issue
> > now.
> > > > > Thank
> > > > > > > you
> > > > > > > > > for
> > > > > > > > > > > > > >> letting me
> > > > > > > > > > > > > >> > know.
> > > > > > > > > > > > > >> >
> > > > > > > > > > > > > >> > Best,
> > > > > > > > > > > > > >> > Dongjin
> > > > > > > > > > > > > >> >
> > > > > > > > > > > > > >> > On Wed, Jun 13, 2018, 11:44 PM Ismael Juma <
> > > > > > > > isma...@gmail.com
> > > > > > > > > >
> > > > > > > > > > > > wrote:
> > > > > > > > > > > > > >> >
> > > > > > > > > > > > > >> > > Sorry for the delay Dongjin. Everyone is
> busy
> > > > > > finalising
> > > > > > > > > > 2.0.0.
> > > > > > > > > > > > This
> > > > > > > > > > > > > >> KIP
> > > > > > > > > > > > > >> > > seems like a great candidate for 2.1.0 and
> > > > hopefully
> > > > > > > there
> > > > > > > > > > will
> > > > > > > > > > > be
> > > > > > > > > > > > > >> more
> > > > > > > > > > > > > >> > of
> > > > > > > > > > > > > >> > > a discussion next week. :)
> > > > > > > > > > > > > >> > >
> > > > > > > > > > > > > >> > > Ismael
> > > > > > > > > > > > > >> > >
> > > > > > > > > > > > > >> > > On Wed, 13 Jun 2018, 05:17 Dongjin Lee, <
> > > > > > > > dong...@apache.org
> > > > > > > > > >
> > > > > > > > > > > > wrote:
> > > > > > > > > > > > > >> > >
> > > > > > > > > > > > > >> > > > Hello. I just updated my draft
> > implementation:
> > > > > > > > > > > > > >> > > >
> > > > > > > > > > > > > >> > > > 1. Rebased to latest trunk (commit
> 5145d6b)
> > > > > > > > > > > > > >> > > > 2. Apply ZStd 1.3.4
> > > > > > > > > > > > > >> > > >
> > > > > > > > > > > > > >> > > > You can check out the implementation from
> > here
> > > > > > > > > > > > > >> > > > <
> https://github.com/apache/kafka/pull/2267
> > >.
> > > If
> > > > > you
> > > > > > > > > > > experience
> > > > > > > > > > > > any
> > > > > > > > > > > > > >> > > problem
> > > > > > > > > > > > > >> > > > running it, don't hesitate to give me a
> > > mention.
> > > > > > > > > > > > > >> > > >
> > > > > > > > > > > > > >> > > > Best,
> > > > > > > > > > > > > >> > > > Dongjin
> > > > > > > > > > > > > >> > > >
> > > > > > > > > > > > > >> > > > On Tue, Jun 12, 2018 at 6:50 PM Dongjin
> Lee
> > <
> > > > > > > > > > > dong...@apache.org
> > > > > > > > > > > > >
> > > > > > > > > > > > > >> > wrote:
> > > > > > > > > > > > > >> > > >
> > > > > > > > > > > > > >> > > > > Here is the short conclusion about the
> > > license
> > > > > > > > problem:
> > > > > > > > > > *We
> > > > > > > > > > > > can
> > > > > > > > > > > > > >> use
> > > > > > > > > > > > > >> > > zstd
> > > > > > > > > > > > > >> > > > > and zstd-jni without any problem, but we
> > > need
> > > > to
> > > > > > > > include
> > > > > > > > > > > their
> > > > > > > > > > > > > >> > license,
> > > > > > > > > > > > > >> > > > > e.g., BSD license.*
> > > > > > > > > > > > > >> > > > >
> > > > > > > > > > > > > >> > > > > Both of BSD 2 Clause License & 3 Clause
> > > > License
> > > > > > > > requires
> > > > > > > > > > to
> > > > > > > > > > > > > >> include
> > > > > > > > > > > > > >> > the
> > > > > > > > > > > > > >> > > > > license used, and BSD 3 Clause License
> > > > requires
> > > > > > that
> > > > > > > > the
> > > > > > > > > > > name
> > > > > > > > > > > > of
> > > > > > > > > > > > > >> the
> > > > > > > > > > > > > >> > > > > contributor can't be used to endorse or
> > > > promote
> > > > > > the
> > > > > > > > > > product.
> > > > > > > > > > > > > >> That's
> > > > > > > > > > > > > >> > it
> > > > > > > > > > > > > >> > > > > <
> > > > > > > > > > > > > >> > > >
> > > > > > > > > > > > > >> > >
> > > > > > > > > > > > > >> >
> > > > > > > > > > > > > >>
> > http://www.mikestratton.net/2011/12/is-bsd-license-
> > > > > > > > > > > > compatible-with-apache-2-0-license/
> > > > > > > > > > > > > >> > > > >
> > > > > > > > > > > > > >> > > > > - They are not listed in the list of
> > > > prohibited
> > > > > > > > licenses
> > > > > > > > > > > > > >> > > > > <https://www.apache.org/legal/
> > > > > > > > resolved.html#category-x>
> > > > > > > > > > > also.
> > > > > > > > > > > > > >> > > > >
> > > > > > > > > > > > > >> > > > > Here is how Spark did for it
> > > > > > > > > > > > > >> > > > > <https://issues.apache.org/
> > > > > > jira/browse/SPARK-19112
> > > > > > > >:
> > > > > > > > > > > > > >> > > > >
> > > > > > > > > > > > > >> > > > > - They made a directory dedicated to the
> > > > > > dependency
> > > > > > > > > > license
> > > > > > > > > > > > files
> > > > > > > > > > > > > >> > > > > <
> > > > > > > https://github.com/apache/spark/tree/master/licenses
> > > > > > > > >
> > > > > > > > > > and
> > > > > > > > > > > > added
> > > > > > > > > > > > > >> > > > licenses
> > > > > > > > > > > > > >> > > > > for Zstd
> > > > > > > > > > > > > >> > > > > <
> > > > > > > > > > > > > >> >
> > > > https://github.com/apache/spark/blob/master/licenses/
> > > > > > > > > > > > LICENSE-zstd.txt
> > > > > > > > > > > > > >> > > >
> > > > > > > > > > > > > >> > > > &
> > > > > > > > > > > > > >> > > > > Zstd-jni
> > > > > > > > > > > > > >> > > > > <
> > > > > > > > > > > > > >> > > >
> > > > > > > > > > > > > >> > >
> > > > > > > > > > > > > >> >
> > > > > > > > > > > > > >> https://github.com/apache/
> > > spark/blob/master/licenses/
> > > > > > > > > > > > LICENSE-zstd-jni.txt
> > > > > > > > > > > > > >> >
> > > > > > > > > > > > > >> > > > > .
> > > > > > > > > > > > > >> > > > > - Added a link to the original license
> > files
> > > > in
> > > > > > > > LICENSE.
> > > > > > > > > > > > > >> > > > > <
> > > > > https://github.com/apache/spark/pull/18805/files
> > > > > > >
> > > > > > > > > > > > > >> > > > >
> > > > > > > > > > > > > >> > > > > If needed, I can make a similar update.
> > > > > > > > > > > > > >> > > > >
> > > > > > > > > > > > > >> > > > > Thanks for pointing out this problem,
> > > Viktor!
> > > > > Nice
> > > > > > > > > catch!
> > > > > > > > > > > > > >> > > > >
> > > > > > > > > > > > > >> > > > > Best,
> > > > > > > > > > > > > >> > > > > Dongjin
> > > > > > > > > > > > > >> > > > >
> > > > > > > > > > > > > >> > > > >
> > > > > > > > > > > > > >> > > > >
> > > > > > > > > > > > > >> > > > > On Mon, Jun 11, 2018 at 11:50 PM Dongjin
> > > Lee <
> > > > > > > > > > > > dong...@apache.org>
> > > > > > > > > > > > > >> > > wrote:
> > > > > > > > > > > > > >> > > > >
> > > > > > > > > > > > > >> > > > >> I greatly appreciate your comprehensive
> > > > > > reasoning.
> > > > > > > > so:
> > > > > > > > > +1
> > > > > > > > > > > > for b
> > > > > > > > > > > > > >> > until
> > > > > > > > > > > > > >> > > > now.
> > > > > > > > > > > > > >> > > > >>
> > > > > > > > > > > > > >> > > > >> For the license issues, I will have a
> > check
> > > > on
> > > > > > how
> > > > > > > > the
> > > > > > > > > > over
> > > > > > > > > > > > > >> projects
> > > > > > > > > > > > > >> > > are
> > > > > > > > > > > > > >> > > > >> doing and share the results.
> > > > > > > > > > > > > >> > > > >>
> > > > > > > > > > > > > >> > > > >> Best,
> > > > > > > > > > > > > >> > > > >> Dongjin
> > > > > > > > > > > > > >> > > > >>
> > > > > > > > > > > > > >> > > > >> On Mon, Jun 11, 2018 at 10:08 PM Viktor
> > > > > Somogyi <
> > > > > > > > > > > > > >> > > > viktorsomo...@gmail.com>
> > > > > > > > > > > > > >> > > > >> wrote:
> > > > > > > > > > > > > >> > > > >>
> > > > > > > > > > > > > >> > > > >>> Hi Dongjin,
> > > > > > > > > > > > > >> > > > >>>
> > > > > > > > > > > > > >> > > > >>> A couple of comments:
> > > > > > > > > > > > > >> > > > >>> I would vote for option b. in the
> > > "backward
> > > > > > > > > > compatibility"
> > > > > > > > > > > > > >> section.
> > > > > > > > > > > > > >> > > My
> > > > > > > > > > > > > >> > > > >>> reasoning for this is that users
> > upgrading
> > > > to
> > > > > a
> > > > > > > zstd
> > > > > > > > > > > > compatible
> > > > > > > > > > > > > >> > > version
> > > > > > > > > > > > > >> > > > >>> won't start to use it automatically,
> so
> > > > manual
> > > > > > > > > > > > reconfiguration
> > > > > > > > > > > > > >> is
> > > > > > > > > > > > > >> > > > >>> required.
> > > > > > > > > > > > > >> > > > >>> Therefore an upgrade won't mess up the
> > > > > cluster.
> > > > > > If
> > > > > > > > not
> > > > > > > > > > all
> > > > > > > > > > > > the
> > > > > > > > > > > > > >> > > clients
> > > > > > > > > > > > > >> > > > >>> are
> > > > > > > > > > > > > >> > > > >>> upgraded but just some of them and
> > they'd
> > > > > start
> > > > > > to
> > > > > > > > use
> > > > > > > > > > > zstd
> > > > > > > > > > > > > >> then it
> > > > > > > > > > > > > >> > > > would
> > > > > > > > > > > > > >> > > > >>> cause errors in the cluster. I'd like
> to
> > > > > presume
> > > > > > > > > though
> > > > > > > > > > > that
> > > > > > > > > > > > > >> this
> > > > > > > > > > > > > >> > is
> > > > > > > > > > > > > >> > > a
> > > > > > > > > > > > > >> > > > >>> very
> > > > > > > > > > > > > >> > > > >>> obvious failure case and nobody should
> > be
> > > > > > > surprised
> > > > > > > > if
> > > > > > > > > > it
> > > > > > > > > > > > didn't
> > > > > > > > > > > > > >> > > work.
> > > > > > > > > > > > > >> > > > >>> I wouldn't choose a. as I think we
> > should
> > > > bump
> > > > > > the
> > > > > > > > > fetch
> > > > > > > > > > > and
> > > > > > > > > > > > > >> > produce
> > > > > > > > > > > > > >> > > > >>> requests if it's a change in the
> message
> > > > > format.
> > > > > > > > > > Moreover
> > > > > > > > > > > if
> > > > > > > > > > > > > >> some
> > > > > > > > > > > > > >> > of
> > > > > > > > > > > > > >> > > > the
> > > > > > > > > > > > > >> > > > >>> producers and the brokers are upgraded
> > but
> > > > > some
> > > > > > of
> > > > > > > > the
> > > > > > > > > > > > consumers
> > > > > > > > > > > > > >> > are
> > > > > > > > > > > > > >> > > > not,
> > > > > > > > > > > > > >> > > > >>> then we wouldn't prevent the error
> when
> > > the
> > > > > old
> > > > > > > > > consumer
> > > > > > > > > > > > tries
> > > > > > > > > > > > > >> to
> > > > > > > > > > > > > >> > > > consume
> > > > > > > > > > > > > >> > > > >>> the zstd compressed messages.
> > > > > > > > > > > > > >> > > > >>> I wouldn't choose c. either as I think
> > > > binding
> > > > > > the
> > > > > > > > > > > > compression
> > > > > > > > > > > > > >> type
> > > > > > > > > > > > > >> > > to
> > > > > > > > > > > > > >> > > > an
> > > > > > > > > > > > > >> > > > >>> API is not so obvious from the
> > developer's
> > > > > > > > > perspective.
> > > > > > > > > > > > > >> > > > >>>
> > > > > > > > > > > > > >> > > > >>> I would also prefer to use the
> existing
> > > > > binding,
> > > > > > > > > however
> > > > > > > > > > > we
> > > > > > > > > > > > must
> > > > > > > > > > > > > >> > > > respect
> > > > > > > > > > > > > >> > > > >>> the licenses:
> > > > > > > > > > > > > >> > > > >>> "The code for these JNI bindings is
> > > licenced
> > > > > > under
> > > > > > > > > > > 2-clause
> > > > > > > > > > > > BSD
> > > > > > > > > > > > > >> > > > license.
> > > > > > > > > > > > > >> > > > >>> The native Zstd library is licensed
> > under
> > > > > > 3-clause
> > > > > > > > BSD
> > > > > > > > > > > > license
> > > > > > > > > > > > > >> and
> > > > > > > > > > > > > >> > > > GPL2"
> > > > > > > > > > > > > >> > > > >>> Based on the FAQ page
> > > > > > > > > > > > > >> > > > >>> https://www.apache.org/legal/
> > > > > > > > resolved.html#category-a
> > > > > > > > > > > > > >> > > > >>> we may use 2- and 3-clause BSD
> licenses
> > > but
> > > > > the
> > > > > > > > Apache
> > > > > > > > > > > > license
> > > > > > > > > > > > > >> is
> > > > > > > > > > > > > >> > not
> > > > > > > > > > > > > >> > > > >>> compatible with GPL2. I'm hoping that
> > the
> > > > > > > "3-clause
> > > > > > > > > BSD
> > > > > > > > > > > > license
> > > > > > > > > > > > > >> and
> > > > > > > > > > > > > >> > > > GPL2"
> > > > > > > > > > > > > >> > > > >>> is really not an AND but an OR in this
> > > case,
> > > > > but
> > > > > > > I'm
> > > > > > > > > no
> > > > > > > > > > > > lawyer,
> > > > > > > > > > > > > >> > just
> > > > > > > > > > > > > >> > > > >>> wanted
> > > > > > > > > > > > > >> > > > >>> to make the point that we should watch
> > out
> > > > for
> > > > > > > > > licenses.
> > > > > > > > > > > :)
> > > > > > > > > > > > > >> > > > >>>
> > > > > > > > > > > > > >> > > > >>> Regards,
> > > > > > > > > > > > > >> > > > >>> Viktor
> > > > > > > > > > > > > >> > > > >>>
> > > > > > > > > > > > > >> > > > >>>
> > > > > > > > > > > > > >> > > > >>> On Sun, Jun 10, 2018 at 3:02 AM Ivan
> > > Babrou
> > > > <
> > > > > > > > > > > > ibob...@gmail.com>
> > > > > > > > > > > > > >> > > wrote:
> > > > > > > > > > > > > >> > > > >>>
> > > > > > > > > > > > > >> > > > >>> > Hello,
> > > > > > > > > > > > > >> > > > >>> >
> > > > > > > > > > > > > >> > > > >>> > This is Ivan and I still very much
> > > support
> > > > > the
> > > > > > > > fact
> > > > > > > > > > that
> > > > > > > > > > > > zstd
> > > > > > > > > > > > > >> > > > >>> compression
> > > > > > > > > > > > > >> > > > >>> > should be included out of the box.
> > > > > > > > > > > > > >> > > > >>> >
> > > > > > > > > > > > > >> > > > >>> > Please think about the environment,
> > you
> > > > can
> > > > > > save
> > > > > > > > > > quite a
> > > > > > > > > > > > lot
> > > > > > > > > > > > > >> of
> > > > > > > > > > > > > >> > > > >>> hardware
> > > > > > > > > > > > > >> > > > >>> > with it.
> > > > > > > > > > > > > >> > > > >>> >
> > > > > > > > > > > > > >> > > > >>> > Thank you.
> > > > > > > > > > > > > >> > > > >>> >
> > > > > > > > > > > > > >> > > > >>> > On Sat, Jun 9, 2018 at 14:14 Dongjin
> > > Lee <
> > > > > > > > > > > > dong...@apache.org>
> > > > > > > > > > > > > >> > > wrote:
> > > > > > > > > > > > > >> > > > >>> >
> > > > > > > > > > > > > >> > > > >>> > > Since there are no responses for a
> > > > week, I
> > > > > > > > decided
> > > > > > > > > > to
> > > > > > > > > > > > > >> > reinitiate
> > > > > > > > > > > > > >> > > > the
> > > > > > > > > > > > > >> > > > >>> > > discussion thread.
> > > > > > > > > > > > > >> > > > >>> > >
> > > > > > > > > > > > > >> > > > >>> > >
> > > > > > > > > > > > > >> > > > >>> > >
> > > > > > > > > > > > > >> > > > >>> >
> > > > > > > > > > > > > >> > > > >>>
> > > > > > > > > > > > > >> > > >
> > > > > > > > > > > > > >> > >
> > > > > > > > > > > > > >> >
> > > > > > > > > > > > > >>
> > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-
> > > > > > > > > > > > 110%3A+Add+Codec+for+ZStandard+Compression
> > > > > > > > > > > > > >> > > > >>> > >
> > > > > > > > > > > > > >> > > > >>> > > This KIP is about to introduce
> > > ZStandard
> > > > > > > > > Compression
> > > > > > > > > > > > into
> > > > > > > > > > > > > >> > Apache
> > > > > > > > > > > > > >> > > > >>> Kafka.
> > > > > > > > > > > > > >> > > > >>> > > The reason why it is posted again
> > has
> > > a
> > > > > > story:
> > > > > > > > It
> > > > > > > > > > was
> > > > > > > > > > > > > >> > originally
> > > > > > > > > > > > > >> > > > >>> posted
> > > > > > > > > > > > > >> > > > >>> > to
> > > > > > > > > > > > > >> > > > >>> > > the dev mailing list more than one
> > > year
> > > > > ago
> > > > > > > but
> > > > > > > > > > since
> > > > > > > > > > > it
> > > > > > > > > > > > > >> has no
> > > > > > > > > > > > > >> > > > >>> > performance
> > > > > > > > > > > > > >> > > > >>> > > report included, it was postponed
> > > later.
> > > > > But
> > > > > > > > Some
> > > > > > > > > > > people
> > > > > > > > > > > > > >> > > (including
> > > > > > > > > > > > > >> > > > >>> Ivan)
> > > > > > > > > > > > > >> > > > >>> > > reported excellent performance
> > report
> > > > with
> > > > > > the
> > > > > > > > > draft
> > > > > > > > > > > PR,
> > > > > > > > > > > > > >> this
> > > > > > > > > > > > > >> > > work
> > > > > > > > > > > > > >> > > > >>> is now
> > > > > > > > > > > > > >> > > > >>> > > reactivated.
> > > > > > > > > > > > > >> > > > >>> > >
> > > > > > > > > > > > > >> > > > >>> > > The updated KIP document includes
> > some
> > > > > > > expected
> > > > > > > > > > > > problems and
> > > > > > > > > > > > > >> > > their
> > > > > > > > > > > > > >> > > > >>> > > candidate alternatives. Please
> have
> > a
> > > > look
> > > > > > > when
> > > > > > > > > you
> > > > > > > > > > > are
> > > > > > > > > > > > > >> free,
> > > > > > > > > > > > > >> > and
> > > > > > > > > > > > > >> > > > >>> give
> > > > > > > > > > > > > >> > > > >>> > me a
> > > > > > > > > > > > > >> > > > >>> > > feedback. All kinds of
> participating
> > > are
> > > > > > > > welcome.
> > > > > > > > > > > > > >> > > > >>> > >
> > > > > > > > > > > > > >> > > > >>> > > Best,
> > > > > > > > > > > > > >> > > > >>> > > Dongjin
> > > > > > > > > > > > > >> > > > >>> > >
> > > > > > > > > > > > > >> > > > >>> > > --
> > > > > > > > > > > > > >> > > > >>> > > *Dongjin Lee*
> > > > > > > > > > > > > >> > > > >>> > >
> > > > > > > > > > > > > >> > > > >>> > > *A hitchhiker in the mathematical
> > > > world.*
> > > > > > > > > > > > > >> > > > >>> > >
> > > > > > > > > > > > > >> > > > >>> > > *github: <http://goog_969573159/
> > > > >github
> > > > > > > > > > > > .com/dongjinleekr
> > > > > > > > > > > > > >> > > > >>> > > <http://github.com/dongjinleekr
> > > > >linkedin:
> > > > > > > > > > > > > >> > > > >>> > kr.linkedin.com/in/dongjinleekr
> > > > > > > > > > > > > >> > > > >>> > > <http://kr.linkedin.com/in/
> > > dongjinleekr
> > > > > > > > > >slideshare:
> > > > > > > > > > > > > >> > > > >>> > www.slideshare.net/dongjinleekr
> > > > > > > > > > > > > >> > > > >>> > > <http://www.slideshare.net/
> > > dongjinleekr
> > > > >*
> > > > > > > > > > > > > >> > > > >>> > >
> > > > > > > > > > > > > >> > > > >>> >
> > > > > > > > > > > > > >> > > > >>>
> > > > > > > > > > > > > >> > > > >> --
> > > > > > > > > > > > > >> > > > >> *Dongjin Lee*
> > > > > > > > > > > > > >> > > > >>
> > > > > > > > > > > > > >> > > > >> *A hitchhiker in the mathematical
> world.*
> > > > > > > > > > > > > >> > > > >>
> > > > > > > > > > > > > >> > > > >> *github: <http://goog_969573159/
> >github
> > > > > > > > > > .com/dongjinleekr
> > > > > > > > > > > > > >> > > > >> <http://github.com/dongjinleekr
> > >linkedin:
> > > > > > > > > > > > > >> > > > kr.linkedin.com/in/dongjinleekr
> > > > > > > > > > > > > >> > > > >> <
> http://kr.linkedin.com/in/dongjinleekr
> > > > > > > >slideshare:
> > > > > > > > > > > > > >> > > > www.slideshare.net/dongjinleekr
> > > > > > > > > > > > > >> > > > >> <
> http://www.slideshare.net/dongjinleekr
> > >*
> > > > > > > > > > > > > >> > > > >>
> > > > > > > > > > > > > >> > > > >
> > > > > > > > > > > > > >> > > > >
> > > > > > > > > > > > > >> > > > > --
> > > > > > > > > > > > > >> > > > > *Dongjin Lee*
> > > > > > > > > > > > > >> > > > >
> > > > > > > > > > > > > >> > > > > *A hitchhiker in the mathematical
> world.*
> > > > > > > > > > > > > >> > > > >
> > > > > > > > > > > > > >> > > > > *github: <http://goog_969573159/>
> > > > > > > > > github.com/dongjinleekr
> > > > > > > > > > > > > >> > > > > <http://github.com/dongjinleekr
> >linkedin:
> > > > > > > > > > > > > >> > > > kr.linkedin.com/in/dongjinleekr
> > > > > > > > > > > > > >> > > > > <http://kr.linkedin.com/in/dongjinleekr
> > > > > > >slideshare:
> > > > > > > > > > > > > >> > > > www.slideshare.net/dongjinleekr
> > > > > > > > > > > > > >> > > > > <http://www.slideshare.net/dongjinleekr
> >*
> > > > > > > > > > > > > >> > > > >
> > > > > > > > > > > > > >> > > >
> > > > > > > > > > > > > >> > > >
> > > > > > > > > > > > > >> > > > --
> > > > > > > > > > > > > >> > > > *Dongjin Lee*
> > > > > > > > > > > > > >> > > >
> > > > > > > > > > > > > >> > > > *A hitchhiker in the mathematical world.*
> > > > > > > > > > > > > >> > > >
> > > > > > > > > > > > > >> > > > *github: <http://goog_969573159/>github
> > > > > > > > .com/dongjinleekr
> > > > > > > > > > > > > >> > > > <http://github.com/dongjinleekr>linkedin:
> > > > > > > > > > > > > >> > > kr.linkedin.com/in/dongjinleekr
> > > > > > > > > > > > > >> > > > <http://kr.linkedin.com/in/dongjinleekr
> > > > > >slideshare:
> > > > > > > > > > > > > >> > > > www.slideshare.net/dongjinleekr
> > > > > > > > > > > > > >> > > > <http://www.slideshare.net/dongjinleekr>*
> > > > > > > > > > > > > >> > > >
> > > > > > > > > > > > > >> > >
> > > > > > > > > > > > > >> >
> > > > > > > > > > > > > >>
> > > > > > > > > > > > > >> --
> > > > > > > > > > > > > >> *Dongjin Lee*
> > > > > > > > > > > > > >>
> > > > > > > > > > > > > >> *A hitchhiker in the mathematical world.*
> > > > > > > > > > > > > >>
> > > > > > > > > > > > > >> *github: <http://goog_969573159/>
> > > > > github.com/dongjinleekr
> > > > > > > > > > > > > >> <http://github.com/dongjinleekr>linkedin:
> > > > > > > kr.linkedin.com/in/
> > > > > > > > > > > > dongjinleekr
> > > > > > > > > > > > > >> <http://kr.linkedin.com/in/dongjinleekr
> > >slideshare:
> > > > > > > > > > > > www.slideshare.net/dongjinleekr
> > > > > > > > > > > > > >> <http://www.slideshare.net/dongjinleekr>*
> > > > > > > > > > > > > >>
> > > > > > > > > > > > > >
> > > > > > > > > > > > >
> > > > > > > > > > > > > --
> > > > > > > > > > > > > *Dongjin Lee*
> > > > > > > > > > > > >
> > > > > > > > > > > > > *A hitchhiker in the mathematical world.*
> > > > > > > > > > > > >
> > > > > > > > > > > > > *github: <http://goog_969573159/>
> > > > github.com/dongjinleekr
> > > > > > > > > > > > > <http://github.com/dongjinleekr>linkedin:
> > > > > > kr.linkedin.com/in/
> > > > > > > > > > > > dongjinleekr
> > > > > > > > > > > > > <http://kr.linkedin.com/in/dongjinleekr
> >slideshare:
> > > > > > > > > > > > > www.slideshare.net/dongjinleekr
> > > > > > > > > > > > > <http://www.slideshare.net/dongjinleekr>*
> > > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > --
> > > > > > > > > > > *Dongjin Lee*
> > > > > > > > > > >
> > > > > > > > > > > *A hitchhiker in the mathematical world.*
> > > > > > > > > > >
> > > > > > > > > > > *github: <http://goog_969573159/>
> > github.com/dongjinleekr
> > > > > > > > > > > <http://github.com/dongjinleekr>linkedin:
> > > > kr.linkedin.com/in/
> > > > > > > > > > dongjinleekr
> > > > > > > > > > > <http://kr.linkedin.com/in/dongjinleekr>slideshare:
> > > > > > > > > www.slideshare.net/
> > > > > > > > > > dongjinleekr
> > > > > > > > > > > <http://www.slideshare.net/dongjinleekr>*
> > > > > > > > > > >
> > > > > > > > > >
> > > > > > > > >
> > > > > > > > > --
> > > > > > > > > *Dongjin Lee*
> > > > > > > > >
> > > > > > > > > *A hitchhiker in the mathematical world.*
> > > > > > > > >
> > > > > > > > > *github: <http://goog_969573159/>github.com/dongjinleekr
> > > > > > > > > <http://github.com/dongjinleekr>linkedin:
> > kr.linkedin.com/in/
> > > > > > > > dongjinleekr
> > > > > > > > > <http://kr.linkedin.com/in/dongjinleekr>slideshare:
> > > > > > > www.slideshare.net/
> > > > > > > > dongjinleekr
> > > > > > > > > <http://www.slideshare.net/dongjinleekr>*
> > > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > > > --
> > > > *Dongjin Lee*
> > > >
> > > > *A hitchhiker in the mathematical world.*
> > > >
> > > > *github: <http://goog_969573159/>github.com/dongjinleekr
> > > > <http://github.com/dongjinleekr>linkedin: kr.linkedin.com/in/
> > > dongjinleekr
> > > > <http://kr.linkedin.com/in/dongjinleekr>slideshare:
> > www.slideshare.net/
> > > dongjinleekr
> > > > <http://www.slideshare.net/dongjinleekr>*
> > > >
> > >
> >
>
> --
> *Dongjin Lee*
>
> *A hitchhiker in the mathematical world.*
>
> *github: <http://goog_969573159/>github.com/dongjinleekr
> <http://github.com/dongjinleekr>linkedin: kr.linkedin.com/in/dongjinleekr
> <http://kr.linkedin.com/in/dongjinleekr>slideshare:
> www.slideshare.net/dongjinleekr
> <http://www.slideshare.net/dongjinleekr>*
>
