Hi, Dongjin,
Sorry for interrupting the discussion.
And thank you for your hard work about KIP-653, KIP-719.
I understand that KIP-653 is already accepted so log4j2 is the choice of
the Kafka community though, I'm now feeling that logback is a better choice
here.
Reasons:
- even after "log4shell", several vulnerabilities found on log4j2 so new
versions are released and users have to update in high-pace
* actually, a CVE was also reported for logback (CVE-2021-42550) but it
requires edit-permission of the config file for an attacker so it's much
less threatening
- log4j1.x and logback are made by same developer (ceki), so substantially
the successor of log4j1 is logback rather than log4j2
- in Hadoop project, seems similar suggestion was made from a PMC
* https://issues.apache.org/jira/browse/HADOOP-12956
What do you think about adopting logback instead?
Thanks,
2021年12月21日(火) 18:02 Dongjin Lee <dong...@apache.org>:
> Hi Mickael,
>
> > In the meantime, you may want to bump the VOTE thread too.
>
> Sure, I just reset the voting thread with a brief context.
>
> Thanks,
> Dongjin
>
> On Tue, Dec 21, 2021 at 2:13 AM Mickael Maison <mickael.mai...@gmail.com>
> wrote:
>
> > Thanks Dongjin!
> >
> > I'll take a look soon.
> > In the meantime, you may want to bump the VOTE thread too.
> >
> > Best,
> > Mickael
> >
> >
> > On Sat, Dec 18, 2021 at 10:00 AM Dongjin Lee <dong...@apache.org> wrote:
> > >
> > > Hi Mickael,
> > >
> > > Finally, I did it! As you can see at the PR
> > > <https://github.com/apache/kafka/pull/10244>, KIP-719 now uses
> log4j2's
> > > Kafka appender, and log4j-appender is not used by the other modules
> > > anymore. You can see how it will work with KIP-653 at this preview
> > > <http://home.apache.org/~dongjin/post/apache-kafka-log4j2-support/>,
> > based
> > > on Apache Kafka 3.0.0. The proposal document
> > > <
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-719%3A+Deprecate+Log4J+Appender
> > >
> > > is also updated accordingly, with its title.
> > >
> > > There is a minor issue on log4j2
> > > <https://issues.apache.org/jira/browse/LOG4J2-3256>, but it seems like
> > it
> > > will be resolved soon.
> > >
> > > Best,
> > > Dongjin
> > >
> > > On Wed, Dec 15, 2021 at 9:28 PM Dongjin Lee <dong...@apache.org>
> wrote:
> > >
> > > > Hi Mickael,
> > > >
> > > > > Can we do step 3 without breaking any compatibility? If so then
> that
> > > > sounds like a good idea.
> > > >
> > > > As far as I know, the answer is yes; I am now updating my PR, so I
> will
> > > > notify you as soon as I complete the work.
> > > >
> > > > Best,
> > > > Dongjin
> > > >
> > > > On Wed, Dec 15, 2021 at 2:00 AM Mickael Maison <
> > mickael.mai...@gmail.com>
> > > > wrote:
> > > >
> > > >> Hi Dongjin,
> > > >>
> > > >> Sorry for the late reply. Can we do step 3 without breaking any
> > > >> compatibility? If so then that sounds like a good idea.
> > > >>
> > > >> Thanks,
> > > >> Mickael
> > > >>
> > > >>
> > > >>
> > > >> On Tue, Nov 23, 2021 at 2:08 PM Dongjin Lee <dong...@apache.org>
> > wrote:
> > > >> >
> > > >> > Hi Mickael,
> > > >> >
> > > >> > I also thought over the issue thoroughly and would like to
> propose a
> > > >> minor
> > > >> > change to your proposal:
> > > >> >
> > > >> > 1. Deprecate log4j-appender now
> > > >> > 2. Document how to migrate into logging-log4j2
> > > >> > 3. (Changed) Replace the log4j-appender (in turn log4j 1.x)
> > > >> dependencies in
> > > >> > tools, trogdor, and shell and upgrade to log4j2 in 3.x, removing
> > log4j
> > > >> 1.x
> > > >> > dependencies.
> > > >> > 4. (Changed) Remove log4j-appender in Kafka 4.0
> > > >> >
> > > >> > What we need to do for the log4j2 upgrade is just removing the
> log4j
> > > >> > dependencies only, for they can cause a classpath error. And
> > actually,
> > > >> we
> > > >> > can do it without discontinuing publishing the log4j-appender
> > artifact.
> > > >> So,
> > > >> > I suggest separating the upgrade to log4j2 and removing the
> > > >> log4j-appender
> > > >> > module.
> > > >> >
> > > >> > How do you think? If you agree, I will update the KIP and the PR
> > > >> > accordingly ASAP.
> > > >> >
> > > >> > Thanks,
> > > >> > Dongjin
> > > >> >
> > > >> > On Mon, Nov 15, 2021 at 8:06 PM Mickael Maison <
> > > >> mickael.mai...@gmail.com>
> > > >> > wrote:
> > > >> >
> > > >> > > Hi Dongjin,
> > > >> > >
> > > >> > > Thanks for the clarifications.
> > > >> > >
> > > >> > > I wonder if a simpler course of action could be:
> > > >> > > - Deprecate log4j-appender now
> > > >> > > - Document how to use logging-log4j2
> > > >> > > - Remove log4j-appender and all the log4j dependencies in Kafka
> > 4.0
> > > >> > >
> > > >> > > This delays KIP-653 till Kafka 4.0 but (so far) Kafka is not
> > directly
> > > >> > > affected by the log4j CVEs. At least this gives us a clear and
> > simple
> > > >> > > roadmap to follow.
> > > >> > >
> > > >> > > What do you think?
> > > >> > >
> > > >> > > On Tue, Nov 9, 2021 at 12:12 PM Dongjin Lee <dong...@apache.org
> >
> > > >> wrote:
> > > >> > > >
> > > >> > > > Hi Mickael,
> > > >> > > >
> > > >> > > > I greatly appreciate you for reading the proposal so
> carefully!
> > I
> > > >> wrote
> > > >> > > it
> > > >> > > > quite a while ago and rechecked it today.
> > > >> > > >
> > > >> > > > > Is the KIP proposing to replace the existing log4-appender
> or
> > > >> simply
> > > >> > > add
> > > >> > > > a new one for log4j2? Reading the KIP and with its current
> > title,
> > > >> it's
> > > >> > > not
> > > >> > > > entirely explicit.
> > > >> > > >
> > > >> > > > Oh, After re-reading it, I realized that this is not clear.
> Let
> > me
> > > >> > > clarify;
> > > >> > > >
> > > >> > > > 1. Provide a lo4j2 equivalent of traditional log4j-appender,
> > > >> > > > log4j2-appender.
> > > >> > > > 2. Migrate the modules depending on log4j-appender (i.e.,
> tools,
> > > >> trogdor,
> > > >> > > > shell) into log4j2-appender, removing log4j-appender from
> > > >> dependencies.
> > > >> > > > 3. Entirely remove log4j-appender from the project
> dependencies,
> > > >> along
> > > >> > > with
> > > >> > > > log4j.
> > > >> > > >
> > > >> > > > I think log4j-appender may be published for every new release
> > like
> > > >> > > before,
> > > >> > > > but the committee should make a decision on the policy.
> > > >> > > >
> > > >> > > > > Under Rejected Alternative, the KIP states: "the Kafka
> > appender
> > > >> > > provided
> > > >> > > > by log4j2 community stores log message in the Record key".
> > Looking
> > > >> at the
> > > >> > > > code, it looks like the log message is stored in the Record
> > value:
> > > >> > > >
> > > >> > >
> > > >>
> >
> https://github.com/apache/logging-log4j2/blob/master/log4j-kafka/src/main/java/org/apache/logging/log4j/kafka/appender/KafkaManager.java#L135
> > > >> > > > Am I missing something?
> > > >> > > >
> > > >> > > > It's totally my fault; I confused it with another appender.
> The
> > > >> > > > compatibility problem in the logging-log4j2 Kafka appender is
> > not
> > > >> the
> > > >> > > > format but the configuration. logging-log4j2 Kafka appender
> > supports
> > > >> > > > `properties` configuration, which will be directly used to
> > > >> instantiate a
> > > >> > > > Kafka producer. However, log4j-appender has been using
> > non-producer
> > > >> > > config
> > > >> > > > names like brokerList (=bootstrap.servers), requiredNumAcks
> > (=acks).
> > > >> > > > Instead, logging-log4j2 Kafka appender supports retryCount,
> > > >> > > > sendEventTimestamp.
> > > >> > > >
> > > >> > > > On second thought, using logging-log4j2 Kafka appender
> > internally
> > > >> and
> > > >> > > > making log4j2-appender to focus on compatibility facade only
> > would
> > > >> be a
> > > >> > > > better approach; As I described above, the goal of this module
> > is
> > > >> just
> > > >> > > > keeping the backward-compatibility, and (as you pointed out)
> the
> > > >> current
> > > >> > > > implementation has little value. Since
> > > >> > > org.apache.logging.log4j:log4j-core
> > > >> > > > already includes Kafka appender, we can make use of the
> 'proven
> > > >> wheel'
> > > >> > > > without adding more dependencies. I have not tried it yet,
> but I
> > > >> think it
> > > >> > > > is well worth it. (One additional advantage of this approach
> is
> > > >> > > providing a
> > > >> > > > bridge to the users who hope to move from/into logging-log4j2
> > Kafka
> > > >> > > > appender.)
> > > >> > > >
> > > >> > > > > As the current log4j-appender is not even deprecated yet, in
> > > >> theory we
> > > >> > > > can't remove it till Kafka 4. If we want to speed up the
> > process, I
> > > >> > > wonder
> > > >> > > > if the lack of documentation and a migration guide could help
> > us.
> > > >> What do
> > > >> > > > you think?
> > > >> > > >
> > > >> > > > In fact, this is what I am doing nowadays. While working with
> > > >> > > > log4j-appender, I found that despite a lack of documentation,
> > > >> > > considerable
> > > >> > > > users are already using it[^1][^2][^3][^4][^5]. So, I think
> > > >> providing a
> > > >> > > > documentation to those who are already using log4j-appender is
> > > >> > > > indispensable. It should include:
> > > >> > > >
> > > >> > > > - What is the difference between log4j-appender vs.
> > log4j2-appender.
> > > >> > > > - Which options are supported and deprecated.
> > > >> > > > - Exemplar configurations that show how to migrate.
> > > >> > > >
> > > >> > > > Here is the summary:
> > > >> > > >
> > > >> > > > 1. The goal of this proposal is to replace the traditional
> > > >> log4j-appender
> > > >> > > > for compatibility concerns. But log4j-appender may be
> published
> > > >> after the
> > > >> > > > deprecation.
> > > >> > > > 2. As of present, the description about logging-log4j2 Kafka
> > > >> appender is
> > > >> > > > entirely wrong. The problem is interface compatibility, not
> > record
> > > >> > > format.
> > > >> > > > Focusing on the compatibility facade is a good approach.
> > > >> > > > 3. A documentation focus on migration should be provided.
> > > >> > > >
> > > >> > > > If you have any questions or suggestions, don't hesitate to
> > tell me.
> > > >> > > Thanks
> > > >> > > > again for your comments!
> > > >> > > >
> > > >> > > > Best,
> > > >> > > > Dongjin
> > > >> > > >
> > > >> > > > [^1]:
> > > >> > > >
> > > >> > >
> > > >>
> >
> https://docs.cloudera.com/csa/1.2.0/monitoring/topics/csa-kafka-logging.html
> > > >> > > > [^2]:
> > > >> > > >
> > > >> > >
> > > >>
> >
> https://stackoverflow.com/questions/22034895/how-to-use-kafka-0-8-log4j-appender
> > > >> > > > [^3]:
> > > >> > > >
> > > >> > >
> > > >>
> >
> https://stackoverflow.com/questions/32402405/delay-in-kafka-log4j-appender
> > > >> > > > [^4]:
> > > >> > > >
> > > >> > >
> > > >>
> >
> https://stackoverflow.com/questions/32301129/kafka-log4j-appender-not-sending-messages
> > > >> > > > [^5]:
> > > >> > > >
> > > >> > >
> > > >>
> >
> https://stackoverflow.com/questions/35628706/kafka-log4j-appender-0-9-does-not-work
> > > >> > > >
> > > >> > > > On Mon, Nov 8, 2021 at 9:04 PM Mickael Maison <
> > > >> mickael.mai...@gmail.com>
> > > >> > > > wrote:
> > > >> > > >
> > > >> > > > > Hi Dongjin,
> > > >> > > > >
> > > >> > > > > Thanks for working on the update to log4j2, it's
> definitively
> > > >> > > > > something we should complete.
> > > >> > > > > I have a couple of comments:
> > > >> > > > >
> > > >> > > > > 1) Is the KIP proposing to replace the existing
> log4-appender
> > or
> > > >> > > > > simply add a new one for log4j2? Reading the KIP and with
> its
> > > >> current
> > > >> > > > > title, it's not entirely explicit. For example I don't see a
> > > >> statement
> > > >> > > > > under the proposed changes section. The PR seems to only add
> > a new
> > > >> > > > > appender but the KIP mentions we want to fully remove
> > > >> dependencies to
> > > >> > > > > log4j.
> > > >> > > > >
> > > >> > > > > 2) Under Rejected Alternative, the KIP states: "the Kafka
> > appender
> > > >> > > > > provided by log4j2 community stores log message in the
> Record
> > > >> key".
> > > >> > > > > Looking at the code, it looks like the log message is stored
> > in
> > > >> the
> > > >> > > > > Record value:
> > > >> > > > >
> > > >> > >
> > > >>
> >
> https://github.com/apache/logging-log4j2/blob/master/log4j-kafka/src/main/java/org/apache/logging/log4j/kafka/appender/KafkaManager.java#L135
> > > >> > > > > Am I missing something?
> > > >> > > > > Comparing it with the proposed new appender, apart from
> their
> > > >> > > > > configuration format (hence the backwards compatibility
> > issues),
> > > >> they
> > > >> > > > > both work pretty much the same way, so it's not clear it
> would
> > > >> add a
> > > >> > > > > ton a value.
> > > >> > > > >
> > > >> > > > > At a glance, _I've not extensively looked at it_, it does
> not
> > look
> > > >> > > > > very hard to migrate to the appender from the logging team.
> I
> > was
> > > >> > > > > wondering if we should mention it in our documentation but I
> > was
> > > >> not
> > > >> > > > > able to find any references to the log4j-appender in the
> Kafka
> > > >> docs:
> > > >> > > > >
> > https://github.com/apache/kafka-site/search?q=KafkaLog4jAppender
> > > >> > > > >
> > > >> > > > > As the current log4j-appender is not even deprecated yet, in
> > > >> theory we
> > > >> > > > > can't remove it till Kafka 4. If we want to speed up the
> > process,
> > > >> I
> > > >> > > > > wonder if the lack of documentation and a migration guide
> > could
> > > >> help
> > > >> > > > > us. What do you think?
> > > >> > > > >
> > > >> > > > > Thanks,
> > > >> > > > > Mickael
> > > >> > > > >
> > > >> > > > >
> > > >> > > > >
> > > >> > > > >
> > > >> > > > > On Fri, Jun 11, 2021 at 4:57 PM Boojapho O <
> > booja...@gmail.com>
> > > >> wrote:
> > > >> > > > > >
> > > >> > > > > > Continuing to use log4j would leave several known security
> > > >> > > > > vulnerabilities in Apache Kafka, including
> > > >> > > > > https://nvd.nist.gov/vuln/detail/CVE-2019-17571. The
> Apache
> > > >> log4j
> > > >> > > team
> > > >> > > > > will not fix this vulnerability and is urging an upgrade to
> > > >> log4j2.
> > > >> > > See
> > > >> > > > > https://logging.apache.org/log4j/1.2/ for further
> > information.
> > > >> > > > > >
> > > >> > > > > > This is desperately needed in Apache 3.0 to keep the
> > software
> > > >> secure.
> > > >> > > > > >
> > > >> > > > > > On 2021/05/26 12:31:20, Dongjin Lee <dong...@apache.org>
> > wrote:
> > > >> > > > > > > CC'd the +1ers of KIP-653 with detailed context:
> > > >> > > > > > >
> > > >> > > > > > > When I submitted and got the approval of KIP-653:
> Upgrade
> > > >> log4j to
> > > >> > > > > log4j2
> > > >> > > > > > > <
> > > >> > > > >
> > > >> > >
> > > >>
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-653%3A+Upgrade+log4j+to+log4j2
> > > >> > > > > >,
> > > >> > > > > > > I thought the log4j2-appender should not be the scope of
> > the
> > > >> work.
> > > >> > > But
> > > >> > > > > it
> > > >> > > > > > > was wrong.
> > > >> > > > > > >
> > > >> > > > > > > Since the VerifiableLog4jAppender tool is built upon
> > > >> > > log4j-appender,
> > > >> > > > > log4j
> > > >> > > > > > > 1.x artifact will co-exist with log4j2 artifact in the
> > > >> classpath
> > > >> > > within
> > > >> > > > > > > this scheme. Since the log4j 1.x code is not called
> > anymore, I
> > > >> > > thought
> > > >> > > > > it
> > > >> > > > > > > is not problematic but actually, it was not - when I
> > started
> > > >> to
> > > >> > > > > provide a
> > > >> > > > > > > preview of KIP-653
> > > >> > > > > > > <
> > > >> http://home.apache.org/~dongjin/post/apache-kafka-log4j2-support/
> > > >> > > >,
> > > >> > > > > some
> > > >> > > > > > > users reported that sometimes slf4j fails to find the
> > > >> appropriate
> > > >> > > > > binding
> > > >> > > > > > > within the classpath, resulting fail to append the log
> > > >> message.
> > > >> > > > > > >
> > > >> > > > > > > To resolve this problem, I subtly adjusted the scope of
> > the
> > > >> work; I
> > > >> > > > > > > excluded Tools and Trogdor from KIP-653 and extended
> > KIP-719
> > > >> to
> > > >> > > take
> > > >> > > > > care
> > > >> > > > > > > of them instead, along with providing log4j2-appender.
> It
> > is
> > > >> why
> > > >> > > the
> > > >> > > > > > > current WIP implementations include some classpath logic
> > in
> > > >> the
> > > >> > > shell
> > > >> > > > > > > script and *why KIP-653 only can't complete the log4j2
> > > >> migration*.
> > > >> > > > > > >
> > > >> > > > > > > I hope you will check this proposal out.
> > > >> > > > > > >
> > > >> > > > > > > Best,
> > > >> > > > > > > Dongjin
> > > >> > > > > > >
> > > >> > > > > > > On Tue, May 25, 2021 at 10:43 PM Dongjin Lee <
> > > >> dong...@apache.org>
> > > >> > > > > wrote:
> > > >> > > > > > >
> > > >> > > > > > > > Bumping up the discussion thread.
> > > >> > > > > > > >
> > > >> > > > > > > > Recently, I updated the document of KIP-653: Upgrade
> > log4j
> > > >> to
> > > >> > > log4j2
> > > >> > > > > > > > <
> > > >> > > > >
> > > >> > >
> > > >>
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-653%3A+Upgrade+log4j+to+log4j2
> > > >> > > >
> > > >> > > > > (accepted)
> > > >> > > > > > > > and KIP-719: Add Log4J2 Appender
> > > >> > > > > > > > <
> > > >> > > > >
> > > >> > >
> > > >>
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-719%3A+Add+Log4J2+Appender
> > > >> > > >
> > > >> > > > > (under
> > > >> > > > > > > > discussion) reflecting the recent changes to our
> > codebase.
> > > >> > > > > Especially:
> > > >> > > > > > > >
> > > >> > > > > > > > 1. KIP-653 document
> > > >> > > > > > > > <
> > > >> > > > >
> > > >> > >
> > > >>
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-653%3A+Upgrade+log4j+to+log4j2
> > > >> > > >
> > > >> > > > > now
> > > >> > > > > > > > explains which modules will be migrated and why.
> > > >> > > > > > > > 2. KIP-719 document
> > > >> > > > > > > > <
> > > >> > > > >
> > > >> > >
> > > >>
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-719%3A+Add+Log4J2+Appender
> > > >> > > >
> > > >> > > > > now
> > > >> > > > > > > > explains not only the log4j2-appender plan but also
> > > >> upgrading the
> > > >> > > > > omitted
> > > >> > > > > > > > modules in KIP-653 into log4j2.
> > > >> > > > > > > >
> > > >> > > > > > > > As you can see here, those two KIPs are the different
> > parts
> > > >> of
> > > >> > > the
> > > >> > > > > same
> > > >> > > > > > > > problem. I believe the community will have a good
> grasp
> > on
> > > >> why
> > > >> > > both
> > > >> > > > > KIPs
> > > >> > > > > > > > are best if released altogether.
> > > >> > > > > > > >
> > > >> > > > > > > > I will open the voting thread now, and please leave a
> > vote
> > > >> if
> > > >> > > you are
> > > >> > > > > > > > interested in this issue.
> > > >> > > > > > > >
> > > >> > > > > > > > Best,
> > > >> > > > > > > > Dongjin
> > > >> > > > > > > >
> > > >> > > > > > > > On Tue, Mar 2, 2021 at 5:00 PM Dongjin Lee <
> > > >> dong...@apache.org>
> > > >> > > > > wrote:
> > > >> > > > > > > >
> > > >> > > > > > > >> Hi Kafka dev,
> > > >> > > > > > > >>
> > > >> > > > > > > >> I would like to start the discussion of KIP-719: Add
> > Log4J2
> > > >> > > > > Appender.
> > > >> > > > > > > >>
> > > >> > > > > > > >>
> > > >> > > > > > > >>
> > > >> > > > >
> > > >> > >
> > > >>
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-719%3A+Add+Log4J2+Appender
> > > >> > > > > > > >>
> > > >> > > > > > > >> All kinds of feedbacks are greatly appreciated!
> > > >> > > > > > > >>
> > > >> > > > > > > >> Best,
> > > >> > > > > > > >> Dongjin
> > > >> > > > > > > >>
> > > >> > > > > > > >> --
> > > >> > > > > > > >> *Dongjin Lee*
> > > >> > > > > > > >>
> > > >> > > > > > > >> *A hitchhiker in the mathematical world.*
> > > >> > > > > > > >>
> > > >> > > > > > > >>
> > > >> > > > > > > >>
> > > >> > > > > > > >> *github: <http://goog_969573159/>
> > github.com/dongjinleekr
> > > >> > > > > > > >> <https://github.com/dongjinleekr>keybase:
> > > >> > > > > https://keybase.io/dongjinleekr
> > > >> > > > > > > >> <https://keybase.io/dongjinleekr>linkedin:
> > > >> > > > > kr.linkedin.com/in/dongjinleekr
> > > >> > > > > > > >> <https://kr.linkedin.com/in/dongjinleekr
> >speakerdeck:
> > > >> > > > > speakerdeck.com/dongjin
> > > >> > > > > > > >> <https://speakerdeck.com/dongjin>*
> > > >> > > > > > > >>
> > > >> > > > > > > >
> > > >> > > > > > > >
> > > >> > > > > > > > --
> > > >> > > > > > > > *Dongjin Lee*
> > > >> > > > > > > >
> > > >> > > > > > > > *A hitchhiker in the mathematical world.*
> > > >> > > > > > > >
> > > >> > > > > > > >
> > > >> > > > > > > >
> > > >> > > > > > > > *github: <http://goog_969573159/>
> > github.com/dongjinleekr
> > > >> > > > > > > > <https://github.com/dongjinleekr>keybase:
> > > >> > > > > https://keybase.io/dongjinleekr
> > > >> > > > > > > > <https://keybase.io/dongjinleekr>linkedin:
> > > >> > > > > kr.linkedin.com/in/dongjinleekr
> > > >> > > > > > > > <https://kr.linkedin.com/in/dongjinleekr>speakerdeck:
> > > >> > > > > speakerdeck.com/dongjin
> > > >> > > > > > > > <https://speakerdeck.com/dongjin>*
> > > >> > > > > > > >
> > > >> > > > > > >
> > > >> > > > > > >
> > > >> > > > > > > --
> > > >> > > > > > > *Dongjin Lee*
> > > >> > > > > > >
> > > >> > > > > > > *A hitchhiker in the mathematical world.*
> > > >> > > > > > >
> > > >> > > > > > >
> > > >> > > > > > >
> > > >> > > > > > > *github: <http://goog_969573159/>
> github.com/dongjinleekr
> > > >> > > > > > > <https://github.com/dongjinleekr>keybase:
> > > >> > > > > https://keybase.io/dongjinleekr
> > > >> > > > > > > <https://keybase.io/dongjinleekr>linkedin:
> > > >> > > > > kr.linkedin.com/in/dongjinleekr
> > > >> > > > > > > <https://kr.linkedin.com/in/dongjinleekr>speakerdeck:
> > > >> > > > > speakerdeck.com/dongjin
> > > >> > > > > > > <https://speakerdeck.com/dongjin>*
> > > >> > > > > > >
> > > >> > > > >
> > > >> > > >
> > > >> > > >
> > > >> > > > --
> > > >> > > > *Dongjin Lee*
> > > >> > > >
> > > >> > > > *A hitchhiker in the mathematical world.*
> > > >> > > >
> > > >> > > >
> > > >> > > >
> > > >> > > > *github: <http://goog_969573159/>github.com/dongjinleekr
> > > >> > > > <https://github.com/dongjinleekr>keybase:
> > > >> > > https://keybase.io/dongjinleekr
> > > >> > > > <https://keybase.io/dongjinleekr>linkedin:
> > > >> > > kr.linkedin.com/in/dongjinleekr
> > > >> > > > <https://kr.linkedin.com/in/dongjinleekr>speakerdeck:
> > > >> > > speakerdeck.com/dongjin
> > > >> > > > <https://speakerdeck.com/dongjin>*
> > > >> > >
> > > >> >
> > > >> >
> > > >> > --
> > > >> > *Dongjin Lee*
> > > >> >
> > > >> > *A hitchhiker in the mathematical world.*
> > > >> >
> > > >> >
> > > >> >
> > > >> > *github: <http://goog_969573159/>github.com/dongjinleekr
> > > >> > <https://github.com/dongjinleekr>keybase:
> > > >> https://keybase.io/dongjinleekr
> > > >> > <https://keybase.io/dongjinleekr>linkedin:
> > > >> kr.linkedin.com/in/dongjinleekr
> > > >> > <https://kr.linkedin.com/in/dongjinleekr>speakerdeck:
> > > >> speakerdeck.com/dongjin
> > > >> > <https://speakerdeck.com/dongjin>*
> > > >>
> > > >
> > > >
> > > > --
> > > > *Dongjin Lee*
> > > >
> > > > *A hitchhiker in the mathematical world.*
> > > >
> > > >
> > > >
> > > > *github: <http://goog_969573159/>github.com/dongjinleekr
> > > > <https://github.com/dongjinleekr>keybase:
> > https://keybase.io/dongjinleekr
> > > > <https://keybase.io/dongjinleekr>linkedin:
> > kr.linkedin.com/in/dongjinleekr
> > > > <https://kr.linkedin.com/in/dongjinleekr>speakerdeck:
> > speakerdeck.com/dongjin
> > > > <https://speakerdeck.com/dongjin>*
> > > >
> > >
> > >
> > > --
> > > *Dongjin Lee*
> > >
> > > *A hitchhiker in the mathematical world.*
> > >
> > >
> > >
> > > *github: <http://goog_969573159/>github.com/dongjinleekr
> > > <https://github.com/dongjinleekr>keybase:
> > https://keybase.io/dongjinleekr
> > > <https://keybase.io/dongjinleekr>linkedin:
> > kr.linkedin.com/in/dongjinleekr
> > > <https://kr.linkedin.com/in/dongjinleekr>speakerdeck:
> > speakerdeck.com/dongjin
> > > <https://speakerdeck.com/dongjin>*
> >
>
>
> --
> *Dongjin Lee*
>
> *A hitchhiker in the mathematical world.*
>
>
>
> *github: <http://goog_969573159/>github.com/dongjinleekr
> <https://github.com/dongjinleekr>keybase: https://keybase.io/dongjinleekr
> <https://keybase.io/dongjinleekr>linkedin: kr.linkedin.com/in/dongjinleekr
> <https://kr.linkedin.com/in/dongjinleekr>speakerdeck:
> speakerdeck.com/dongjin
> <https://speakerdeck.com/dongjin>*
>
--
========================
Okada Haruki
ocadar...@gmail.com
========================
