Hi Tom, 1. > I think you mean tools-log4j.properties there, right?
Thanks for reading carefully. Yes, you are right. It was an error. 2. > Can the log4j-appender log a warning about its own deprecation? That's a good suggestion. I hadn't thought of this part - adding a WARNing message to the Log4jAppender would help, like: > log4j-appender is deprecated and will be removed in a future release. For migration, please refer to the latest documentation. I just updated the proposal and the PR accordingly. Best, Dongjin On Fri, Jan 21, 2022 at 9:32 PM Tom Bentley <tbent...@redhat.com> wrote: > Hi Dongjin, > > Many thanks for the KIP. I have just a couple of minor points. > > 1. In the Proposed Changes section there is the sentence "For backward > compatibility, these tools will use the log4j configuration > file (tools-log4j2.properties) by default.", I think you mean > tools-log4j.properties there, right? > > 2. Can the log4j-appender log a warning about its own deprecation? The > "DEPRECATED: using log4j 1.x configuration. To use log4j 2.x > configuration," message is a bit confusing since it suggests that it's just > the use of 1.x configuration that's deprecated (which it is), but it's also > the use of the appender itself which is deprecated. > > Kind regards, > > Tom > > On Thu, 20 Jan 2022 at 05:01, Dongjin Lee <dong...@apache.org> wrote: > > > Hi all, > > > > I just filed the issue based on the discussion here: > > > > KAFKA-13604: Add pluggable logging framework support ( > > https://issues.apache.org/jira/browse/KAFKA-13604) > > > > Thanks for posing a great issue, Viktor and Haruki! > > > > Best, > > Dongjin > > > > On Thu, Jan 20, 2022 at 2:54 AM Viktor Somogyi-Vass > > <viktor.somo...@cloudera.com.invalid> wrote: > > > > > Hi folks, > > > > > > >a) I think this makes sense. But I think this shouldn't block this > > > KIP, it can be done after moving to log4j2. > > > > > > Absolutely. > > > > > > >However, this limitation may change in the future - slf4j will support > > > dynamic logging levels in 2.0: > > > > > > This would be awesome, let's keep an eye on this. > > > > > > >Kafka avoided all the log4shell vulnerabilities exactly because we > > DIDN'T > > > move to log4j 2.x. > > > > > > My first reaction was how lucky we are (and all Kafka users) that we > > didn't > > > have to do anything on that weekend! Blessed are the lazy. :) > > > > > > Viktor > > > > > > On Tue, Jan 18, 2022 at 5:16 PM Colin McCabe <cmcc...@apache.org> > wrote: > > > > > > > On Wed, Jan 12, 2022, at 02:37, Viktor Somogyi-Vass wrote: > > > > > Hi Dongjin, > > > > > > > > > > We're also looking into this matter as our stack was also affected > by > > > all > > > > > the log4j hell and users increasingly pushing us to upgrade to > log4j2 > > > or > > > > > logback because of the existing vulnerabilities in log4j1. > > > > > Regarding the points raised by Haruki: > > > > > > > > > > > > > I've heard the same thing from other people -- that there is now more > > > > interest in moving from log4j1.x to log4j2.x, after all the recent > > > > vulnerabilities in the latter. I found this a bit strange. Kafka > > avoided > > > > all the log4shell vulnerabilities exactly because we DIDN'T move to > > log4j > > > > 2.x. (Yes, I am aware that there is a longstanding vulnerability in > > that > > > > one log sink in log4j 1.x, but you can just not use that one.) > > > > > > > > I haven't thought about this very hard. Maybe it's still a good idea > to > > > > move to log4j2. But it's odd that nobody is commenting about how in > > this > > > > case, not updating actually prevented a major security incident for > > > Kafka. > > > > > > > > best, > > > > Colin > > > > > > > > > > > > > > a) In my opinion the best would be to make the dynamic logger > support > > > > > (Log4jController and LoggingResource) pluggable for log4j2 and > > logback > > > > (so > > > > > an interface could be used to define the dynamic logging control > > > methods > > > > > and a config to specify the implementation). That way we're not > bound > > > to > > > > > either logback or log4j and seems like a low-effort thing to do. > > > > > Additionally this could be used in Connect too in LoggingResource. > > > > > > > > > > b) I think testing dependencies aren't that important from the user > > > > > perspective, it's fine to either use log4j2 or logback, whichever > is > > > > > easier. Kafka is either used from the distribution (tgz) or pulled > in > > > > > through maven, but test dependencies shouldn't be exposed to the > > world. > > > > > > > > > > c) I would support deprecating the appender in favor of the log4j2 > > > Kafka > > > > > appender. VerifiableLog4jAppender is intended as a testing tool > > anyway, > > > > so > > > > > I think it's less important to change this to logback. > > > > > > > > > > Future vulnerabilities will always be found in either logback or > > log4j2 > > > > or > > > > > any other logging framework, so I think the safest approach is to > > allow > > > > > users to choose their implementation, while in tests I think we're > > free > > > > to > > > > > use whatever we want as that shouldn't be constrained by > > > vulnerabilities. > > > > > > > > > > Viktor > > > > > > > > > > On Thu, Dec 23, 2021 at 9:37 AM Haruki Okada <ocadar...@gmail.com> > > > > wrote: > > > > > > > > > >> Thanks for the clarification. > > > > >> > > > > >> About 2, I wan't aware of those concerns. > > > > >> Let me check them first. > > > > >> > > > > >> > > > > >> Thanks, > > > > >> > > > > >> 2021年12月23日(木) 13:37 Dongjin Lee <dong...@apache.org>: > > > > >> > > > > >> > Hi Haruki, > > > > >> > > > > > >> > > > > > >> > Thanks for organizing the issue. > > > > >> > > > > > >> > > > > > >> > If the community prefers logback, I will gladly change the > > > dependency > > > > and > > > > >> > update the PR. However, it has the following issues: > > > > >> > > > > > >> > > > > > >> > 1. The log4j2 vulnerabilities seem mostly fixed, and KIP-653 + > > > KIP-719 > > > > >> are > > > > >> > not released yet. So, using log4j2 (whose recent update pace is > so > > > > high) > > > > >> > will not affect the users. > > > > >> > > > > > >> > > > > > >> > 2. To switch to logback, the following features should be > > reworked: > > > > >> > > > > > >> > > > > > >> > a. Dynamic logger level configuration (core, connect) > > > > >> > > > > > >> > b. Logging tests (streams) > > > > >> > > > > > >> > c. Kafka Appender (tools) > > > > >> > > > > > >> > > > > > >> > a and b are the most challenging ones since there is little > > > > documentation > > > > >> > on how to do this, so it requires analyzing the implementation > > > itself. > > > > >> > (what I actually did with log4j2) About c, logback does not > > provide > > > a > > > > >> Kafka > > > > >> > Appender so we have to provide an equivalent. > > > > >> > > > > > >> > > > > > >> > It is why I prefer to use log4j2. How do you think? > > > > >> > > > > > >> > > > > > >> > Thanks, > > > > >> > > > > > >> > Dongjin > > > > >> > > > > > >> > > > > > >> > On Thu, Dec 23, 2021 at 9:01 AM Haruki Okada < > ocadar...@gmail.com > > > > > > > >> wrote: > > > > >> > > > > > >> > > 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 > > > > >> > > ======================== > > > > >> > > > > > > >> > > > > > >> > > > > > >> > -- > > > > >> > *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 > > > > >> ======================== > > > > >> > > > > > > > > > > > > > -- > > *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>*
