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>* >
