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> On 01/23/2021 4:14 AM Guozhang Wang <wangg...@gmail.com> wrote:
>
>
> Thanks Boyang, yes I think I was confused about the different handling of
> two abortTxn calls, and now I get it was not intentional. I think I do not
> have more concerns.
>
> On Fri, Jan 22, 2021 at 1:12 PM Boyang Chen <reluctanthero...@gmail.com>
> wrote:
>
> > Thanks for the clarification Guozhang, I got your point that we want to
> > have a consistent handling of fatal exceptions being thrown from the
> > abortTxn. I modified the current template to move the fatal exception
> > try-catch outside of the processing loop to make sure we could get a chance
> > to close consumer/producer modules. Let me know what you think.
> >
> > Best,
> > Boyang
> >
> > On Fri, Jan 22, 2021 at 11:05 AM Boyang Chen <reluctanthero...@gmail.com>
> > wrote:
> >
> > > My understanding is that abortTransaction would only throw when the
> > > producer is in fatal state. For CommitFailed, the producer should still
> > be
> > > in the abortable error state, so that abortTransaction call would not
> > throw.
> > >
> > > On Fri, Jan 22, 2021 at 11:02 AM Guozhang Wang <wangg...@gmail.com>
> > wrote:
> > >
> > >> Or are you going to maintain some internal state such that, the
> > >> `abortTransaction` in the catch block would never throw again?
> > >>
> > >> On Fri, Jan 22, 2021 at 11:01 AM Guozhang Wang <wangg...@gmail.com>
> > >> wrote:
> > >>
> > >> > Hi Boyang/Jason,
> > >> >
> > >> > I've also thought about this (i.e. using CommitFailed for all
> > >> non-fatal),
> > >> > but what I'm pondering is that, in the catch (CommitFailed) block,
> > what
> > >> > would happen if the `producer.abortTransaction();` throws again?
> > should
> > >> > that be captured as a fatal and cause the client to close again.
> > >> >
> > >> > If yes, then naively the pattern would be:
> > >> >
> > >> > ...
> > >> > catch (CommitFailedException e) {
> > >> > // Transaction commit failed with abortable error, user could
> > >> reset
> > >> > // the application state and resume with a new transaction.
> > The
> > >> > root
> > >> > // cause was wrapped in the thrown exception.
> > >> > resetToLastCommittedPositions(consumer);
> > >> > try {
> > >> > producer.abortTransaction();
> > >> > } catch (KafkaException e) {
> > >> > producer.close();
> > >> > consumer.close();
> > >> > throw e;
> > >> > }
> > >> > } catch (KafkaException e) {
> > >> > producer.close();
> > >> > consumer.close();
> > >> > throw e;
> > >> > }
> > >> > ...
> > >> >
> > >> > Guozhang
> > >> >
> > >> > On Fri, Jan 22, 2021 at 10:47 AM Boyang Chen <
> > >> reluctanthero...@gmail.com>
> > >> > wrote:
> > >> >
> > >> >> Hey Guozhang,
> > >> >>
> > >> >> Jason and I were discussing the new API offline and decided to take
> > >> >> another
> > >> >> approach. Firstly, the reason not to invent a new API with returned
> > >> >> boolean
> > >> >> flag is for compatibility consideration, since old EOS code would not
> > >> know
> > >> >> that a given transaction commit was failed internally as they don't
> > >> listen
> > >> >> to the output flag. Our proposed alternative solution is to let
> > >> >> *commitTransaction
> > >> >> throw CommitFailedException whenever the commit failed with non-fatal
> > >> >> exception*, so that on the caller side the handling logic becomes:
> > >> >>
> > >> >> try {
> > >> >> if (shouldCommit) {
> > >> >> producer.commitTransaction();
> > >> >> } else {
> > >> >> resetToLastCommittedPositions(consumer);
> > >> >> producer.abortTransaction();
> > >> >> }
> > >> >> } catch (CommitFailedException e) {
> > >> >> // Transaction commit failed with abortable error, user could
> > >> >> reset
> > >> >> // the application state and resume with a new transaction.
> > The
> > >> >> root
> > >> >> // cause was wrapped in the thrown exception.
> > >> >> resetToLastCommittedPositions(consumer);
> > >> >> producer.abortTransaction();
> > >> >> } catch (KafkaException e) {
> > >> >> producer.close();
> > >> >> consumer.close();
> > >> >> throw e;
> > >> >> }
> > >> >>
> > >> >> This approach looks cleaner as all exception types other than
> > >> CommitFailed
> > >> >> will doom to be fatal, which is very easy to adopt for users. In the
> > >> >> meantime, we still maintain the commitTxn behavior to throw instead
> > of
> > >> >> silently failing.
> > >> >>
> > >> >> In addition, we decided to drop the recommendation to handle
> > >> >> TimeoutException and leave it to the users to make the call. The
> > >> downside
> > >> >> for blindly calling abortTxn upon timeout is that we could result in
> > an
> > >> >> illegal state when the commit was already successful on the broker
> > >> >> side. Without a good guarantee on the outcome, overcomplicating the
> > >> >> template should not be encouraged IMHO.
> > >> >>
> > >> >> Let me know your thoughts on the new approach here, thank you!
> > >> >>
> > >> >> Best,
> > >> >> Boyang
> > >> >>
> > >> >> On Tue, Jan 19, 2021 at 11:11 AM Guozhang Wang <wangg...@gmail.com>
> > >> >> wrote:
> > >> >>
> > >> >> > Thanks for your clarification on 2)/3), that makes sense.
> > >> >> >
> > >> >> > On Tue, Jan 19, 2021 at 10:16 AM Boyang Chen <
> > >> >> reluctanthero...@gmail.com>
> > >> >> > wrote:
> > >> >> >
> > >> >> > > Thanks for the input Guozhang, replied inline.
> > >> >> > >
> > >> >> > > On Mon, Jan 18, 2021 at 8:57 PM Guozhang Wang <
> > wangg...@gmail.com>
> > >> >> > wrote:
> > >> >> > >
> > >> >> > > > Hello Boyang,
> > >> >> > > >
> > >> >> > > > Thanks for the updated KIP. I read it again and have the
> > >> following
> > >> >> > > > thoughts:
> > >> >> > > >
> > >> >> > > > 0. I'm a bit concerned that if commitTxn does not throw any
> > >> >> non-fatal
> > >> >> > > > exception, and instead we rely on the subsequent beginTxn call
> > to
> > >> >> > throw,
> > >> >> > > it
> > >> >> > > > may violate some callers with a pattern that relying on
> > >> commitTxn to
> > >> >> > > > succeed to make some non-rollback operations. For example:
> > >> >> > > >
> > >> >> > > > beginTxn()
> > >> >> > > > // do some read-write on my local DB
> > >> >> > > > commitTxn()
> > >> >> > > > // if commitTxn succeeds, then commit the DB
> > >> >> > > >
> > >> >> > > > -------------
> > >> >> > > >
> > >> >> > > > The issue is that, committing DB is a non-rollback operation,
> > and
> > >> >> users
> > >> >> > > may
> > >> >> > > > just rely on commitTxn to return without error to make this
> > >> >> > non-rollback
> > >> >> > > > call. Of course we can just claim this pattern is not
> > legitimate
> > >> >> and is
> > >> >> > > not
> > >> >> > > > the right way of doing things, but many users may naturally
> > adopt
> > >> >> this
> > >> >> > > > pattern.
> > >> >> > > >
> > >> >> > > > So maybe we should still let commitTxn also throw non-fatal
> > >> >> exceptions,
> > >> >> > > in
> > >> >> > > > which case we would then call abortTxn again.
> > >> >> > > >
> > >> >> > > > But if we do this, the pattern becomes:
> > >> >> > > >
> > >> >> > > > try {
> > >> >> > > > beginTxn()
> > >> >> > > > // do something
> > >> >> > > > } catch (Exception) {
> > >> >> > > > shouldCommit = false;
> > >> >> > > > }
> > >> >> > > >
> > >> >> > > > if (shouldCommit) {
> > >> >> > > > try {
> > >> >> > > > commitTxn()
> > >> >> > > > } catch (...) { // enumerate all fatal exceptions
> > >> >> > > > shutdown()
> > >> >> > > > } catch (KafkaException) {
> > >> >> > > > // non-fatal
> > >> >> > > > shouldCommit = false;
> > >> >> > > > }
> > >> >> > > > }
> > >> >> > > >
> > >> >> > > > if (!shouldCommit && running()) {
> > >> >> > > > try {
> > >> >> > > > abortTxn()
> > >> >> > > > } catch (KafkaException) {
> > >> >> > > > // only throw fatal
> > >> >> > > > shutdown()
> > >> >> > > > }
> > >> >> > > > }
> > >> >> > > >
> > >> >> > > > ---------------------
> > >> >> > > >
> > >> >> > > > Which is much more complicated.
> > >> >> > > >
> > >> >> > > > Thank makes me think, the alternative we have discussed offline
> > >> may
> > >> >> be
> > >> >> > > > better: let commitTxn() to return a boolean flag.
> > >> >> > > >
> > >> >> > > > * If it returns true, it means the commit succeeded. Users can
> > >> >> > > comfortably
> > >> >> > > > continue and do any external non-rollback operations if they
> > >> like.
> > >> >> > > > * If it returns false, it means the commit failed with
> > non-fatal
> > >> >> error
> > >> >> > > *AND
> > >> >> > > > the txn has been aborted*. Users do not need to call abortTxn
> > >> again.
> > >> >> > > > * If it throws, then it means fatal errors. Users should shut
> > >> down
> > >> >> the
> > >> >> > > > client.
> > >> >> > > >
> > >> >> > > > In this case, the pattern becomes:
> > >> >> > > >
> > >> >> > > > try {
> > >> >> > > > beginTxn()
> > >> >> > > > // do something
> > >> >> > > > } catch (Exception) {
> > >> >> > > > shouldCommit = false;
> > >> >> > > > }
> > >> >> > > >
> > >> >> > > > try {
> > >> >> > > > if (shouldCommit) {
> > >> >> > > > commitSucceeded = commitTxn()
> > >> >> > > > } else {
> > >> >> > > > // reset offsets, rollback operations, etc
> > >> >> > > > abortTxn()
> > >> >> > > > }
> > >> >> > > > } catch (KafkaException) {
> > >> >> > > > // only throw fatal
> > >> >> > > > shutdown()
> > >> >> > > > }
> > >> >> > > >
> > >> >> > > > if (commitSucceeded)
> > >> >> > > > // do other non-rollbackable things
> > >> >> > > > else
> > >> >> > > > // reset offsets, rollback operations, etc
> > >> >> > > >
> > >> >> > > > -------------------------
> > >> >> > > >
> > >> >> > > > Of course, if we want to have better visibility into what
> > caused
> > >> the
> > >> >> > > commit
> > >> >> > > > to fail and txn to abort. We can let the return type be an enum
> > >> >> instead
> > >> >> > > of
> > >> >> > > > a flag. But my main idea is to still let the commitTxn be the
> > >> final
> > >> >> > point
> > >> >> > > > users can tell whether this txn succeeded or not, instead of
> > >> >> relying on
> > >> >> > > the
> > >> >> > > > next beginTxn() call.
> > >> >> > > >
> > >> >> > > > I agree that adding a boolean flag is indeed useful in this
> > case.
> > >> >> Will
> > >> >> > > update the KIP.
> > >> >> > >
> > >> >> > > 1. Re: "while maintaining the behavior to throw fatal exception
> > in
> > >> >> raw"
> > >> >> > not
> > >> >> > > > sure what do you mean by "throw" here. Are you proposing the
> > >> >> callback
> > >> >> > > would
> > >> >> > > > *pass* (not throw) in any fatal exceptions when triggered
> > without
> > >> >> > > wrapping?
> > >> >> > > >
> > >> >> > > > Yes, I want to say *pass*, the benefit is to make the end
> > user's
> > >> >> > > expectation consistent
> > >> >> > > regarding exception handling.
> > >> >> > >
> > >> >> > >
> > >> >> > > > 2. I'm not sure I understand the claim regarding the callback
> > >> that
> > >> >> "In
> > >> >> > > EOS
> > >> >> > > > setup, it is not required to handle the exception". Are you
> > >> >> proposing
> > >> >> > > that,
> > >> >> > > > e.g. in Streams, we do not try to handle any exceptions if EOS
> > is
> > >> >> > enabled
> > >> >> > > > in the callback anymore, but just let commitTxn() itself to
> > fail
> > >> to
> > >> >> be
> > >> >> > > > notified about the problem? Personally I think in Streams we
> > >> should
> > >> >> > just
> > >> >> > > > make the handling logic of the callback to be consistent
> > >> regardless
> > >> >> of
> > >> >> > > the
> > >> >> > > > EOS settings (today we have different logic depending on this
> > >> logic,
> > >> >> > > which
> > >> >> > > > I think could be unified as well).
> > >> >> > > >
> > >> >> > > > My idea originates from the claim on send API:
> > >> >> > > "When used as part of a transaction, it is not necessary to
> > define
> > >> a
> > >> >> > > callback or check the result of the future in order to detect
> > >> errors
> > >> >> > from
> > >> >> > > <code>send</code>. "
> > >> >> > > My understanding is that for EOS, the exception will be detected
> > by
> > >> >> > calling
> > >> >> > > transactional APIs either way, so it is a duplicate handling to
> > >> track
> > >> >> > > all the sendExceptions in RecordCollector. However, I looked up
> > >> >> > > sendException is being used today as follow:
> > >> >> > >
> > >> >> > > 1. Pass to "ProductionExceptionHandler" for any default or
> > >> customized
> > >> >> > > exception handler to handle
> > >> >> > > 2. Stop collecting offset info or new exceptions
> > >> >> > > 3. Check and rethrow exceptions in close(), flush() or new send()
> > >> >> calls
> > >> >> > >
> > >> >> > > To my understanding, we should still honor the commitment to #1
> > for
> > >> >> any
> > >> >> > > user customized implementation. The #2 does not really affect our
> > >> >> > decision
> > >> >> > > upon EOS. The #3 here is still valuable as it could help us fail
> > >> fast
> > >> >> in
> > >> >> > > new send() instead of waiting to later stage of processing. In
> > that
> > >> >> > sense,
> > >> >> > > I agree we should continue to record send exceptions even under
> > EOS
> > >> >> case
> > >> >> > to
> > >> >> > > ensure the strength of stream side Producer logic. On the safer
> > >> side,
> > >> >> we
> > >> >> > no
> > >> >> > > longer need to wrap certain fatal exceptions like ProducerFenced
> > as
> > >> >> > > TaskMigrated, since they should not crash the stream thread if
> > >> thrown
> > >> >> in
> > >> >> > > raw format, once we adopt the new processing model in the send
> > >> phase.
> > >> >> > >
> > >> >> > >
> > >> >> > > >
> > >> >> > > > Guozhang
> > >> >> > > >
> > >> >> > > >
> > >> >> > > >
> > >> >> > > > On Thu, Dec 17, 2020 at 8:42 PM Boyang Chen <
> > >> >> > reluctanthero...@gmail.com>
> > >> >> > > > wrote:
> > >> >> > > >
> > >> >> > > > > Thanks for everyone's feedback so far. I have polished the
> > KIP
> > >> >> after
> > >> >> > > > > offline discussion with some folks working on EOS to make the
> > >> >> > exception
> > >> >> > > > > handling more lightweight. The essential change is that we
> > are
> > >> not
> > >> >> > > > > inventing a new intermediate exception type, but instead
> > >> >> separating a
> > >> >> > > > full
> > >> >> > > > > transaction into two phases:
> > >> >> > > > >
> > >> >> > > > > 1. The data transmission phase
> > >> >> > > > > 2. The commit phase
> > >> >> > > > >
> > >> >> > > > > This way for any exception thrown from phase 1, will be an
> > >> >> indicator
> > >> >> > in
> > >> >> > > > > phase 2 whether we should do commit or abort, and from now on
> > >> >> > > > > `commitTransaction` should only throw fatal exceptions,
> > >> similar to
> > >> >> > > > > `abortTransaction`, so that any KafkaException caught in the
> > >> >> commit
> > >> >> > > phase
> > >> >> > > > > will be definitely fatal to crash the app. For more advanced
> > >> users
> > >> >> > such
> > >> >> > > > as
> > >> >> > > > > Streams, we have the ability to further wrap selected types
> > of
> > >> >> fatal
> > >> >> > > > > exceptions to trigger task migration if necessary.
> > >> >> > > > >
> > >> >> > > > > More details in the KIP, feel free to take another look,
> > >> thanks!
> > >> >> > > > >
> > >> >> > > > > On Thu, Dec 17, 2020 at 8:36 PM Boyang Chen <
> > >> >> > > reluctanthero...@gmail.com>
> > >> >> > > > > wrote:
> > >> >> > > > >
> > >> >> > > > > > Thanks Bruno for the feedback.
> > >> >> > > > > >
> > >> >> > > > > > On Mon, Dec 7, 2020 at 5:26 AM Bruno Cadonna <
> > >> >> br...@confluent.io>
> > >> >> > > > wrote:
> > >> >> > > > > >
> > >> >> > > > > >> Thanks Boyang for the KIP!
> > >> >> > > > > >>
> > >> >> > > > > >> Like Matthias, I do also not know the producer internal
> > well
> > >> >> > enough
> > >> >> > > to
> > >> >> > > > > >> comment on the categorization. However, I think having a
> > >> super
> > >> >> > > > exception
> > >> >> > > > > >> (e.g. RetriableException) that encodes if an exception is
> > >> >> fatal
> > >> >> > or
> > >> >> > > > not
> > >> >> > > > > >> is cleaner, better understandable and less error-prone,
> > >> because
> > >> >> > > > ideally
> > >> >> > > > > >> when you add a new non-fatal exception in future you just
> > >> need
> > >> >> to
> > >> >> > > > think
> > >> >> > > > > >> about letting it inherit from the super exception and all
> > >> the
> > >> >> rest
> > >> >> > > of
> > >> >> > > > > >> the code will just behave correctly without the need to
> > wrap
> > >> >> the
> > >> >> > new
> > >> >> > > > > >> exception into another exception each time it is thrown
> > >> (maybe
> > >> >> it
> > >> >> > is
> > >> >> > > > > >> thrown at different location in the code).
> > >> >> > > > > >>
> > >> >> > > > > >> As far as I understand the following statement from your
> > >> >> previous
> > >> >> > > > e-mail
> > >> >> > > > > >> is the reason that currently such a super exception is not
> > >> >> > possible:
> > >> >> > > > > >>
> > >> >> > > > > >> "Right now we have RetriableException type, if we are
> > going
> > >> to
> > >> >> > add a
> > >> >> > > > > >> `ProducerRetriableException` type, we have to put this new
> > >> >> > interface
> > >> >> > > > as
> > >> >> > > > > >> the parent of the RetriableException, because not all
> > thrown
> > >> >> > > non-fatal
> > >> >> > > > > >> exceptions are `retriable` in general for producer"
> > >> >> > > > > >>
> > >> >> > > > > >>
> > >> >> > > > > >> In the list of exceptions in your KIP, I found non-fatal
> > >> >> > exceptions
> > >> >> > > > that
> > >> >> > > > > >> do not inherit from RetriableException. I guess those are
> > >> the
> > >> >> ones
> > >> >> > > you
> > >> >> > > > > >> are referring to in your statement:
> > >> >> > > > > >>
> > >> >> > > > > >> InvalidProducerEpochException
> > >> >> > > > > >> InvalidPidMappingException
> > >> >> > > > > >> TransactionAbortedException
> > >> >> > > > > >>
> > >> >> > > > > >> All of those exceptions are non-fatal and do not inherit
> > >> from
> > >> >> > > > > >> RetriableException. Is there a reason for that? If they
> > >> >> depended
> > >> >> > > from
> > >> >> > > > > >> RetriableException we would be a bit closer to a super
> > >> >> exception I
> > >> >> > > > > >> mention above.
> > >> >> > > > > >>
> > >> >> > > > > >> The reason is that sender may catch those exceptions in
> > the
> > >> >> > > > > > ProduceResponse, and it currently does infinite
> > >> >> > > > > > retries on RetriableException. To make sure we could
> > trigger
> > >> the
> > >> >> > > > > > abortTransaction() by catching non-fatal thrown
> > >> >> > > > > > exceptions and reinitialize the txn state, we chose not to
> > >> let
> > >> >> > those
> > >> >> > > > > > exceptions inherit RetriableException so that
> > >> >> > > > > > they won't cause infinite retry on sender.
> > >> >> > > > > >
> > >> >> > > > > >
> > >> >> > > > > >> With OutOfOrderSequenceException and
> > >> >> UnknownProducerIdException, I
> > >> >> > > > think
> > >> >> > > > > >> to understand that their fatality depends on the type
> > (i.e.
> > >> >> > > > > >> configuration) of the producer. That makes it difficult to
> > >> >> have a
> > >> >> > > > super
> > >> >> > > > > >> exception that encodes the retriability as mentioned
> > above.
> > >> >> Would
> > >> >> > it
> > >> >> > > > be
> > >> >> > > > > >> possible to introduce exceptions that inherit from
> > >> >> > > RetriableException
> > >> >> > > > > >> and that are thrown when those exceptions are caught from
> > >> the
> > >> >> > > brokers
> > >> >> > > > > >> and the type of the producer is such that the exceptions
> > are
> > >> >> > > > retriable?
> > >> >> > > > > >>
> > >> >> > > > > >> Yea, I think in general the exception type mixing is
> > >> difficult
> > >> >> to
> > >> >> > > get
> > >> >> > > > > > them all right. I have already proposed another solution
> > >> based
> > >> >> on
> > >> >> > my
> > >> >> > > > > > offline discussion with some folks working on EOS
> > >> >> > > > > > to make the handling more straightforward for end users
> > >> without
> > >> >> the
> > >> >> > > > need
> > >> >> > > > > > to distinguish exception fatality.
> > >> >> > > > > >
> > >> >> > > > > >> Best,
> > >> >> > > > > >> Bruno
> > >> >> > > > > >>
> > >> >> > > > > >>
> > >> >> > > > > >> On 04.12.20 19:34, Guozhang Wang wrote:
> > >> >> > > > > >> > Thanks Boyang for the proposal! I made a pass over the
> > >> list
> > >> >> and
> > >> >> > > here
> > >> >> > > > > are
> > >> >> > > > > >> > some thoughts:
> > >> >> > > > > >> >
> > >> >> > > > > >> > 0) Although this is not part of the public API, I think
> > we
> > >> >> > should
> > >> >> > > > make
> > >> >> > > > > >> sure
> > >> >> > > > > >> > that the suggested pattern (i.e. user can always call
> > >> >> abortTxn()
> > >> >> > > > when
> > >> >> > > > > >> > handling non-fatal errors) are indeed supported. E.g. if
> > >> the
> > >> >> txn
> > >> >> > > is
> > >> >> > > > > >> already
> > >> >> > > > > >> > aborted by the broker side, then users can still call
> > >> >> abortTxn
> > >> >> > > which
> > >> >> > > > > >> would
> > >> >> > > > > >> > not throw another exception but just be treated as a
> > >> no-op.
> > >> >> > > > > >> >
> > >> >> > > > > >> > 1) *ConcurrentTransactionsException*: I think this error
> > >> can
> > >> >> > also
> > >> >> > > be
> > >> >> > > > > >> > returned but not documented yet. This should be a
> > >> non-fatal
> > >> >> > error.
> > >> >> > > > > >> >
> > >> >> > > > > >> > 2) *InvalidTxnStateException*: this error is returned
> > from
> > >> >> > broker
> > >> >> > > > when
> > >> >> > > > > >> txn
> > >> >> > > > > >> > state transition failed (e.g. it is trying to transit to
> > >> >> > > > > complete-commit
> > >> >> > > > > >> > while the current state is not prepare-commit). This
> > error
> > >> >> could
> > >> >> > > > > >> indicates
> > >> >> > > > > >> > a bug on the client internal code or the broker code,
> > OR a
> > >> >> user
> > >> >> > > > error
> > >> >> > > > > >> --- a
> > >> >> > > > > >> > similar error is ConcurrentTransactionsException, i.e.
> > if
> > >> >> Kafka
> > >> >> > is
> > >> >> > > > > >> bug-free
> > >> >> > > > > >> > these exceptions would only be returned if users try to
> > do
> > >> >> > > something
> > >> >> > > > > >> wrong,
> > >> >> > > > > >> > e.g. calling abortTxn right after a commitTxn, etc. So
> > I'm
> > >> >> > > thinking
> > >> >> > > > it
> > >> >> > > > > >> > should be a non-fatal error instead of a fatal error,
> > >> wdyt?
> > >> >> > > > > >> >
> > >> >> > > > > >> > 3) *KafkaException*: case i "indicates fatal
> > transactional
> > >> >> > > sequence
> > >> >> > > > > >> > (Fatal)", this is a bit conflicting with the
> > >> >> > > > *OutOfSequenceException*
> > >> >> > > > > >> that
> > >> >> > > > > >> > is treated as non-fatal. I guess your proposal is that
> > >> >> > > > > >> > OutOfOrderSequenceException would be treated either as
> > >> fatal
> > >> >> > with
> > >> >> > > > > >> > transactional producer, or non-fatal with idempotent
> > >> >> producer,
> > >> >> > is
> > >> >> > > > that
> > >> >> > > > > >> > right? If the producer is only configured with
> > idempotency
> > >> >> but
> > >> >> > not
> > >> >> > > > > >> > transaction, then throwing a
> > >> >> TransactionStateCorruptedException
> > >> >> > > for
> > >> >> > > > > >> > non-fatal errors would be confusing since users are not
> > >> using
> > >> >> > > > > >> transactions
> > >> >> > > > > >> > at all.. So I suggest we always throw
> > >> OutOfSequenceException
> > >> >> > as-is
> > >> >> > > > > (i.e.
> > >> >> > > > > >> > not wrapped) no matter how the producer is configured,
> > and
> > >> >> let
> > >> >> > the
> > >> >> > > > > >> caller
> > >> >> > > > > >> > decide how to handle it based on whether it is only
> > >> >> idempotent
> > >> >> > or
> > >> >> > > > > >> > transactional itself.
> > >> >> > > > > >> >
> > >> >> > > > > >> > 4) Besides all the txn APIs, the `send()` callback /
> > >> future
> > >> >> can
> > >> >> > > also
> > >> >> > > > > >> throw
> > >> >> > > > > >> > txn-related exceptions, I think this KIP should also
> > cover
> > >> >> this
> > >> >> > > API
> > >> >> > > > as
> > >> >> > > > > >> well?
> > >> >> > > > > >> >
> > >> >> > > > > >> > 5) This is related to 1/2) above: sometimes those
> > >> non-fatal
> > >> >> > errors
> > >> >> > > > > like
> > >> >> > > > > >> > ConcurrentTxn or InvalidTxnState are not due to the
> > state
> > >> >> being
> > >> >> > > > > >> corrupted
> > >> >> > > > > >> > at the broker side, but maybe users are doing something
> > >> >> wrong.
> > >> >> > So
> > >> >> > > > I'm
> > >> >> > > > > >> > wondering if we should further distinguish those
> > non-fatal
> > >> >> > errors
> > >> >> > > > > >> between
> > >> >> > > > > >> > a) those that are caused by Kafka itself, e.g. a broker
> > >> timed
> > >> >> > out
> > >> >> > > > and
> > >> >> > > > > >> > aborted a txn and later an endTxn request is received,
> > >> and b)
> > >> >> > the
> > >> >> > > > > user's
> > >> >> > > > > >> > API call pattern is incorrect, causing the request to be
> > >> >> > rejected
> > >> >> > > > with
> > >> >> > > > > >> an
> > >> >> > > > > >> > error code from the broker.
> > >> >> *TransactionStateCorruptedException*
> > >> >> > > > feels
> > >> >> > > > > >> to
> > >> >> > > > > >> > me more like for case a), but not case b).
> > >> >> > > > > >> >
> > >> >> > > > > >> >
> > >> >> > > > > >> > Guozhang
> > >> >> > > > > >> >
> > >> >> > > > > >> >
> > >> >> > > > > >> > On Wed, Dec 2, 2020 at 4:50 PM Boyang Chen <
> > >> >> > > > > reluctanthero...@gmail.com>
> > >> >> > > > > >> > wrote:
> > >> >> > > > > >> >
> > >> >> > > > > >> >> Thanks Matthias, I think your proposal makes sense as
> > >> well,
> > >> >> on
> > >> >> > > the
> > >> >> > > > > pro
> > >> >> > > > > >> side
> > >> >> > > > > >> >> we could have a universally agreed exception type to be
> > >> >> caught
> > >> >> > by
> > >> >> > > > the
> > >> >> > > > > >> user,
> > >> >> > > > > >> >> without having an extra layer on top of the actual
> > >> >> exceptions.
> > >> >> > I
> > >> >> > > > > could
> > >> >> > > > > >> see
> > >> >> > > > > >> >> some issue on downsides:
> > >> >> > > > > >> >>
> > >> >> > > > > >> >> 1. The exception hierarchy will be more complex. Right
> > >> now
> > >> >> we
> > >> >> > > have
> > >> >> > > > > >> >> RetriableException type, if we are going to add a
> > >> >> > > > > >> >> `ProducerRetriableException` type, we have to put this
> > >> new
> > >> >> > > > interface
> > >> >> > > > > >> as the
> > >> >> > > > > >> >> parent of the RetriableException, because not all
> > thrown
> > >> >> > > non-fatal
> > >> >> > > > > >> >> exceptions are `retriable` in general for producer, for
> > >> >> example
> > >> >> > > > > >> >> <
> > >> >> > > > > >> >>
> > >> >> > > > > >>
> > >> >> > > > >
> > >> >> > > >
> > >> >> > >
> > >> >> >
> > >> >>
> > >>
> > https://github.com/apache/kafka/blob/e275742f850af4a1b79b0d1bd1ac9a1d2e89c64e/clients/src/main/java/org/apache/kafka/clients/producer/internals/Sender.java#L745
> > >> >> > > > > >> >>> .
> > >> >> > > > > >> >> We could have an empty interface
> > >> >> `ProducerRetriableException`
> > >> >> > to
> > >> >> > > > let
> > >> >> > > > > >> all
> > >> >> > > > > >> >> the thrown exceptions implement for sure, but it's a
> > bit
> > >> >> > > unorthodox
> > >> >> > > > > in
> > >> >> > > > > >> the
> > >> >> > > > > >> >> way we deal with exceptions in general.
> > >> >> > > > > >> >>
> > >> >> > > > > >> >> 2. There are cases where we throw a KafkaException
> > >> wrapping
> > >> >> > > another
> > >> >> > > > > >> >> KafkaException as either fatal or non-fatal. If we use
> > an
> > >> >> > > interface
> > >> >> > > > > to
> > >> >> > > > > >> >> solve #1, it is also required to implement another
> > >> bloated
> > >> >> > > > exception
> > >> >> > > > > >> class
> > >> >> > > > > >> >> which could replace KafkaException type, as we couldn't
> > >> mark
> > >> >> > > > > >> KafkaException
> > >> >> > > > > >> >> as retriable for sure.
> > >> >> > > > > >> >>
> > >> >> > > > > >> >> 3. In terms of the encapsulation, wrapping means we
> > could
> > >> >> limit
> > >> >> > > the
> > >> >> > > > > >> scope
> > >> >> > > > > >> >> of affection to the producer only, which is important
> > >> since
> > >> >> we
> > >> >> > > > don't
> > >> >> > > > > >> want
> > >> >> > > > > >> >> shared exception types to implement a producer-related
> > >> >> > interface,
> > >> >> > > > > such
> > >> >> > > > > >> >> as UnknownTopicOrPartitionException.
> > >> >> > > > > >> >>
> > >> >> > > > > >> >> Best,
> > >> >> > > > > >> >> Boyang
> > >> >> > > > > >> >>
> > >> >> > > > > >> >> On Wed, Dec 2, 2020 at 3:38 PM Matthias J. Sax <
> > >> >> > mj...@apache.org
> > >> >> > > >
> > >> >> > > > > >> wrote:
> > >> >> > > > > >> >>
> > >> >> > > > > >> >>> Thanks for the KIP Boyang!
> > >> >> > > > > >> >>>
> > >> >> > > > > >> >>> Overall, categorizing exceptions makes a lot of sense.
> > >> As I
> > >> >> > > don't
> > >> >> > > > > know
> > >> >> > > > > >> >>> the producer internals well enough, I cannot comment
> > on
> > >> the
> > >> >> > > > > >> >>> categorization in detail though.
> > >> >> > > > > >> >>>
> > >> >> > > > > >> >>> What I am wondering is, if we should introduce an
> > >> exception
> > >> >> > > > > interface
> > >> >> > > > > >> >>> that non-fatal exception would implement instead of
> > >> >> creating a
> > >> >> > > new
> > >> >> > > > > >> class
> > >> >> > > > > >> >>> that will wrap non-fatal exceptions? What would be the
> > >> >> > pros/cons
> > >> >> > > > for
> > >> >> > > > > >> >>> both designs?
> > >> >> > > > > >> >>>
> > >> >> > > > > >> >>>
> > >> >> > > > > >> >>> -Matthias
> > >> >> > > > > >> >>>
> > >> >> > > > > >> >>>
> > >> >> > > > > >> >>> On 12/2/20 11:35 AM, Boyang Chen wrote:
> > >> >> > > > > >> >>>> Hey there,
> > >> >> > > > > >> >>>>
> > >> >> > > > > >> >>>> I would like to start a discussion thread for
> > KIP-691:
> > >> >> > > > > >> >>>>
> > >> >> > > > > >> >>>
> > >> >> > > > > >> >>
> > >> >> > > > > >>
> > >> >> > > > >
> > >> >> > > >
> > >> >> > >
> > >> >> >
> > >> >>
> > >>
> > https://cwiki.apache.org/confluence/display/KAFKA/KIP-691%3A+Enhance+Transactional+Producer+Exception+Handling
> > >> >> > > > > >> >>>>
> > >> >> > > > > >> >>>> The KIP is aiming to simplify the exception handling
> > >> logic
> > >> >> > for
> > >> >> > > > > >> >>>> transactional Producer users by classifying fatal and
> > >> >> > non-fatal
> > >> >> > > > > >> >>> exceptions
> > >> >> > > > > >> >>>> and throw them correspondingly for easier catch and
> > >> retry.
> > >> >> > Let
> > >> >> > > me
> > >> >> > > > > >> know
> > >> >> > > > > >> >>> what
> > >> >> > > > > >> >>>> you think.
> > >> >> > > > > >> >>>>
> > >> >> > > > > >> >>>> Best,
> > >> >> > > > > >> >>>> Boyang
> > >> >> > > > > >> >>>>
> > >> >> > > > > >> >>>
> > >> >> > > > > >> >>
> > >> >> > > > > >> >
> > >> >> > > > > >> >
> > >> >> > > > > >>
> > >> >> > > > > >
> > >> >> > > > >
> > >> >> > > >
> > >> >> > > >
> > >> >> > > > --
> > >> >> > > > -- Guozhang
> > >> >> > > >
> > >> >> > >
> > >> >> >
> > >> >> >
> > >> >> > --
> > >> >> > -- Guozhang
> > >> >> >
> > >> >>
> > >> >
> > >> >
> > >> > --
> > >> > -- Guozhang
> > >> >
> > >>
> > >>
> > >> --
> > >> -- Guozhang
> > >>
> > >
> >
>
>
> --
> -- Guozhang
