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
