Hi, Justine, Which PRC/record protocols will TV guard? Going forward, will those PRC/record protocols only be guarded by TV and not by other features like MV?
Thanks, Jun On Mon, Feb 5, 2024 at 2:41 PM Justine Olshan <jols...@confluent.io.invalid> wrote: > Hi Jun, > > Sorry I think I misunderstood your question or answered incorrectly. The TV > version should ideally be fully independent from MV. > At least for the changes I proposed, TV should not affect MV and MV should > not affect TV/ > > I think if we downgrade TV, only that feature should downgrade. Likewise > the same with MV. The finalizedFeatures should just reflect the feature > downgrade we made. > > I also plan to write a new KIP for managing the disk format and upgrade > tool as we will need new flags to support these features. That should help > clarify some things. > > Justine > > On Mon, Feb 5, 2024 at 11:03 AM Jun Rao <j...@confluent.io.invalid> wrote: > > > Hi, Justine, > > > > Thanks for the reply. > > > > So, if we downgrade TV, we could implicitly downgrade another feature > (say > > MV) that has dependency (e.g. RPC). What would we return for > > FinalizedFeatures for MV in ApiVersionsResponse in that case? > > > > Thanks, > > > > Jun > > > > On Fri, Feb 2, 2024 at 1:06 PM Justine Olshan > <jols...@confluent.io.invalid > > > > > wrote: > > > > > Hey Jun, > > > > > > Yes, the idea is that if we downgrade TV (transaction version) we will > > stop > > > using the add partitions to txn optimization and stop writing the > > flexible > > > feature version of the log. > > > In the compatibility section I included some explanations on how this > is > > > done. > > > > > > Thanks, > > > Justine > > > > > > On Fri, Feb 2, 2024 at 11:12 AM Jun Rao <j...@confluent.io.invalid> > > wrote: > > > > > > > Hi, Justine, > > > > > > > > Thanks for the update. > > > > > > > > If we ever downgrade the transaction feature, any feature depending > on > > > > changes on top of those RPC/record > > > > (AddPartitionsToTxnRequest/TransactionLogValue) changes made in > KIP-890 > > > > will be automatically downgraded too? > > > > > > > > Jun > > > > > > > > On Tue, Jan 30, 2024 at 3:32 PM Justine Olshan > > > > <jols...@confluent.io.invalid> > > > > wrote: > > > > > > > > > Hey Jun, > > > > > > > > > > I wanted to get back to you about your questions about MV/IBP. > > > > > > > > > > Looking at the options, I think it makes the most sense to create a > > > > > separate feature for transactions and use that to version gate the > > > > features > > > > > we need to version gate (flexible transactional state records and > > using > > > > the > > > > > new protocol) > > > > > I've updated the KIP to include this change. Hopefully that's > > > everything > > > > we > > > > > need for this KIP :) > > > > > > > > > > Justine > > > > > > > > > > > > > > > On Mon, Jan 22, 2024 at 3:17 PM Justine Olshan < > jols...@confluent.io > > > > > > > > wrote: > > > > > > > > > > > Thanks Jun, > > > > > > > > > > > > I will update the KIP with the prev field for prepare as well. > > > > > > > > > > > > PREPARE > > > > > > producerId: x > > > > > > previous/lastProducerId (tagged field): x > > > > > > nextProducerId (tagged field): empty or z if y will overflow > > > > > > producerEpoch: y + 1 > > > > > > > > > > > > COMPLETE > > > > > > producerId: x or z if y overflowed > > > > > > previous/lastProducerId (tagged field): x > > > > > > nextProducerId (tagged field): empty > > > > > > producerEpoch: y + 1 or 0 if we overflowed > > > > > > > > > > > > Thanks again, > > > > > > Justine > > > > > > > > > > > > On Mon, Jan 22, 2024 at 3:15 PM Jun Rao <j...@confluent.io.invalid > > > > > > > wrote: > > > > > > > > > > > >> Hi, Justine, > > > > > >> > > > > > >> 101.3 Thanks for the explanation. > > > > > >> (1) My point was that the coordinator could fail right after > > writing > > > > the > > > > > >> prepare marker. When the new txn coordinator generates the > > complete > > > > > marker > > > > > >> after the failover, it needs some field from the prepare marker > to > > > > > >> determine whether it's written by the new client. > > > > > >> > > > > > >> (2) The changing of the behavior sounds good to me. We only want > > to > > > > > return > > > > > >> success if the prepare state is written by the new client. So, > in > > > the > > > > > >> non-overflow case, it seems that we also need sth in the prepare > > > > marker > > > > > to > > > > > >> tell us whether it's written by the new client. > > > > > >> > > > > > >> 112. Thanks for the explanation. That sounds good to me. > > > > > >> > > > > > >> Jun > > > > > >> > > > > > >> On Mon, Jan 22, 2024 at 11:32 AM Justine Olshan > > > > > >> <jols...@confluent.io.invalid> wrote: > > > > > >> > > > > > >> > 101.3 I realized that I actually have two questions. > > > > > >> > > (1) In the non-overflow case, we need to write the previous > > > > produce > > > > > Id > > > > > >> > tagged field in the end maker so that we know if the marker is > > > from > > > > > the > > > > > >> new > > > > > >> > client. Since the end maker is derived from the prepare > marker, > > > > should > > > > > >> we > > > > > >> > write the previous produce Id in the prepare marker field too? > > > > > >> Otherwise, > > > > > >> > we will lose this information when deriving the end marker. > > > > > >> > > > > > > >> > The "previous" producer ID is in the normal producer ID field. > > So > > > > yes, > > > > > >> we > > > > > >> > need it in prepare and that was always the plan. > > > > > >> > > > > > > >> > Maybe it is a bit unclear so I will enumerate the fields and > add > > > > them > > > > > to > > > > > >> > the KIP if that helps. > > > > > >> > Say we have producer ID x and epoch y. When we overflow epoch > y > > we > > > > get > > > > > >> > producer ID Z. > > > > > >> > > > > > > >> > PREPARE > > > > > >> > producerId: x > > > > > >> > previous/lastProducerId (tagged field): empty > > > > > >> > nextProducerId (tagged field): empty or z if y will overflow > > > > > >> > producerEpoch: y + 1 > > > > > >> > > > > > > >> > COMPLETE > > > > > >> > producerId: x or z if y overflowed > > > > > >> > previous/lastProducerId (tagged field): x > > > > > >> > nextProducerId (tagged field): empty > > > > > >> > producerEpoch: y + 1 or 0 if we overflowed > > > > > >> > > > > > > >> > (2) In the prepare phase, if we retry and see epoch - 1 + ID > in > > > last > > > > > >> seen > > > > > >> > fields and are issuing the same command (ie commit not abort), > > we > > > > > return > > > > > >> > success. The logic before KIP-890 seems to return > > > > > >> CONCURRENT_TRANSACTIONS > > > > > >> > in this case. Are we intentionally making this change? > > > > > >> > > > > > > >> > Hmm -- we would fence the producer if the epoch is bumped and > we > > > > get a > > > > > >> > lower epoch. Yes -- we are intentionally adding this to > prevent > > > > > fencing. > > > > > >> > > > > > > >> > > > > > > >> > 112. We already merged the code that adds the VerifyOnly field > > in > > > > > >> > AddPartitionsToTxnRequest, which is an inter broker request. > It > > > > seems > > > > > >> that > > > > > >> > we didn't bump up the IBP for that. Do you know why? > > > > > >> > > > > > > >> > We no longer need IBP for all interbroker requests as > > ApiVersions > > > > > should > > > > > >> > correctly gate versioning. > > > > > >> > We also handle unsupported version errors correctly if we > > receive > > > > them > > > > > >> in > > > > > >> > edge cases like upgrades/downgrades. > > > > > >> > > > > > > >> > Justine > > > > > >> > > > > > > >> > On Mon, Jan 22, 2024 at 11:00 AM Jun Rao > > <j...@confluent.io.invalid > > > > > > > > > >> wrote: > > > > > >> > > > > > > >> > > Hi, Justine, > > > > > >> > > > > > > > >> > > Thanks for the reply. > > > > > >> > > > > > > > >> > > 101.3 I realized that I actually have two questions. > > > > > >> > > (1) In the non-overflow case, we need to write the previous > > > > produce > > > > > Id > > > > > >> > > tagged field in the end maker so that we know if the marker > is > > > > from > > > > > >> the > > > > > >> > new > > > > > >> > > client. Since the end maker is derived from the prepare > > marker, > > > > > >> should we > > > > > >> > > write the previous produce Id in the prepare marker field > too? > > > > > >> Otherwise, > > > > > >> > > we will lose this information when deriving the end marker. > > > > > >> > > (2) In the prepare phase, if we retry and see epoch - 1 + ID > > in > > > > last > > > > > >> seen > > > > > >> > > fields and are issuing the same command (ie commit not > abort), > > > we > > > > > >> return > > > > > >> > > success. The logic before KIP-890 seems to return > > > > > >> CONCURRENT_TRANSACTIONS > > > > > >> > > in this case. Are we intentionally making this change? > > > > > >> > > > > > > > >> > > 112. We already merged the code that adds the VerifyOnly > field > > > in > > > > > >> > > AddPartitionsToTxnRequest, which is an inter broker request. > > It > > > > > seems > > > > > >> > that > > > > > >> > > we didn't bump up the IBP for that. Do you know why? > > > > > >> > > > > > > > >> > > Jun > > > > > >> > > > > > > > >> > > On Fri, Jan 19, 2024 at 4:50 PM Justine Olshan > > > > > >> > > <jols...@confluent.io.invalid> > > > > > >> > > wrote: > > > > > >> > > > > > > > >> > > > Hi Jun, > > > > > >> > > > > > > > > >> > > > 101.3 I can change "last seen" to "current producer id and > > > > epoch" > > > > > if > > > > > >> > that > > > > > >> > > > was the part that was confusing > > > > > >> > > > 110 I can mention this > > > > > >> > > > 111 I can do that > > > > > >> > > > 112 We still need it. But I am still finalizing the > design. > > I > > > > will > > > > > >> > update > > > > > >> > > > the KIP once I get the information finalized. Sorry for > the > > > > > delays. > > > > > >> > > > > > > > > >> > > > Justine > > > > > >> > > > > > > > > >> > > > On Fri, Jan 19, 2024 at 10:50 AM Jun Rao > > > > <j...@confluent.io.invalid > > > > > > > > > > > >> > > wrote: > > > > > >> > > > > > > > > >> > > > > Hi, Justine, > > > > > >> > > > > > > > > > >> > > > > Thanks for the reply. > > > > > >> > > > > > > > > > >> > > > > 101.3 In the non-overflow case, the previous ID is the > > same > > > as > > > > > the > > > > > >> > > > produce > > > > > >> > > > > ID for the complete marker too, but we set the previous > ID > > > in > > > > > the > > > > > >> > > > complete > > > > > >> > > > > marker. Earlier you mentioned that this is to know that > > the > > > > > >> marker is > > > > > >> > > > > written by the new client so that we could return > success > > on > > > > > >> retried > > > > > >> > > > > endMarker requests. I was trying to understand why this > is > > > not > > > > > >> needed > > > > > >> > > for > > > > > >> > > > > the prepare marker since retry can happen in the prepare > > > state > > > > > >> too. > > > > > >> > Is > > > > > >> > > > the > > > > > >> > > > > reason that in the prepare state, we return > > > > > >> CONCURRENT_TRANSACTIONS > > > > > >> > > > instead > > > > > >> > > > > of success on retried endMaker requests? If so, should > we > > > > change > > > > > >> "If > > > > > >> > we > > > > > >> > > > > retry and see epoch - 1 + ID in last seen fields and are > > > > issuing > > > > > >> the > > > > > >> > > same > > > > > >> > > > > command (ie commit not abort) we can return (with the > new > > > > > epoch)" > > > > > >> > > > > accordingly? > > > > > >> > > > > > > > > > >> > > > > 110. Yes, without this KIP, a delayed endMaker request > > > carries > > > > > the > > > > > >> > same > > > > > >> > > > > epoch and won't be fenced. This can commit/abort a > future > > > > > >> transaction > > > > > >> > > > > unexpectedly. I am not sure if we have seen this in > > practice > > > > > >> though. > > > > > >> > > > > > > > > > >> > > > > 111. Sounds good. It would be useful to make it clear > that > > > we > > > > > can > > > > > >> now > > > > > >> > > > > populate the lastSeen field from the log reliably. > > > > > >> > > > > > > > > > >> > > > > 112. Yes, I was referring to AddPartitionsToTxnRequest > > since > > > > > it's > > > > > >> > > called > > > > > >> > > > > across brokers and we are changing its schema. Are you > > > saying > > > > we > > > > > >> > don't > > > > > >> > > > need > > > > > >> > > > > it any more? I thought that we already implemented the > > > server > > > > > side > > > > > >> > > > > verification logic based on AddPartitionsToTxnRequest > > across > > > > > >> brokers. > > > > > >> > > > > > > > > > >> > > > > Jun > > > > > >> > > > > > > > > > >> > > > > > > > > > >> > > > > On Thu, Jan 18, 2024 at 5:05 PM Justine Olshan > > > > > >> > > > > <jols...@confluent.io.invalid> > > > > > >> > > > > wrote: > > > > > >> > > > > > > > > > >> > > > > > Hey Jun, > > > > > >> > > > > > > > > > > >> > > > > > 101.3 We don't set the previous ID in the Prepare > field > > > > since > > > > > we > > > > > >> > > don't > > > > > >> > > > > need > > > > > >> > > > > > it. It is the same producer ID as the main producer ID > > > > field. > > > > > >> > > > > > > > > > > >> > > > > > 110 Hmm -- maybe I need to reread your message about > > > delayed > > > > > >> > markers. > > > > > >> > > > If > > > > > >> > > > > we > > > > > >> > > > > > receive a delayed endTxn marker after the transaction > is > > > > > already > > > > > >> > > > > complete? > > > > > >> > > > > > So we will commit the next transaction early without > the > > > > fixes > > > > > >> in > > > > > >> > > part > > > > > >> > > > 2? > > > > > >> > > > > > > > > > > >> > > > > > 111 Yes -- this terminology was used in a previous KIP > > and > > > > > never > > > > > >> > > > > > implemented it in the log -- only in memory > > > > > >> > > > > > > > > > > >> > > > > > 112 Hmm -- which interbroker protocol are you > referring > > > to? > > > > I > > > > > am > > > > > >> > > > working > > > > > >> > > > > on > > > > > >> > > > > > the design for the work to remove the extra add > > partitions > > > > > call > > > > > >> > and I > > > > > >> > > > > right > > > > > >> > > > > > now the design bumps MV. I have yet to update that > > section > > > > as > > > > > I > > > > > >> > > > finalize > > > > > >> > > > > > the design so please stay tuned. Was there anything > else > > > you > > > > > >> > thought > > > > > >> > > > > needed > > > > > >> > > > > > MV bump? > > > > > >> > > > > > > > > > > >> > > > > > Justine > > > > > >> > > > > > > > > > > >> > > > > > On Thu, Jan 18, 2024 at 3:07 PM Jun Rao > > > > > >> <j...@confluent.io.invalid> > > > > > >> > > > > wrote: > > > > > >> > > > > > > > > > > >> > > > > > > Hi, Justine, > > > > > >> > > > > > > > > > > > >> > > > > > > I don't see this create any issue. It just makes it > a > > > bit > > > > > >> hard to > > > > > >> > > > > explain > > > > > >> > > > > > > what this non-tagged produce id field means. We are > > > > > >> essentially > > > > > >> > > > trying > > > > > >> > > > > to > > > > > >> > > > > > > combine two actions (completing a txn and init a new > > > > produce > > > > > >> Id) > > > > > >> > > in a > > > > > >> > > > > > > single record. But, this may be fine too. > > > > > >> > > > > > > > > > > > >> > > > > > > A few other follow up comments. > > > > > >> > > > > > > > > > > > >> > > > > > > 101.3 I guess the reason that we only set the > previous > > > > > >> produce id > > > > > >> > > > > tagged > > > > > >> > > > > > > field in the complete marker, but not in the prepare > > > > marker, > > > > > >> is > > > > > >> > > that > > > > > >> > > > in > > > > > >> > > > > > the > > > > > >> > > > > > > prepare state, we always return > > CONCURRENT_TRANSACTIONS > > > on > > > > > >> > retried > > > > > >> > > > > > endMaker > > > > > >> > > > > > > requests? > > > > > >> > > > > > > > > > > > >> > > > > > > 110. "I believe your second point is mentioned in > the > > > > KIP. I > > > > > >> can > > > > > >> > > add > > > > > >> > > > > more > > > > > >> > > > > > > text on > > > > > >> > > > > > > this if it is helpful. > > > > > >> > > > > > > > The delayed message case can also violate EOS if > the > > > > > delayed > > > > > >> > > > message > > > > > >> > > > > > > comes in after the next addPartitionsToTxn request > > comes > > > > in. > > > > > >> > > > > Effectively > > > > > >> > > > > > we > > > > > >> > > > > > > may see a message from a previous (aborted) > > transaction > > > > > become > > > > > >> > part > > > > > >> > > > of > > > > > >> > > > > > the > > > > > >> > > > > > > next transaction." > > > > > >> > > > > > > > > > > > >> > > > > > > The above is the case when a delayed message is > > appended > > > > to > > > > > >> the > > > > > >> > > data > > > > > >> > > > > > > partition. What I mentioned is a slightly different > > case > > > > > when > > > > > >> a > > > > > >> > > > delayed > > > > > >> > > > > > > marker is appended to the transaction log partition. > > > > > >> > > > > > > > > > > > >> > > > > > > 111. The KIP says "Once we move past the Prepare and > > > > > Complete > > > > > >> > > states, > > > > > >> > > > > we > > > > > >> > > > > > > don’t need to worry about lastSeen fields and clear > > > them, > > > > > just > > > > > >> > > handle > > > > > >> > > > > > state > > > > > >> > > > > > > transitions as normal.". Is the lastSeen field the > > same > > > as > > > > > the > > > > > >> > > > previous > > > > > >> > > > > > > Produce Id tagged field in TransactionLogValue? > > > > > >> > > > > > > > > > > > >> > > > > > > 112. Since the kip changes the inter-broker > protocol, > > > > should > > > > > >> we > > > > > >> > > bump > > > > > >> > > > up > > > > > >> > > > > > the > > > > > >> > > > > > > MV/IBP version? Is this feature only for the KRaft > > mode? > > > > > >> > > > > > > > > > > > >> > > > > > > Thanks, > > > > > >> > > > > > > > > > > > >> > > > > > > Jun > > > > > >> > > > > > > > > > > > >> > > > > > > > > > > > >> > > > > > > On Wed, Jan 17, 2024 at 11:13 AM Justine Olshan > > > > > >> > > > > > > <jols...@confluent.io.invalid> wrote: > > > > > >> > > > > > > > > > > > >> > > > > > > > Hey Jun, > > > > > >> > > > > > > > > > > > > >> > > > > > > > I'm glad we are getting to convergence on the > > design. > > > :) > > > > > >> > > > > > > > > > > > > >> > > > > > > > While I understand it seems a little "weird". I'm > > not > > > > sure > > > > > >> what > > > > > >> > > the > > > > > >> > > > > > > benefit > > > > > >> > > > > > > > of writing an extra record to the log. > > > > > >> > > > > > > > Is the concern a tool to describe transactions > won't > > > > work > > > > > >> (ie, > > > > > >> > > the > > > > > >> > > > > > > complete > > > > > >> > > > > > > > state is needed to calculate the time since the > > > > > transaction > > > > > >> > > > > completed?) > > > > > >> > > > > > > > If we have a reason like this, it is enough to > > > convince > > > > me > > > > > >> we > > > > > >> > > need > > > > > >> > > > > such > > > > > >> > > > > > > an > > > > > >> > > > > > > > extra record. It seems like it would be replacing > > the > > > > > record > > > > > >> > > > written > > > > > >> > > > > on > > > > > >> > > > > > > > InitProducerId. Is this correct? > > > > > >> > > > > > > > > > > > > >> > > > > > > > Thanks, > > > > > >> > > > > > > > Justine > > > > > >> > > > > > > > > > > > > >> > > > > > > > On Tue, Jan 16, 2024 at 5:14 PM Jun Rao > > > > > >> > <j...@confluent.io.invalid > > > > > >> > > > > > > > > >> > > > > > > wrote: > > > > > >> > > > > > > > > > > > > >> > > > > > > > > Hi, Justine, > > > > > >> > > > > > > > > > > > > > >> > > > > > > > > Thanks for the explanation. I understand the > > > intention > > > > > >> now. > > > > > >> > In > > > > > >> > > > the > > > > > >> > > > > > > > overflow > > > > > >> > > > > > > > > case, we set the non-tagged field to the old pid > > > (and > > > > > the > > > > > >> max > > > > > >> > > > > epoch) > > > > > >> > > > > > in > > > > > >> > > > > > > > the > > > > > >> > > > > > > > > prepare marker so that we could correctly write > > the > > > > > >> marker to > > > > > >> > > the > > > > > >> > > > > > data > > > > > >> > > > > > > > > partition if the broker downgrades. When writing > > the > > > > > >> complete > > > > > >> > > > > marker, > > > > > >> > > > > > > we > > > > > >> > > > > > > > > know the marker has already been written to the > > data > > > > > >> > partition. > > > > > >> > > > We > > > > > >> > > > > > set > > > > > >> > > > > > > > the > > > > > >> > > > > > > > > non-tagged field to the new pid to avoid > > > > > >> > > > InvalidPidMappingException > > > > > >> > > > > > in > > > > > >> > > > > > > > the > > > > > >> > > > > > > > > client if the broker downgrades. > > > > > >> > > > > > > > > > > > > > >> > > > > > > > > The above seems to work. It's just a bit > > > inconsistent > > > > > for > > > > > >> a > > > > > >> > > > prepare > > > > > >> > > > > > > > marker > > > > > >> > > > > > > > > and a complete marker to use different pids in > > this > > > > > >> special > > > > > >> > > case. > > > > > >> > > > > If > > > > > >> > > > > > we > > > > > >> > > > > > > > > downgrade with the complete marker, it seems > that > > we > > > > > will > > > > > >> > never > > > > > >> > > > be > > > > > >> > > > > > able > > > > > >> > > > > > > > to > > > > > >> > > > > > > > > write the complete marker with the old pid. Not > > sure > > > > if > > > > > it > > > > > >> > > causes > > > > > >> > > > > any > > > > > >> > > > > > > > > issue, but it seems a bit weird. Instead of > > writing > > > > the > > > > > >> > > complete > > > > > >> > > > > > marker > > > > > >> > > > > > > > > with the new pid, could we write two records: a > > > > complete > > > > > >> > marker > > > > > >> > > > > with > > > > > >> > > > > > > the > > > > > >> > > > > > > > > old pid followed by a TransactionLogValue with > the > > > new > > > > > pid > > > > > >> > and > > > > > >> > > an > > > > > >> > > > > > empty > > > > > >> > > > > > > > > state? We could make the two records in the same > > > batch > > > > > so > > > > > >> > that > > > > > >> > > > they > > > > > >> > > > > > > will > > > > > >> > > > > > > > be > > > > > >> > > > > > > > > added to the log atomically. > > > > > >> > > > > > > > > > > > > > >> > > > > > > > > Thanks, > > > > > >> > > > > > > > > > > > > > >> > > > > > > > > Jun > > > > > >> > > > > > > > > > > > > > >> > > > > > > > > > > > > > >> > > > > > > > > On Fri, Jan 12, 2024 at 5:40 PM Justine Olshan > > > > > >> > > > > > > > > <jols...@confluent.io.invalid> > > > > > >> > > > > > > > > wrote: > > > > > >> > > > > > > > > > > > > > >> > > > > > > > > > (1) the prepare marker is written, but the > > endTxn > > > > > >> response > > > > > >> > is > > > > > >> > > > not > > > > > >> > > > > > > > > received > > > > > >> > > > > > > > > > by the client when the server downgrades > > > > > >> > > > > > > > > > (2) the prepare marker is written, the endTxn > > > > > response > > > > > >> is > > > > > >> > > > > received > > > > > >> > > > > > > by > > > > > >> > > > > > > > > the > > > > > >> > > > > > > > > > client when the server downgrades. > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > I think I am still a little confused. In both > of > > > > these > > > > > >> > cases, > > > > > >> > > > the > > > > > >> > > > > > > > > > transaction log has the old producer ID. We > > don't > > > > > write > > > > > >> the > > > > > >> > > new > > > > > >> > > > > > > > producer > > > > > >> > > > > > > > > ID > > > > > >> > > > > > > > > > in the prepare marker's non tagged fields. > > > > > >> > > > > > > > > > If the server downgrades now, it would read > the > > > > > records > > > > > >> not > > > > > >> > > in > > > > > >> > > > > > tagged > > > > > >> > > > > > > > > > fields and the complete marker will also have > > the > > > > old > > > > > >> > > producer > > > > > >> > > > > ID. > > > > > >> > > > > > > > > > (If we had used the new producer ID, we would > > not > > > > have > > > > > >> > > > > > transactional > > > > > >> > > > > > > > > > correctness since the producer id doesn't > match > > > the > > > > > >> > > transaction > > > > > >> > > > > and > > > > > >> > > > > > > the > > > > > >> > > > > > > > > > state would not be correct on the data > > partition.) > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > In the overflow case, I'd expect the following > > to > > > > > >> happen on > > > > > >> > > the > > > > > >> > > > > > > client > > > > > >> > > > > > > > > side > > > > > >> > > > > > > > > > Case 1 -- we retry EndTxn -- it is the same > > > > producer > > > > > ID > > > > > >> > and > > > > > >> > > > > epoch > > > > > >> > > > > > - > > > > > >> > > > > > > 1 > > > > > >> > > > > > > > > this > > > > > >> > > > > > > > > > would fence the producer > > > > > >> > > > > > > > > > Case 2 -- we don't retry EndTxn and use the > new > > > > > >> producer id > > > > > >> > > > which > > > > > >> > > > > > > would > > > > > >> > > > > > > > > > result in InvalidPidMappingException > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > Maybe we can have special handling for when a > > > server > > > > > >> > > > downgrades. > > > > > >> > > > > > When > > > > > >> > > > > > > > it > > > > > >> > > > > > > > > > reconnects we could get an API version request > > > > showing > > > > > >> > > KIP-890 > > > > > >> > > > > > part 2 > > > > > >> > > > > > > > is > > > > > >> > > > > > > > > > not supported. In that case, we can call > > > > > initProducerId > > > > > >> to > > > > > >> > > > abort > > > > > >> > > > > > the > > > > > >> > > > > > > > > > transaction. (In the overflow case, this > > correctly > > > > > gives > > > > > >> > us a > > > > > >> > > > new > > > > > >> > > > > > > > > producer > > > > > >> > > > > > > > > > ID) > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > I guess the corresponding case would be where > > the > > > > > >> *complete > > > > > >> > > > > marker > > > > > >> > > > > > > *is > > > > > >> > > > > > > > > > written but the endTxn is not received by the > > > client > > > > > and > > > > > >> > the > > > > > >> > > > > server > > > > > >> > > > > > > > > > downgrades? This would result in the > transaction > > > > > >> > coordinator > > > > > >> > > > > having > > > > > >> > > > > > > the > > > > > >> > > > > > > > > new > > > > > >> > > > > > > > > > ID and not the old one. If the client > retries, > > it > > > > > will > > > > > >> > > receive > > > > > >> > > > > an > > > > > >> > > > > > > > > > InvalidPidMappingException. The InitProducerId > > > > > scenario > > > > > >> > above > > > > > >> > > > > would > > > > > >> > > > > > > > help > > > > > >> > > > > > > > > > here too. > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > To be clear, my compatibility story is meant > to > > > > > support > > > > > >> > > > > downgrades > > > > > >> > > > > > > > server > > > > > >> > > > > > > > > > side in keeping the transactional correctness. > > > > Keeping > > > > > >> the > > > > > >> > > > client > > > > > >> > > > > > > from > > > > > >> > > > > > > > > > fencing itself is not the priority. > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > Hope this helps. I can also add text in the > KIP > > > > about > > > > > >> > > > > > InitProducerId > > > > > >> > > > > > > if > > > > > >> > > > > > > > > we > > > > > >> > > > > > > > > > think that fixes some edge cases. > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > Justine > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > On Fri, Jan 12, 2024 at 4:10 PM Jun Rao > > > > > >> > > > <j...@confluent.io.invalid > > > > > >> > > > > > > > > > > >> > > > > > > > > wrote: > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > Hi, Justine, > > > > > >> > > > > > > > > > > > > > > > >> > > > > > > > > > > Thanks for the reply. > > > > > >> > > > > > > > > > > > > > > > >> > > > > > > > > > > I agree that we don't need to optimize for > > > fencing > > > > > >> during > > > > > >> > > > > > > downgrades. > > > > > >> > > > > > > > > > > Regarding consistency, there are two > possible > > > > cases: > > > > > >> (1) > > > > > >> > > the > > > > > >> > > > > > > prepare > > > > > >> > > > > > > > > > marker > > > > > >> > > > > > > > > > > is written, but the endTxn response is not > > > > received > > > > > by > > > > > >> > the > > > > > >> > > > > client > > > > > >> > > > > > > > when > > > > > >> > > > > > > > > > the > > > > > >> > > > > > > > > > > server downgrades; (2) the prepare marker > is > > > > > written, > > > > > >> > the > > > > > >> > > > > endTxn > > > > > >> > > > > > > > > > response > > > > > >> > > > > > > > > > > is received by the client when the server > > > > > downgrades. > > > > > >> In > > > > > >> > > (1), > > > > > >> > > > > the > > > > > >> > > > > > > > > client > > > > > >> > > > > > > > > > > will have the old produce Id and in (2), the > > > > client > > > > > >> will > > > > > >> > > have > > > > > >> > > > > the > > > > > >> > > > > > > new > > > > > >> > > > > > > > > > > produce Id. If we downgrade right after the > > > > prepare > > > > > >> > marker, > > > > > >> > > > we > > > > > >> > > > > > > can't > > > > > >> > > > > > > > be > > > > > >> > > > > > > > > > > consistent to both (1) and (2) since we can > > only > > > > put > > > > > >> one > > > > > >> > > > value > > > > > >> > > > > in > > > > > >> > > > > > > the > > > > > >> > > > > > > > > > > existing produce Id field. It's also not > clear > > > > which > > > > > >> case > > > > > >> > > is > > > > > >> > > > > more > > > > > >> > > > > > > > > likely. > > > > > >> > > > > > > > > > > So we could probably be consistent with > either > > > > case. > > > > > >> By > > > > > >> > > > putting > > > > > >> > > > > > the > > > > > >> > > > > > > > new > > > > > >> > > > > > > > > > > producer Id in the prepare marker, we are > > > > consistent > > > > > >> with > > > > > >> > > > case > > > > > >> > > > > > (2) > > > > > >> > > > > > > > and > > > > > >> > > > > > > > > it > > > > > >> > > > > > > > > > > also has the slight benefit that the produce > > > field > > > > > in > > > > > >> the > > > > > >> > > > > prepare > > > > > >> > > > > > > and > > > > > >> > > > > > > > > > > complete marker are consistent in the > overflow > > > > case. > > > > > >> > > > > > > > > > > > > > > > >> > > > > > > > > > > Jun > > > > > >> > > > > > > > > > > > > > > > >> > > > > > > > > > > On Fri, Jan 12, 2024 at 3:11 PM Justine > Olshan > > > > > >> > > > > > > > > > > <jols...@confluent.io.invalid> > > > > > >> > > > > > > > > > > wrote: > > > > > >> > > > > > > > > > > > > > > > >> > > > > > > > > > > > Hi Jun, > > > > > >> > > > > > > > > > > > > > > > > >> > > > > > > > > > > > In the case you describe, we would need to > > > have > > > > a > > > > > >> > delayed > > > > > >> > > > > > > request, > > > > > >> > > > > > > > > > send a > > > > > >> > > > > > > > > > > > successful EndTxn, and a successful > > > > > >> AddPartitionsToTxn > > > > > >> > > and > > > > > >> > > > > then > > > > > >> > > > > > > > have > > > > > >> > > > > > > > > > the > > > > > >> > > > > > > > > > > > delayed EndTxn request go through for a > > given > > > > > >> producer. > > > > > >> > > > > > > > > > > > I'm trying to figure out if it is possible > > for > > > > the > > > > > >> > client > > > > > >> > > > to > > > > > >> > > > > > > > > transition > > > > > >> > > > > > > > > > > if > > > > > >> > > > > > > > > > > > a previous request is delayed somewhere. > But > > > > yes, > > > > > in > > > > > >> > this > > > > > >> > > > > case > > > > > >> > > > > > I > > > > > >> > > > > > > > > think > > > > > >> > > > > > > > > > we > > > > > >> > > > > > > > > > > > would fence the client. > > > > > >> > > > > > > > > > > > > > > > > >> > > > > > > > > > > > Not for the overflow case. In the overflow > > > case, > > > > > the > > > > > >> > > > producer > > > > > >> > > > > > ID > > > > > >> > > > > > > > and > > > > > >> > > > > > > > > > the > > > > > >> > > > > > > > > > > > epoch are different on the marker and on > the > > > new > > > > > >> > > > transaction. > > > > > >> > > > > > So > > > > > >> > > > > > > we > > > > > >> > > > > > > > > > want > > > > > >> > > > > > > > > > > > the marker to use the max epoch but the > new > > > > > >> > transaction > > > > > >> > > > > should > > > > > >> > > > > > > > start > > > > > >> > > > > > > > > > > with > > > > > >> > > > > > > > > > > > the new ID and epoch 0 in the > transactional > > > > state. > > > > > >> > > > > > > > > > > > > > > > > >> > > > > > > > > > > > In the server downgrade case, we want to > see > > > the > > > > > >> > producer > > > > > >> > > > ID > > > > > >> > > > > as > > > > > >> > > > > > > > that > > > > > >> > > > > > > > > is > > > > > >> > > > > > > > > > > > what the client will have. If we complete > > the > > > > > >> commit, > > > > > >> > and > > > > > >> > > > the > > > > > >> > > > > > > > > > transaction > > > > > >> > > > > > > > > > > > state is reloaded, we need the new > producer > > ID > > > > in > > > > > >> the > > > > > >> > > state > > > > > >> > > > > so > > > > > >> > > > > > > > there > > > > > >> > > > > > > > > > > isn't > > > > > >> > > > > > > > > > > > an invalid producer ID mapping. > > > > > >> > > > > > > > > > > > The server downgrade cases are considering > > > > > >> > transactional > > > > > >> > > > > > > > correctness > > > > > >> > > > > > > > > > and > > > > > >> > > > > > > > > > > > not regressing from previous behavior -- > and > > > are > > > > > not > > > > > >> > > > > concerned > > > > > >> > > > > > > > about > > > > > >> > > > > > > > > > > > supporting the safety from fencing retries > > (as > > > > we > > > > > >> have > > > > > >> > > > > > downgraded > > > > > >> > > > > > > > so > > > > > >> > > > > > > > > we > > > > > >> > > > > > > > > > > > don't need to support). Perhaps this is a > > > trade > > > > > off, > > > > > >> > but > > > > > >> > > I > > > > > >> > > > > > think > > > > > >> > > > > > > it > > > > > >> > > > > > > > > is > > > > > >> > > > > > > > > > > the > > > > > >> > > > > > > > > > > > right one. > > > > > >> > > > > > > > > > > > > > > > > >> > > > > > > > > > > > (If the client downgrades, it will have > > > > restarted > > > > > >> and > > > > > >> > it > > > > > >> > > is > > > > > >> > > > > ok > > > > > >> > > > > > > for > > > > > >> > > > > > > > it > > > > > >> > > > > > > > > > to > > > > > >> > > > > > > > > > > > have a new producer ID too). > > > > > >> > > > > > > > > > > > > > > > > >> > > > > > > > > > > > Justine > > > > > >> > > > > > > > > > > > > > > > > >> > > > > > > > > > > > On Fri, Jan 12, 2024 at 11:42 AM Jun Rao > > > > > >> > > > > > > <j...@confluent.io.invalid > > > > > >> > > > > > > > > > > > > > >> > > > > > > > > > > wrote: > > > > > >> > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > Hi, Justine, > > > > > >> > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > Thanks for the reply. > > > > > >> > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > 101.4 "If the marker is written by the > new > > > > > >> client, we > > > > > >> > > can > > > > > >> > > > > as > > > > > >> > > > > > I > > > > > >> > > > > > > > > > > mentioned > > > > > >> > > > > > > > > > > > in > > > > > >> > > > > > > > > > > > > the last email guarantee that any EndTxn > > > > > requests > > > > > >> > with > > > > > >> > > > the > > > > > >> > > > > > same > > > > > >> > > > > > > > > epoch > > > > > >> > > > > > > > > > > are > > > > > >> > > > > > > > > > > > > from the same producer and the same > > > > transaction. > > > > > >> Then > > > > > >> > > we > > > > > >> > > > > > don't > > > > > >> > > > > > > > have > > > > > >> > > > > > > > > > to > > > > > >> > > > > > > > > > > > > return a fenced error but can handle > > > > gracefully > > > > > as > > > > > >> > > > > described > > > > > >> > > > > > in > > > > > >> > > > > > > > the > > > > > >> > > > > > > > > > > KIP." > > > > > >> > > > > > > > > > > > > When a delayed EndTnx request is > > processed, > > > > the > > > > > >> txn > > > > > >> > > state > > > > > >> > > > > > could > > > > > >> > > > > > > > be > > > > > >> > > > > > > > > > > > ongoing > > > > > >> > > > > > > > > > > > > for the next txn. I guess in this case > we > > > > still > > > > > >> > return > > > > > >> > > > the > > > > > >> > > > > > > fenced > > > > > >> > > > > > > > > > error > > > > > >> > > > > > > > > > > > for > > > > > >> > > > > > > > > > > > > the delayed request? > > > > > >> > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > 102. Sorry, my question was inaccurate. > > What > > > > you > > > > > >> > > > described > > > > > >> > > > > is > > > > > >> > > > > > > > > > accurate. > > > > > >> > > > > > > > > > > > > "The downgrade compatibility I mention > is > > > that > > > > > we > > > > > >> > keep > > > > > >> > > > the > > > > > >> > > > > > same > > > > > >> > > > > > > > > > > producer > > > > > >> > > > > > > > > > > > ID > > > > > >> > > > > > > > > > > > > and epoch in the main (non-tagged) > fields > > as > > > > we > > > > > >> did > > > > > >> > > > before > > > > > >> > > > > > the > > > > > >> > > > > > > > code > > > > > >> > > > > > > > > > on > > > > > >> > > > > > > > > > > > the > > > > > >> > > > > > > > > > > > > server side." If we want to do this, it > > > seems > > > > > >> that we > > > > > >> > > > > should > > > > > >> > > > > > > use > > > > > >> > > > > > > > > the > > > > > >> > > > > > > > > > > > > current produce Id and max epoch in the > > > > existing > > > > > >> > > > producerId > > > > > >> > > > > > and > > > > > >> > > > > > > > > > > > > producerEpoch fields for both the > prepare > > > and > > > > > the > > > > > >> > > > complete > > > > > >> > > > > > > > marker, > > > > > >> > > > > > > > > > > right? > > > > > >> > > > > > > > > > > > > The downgrade can happen after the > > complete > > > > > >> marker is > > > > > >> > > > > > written. > > > > > >> > > > > > > > With > > > > > >> > > > > > > > > > > what > > > > > >> > > > > > > > > > > > > you described, the downgraded > coordinator > > > will > > > > > see > > > > > >> > the > > > > > >> > > > new > > > > > >> > > > > > > > produce > > > > > >> > > > > > > > > Id > > > > > >> > > > > > > > > > > > > instead of the old one. > > > > > >> > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > Jun > > > > > >> > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > On Fri, Jan 12, 2024 at 10:44 AM Justine > > > > Olshan > > > > > >> > > > > > > > > > > > > <jols...@confluent.io.invalid> wrote: > > > > > >> > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > Hi Jun, > > > > > >> > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > I can update the description. > > > > > >> > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > I believe your second point is > mentioned > > > in > > > > > the > > > > > >> > KIP. > > > > > >> > > I > > > > > >> > > > > can > > > > > >> > > > > > > add > > > > > >> > > > > > > > > more > > > > > >> > > > > > > > > > > > text > > > > > >> > > > > > > > > > > > > on > > > > > >> > > > > > > > > > > > > > this if it is helpful. > > > > > >> > > > > > > > > > > > > > > The delayed message case can also > > > violate > > > > > EOS > > > > > >> if > > > > > >> > > the > > > > > >> > > > > > > delayed > > > > > >> > > > > > > > > > > message > > > > > >> > > > > > > > > > > > > > comes in after the next > > addPartitionsToTxn > > > > > >> request > > > > > >> > > > comes > > > > > >> > > > > > in. > > > > > >> > > > > > > > > > > > Effectively > > > > > >> > > > > > > > > > > > > we > > > > > >> > > > > > > > > > > > > > may see a message from a previous > > > (aborted) > > > > > >> > > transaction > > > > > >> > > > > > > become > > > > > >> > > > > > > > > part > > > > > >> > > > > > > > > > > of > > > > > >> > > > > > > > > > > > > the > > > > > >> > > > > > > > > > > > > > next transaction. > > > > > >> > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > If the marker is written by the new > > > client, > > > > we > > > > > >> can > > > > > >> > > as I > > > > > >> > > > > > > > mentioned > > > > > >> > > > > > > > > > in > > > > > >> > > > > > > > > > > > the > > > > > >> > > > > > > > > > > > > > last email guarantee that any EndTxn > > > > requests > > > > > >> with > > > > > >> > > the > > > > > >> > > > > same > > > > > >> > > > > > > > epoch > > > > > >> > > > > > > > > > are > > > > > >> > > > > > > > > > > > > from > > > > > >> > > > > > > > > > > > > > the same producer and the same > > > transaction. > > > > > >> Then we > > > > > >> > > > don't > > > > > >> > > > > > > have > > > > > >> > > > > > > > to > > > > > >> > > > > > > > > > > > return > > > > > >> > > > > > > > > > > > > a > > > > > >> > > > > > > > > > > > > > fenced error but can handle gracefully > > as > > > > > >> described > > > > > >> > > in > > > > > >> > > > > the > > > > > >> > > > > > > KIP. > > > > > >> > > > > > > > > > > > > > I don't think a boolean is useful > since > > it > > > > is > > > > > >> > > directly > > > > > >> > > > > > > encoded > > > > > >> > > > > > > > by > > > > > >> > > > > > > > > > the > > > > > >> > > > > > > > > > > > > > existence or lack of the tagged field > > > being > > > > > >> > written. > > > > > >> > > > > > > > > > > > > > In the prepare marker we will have the > > > same > > > > > >> > producer > > > > > >> > > ID > > > > > >> > > > > in > > > > > >> > > > > > > the > > > > > >> > > > > > > > > > > > non-tagged > > > > > >> > > > > > > > > > > > > > field. In the Complete state we may > not. > > > > > >> > > > > > > > > > > > > > I'm not sure why the ongoing state > > matters > > > > for > > > > > >> this > > > > > >> > > > KIP. > > > > > >> > > > > It > > > > > >> > > > > > > > does > > > > > >> > > > > > > > > > > matter > > > > > >> > > > > > > > > > > > > for > > > > > >> > > > > > > > > > > > > > KIP-939. > > > > > >> > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > I'm not sure what you are referring to > > > about > > > > > >> > writing > > > > > >> > > > the > > > > > >> > > > > > > > previous > > > > > >> > > > > > > > > > > > > producer > > > > > >> > > > > > > > > > > > > > ID in the prepare marker. This is not > in > > > the > > > > > >> KIP. > > > > > >> > > > > > > > > > > > > > In the overflow case, we write the > > > > > >> nextProducerId > > > > > >> > in > > > > > >> > > > the > > > > > >> > > > > > > > prepare > > > > > >> > > > > > > > > > > state. > > > > > >> > > > > > > > > > > > > > This is so we know what we assigned > when > > > we > > > > > >> reload > > > > > >> > > the > > > > > >> > > > > > > > > transaction > > > > > >> > > > > > > > > > > log. > > > > > >> > > > > > > > > > > > > > Once we complete, we transition this > ID > > to > > > > the > > > > > >> main > > > > > >> > > > > > > (non-tagged > > > > > >> > > > > > > > > > > field) > > > > > >> > > > > > > > > > > > > and > > > > > >> > > > > > > > > > > > > > have the previous producer ID field > > filled > > > > in. > > > > > >> This > > > > > >> > > is > > > > > >> > > > so > > > > > >> > > > > > we > > > > > >> > > > > > > > can > > > > > >> > > > > > > > > > > > identify > > > > > >> > > > > > > > > > > > > > in a retry case the operation > completed > > > > > >> > successfully > > > > > >> > > > and > > > > > >> > > > > we > > > > > >> > > > > > > > don't > > > > > >> > > > > > > > > > > fence > > > > > >> > > > > > > > > > > > > our > > > > > >> > > > > > > > > > > > > > producer. The downgrade compatibility > I > > > > > mention > > > > > >> is > > > > > >> > > that > > > > > >> > > > > we > > > > > >> > > > > > > keep > > > > > >> > > > > > > > > the > > > > > >> > > > > > > > > > > > same > > > > > >> > > > > > > > > > > > > > producer ID and epoch in the main > > > > (non-tagged) > > > > > >> > fields > > > > > >> > > > as > > > > > >> > > > > we > > > > > >> > > > > > > did > > > > > >> > > > > > > > > > > before > > > > > >> > > > > > > > > > > > > the > > > > > >> > > > > > > > > > > > > > code on the server side. If the server > > > > > >> downgrades, > > > > > >> > we > > > > > >> > > > are > > > > > >> > > > > > > still > > > > > >> > > > > > > > > > > > > compatible. > > > > > >> > > > > > > > > > > > > > This addresses both the prepare and > > > complete > > > > > >> state > > > > > >> > > > > > > downgrades. > > > > > >> > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > Justine > > > > > >> > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > On Fri, Jan 12, 2024 at 10:21 AM Jun > Rao > > > > > >> > > > > > > > > <j...@confluent.io.invalid > > > > > >> > > > > > > > > > > > > > > > >> > > > > > > > > > > > > wrote: > > > > > >> > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > Hi, Justine, > > > > > >> > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > Thanks for the reply. Sorry for the > > > > delay. I > > > > > >> > have a > > > > > >> > > > few > > > > > >> > > > > > > more > > > > > >> > > > > > > > > > > > comments. > > > > > >> > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > 110. I think the motivation section > > > could > > > > be > > > > > >> > > > improved. > > > > > >> > > > > > One > > > > > >> > > > > > > of > > > > > >> > > > > > > > > the > > > > > >> > > > > > > > > > > > > > > motivations listed by the KIP is > "This > > > can > > > > > >> happen > > > > > >> > > > when > > > > > >> > > > > a > > > > > >> > > > > > > > > message > > > > > >> > > > > > > > > > > gets > > > > > >> > > > > > > > > > > > > > stuck > > > > > >> > > > > > > > > > > > > > > or delayed due to networking issues > > or a > > > > > >> network > > > > > >> > > > > > partition, > > > > > >> > > > > > > > the > > > > > >> > > > > > > > > > > > > > transaction > > > > > >> > > > > > > > > > > > > > > aborts, and then the delayed message > > > > finally > > > > > >> > comes > > > > > >> > > > > in.". > > > > > >> > > > > > > This > > > > > >> > > > > > > > > > seems > > > > > >> > > > > > > > > > > > not > > > > > >> > > > > > > > > > > > > > > very accurate. Without KIP-890, > > > currently, > > > > > if > > > > > >> the > > > > > >> > > > > > > coordinator > > > > > >> > > > > > > > > > times > > > > > >> > > > > > > > > > > > out > > > > > >> > > > > > > > > > > > > > and > > > > > >> > > > > > > > > > > > > > > aborts an ongoing transaction, it > > > already > > > > > >> bumps > > > > > >> > up > > > > > >> > > > the > > > > > >> > > > > > > epoch > > > > > >> > > > > > > > in > > > > > >> > > > > > > > > > the > > > > > >> > > > > > > > > > > > > > marker, > > > > > >> > > > > > > > > > > > > > > which prevents the delayed produce > > > message > > > > > >> from > > > > > >> > > being > > > > > >> > > > > > added > > > > > >> > > > > > > > to > > > > > >> > > > > > > > > > the > > > > > >> > > > > > > > > > > > user > > > > > >> > > > > > > > > > > > > > > partition. What can cause a hanging > > > > > >> transaction > > > > > >> > is > > > > > >> > > > that > > > > > >> > > > > > the > > > > > >> > > > > > > > > > > producer > > > > > >> > > > > > > > > > > > > > > completes (either aborts or > commits) a > > > > > >> > transaction > > > > > >> > > > > before > > > > > >> > > > > > > > > > > receiving a > > > > > >> > > > > > > > > > > > > > > successful ack on messages published > > in > > > > the > > > > > >> same > > > > > >> > > txn. > > > > > >> > > > > In > > > > > >> > > > > > > this > > > > > >> > > > > > > > > > case, > > > > > >> > > > > > > > > > > > > it's > > > > > >> > > > > > > > > > > > > > > possible for the delayed message to > be > > > > > >> appended > > > > > >> > to > > > > > >> > > > the > > > > > >> > > > > > > > > partition > > > > > >> > > > > > > > > > > > after > > > > > >> > > > > > > > > > > > > > the > > > > > >> > > > > > > > > > > > > > > marker, causing a transaction to > hang. > > > > > >> > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > A similar issue (not mentioned in > the > > > > > >> motivation) > > > > > >> > > > could > > > > > >> > > > > > > > happen > > > > > >> > > > > > > > > on > > > > > >> > > > > > > > > > > the > > > > > >> > > > > > > > > > > > > > > marker in the coordinator's log. For > > > > > example, > > > > > >> > it's > > > > > >> > > > > > possible > > > > > >> > > > > > > > for > > > > > >> > > > > > > > > > an > > > > > >> > > > > > > > > > > > > > > EndTxnRequest to be delayed on the > > > > > >> coordinator. > > > > > >> > By > > > > > >> > > > the > > > > > >> > > > > > time > > > > > >> > > > > > > > the > > > > > >> > > > > > > > > > > > delayed > > > > > >> > > > > > > > > > > > > > > EndTxnRequest is processed, it's > > > possible > > > > > that > > > > > >> > the > > > > > >> > > > > > previous > > > > > >> > > > > > > > txn > > > > > >> > > > > > > > > > has > > > > > >> > > > > > > > > > > > > > already > > > > > >> > > > > > > > > > > > > > > completed and a new txn has started. > > > > > >> Currently, > > > > > >> > > since > > > > > >> > > > > the > > > > > >> > > > > > > > epoch > > > > > >> > > > > > > > > > is > > > > > >> > > > > > > > > > > > not > > > > > >> > > > > > > > > > > > > > > bumped on every txn, the delayed > > > > > EndTxnRequest > > > > > >> > will > > > > > >> > > > add > > > > > >> > > > > > an > > > > > >> > > > > > > > > > > unexpected > > > > > >> > > > > > > > > > > > > > > prepare marker (and eventually a > > > complete > > > > > >> marker) > > > > > >> > > to > > > > > >> > > > > the > > > > > >> > > > > > > > > ongoing > > > > > >> > > > > > > > > > > txn. > > > > > >> > > > > > > > > > > > > > This > > > > > >> > > > > > > > > > > > > > > won't cause the transaction to hang, > > but > > > > it > > > > > >> will > > > > > >> > > > break > > > > > >> > > > > > the > > > > > >> > > > > > > > EoS > > > > > >> > > > > > > > > > > > > semantic. > > > > > >> > > > > > > > > > > > > > > The proposal in this KIP will > address > > > this > > > > > >> issue > > > > > >> > > too. > > > > > >> > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > 101. "However, I was writing it so > > that > > > we > > > > > can > > > > > >> > > > > > distinguish > > > > > >> > > > > > > > > > between > > > > > >> > > > > > > > > > > > > > > old clients where we don't have the > > > > ability > > > > > do > > > > > >> > this > > > > > >> > > > > > > operation > > > > > >> > > > > > > > > and > > > > > >> > > > > > > > > > > new > > > > > >> > > > > > > > > > > > > > > clients that can. (Old clients don't > > > bump > > > > > the > > > > > >> > epoch > > > > > >> > > > on > > > > > >> > > > > > > > commit, > > > > > >> > > > > > > > > so > > > > > >> > > > > > > > > > > we > > > > > >> > > > > > > > > > > > > > can't > > > > > >> > > > > > > > > > > > > > > say for sure the write belongs to > the > > > > given > > > > > >> > > > > > transaction)." > > > > > >> > > > > > > > > > > > > > > 101.1 I am wondering why we need to > > > > > >> distinguish > > > > > >> > > > whether > > > > > >> > > > > > the > > > > > >> > > > > > > > > > marker > > > > > >> > > > > > > > > > > is > > > > > >> > > > > > > > > > > > > > > written by the old and the new > client. > > > > Could > > > > > >> you > > > > > >> > > > > describe > > > > > >> > > > > > > > what > > > > > >> > > > > > > > > we > > > > > >> > > > > > > > > > > do > > > > > >> > > > > > > > > > > > > > > differently if we know the marker is > > > > written > > > > > >> by > > > > > >> > the > > > > > >> > > > new > > > > > >> > > > > > > > client? > > > > > >> > > > > > > > > > > > > > > 101.2 If we do need a way to > > distinguish > > > > > >> whether > > > > > >> > > the > > > > > >> > > > > > marker > > > > > >> > > > > > > > is > > > > > >> > > > > > > > > > > > written > > > > > >> > > > > > > > > > > > > by > > > > > >> > > > > > > > > > > > > > > the old and the new client. Would it > > be > > > > > >> simpler > > > > > >> > to > > > > > >> > > > just > > > > > >> > > > > > > > > > introduce a > > > > > >> > > > > > > > > > > > > > boolean > > > > > >> > > > > > > > > > > > > > > field instead of indirectly through > > the > > > > > >> previous > > > > > >> > > > > produce > > > > > >> > > > > > ID > > > > > >> > > > > > > > > > field? > > > > > >> > > > > > > > > > > > > > > 101.3 It's not clear to me why we > only > > > add > > > > > the > > > > > >> > > > previous > > > > > >> > > > > > > > produce > > > > > >> > > > > > > > > > ID > > > > > >> > > > > > > > > > > > > field > > > > > >> > > > > > > > > > > > > > in > > > > > >> > > > > > > > > > > > > > > the complete marker, but not in the > > > > prepare > > > > > >> > marker. > > > > > >> > > > If > > > > > >> > > > > we > > > > > >> > > > > > > > want > > > > > >> > > > > > > > > to > > > > > >> > > > > > > > > > > > know > > > > > >> > > > > > > > > > > > > > > whether a marker is written by the > new > > > > > client > > > > > >> or > > > > > >> > > not, > > > > > >> > > > > it > > > > > >> > > > > > > > seems > > > > > >> > > > > > > > > > that > > > > > >> > > > > > > > > > > > we > > > > > >> > > > > > > > > > > > > > want > > > > > >> > > > > > > > > > > > > > > to do this consistently for all > > markers. > > > > > >> > > > > > > > > > > > > > > 101.4 What about the > > TransactionLogValue > > > > > >> record > > > > > >> > > > > > > representing > > > > > >> > > > > > > > > the > > > > > >> > > > > > > > > > > > > ongoing > > > > > >> > > > > > > > > > > > > > > state? Should we also distinguish > > > whether > > > > > it's > > > > > >> > > > written > > > > > >> > > > > by > > > > > >> > > > > > > the > > > > > >> > > > > > > > > old > > > > > >> > > > > > > > > > > or > > > > > >> > > > > > > > > > > > > the > > > > > >> > > > > > > > > > > > > > > new client? > > > > > >> > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > 102. In the overflow case, it's > still > > > not > > > > > >> clear > > > > > >> > to > > > > > >> > > me > > > > > >> > > > > why > > > > > >> > > > > > > we > > > > > >> > > > > > > > > > write > > > > > >> > > > > > > > > > > > the > > > > > >> > > > > > > > > > > > > > > previous produce Id in the prepare > > > marker > > > > > >> while > > > > > >> > > > writing > > > > > >> > > > > > the > > > > > >> > > > > > > > > next > > > > > >> > > > > > > > > > > > > produce > > > > > >> > > > > > > > > > > > > > Id > > > > > >> > > > > > > > > > > > > > > in the complete marker. You > mentioned > > > that > > > > > >> it's > > > > > >> > for > > > > > >> > > > > > > > > downgrading. > > > > > >> > > > > > > > > > > > > However, > > > > > >> > > > > > > > > > > > > > > we could downgrade with either the > > > prepare > > > > > >> marker > > > > > >> > > or > > > > > >> > > > > the > > > > > >> > > > > > > > > complete > > > > > >> > > > > > > > > > > > > marker. > > > > > >> > > > > > > > > > > > > > > In either case, the downgraded > > > coordinator > > > > > >> should > > > > > >> > > see > > > > > >> > > > > the > > > > > >> > > > > > > > same > > > > > >> > > > > > > > > > > > produce > > > > > >> > > > > > > > > > > > > id > > > > > >> > > > > > > > > > > > > > > (probably the previous produce Id), > > > right? > > > > > >> > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > Jun > > > > > >> > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > On Wed, Dec 20, 2023 at 6:00 PM > > Justine > > > > > Olshan > > > > > >> > > > > > > > > > > > > > > <jols...@confluent.io.invalid> > > > > > >> > > > > > > > > > > > > > > wrote: > > > > > >> > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > Hey Jun, > > > > > >> > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > Thanks for taking a look at the > KIP > > > > again. > > > > > >> > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > 100. For the epoch overflow case, > > only > > > > the > > > > > >> > marker > > > > > >> > > > > will > > > > > >> > > > > > > have > > > > > >> > > > > > > > > max > > > > > >> > > > > > > > > > > > > epoch. > > > > > >> > > > > > > > > > > > > > > This > > > > > >> > > > > > > > > > > > > > > > keeps the behavior of the rest of > > the > > > > > >> markers > > > > > >> > > where > > > > > >> > > > > the > > > > > >> > > > > > > > last > > > > > >> > > > > > > > > > > marker > > > > > >> > > > > > > > > > > > > is > > > > > >> > > > > > > > > > > > > > > the > > > > > >> > > > > > > > > > > > > > > > epoch of the transaction records + > > 1. > > > > > >> > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > 101. You are correct that we don't > > > need > > > > to > > > > > >> > write > > > > > >> > > > the > > > > > >> > > > > > > > producer > > > > > >> > > > > > > > > > ID > > > > > >> > > > > > > > > > > > > since > > > > > >> > > > > > > > > > > > > > it > > > > > >> > > > > > > > > > > > > > > > is the same. However, I was > writing > > it > > > > so > > > > > >> that > > > > > >> > we > > > > > >> > > > can > > > > > >> > > > > > > > > > distinguish > > > > > >> > > > > > > > > > > > > > between > > > > > >> > > > > > > > > > > > > > > > old clients where we don't have > the > > > > > ability > > > > > >> do > > > > > >> > > this > > > > > >> > > > > > > > operation > > > > > >> > > > > > > > > > and > > > > > >> > > > > > > > > > > > new > > > > > >> > > > > > > > > > > > > > > > clients that can. (Old clients > don't > > > > bump > > > > > >> the > > > > > >> > > epoch > > > > > >> > > > > on > > > > > >> > > > > > > > > commit, > > > > > >> > > > > > > > > > so > > > > > >> > > > > > > > > > > > we > > > > > >> > > > > > > > > > > > > > > can't > > > > > >> > > > > > > > > > > > > > > > say for sure the write belongs to > > the > > > > > given > > > > > >> > > > > > transaction). > > > > > >> > > > > > > > If > > > > > >> > > > > > > > > we > > > > > >> > > > > > > > > > > > > receive > > > > > >> > > > > > > > > > > > > > > an > > > > > >> > > > > > > > > > > > > > > > EndTxn request from a new client, > we > > > > will > > > > > >> fill > > > > > >> > > this > > > > > >> > > > > > > field. > > > > > >> > > > > > > > We > > > > > >> > > > > > > > > > can > > > > > >> > > > > > > > > > > > > > > guarantee > > > > > >> > > > > > > > > > > > > > > > that any EndTxn requests with the > > same > > > > > epoch > > > > > >> > are > > > > > >> > > > from > > > > > >> > > > > > the > > > > > >> > > > > > > > > same > > > > > >> > > > > > > > > > > > > producer > > > > > >> > > > > > > > > > > > > > > and > > > > > >> > > > > > > > > > > > > > > > the same transaction. > > > > > >> > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > 102. In prepare phase, we have the > > > same > > > > > >> > producer > > > > > >> > > ID > > > > > >> > > > > and > > > > > >> > > > > > > > epoch > > > > > >> > > > > > > > > > we > > > > > >> > > > > > > > > > > > > always > > > > > >> > > > > > > > > > > > > > > > had. It is the producer ID and > epoch > > > > that > > > > > >> are > > > > > >> > on > > > > > >> > > > the > > > > > >> > > > > > > > marker. > > > > > >> > > > > > > > > In > > > > > >> > > > > > > > > > > > > commit > > > > > >> > > > > > > > > > > > > > > > phase, we stay the same unless it > is > > > the > > > > > >> > overflow > > > > > >> > > > > case. > > > > > >> > > > > > > In > > > > > >> > > > > > > > > that > > > > > >> > > > > > > > > > > > case, > > > > > >> > > > > > > > > > > > > > we > > > > > >> > > > > > > > > > > > > > > > set the producer ID to the new one > > we > > > > > >> generated > > > > > >> > > and > > > > > >> > > > > > epoch > > > > > >> > > > > > > > to > > > > > >> > > > > > > > > 0 > > > > > >> > > > > > > > > > > > after > > > > > >> > > > > > > > > > > > > > > > complete. This is for downgrade > > > > > >> compatibility. > > > > > >> > > The > > > > > >> > > > > > tagged > > > > > >> > > > > > > > > > fields > > > > > >> > > > > > > > > > > > are > > > > > >> > > > > > > > > > > > > > just > > > > > >> > > > > > > > > > > > > > > > safety guards for retries and > > > failovers. > > > > > >> > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > In prepare phase for epoch > overflow > > > case > > > > > >> only > > > > > >> > we > > > > > >> > > > > store > > > > > >> > > > > > > the > > > > > >> > > > > > > > > next > > > > > >> > > > > > > > > > > > > > producer > > > > > >> > > > > > > > > > > > > > > > ID. This is for the case where we > > > reload > > > > > the > > > > > >> > > > > > transaction > > > > > >> > > > > > > > > > > > coordinator > > > > > >> > > > > > > > > > > > > in > > > > > >> > > > > > > > > > > > > > > > prepare state. Once the > transaction > > is > > > > > >> > committed, > > > > > >> > > > we > > > > > >> > > > > > can > > > > > >> > > > > > > > use > > > > > >> > > > > > > > > > the > > > > > >> > > > > > > > > > > > > > producer > > > > > >> > > > > > > > > > > > > > > > ID the client already is using. > > > > > >> > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > In commit phase, we store the > > previous > > > > > >> producer > > > > > >> > > ID > > > > > >> > > > in > > > > > >> > > > > > > case > > > > > >> > > > > > > > of > > > > > >> > > > > > > > > > > > > retries. > > > > > >> > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > I think it is easier to think of > it > > as > > > > > just > > > > > >> how > > > > > >> > > we > > > > > >> > > > > were > > > > > >> > > > > > > > > storing > > > > > >> > > > > > > > > > > > > > producer > > > > > >> > > > > > > > > > > > > > > ID > > > > > >> > > > > > > > > > > > > > > > and epoch before, with some extra > > > > > bookeeping > > > > > >> > and > > > > > >> > > > edge > > > > > >> > > > > > > case > > > > > >> > > > > > > > > > > handling > > > > > >> > > > > > > > > > > > > in > > > > > >> > > > > > > > > > > > > > > the > > > > > >> > > > > > > > > > > > > > > > tagged fields. We have to do it > this > > > way > > > > > for > > > > > >> > > > > > > compatibility > > > > > >> > > > > > > > > with > > > > > >> > > > > > > > > > > > > > > downgrades. > > > > > >> > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > 103. Next producer ID is for > prepare > > > > > status > > > > > >> and > > > > > >> > > > > > previous > > > > > >> > > > > > > > > > producer > > > > > >> > > > > > > > > > > > ID > > > > > >> > > > > > > > > > > > > is > > > > > >> > > > > > > > > > > > > > > for > > > > > >> > > > > > > > > > > > > > > > after complete. The reason why we > > need > > > > two > > > > > >> > > separate > > > > > >> > > > > > > > (tagged) > > > > > >> > > > > > > > > > > fields > > > > > >> > > > > > > > > > > > > is > > > > > >> > > > > > > > > > > > > > > for > > > > > >> > > > > > > > > > > > > > > > backwards compatibility. We need > to > > > keep > > > > > the > > > > > >> > same > > > > > >> > > > > > > semantics > > > > > >> > > > > > > > > for > > > > > >> > > > > > > > > > > the > > > > > >> > > > > > > > > > > > > > > > non-tagged field in case we > > downgrade. > > > > > >> > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > 104. We set the fields as we do in > > the > > > > > >> > > > transactional > > > > > >> > > > > > > state > > > > > >> > > > > > > > > (as > > > > > >> > > > > > > > > > we > > > > > >> > > > > > > > > > > > > need > > > > > >> > > > > > > > > > > > > > to > > > > > >> > > > > > > > > > > > > > > > do this for compatibility -- if we > > > > > >> downgrade, > > > > > >> > we > > > > > >> > > > will > > > > > >> > > > > > > only > > > > > >> > > > > > > > > have > > > > > >> > > > > > > > > > > the > > > > > >> > > > > > > > > > > > > > > > non-tagged fields) It will be the > > old > > > > > >> producer > > > > > >> > ID > > > > > >> > > > and > > > > > >> > > > > > max > > > > > >> > > > > > > > > > epoch. > > > > > >> > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > Hope this helps. Let me know if > you > > > have > > > > > >> > further > > > > > >> > > > > > > questions. > > > > > >> > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > Justine > > > > > >> > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > On Wed, Dec 20, 2023 at 3:33 PM > Jun > > > Rao > > > > > >> > > > > > > > > > <j...@confluent.io.invalid > > > > > >> > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > wrote: > > > > > >> > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > Hi, Justine, > > > > > >> > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > It seems that you have made some > > > > changes > > > > > >> to > > > > > >> > > > KIP-890 > > > > > >> > > > > > > since > > > > > >> > > > > > > > > the > > > > > >> > > > > > > > > > > > vote. > > > > > >> > > > > > > > > > > > > > In > > > > > >> > > > > > > > > > > > > > > > > particular, we are changing the > > > format > > > > > of > > > > > >> > > > > > > > > > TransactionLogValue. > > > > > >> > > > > > > > > > > A > > > > > >> > > > > > > > > > > > > few > > > > > >> > > > > > > > > > > > > > > > > comments related to that. > > > > > >> > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > 100. Just to be clear. The > > overflow > > > > case > > > > > >> > (i.e. > > > > > >> > > > > when a > > > > > >> > > > > > > new > > > > > >> > > > > > > > > > > > > producerId > > > > > >> > > > > > > > > > > > > > is > > > > > >> > > > > > > > > > > > > > > > > generated) is when the current > > epoch > > > > > >> equals > > > > > >> > to > > > > > >> > > > max > > > > > >> > > > > - > > > > > >> > > > > > 1 > > > > > >> > > > > > > > and > > > > > >> > > > > > > > > > not > > > > > >> > > > > > > > > > > > max? > > > > > >> > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > 101. For the "not epoch > overflow" > > > > case, > > > > > we > > > > > >> > > write > > > > > >> > > > > the > > > > > >> > > > > > > > > previous > > > > > >> > > > > > > > > > > ID > > > > > >> > > > > > > > > > > > in > > > > > >> > > > > > > > > > > > > > the > > > > > >> > > > > > > > > > > > > > > > > tagged field in the complete > > phase. > > > Do > > > > > we > > > > > >> > need > > > > > >> > > to > > > > > >> > > > > do > > > > > >> > > > > > > that > > > > > >> > > > > > > > > > since > > > > > >> > > > > > > > > > > > > > produce > > > > > >> > > > > > > > > > > > > > > > id > > > > > >> > > > > > > > > > > > > > > > > doesn't change in this case? > > > > > >> > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > 102. It seems that the meaning > for > > > the > > > > > >> > > > > > > > > > ProducerId/ProducerEpoch > > > > > >> > > > > > > > > > > > > > fields > > > > > >> > > > > > > > > > > > > > > in > > > > > >> > > > > > > > > > > > > > > > > TransactionLogValue changes > > > depending > > > > on > > > > > >> the > > > > > >> > > > > > > > > > TransactionStatus. > > > > > >> > > > > > > > > > > > > When > > > > > >> > > > > > > > > > > > > > > > > the TransactionStatus is > ongoing, > > > they > > > > > >> > > represent > > > > > >> > > > > the > > > > > >> > > > > > > > > current > > > > > >> > > > > > > > > > > > > > ProducerId > > > > > >> > > > > > > > > > > > > > > > and > > > > > >> > > > > > > > > > > > > > > > > the current ProducerEpoch. When > > the > > > > > >> > > > > TransactionStatus > > > > > >> > > > > > > is > > > > > >> > > > > > > > > > > > > > > > > PrepareCommit/PrepareAbort, they > > > > > represent > > > > > >> > the > > > > > >> > > > > > current > > > > > >> > > > > > > > > > > ProducerId > > > > > >> > > > > > > > > > > > > and > > > > > >> > > > > > > > > > > > > > > the > > > > > >> > > > > > > > > > > > > > > > > next ProducerEpoch. When the > > > > > >> > TransactionStatus > > > > > >> > > is > > > > > >> > > > > > > > > > Commit/Abort, > > > > > >> > > > > > > > > > > > > they > > > > > >> > > > > > > > > > > > > > > > > further depend on whether the > > epoch > > > > > >> overflows > > > > > >> > > or > > > > > >> > > > > not. > > > > > >> > > > > > > If > > > > > >> > > > > > > > > > there > > > > > >> > > > > > > > > > > is > > > > > >> > > > > > > > > > > > > no > > > > > >> > > > > > > > > > > > > > > > > overflow, they represent the > > > current > > > > > >> > > ProducerId > > > > > >> > > > > and > > > > > >> > > > > > > the > > > > > >> > > > > > > > > next > > > > > >> > > > > > > > > > > > > > > > ProducerEpoch > > > > > >> > > > > > > > > > > > > > > > > (max). Otherwise, they represent > > the > > > > > newly > > > > > >> > > > > generated > > > > > >> > > > > > > > > > ProducerId > > > > > >> > > > > > > > > > > > > and a > > > > > >> > > > > > > > > > > > > > > > > ProducerEpoch of 0. Is that > right? > > > > This > > > > > >> seems > > > > > >> > > not > > > > > >> > > > > > easy > > > > > >> > > > > > > to > > > > > >> > > > > > > > > > > > > understand. > > > > > >> > > > > > > > > > > > > > > > Could > > > > > >> > > > > > > > > > > > > > > > > we provide some examples like > what > > > > Artem > > > > > >> has > > > > > >> > > done > > > > > >> > > > > in > > > > > >> > > > > > > > > KIP-939? > > > > > >> > > > > > > > > > > > Have > > > > > >> > > > > > > > > > > > > we > > > > > >> > > > > > > > > > > > > > > > > considered a simpler design > where > > > > > >> > > > > > > > ProducerId/ProducerEpoch > > > > > >> > > > > > > > > > > always > > > > > >> > > > > > > > > > > > > > > > represent > > > > > >> > > > > > > > > > > > > > > > > the same value (e.g. for the > > current > > > > > >> > > transaction) > > > > > >> > > > > > > > > independent > > > > > >> > > > > > > > > > > of > > > > > >> > > > > > > > > > > > > the > > > > > >> > > > > > > > > > > > > > > > > TransactionStatus and epoch > > > overflow? > > > > > >> > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > 103. It's not clear to me why we > > > need > > > > 3 > > > > > >> > fields: > > > > > >> > > > > > > > ProducerId, > > > > > >> > > > > > > > > > > > > > > > PrevProducerId, > > > > > >> > > > > > > > > > > > > > > > > NextProducerId. Could we just > have > > > > > >> ProducerId > > > > > >> > > and > > > > > >> > > > > > > > > > > NextProducerId? > > > > > >> > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > 104. For WriteTxnMarkerRequests, > > if > > > > the > > > > > >> > > producer > > > > > >> > > > > > epoch > > > > > >> > > > > > > > > > > overflows, > > > > > >> > > > > > > > > > > > > > what > > > > > >> > > > > > > > > > > > > > > do > > > > > >> > > > > > > > > > > > > > > > > we set the producerId and the > > > > > >> producerEpoch? > > > > > >> > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > Thanks, > > > > > >> > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > Jun > > > > > >> > > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > > >> > > > > > > > > > > >> > > > > > > > > > >> > > > > > > > > >> > > > > > > > >> > > > > > > >> > > > > > > > > > > > > > > > > > > > > >
