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 > > >> > > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > > >> > > > > > > > > > > >> > > > > > > > > > >> > > > > > > > > >> > > > > > > > >> > > > > > > >> > > > > > >> > > > > >> > > > >> > > > > > >
