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