Hello Justine, Thanks for the great write-up! I made a quick pass through it and here are some thoughts (I have not been able to read through this thread so pardon me if they have overlapped or subsumed by previous comments):
First are some meta ones: 1. I think we need to also improve the client's experience once we have this defence in place. More concretely, say a user's producer code is like following: future = producer.send(); // producer.flush(); producer.commitTransaction(); future.get(); Which resulted in the order of a) produce-request sent by producer, b) end-txn-request sent by producer, c) end-txn-response sent back, d) txn-marker-request sent from coordinator to partition leader, e) produce-request finally received by the partition leader, before this KIP e) step would be accepted causing a dangling txn; now it would be rejected in step e) which is good. But from the client's point of view now it becomes confusing since the `commitTransaction()` returns successfully, but the "future" throws an invalid-epoch error, and they are not sure if the transaction did succeed or not. In fact, it "partially succeeded" with some msgs being rejected but others committed successfully. Of course the easy way to avoid this is, always call "producer.flush()" before commitTxn and that's what we do ourselves, and what we recommend users do. But I suspect not everyone does it. In fact I just checked the javadoc in KafkaProducer and our code snippet does not include a `flush()` call. So I'm thinking maybe we can in side the `commitTxn` code to enforce flushing before sending the end-txn request. 2. I'd like to clarify a bit details on "just add partitions to the transaction on the first produce request during a transaction". My understanding is that the partition leader's cache has the producer id / sequence / epoch for the latest txn, either on-going or is completed (upon receiving the marker request from coordinator). When a produce request is received, if * producer's epoch < cached epoch, or producer's epoch == cached epoch but the latest txn is completed, leader directly reject with invalid-epoch. * producer's epoch > cached epoch, park the the request and send add-partitions request to coordinator. In order to do it, does the coordinator need to bump the sequence and reset epoch to 0 when the next epoch is going to overflow? If no need to do so, then how we handle the (admittedly rare, but still may happen) epoch overflow situation? 3. I'm a bit concerned about adding a generic "ABORTABLE_ERROR" given we already have a pretty messy error classification and error handling on the producer clients side --- I have a summary about the issues and a proposal to address this in https://cwiki.apache.org/confluence/display/KAFKA/KIP-691%3A+Enhance+Transactional+Producer+Exception+Handling -- I understand we do not want to use "UNKNOWN_PRODUCER_ID" anymore and in fact we intend to deprecate it in KIP-360 and eventually remove it; but I'm wondering can we still use specific error codes. E.g. what about "InvalidProducerEpochException" since for new clients, the actual reason this would actually be rejected is indeed because the epoch on the coordinator caused the add-partitions-request from the brokers to be rejected anyways? 4. It seems we put the producer request into purgatory before we ever append the records, while other producer's records may still be appended during the time; and that potentially may result in some re-ordering compared with reception order. I'm not super concerned about it since Kafka does not guarantee reception ordering across producers anyways, but it may make the timestamps of records inside a partition to be more out-of-ordered. Are we aware of any scenarios such as future enhancements on log compactions that may be affected by this effect? Below are just minor comments: 5. In "AddPartitionsToTxnTransaction" field of "AddPartitionsToTxnRequest" RPC, the versions of those inner fields are "0-3" while I thought they should be "0+" still? 6. Regarding "we can place the request in a purgatory of sorts and check if there is any state for the transaction on the broker": i think at this time when we just do the checks against the cached state, we do not need to put the request to purgatory yet? 7. This is related to 3) above. I feel using "InvalidRecordException" for older clients may also be a bit confusing, and also it is not fatal -- for old clients, it better to be fatal since this indicates the clients is doing something wrong and hence it should be closed. And in general I'd prefer to use slightly more specific meaning error codes for clients. That being said, I also feel "InvalidProducerEpochException" is not suitable for old versioned clients, and we'd have to pick one that old clients recognize. I'd prefer "InvalidTxnStateException" but that one is supposed to be returned from txn coordinators only today. I'd suggest we do a quick check in the current client's code path and see if that one would be handled if it's from a produce-response, and if yes, use this one; otherwise, use "ProducerFencedException" which is much less meaningful but it's still a fatal error. Thanks, Guozhang On Wed, Jan 18, 2023 at 3:01 PM Justine Olshan <jols...@confluent.io.invalid> wrote: > > Yeah -- looks like we already have code to handle bumping the epoch and > when the epoch is Short.MAX_VALUE, we get a new producer ID. Since this is > already the behavior, do we want to change it further? > > Justine > > On Wed, Jan 18, 2023 at 1:12 PM Justine Olshan <jols...@confluent.io> wrote: > > > Hey all, just wanted to quickly update and say I've modified the KIP to > > explicitly mention that AddOffsetCommitsToTxnRequest will be replaced by > > a coordinator-side (inter-broker) AddPartitionsToTxn implicit request. This > > mirrors the user partitions and will implicitly add offset partitions to > > transactions when we commit offsets on them. We will deprecate > > AddOffsetCommitsToTxnRequest > > for new clients. > > > > Also to address Artem's comments -- > > I'm a bit unsure if the changes here will change the previous behavior for > > fencing producers. In the case you mention in the first paragraph, are you > > saying we bump the epoch before we try to abort the transaction? I think I > > need to understand the scenarios you mention a bit better. > > > > As for the second part -- I think it makes sense to have some sort of > > "sentinel" epoch to signal epoch is about to overflow (I think we sort of > > have this value in place in some ways) so we can codify it in the KIP. I'll > > look into that and try to update soon. > > > > Thanks, > > Justine. > > > > On Fri, Jan 13, 2023 at 5:01 PM Artem Livshits > > <alivsh...@confluent.io.invalid> wrote: > > > >> It's good to know that KIP-588 addressed some of the issues. Looking at > >> the code, it still looks like there are some cases that would result in > >> fatal error, e.g. PRODUCER_FENCED is issued by the transaction coordinator > >> if epoch doesn't match, and the client treats it as a fatal error (code in > >> TransactionManager request handling). If we consider, for example, > >> committing a transaction that returns a timeout, but actually succeeds, > >> trying to abort it or re-commit may result in PRODUCER_FENCED error > >> (because of epoch bump). > >> > >> For failed commits, specifically, we need to know the actual outcome, > >> because if we return an error the application may think that the > >> transaction is aborted and redo the work, leading to duplicates. > >> > >> Re: overflowing epoch. We could either do it on the TC and return both > >> producer id and epoch (e.g. change the protocol), or signal the client > >> that > >> it needs to get a new producer id. Checking for max epoch could be a > >> reasonable signal, the value to check should probably be present in the > >> KIP > >> as this is effectively a part of the contract. Also, the TC should > >> probably return an error if the client didn't change producer id after > >> hitting max epoch. > >> > >> -Artem > >> > >> > >> On Thu, Jan 12, 2023 at 10:31 AM Justine Olshan > >> <jols...@confluent.io.invalid> wrote: > >> > >> > Thanks for the discussion Artem. > >> > > >> > With respect to the handling of fenced producers, we have some behavior > >> > already in place. As of KIP-588: > >> > > >> > > >> https://cwiki.apache.org/confluence/display/KAFKA/KIP-588%3A+Allow+producers+to+recover+gracefully+from+transaction+timeouts > >> > , > >> > we handle timeouts more gracefully. The producer can recover. > >> > > >> > Produce requests can also recover from epoch fencing by aborting the > >> > transaction and starting over. > >> > > >> > What other cases were you considering that would cause us to have a > >> fenced > >> > epoch but we'd want to recover? > >> > > >> > The first point about handling epoch overflows is fair. I think there is > >> > some logic we'd need to consider. (ie, if we are one away from the max > >> > epoch, we need to reset the producer ID.) I'm still wondering if there > >> is a > >> > way to direct this from the response, or if everything should be done on > >> > the client side. Let me know if you have any thoughts here. > >> > > >> > Thanks, > >> > Justine > >> > > >> > On Tue, Jan 10, 2023 at 4:06 PM Artem Livshits > >> > <alivsh...@confluent.io.invalid> wrote: > >> > > >> > > There are some workflows in the client that are implied by protocol > >> > > changes, e.g.: > >> > > > >> > > - for new clients, epoch changes with every transaction and can > >> overflow, > >> > > in old clients this condition was handled transparently, because epoch > >> > was > >> > > bumped in InitProducerId and it would return a new producer id if > >> epoch > >> > > overflows, the new clients would need to implement some workflow to > >> > refresh > >> > > producer id > >> > > - how to handle fenced producers, for new clients epoch changes with > >> > every > >> > > transaction, so in presence of failures during commits / aborts, the > >> > > producer could get easily fenced, old clients would pretty much would > >> get > >> > > fenced when a new incarnation of the producer was initialized with > >> > > InitProducerId so it's ok to treat as a fatal error, the new clients > >> > would > >> > > need to implement some workflow to handle that error, otherwise they > >> > could > >> > > get fenced by themselves > >> > > - in particular (as a subset of the previous issue), what would the > >> > client > >> > > do if it got a timeout during commit? commit could've succeeded or > >> > failed > >> > > > >> > > Not sure if this has to be defined in the KIP as implementing those > >> > > probably wouldn't require protocol changes, but we have multiple > >> > > implementations of Kafka clients, so probably would be good to have > >> some > >> > > client implementation guidance. Could also be done as a separate doc. > >> > > > >> > > -Artem > >> > > > >> > > On Mon, Jan 9, 2023 at 3:38 PM Justine Olshan > >> > <jols...@confluent.io.invalid > >> > > > > >> > > wrote: > >> > > > >> > > > Hey all, I've updated the KIP to incorporate Jason's suggestions. > >> > > > > >> > > > > >> > > > > >> > > > >> > > >> https://cwiki.apache.org/confluence/display/KAFKA/KIP-890%3A+Transactions+Server-Side+Defense > >> > > > > >> > > > > >> > > > 1. Use AddPartitionsToTxn + verify flag to check on old clients > >> > > > 2. Updated AddPartitionsToTxn API to support transaction batching > >> > > > 3. Mention IBP bump > >> > > > 4. Mention auth change on new AddPartitionsToTxn version. > >> > > > > >> > > > I'm planning on opening a vote soon. > >> > > > Thanks, > >> > > > Justine > >> > > > > >> > > > On Fri, Jan 6, 2023 at 3:32 PM Justine Olshan <jols...@confluent.io > >> > > >> > > > wrote: > >> > > > > >> > > > > Thanks Jason. Those changes make sense to me. I will update the > >> KIP. > >> > > > > > >> > > > > > >> > > > > > >> > > > > On Fri, Jan 6, 2023 at 3:31 PM Jason Gustafson > >> > > > <ja...@confluent.io.invalid> > >> > > > > wrote: > >> > > > > > >> > > > >> Hey Justine, > >> > > > >> > >> > > > >> > I was wondering about compatibility here. When we send requests > >> > > > >> between brokers, we want to ensure that the receiving broker > >> > > understands > >> > > > >> the request (specifically the new fields). Typically this is done > >> > via > >> > > > >> IBP/metadata version. > >> > > > >> I'm trying to think if there is a way around it but I'm not sure > >> > there > >> > > > is. > >> > > > >> > >> > > > >> Yes. I think we would gate usage of this behind an IBP bump. Does > >> > that > >> > > > >> seem > >> > > > >> reasonable? > >> > > > >> > >> > > > >> > As for the improvements -- can you clarify how the multiple > >> > > > >> transactional > >> > > > >> IDs would help here? Were you thinking of a case where we > >> wait/batch > >> > > > >> multiple produce requests together? My understanding for now was > >> 1 > >> > > > >> transactional ID and one validation per 1 produce request. > >> > > > >> > >> > > > >> Each call to `AddPartitionsToTxn` is essentially a write to the > >> > > > >> transaction > >> > > > >> log and must block on replication. The more we can fit into a > >> single > >> > > > >> request, the more writes we can do in parallel. The alternative > >> is > >> > to > >> > > > make > >> > > > >> use of more connections, but usually we prefer batching since the > >> > > > network > >> > > > >> stack is not really optimized for high connection/request loads. > >> > > > >> > >> > > > >> > Finally with respect to the authorizations, I think it makes > >> sense > >> > > to > >> > > > >> skip > >> > > > >> topic authorizations, but I'm a bit confused by the "leader ID" > >> > field. > >> > > > >> Wouldn't we just want to flag the request as from a broker (does > >> it > >> > > > matter > >> > > > >> which one?). > >> > > > >> > >> > > > >> We could also make it version-based. For the next version, we > >> could > >> > > > >> require > >> > > > >> CLUSTER auth. So clients would not be able to use the API > >> anymore, > >> > > which > >> > > > >> is > >> > > > >> probably what we want. > >> > > > >> > >> > > > >> -Jason > >> > > > >> > >> > > > >> On Fri, Jan 6, 2023 at 10:43 AM Justine Olshan > >> > > > >> <jols...@confluent.io.invalid> > >> > > > >> wrote: > >> > > > >> > >> > > > >> > As a follow up, I was just thinking about the batching a bit > >> more. > >> > > > >> > I suppose if we have one request in flight and we queue up the > >> > other > >> > > > >> > produce requests in some sort of purgatory, we could send > >> > > information > >> > > > >> out > >> > > > >> > for all of them rather than one by one. So that would be a > >> benefit > >> > > of > >> > > > >> > batching partitions to add per transaction. > >> > > > >> > > >> > > > >> > I'll need to think a bit more on the design of this part of the > >> > KIP, > >> > > > and > >> > > > >> > will update the KIP in the next few days. > >> > > > >> > > >> > > > >> > Thanks, > >> > > > >> > Justine > >> > > > >> > > >> > > > >> > On Fri, Jan 6, 2023 at 10:22 AM Justine Olshan < > >> > > jols...@confluent.io> > >> > > > >> > wrote: > >> > > > >> > > >> > > > >> > > Hey Jason -- thanks for the input -- I was just digging a bit > >> > > deeper > >> > > > >> into > >> > > > >> > > the design + implementation of the validation calls here and > >> > what > >> > > > you > >> > > > >> say > >> > > > >> > > makes sense. > >> > > > >> > > > >> > > > >> > > I was wondering about compatibility here. When we send > >> requests > >> > > > >> > > between brokers, we want to ensure that the receiving broker > >> > > > >> understands > >> > > > >> > > the request (specifically the new fields). Typically this is > >> > done > >> > > > via > >> > > > >> > > IBP/metadata version. > >> > > > >> > > I'm trying to think if there is a way around it but I'm not > >> sure > >> > > > there > >> > > > >> > is. > >> > > > >> > > > >> > > > >> > > As for the improvements -- can you clarify how the multiple > >> > > > >> transactional > >> > > > >> > > IDs would help here? Were you thinking of a case where we > >> > > wait/batch > >> > > > >> > > multiple produce requests together? My understanding for now > >> > was 1 > >> > > > >> > > transactional ID and one validation per 1 produce request. > >> > > > >> > > > >> > > > >> > > Finally with respect to the authorizations, I think it makes > >> > sense > >> > > > to > >> > > > >> > skip > >> > > > >> > > topic authorizations, but I'm a bit confused by the "leader > >> ID" > >> > > > field. > >> > > > >> > > Wouldn't we just want to flag the request as from a broker > >> (does > >> > > it > >> > > > >> > matter > >> > > > >> > > which one?). > >> > > > >> > > > >> > > > >> > > I think I want to adopt these suggestions, just had a few > >> > > questions > >> > > > on > >> > > > >> > the > >> > > > >> > > details. > >> > > > >> > > > >> > > > >> > > Thanks, > >> > > > >> > > Justine > >> > > > >> > > > >> > > > >> > > On Thu, Jan 5, 2023 at 5:05 PM Jason Gustafson > >> > > > >> > <ja...@confluent.io.invalid> > >> > > > >> > > wrote: > >> > > > >> > > > >> > > > >> > >> Hi Justine, > >> > > > >> > >> > >> > > > >> > >> Thanks for the proposal. > >> > > > >> > >> > >> > > > >> > >> I was thinking about the implementation a little bit. In the > >> > > > current > >> > > > >> > >> proposal, the behavior depends on whether we have an old or > >> new > >> > > > >> client. > >> > > > >> > >> For > >> > > > >> > >> old clients, we send `DescribeTransactions` and verify the > >> > result > >> > > > and > >> > > > >> > for > >> > > > >> > >> new clients, we send `AddPartitionsToTxn`. We might be able > >> to > >> > > > >> simplify > >> > > > >> > >> the > >> > > > >> > >> implementation if we can use the same request type. For > >> > example, > >> > > > >> what if > >> > > > >> > >> we > >> > > > >> > >> bump the protocol version for `AddPartitionsToTxn` and add a > >> > > > >> > >> `validateOnly` > >> > > > >> > >> flag? For older versions, we can set `validateOnly=true` so > >> > that > >> > > > the > >> > > > >> > >> request only returns successfully if the partition had > >> already > >> > > been > >> > > > >> > added. > >> > > > >> > >> For new versions, we can set `validateOnly=false` and the > >> > > partition > >> > > > >> will > >> > > > >> > >> be > >> > > > >> > >> added to the transaction. The other slightly annoying thing > >> > that > >> > > > this > >> > > > >> > >> would > >> > > > >> > >> get around is the need to collect the transaction state for > >> all > >> > > > >> > partitions > >> > > > >> > >> even when we only care about a subset. > >> > > > >> > >> > >> > > > >> > >> Some additional improvements to consider: > >> > > > >> > >> > >> > > > >> > >> - We can give `AddPartitionsToTxn` better batch support for > >> > > > >> inter-broker > >> > > > >> > >> usage. Currently we only allow one `TransactionalId` to be > >> > > > specified, > >> > > > >> > but > >> > > > >> > >> the broker may get some benefit being able to batch across > >> > > multiple > >> > > > >> > >> transactions. > >> > > > >> > >> - Another small improvement is skipping topic authorization > >> > > checks > >> > > > >> for > >> > > > >> > >> `AddPartitionsToTxn` when the request is from a broker. > >> Perhaps > >> > > we > >> > > > >> can > >> > > > >> > add > >> > > > >> > >> a field for the `LeaderId` or something like that and > >> require > >> > > > CLUSTER > >> > > > >> > >> permission when set. > >> > > > >> > >> > >> > > > >> > >> Best, > >> > > > >> > >> Jason > >> > > > >> > >> > >> > > > >> > >> > >> > > > >> > >> > >> > > > >> > >> On Mon, Dec 19, 2022 at 3:56 PM Jun Rao > >> > <j...@confluent.io.invalid > >> > > > > >> > > > >> > wrote: > >> > > > >> > >> > >> > > > >> > >> > Hi, Justine, > >> > > > >> > >> > > >> > > > >> > >> > Thanks for the explanation. It makes sense to me now. > >> > > > >> > >> > > >> > > > >> > >> > Jun > >> > > > >> > >> > > >> > > > >> > >> > On Mon, Dec 19, 2022 at 1:42 PM Justine Olshan > >> > > > >> > >> > <jols...@confluent.io.invalid> > >> > > > >> > >> > wrote: > >> > > > >> > >> > > >> > > > >> > >> > > Hi Jun, > >> > > > >> > >> > > > >> > > > >> > >> > > My understanding of the mechanism is that when we get to > >> > the > >> > > > last > >> > > > >> > >> epoch, > >> > > > >> > >> > we > >> > > > >> > >> > > increment to the fencing/last epoch and if any further > >> > > requests > >> > > > >> come > >> > > > >> > >> in > >> > > > >> > >> > for > >> > > > >> > >> > > this producer ID they are fenced. Then the producer > >> gets a > >> > > new > >> > > > ID > >> > > > >> > and > >> > > > >> > >> > > restarts with epoch/sequence 0. The fenced epoch sticks > >> > > around > >> > > > >> for > >> > > > >> > the > >> > > > >> > >> > > duration of producer.id.expiration.ms and blocks any > >> late > >> > > > >> messages > >> > > > >> > >> > there. > >> > > > >> > >> > > The new ID will get to take advantage of the improved > >> > > semantics > >> > > > >> > around > >> > > > >> > >> > > non-zero start sequences. So I think we are covered. > >> > > > >> > >> > > > >> > > > >> > >> > > The only potential issue is overloading the cache, but > >> > > > hopefully > >> > > > >> the > >> > > > >> > >> > > improvements (lowered producer.id.expiration.ms) will > >> help > >> > > > with > >> > > > >> > that. > >> > > > >> > >> > Let > >> > > > >> > >> > > me know if you still have concerns. > >> > > > >> > >> > > > >> > > > >> > >> > > Thanks, > >> > > > >> > >> > > Justine > >> > > > >> > >> > > > >> > > > >> > >> > > On Mon, Dec 19, 2022 at 10:24 AM Jun Rao > >> > > > >> <j...@confluent.io.invalid> > >> > > > >> > >> > wrote: > >> > > > >> > >> > > > >> > > > >> > >> > > > Hi, Justine, > >> > > > >> > >> > > > > >> > > > >> > >> > > > Thanks for the explanation. > >> > > > >> > >> > > > > >> > > > >> > >> > > > 70. The proposed fencing logic doesn't apply when pid > >> > > > changes, > >> > > > >> is > >> > > > >> > >> that > >> > > > >> > >> > > > right? If so, I am not sure how complete we are > >> > addressing > >> > > > this > >> > > > >> > >> issue > >> > > > >> > >> > if > >> > > > >> > >> > > > the pid changes more frequently. > >> > > > >> > >> > > > > >> > > > >> > >> > > > Thanks, > >> > > > >> > >> > > > > >> > > > >> > >> > > > Jun > >> > > > >> > >> > > > > >> > > > >> > >> > > > > >> > > > >> > >> > > > > >> > > > >> > >> > > > On Fri, Dec 16, 2022 at 9:16 AM Justine Olshan > >> > > > >> > >> > > > <jols...@confluent.io.invalid> > >> > > > >> > >> > > > wrote: > >> > > > >> > >> > > > > >> > > > >> > >> > > > > Hi Jun, > >> > > > >> > >> > > > > > >> > > > >> > >> > > > > Thanks for replying! > >> > > > >> > >> > > > > > >> > > > >> > >> > > > > 70.We already do the overflow mechanism, so my > >> change > >> > > would > >> > > > >> just > >> > > > >> > >> make > >> > > > >> > >> > > it > >> > > > >> > >> > > > > happen more often. > >> > > > >> > >> > > > > I was also not suggesting a new field in the log, > >> but > >> > in > >> > > > the > >> > > > >> > >> > response, > >> > > > >> > >> > > > > which would be gated by the client version. Sorry if > >> > > > >> something > >> > > > >> > >> there > >> > > > >> > >> > is > >> > > > >> > >> > > > > unclear. I think we are starting to diverge. > >> > > > >> > >> > > > > The goal of this KIP is to not change to the marker > >> > > format > >> > > > at > >> > > > >> > all. > >> > > > >> > >> > > > > > >> > > > >> > >> > > > > 71. Yes, I guess I was going under the assumption > >> that > >> > > the > >> > > > >> log > >> > > > >> > >> would > >> > > > >> > >> > > just > >> > > > >> > >> > > > > look at its last epoch and treat it as the current > >> > > epoch. I > >> > > > >> > >> suppose > >> > > > >> > >> > we > >> > > > >> > >> > > > can > >> > > > >> > >> > > > > have some special logic that if the last epoch was > >> on a > >> > > > >> marker > >> > > > >> > we > >> > > > >> > >> > > > actually > >> > > > >> > >> > > > > expect the next epoch or something like that. We > >> just > >> > > need > >> > > > to > >> > > > >> > >> > > distinguish > >> > > > >> > >> > > > > based on whether we had a commit/abort marker. > >> > > > >> > >> > > > > > >> > > > >> > >> > > > > 72. > >> > > > >> > >> > > > > > if the producer epoch hasn't been bumped on the > >> > > > >> > >> > > > > broker, it seems that the stucked message will fail > >> the > >> > > > >> sequence > >> > > > >> > >> > > > validation > >> > > > >> > >> > > > > and will be ignored. If the producer epoch has been > >> > > bumped, > >> > > > >> we > >> > > > >> > >> ignore > >> > > > >> > >> > > the > >> > > > >> > >> > > > > sequence check and the stuck message could be > >> appended > >> > to > >> > > > the > >> > > > >> > log. > >> > > > >> > >> > So, > >> > > > >> > >> > > is > >> > > > >> > >> > > > > the latter case that we want to guard? > >> > > > >> > >> > > > > > >> > > > >> > >> > > > > I'm not sure I follow that "the message will fail > >> the > >> > > > >> sequence > >> > > > >> > >> > > > validation". > >> > > > >> > >> > > > > In some of these cases, we had an abort marker (due > >> to > >> > an > >> > > > >> error) > >> > > > >> > >> and > >> > > > >> > >> > > then > >> > > > >> > >> > > > > the late message comes in with the correct sequence > >> > > number. > >> > > > >> This > >> > > > >> > >> is a > >> > > > >> > >> > > > case > >> > > > >> > >> > > > > covered by the KIP. > >> > > > >> > >> > > > > The latter case is actually not something we've > >> > > considered > >> > > > >> > here. I > >> > > > >> > >> > > think > >> > > > >> > >> > > > > generally when we bump the epoch, we are accepting > >> that > >> > > the > >> > > > >> > >> sequence > >> > > > >> > >> > > does > >> > > > >> > >> > > > > not need to be checked anymore. My understanding is > >> > also > >> > > > >> that we > >> > > > >> > >> > don't > >> > > > >> > >> > > > > typically bump epoch mid transaction (based on a > >> quick > >> > > look > >> > > > >> at > >> > > > >> > the > >> > > > >> > >> > > code) > >> > > > >> > >> > > > > but let me know if that is the case. > >> > > > >> > >> > > > > > >> > > > >> > >> > > > > Thanks, > >> > > > >> > >> > > > > Justine > >> > > > >> > >> > > > > > >> > > > >> > >> > > > > On Thu, Dec 15, 2022 at 12:23 PM Jun Rao > >> > > > >> > <j...@confluent.io.invalid > >> > > > >> > >> > > >> > > > >> > >> > > > wrote: > >> > > > >> > >> > > > > > >> > > > >> > >> > > > > > Hi, Justine, > >> > > > >> > >> > > > > > > >> > > > >> > >> > > > > > Thanks for the reply. > >> > > > >> > >> > > > > > > >> > > > >> > >> > > > > > 70. Assigning a new pid on int overflow seems a > >> bit > >> > > > hacky. > >> > > > >> If > >> > > > >> > we > >> > > > >> > >> > > need a > >> > > > >> > >> > > > > txn > >> > > > >> > >> > > > > > level id, it will be better to model this > >> explicitly. > >> > > > >> Adding a > >> > > > >> > >> new > >> > > > >> > >> > > > field > >> > > > >> > >> > > > > > would require a bit more work since it requires a > >> new > >> > > txn > >> > > > >> > marker > >> > > > >> > >> > > format > >> > > > >> > >> > > > > in > >> > > > >> > >> > > > > > the log. So, we probably need to guard it with an > >> IBP > >> > > or > >> > > > >> > >> metadata > >> > > > >> > >> > > > version > >> > > > >> > >> > > > > > and document the impact on downgrade once the new > >> > > format > >> > > > is > >> > > > >> > >> written > >> > > > >> > >> > > to > >> > > > >> > >> > > > > the > >> > > > >> > >> > > > > > log. > >> > > > >> > >> > > > > > > >> > > > >> > >> > > > > > 71. Hmm, once the marker is written, the partition > >> > will > >> > > > >> expect > >> > > > >> > >> the > >> > > > >> > >> > > next > >> > > > >> > >> > > > > > append to be on the next epoch. Does that cover > >> the > >> > > case > >> > > > >> you > >> > > > >> > >> > > mentioned? > >> > > > >> > >> > > > > > > >> > > > >> > >> > > > > > 72. Also, just to be clear on the stucked message > >> > issue > >> > > > >> > >> described > >> > > > >> > >> > in > >> > > > >> > >> > > > the > >> > > > >> > >> > > > > > motivation. With EoS, we also validate the > >> sequence > >> > id > >> > > > for > >> > > > >> > >> > > idempotency. > >> > > > >> > >> > > > > So, > >> > > > >> > >> > > > > > with the current logic, if the producer epoch > >> hasn't > >> > > been > >> > > > >> > >> bumped on > >> > > > >> > >> > > the > >> > > > >> > >> > > > > > broker, it seems that the stucked message will > >> fail > >> > the > >> > > > >> > sequence > >> > > > >> > >> > > > > validation > >> > > > >> > >> > > > > > and will be ignored. If the producer epoch has > >> been > >> > > > >> bumped, we > >> > > > >> > >> > ignore > >> > > > >> > >> > > > the > >> > > > >> > >> > > > > > sequence check and the stuck message could be > >> > appended > >> > > to > >> > > > >> the > >> > > > >> > >> log. > >> > > > >> > >> > > So, > >> > > > >> > >> > > > is > >> > > > >> > >> > > > > > the latter case that we want to guard? > >> > > > >> > >> > > > > > > >> > > > >> > >> > > > > > Thanks, > >> > > > >> > >> > > > > > > >> > > > >> > >> > > > > > Jun > >> > > > >> > >> > > > > > > >> > > > >> > >> > > > > > On Wed, Dec 14, 2022 at 10:44 AM Justine Olshan > >> > > > >> > >> > > > > > <jols...@confluent.io.invalid> wrote: > >> > > > >> > >> > > > > > > >> > > > >> > >> > > > > > > Matthias — thanks again for taking time to look > >> a > >> > > this. > >> > > > >> You > >> > > > >> > >> said: > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > > My proposal was only focusing to avoid > >> dangling > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > transactions if records are added without > >> > registered > >> > > > >> > >> partition. > >> > > > >> > >> > -- > >> > > > >> > >> > > > > Maybe > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > you can add a few more details to the KIP about > >> > this > >> > > > >> > scenario > >> > > > >> > >> for > >> > > > >> > >> > > > > better > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > documentation purpose? > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > I'm not sure I understand what you mean here. > >> The > >> > > > >> motivation > >> > > > >> > >> > > section > >> > > > >> > >> > > > > > > describes two scenarios about how the record > >> can be > >> > > > added > >> > > > >> > >> > without a > >> > > > >> > >> > > > > > > registered partition: > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > > 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. > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > > Another way hanging transactions can occur is > >> > that > >> > > a > >> > > > >> > client > >> > > > >> > >> is > >> > > > >> > >> > > > buggy > >> > > > >> > >> > > > > > and > >> > > > >> > >> > > > > > > may somehow try to write to a partition before > >> it > >> > > adds > >> > > > >> the > >> > > > >> > >> > > partition > >> > > > >> > >> > > > to > >> > > > >> > >> > > > > > the > >> > > > >> > >> > > > > > > transaction. > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > For the first example of this would it be > >> helpful > >> > to > >> > > > say > >> > > > >> > that > >> > > > >> > >> > this > >> > > > >> > >> > > > > > message > >> > > > >> > >> > > > > > > comes in after the abort, but before the > >> partition > >> > is > >> > > > >> added > >> > > > >> > to > >> > > > >> > >> > the > >> > > > >> > >> > > > next > >> > > > >> > >> > > > > > > transaction so it becomes "hanging." Perhaps the > >> > next > >> > > > >> > sentence > >> > > > >> > >> > > > > describing > >> > > > >> > >> > > > > > > the message becoming part of the next > >> transaction > >> > (a > >> > > > >> > different > >> > > > >> > >> > > case) > >> > > > >> > >> > > > > was > >> > > > >> > >> > > > > > > not properly differentiated. > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > Jun — thanks for reading the KIP. > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > 70. The int typing was a concern. Currently we > >> > have a > >> > > > >> > >> mechanism > >> > > > >> > >> > in > >> > > > >> > >> > > > > place > >> > > > >> > >> > > > > > to > >> > > > >> > >> > > > > > > fence the final epoch when the epoch is about to > >> > > > overflow > >> > > > >> > and > >> > > > >> > >> > > assign > >> > > > >> > >> > > > a > >> > > > >> > >> > > > > > new > >> > > > >> > >> > > > > > > producer ID with epoch 0. Of course, this is a > >> bit > >> > > > tricky > >> > > > >> > >> when it > >> > > > >> > >> > > > comes > >> > > > >> > >> > > > > > to > >> > > > >> > >> > > > > > > the response back to the client. > >> > > > >> > >> > > > > > > Making this a long could be another option, but > >> I > >> > > > wonder > >> > > > >> are > >> > > > >> > >> > there > >> > > > >> > >> > > > any > >> > > > >> > >> > > > > > > implications on changing this field if the > >> epoch is > >> > > > >> > persisted > >> > > > >> > >> to > >> > > > >> > >> > > > disk? > >> > > > >> > >> > > > > > I'd > >> > > > >> > >> > > > > > > need to check the usages. > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > 71.This was something Matthias asked about as > >> > well. I > >> > > > was > >> > > > >> > >> > > > considering a > >> > > > >> > >> > > > > > > possible edge case where a produce request from > >> a > >> > new > >> > > > >> > >> transaction > >> > > > >> > >> > > > > somehow > >> > > > >> > >> > > > > > > gets sent right after the marker is written, but > >> > > before > >> > > > >> the > >> > > > >> > >> > > producer > >> > > > >> > >> > > > is > >> > > > >> > >> > > > > > > alerted of the newly bumped epoch. In this > >> case, we > >> > > may > >> > > > >> > >> include > >> > > > >> > >> > > this > >> > > > >> > >> > > > > > record > >> > > > >> > >> > > > > > > when we don't want to. I suppose we could try > >> to do > >> > > > >> > something > >> > > > >> > >> > > client > >> > > > >> > >> > > > > side > >> > > > >> > >> > > > > > > to bump the epoch after sending an endTxn as > >> well > >> > in > >> > > > this > >> > > > >> > >> > scenario > >> > > > >> > >> > > — > >> > > > >> > >> > > > > but > >> > > > >> > >> > > > > > I > >> > > > >> > >> > > > > > > wonder how it would work when the server is > >> > aborting > >> > > > >> based > >> > > > >> > on > >> > > > >> > >> a > >> > > > >> > >> > > > > > server-side > >> > > > >> > >> > > > > > > error. I could also be missing something and > >> this > >> > > > >> scenario > >> > > > >> > is > >> > > > >> > >> > > > actually > >> > > > >> > >> > > > > > not > >> > > > >> > >> > > > > > > possible. > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > Thanks again to everyone reading and commenting. > >> > Let > >> > > me > >> > > > >> know > >> > > > >> > >> > about > >> > > > >> > >> > > > any > >> > > > >> > >> > > > > > > further questions or comments. > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > Justine > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > On Wed, Dec 14, 2022 at 9:41 AM Jun Rao > >> > > > >> > >> <j...@confluent.io.invalid > >> > > > >> > >> > > > >> > > > >> > >> > > > > > wrote: > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > > Hi, Justine, > >> > > > >> > >> > > > > > > > > >> > > > >> > >> > > > > > > > Thanks for the KIP. A couple of comments. > >> > > > >> > >> > > > > > > > > >> > > > >> > >> > > > > > > > 70. Currently, the producer epoch is an int. > >> I am > >> > > not > >> > > > >> sure > >> > > > >> > >> if > >> > > > >> > >> > > it's > >> > > > >> > >> > > > > > enough > >> > > > >> > >> > > > > > > > to accommodate all transactions in the > >> lifetime > >> > of > >> > > a > >> > > > >> > >> producer. > >> > > > >> > >> > > > Should > >> > > > >> > >> > > > > > we > >> > > > >> > >> > > > > > > > change that to a long or add a new long field > >> > like > >> > > > >> txnId? > >> > > > >> > >> > > > > > > > > >> > > > >> > >> > > > > > > > 71. "it will write the prepare commit message > >> > with > >> > > a > >> > > > >> > bumped > >> > > > >> > >> > epoch > >> > > > >> > >> > > > and > >> > > > >> > >> > > > > > > send > >> > > > >> > >> > > > > > > > WriteTxnMarkerRequests with the bumped epoch." > >> > Hmm, > >> > > > the > >> > > > >> > >> epoch > >> > > > >> > >> > is > >> > > > >> > >> > > > > > > associated > >> > > > >> > >> > > > > > > > with the current txn right? So, it seems > >> weird to > >> > > > >> write a > >> > > > >> > >> > commit > >> > > > >> > >> > > > > > message > >> > > > >> > >> > > > > > > > with a bumped epoch. Should we only bump up > >> the > >> > > epoch > >> > > > >> in > >> > > > >> > >> > > > > EndTxnResponse > >> > > > >> > >> > > > > > > and > >> > > > >> > >> > > > > > > > rename the field to sth like > >> nextProducerEpoch? > >> > > > >> > >> > > > > > > > > >> > > > >> > >> > > > > > > > Thanks, > >> > > > >> > >> > > > > > > > > >> > > > >> > >> > > > > > > > Jun > >> > > > >> > >> > > > > > > > > >> > > > >> > >> > > > > > > > > >> > > > >> > >> > > > > > > > > >> > > > >> > >> > > > > > > > On Mon, Dec 12, 2022 at 8:54 PM Matthias J. > >> Sax < > >> > > > >> > >> > > mj...@apache.org> > >> > > > >> > >> > > > > > > wrote: > >> > > > >> > >> > > > > > > > > >> > > > >> > >> > > > > > > > > Thanks for the background. > >> > > > >> > >> > > > > > > > > > >> > > > >> > >> > > > > > > > > 20/30: SGTM. My proposal was only focusing > >> to > >> > > avoid > >> > > > >> > >> dangling > >> > > > >> > >> > > > > > > > > transactions if records are added without > >> > > > registered > >> > > > >> > >> > partition. > >> > > > >> > >> > > > -- > >> > > > >> > >> > > > > > > Maybe > >> > > > >> > >> > > > > > > > > you can add a few more details to the KIP > >> about > >> > > > this > >> > > > >> > >> scenario > >> > > > >> > >> > > for > >> > > > >> > >> > > > > > > better > >> > > > >> > >> > > > > > > > > documentation purpose? > >> > > > >> > >> > > > > > > > > > >> > > > >> > >> > > > > > > > > 40: I think you hit a fair point about race > >> > > > >> conditions > >> > > > >> > or > >> > > > >> > >> > > client > >> > > > >> > >> > > > > bugs > >> > > > >> > >> > > > > > > > > (incorrectly not bumping the epoch). The > >> > > > >> > >> complexity/confusion > >> > > > >> > >> > > for > >> > > > >> > >> > > > > > using > >> > > > >> > >> > > > > > > > > the bumped epoch I see, is mainly for > >> internal > >> > > > >> > debugging, > >> > > > >> > >> ie, > >> > > > >> > >> > > > > > > inspecting > >> > > > >> > >> > > > > > > > > log segment dumps -- it seems harder to > >> reason > >> > > > about > >> > > > >> the > >> > > > >> > >> > system > >> > > > >> > >> > > > for > >> > > > >> > >> > > > > > us > >> > > > >> > >> > > > > > > > > humans. But if we get better guarantees, it > >> > would > >> > > > be > >> > > > >> > >> worth to > >> > > > >> > >> > > use > >> > > > >> > >> > > > > the > >> > > > >> > >> > > > > > > > > bumped epoch. > >> > > > >> > >> > > > > > > > > > >> > > > >> > >> > > > > > > > > 60: as I mentioned already, I don't know the > >> > > broker > >> > > > >> > >> internals > >> > > > >> > >> > > to > >> > > > >> > >> > > > > > > provide > >> > > > >> > >> > > > > > > > > more input. So if nobody else chimes in, we > >> > > should > >> > > > >> just > >> > > > >> > >> move > >> > > > >> > >> > > > > forward > >> > > > >> > >> > > > > > > > > with your proposal. > >> > > > >> > >> > > > > > > > > > >> > > > >> > >> > > > > > > > > > >> > > > >> > >> > > > > > > > > -Matthias > >> > > > >> > >> > > > > > > > > > >> > > > >> > >> > > > > > > > > > >> > > > >> > >> > > > > > > > > On 12/6/22 4:22 PM, Justine Olshan wrote: > >> > > > >> > >> > > > > > > > > > Hi all, > >> > > > >> > >> > > > > > > > > > After Artem's questions about error > >> behavior, > >> > > > I've > >> > > > >> > >> > > re-evaluated > >> > > > >> > >> > > > > the > >> > > > >> > >> > > > > > > > > > unknown producer ID exception and had some > >> > > > >> discussions > >> > > > >> > >> > > offline. > >> > > > >> > >> > > > > > > > > > > >> > > > >> > >> > > > > > > > > > I think generally it makes sense to > >> simplify > >> > > > error > >> > > > >> > >> handling > >> > > > >> > >> > > in > >> > > > >> > >> > > > > > cases > >> > > > >> > >> > > > > > > > like > >> > > > >> > >> > > > > > > > > > this and the UNKNOWN_PRODUCER_ID error > >> has a > >> > > > pretty > >> > > > >> > long > >> > > > >> > >> > and > >> > > > >> > >> > > > > > > > complicated > >> > > > >> > >> > > > > > > > > > history. Because of this, I propose > >> adding a > >> > > new > >> > > > >> error > >> > > > >> > >> code > >> > > > >> > >> > > > > > > > > ABORTABLE_ERROR > >> > > > >> > >> > > > > > > > > > that when encountered by new clients > >> (gated > >> > by > >> > > > the > >> > > > >> > >> produce > >> > > > >> > >> > > > > request > >> > > > >> > >> > > > > > > > > version) > >> > > > >> > >> > > > > > > > > > will simply abort the transaction. This > >> > allows > >> > > > the > >> > > > >> > >> server > >> > > > >> > >> > to > >> > > > >> > >> > > > have > >> > > > >> > >> > > > > > > some > >> > > > >> > >> > > > > > > > > say > >> > > > >> > >> > > > > > > > > > in whether the client aborts and makes > >> > handling > >> > > > >> much > >> > > > >> > >> > simpler. > >> > > > >> > >> > > > In > >> > > > >> > >> > > > > > the > >> > > > >> > >> > > > > > > > > > future, we can also use this error in > >> other > >> > > > >> situations > >> > > > >> > >> > where > >> > > > >> > >> > > we > >> > > > >> > >> > > > > > want > >> > > > >> > >> > > > > > > to > >> > > > >> > >> > > > > > > > > > abort the transactions. We can even use on > >> > > other > >> > > > >> apis. > >> > > > >> > >> > > > > > > > > > > >> > > > >> > >> > > > > > > > > > I've added this to the KIP. Let me know if > >> > > there > >> > > > >> are > >> > > > >> > any > >> > > > >> > >> > > > > questions > >> > > > >> > >> > > > > > or > >> > > > >> > >> > > > > > > > > > issues. > >> > > > >> > >> > > > > > > > > > > >> > > > >> > >> > > > > > > > > > Justine > >> > > > >> > >> > > > > > > > > > > >> > > > >> > >> > > > > > > > > > On Fri, Dec 2, 2022 at 10:22 AM Justine > >> > Olshan > >> > > < > >> > > > >> > >> > > > > > jols...@confluent.io > >> > > > >> > >> > > > > > > > > >> > > > >> > >> > > > > > > > > wrote: > >> > > > >> > >> > > > > > > > > > > >> > > > >> > >> > > > > > > > > >> Hey Matthias, > >> > > > >> > >> > > > > > > > > >> > >> > > > >> > >> > > > > > > > > >> > >> > > > >> > >> > > > > > > > > >> 20/30 — Maybe I also didn't express > >> myself > >> > > > >> clearly. > >> > > > >> > For > >> > > > >> > >> > > older > >> > > > >> > >> > > > > > > clients > >> > > > >> > >> > > > > > > > we > >> > > > >> > >> > > > > > > > > >> don't have a way to distinguish between a > >> > > > previous > >> > > > >> > and > >> > > > >> > >> the > >> > > > >> > >> > > > > current > >> > > > >> > >> > > > > > > > > >> transaction since we don't have the epoch > >> > > bump. > >> > > > >> This > >> > > > >> > >> means > >> > > > >> > >> > > > that > >> > > > >> > >> > > > > a > >> > > > >> > >> > > > > > > late > >> > > > >> > >> > > > > > > > > >> message from the previous transaction > >> may be > >> > > > >> added to > >> > > > >> > >> the > >> > > > >> > >> > > new > >> > > > >> > >> > > > > one. > >> > > > >> > >> > > > > > > > With > >> > > > >> > >> > > > > > > > > >> older clients — we can't guarantee this > >> > won't > >> > > > >> happen > >> > > > >> > >> if we > >> > > > >> > >> > > > > already > >> > > > >> > >> > > > > > > > sent > >> > > > >> > >> > > > > > > > > the > >> > > > >> > >> > > > > > > > > >> addPartitionsToTxn call (why we make > >> changes > >> > > for > >> > > > >> the > >> > > > >> > >> newer > >> > > > >> > >> > > > > client) > >> > > > >> > >> > > > > > > but > >> > > > >> > >> > > > > > > > > we > >> > > > >> > >> > > > > > > > > >> can at least gate some by ensuring that > >> the > >> > > > >> partition > >> > > > >> > >> has > >> > > > >> > >> > > been > >> > > > >> > >> > > > > > added > >> > > > >> > >> > > > > > > > to > >> > > > >> > >> > > > > > > > > the > >> > > > >> > >> > > > > > > > > >> transaction. The rationale here is that > >> > there > >> > > > are > >> > > > >> > >> likely > >> > > > >> > >> > > LESS > >> > > > >> > >> > > > > late > >> > > > >> > >> > > > > > > > > arrivals > >> > > > >> > >> > > > > > > > > >> as time goes on, so hopefully most late > >> > > arrivals > >> > > > >> will > >> > > > >> > >> come > >> > > > >> > >> > > in > >> > > > >> > >> > > > > > BEFORE > >> > > > >> > >> > > > > > > > the > >> > > > >> > >> > > > > > > > > >> addPartitionsToTxn call. Those that > >> arrive > >> > > > before > >> > > > >> > will > >> > > > >> > >> be > >> > > > >> > >> > > > > properly > >> > > > >> > >> > > > > > > > gated > >> > > > >> > >> > > > > > > > > >> with the describeTransactions approach. > >> > > > >> > >> > > > > > > > > >> > >> > > > >> > >> > > > > > > > > >> If we take the approach you suggested, > >> ANY > >> > > late > >> > > > >> > arrival > >> > > > >> > >> > > from a > >> > > > >> > >> > > > > > > > previous > >> > > > >> > >> > > > > > > > > >> transaction will be added. And we don't > >> want > >> > > > >> that. I > >> > > > >> > >> also > >> > > > >> > >> > > > don't > >> > > > >> > >> > > > > > see > >> > > > >> > >> > > > > > > > any > >> > > > >> > >> > > > > > > > > >> benefit in sending addPartitionsToTxn > >> over > >> > the > >> > > > >> > >> > describeTxns > >> > > > >> > >> > > > > call. > >> > > > >> > >> > > > > > > They > >> > > > >> > >> > > > > > > > > will > >> > > > >> > >> > > > > > > > > >> both be one extra RPC to the Txn > >> > coordinator. > >> > > > >> > >> > > > > > > > > >> > >> > > > >> > >> > > > > > > > > >> > >> > > > >> > >> > > > > > > > > >> To be clear — newer clients will use > >> > > > >> > addPartitionsToTxn > >> > > > >> > >> > > > instead > >> > > > >> > >> > > > > of > >> > > > >> > >> > > > > > > the > >> > > > >> > >> > > > > > > > > >> DescribeTxns. > >> > > > >> > >> > > > > > > > > >> > >> > > > >> > >> > > > > > > > > >> > >> > > > >> > >> > > > > > > > > >> 40) > >> > > > >> > >> > > > > > > > > >> My concern is that if we have some delay > >> in > >> > > the > >> > > > >> > client > >> > > > >> > >> to > >> > > > >> > >> > > bump > >> > > > >> > >> > > > > the > >> > > > >> > >> > > > > > > > > epoch, > >> > > > >> > >> > > > > > > > > >> it could continue to send epoch 73 and > >> those > >> > > > >> records > >> > > > >> > >> would > >> > > > >> > >> > > not > >> > > > >> > >> > > > > be > >> > > > >> > >> > > > > > > > > fenced. > >> > > > >> > >> > > > > > > > > >> Perhaps this is not an issue if we don't > >> > allow > >> > > > the > >> > > > >> > next > >> > > > >> > >> > > > produce > >> > > > >> > >> > > > > to > >> > > > >> > >> > > > > > > go > >> > > > >> > >> > > > > > > > > >> through before the EndTxn request > >> returns. > >> > I'm > >> > > > >> also > >> > > > >> > >> > thinking > >> > > > >> > >> > > > > about > >> > > > >> > >> > > > > > > > > cases of > >> > > > >> > >> > > > > > > > > >> failure. I will need to think on this a > >> bit. > >> > > > >> > >> > > > > > > > > >> > >> > > > >> > >> > > > > > > > > >> I wasn't sure if it was that confusing. > >> But > >> > if > >> > > > we > >> > > > >> > >> think it > >> > > > >> > >> > > is, > >> > > > >> > >> > > > > we > >> > > > >> > >> > > > > > > can > >> > > > >> > >> > > > > > > > > >> investigate other ways. > >> > > > >> > >> > > > > > > > > >> > >> > > > >> > >> > > > > > > > > >> > >> > > > >> > >> > > > > > > > > >> 60) > >> > > > >> > >> > > > > > > > > >> > >> > > > >> > >> > > > > > > > > >> I'm not sure these are the same > >> purgatories > >> > > > since > >> > > > >> one > >> > > > >> > >> is a > >> > > > >> > >> > > > > produce > >> > > > >> > >> > > > > > > > > >> purgatory (I was planning on using a > >> > callback > >> > > > >> rather > >> > > > >> > >> than > >> > > > >> > >> > > > > > purgatory) > >> > > > >> > >> > > > > > > > and > >> > > > >> > >> > > > > > > > > >> the other is simply a request to append > >> to > >> > the > >> > > > >> log. > >> > > > >> > Not > >> > > > >> > >> > sure > >> > > > >> > >> > > > we > >> > > > >> > >> > > > > > have > >> > > > >> > >> > > > > > > > any > >> > > > >> > >> > > > > > > > > >> structure here for ordering, but my > >> > > > understanding > >> > > > >> is > >> > > > >> > >> that > >> > > > >> > >> > > the > >> > > > >> > >> > > > > > broker > >> > > > >> > >> > > > > > > > > could > >> > > > >> > >> > > > > > > > > >> handle the write request before it hears > >> > back > >> > > > from > >> > > > >> > the > >> > > > >> > >> Txn > >> > > > >> > >> > > > > > > > Coordinator. > >> > > > >> > >> > > > > > > > > >> > >> > > > >> > >> > > > > > > > > >> Let me know if I misunderstood something > >> or > >> > > > >> something > >> > > > >> > >> was > >> > > > >> > >> > > > > unclear. > >> > > > >> > >> > > > > > > > > >> > >> > > > >> > >> > > > > > > > > >> Justine > >> > > > >> > >> > > > > > > > > >> > >> > > > >> > >> > > > > > > > > >> On Thu, Dec 1, 2022 at 12:15 PM Matthias > >> J. > >> > > Sax > >> > > > < > >> > > > >> > >> > > > > mj...@apache.org > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > > > wrote: > >> > > > >> > >> > > > > > > > > >> > >> > > > >> > >> > > > > > > > > >>> Thanks for the details Justine! > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > >>>> 20) > >> > > > >> > >> > > > > > > > > >>>> > >> > > > >> > >> > > > > > > > > >>>> The client side change for 2 is > >> removing > >> > the > >> > > > >> > >> > addPartitions > >> > > > >> > >> > > > to > >> > > > >> > >> > > > > > > > > >>> transaction > >> > > > >> > >> > > > > > > > > >>>> call. We don't need to make this from > >> the > >> > > > >> producer > >> > > > >> > to > >> > > > >> > >> > the > >> > > > >> > >> > > > txn > >> > > > >> > >> > > > > > > > > >>> coordinator, > >> > > > >> > >> > > > > > > > > >>>> only server side. > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > >>> I think I did not express myself > >> clearly. I > >> > > > >> > understand > >> > > > >> > >> > that > >> > > > >> > >> > > > we > >> > > > >> > >> > > > > > can > >> > > > >> > >> > > > > > > > (and > >> > > > >> > >> > > > > > > > > >>> should) change the producer to not send > >> the > >> > > > >> > >> > `addPartitions` > >> > > > >> > >> > > > > > request > >> > > > >> > >> > > > > > > > any > >> > > > >> > >> > > > > > > > > >>> longer. But I don't thinks it's > >> requirement > >> > > to > >> > > > >> > change > >> > > > >> > >> the > >> > > > >> > >> > > > > broker? > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > >>> What I am trying to say is: as a > >> safe-guard > >> > > and > >> > > > >> > >> > improvement > >> > > > >> > >> > > > for > >> > > > >> > >> > > > > > > older > >> > > > >> > >> > > > > > > > > >>> producers, the partition leader can just > >> > send > >> > > > the > >> > > > >> > >> > > > > `addPartitions` > >> > > > >> > >> > > > > > > > > >>> request to the TX-coordinator in any > >> case > >> > -- > >> > > if > >> > > > >> the > >> > > > >> > >> old > >> > > > >> > >> > > > > producer > >> > > > >> > >> > > > > > > > > >>> correctly did send the `addPartition` > >> > request > >> > > > to > >> > > > >> the > >> > > > >> > >> > > > > > TX-coordinator > >> > > > >> > >> > > > > > > > > >>> already, the TX-coordinator can just > >> > "ignore" > >> > > > is > >> > > > >> as > >> > > > >> > >> > > > idempotent. > >> > > > >> > >> > > > > > > > > However, > >> > > > >> > >> > > > > > > > > >>> if the old producer has a bug and did > >> > forget > >> > > to > >> > > > >> sent > >> > > > >> > >> the > >> > > > >> > >> > > > > > > > `addPartition` > >> > > > >> > >> > > > > > > > > >>> request, we would now ensure that the > >> > > partition > >> > > > >> is > >> > > > >> > >> indeed > >> > > > >> > >> > > > added > >> > > > >> > >> > > > > > to > >> > > > >> > >> > > > > > > > the > >> > > > >> > >> > > > > > > > > >>> TX and thus fix a potential producer bug > >> > > (even > >> > > > >> if we > >> > > > >> > >> > don't > >> > > > >> > >> > > > get > >> > > > >> > >> > > > > > the > >> > > > >> > >> > > > > > > > > >>> fencing via the bump epoch). -- It > >> seems to > >> > > be > >> > > > a > >> > > > >> > good > >> > > > >> > >> > > > > > improvement? > >> > > > >> > >> > > > > > > Or > >> > > > >> > >> > > > > > > > > is > >> > > > >> > >> > > > > > > > > >>> there a reason to not do this? > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > >>>> 30) > >> > > > >> > >> > > > > > > > > >>>> > >> > > > >> > >> > > > > > > > > >>>> Transaction is ongoing = partition was > >> > added > >> > > > to > >> > > > >> > >> > > transaction > >> > > > >> > >> > > > > via > >> > > > >> > >> > > > > > > > > >>>> addPartitionsToTxn. We check this with > >> the > >> > > > >> > >> > > > > DescribeTransactions > >> > > > >> > >> > > > > > > > call. > >> > > > >> > >> > > > > > > > > >>> Let > >> > > > >> > >> > > > > > > > > >>>> me know if this wasn't sufficiently > >> > > explained > >> > > > >> here: > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > >>> If we do what I propose in (20), we > >> don't > >> > > > really > >> > > > >> > need > >> > > > >> > >> to > >> > > > >> > >> > > make > >> > > > >> > >> > > > > > this > >> > > > >> > >> > > > > > > > > >>> `DescribeTransaction` call, as the > >> > partition > >> > > > >> leader > >> > > > >> > >> adds > >> > > > >> > >> > > the > >> > > > >> > >> > > > > > > > partition > >> > > > >> > >> > > > > > > > > >>> for older clients and we get this check > >> for > >> > > > free. > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > >>>> 40) > >> > > > >> > >> > > > > > > > > >>>> > >> > > > >> > >> > > > > > > > > >>>> The idea here is that if any messages > >> > > somehow > >> > > > >> come > >> > > > >> > in > >> > > > >> > >> > > before > >> > > > >> > >> > > > > we > >> > > > >> > >> > > > > > > get > >> > > > >> > >> > > > > > > > > the > >> > > > >> > >> > > > > > > > > >>> new > >> > > > >> > >> > > > > > > > > >>>> epoch to the producer, they will be > >> > fenced. > >> > > > >> > However, > >> > > > >> > >> if > >> > > > >> > >> > we > >> > > > >> > >> > > > > don't > >> > > > >> > >> > > > > > > > think > >> > > > >> > >> > > > > > > > > >>> this > >> > > > >> > >> > > > > > > > > >>>> is necessary, it can be discussed > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > >>> I agree that we should have epoch > >> fencing. > >> > My > >> > > > >> > >> question is > >> > > > >> > >> > > > > > > different: > >> > > > >> > >> > > > > > > > > >>> Assume we are at epoch 73, and we have > >> an > >> > > > ongoing > >> > > > >> > >> > > > transaction, > >> > > > >> > >> > > > > > that > >> > > > >> > >> > > > > > > > is > >> > > > >> > >> > > > > > > > > >>> committed. It seems natural to write the > >> > > > "prepare > >> > > > >> > >> commit" > >> > > > >> > >> > > > > marker > >> > > > >> > >> > > > > > > and > >> > > > >> > >> > > > > > > > > the > >> > > > >> > >> > > > > > > > > >>> `WriteTxMarkerRequest` both with epoch > >> 73, > >> > > too, > >> > > > >> as > >> > > > >> > it > >> > > > >> > >> > > belongs > >> > > > >> > >> > > > > to > >> > > > >> > >> > > > > > > the > >> > > > >> > >> > > > > > > > > >>> current transaction. Of course, we now > >> also > >> > > > bump > >> > > > >> the > >> > > > >> > >> > epoch > >> > > > >> > >> > > > and > >> > > > >> > >> > > > > > > expect > >> > > > >> > >> > > > > > > > > >>> the next requests to have epoch 74, and > >> > would > >> > > > >> reject > >> > > > >> > >> an > >> > > > >> > >> > > > request > >> > > > >> > >> > > > > > > with > >> > > > >> > >> > > > > > > > > >>> epoch 73, as the corresponding TX for > >> epoch > >> > > 73 > >> > > > >> was > >> > > > >> > >> > already > >> > > > >> > >> > > > > > > committed. > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > >>> It seems you propose to write the > >> "prepare > >> > > > commit > >> > > > >> > >> marker" > >> > > > >> > >> > > and > >> > > > >> > >> > > > > > > > > >>> `WriteTxMarkerRequest` with epoch 74 > >> > though, > >> > > > what > >> > > > >> > >> would > >> > > > >> > >> > > work, > >> > > > >> > >> > > > > but > >> > > > >> > >> > > > > > > it > >> > > > >> > >> > > > > > > > > >>> seems confusing. Is there a reason why > >> we > >> > > would > >> > > > >> use > >> > > > >> > >> the > >> > > > >> > >> > > > bumped > >> > > > >> > >> > > > > > > epoch > >> > > > >> > >> > > > > > > > 74 > >> > > > >> > >> > > > > > > > > >>> instead of the current epoch 73? > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > >>>> 60) > >> > > > >> > >> > > > > > > > > >>>> > >> > > > >> > >> > > > > > > > > >>>> When we are checking if the > >> transaction is > >> > > > >> ongoing, > >> > > > >> > >> we > >> > > > >> > >> > > need > >> > > > >> > >> > > > to > >> > > > >> > >> > > > > > > make > >> > > > >> > >> > > > > > > > a > >> > > > >> > >> > > > > > > > > >>> round > >> > > > >> > >> > > > > > > > > >>>> trip from the leader partition to the > >> > > > >> transaction > >> > > > >> > >> > > > coordinator. > >> > > > >> > >> > > > > > In > >> > > > >> > >> > > > > > > > the > >> > > > >> > >> > > > > > > > > >>> time > >> > > > >> > >> > > > > > > > > >>>> we are waiting for this message to come > >> > > back, > >> > > > in > >> > > > >> > >> theory > >> > > > >> > >> > we > >> > > > >> > >> > > > > could > >> > > > >> > >> > > > > > > > have > >> > > > >> > >> > > > > > > > > >>> sent > >> > > > >> > >> > > > > > > > > >>>> a commit/abort call that would make the > >> > > > original > >> > > > >> > >> result > >> > > > >> > >> > of > >> > > > >> > >> > > > the > >> > > > >> > >> > > > > > > check > >> > > > >> > >> > > > > > > > > >>> out of > >> > > > >> > >> > > > > > > > > >>>> date. That is why we can check the > >> leader > >> > > > state > >> > > > >> > >> before > >> > > > >> > >> > we > >> > > > >> > >> > > > > write > >> > > > >> > >> > > > > > to > >> > > > >> > >> > > > > > > > the > >> > > > >> > >> > > > > > > > > >>> log. > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > >>> Thanks. Got it. > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > >>> However, is this really an issue? We put > >> > the > >> > > > >> produce > >> > > > >> > >> > > request > >> > > > >> > >> > > > in > >> > > > >> > >> > > > > > > > > >>> purgatory, so how could we process the > >> > > > >> > >> > > > `WriteTxnMarkerRequest` > >> > > > >> > >> > > > > > > first? > >> > > > >> > >> > > > > > > > > >>> Don't we need to put the > >> > > > `WriteTxnMarkerRequest` > >> > > > >> > into > >> > > > >> > >> > > > > purgatory, > >> > > > >> > >> > > > > > > too, > >> > > > >> > >> > > > > > > > > >>> for this case, and process both request > >> > > > in-order? > >> > > > >> > >> (Again, > >> > > > >> > >> > > my > >> > > > >> > >> > > > > > broker > >> > > > >> > >> > > > > > > > > >>> knowledge is limited and maybe we don't > >> > > > maintain > >> > > > >> > >> request > >> > > > >> > >> > > > order > >> > > > >> > >> > > > > > for > >> > > > >> > >> > > > > > > > this > >> > > > >> > >> > > > > > > > > >>> case, what seems to be an issue IMHO, > >> and I > >> > > am > >> > > > >> > >> wondering > >> > > > >> > >> > if > >> > > > >> > >> > > > > > > changing > >> > > > >> > >> > > > > > > > > >>> request handling to preserve order for > >> this > >> > > > case > >> > > > >> > >> might be > >> > > > >> > >> > > the > >> > > > >> > >> > > > > > > cleaner > >> > > > >> > >> > > > > > > > > >>> solution?) > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > >>> -Matthias > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > >>> On 11/30/22 3:28 PM, Artem Livshits > >> wrote: > >> > > > >> > >> > > > > > > > > >>>> Hi Justine, > >> > > > >> > >> > > > > > > > > >>>> > >> > > > >> > >> > > > > > > > > >>>> I think the interesting part is not in > >> > this > >> > > > >> logic > >> > > > >> > >> > (because > >> > > > >> > >> > > > it > >> > > > >> > >> > > > > > > tries > >> > > > >> > >> > > > > > > > to > >> > > > >> > >> > > > > > > > > >>>> figure out when UNKNOWN_PRODUCER_ID is > >> > > > retriable > >> > > > >> > and > >> > > > >> > >> if > >> > > > >> > >> > > it's > >> > > > >> > >> > > > > > > > > retryable, > >> > > > >> > >> > > > > > > > > >>>> it's definitely not fatal), but what > >> > happens > >> > > > >> when > >> > > > >> > >> this > >> > > > >> > >> > > logic > >> > > > >> > >> > > > > > > doesn't > >> > > > >> > >> > > > > > > > > >>> return > >> > > > >> > >> > > > > > > > > >>>> 'true' and falls through. In the old > >> > > clients > >> > > > it > >> > > > >> > >> seems > >> > > > >> > >> > to > >> > > > >> > >> > > be > >> > > > >> > >> > > > > > > fatal, > >> > > > >> > >> > > > > > > > if > >> > > > >> > >> > > > > > > > > >>> we > >> > > > >> > >> > > > > > > > > >>>> keep the behavior in the new clients, > >> I'd > >> > > > >> expect it > >> > > > >> > >> > would > >> > > > >> > >> > > be > >> > > > >> > >> > > > > > fatal > >> > > > >> > >> > > > > > > > as > >> > > > >> > >> > > > > > > > > >>> well. > >> > > > >> > >> > > > > > > > > >>>> > >> > > > >> > >> > > > > > > > > >>>> -Artem > >> > > > >> > >> > > > > > > > > >>>> > >> > > > >> > >> > > > > > > > > >>>> On Tue, Nov 29, 2022 at 11:57 AM > >> Justine > >> > > > Olshan > >> > > > >> > >> > > > > > > > > >>>> <jols...@confluent.io.invalid> wrote: > >> > > > >> > >> > > > > > > > > >>>> > >> > > > >> > >> > > > > > > > > >>>>> Hi Artem and Jeff, > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> Thanks for taking a look and sorry for > >> > the > >> > > > slow > >> > > > >> > >> > response. > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> You both mentioned the change to > >> handle > >> > > > >> > >> > > UNKNOWN_PRODUCER_ID > >> > > > >> > >> > > > > > > errors. > >> > > > >> > >> > > > > > > > > To > >> > > > >> > >> > > > > > > > > >>> be > >> > > > >> > >> > > > > > > > > >>>>> clear — this error code will only be > >> sent > >> > > > again > >> > > > >> > when > >> > > > >> > >> > the > >> > > > >> > >> > > > > > client's > >> > > > >> > >> > > > > > > > > >>> request > >> > > > >> > >> > > > > > > > > >>>>> version is high enough to ensure we > >> > handle > >> > > it > >> > > > >> > >> > correctly. > >> > > > >> > >> > > > > > > > > >>>>> The current (Java) client handles > >> this by > >> > > the > >> > > > >> > >> following > >> > > > >> > >> > > > > > (somewhat > >> > > > >> > >> > > > > > > > > long) > >> > > > >> > >> > > > > > > > > >>>>> code snippet: > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> // An UNKNOWN_PRODUCER_ID means that > >> we > >> > > have > >> > > > >> lost > >> > > > >> > >> the > >> > > > >> > >> > > > > producer > >> > > > >> > >> > > > > > > > state > >> > > > >> > >> > > > > > > > > >>> on the > >> > > > >> > >> > > > > > > > > >>>>> broker. Depending on the log start > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> // offset, we may want to retry > >> these, as > >> > > > >> > described > >> > > > >> > >> for > >> > > > >> > >> > > > each > >> > > > >> > >> > > > > > case > >> > > > >> > >> > > > > > > > > >>> below. If > >> > > > >> > >> > > > > > > > > >>>>> none of those apply, then for the > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> // idempotent producer, we will > >> locally > >> > > bump > >> > > > >> the > >> > > > >> > >> epoch > >> > > > >> > >> > > and > >> > > > >> > >> > > > > > reset > >> > > > >> > >> > > > > > > > the > >> > > > >> > >> > > > > > > > > >>>>> sequence numbers of in-flight batches > >> > from > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> // sequence 0, then retry the failed > >> > batch, > >> > > > >> which > >> > > > >> > >> > should > >> > > > >> > >> > > > now > >> > > > >> > >> > > > > > > > succeed. > >> > > > >> > >> > > > > > > > > >>> For > >> > > > >> > >> > > > > > > > > >>>>> the transactional producer, allow the > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> // batch to fail. When processing the > >> > > failed > >> > > > >> > batch, > >> > > > >> > >> we > >> > > > >> > >> > > will > >> > > > >> > >> > > > > > > > > transition > >> > > > >> > >> > > > > > > > > >>> to > >> > > > >> > >> > > > > > > > > >>>>> an abortable error and set a flag > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> // indicating that we need to bump the > >> > > epoch > >> > > > >> (if > >> > > > >> > >> > > supported > >> > > > >> > >> > > > by > >> > > > >> > >> > > > > > the > >> > > > >> > >> > > > > > > > > >>> broker). > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> if (error == > >> > Errors.*UNKNOWN_PRODUCER_ID*) > >> > > { > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> if (response.logStartOffset == > >> -1) > >> > { > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> // We don't know the log > >> start > >> > > > offset > >> > > > >> > with > >> > > > >> > >> > this > >> > > > >> > >> > > > > > > response. > >> > > > >> > >> > > > > > > > > We > >> > > > >> > >> > > > > > > > > >>> should > >> > > > >> > >> > > > > > > > > >>>>> just retry the request until we get > >> it. > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> // The UNKNOWN_PRODUCER_ID > >> > error > >> > > > code > >> > > > >> > was > >> > > > >> > >> > added > >> > > > >> > >> > > > > along > >> > > > >> > >> > > > > > > > with > >> > > > >> > >> > > > > > > > > >>> the new > >> > > > >> > >> > > > > > > > > >>>>> ProduceResponse which includes the > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> // logStartOffset. So the > >> '-1' > >> > > > >> sentinel > >> > > > >> > is > >> > > > >> > >> > not > >> > > > >> > >> > > > for > >> > > > >> > >> > > > > > > > backward > >> > > > >> > >> > > > > > > > > >>>>> compatibility. Instead, it is possible > >> > for > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> // a broker to not know the > >> > > > >> > >> logStartOffset at > >> > > > >> > >> > > > when > >> > > > >> > >> > > > > it > >> > > > >> > >> > > > > > > is > >> > > > >> > >> > > > > > > > > >>> returning > >> > > > >> > >> > > > > > > > > >>>>> the response because the partition > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> // may have moved away from > >> the > >> > > > >> broker > >> > > > >> > >> from > >> > > > >> > >> > the > >> > > > >> > >> > > > > time > >> > > > >> > >> > > > > > > the > >> > > > >> > >> > > > > > > > > >>> error was > >> > > > >> > >> > > > > > > > > >>>>> initially raised to the time the > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> // response was being > >> > > constructed. > >> > > > In > >> > > > >> > >> these > >> > > > >> > >> > > > cases, > >> > > > >> > >> > > > > we > >> > > > >> > >> > > > > > > > > should > >> > > > >> > >> > > > > > > > > >>> just > >> > > > >> > >> > > > > > > > > >>>>> retry the request: we are guaranteed > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> // to eventually get a > >> > > > logStartOffset > >> > > > >> > once > >> > > > >> > >> > > things > >> > > > >> > >> > > > > > > settle > >> > > > >> > >> > > > > > > > > down. > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> return true; > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> } > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> if > >> (batch.sequenceHasBeenReset()) { > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> // When the first inflight > >> > batch > >> > > > >> fails > >> > > > >> > >> due to > >> > > > >> > >> > > the > >> > > > >> > >> > > > > > > > > truncation > >> > > > >> > >> > > > > > > > > >>> case, > >> > > > >> > >> > > > > > > > > >>>>> then the sequences of all the other > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> // in flight batches would > >> have > >> > > > been > >> > > > >> > >> > restarted > >> > > > >> > >> > > > from > >> > > > >> > >> > > > > > the > >> > > > >> > >> > > > > > > > > >>> beginning. > >> > > > >> > >> > > > > > > > > >>>>> However, when those responses > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> // come back from the > >> broker, > >> > > they > >> > > > >> would > >> > > > >> > >> also > >> > > > >> > >> > > > come > >> > > > >> > >> > > > > > with > >> > > > >> > >> > > > > > > > an > >> > > > >> > >> > > > > > > > > >>>>> UNKNOWN_PRODUCER_ID error. In this > >> case, > >> > we > >> > > > >> should > >> > > > >> > >> not > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> // reset the sequence > >> numbers > >> > to > >> > > > the > >> > > > >> > >> > beginning. > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> return true; > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> } else if > >> > > > >> > >> > > > > (lastAckedOffset(batch.topicPartition).orElse( > >> > > > >> > >> > > > > > > > > >>>>> *NO_LAST_ACKED_SEQUENCE_NUMBER*) < > >> > > > >> > >> > > > response.logStartOffset) { > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> // The head of the log has > >> been > >> > > > >> removed, > >> > > > >> > >> > > probably > >> > > > >> > >> > > > > due > >> > > > >> > >> > > > > > > to > >> > > > >> > >> > > > > > > > > the > >> > > > >> > >> > > > > > > > > >>>>> retention time elapsing. In this case, > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> // we expect to lose the > >> > producer > >> > > > >> state. > >> > > > >> > >> For > >> > > > >> > >> > > the > >> > > > >> > >> > > > > > > > > transactional > >> > > > >> > >> > > > > > > > > >>>>> producer, reset the sequences of all > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> // inflight batches to be > >> from > >> > > the > >> > > > >> > >> beginning > >> > > > >> > >> > > and > >> > > > >> > >> > > > > > retry > >> > > > >> > >> > > > > > > > > them, > >> > > > >> > >> > > > > > > > > >>> so > >> > > > >> > >> > > > > > > > > >>>>> that the transaction does not need to > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> // be aborted. For the > >> > idempotent > >> > > > >> > >> producer, > >> > > > >> > >> > > bump > >> > > > >> > >> > > > > the > >> > > > >> > >> > > > > > > > epoch > >> > > > >> > >> > > > > > > > > to > >> > > > >> > >> > > > > > > > > >>> avoid > >> > > > >> > >> > > > > > > > > >>>>> reusing (sequence, epoch) pairs > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> if (isTransactional()) { > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > >> > > > txnPartitionMap.startSequencesAtBeginning(batch.topicPartition, > >> > > > >> > >> > > > > > > > > >>>>> this.producerIdAndEpoch); > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> } else { > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > >> requestEpochBumpForPartition(batch.topicPartition); > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> } > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> return true; > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> } > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> if (!isTransactional()) { > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> // For the idempotent > >> producer, > >> > > > >> always > >> > > > >> > >> retry > >> > > > >> > >> > > > > > > > > >>> UNKNOWN_PRODUCER_ID > >> > > > >> > >> > > > > > > > > >>>>> errors. If the batch has the current > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> // producer ID and epoch, > >> > > request a > >> > > > >> bump > >> > > > >> > >> of > >> > > > >> > >> > the > >> > > > >> > >> > > > > > epoch. > >> > > > >> > >> > > > > > > > > >>> Otherwise > >> > > > >> > >> > > > > > > > > >>>>> just retry the produce. > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > requestEpochBumpForPartition(batch.topicPartition); > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> return true; > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> } > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> } > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> I was considering keeping this > >> behavior — > >> > > but > >> > > > >> am > >> > > > >> > >> open > >> > > > >> > >> > to > >> > > > >> > >> > > > > > > > simplifying > >> > > > >> > >> > > > > > > > > >>> it. > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> We are leaving changes to older > >> clients > >> > off > >> > > > the > >> > > > >> > >> table > >> > > > >> > >> > > here > >> > > > >> > >> > > > > > since > >> > > > >> > >> > > > > > > it > >> > > > >> > >> > > > > > > > > >>> caused > >> > > > >> > >> > > > > > > > > >>>>> many issues for clients in the past. > >> > > > Previously > >> > > > >> > this > >> > > > >> > >> > was > >> > > > >> > >> > > a > >> > > > >> > >> > > > > > fatal > >> > > > >> > >> > > > > > > > > error > >> > > > >> > >> > > > > > > > > >>> and > >> > > > >> > >> > > > > > > > > >>>>> we didn't have the mechanisms in > >> place to > >> > > > >> detect > >> > > > >> > >> when > >> > > > >> > >> > > this > >> > > > >> > >> > > > > was > >> > > > >> > >> > > > > > a > >> > > > >> > >> > > > > > > > > >>> legitimate > >> > > > >> > >> > > > > > > > > >>>>> case vs some bug or gap in the > >> protocol. > >> > > > >> Ensuring > >> > > > >> > >> each > >> > > > >> > >> > > > > > > transaction > >> > > > >> > >> > > > > > > > > has > >> > > > >> > >> > > > > > > > > >>> its > >> > > > >> > >> > > > > > > > > >>>>> own epoch should close this gap. > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> And to address Jeff's second point: > >> > > > >> > >> > > > > > > > > >>>>> *does the typical produce request path > >> > > append > >> > > > >> > >> records > >> > > > >> > >> > to > >> > > > >> > >> > > > > local > >> > > > >> > >> > > > > > > log > >> > > > >> > >> > > > > > > > > >>> along* > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> *with the currentTxnFirstOffset > >> > > information? > >> > > > I > >> > > > >> > would > >> > > > >> > >> > like > >> > > > >> > >> > > > to > >> > > > >> > >> > > > > > > > > >>> understand* > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> *when the field is written to disk.* > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> Yes, the first produce request > >> populates > >> > > this > >> > > > >> > field > >> > > > >> > >> and > >> > > > >> > >> > > > > writes > >> > > > >> > >> > > > > > > the > >> > > > >> > >> > > > > > > > > >>> offset > >> > > > >> > >> > > > > > > > > >>>>> as part of the record batch and also > >> to > >> > the > >> > > > >> > producer > >> > > > >> > >> > > state > >> > > > >> > >> > > > > > > > snapshot. > >> > > > >> > >> > > > > > > > > >>> When > >> > > > >> > >> > > > > > > > > >>>>> we reload the records on restart > >> and/or > >> > > > >> > >> reassignment, > >> > > > >> > >> > we > >> > > > >> > >> > > > > > > repopulate > >> > > > >> > >> > > > > > > > > >>> this > >> > > > >> > >> > > > > > > > > >>>>> field with the snapshot from disk > >> along > >> > > with > >> > > > >> the > >> > > > >> > >> rest > >> > > > >> > >> > of > >> > > > >> > >> > > > the > >> > > > >> > >> > > > > > > > producer > >> > > > >> > >> > > > > > > > > >>>>> state. > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> Let me know if there are further > >> comments > >> > > > >> and/or > >> > > > >> > >> > > questions. > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> Thanks, > >> > > > >> > >> > > > > > > > > >>>>> Justine > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>> On Tue, Nov 22, 2022 at 9:00 PM Jeff > >> Kim > >> > > > >> > >> > > > > > > > > <jeff....@confluent.io.invalid > >> > > > >> > >> > > > > > > > > >>>> > >> > > > >> > >> > > > > > > > > >>>>> wrote: > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>>>> Hi Justine, > >> > > > >> > >> > > > > > > > > >>>>>> > >> > > > >> > >> > > > > > > > > >>>>>> Thanks for the KIP! I have two > >> > questions: > >> > > > >> > >> > > > > > > > > >>>>>> > >> > > > >> > >> > > > > > > > > >>>>>> 1) For new clients, we can once again > >> > > return > >> > > > >> an > >> > > > >> > >> error > >> > > > >> > >> > > > > > > > > >>> UNKNOWN_PRODUCER_ID > >> > > > >> > >> > > > > > > > > >>>>>> for sequences > >> > > > >> > >> > > > > > > > > >>>>>> that are non-zero when there is no > >> > > producer > >> > > > >> state > >> > > > >> > >> > > present > >> > > > >> > >> > > > on > >> > > > >> > >> > > > > > the > >> > > > >> > >> > > > > > > > > >>> server. > >> > > > >> > >> > > > > > > > > >>>>>> This will indicate we missed the 0 > >> > > sequence > >> > > > >> and > >> > > > >> > we > >> > > > >> > >> > don't > >> > > > >> > >> > > > yet > >> > > > >> > >> > > > > > > want > >> > > > >> > >> > > > > > > > to > >> > > > >> > >> > > > > > > > > >>>>> write > >> > > > >> > >> > > > > > > > > >>>>>> to the log. > >> > > > >> > >> > > > > > > > > >>>>>> > >> > > > >> > >> > > > > > > > > >>>>>> I would like to understand the > >> current > >> > > > >> behavior > >> > > > >> > to > >> > > > >> > >> > > handle > >> > > > >> > >> > > > > > older > >> > > > >> > >> > > > > > > > > >>> clients, > >> > > > >> > >> > > > > > > > > >>>>>> and if there are any changes we are > >> > > making. > >> > > > >> Maybe > >> > > > >> > >> I'm > >> > > > >> > >> > > > > missing > >> > > > >> > >> > > > > > > > > >>> something, > >> > > > >> > >> > > > > > > > > >>>>>> but we would want to identify > >> whether we > >> > > > >> missed > >> > > > >> > >> the 0 > >> > > > >> > >> > > > > sequence > >> > > > >> > >> > > > > > > for > >> > > > >> > >> > > > > > > > > >>> older > >> > > > >> > >> > > > > > > > > >>>>>> clients, no? > >> > > > >> > >> > > > > > > > > >>>>>> > >> > > > >> > >> > > > > > > > > >>>>>> 2) Upon returning from the > >> transaction > >> > > > >> > >> coordinator, we > >> > > > >> > >> > > can > >> > > > >> > >> > > > > set > >> > > > >> > >> > > > > > > the > >> > > > >> > >> > > > > > > > > >>>>>> transaction > >> > > > >> > >> > > > > > > > > >>>>>> as ongoing on the leader by > >> populating > >> > > > >> > >> > > > currentTxnFirstOffset > >> > > > >> > >> > > > > > > > > >>>>>> through the typical produce request > >> > > > handling. > >> > > > >> > >> > > > > > > > > >>>>>> > >> > > > >> > >> > > > > > > > > >>>>>> does the typical produce request path > >> > > append > >> > > > >> > >> records > >> > > > >> > >> > to > >> > > > >> > >> > > > > local > >> > > > >> > >> > > > > > > log > >> > > > >> > >> > > > > > > > > >>> along > >> > > > >> > >> > > > > > > > > >>>>>> with the currentTxnFirstOffset > >> > > information? > >> > > > I > >> > > > >> > would > >> > > > >> > >> > like > >> > > > >> > >> > > > to > >> > > > >> > >> > > > > > > > > understand > >> > > > >> > >> > > > > > > > > >>>>>> when the field is written to disk. > >> > > > >> > >> > > > > > > > > >>>>>> > >> > > > >> > >> > > > > > > > > >>>>>> Thanks, > >> > > > >> > >> > > > > > > > > >>>>>> Jeff > >> > > > >> > >> > > > > > > > > >>>>>> > >> > > > >> > >> > > > > > > > > >>>>>> > >> > > > >> > >> > > > > > > > > >>>>>> On Tue, Nov 22, 2022 at 4:44 PM Artem > >> > > > Livshits > >> > > > >> > >> > > > > > > > > >>>>>> <alivsh...@confluent.io.invalid> > >> wrote: > >> > > > >> > >> > > > > > > > > >>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>> Hi Justine, > >> > > > >> > >> > > > > > > > > >>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>> Thank you for the KIP. I have one > >> > > > question. > >> > > > >> > >> > > > > > > > > >>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>> 5) For new clients, we can once > >> again > >> > > > return > >> > > > >> an > >> > > > >> > >> error > >> > > > >> > >> > > > > > > > > >>>>> UNKNOWN_PRODUCER_ID > >> > > > >> > >> > > > > > > > > >>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>> I believe we had problems in the > >> past > >> > > with > >> > > > >> > >> returning > >> > > > >> > >> > > > > > > > > >>>>> UNKNOWN_PRODUCER_ID > >> > > > >> > >> > > > > > > > > >>>>>>> because it was considered fatal and > >> > > > required > >> > > > >> > >> client > >> > > > >> > >> > > > > restart. > >> > > > >> > >> > > > > > > It > >> > > > >> > >> > > > > > > > > >>> would > >> > > > >> > >> > > > > > > > > >>>>> be > >> > > > >> > >> > > > > > > > > >>>>>>> good to spell out the new client > >> > behavior > >> > > > >> when > >> > > > >> > it > >> > > > >> > >> > > > receives > >> > > > >> > >> > > > > > the > >> > > > >> > >> > > > > > > > > error. > >> > > > >> > >> > > > > > > > > >>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>> -Artem > >> > > > >> > >> > > > > > > > > >>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>> On Tue, Nov 22, 2022 at 10:00 AM > >> > Justine > >> > > > >> Olshan > >> > > > >> > >> > > > > > > > > >>>>>>> <jols...@confluent.io.invalid> > >> wrote: > >> > > > >> > >> > > > > > > > > >>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> Thanks for taking a look Matthias. > >> > I've > >> > > > >> tried > >> > > > >> > to > >> > > > >> > >> > > answer > >> > > > >> > >> > > > > your > >> > > > >> > >> > > > > > > > > >>>>> questions > >> > > > >> > >> > > > > > > > > >>>>>>>> below: > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> 10) > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> Right — so the hanging transaction > >> > only > >> > > > >> occurs > >> > > > >> > >> when > >> > > > >> > >> > we > >> > > > >> > >> > > > > have > >> > > > >> > >> > > > > > a > >> > > > >> > >> > > > > > > > late > >> > > > >> > >> > > > > > > > > >>>>>>> message > >> > > > >> > >> > > > > > > > > >>>>>>>> come in and the partition is never > >> > added > >> > > > to > >> > > > >> a > >> > > > >> > >> > > > transaction > >> > > > >> > >> > > > > > > again. > >> > > > >> > >> > > > > > > > > If > >> > > > >> > >> > > > > > > > > >>>>> we > >> > > > >> > >> > > > > > > > > >>>>>>>> never add the partition to a > >> > > transaction, > >> > > > we > >> > > > >> > will > >> > > > >> > >> > > never > >> > > > >> > >> > > > > > write > >> > > > >> > >> > > > > > > a > >> > > > >> > >> > > > > > > > > >>>>> marker > >> > > > >> > >> > > > > > > > > >>>>>>> and > >> > > > >> > >> > > > > > > > > >>>>>>>> never advance the LSO. > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> If we do end up adding the > >> partition > >> > to > >> > > > the > >> > > > >> > >> > > transaction > >> > > > >> > >> > > > (I > >> > > > >> > >> > > > > > > > suppose > >> > > > >> > >> > > > > > > > > >>>>> this > >> > > > >> > >> > > > > > > > > >>>>>>> can > >> > > > >> > >> > > > > > > > > >>>>>>>> happen before or after the late > >> > message > >> > > > >> comes > >> > > > >> > in) > >> > > > >> > >> > then > >> > > > >> > >> > > > we > >> > > > >> > >> > > > > > will > >> > > > >> > >> > > > > > > > > >>>>> include > >> > > > >> > >> > > > > > > > > >>>>>>> the > >> > > > >> > >> > > > > > > > > >>>>>>>> late message in the next > >> (incorrect) > >> > > > >> > transaction. > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> So perhaps it is clearer to make > >> the > >> > > > >> > distinction > >> > > > >> > >> > > between > >> > > > >> > >> > > > > > > > messages > >> > > > >> > >> > > > > > > > > >>>>> that > >> > > > >> > >> > > > > > > > > >>>>>>>> eventually get added to the > >> > transaction > >> > > > (but > >> > > > >> > the > >> > > > >> > >> > wrong > >> > > > >> > >> > > > > one) > >> > > > >> > >> > > > > > or > >> > > > >> > >> > > > > > > > > >>>>> messages > >> > > > >> > >> > > > > > > > > >>>>>>>> that never get added and become > >> > hanging. > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> 20) > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> The client side change for 2 is > >> > removing > >> > > > the > >> > > > >> > >> > > > addPartitions > >> > > > >> > >> > > > > > to > >> > > > >> > >> > > > > > > > > >>>>>> transaction > >> > > > >> > >> > > > > > > > > >>>>>>>> call. We don't need to make this > >> from > >> > > the > >> > > > >> > >> producer > >> > > > >> > >> > to > >> > > > >> > >> > > > the > >> > > > >> > >> > > > > > txn > >> > > > >> > >> > > > > > > > > >>>>>>> coordinator, > >> > > > >> > >> > > > > > > > > >>>>>>>> only server side. > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> In my opinion, the issue with the > >> > > > >> > >> addPartitionsToTxn > >> > > > >> > >> > > > call > >> > > > >> > >> > > > > > for > >> > > > >> > >> > > > > > > > > older > >> > > > >> > >> > > > > > > > > >>>>>>> clients > >> > > > >> > >> > > > > > > > > >>>>>>>> is that we don't have the epoch > >> bump, > >> > so > >> > > > we > >> > > > >> > don't > >> > > > >> > >> > know > >> > > > >> > >> > > > if > >> > > > >> > >> > > > > > the > >> > > > >> > >> > > > > > > > > >>> message > >> > > > >> > >> > > > > > > > > >>>>>>>> belongs to the previous > >> transaction or > >> > > > this > >> > > > >> > one. > >> > > > >> > >> We > >> > > > >> > >> > > need > >> > > > >> > >> > > > > to > >> > > > >> > >> > > > > > > > check > >> > > > >> > >> > > > > > > > > if > >> > > > >> > >> > > > > > > > > >>>>>> the > >> > > > >> > >> > > > > > > > > >>>>>>>> partition has been added to this > >> > > > >> transaction. > >> > > > >> > Of > >> > > > >> > >> > > course, > >> > > > >> > >> > > > > > this > >> > > > >> > >> > > > > > > > > means > >> > > > >> > >> > > > > > > > > >>>>> we > >> > > > >> > >> > > > > > > > > >>>>>>>> won't completely cover the case > >> where > >> > we > >> > > > >> have a > >> > > > >> > >> > really > >> > > > >> > >> > > > > late > >> > > > >> > >> > > > > > > > > message > >> > > > >> > >> > > > > > > > > >>>>> and > >> > > > >> > >> > > > > > > > > >>>>>>> we > >> > > > >> > >> > > > > > > > > >>>>>>>> have added the partition to the new > >> > > > >> > transaction, > >> > > > >> > >> but > >> > > > >> > >> > > > > that's > >> > > > >> > >> > > > > > > > > >>>>>> unfortunately > >> > > > >> > >> > > > > > > > > >>>>>>>> something we will need the new > >> clients > >> > > to > >> > > > >> > cover. > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> 30) > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> Transaction is ongoing = partition > >> was > >> > > > >> added to > >> > > > >> > >> > > > > transaction > >> > > > >> > >> > > > > > > via > >> > > > >> > >> > > > > > > > > >>>>>>>> addPartitionsToTxn. We check this > >> with > >> > > the > >> > > > >> > >> > > > > > > DescribeTransactions > >> > > > >> > >> > > > > > > > > >>> call. > >> > > > >> > >> > > > > > > > > >>>>>> Let > >> > > > >> > >> > > > > > > > > >>>>>>>> me know if this wasn't sufficiently > >> > > > >> explained > >> > > > >> > >> here: > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>> > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > > >> > > > >> > >> > > > > > > > > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > >> > > > >> > >> > > > > > >> > > > >> > >> > > > > >> > > > >> > >> > > > >> > > > >> > >> > > >> > > > >> > >> > >> > > > >> > > >> > > > >> > >> > > > > >> > > > >> > > >> https://cwiki.apache.org/confluence/display/KAFKA/KIP-890%3A+Transactions+Server-Side+Defense#KIP890:TransactionsServerSideDefense-EnsureOngoingTransactionforOlderClients(3) > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> 40) > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> The idea here is that if any > >> messages > >> > > > >> somehow > >> > > > >> > >> come > >> > > > >> > >> > in > >> > > > >> > >> > > > > before > >> > > > >> > >> > > > > > > we > >> > > > >> > >> > > > > > > > > get > >> > > > >> > >> > > > > > > > > >>>>> the > >> > > > >> > >> > > > > > > > > >>>>>>> new > >> > > > >> > >> > > > > > > > > >>>>>>>> epoch to the producer, they will be > >> > > > fenced. > >> > > > >> > >> However, > >> > > > >> > >> > > if > >> > > > >> > >> > > > we > >> > > > >> > >> > > > > > > don't > >> > > > >> > >> > > > > > > > > >>>>> think > >> > > > >> > >> > > > > > > > > >>>>>>> this > >> > > > >> > >> > > > > > > > > >>>>>>>> is necessary, it can be discussed > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> 50) > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> It should be synchronous because > >> if we > >> > > > have > >> > > > >> an > >> > > > >> > >> event > >> > > > >> > >> > > > (ie, > >> > > > >> > >> > > > > an > >> > > > >> > >> > > > > > > > > error) > >> > > > >> > >> > > > > > > > > >>>>>> that > >> > > > >> > >> > > > > > > > > >>>>>>>> causes us to need to abort the > >> > > > transaction, > >> > > > >> we > >> > > > >> > >> need > >> > > > >> > >> > to > >> > > > >> > >> > > > > know > >> > > > >> > >> > > > > > > > which > >> > > > >> > >> > > > > > > > > >>>>>>>> partitions to send transaction > >> markers > >> > > to. > >> > > > >> We > >> > > > >> > >> know > >> > > > >> > >> > the > >> > > > >> > >> > > > > > > > partitions > >> > > > >> > >> > > > > > > > > >>>>>> because > >> > > > >> > >> > > > > > > > > >>>>>>>> we added them to the coordinator > >> via > >> > the > >> > > > >> > >> > > > > addPartitionsToTxn > >> > > > >> > >> > > > > > > > call. > >> > > > >> > >> > > > > > > > > >>>>>>>> Previously we have had asynchronous > >> > > calls > >> > > > in > >> > > > >> > the > >> > > > >> > >> > past > >> > > > >> > >> > > > (ie, > >> > > > >> > >> > > > > > > > writing > >> > > > >> > >> > > > > > > > > >>>>> the > >> > > > >> > >> > > > > > > > > >>>>>>>> commit markers when the > >> transaction is > >> > > > >> > completed) > >> > > > >> > >> > but > >> > > > >> > >> > > > > often > >> > > > >> > >> > > > > > > this > >> > > > >> > >> > > > > > > > > >>> just > >> > > > >> > >> > > > > > > > > >>>>>>>> causes confusion as we need to wait > >> > for > >> > > > some > >> > > > >> > >> > > operations > >> > > > >> > >> > > > to > >> > > > >> > >> > > > > > > > > complete. > >> > > > >> > >> > > > > > > > > >>>>> In > >> > > > >> > >> > > > > > > > > >>>>>>> the > >> > > > >> > >> > > > > > > > > >>>>>>>> writing commit markers case, > >> clients > >> > > often > >> > > > >> see > >> > > > >> > >> > > > > > > > > >>>>> CONCURRENT_TRANSACTIONs > >> > > > >> > >> > > > > > > > > >>>>>>>> error messages and that can be > >> > > confusing. > >> > > > >> For > >> > > > >> > >> that > >> > > > >> > >> > > > reason, > >> > > > >> > >> > > > > > it > >> > > > >> > >> > > > > > > > may > >> > > > >> > >> > > > > > > > > be > >> > > > >> > >> > > > > > > > > >>>>>>>> simpler to just have synchronous > >> > calls — > >> > > > >> > >> especially > >> > > > >> > >> > if > >> > > > >> > >> > > > we > >> > > > >> > >> > > > > > need > >> > > > >> > >> > > > > > > > to > >> > > > >> > >> > > > > > > > > >>>>> block > >> > > > >> > >> > > > > > > > > >>>>>>> on > >> > > > >> > >> > > > > > > > > >>>>>>>> some operation's completion anyway > >> > > before > >> > > > we > >> > > > >> > can > >> > > > >> > >> > start > >> > > > >> > >> > > > the > >> > > > >> > >> > > > > > > next > >> > > > >> > >> > > > > > > > > >>>>>>>> transaction. And yes, I meant > >> > > > coordinator. I > >> > > > >> > will > >> > > > >> > >> > fix > >> > > > >> > >> > > > > that. > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> 60) > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> When we are checking if the > >> > transaction > >> > > is > >> > > > >> > >> ongoing, > >> > > > >> > >> > we > >> > > > >> > >> > > > > need > >> > > > >> > >> > > > > > to > >> > > > >> > >> > > > > > > > > make > >> > > > >> > >> > > > > > > > > >>> a > >> > > > >> > >> > > > > > > > > >>>>>>> round > >> > > > >> > >> > > > > > > > > >>>>>>>> trip from the leader partition to > >> the > >> > > > >> > transaction > >> > > > >> > >> > > > > > coordinator. > >> > > > >> > >> > > > > > > > In > >> > > > >> > >> > > > > > > > > >>> the > >> > > > >> > >> > > > > > > > > >>>>>>> time > >> > > > >> > >> > > > > > > > > >>>>>>>> we are waiting for this message to > >> > come > >> > > > >> back, > >> > > > >> > in > >> > > > >> > >> > > theory > >> > > > >> > >> > > > we > >> > > > >> > >> > > > > > > could > >> > > > >> > >> > > > > > > > > >>> have > >> > > > >> > >> > > > > > > > > >>>>>>> sent > >> > > > >> > >> > > > > > > > > >>>>>>>> a commit/abort call that would make > >> > the > >> > > > >> > original > >> > > > >> > >> > > result > >> > > > >> > >> > > > of > >> > > > >> > >> > > > > > the > >> > > > >> > >> > > > > > > > > check > >> > > > >> > >> > > > > > > > > >>>>>> out > >> > > > >> > >> > > > > > > > > >>>>>>> of > >> > > > >> > >> > > > > > > > > >>>>>>>> date. That is why we can check the > >> > > leader > >> > > > >> state > >> > > > >> > >> > before > >> > > > >> > >> > > > we > >> > > > >> > >> > > > > > > write > >> > > > >> > >> > > > > > > > to > >> > > > >> > >> > > > > > > > > >>>>> the > >> > > > >> > >> > > > > > > > > >>>>>>> log. > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> I'm happy to update the KIP if > >> some of > >> > > > these > >> > > > >> > >> things > >> > > > >> > >> > > were > >> > > > >> > >> > > > > not > >> > > > >> > >> > > > > > > > > clear. > >> > > > >> > >> > > > > > > > > >>>>>>>> Thanks, > >> > > > >> > >> > > > > > > > > >>>>>>>> Justine > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> On Mon, Nov 21, 2022 at 7:11 PM > >> > Matthias > >> > > > J. > >> > > > >> > Sax < > >> > > > >> > >> > > > > > > > mj...@apache.org > >> > > > >> > >> > > > > > > > > > > >> > > > >> > >> > > > > > > > > >>>>>>> wrote: > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> Thanks for the KIP. > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> Couple of clarification questions > >> (I > >> > am > >> > > > >> not a > >> > > > >> > >> > broker > >> > > > >> > >> > > > > expert > >> > > > >> > >> > > > > > > do > >> > > > >> > >> > > > > > > > > >>>>> maybe > >> > > > >> > >> > > > > > > > > >>>>>>>>> some question are obvious for > >> others, > >> > > but > >> > > > >> not > >> > > > >> > >> for > >> > > > >> > >> > me > >> > > > >> > >> > > > with > >> > > > >> > >> > > > > > my > >> > > > >> > >> > > > > > > > lack > >> > > > >> > >> > > > > > > > > >>>>> of > >> > > > >> > >> > > > > > > > > >>>>>>>>> broker knowledge). > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> (10) > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>>> 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. > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> What happens if the message come > >> in > >> > > > before > >> > > > >> the > >> > > > >> > >> next > >> > > > >> > >> > > > > > > > > >>>>>> addPartitionsToTxn > >> > > > >> > >> > > > > > > > > >>>>>>>>> request? It seems the broker > >> hosting > >> > > the > >> > > > >> data > >> > > > >> > >> > > > partitions > >> > > > >> > >> > > > > > > won't > >> > > > >> > >> > > > > > > > > know > >> > > > >> > >> > > > > > > > > >>>>>>>>> anything about it and append it to > >> > the > >> > > > >> > >> partition, > >> > > > >> > >> > > too? > >> > > > >> > >> > > > > What > >> > > > >> > >> > > > > > > is > >> > > > >> > >> > > > > > > > > the > >> > > > >> > >> > > > > > > > > >>>>>>>>> difference between both cases? > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> Also, it seems a TX would only > >> hang, > >> > if > >> > > > >> there > >> > > > >> > >> is no > >> > > > >> > >> > > > > > following > >> > > > >> > >> > > > > > > > TX > >> > > > >> > >> > > > > > > > > >>>>> that > >> > > > >> > >> > > > > > > > > >>>>>>> is > >> > > > >> > >> > > > > > > > > >>>>>>>>> either committer or aborted? Thus, > >> > for > >> > > > the > >> > > > >> > case > >> > > > >> > >> > > above, > >> > > > >> > >> > > > > the > >> > > > >> > >> > > > > > TX > >> > > > >> > >> > > > > > > > > might > >> > > > >> > >> > > > > > > > > >>>>>>>>> actually not hang (of course, we > >> > might > >> > > > get > >> > > > >> an > >> > > > >> > >> EOS > >> > > > >> > >> > > > > violation > >> > > > >> > >> > > > > > > if > >> > > > >> > >> > > > > > > > > the > >> > > > >> > >> > > > > > > > > >>>>>>> first > >> > > > >> > >> > > > > > > > > >>>>>>>>> TX was aborted and the second > >> > > committed, > >> > > > or > >> > > > >> > the > >> > > > >> > >> > other > >> > > > >> > >> > > > way > >> > > > >> > >> > > > > > > > > around). > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> (20) > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>>> Of course, 1 and 2 require > >> > client-side > >> > > > >> > >> changes, so > >> > > > >> > >> > > for > >> > > > >> > >> > > > > > older > >> > > > >> > >> > > > > > > > > >>>>>> clients, > >> > > > >> > >> > > > > > > > > >>>>>>>>> those approaches won’t apply. > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> For (1) I understand why a client > >> > > change > >> > > > is > >> > > > >> > >> > > necessary, > >> > > > >> > >> > > > > but > >> > > > >> > >> > > > > > > not > >> > > > >> > >> > > > > > > > > sure > >> > > > >> > >> > > > > > > > > >>>>>> why > >> > > > >> > >> > > > > > > > > >>>>>>>>> we need a client change for (2). > >> Can > >> > > you > >> > > > >> > >> elaborate? > >> > > > >> > >> > > -- > >> > > > >> > >> > > > > > Later > >> > > > >> > >> > > > > > > > you > >> > > > >> > >> > > > > > > > > >>>>>>> explain > >> > > > >> > >> > > > > > > > > >>>>>>>>> that we should send a > >> > > > >> > >> DescribeTransactionRequest, > >> > > > >> > >> > > but I > >> > > > >> > >> > > > > am > >> > > > >> > >> > > > > > > not > >> > > > >> > >> > > > > > > > > sure > >> > > > >> > >> > > > > > > > > >>>>>>> why? > >> > > > >> > >> > > > > > > > > >>>>>>>>> Can't we not just do an implicit > >> > > > >> > >> AddPartiitonToTx, > >> > > > >> > >> > > too? > >> > > > >> > >> > > > > If > >> > > > >> > >> > > > > > > the > >> > > > >> > >> > > > > > > > > old > >> > > > >> > >> > > > > > > > > >>>>>>>>> producer correctly registered the > >> > > > partition > >> > > > >> > >> > already, > >> > > > >> > >> > > > the > >> > > > >> > >> > > > > > > > > >>>>>> TX-coordinator > >> > > > >> > >> > > > > > > > > >>>>>>>>> can just ignore it as it's an > >> > > idempotent > >> > > > >> > >> operation? > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> (30) > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>>> To cover older clients, we will > >> > > ensure a > >> > > > >> > >> > transaction > >> > > > >> > >> > > > is > >> > > > >> > >> > > > > > > > ongoing > >> > > > >> > >> > > > > > > > > >>>>>>> before > >> > > > >> > >> > > > > > > > > >>>>>>>>> we write to a transaction > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> Not sure what you mean by this? > >> Can > >> > you > >> > > > >> > >> elaborate? > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> (40) > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>>> [the TX-coordinator] will write > >> the > >> > > > >> prepare > >> > > > >> > >> commit > >> > > > >> > >> > > > > message > >> > > > >> > >> > > > > > > > with > >> > > > >> > >> > > > > > > > > a > >> > > > >> > >> > > > > > > > > >>>>>>>> bumped > >> > > > >> > >> > > > > > > > > >>>>>>>>> epoch and send > >> WriteTxnMarkerRequests > >> > > > with > >> > > > >> the > >> > > > >> > >> > bumped > >> > > > >> > >> > > > > > epoch. > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> Why do we use the bumped epoch for > >> > > both? > >> > > > It > >> > > > >> > >> seems > >> > > > >> > >> > > more > >> > > > >> > >> > > > > > > > intuitive > >> > > > >> > >> > > > > > > > > to > >> > > > >> > >> > > > > > > > > >>>>>> use > >> > > > >> > >> > > > > > > > > >>>>>>>>> the current epoch, and only return > >> > the > >> > > > >> bumped > >> > > > >> > >> epoch > >> > > > >> > >> > > to > >> > > > >> > >> > > > > the > >> > > > >> > >> > > > > > > > > >>>>> producer? > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> (50) "Implicit > >> > > AddPartitionToTransaction" > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> Why does the implicitly sent > >> request > >> > > need > >> > > > >> to > >> > > > >> > be > >> > > > >> > >> > > > > > synchronous? > >> > > > >> > >> > > > > > > > The > >> > > > >> > >> > > > > > > > > >>>>> KIP > >> > > > >> > >> > > > > > > > > >>>>>>>>> also says > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>>> in case we need to abort and > >> need to > >> > > > know > >> > > > >> > which > >> > > > >> > >> > > > > partitions > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> What do you mean by this? > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>>> we don’t want to write to it > >> before > >> > we > >> > > > >> store > >> > > > >> > in > >> > > > >> > >> > the > >> > > > >> > >> > > > > > > > transaction > >> > > > >> > >> > > > > > > > > >>>>>>> manager > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> Do you mean TX-coordinator > >> instead of > >> > > > >> > "manager"? > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> (60) > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> For older clients and ensuring > >> that > >> > the > >> > > > TX > >> > > > >> is > >> > > > >> > >> > > ongoing, > >> > > > >> > >> > > > > you > >> > > > >> > >> > > > > > > > > >>>>> describe a > >> > > > >> > >> > > > > > > > > >>>>>>>>> race condition. I am not sure if I > >> > can > >> > > > >> follow > >> > > > >> > >> here. > >> > > > >> > >> > > Can > >> > > > >> > >> > > > > you > >> > > > >> > >> > > > > > > > > >>>>>> elaborate? > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> -Matthias > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> On 11/18/22 1:21 PM, Justine > >> Olshan > >> > > > wrote: > >> > > > >> > >> > > > > > > > > >>>>>>>>>> Hey all! > >> > > > >> > >> > > > > > > > > >>>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>>> I'd like to start a discussion > >> on my > >> > > > >> proposal > >> > > > >> > >> to > >> > > > >> > >> > add > >> > > > >> > >> > > > > some > >> > > > >> > >> > > > > > > > > >>>>>> server-side > >> > > > >> > >> > > > > > > > > >>>>>>>>>> checks on transactions to avoid > >> > > hanging > >> > > > >> > >> > > transactions. > >> > > > >> > >> > > > I > >> > > > >> > >> > > > > > know > >> > > > >> > >> > > > > > > > > this > >> > > > >> > >> > > > > > > > > >>>>>> has > >> > > > >> > >> > > > > > > > > >>>>>>>>> been > >> > > > >> > >> > > > > > > > > >>>>>>>>>> an issue for some time, so I > >> really > >> > > hope > >> > > > >> this > >> > > > >> > >> KIP > >> > > > >> > >> > > will > >> > > > >> > >> > > > > be > >> > > > >> > >> > > > > > > > > helpful > >> > > > >> > >> > > > > > > > > >>>>>> for > >> > > > >> > >> > > > > > > > > >>>>>>>>> many > >> > > > >> > >> > > > > > > > > >>>>>>>>>> users of EOS. > >> > > > >> > >> > > > > > > > > >>>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>>> The KIP includes changes that > >> will > >> > be > >> > > > >> > >> compatible > >> > > > >> > >> > > with > >> > > > >> > >> > > > > old > >> > > > >> > >> > > > > > > > > clients > >> > > > >> > >> > > > > > > > > >>>>>> and > >> > > > >> > >> > > > > > > > > >>>>>>>>>> changes to improve performance > >> and > >> > > > >> > correctness > >> > > > >> > >> on > >> > > > >> > >> > > new > >> > > > >> > >> > > > > > > clients. > >> > > > >> > >> > > > > > > > > >>>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>>> Please take a look and leave any > >> > > > comments > >> > > > >> you > >> > > > >> > >> may > >> > > > >> > >> > > > have! > >> > > > >> > >> > > > > > > > > >>>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>>> KIP: > >> > > > >> > >> > > > > > > > > >>>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>> > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > > >> > > > >> > >> > > > > > > > > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > >> > > > >> > >> > > > > > >> > > > >> > >> > > > > >> > > > >> > >> > > > >> > > > >> > >> > > >> > > > >> > >> > >> > > > >> > > >> > > > >> > >> > > > > >> > > > >> > > >> https://cwiki.apache.org/confluence/display/KAFKA/KIP-890%3A+Transactions+Server-Side+Defense > >> > > > >> > >> > > > > > > > > >>>>>>>>>> JIRA: > >> > > > >> > >> > > > https://issues.apache.org/jira/browse/KAFKA-14402 > >> > > > >> > >> > > > > > > > > >>>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>>> Thanks! > >> > > > >> > >> > > > > > > > > >>>>>>>>>> Justine > >> > > > >> > >> > > > > > > > > >>>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>>> > >> > > > >> > >> > > > > > > > > >>>>>> > >> > > > >> > >> > > > > > > > > >>>>> > >> > > > >> > >> > > > > > > > > >>>> > >> > > > >> > >> > > > > > > > > >>> > >> > > > >> > >> > > > > > > > > >> > >> > > > >> > >> > > > > > > > > > > >> > > > >> > >> > > > > > > > > > >> > > > >> > >> > > > > > > > > >> > > > >> > >> > > > > > > > >> > > > >> > >> > > > > > > >> > > > >> > >> > > > > > >> > > > >> > >> > > > > >> > > > >> > >> > > > >> > > > >> > >> > > >> > > > >> > >> > >> > > > >> > > > >> > > > >> > > >> > > > >> > >> > > > > > >> > > > > >> > > > >> > > >> > >
