Hi Nitty, > I called commitTransaction when I reach the first error record, but commit is not happening for me. Kafka connect tries to abort the transaction automatically
This is really interesting--are you certain that your task never invoked TransactionContext::abortTransaction in this case? I'm looking over the code base and it seems fairly clear that the only thing that could trigger a call to KafkaProducer::abortTransaction is a request by the task to abort a transaction (either for a next batch, or for a specific record). It may help to run the connector in a debugger and/or look for "Aborting transaction for batch as requested by connector" or "Aborting transaction for record on topic <TOPIC NAME HERE> as requested by connector" log messages (which will be emitted at INFO level by the org.apache.kafka.connect.runtime.ExactlyOnceWorkerSourceTask class if the task is requesting an abort). Regardless, I'll work on a fix for the bug with aborting empty transactions. Thanks for helping uncover that one! Cheers, Chris On Thu, Mar 9, 2023 at 6:36 PM NITTY BENNY <nittybe...@gmail.com> wrote: > Hi Chris, > > We have a use case to commit previous successful records and stop the > processing of the current file and move on with the next file. To achieve > that I called commitTransaction when I reach the first error record, but > commit is not happening for me. Kafka connect tries to abort the > transaction automatically, I checked the _transaction_state topic and > states marked as PrepareAbort and CompleteAbort. Do you know why kafka > connect automatically invokes abort instead of the implicit commit I > called? > Then as a result, when I tries to parse the next file - say ABC, I saw the > logs "Aborting incomplete transaction" and ERROR: "Failed to sent record to > topic", and we lost the first batch of records from the current transaction > in the file ABC. > > Is it possible that there's a case where an abort is being requested while > the current transaction is empty (i.e., the task hasn't returned any > records from SourceTask::poll since the last transaction was > committed/aborted)? --- Yes, that case is possible for us. There is a case > where the first record itself an error record. > > Thanks, > Nitty > > On Thu, Mar 9, 2023 at 3:48 PM Chris Egerton <chr...@aiven.io.invalid> > wrote: > > > Hi Nitty, > > > > Thanks for the code examples and the detailed explanations, this is > really > > helpful! > > > > > Say if I have a file with 5 records and batch size is 2, and in my 3rd > > batch I have one error record then in that batch, I dont have a valid > > record to call commit or abort. But I want to commit all the previous > > batches that were successfully parsed. How do I do that? > > > > An important thing to keep in mind with the TransactionContext API is > that > > all records that a task returns from SourceTask::poll are implicitly > > included in a transaction. Invoking SourceTaskContext::transactionContext > > doesn't alter this or cause transactions to start being used; everything > is > > already in a transaction, and the Connect runtime automatically begins > > transactions for any records it sees from the task if it hasn't already > > begun one. It's also valid to return a null or empty list of records from > > SourceTask::poll. So in this case, you can invoke > > transactionContext.commitTransaction() (the no-args variant) and return > an > > empty batch from SourceTask::poll, which will cause the transaction > > containing the 4 valid records that were returned in the last 2 batches > to > > be committed. > > > > FWIW, I would be a little cautious about this approach. Many times it's > > better to fail fast on invalid data; it might be worth it to at least > allow > > users to configure whether the connector fails on invalid data, or > silently > > skips over it (which is what happens when transactions are aborted). > > > > > Why is abort not working without adding the last record to the list? > > > > Is it possible that there's a case where an abort is being requested > while > > the current transaction is empty (i.e., the task hasn't returned any > > records from SourceTask::poll since the last transaction was > > committed/aborted)? I think this may be a bug in the Connect framework > > where we don't check to see if a transaction is already open when a task > > requests that a transaction be aborted, which can cause tasks to fail > (see > > https://issues.apache.org/jira/browse/KAFKA-14799 for more details). > > > > Cheers, > > > > Chris > > > > > > On Wed, Mar 8, 2023 at 6:44 PM NITTY BENNY <nittybe...@gmail.com> wrote: > > > > > Hi Chris, > > > > > > I am not sure if you are able to see the images I shared with you . > > > Copying the code snippet below, > > > > > > if (expectedRecordCount >= 0) { > > > int missingCount = expectedRecordCount - (int) this. > > > recordOffset() - 1; > > > if (missingCount > 0) { > > > if (transactionContext != null) { > > > isMissedRecords = true; > > > } else { > > > throw new DataException(String.format("Missing %d > records > > > (expecting %d, actual %d)", missingCount, expectedRecordCount, this. > > > recordOffset())); > > > } > > > } else if (missingCount < 0) { > > > if (transactionContext != null) { > > > isMissedRecords = true; > > > } else { > > > throw new DataException(String.format("Too many records > > > (expecting %d, actual %d)", expectedRecordCount, this.recordOffset())); > > > } > > > } > > > } > > > addLastRecord(records, null, value); > > > } > > > > > > > > > > > > //asn1 or binary abort > > > if((config.parseErrorThreshold != null && parseErrorCount >= > > > config.parseErrorThreshold > > > && lastbatch && transactionContext != null) || (isMissedRecords > > > && transactionContext != null && lastbatch)) { > > > log.info("Transaction is aborting"); > > > log.info("records = {}", records); > > > if (!records.isEmpty()) { > > > log.info("with record"); > > > > > transactionContext.abortTransaction(records.get(records.size > > > ()-1)); > > > } else { > > > log.info("without record"); > > > transactionContext.abortTransaction(); > > > } > > > > > > Thanks, > > > Nitty > > > > > > On Wed, Mar 8, 2023 at 11:38 PM NITTY BENNY <nittybe...@gmail.com> > > wrote: > > > > > >> Hi Chris, > > >> Sorry for the typo in my previous email. > > >> > > >> Regarding the point 2,* the task returns a batch of records from > > >> SourceTask::poll (and, if using* > > >> > > >> > > >> *the per-record API provided by the TransactionContext class, includes > > >> atleast one record that should trigger a transaction commit/abort in > > >> thatbatch)* > > >> What if I am using the API without passing a record? We have 2 types > of > > >> use cases, one where on encountering an error record, we want to > commit > > >> previous successful batches and disregard the failed record and > upcoming > > >> batches. In this case we created the transactionContext just before > > reading > > >> the file (file is our transaction boundary).Say if I have a file with > 5 > > >> records and batch size is 2, and in my 3rd batch I have one error > record > > >> then in that batch, I dont have a valid record to call commit or > abort. > > But > > >> I want to commit all the previous batches that were successfully > parsed. > > >> How do I do that? > > >> > > >> Second use case is where I want to abort a transaction if the record > > >> count doesn't match. > > >> Code Snippet : > > >> [image: image.png] > > >> There are no error records in this case. If you see I added the > > condition > > >> of transactionContext check to implement exactly once, without > > >> transaction it was just throwing the exception without calling the > > >> addLastRecord() method and in the catch block it just logs the message > > and > > >> return the list of records without the last record to poll().To make > it > > >> work, I called the method addLastRecord() in this case, so it is not > > >> throwing the exception and list has last record as well. Then I called > > the > > >> abort, everything got aborted. Why is abort not working without adding > > the > > >> last record to the list? > > >> [image: image.png] > > >> > > >> Code to call abort. > > >> > > >> > > >> > > >> > > >> Thanks, > > >> Nitty > > >> > > >> On Wed, Mar 8, 2023 at 4:26 PM Chris Egerton <chr...@aiven.io.invalid > > > > >> wrote: > > >> > > >>> Hi Nitty, > > >>> > > >>> I'm a little confused about what you mean by this part: > > >>> > > >>> > transaction is not getting completed because it is not commiting > the > > >>> transaction offest. > > >>> > > >>> The only conditions required for a transaction to be completed when a > > >>> connector is defining its own transaction boundaries are: > > >>> > > >>> 1. The task requests a transaction commit/abort from the > > >>> TransactionContext > > >>> 2. The task returns a batch of records from SourceTask::poll (and, if > > >>> using > > >>> the per-record API provided by the TransactionContext class, includes > > at > > >>> least one record that should trigger a transaction commit/abort in > that > > >>> batch) > > >>> > > >>> The Connect runtime should automatically commit source offsets to > Kafka > > >>> whenever a transaction is completed, either by commit or abort. This > is > > >>> because transactions should only be aborted for data that should > never > > be > > >>> re-read by the connector; if there is a validation error that should > be > > >>> handled by reconfiguring the connector, then the task should throw an > > >>> exception instead of aborting the transaction. > > >>> > > >>> If possible, do you think you could provide a brief code snippet > > >>> illustrating what your task is doing that's causing issues? > > >>> > > >>> Cheers, > > >>> > > >>> Chris (not Chrise 🙂) > > >>> > > >>> On Tue, Mar 7, 2023 at 10:17 AM NITTY BENNY <nittybe...@gmail.com> > > >>> wrote: > > >>> > > >>> > Hi Chrise, > > >>> > > > >>> > Thanks for sharing the details. > > >>> > > > >>> > Regarding the use case, For Asn1 source connector we have a use > case > > to > > >>> > validate number of records in the file with the number of records > in > > >>> the > > >>> > header. So currently, if validation fails we are not sending the > last > > >>> > record to the topic. But after introducing exactly once with > > connector > > >>> > transaction boundary, I can see that if I call an abort when the > > >>> validation > > >>> > fails, transaction is not getting completed because it is not > > >>> commiting the > > >>> > transaction offest. I saw that transaction state changed to > > >>> CompleteAbort. > > >>> > So for my next transaction I am getting > InvalidProducerEpochException > > >>> and > > >>> > then task stopped after that. I tried calling the abort after > sending > > >>> last > > >>> > record to the topic then transaction getting completed. > > >>> > > > >>> > I dont know if I am doing anything wrong here. > > >>> > > > >>> > Please advise. > > >>> > Thanks, > > >>> > Nitty > > >>> > > > >>> > On Tue 7 Mar 2023 at 2:21 p.m., Chris Egerton > > <chr...@aiven.io.invalid > > >>> > > > >>> > wrote: > > >>> > > > >>> > > Hi Nitty, > > >>> > > > > >>> > > We've recently added some documentation on implementing > > exactly-once > > >>> > source > > >>> > > connectors here: > > >>> > > > > >>> > > > >>> > > > https://kafka.apache.org/documentation/#connect_exactlyoncesourceconnectors > > >>> > > . > > >>> > > To quote a relevant passage from those docs: > > >>> > > > > >>> > > > In order for a source connector to take advantage of this > > support, > > >>> it > > >>> > > must be able to provide meaningful source offsets for each record > > >>> that it > > >>> > > emits, and resume consumption from the external system at the > exact > > >>> > > position corresponding to any of those offsets without dropping > or > > >>> > > duplicating messages. > > >>> > > > > >>> > > So, as long as your source connector is able to use the Kafka > > Connect > > >>> > > framework's offsets API correctly, it shouldn't be necessary to > > make > > >>> any > > >>> > > other code changes to the connector. > > >>> > > > > >>> > > To enable exactly-once support for source connectors on your > > Connect > > >>> > > cluster, see the docs section here: > > >>> > > > https://kafka.apache.org/documentation/#connect_exactlyoncesource > > >>> > > > > >>> > > With regard to transactions, a transactional producer is always > > >>> created > > >>> > > automatically for your connector by the Connect runtime when > > >>> exactly-once > > >>> > > support is enabled on the worker. The only reason to set > > >>> > > "transaction.boundary" to "connector" is if your connector would > > >>> like to > > >>> > > explicitly define its own transaction boundaries. In this case, > it > > >>> sounds > > >>> > > like may be what you want; I just want to make sure to call out > > that > > >>> in > > >>> > > either case, you should not be directly instantiating a producer > in > > >>> your > > >>> > > connector code, but let the Kafka Connect runtime do that for > you, > > >>> and > > >>> > just > > >>> > > worry about returning the right records from SourceTask::poll > (and > > >>> > possibly > > >>> > > defining custom transactions using the TransactionContext API). > > >>> > > > > >>> > > With respect to your question about committing or aborting in > > certain > > >>> > > circumstances, it'd be useful to know more about your use case, > > >>> since it > > >>> > > may not be necessary to define custom transaction boundaries in > > your > > >>> > > connector at all. > > >>> > > > > >>> > > Cheers, > > >>> > > > > >>> > > Chris > > >>> > > > > >>> > > > > >>> > > > > >>> > > On Tue, Mar 7, 2023 at 7:21 AM NITTY BENNY <nittybe...@gmail.com > > > > >>> wrote: > > >>> > > > > >>> > > > Hi Team, > > >>> > > > > > >>> > > > Adding on top of this, I tried creating a TransactionContext > > >>> object and > > >>> > > > calling the commitTransaction and abortTranaction methods in > > source > > >>> > > > connectors. > > >>> > > > But the main problem I saw is that if there is any error while > > >>> parsing > > >>> > > the > > >>> > > > record, connect is calling an abort but we have a use case to > > call > > >>> > commit > > >>> > > > in some cases. Is it a valid use case in terms of kafka > connect? > > >>> > > > > > >>> > > > Another Question - Should I use a transactional producer > instead > > >>> > > > creating an object of TransactionContext? Below is the > connector > > >>> > > > configuration I am using. > > >>> > > > > > >>> > > > exactly.once.support: "required" > > >>> > > > transaction.boundary: "connector" > > >>> > > > > > >>> > > > Could you please help me here? > > >>> > > > > > >>> > > > Thanks, > > >>> > > > Nitty > > >>> > > > > > >>> > > > On Tue, Mar 7, 2023 at 12:29 AM NITTY BENNY < > > nittybe...@gmail.com> > > >>> > > wrote: > > >>> > > > > > >>> > > > > Hi Team, > > >>> > > > > I am trying to implement exactly once behavior in our source > > >>> > connector. > > >>> > > > Is > > >>> > > > > there any sample source connector implementation available to > > >>> have a > > >>> > > look > > >>> > > > > at? > > >>> > > > > Regards, > > >>> > > > > Nitty > > >>> > > > > > > >>> > > > > > >>> > > > > >>> > > > >>> > > >> > > >
