Hi Tobi, No, FlinkKafkaConsumer is not using committed Kafka’s offsets for recovery. Offsets where to start from are stored in the checkpoint itself. Updating the offsets back to Kafka is an optional, purely cosmetic thing from the Flink’s perspective, so the job will start from the correct offsets.
However, if you for whatever the reason re-start the job from a savepoint/checkpoint that’s not the latest one, this will violate exactly-once guarantees - there will be some duplicated records committed two times in the sinks, as simply some records would be processed and committed twice. Committing happens on checkpoint, so if you are recovering to some previous checkpoint, there is nothing Flink can do - some records were already committed before. Piotrek > On 2 Mar 2020, at 10:12, Kaymak, Tobias <tobias.kay...@ricardo.ch> wrote: > > Thank you Piotr! > > One last question - let's assume my source is a Kafka topic - if I stop via > the CLI with a savepoint in Flink 1.9, but do not use that savepoint when > restarting my job - the job would continue from the last offset that has been > committed in Kafka and thus I would also not experience a loss of data in my > sink. Is that correct? > > Best, > Tobi > > On Fri, Feb 28, 2020 at 3:17 PM Piotr Nowojski <pi...@ververica.com > <mailto:pi...@ververica.com>> wrote: > Yes, that’s correct. There shouldn’t be any data loss. Stop with savepoint is > a solution to make sure, that if you are stopping a job (either permanently > or temporarily) that all of the results are published/committed to external > systems before you actually stop the job. > > If you just cancel/kill/crash a job, in some rare cases (if a checkpoint was > completing at the time cluster was crashing), some records might not be > committed before the cancellation/kill/crash happened. Also note that doesn’t > mean there is a data loss, just those records will be published once you > restore your job from a checkpoint. If you want to stop the job permanently, > that might not happen, hence we need stop with savepoint. > > Piotrek > >> On 28 Feb 2020, at 15:02, Kaymak, Tobias <tobias.kay...@ricardo.ch >> <mailto:tobias.kay...@ricardo.ch>> wrote: >> >> Thank you! For understanding the matter: When I have a streaming pipeline >> (reading from Kafka, writing somewhere) and I click "cancel" and after that >> I restart the pipeline - I should not expect any data to be lost - is that >> correct? >> >> Best, >> Tobias >> >> On Fri, Feb 28, 2020 at 2:51 PM Piotr Nowojski <pi...@ververica.com >> <mailto:pi...@ververica.com>> wrote: >> Thanks for confirming that Yadong. I’ve created a ticket for that [1]. >> >> Piotrek >> >> [1] https://issues.apache.org/jira/browse/FLINK-16340 >> <https://issues.apache.org/jira/browse/FLINK-16340> >> >>> On 28 Feb 2020, at 14:32, Yadong Xie <vthink...@gmail.com >>> <mailto:vthink...@gmail.com>> wrote: >>> >>> Hi >>> >>> 1. the old stop button was removed in flink 1.9.0 since it could not work >>> properly as I know >>> 2. if we have the feature of the stop with savepoint, we could add it to >>> the web UI, but it may still need some work on the rest API to support the >>> new feature >>> >>> >>> Best, >>> Yadong >>> >>> >>> Piotr Nowojski <pi...@ververica.com <mailto:pi...@ververica.com>> >>> 于2020年2月28日周五 下午8:49写道： >>> Hi, >>> >>> I’m not sure. Maybe Yadong (CC) will know more, but to the best of my >>> knowledge and research: >>> >>> 1. In Flink 1.9 we switched from the old webUI to a new one, that probably >>> explains the difference you are seeing. >>> 2. The “Stop” button in the old webUI, was not working properly - that was >>> not stop with savepoint, as stop with savepoint is a relatively new feature. >>> 3. Now that we have stop with savepoint (it can be used from CLI as you >>> wrote), probably we could expose this feature in the new UI as well, unless >>> it’s already exposed somewhere? Yadong, do you know an answer for that? >>> >>> Piotrek >>> >>>> On 27 Feb 2020, at 13:31, Kaymak, Tobias <tobias.kay...@ricardo.ch >>>> <mailto:tobias.kay...@ricardo.ch>> wrote: >>>> >>>> Hello, >>>> >>>> before Flink 1.9 I was able to "Stop" a streaming pipeline - after >>>> clicking that button in the webinterface it performed a clean shutdown. >>>> Now with Flink 1.9 I just see the option to cancel it. >>>> >>>> However, using the commandline flink stop -d >>>> 266c5b38cf9d8e61a398a0bef4a1b350 still does the trick. So the >>>> functionality is there. >>>> >>>> Has the button been removed on purpose? >>>> >>>> Best, >>>> Tobias >>> >> >> >> >> -- >> >> Tobias Kaymak >> Data Engineer >> Data Intelligence >> >> tobias.kay...@ricardo.ch <mailto:tobias.kay...@ricardo.ch> >> www.ricardo.ch <http://www.ricardo.ch/> >> Theilerstrasse 1a, 6300 Zug >> >
