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From Antoine Philippot <antoine.philip...@teads.tv>
Subject Re: Avoid duplicate messages while restarting a job for an application upgrade
Date Mon, 02 Oct 2017 15:30:53 GMT
Thanks Piotr for your answer, we sadly can't use kafka 0.11 for now (and
until a while).

We can not afford tens of thousands of duplicated messages for each
application upgrade, can I help by working on this feature ?
Do you have any hint or details on this part of that "todo list" ?


Le lun. 2 oct. 2017 à 16:50, Piotr Nowojski <piotr@data-artisans.com> a
écrit :

> Hi,
>
> For failures recovery with Kafka 0.9 it is not possible to avoid
> duplicated messages. Using Flink 1.4 (unreleased yet) combined with Kafka
> 0.11 it will be possible to achieve exactly-once end to end semantic when
> writing to Kafka. However this still a work in progress:
>
> https://issues.apache.org/jira/browse/FLINK-6988
>
> However this is a superset of functionality that you are asking for.
> Exactly-once just for clean shutdowns is also on our “TODO” list (it
> would/could support Kafka 0.9), but it is not currently being actively
> developed.
>
> Piotr Nowojski
>
> On Oct 2, 2017, at 3:35 PM, Antoine Philippot <antoine.philippot@teads.tv>
> wrote:
>
> Hi,
>
> I'm working on a flink streaming app with a kafka09 to kafka09 use case
> which handles around 100k messages per seconds.
>
> To upgrade our application we used to run a flink cancel with savepoint
> command followed by a flink run with the previous saved savepoint and the
> new application fat jar as parameter. We notice that we can have more than
> 50k of duplicated messages in the kafka sink wich is not idempotent.
>
> This behaviour is actually problematic for this project and I try to find
> a solution / workaround to avoid these duplicated messages.
>
> The JobManager indicates clearly that the cancel call is triggered once
> the savepoint is finished, but during the savepoint execution, kafka source
> continue to poll new messages which will not be part of the savepoint and
> will be replayed on the next application start.
>
> I try to find a solution with the stop command line argument but the kafka
> source doesn't implement StoppableFunction (
> https://issues.apache.org/jira/browse/FLINK-3404) and the savepoint
> generation is not available with stop in contrary to cancel.
>
> Is there an other solution to not process duplicated messages for each
> application upgrade or rescaling ?
>
> If no, has someone planned to implement it? Otherwise, I can propose a
> pull request after some architecture advices.
>
> The final goal is to stop polling source and trigger a savepoint once
> polling stopped.
>
> Thanks
>
>
>

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