Hi Piotrek, I come back to you with a Jira ticket that I created and a proposal the ticket : https://issues.apache.org/jira/browse/FLINK-7883 the proposal : https://github.com/aphilippot/flink/commit/9c58c95bb4b68ea337f7c583b7e039d86f3142a6
I'am open to any comments or suggestions Antoine Le mar. 10 oct. 2017 à 09:28, Piotr Nowojski <pi...@data-artisans.com> a écrit : > Hi, > > That’s good to hear :) > > I quickly went through the code and it seems reasonable. I think there > might be need to think a little bit more about how this cancel checkpoint > should be exposed to the operators and what should be default action - > right now by default cancel flag is ignored, I would like to consider if > throwing an UnsupportedOperation would be a better long therm solution. > > But at first glance I do not see any larger issues and it would great if > you could make a pull request out of it. > > Piotrek > > On 9 Oct 2017, at 15:56, Antoine Philippot <antoine.philip...@teads.tv> > wrote: > > Thanks for your advices Piotr. > > Firstly, yes, we are aware that even with clean shutdown we can end up > with duplicated messages after a crash and it is acceptable as is it rare > and unintentional unlike deploying new business code or up/down scale. > > I made a fork of the 1.2.1 version which we currently use and developed a > simple POC based on the solution to pass a boolean stopSourceSavepoint from > the job manager to the source when a cancel with savepoint is triggered. > This is the altered code : > https://github.com/aphilippot/flink/compare/release-1.2.1...aphilippot:flink_1_2_1_POC_savepoint > > We test it with our production workload and there are no duplicated > messages any more while hundred of thousands were duplicated before. > > I planned to reapply/adapt this patch for the 1.3.2 release when we > migrate to it and maybe later to the 1.4 > > I'm open to suggestion or to help/develop this feature upstream if you > want. > > > Le lun. 2 oct. 2017 à 19:09, Piotr Nowojski <pi...@data-artisans.com> a > écrit : > >> We are planning to work on this clean shut down after releasing Flink >> 1.4. Implementing this properly would require some work, for example: >> - adding some checkpoint options to add information about >> “closing”/“shutting down” event >> - add clean shutdown to source functions API >> - implement handling of this clean shutdown in desired sources >> >> Those are not super complicated changes but also not trivial. >> >> One thing that you could do, is to implement some super hacky filter >> function just after source operator, that you would manually trigger. >> Normally it would pass all of the messages. Once triggered, it would wait >> for next checkpoint to happen. It would assume that it is a save point, and >> would start filtering out all of the subsequent messages. When this >> checkpoint completes, you could manually shutdown your Flink application. >> This could guarantee that there are no duplicated writes after a restart. >> This might work for clean shutdown, but it would be a very hacky solution. >> >> Btw, keep in mind that even with clean shutdown you can end up with >> duplicated messages after a crash and there is no way around this with >> Kafka 0.9. >> >> Piotrek >> >> On Oct 2, 2017, at 5:30 PM, Antoine Philippot <antoine.philip...@teads.tv> >> wrote: >> >> 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 <pi...@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.philip...@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 >>> >>> >>> >> >
