You could use CEP for that. First you would create a pattern of two states which matches everything. In the select function you could then check whether both elements are different.
However, this would be a little bit of an overkill for this simple use case. You could for example simply use a flat map operation which stores the last seen element. Then whenever you see a different element you can emit a change event. Cheers, Till On Wed, Apr 20, 2016 at 2:43 PM, Stefano Baghino < stefano.bagh...@radicalbit.io> wrote: > Can the CEP library be used for this use case? > > On Wed, Apr 20, 2016 at 2:02 PM, Aljoscha Krettek <aljos...@apache.org> > wrote: > >> Hi, >> this could be done by implementing a user function that keeps state or by >> using windows with a custom Trigger. On only works, however, if you only >> have one Kafka partition and if your Flink job is executing with >> parallelism=1. Otherwise we don't have any ordering guarantees on streams. >> >> Cheers, >> Aljoscha >> >> On Wed, 20 Apr 2016 at 12:50 <tole...@toletum.org> wrote: >> >>> Hi! I'm a beginner in Flink. >>> I'm reading from a Kafka topic. In this topic, I receive a character >>> each event, like that: >>> >>> Event.: 1 2 3 4 5 6 7 8 9... >>> Data..: A A A B B B B C C... >>> >>> I would like to do a "trigger" when the character is different than >>> before. For example: >>> Event º1 fire because of A is different to "null" >>> Event º4 fire because of B is different to A >>> Event º8 fire because of C is different to B >>> >>> Could it be possible? >>> >> > > > -- > BR, > Stefano Baghino > > Software Engineer @ Radicalbit >
