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From "Katsipoulakis, Nikolaos Romanos" <kat...@cs.pitt.edu>
Subject When is the StreamPartitioner<T> selectChannel() method called
Date Wed, 25 Jan 2017 13:12:44 GMT
Hello all,

I have been looking into different StreamPartitioner<T> implementations of Flink, and
I noticed they come with an implementation of selectChannel(), as defined in the ChannelSelector<T>
interface. In order to understand better the actions of a StreamPartitioner during execution,
I set up Flink on a single server with one TaskManager that had 16 slots. Then, I submitted
a job, with a HashPartitioner (through a keyBy() transformation), and remote debugged it to
see when the HashPartitioner's selectChannel() method is called. Unfortunately, the breakpoint
is never reached and the job completes successfully. Is the previous behavior normal? If yes,
why is the breakpoint never reached? Does it have to do with running the job in an environment
with local slots? Also, what determines the number of channels when a job is executed? Does
it have to do with the number of available slots in the downstream operation of the partitioner?

Thank you for your time and I appreciate any answers/comments/indications.

Kind Regards.

Nikos R. Katsipoulakis
Department of Computer Science,
University of Pittsburgh


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