If the concrete type cannot be known then a proper TypeInformation cannot be created and Kryo must be used.
There may be a few cases where the TypeInformation can be deduced by the developer but not by TypeExtractor and the returns TypeInformation must be explicitly given to prevent the use of Kryo. A recent example in Gelly was a Function with input and output types the same generic interface bound to different parameters. The implementation outputs the same concrete class as the input, but this programmatic structure cannot be deduced by the TypeExtractor so a returns TypeInformation was specified. Greg > On Jun 21, 2017, at 6:21 AM, Ted Yu <yuzhih...@gmail.com> wrote: > > Greg: > Can you clarify he last part? > Should it be: the concrete type cannot be known ? > > -------- Original message -------- > From: Greg Hogan <c...@greghogan.com> > Date: 6/21/17 3:10 AM (GMT-08:00) > To: nragon <nuno.goncal...@wedotechnologies.com> > Cc: user@flink.apache.org > Subject: Re: Kafka and Flink integration > > The recommendation has been to avoid Kryo where possible. > > General data exchange: avro or thrift. > > Flink internal data exchange: POJO (or Tuple, which are slightly faster > though less readable, and there is an outstanding PR to narrow or close the > performance gap). > > Kryo is useful for types which cannot be modified to be a POJO. There are > also cases where Kryo must be used because Flink has insufficient > TypeInformation, such as when returning an interface or abstract type when > the actual concrete type can be known. > > > > > On Jun 21, 2017, at 3:19 AM, nragon <nuno.goncal...@wedotechnologies.com> > > wrote: > > > > So, serialization between producer application -> kafka -> flink kafka > > consumer will use avro, thrift or kryo right? From there, the remaining > > pipeline can just use standard pojo serialization, which would be better? > > > > > > > > -- > > View this message in context: > > http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/Kafka-and-Flink-integration-tp13792p13885.html > > Sent from the Apache Flink User Mailing List archive. mailing list archive > > at Nabble.com.
