"No fields were detected for class org.apache.beam.sdk.util.WindowedValue" - flink runner

[Sigalit Eliazov <e....@gmail.com>]

Hi all,

I'm encountering an issue while deploying the pipeline to the Flink runner.
The pipeline reads an Avro message from Kafka, applies a global window,
performs a simple transformation, and then sends the data back to Kafka.

The problem arises when I see the following error in the job manager: "No
fields were detected for class org.apache.beam.sdk.util.WindowedValue, so
it cannot be used as a POJO type and must be processed as a GenericType.
Please refer to the Flink documentation on 'Data Types & Serialization' for
details on the effect on performance."

I have double-checked that the objects align with the "rules" specified in
the Flink documentation on "Data Types & Serialization." Surprisingly, the
error occurs even when I try to read a simple string message. Is anyone
familiar with this error message? Any ideas on how to resolve it?

thanks

Sigalit