There are several situations where the ability to dynamically create an Avro schema is desired. Kite provides the ability to dynamically infer an Avro schema from both CSV and JSON data. Since NiFi already contains a kite bundle for converting csv and json to Avro this feature should be an easy add.
I propose 2 new processors "InferAvroSchemaFromCSV" and "InferAvroSchemaFromJSON". These processors will reside inside of the existing "nifi-kite-bundle" and extend upon the already present third party libraries. Each processor will accept either CSV or JSON and produce as output the Avro Schema JSON and the original data that was presented to them. The processors will rely on kite to perform the actually inferring of the schema.