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Building schemas is tedious work and fraught with errors. The InferAvroSchema processor can get you started. It generates a compliant schema for use. There is one caveat, you have to make sure you are using Apache Avro safe field names. I have a custom processor that will clean your attributes if you need them Avro-safe. See processor listed below.

Example Flow Utilizing InferAvroSchema

45381-avro.png

InferAvroSchema Details

45382-inferavroschema.png

Step 0: Use Apache NiFi to Convert Data to JSON or CSV

Step 1: Send JSON or CSV Data to InferAvroSchema

I recommend setting output destination to flowfile-attribute, input content type to json, pretty avro output to true.

Step 2: The New schema is now in attribute: inferred.avro.schema.

inferred.avro.schema
{ "type" : "record", "name" : "schema1", "fields" : [ { "name" : "table", "type" : "string", "doc" : "Type inferred from '\"schema1.tableName\"'" } ] } 

This schema can then be used for conversions directly or stored in Hortonworks Schema Registry or Apache NiFi Built-in Avro Registry.

Now you can use it for ConvertRecord, QueryRecord and other Record processing.

Example Generated Schema in Avro-JSON Format Stored in Hortonworks Schema Registry:

45383-ccda-schemareg.png

Source: https://github.com/tspannhw/nifi-attributecleaner-processor

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