Producer throws an exception - Confluent.SchemaRegistry.SchemaRegistryException: Incompatible artifact: <topic name>[AVRO]; error code: 409

[mastery-sanket-nagare]

We are supposed to add new fields in the existing schema for an existing topic, for which we added those field in the POCO classes and tried to generate a message. We received the exception Exception occured while preparing a kafka producer : Incompatible artifact: [AVRO]; error code: 409 Confluent.SchemaRegistry.SchemaRegistryException: Incompatible artifact: [AVRO]; error code: 409

We have set registerAutomatically setting to AutomaticRegistrationBehavior.Always. Here is the code snippet for the producer configuration

var typeResolver = new ReflectionResolver( resolveReferenceTypesAsNullable: true // this is the important line );

            var schemaRegistry = new CachedSchemaRegistryClient(schemaRegistryConfig);
            var schemaBuilder = new SchemaBuilder(typeResolver: typeResolver);
            var serializerBuilder = new SchemaRegistrySerializerBuilder(schemaRegistry, schemaBuilder: schemaBuilder);
            var producerBuilder = new ProducerBuilder<TKey, TValue>(producerConfig);
            producerBuilder = producerBuilder.SetAvroValueSerializer(serializerBuilder, this.Topic, registerAutomatically: AutomaticRegistrationBehavior.Always).GetAwaiter().GetResult();
            this.Getproducer = producerBuilder
                    .SetAvroKeySerializer(schemaRegistry, AutomaticRegistrationBehavior.Always)
                    .Build();`

[mastery-sanket-nagare]

@dstelljes Could you please help me with this?

[dstelljes]

Try adjusting the subject compatibility level. You can do that with an API request; currently it’s not possible to change the compatibility level using the Confluent.SchemaRegistry library.

To add fields, the compatibility level either needs to be FORWARD or NONE: https://docs.confluent.io/platform/current/schema-registry/avro.html#summary