Unable to serialise avro optional Decimal

Describe the bug

Avro union types of Decimal do not serialise but throw

2021-10-18 17:51:46,311 ERROR [io.sma.rea.mes.kafka] (smallrye-kafka-producer-thread-0) SRMSG18212: Message org.eclipse.microprofile.reactive.messaging.Message$8@5702ccea was not sent to Kafka topic 'com.fnz.test.sink' - nacking message: org.apache.kafka.common.errors.SerializationException: Error serializing Avro message
Caused by: org.apache.avro.UnresolvedUnionException: Not in union ["null",{"type":"bytes","logicalType":"decimal","precision":13,"scale":6}]: 0.26268382480788643
	at org.apache.avro.generic.GenericData.resolveUnion(GenericData.java:877)
	at org.apache.avro.generic.GenericDatumWriter.resolveUnion(GenericDatumWriter.java:272)
	at org.apache.avro.generic.GenericDatumWriter.writeWithoutConversion(GenericDatumWriter.java:143)
	at org.apache.avro.specific.SpecificDatumWriter.writeField(SpecificDatumWriter.java:98)
	at org.apache.avro.generic.GenericDatumWriter.writeRecord(GenericDatumWriter.java:210)
	at org.apache.avro.specific.SpecificDatumWriter.writeRecord(SpecificDatumWriter.java:83)
	at org.apache.avro.generic.GenericDatumWriter.writeWithoutConversion(GenericDatumWriter.java:131)
	at org.apache.avro.generic.GenericDatumWriter.write(GenericDatumWriter.java:83)
	at org.apache.avro.generic.GenericDatumWriter.write(GenericDatumWriter.java:73)
	at io.confluent.kafka.serializers.AbstractKafkaAvroSerializer.serializeImpl(AbstractKafkaAvroSerializer.java:135)
	at io.confluent.kafka.serializers.KafkaAvroSerializer.serialize(KafkaAvroSerializer.java:61)
	at org.apache.kafka.common.serialization.Serializer.serialize(Serializer.java:62)
	at org.apache.kafka.clients.producer.KafkaProducer.doSend(KafkaProducer.java:925)
	at org.apache.kafka.clients.producer.KafkaProducer.send(KafkaProducer.java:885)
	at io.smallrye.reactive.messaging.kafka.impl.ReactiveKafkaProducer.lambda$send$3(ReactiveKafkaProducer.java:102)

Serialisers all seem to work when I use them directly - either using Avro or using the KafkaAvroSerializer but when they are used within quarkus messages fail to serialise

Expected behavior

serialised and sent messages

Actual behavior

Exception and messages not sent

How to Reproduce?

Check out project:

https://github.com/msillence/quarkus-avro-decimal-bug

docker-compose up -d

in the project home

add mskafka and schema-registry to your hosts file pointing to your localhost

Run the quarkus application and you will see serialisation errors every second

Run the unit tests and they all pass

Output of uname -a or ver

Linux JHC8700TP 4.19.128-microsoft-standard #1 SMP Tue Jun 23 12:58:10 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

Output of java -version

openjdk version “17” 2021-09-14

GraalVM version (if different from Java)

No response

Quarkus version or git rev

2.3.0.Final

Build tool (ie. output of mvnw --version or gradlew --version)

apache-maven-3.8.1

Additional information

I have been trying to capture how the serialiser is constructed in the tests here:

https://github.com/msillence/quarkus-avro-decimal-bug/blob/master/src/test/java/com/fnz/schema/SinkValueTest.java

specifically the first tests is meant to be similar to how the serialiser is constructed in quarkus but it all works under test so I feel this is difficult to pin on either avro or the confluent kafak serialiser