In recent ClickHouse versions (21.3) Avro format for kafka does not work at all.
In ClickHouse 20.3 one Avro formatted kafka message can read, than stall forever.
Reportedly in ClickHouse prior 20.3 Avro formatted kafka messages work Ok while contain only single record
{
    
    in.tryIgnore(in.available());
}
const AvroDeserializer & AvroConfluentRowInputFormat::getOrCreateDeserializer(SchemaId schema_id)
{
    auto it = deserializer_cache.find(schema_id);
    if (it == deserializer_cache.end())
    {
        auto schema = schema_registry->getSchema(schema_id);
        AvroDeserializer deserializer(output.getHeader(), schema, format_settings);
        it = deserializer_cache.emplace(schema_id, deserializer).first;
    }
    return it->second;
}
void registerInputFormatProcessorAvro(FormatFactory & factory)