Spring Boot Kafka Micrometer observability doesn't work with concurrency enabled

I configured my application to load beans based on properties in this way:

        @Bean
        @ConditionalOnProperty(
            prefix = "fleexi.kafka.override-concurrency",
            value = {"enabled"}
        )
        ConcurrentKafkaListenerContainerFactory<String, String> kafkaListenerContainerFactoryWithConcurrency(ConsumerFactory<String, String> kafkaConsumerFactory, FleexiKafkaProperties fleexiKafkaProperties) {
            ConcurrentKafkaListenerContainerFactory<String, String> factory = new ConcurrentKafkaListenerContainerFactory();
            factory.setConcurrency(fleexiKafkaProperties.getOverrideConcurrency().getListenerConcurrency());
            factory.getContainerProperties().setObservationEnabled(true);
            factory.setConsumerFactory(kafkaConsumerFactory);
            return factory;
        }

        @Bean
        @ConditionalOnMissingBean({ConcurrentKafkaListenerContainerFactory.class})
        ConcurrentKafkaListenerContainerFactory<String, String> kafkaListenerContainerFactory(ConsumerFactory<String, String> kafkaConsumerFactory) {
            ConcurrentKafkaListenerContainerFactory<String, String> factory = new ConcurrentKafkaListenerContainerFactory();
            factory.getContainerProperties().setObservationEnabled(true);
            factory.setConsumerFactory(kafkaConsumerFactory);
            return factory;
        }

In the first case, with concurrency enabled observabilities log traceId and spanId doesn't work.

In second case, without concurrency it works properly

Concurrency breaks observability?

EDIT: The example here: https://github.com/claudiomerli/demo-issue-spring-kafka-3459

Your problem is here:

 ConcurrentKafkaListenerContainerFactory<String, String> kafkaListenerContainerFactoryWithConcurrency(

where the default containerFactory for the @KafkaListener is indeed that kafkaListenerContainerFactory.

So, since your custom kafkaListenerContainerFactoryWithConcurrency is out of use, that is not a surprise that traces are not logged.

Try just this configuration properties instead of those beans:

spring.kafka.consumer.group-id=TEST
spring.kafka.listener.concurrency=10
spring.kafka.listener.observation-enabled=true

UPDATE

Since you cannot rely on the auto-configuration and have to use those conditional beans you can trick it like this:

    @Bean("kafkaListenerContainerFactory")
    @ConditionalOnProperty(
        prefix = "fleexi.kafka.override-concurrency",
        value = {"enabled"}
    )
    ConcurrentKafkaListenerContainerFactory<String, String> kafkaListenerContainerFactoryWithConcurrency(ConsumerFactory<String, String> kafkaConsumerFactory, FleexiKafkaProperties fleexiKafkaProperties) {

With that default factory bean name expected by the @KafkaListener.