Adding attributes to a span when using Kafka client instrumentation with opentelemetry-spring-boot-starter

[dejan-kosak]

Hi, I use "opentelemetry-spring-boot-starter" (with Kafka instrumentation included) to instrument my app.

I have Kafka producer, where I provide parent context and send the message.

// properties contains parent context information...
ProducerRecord<String, String> record = new ProducerRecord<>("topic-name", null, "key", "payload", getHeaders(properties));
Context context = PROPAGATORS.getTextMapPropagator().extract(Context.current(), record,  new TextMapGetter<ProducerRecord<String, String>>() { /* ... */ });
try (Scope _ = context.makeCurrent()) {
    kafkaTemplate.send(record);
 }

This works and I get a trace with a new span created by kafkaTemplate which is also connected with the parent context.

Now, I would like to enrich the span that is created with kafkaTemplate. For that I am creating ProducerInterceptor which is set to AbstractKafkaListenerContainerFactory.

public class TracingProducerInterceptor<K, V> implements ProducerInterceptor<K, V> {
    @Override
    public ProducerRecord<K, V> onSend(ProducerRecord<K, V> record) {
        Span span = Span.current();
        span.setAttribute("custom-attribute", "test");
        return record;
    }
}

public class KafkaContainerFactoryCustomizer {
    public <C extends AbstractMessageListenerContainer<K, V>, K, V> KafkaContainerFactoryCustomizer(AbstractKafkaListenerContainerFactory<C, K, V> factory, CompositeRecordInterceptor<K, V> compositeRecordInterceptor) {
        factory.setRecordInterceptor(compositeRecordInterceptor);
    }
}

The problem that I have is, that the span that I get in interceptor is not the span that is created by kafkaTemplate. It is the span from parent context.

How to do this the right way? Any help would be appreciated.

Thanks!