I haven't done anything in rabbitmq, so I can't help with that piece at this moment.
But something like this on the producer:
headers = {"traceparent": elasticapm.get_trace_parent_header()}
rabbitmq.queue(message, headers=headers) # I'm making this line up
On the consumer:
def consume(message, headers, client):
traceparent = ealsticapm.trace_parent_from_string(headers.get("traceparent", ""))
if traceparent:
client.begin_transaction(transaction_type="messaging", trace_parent=traceparent)
else:
client.begin_transaction(transaction_type="messaging")
Note that you can also use span links if you're already in an active transaction in your consumer. This is where you link a span to a parent transaction so that they're tied together in the trace view, even though it's not a direct parent/child relationship. There's a links argument in the capture_span context manager.
Hope that helps!