The nova-compute container does not have the cacert mount. 
As a result the nova-compute service can not validate the rabbitmq tls cert.
Accordingly it should be in the nova-custom-ceph service, basically
add caCerts: combined-ca-bundle and edpmServiceType: nova

The updated dnc documentation shows this example. Could you please add the following parameters to the example in this document to avoid confusion?

~~~

 edpmServiceType: nova

addCertMounts: false

caCerts: combined-ca-bundle

~~~

• updated dcn docs:

https://docs.redhat.com/fr/documentation/red_hat_openstack_services_on_openshift/18.0/html/configuring_persistent_storage/assembly_configuring-red-hat-ceph-storage-as-the-backend-for-rhosp-storage#proc_ceph-configuring-data-plane-to-use-ceph_ceph-back-end

• need to update docs:

https://docs.redhat.com/fr/documentation/red_hat_openstack_services_on_openshift/18.0/html/deploying_a_distributed_compute_node_dcn_architecture/assembly_deploying-a-dcn-node-set#proc_dcn-dataplane-configuration_deploying-a-dcn-node-set