ec2-api/doc/source/install/metadata-configuration.rst

EC2 metadata is built in between the nova-metadata and the neutron-metadata, so we need to configure Neutron so that it sends requests to ec2-api-metadata, not to the nova.

To configure OpenStack for EC2 API metadata service for Neutron add:

[DEFAULT]
nova_metadata_port = 8789

to /etc/neutron/metadata_agent.ini

then restart neutron-metadata service.