Comment 9 for bug 1796074

Reviewed: https://review.openstack.org/608040
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=ab5fc6870260d3b3c3bce90a7123c17816bf0093
Submitter: Zuul
Branch: master

commit ab5fc6870260d3b3c3bce90a7123c17816bf0093
Author: melanie witt <email address hidden>
Date: Thu Oct 4 17:37:59 2018 +0000

    De-dupe subnet IDs when calling neutron /subnets API

    In the _get_subnets_from_port method, we call the neutron /subnets API
    to list subnets filtered by subnet IDs. We get the subnet IDs by
    iterating all of the fixed IPs for the instance and sending the list of
    corresponding subnet IDs. The python-neutronclient sends the list of
    subnet IDs as a query string in the URI. When an instance has a large
    number of interfaces attached, the list of subnet IDs can be too long
    for the URI, resulting in a RequestURITooLong error from neutronclient.

    This de-dupes the subnet IDs before calling neutron, to handle the case
    where an instance has a large number of interfaces attached, but many
    of them are on the same subnet.

    Closes-Bug: #1796074

    Change-Id: I5b52ff81f74ae7cb11e6f012ab7e53cfc6821486