conductor should cache barbican certs for periodic tasks

[Ricardo Rocha]

When running the periodic tasks the Magnum conductor gets each cluster's certificate to contact them and perform some checks. This is ok, but as we increase the number of clusters it seems to do quite a few queries to Barbican in sequence, and every time the periodic tasks run.

Looking forward it might be a good idea to cache the certs in the conductor after retrieval from Barbican? This should prevent too much load in the future as the number of clusters increases.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/534364

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/534364
Committed: https://git.openstack.org/cgit/openstack/magnum/commit/?id=d9e590bdc615e0c23b790a65023d01a9e9611176
Submitter: Zuul
Branch: master

commit d9e590bdc615e0c23b790a65023d01a9e9611176
Author: Kirsten G <email address hidden>
Date: Mon Jan 15 22:04:49 2018 -0800

    Cache barbican certs for periodic tasks

    Added configuration parameter, temp_cache_dir, to magnum.conf with
    default value of "/var/lib/magnum/certificate-cache". This local
    directory will hold cached cluster TLS credentials that are generated
    during periodic tasks, to reduce load as the number of clusters
    increases. If the temp_cache_dir does not exist, the certificates
    will be created as tempfiles.

    Closes-Bug: #1659545

    Change-Id: I8808c4098a7c8d22dbfc841142c9f9c8b976dde1

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/magnum 7.0.0 release.