Performance issue when deleting trusts

[Jose Castro Leon]

During a trust deletion, the backend will fetch all trusts belonging to the same trustor and find if there is any delegated trust based on the one we are deleting. So it can delete it as well.

If the backend list_trusts_for_trustor returns a considerable amount of trusts, the whole process will load a huge amount of memory and loop over it. On 380k trusts with no redelegation, the api call takes 35 seconds to process and 2.5 GB of memory while looping.

Just by passing the filter to the backend and filter out the trusts that have delegation, the api call takes around a second with no further increase in memory utilisation.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/keystone/+/800606

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/keystone/+/800606
Committed: https://opendev.org/openstack/keystone/commit/23477a13ab29e952a77184c5cf989ecfa175a3ab
Submitter: "Zuul (22348)"
Branch: master

commit 23477a13ab29e952a77184c5cf989ecfa175a3ab
Author: Jose Castro Leon <email address hidden>
Date: Tue Jul 13 11:00:58 2021 +0200

    Improve performance on trust deletion

    During a trust deletion, the backend will fetch all trust by the same
    trustor and look for redelegations to be deleted as well. If you have
    a considerable amount of trusts that call becomes expensive. Just by
    pushing this filter into the backend, the response time for the api call
    just depends on the number of redelegations for that trust.

    Change-Id: Id3a820fca0bb20561ba031797d2b0fb96ba1f78d
    Closes-Bug: #1935840

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/keystone 21.0.0.0rc1 release candidate.