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Merge "Cleanup quota user docs"

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Zuul
2019-07-09 19:13:47 +00:00
committed by Gerrit Code Review
parent ca44fe365e 47559663aa
commit 1f46fafcf5
1 changed files with 27 additions and 14 deletions
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doc/source/user/quotas.rst
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@@ -18,17 +18,26 @@
Nova uses a quota system for setting limits on resources such as number of
instances or amount of CPU that a specific project or user can use.
Quotas are enforced by making a claim, or reservation, on resources when a
request is made, such as creating a new server. If the claim fails, the request
is rejected. If the reservation succeeds then the operation progresses until
such a point that the reservation is either converted into usage (the operation
was successful) or rolled back (the operation failed).
Starting in the 16.0.0 Pike release the quota calculation system in nova was
overhauled and the old reserve/commit/rollback flow was changed to `count
resource usage`_ at the point of whatever operation is being performed, such
as creating or resizing a server. A check will be performed by counting
current usage for the relevant resource and then if
:oslo.config:option:`quota.recheck_quota` is True (it is by default) another
check will be performed to ensure the initial check is still valid.
Typically the quota reservation is made in the nova-api service and the usage
or rollback is performed in the nova-compute service, at least when dealing
with a server creation or move operation.
By default resource usage is counted using the API and cell databases but
nova can be configured to count some resource usage without using the cell
databases, see `Quota usage from placement`_ for details.
Quota limits and usage can be retrieved via the ``limits`` REST API.
Quota limits and usage can be retrieved via the `limits`_ REST API. Quota
limits can be set per-tenant using the `quota sets`_ REST API or per class
(all tenants) using the `quota class sets`_ API.
.. _count resource usage: https://specs.openstack.org/openstack/nova-specs/specs/pike/implemented/cells-count-resources-to-check-quota-in-api.html
.. _limits: https://developer.openstack.org/api-ref/compute/#limits-limits
.. _quota sets: https://developer.openstack.org/api-ref/compute/#quota-sets-os-quota-sets
.. _quota class sets: https://developer.openstack.org/api-ref/compute/#quota-class-sets-os-quota-class-sets
Checking quota
==============
@@ -49,8 +58,8 @@ checks are made in order:
openstack quota set --class --instances 5 default
* If the above does not provide a resource limit, then rely on the ``quota_*``
configuration options for the default limit.
* If the above does not provide a resource limit, then rely on the
:oslo.config:group:`quota` configuration options for the default limit.
.. note:: The API sets the limit in the `quota_classes` table. Once a default
limit is set via the `default` quota class, that takes precedence over
@@ -132,7 +141,11 @@ See the :ref:`cells documentation <cells-counting-quotas>` for details.
Future plans
============
TODO: talk about quotas in the `resource counting spec`_ and `nested quotas`_
Hierarchical quotas
-------------------
.. _resource counting spec: https://specs.openstack.org/openstack/nova-specs/specs/ocata/approved/cells-count-resources-to-check-quota-in-api.html
.. _nested quotas: https://specs.openstack.org/openstack/nova-specs/specs/mitaka/approved/nested-quota-driver-api.html
There has long been a desire to support hierarchical or nested quotas
leveraging support in the identity service for hierarchical projects.
See the `unified limits`_ spec for details.
.. _unified limits: https://review.opendev.org/#/c/602201/