Per-Tenant Quotas¶
Glance supports resource consumption quotas on tenants through the use of Keystone’s unified limits functionality. Resource limits are registered in Keystone with suitable default values, and may be overridden on a per-tenant basis. When a resource consumption attempt is made in Glance, the current consumption is computed and compared against the limit set in Keystone; the request is denied if the user is over the specified limit.
Due to the design of Glance, most of the storage-focused quotas in Glance are soft limits. Since Glance allows clients to stream image data of unknown total size during an upload or import operation, it is not possible to determine if quota has been exceeded until after the operation has completed. Thus, a user is permitted to go over their quota for a single operation, and then denied additional stored on subsequent operations. There are object-focused quotas that can help operators limit the damage caused by multiple large competing data streams. Those details are covered below.
Note
Glance also has legacy global resource limits that may be ignored if
per-tenant quotas are enabled. Currently the user_storage_quota
limit will be ignored if per-tenant quotas are used.
See the Keystone docs for more information on unified limits.
Quota Resource Types¶
Glance supports quota limits on multiple areas of resource consumption. Limits are enforced at the time in which resource consumption is attempted, so setting an existing user’s quota for any item below the current usage will only prevent them from consuming more data until they free up space.
Total Image Size¶
The image_size_total
limit defines the maximum amount of storage
(in MiB) that the tenant may consume across all of their active
images. Images with multiple locations contribute to this count
according to the number of places the image is stored. Thus, if you
have a single 1GiB image stored in four locations, the usage will be
considered to be 4GiB.
Total Staging Size¶
The Interoperable Image Import function uses a two-step upload
process, whereby a user first uploads an image into the staging
store, and then subsequently imports the image to the final
destination(s). The staging store is generally local storage on the
API workers themselves, and thus is likely at somewhat of a premium,
compared to the bulk shared storage allocated for general images. The
image_stage_total
limit defines the total amount of staging space
that may be used. This should be set to a value sufficient to allow
a user to import one or more images at the same time, according to
your desired level of parallelism. It may be appropriate to provide
the user with a very generous image_size_total
quota, but a
relatively restrictive image_stage_total
allocation, effectively
limiting them to one image being imported at any given point.
Keep in mind that images being imported using the web-download
method will need to fit within this allocation as well, as those are
first downloaded to the staging store before being imported to the
final destination(s). Images being copied from one store to another
using the copy-image
method are similarly affected. Note that the
conventional image upload method does not stage the image, and thus is
not impacted by this limit.
Total Number of Images¶
The image_count_total
limit controls the maximum number of image
objects that the user may have, regardless of the individual or
collective sizes or impact to storage. This limit may be useful if you
wish to prevent users from taking thousands of small server snapshots
without ever deleting them.
Total Number of In-Progress Uploads¶
Because Glance can not enforce storage-focused quotas until after a
stream is finished, it may be useful to limit the number of parallel
upload operations that can be in-progress at any single point. The
image_count_uploading
limit provides this control, and affects
conventional image upload, pre-import stage (including
web-download
and glance-direct
), as well as any copy-image
operations that may be pending. It may be desirable to limit untrusted
users to a single in-progress image upload, which will limit the
amount of damage a malicious user may be able to inflict on your image
storage if they initiate multiple simultaneous unbounded upload
streams.
Quota Strategies¶
Below are a couple of use-case example strategies for different types
of deployments. In all cases, it makes sense for image_size_total
and image_stage_total
to be set to at least the size of the
largest image you expect a user to use. The global limit on a single
image (see configuration item image_size_cap
) may be relevant as
well. Users with an image_count_total
of zero will be unable to
create any images, and with an image_count_uploading
of zero will
be able to upload data to any images.
Public cloud, users are billed per-byte: In this case, it probably makes sense to set fairly high default quota limits for each of the above resource classes, allowing users to consume as much as they are willing to pay for. It still may be desirable to set
image_stage_total
to something modest to prevent overrunning limited staging space, if you have import enabled.Private cloud, trusted users are billed by quota: In this case, each user pays for the amount of resource they are allowed to consume, instead of what they are consuming. Generally this involves billing total space, so
image_size_total
is set to their allotment, potentially with some upper bound on total images viaimage_count_total
. If they are somewhat trusted or low-impact customers, limiting the staging usage and upload count is probably not necessary, and can be left unbounded or set to some high upper bound.Private cloud, semi-trusted third party users: This case may be similar to either of the above in terms of paying for allotment or strict usage. However, the lack of full trust may suggest limiting the total number of image uploads to something like 10% of their compute quota (to allow for snapshots) and limiting staging usage to enough for one or two image imports at a time.
Configuring Glance for Per-Tenant Quotas¶
Register quota limits (optional):
If you decide to use per-tenant quotas in Glance, you must register the limits in Keystone first:
$ openstack --os-cloud devstack-system-admin registered limit create \ --service glance --default-limit 1000 --region RegionOne image_size_total +---------------+----------------------------------+ | Field | Value | +---------------+----------------------------------+ | default_limit | 1000 | | description | None | | id | 9cedfc5de80345a9b13ed00c2b5460f2 | | region_id | RegionOne | | resource_name | image_size_total | | service_id | e38c84a2487f49fd9864193bdc8a3174 | +---------------+----------------------------------+ $ openstack --os-cloud devstack-system-admin registered limit create \ --service glance --default-limit 1000 --region RegionOne image_stage_total +---------------+----------------------------------+ | Field | Value | +---------------+----------------------------------+ | default_limit | 1000 | | description | None | | id | 5a68712b6ba6496d823d0c66e5e860b9 | | region_id | RegionOne | | resource_name | image_stage_total | | service_id | e38c84a2487f49fd9864193bdc8a3174 | +---------------+----------------------------------+ $ openstack --os-cloud devstack-system-admin registered limit create \ --service glance --default-limit 100 --region RegionOne image_count_total +---------------+----------------------------------+ | Field | Value | +---------------+----------------------------------+ | default_limit | 100 | | description | None | | id | beb91b043296499f8e6268f29d8b2749 | | region_id | RegionOne | | resource_name | image_count_total | | service_id | e38c84a2487f49fd9864193bdc8a3174 | +---------------+----------------------------------+ $ openstack --os-cloud devstack-system-admin registered limit create \ --service glance --default-limit 100 --region RegionOne image_count_uploading +---------------+----------------------------------+ | Field | Value | +---------------+----------------------------------+ | default_limit | 100 | | description | None | | id | fc29649c047a45bf9bc03ec4a7bcb8af | | region_id | RegionOne | | resource_name | image_count_uploading | | service_id | e38c84a2487f49fd9864193bdc8a3174 | +---------------+----------------------------------+
Be sure to also set
use_keystone_quotas=True
in yourglance-api.conf
file.Tell Glance to use Keystone quotas
In the
[oslo_limit]
section, configure access to keystone:[oslo_limit] auth_url = http://controller:5000 auth_type = password user_domain_id = default username = MY_SERVICE system_scope = all password = MY_PASSWORD endpoint_id = ENDPOINT_ID region_name = RegionOne
Make sure that the MY_SERVICE account has reader access to system-scope resources (like limits):
$ openstack role add --user MY_SERVICE --user-domain Default --system all reader
See the oslo_limit docs for more information about configuring the unified limits client.
In the
[DEFAULT]
section, optionally enable per-tenant quotas:[DEFAULT] use_keystone_quotas = True
Note that you must have created the registered limits as described above if this is enabled.