.. Copyright 2021 Red Hat, Inc. Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. .. _quotas: 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 :ref:`iir` 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 via ``image_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 ---------------------------------------- .. include:: ../install/register-quotas.rst #. Tell Glance to use Keystone quotas .. include:: ../install/configure-quotas.rst