Merge "Propose tooling and docs for unified limits"
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Zuul
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This work is licensed under a Creative Commons Attribution 3.0 Unported
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License.
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http://creativecommons.org/licenses/by/3.0/legalcode
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===================================
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Tooling and Docs for Unified Limits
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===================================
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https://blueprints.launchpad.net/nova/+spec/unified-limits-nova-tool-and-docs
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In the Yoga release support for Unified Limits was added in Nova as an
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experimental feature to get early feedback and fix issues that were found by
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operators trying it out. Now that a few releases have passed, we want to go
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ahead and formalize the unified limits quota driver by creating a tool to help
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operators copy their existing legacy quota limits from Nova to unified limits
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in Keystone, publish official documentation in the Nova quota documentation,
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and removing the note on the ``[quota]driver=nova.quota.UnifiedLimitsDriver``
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config option indicating its experimental status.
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.. note::
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There are no immediate plans to deprecate legacy quota system in Nova at
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this time. The objective of this work is to provide a better experience for
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users who are opting in to using unified limits in Nova.
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Problem description
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===================
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Currently there is no documentation in the Nova docs about unified limits and
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there isn't any automated tool for generating unified limits in Keystone from
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existing Nova legacy quota limits.
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Use Cases
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---------
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* As an operator, I would like to use a tool to automatically copy my existing
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legacy quota limits from Nova to unified limits in Keystone.
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* As an operator, I would like formal documentation for unified limits quotas
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to be available.
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Proposed change
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===============
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We propose to create an automated tool, for example,
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``nova-manage limits migrate_to_unified_limits`` that will read existing legacy
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quota limits from the Nova database and config options and create equivalent
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unified limits for them in Keystone using the Keystone REST API. It will be
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able to migrate both default limits and project-scoped limits. It will not
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migrate user-scoped limits as they are not supported by unified limits.
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The ``nova-manage`` command will follow the precedence for `checking quota`_
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and:
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#. Check the ``nova_api.quotas`` database table and for each row call the
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Keystone ``POST /limits`` API with the project_id, resource name, and
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resource_limit. These are the project-scoped limits.
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#. Check the ``nova_api.quota_classes`` database table to see if there are rows
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with class_name ``default``. If there are, for each row with class_name
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``default`` call the Keystone ``POST /registered_limits`` API with the
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resource_name and default_limit. These are the default limits that apply to
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all projects.
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#. Check the following config options:
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.. code-block:: ini
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[quota]
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instances
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cores
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ram
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metadata_items
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injected_files
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injected_file_content_bytes
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injected_file_path_length
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key_pairs
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server_groups
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server_group_members
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For each config option, use its set value or default value to call the
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Keystone ``POST /registered_limits`` API with the resource_name and
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default_limit, if the resource_name does not already have a registered limit
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in Keystone. These are default limits that apply to all projects.
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#. The ``nova_api.project_user_quotas`` database table will be ignored because
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user-scoped limits are not supported by unified limits.
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.. _checking quota: https://docs.openstack.org/nova/latest/admin/quotas.html#checking-quota
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We will add formal docs about unified limits to the Nova docs and remove the
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note on the ``[quota]driver`` config option about the
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``nova.quota.UnifiedLimitsDriver`` being in a development state.
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Alternatives
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------------
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Operators can create unified limits using the ``openstack limit`` openstack
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client commands without a provided tool.
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Data model impact
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-----------------
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None
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REST API impact
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---------------
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None
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Security impact
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---------------
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None
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Notifications impact
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--------------------
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None
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Other end user impact
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---------------------
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End users will be able to read documentation about how quotas work with unified
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limits.
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Performance Impact
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------------------
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None
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Other deployer impact
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---------------------
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Deployers will have the option of using the quota limit migration tool to copy
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existing legacy Nova quota limits into Keystone unified limits instead of using
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openstackclient commands or otherwise calling the Keystone REST API manually.
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Developer impact
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----------------
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None
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Upgrade impact
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--------------
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There is no upgrade impact with the quota limit migrate tool in that there is
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no restriction on when operators can run the tool. They can copy quota limits
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into Keystone at any time, unrelated to an upgrade. The only requirements are
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that the Keystone API needs to be available and ``nova-manage`` must have
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access to a Nova config that has ``[api_database]connection`` configured so
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that it can access the Nova quota database tables.
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Implementation
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==============
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Assignee(s)
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-----------
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Primary assignee:
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melwitt
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Other contributors:
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None
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Feature Liaison
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---------------
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Feature liaison:
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melwitt
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Work Items
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----------
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* Develop a ``nova-manage limits migrate_to_unified_limits`` command to copy
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existing legacy Nova quota limits from the Nova database and config options
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to unified limits by calling the Keystone REST API
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* Write documentation for unified limits in Nova
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* Remove note from ``[quota]driver=nova.quota.UnifiedLimitsDriver`` about the
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driver being in a development state
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* Collaborate with Keystone team to remove the docs warning in
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https://docs.openstack.org/keystone/latest/admin/unified-limits.html
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about the unified limits API labeled as experimental
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Dependencies
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============
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* https://specs.openstack.org/openstack/nova-specs/specs/yoga/implemented/unified-limits-nova.html
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Testing
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=======
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Unit and/or functional testing for the quota limit migrate tool wil be added.
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We can also test the quota limit migrate tool alongside the existing
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nova/tools/hooks/post_test_hook.sh unified limits coverage in the nova-next CI
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job.
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Documentation Impact
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====================
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Operators will be most affected by the addition of Nova unified limits
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documentation. The following docs will need to be updated:
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* https://docs.openstack.org/nova/latest/user/quotas.html
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* https://docs.openstack.org/nova/latest/admin/quotas.html
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* https://docs.openstack.org/nova/latest/cli/nova-manage.html
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References
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==========
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* https://etherpad.opendev.org/p/nova-bobcat-ptg#L415
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* https://docs.openstack.org/keystone/latest/admin/unified-limits.html
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History
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=======
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.. list-table:: Revisions
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:header-rows: 1
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* - Release Name
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- Description
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* - 2023.2 Bobcat
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- Introduced
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