Introduce Cyborg Resource Quota -- Usage Part
The concept of quota gives the possibility to limit the maximum number of acceleration resources that one project/tenant can prossess. It will also give the admin users the ability to increase the resource count on-demand, given that the system constraints are not exceeded. Change-Id: I554b9d4603d5e65f69c2b924fba66565f7f6c3c4 Partially-Implements: blueprint cyborg-resource-quota
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Xinran WANG
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@ -10,3 +10,4 @@ ChangeLog
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# Sample profile
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etc/cyborg/policy.json.sample
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.idea/*
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204
doc/specs/rocky/resource-quotas.rst
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204
doc/specs/rocky/resource-quotas.rst
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..
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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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Quota Usage for Cyborg Resources
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================================
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Launchpad blueprint:
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https://blueprints.launchpad.net/openstack-cyborg/+spec/cyborg-resource-quota
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There are multiple ways to slice an OpenStack cloud. Imposing quota on these
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various slices puts a limitation on the amount of resources that can be
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consumed which helps to guarantee "fairness" or fair distribution of resources
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at the creation time. If a particular project needs more resources, the
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concept of quota gives the ability to increase the resource count on-demand,
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given that the system constraints are not exceeded.
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Problem description
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===================
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At present in Cyborg we don't have the concept of Quota on acceleration
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resources, so users can consume as many resources as they want.
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Quotas are tied closely to physical resources and billable entities, hence from
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Cyborg's perspective, it helps to limit the allocation and consumption
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of a particular kind of resources at a certain value.
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In place of implementing quota like other services, we want to enable
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the unified limit which is provided by Keystone to manage our quota limit[1].
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With unified limits, all limits will be set in Keystone and enforced by
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oslo.limit. So we decided to implement quota usage part first.
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Once the oslo.limit is ready for other services, Cyborg will invoke oslo.limit
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to get the limit information and do limit check etc.
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This specs aims at the implementation of quota usage in Cyborg. As the
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oslo.limit is not finished yet, we can directly set the value of limit
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manually, and reserved the function calling oslo.limit with a "pass" inside.
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Use cases
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---------
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Alice is an admin. She would like to have a feature which will give her
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details of Cyborg acceleration resource consumptions so that she can manage her
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resources appropriately.
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She might run into following scenarios:
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* Ability to know current resource consumption.
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* Ability to prohibit overuse by a project.
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* Prevent situation where users in a project get starved because users in
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other project consume all the resource. "Quota Management" would help to
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gurantee "fairness".
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* Prevent DOS kind of attacks, abuse or error by users, which leads to an
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excessive amount of resources allocation.
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Proposed change
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===============
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Proposed changes are introducing a Quota_Usage Table which primarily stores
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the quota usage assigned for each resource in a project, and a Reservation
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Table to store every modification of resource usage.
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When a new resource allocation request comes, the 'reserved' field in the Quota
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usages table will be updated. This acceleration resource is being used to set
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up VM. For example, the fpga quota hardlimit is 5 and 3 fgpas have
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already been used, then two new fpga requests come in. Since we have 3 fpgas
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already used, the 'used' field will be set to 3. Now the 'reserved'
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field will be set to 2 untill the fpga attachment is successful. Once
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the attachment is done this field will be reset to 0, and the 'used'
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count will be updated from 3 to 5. So at this moment, hardlimit is 5, used
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is 5 and in-progress is 0. So there is one more request comes in, this request
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will be rejected since there is not enough quota available.
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In general,
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Resource quota available = Resource hard_limit - [
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(Resource reserved + Resources already allocated for project)]
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In this specs, we just focus on the update of quota usage and we will not check
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if one user has already exceed his quota limit. The limit management will be
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set in Keystone in the future and we just need to invoke the oslo.limit.
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Alternatives
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------------
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At present there is no quota infrastructure in Cyborg.
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Adding Quota Management layer at the Orchestration layer could be an
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alternative.However, our approach will give a finer view of resource
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consumptions at the IaaS layer which can be used while provisioning Cyborg
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resources.
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Data model impact
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-----------------
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New Quota usages and reservation table will be introduced to Cyborg database to
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store quota consumption for each resource in a project.
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Quota usages table:
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+---------------+--------------+------+-----+---------+----------------+
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| Field | Type | Null | Key | Default | Extra |
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+---------------+--------------+------+-----+---------+----------------+
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| created_at | datetime | YES | | NULL | |
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| updated_at | datetime | YES | | NULL | |
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| id | int(11) | NO | PRI | NULL | auto_increment |
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| project_id | varchar(255) | YES | MUL | NULL | |
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| resource | varchar(255) | NO | | NULL | |
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| reserved | int(11) | NO | | NULL | |
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| used | int(11) | NO | | NULL | |
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+---------------+--------------+------+-----+---------+----------------+
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Quota reservation table:
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+------------+--------------+------+-----+---------+----------------+
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| Field | Type | Null | Key | Default | Extra |
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+------------+--------------+------+-----+---------+----------------+
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| created_at | datetime | YES | | NULL | |
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| updated_at | datetime | YES | | NULL | |
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| deleted_at | datetime | YES | | NULL | |
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| deleted | tinyint(1) | YES | | NULL | |
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| id | int(11) | NO | PRI | NULL | auto_increment |
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| uuid | varchar(36) | NO | | NULL | |
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| usage_id | int(11) | NO | MUL | NULL | |
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| project_id | varchar(255) | YES | MUL | NULL | |
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| resource | varchar(255) | YES | | NULL | |
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| delta | int(11) | NO | | NULL | |
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| expire | datetime | YES | | NULL | |
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+------------+--------------+------+-----+---------+----------------+
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We will also introduce QuotaEngine class which represents the set of
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recognized quotas and DbQuotaDriver class which performs check to enforcement
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of quotas and also allows to obtain quota information.
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REST API impact
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---------------
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Not sure if we need to expose GET quota usage before oslo.limit settle down.
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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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None
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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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None
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Developer impact
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----------------
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None
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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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Xinran WANG
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Other contributors:
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None
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Work Items
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----------
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* Introduce Quota usages and Reservation table in Cyborg databases.
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* Update these two tables during allocation and deallocation of resources.
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* Reserve the place of function which will invoke oslo.limit with a "pass"
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inside.
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* Add rollback mechanism when allocation fails.
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Dependencies
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============
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None
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Testing
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=======
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* Each commit will be accompanied with unit tests.
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* Gate functional tests will also be covered.
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Documentation Impact
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====================
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None
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References
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==========
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[1] https://review.openstack.org/#/c/540803
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