f0b8204072
As discussed at our nova meetings, reorganize the juno specs into three directories: - proposed: things proposed which weren't approved - approved: things we approved but didn't implement - implemented: things approved and implemented The first I suspect is the most controversial. I've done this because I worry about the case where a future developer wants to pick up something dropped by a previous developer, but has trouble finding previous proposed specifications on the topic. Note that the actual proposed specs for Juno are adding in a later commit. Change-Id: Idcf55ca37a83d7098dcb7c2971240c4e8fd23dc8
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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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Make Resource Tracker Use Objects
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==========================================
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https://blueprints.launchpad.net/nova/+spec/make-resource-tracker-use-objects
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This blueprint was approved for Icehouse but missed feature freeze.
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Nova is converting data structures it uses to communicate via RPC and through
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the database to use an object encapsulation called Nova Objects. This supports
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of multi-versioning for live-upgrade and database schema independence. This
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blueprint covers the conversion of the resource tracker to use Nova Objects.
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Problem description
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===================
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Conversion to Nova Objects will replace dict data structures that are currently
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communicated via the conductor API with Nova Object versions. Where necessary
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the Nova Objects will be extended to cover parameters that are not already
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implemented.
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Proposed change
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===============
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The Nova Object classes that will be used include:
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- ComputeNode
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- Instance
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- Migrations
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- Flavor
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- Service
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The ComputeNode object is currently missing some parameters that exist
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in the compute_nodes table and are used in the resource tracker. The
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following parameters will be added to the ComputeNode:
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- host_ip
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- pci_stats
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In addition, the following fields exist in the compute_nodes table but
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are not currently used by the resource tracker. We propose not to add fields
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to the ComputeNode object unless they are used, so these fields will not
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be added as part of this blueprint.
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- extra_resources
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- supported_instances
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When complete there will be direct calls to conductor in the resource tracker.
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Alternatives
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------------
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There is another effort to split the scheduler from Nova. When the split is
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complete the resource tracker may no longer interact with the scheduler via
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the database. Initially, the scheduler-lib blueprint (see references) will
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make all compute node interaction with the scheduler go through a new
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scheduler library in the Juno-1 timeframe in preparation for the split.
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This suggests that it might be unnecessary to use the ComputeNode object at
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least. However, it is reasonable to continue using the ComputeNode object
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even if it is not used to persist data in the database, so we will go ahead
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with the existing plan to implement it.
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Data model impact
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-----------------
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The objects isolate the code from the database schema. They are written to
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operate with existing data model versions. At present the scheduler does not
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the ComputeNode object, so code there will need to tolerate changes in
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database schema or the format of data stored in fields.
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The fields that need to be added to the ComputeNode object are as follows:
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**host_ip**
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Database field type: varchar(39)
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Object field type: fields.IPAddressField()
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**pci_stats**
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Database field type: text
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Object field type: fields.ObjectField('PciDeviceList', nullable=True)
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The pci_stats field is currently populated with a PciDeviceList serialized
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as an object primitive. This is already the correct form for an object field.
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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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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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The objects are written to be compatible with the database schema used in
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Icehouse. There is no database migration associated with this blueprint and
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the format of data stored in the fields of the database will not change. This
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means that a combination of Icehouse and Juno versions of the compute nodes
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will be able to coexist and interact with the scheduler.
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Developer impact
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----------------
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Developers working on the resource tracker will be required to use the new
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objects instead of directly making database calls to conductor.
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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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pmurray
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Other contributors:
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alexisl
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Work Items
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----------
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* Use flavor object in resource tracker - (merged in Icehouse)
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* Use Service object in resource tracker
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* Use Instance object in resource tracker
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* Use Migrations object in resource tracker
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* Use ComputeNode object in resource tracker
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Several of these work items are currently ready for review:
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https://review.openstack.org/#/q/topic:bp/make-resource-tracker-use-objects,n,z
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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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This does not affect existing tempest tests. Unit tests will be
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added for each object and existing tests will be modified to deal
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with the new data structure.
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Documentation Impact
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====================
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No new features or API changes so no document impact.
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References
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==========
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https://blueprints.launchpad.net/nova/+spec/scheduler-lib
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