Deprecation plan for nova-baremetal
This spec outlines the process for upgrading from nova-baremetal to Ironic, and descibes the changes in Nova which will be required prior to deleting the nova-baremetal code from the Nova tree. blueprint deprecate-baremetal-driver Change-Id: I2a9e6ca2f19d5b0f80954cdec45a9eca17960fa1
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Devananda van der Veen
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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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Upgrade from a nova "baremetal" deployment to Ironic
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====================================================
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https://blueprints.launchpad.net/nova/+spec/deprecate-baremetal-driver
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This specification describes the requirements to providing an upgrade path from
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a deployment of the nova.virt.baremetal driver to the nova.virt.ironic driver.
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It outlines the data migration path and service upgrade process for such an
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upgrade.
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Problem description
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===================
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The community has split out the functionality of provisioning bare metal
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servers into a separate program, which includes the ironic and
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python-ironicclient projects. While the original intent of the
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nova.virt.baremetal driver was to be an experimental proof-of-concept for
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TripleO, it may have been deployed in some production environments to
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facilitate high-performance compute workloads.
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It is unreasonable to expect operators who have chosen to use
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nova.virt.baremetal to lose all state and delete all instances during an
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upgrade. Migration tools will be available within Ironic.
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NOTE: The service upgrade is only supported within the same release version,
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and will only be supported in the first integrated release containing Ironic.
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For example, if this work is completed during the Juno cycle, an upgrade from
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"juno baremetal" to "juno ironic" will be supported, but a direct upgrade from
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"icehouse baremetal" to "juno ironic" will NOT be supported. That should be
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accomplished by first upgrading from "icehouse baremetal" to "juno baremetal"
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and then to "juno ironic".
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Proposed change
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===============
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At the start of a release cycle following the cycle in which this work is
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completed, the artifacts of baremetal will be delete from the Nova tree.
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This includes: the baremetal virt driver, baremetal host manager, 'nova_bm'
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database schema and its migration tests.
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The API extension will be replaced by a read-only proxy API. This will forward
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the following API commands to Ironic:
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- baremetal-interface-list
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- baremetal-node-list
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- baremetal-node-show
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Alternatives
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------------
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Three alternatives have been discussed.
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* Do not provide any upgrade path; this met with significant opposition.
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* Provide a data-only migration (eg, require that instances be deleted
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prior to, or as part of, the migration). This was also met with opposition.
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* Rather than a data extract-and-load script, one could enroll instances
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via Ironic's REST API. This would require ironic's REST API to accept nodes
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that have non-null provision_state and power_state, which it expressly
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does not allow today. This change would require significant changes
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to the provisioning API and state management within the conductor service.
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Data model impact
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-----------------
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The nova_bm schema and all supporting DB migration tests may be deleted.
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REST API impact
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---------------
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The baremetal extension to Nova's REST API will be replaced with a read-only
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proxy API to Ironic. This will check policy, and forward the user's token
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to Ironic for secondary validation (Ironic requires "admin" privileges).
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The following commands will NOT be proxied:
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- baremetal-interface-add
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- baremetal-interface-remove
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- baremetal-node-create
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- baremetal-node-delete
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The endpoints for these methods will return a 404 NOT FOUND.
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Notifications 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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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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devananda
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Other contributors:
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adam_g
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romcheg
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Work Items
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----------
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* Create new API proxy/extension
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* Database extraction-and-loading script
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(in Ironic's tree)
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* Flavor update script
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(in Ironic's tree)
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* Operator documentation
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(in Ironic's tree)
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* Grenade tests
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(in Grenade)
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Dependencies
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============
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This proposal depends primarily upon the acceptance of the nova.virt.ironic
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driver into the Nova codebase, and secondarily on grenade testing of the
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migration script and upon several open changes in tempest which will allow
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Ironic to pass tempest/api/compute.
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Testing
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=======
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A Grenade test will need to be developed that can:
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* deploy nova with the fake virt driver
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* populate nova_bm database with baremetal nodes and interfaces that map to
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local VMs
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* create dummy images in glance for nova-bm's deploy kernel and ramdisk and
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create a flavor referencing them
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* install ironic, build and publish new deploy kernel and ramdisk
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* perform data migration
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* reconfigure nova to use ironic, start ironic, and restart nova-compute
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* run tempest
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Documentation Impact
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====================
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Upgrade documentation must be written and maintained for one release cycle.
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The proposed upgrade path is:
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* build ironic deploy ramdisk and load it in glance
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* create empty ironic database
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* start maintenance period
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* stop nova-compute services which are configured to use the
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nova.virt.baremetal driver
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* update flavor metadata in Nova to reference new deploy kernel & ramdisk
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* extract data from nova_bm and import to ironic, using the provided tool.
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This tool must accept separate database credentials for each database.
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* start ironic services
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* observe ironic log files to ensure take over completed w/o errors
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* reconfigure nova-scheduler to use the ironic host manager, and, if desired,
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the exact match scheduler filters, then restart it
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* reconfigure nova-compute service to use the nova.virt.ironic driver
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and the ClusteredComputeManager, then restart it
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* observe nova-compute log files to ensure it has connected to ironic and is
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reporting available resources accurately
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* end maintenance period
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References
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==========
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https://etherpad.openstack.org/p/juno-nova-deprecating-baremetal
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https://etherpad.openstack.org/p/juno-nova-mid-cycle-meetup
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https://review.openstack.org/#/q/topic:ironic_grenade,n,z
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https://review.openstack.org/#/q/topic:ironic_tempest,n,z
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