Upgrade from a nova “baremetal” deployment to Ironic

https://blueprints.launchpad.net/nova/+spec/deprecate-baremetal-driver

This specification describes the requirements to providing an upgrade path from a deployment of the nova.virt.baremetal driver to the nova.virt.ironic driver. It outlines the data migration path and service upgrade process for such an upgrade.

Problem description

The community has split out the functionality of provisioning bare metal servers into a separate program, which includes the ironic and python-ironicclient projects. While the original intent of the nova.virt.baremetal driver was to be an experimental proof-of-concept for TripleO, it may have been deployed in some production environments to facilitate high-performance compute workloads.

It is unreasonable to expect operators who have chosen to use nova.virt.baremetal to lose all state and delete all instances during an upgrade. Migration tools will be available within Ironic.

NOTE: The service upgrade is only supported within the same release version, and will only be supported in the first integrated release containing Ironic.

For example, if this work is completed during the Juno cycle, an upgrade from “juno baremetal” to “juno ironic” will be supported, but a direct upgrade from “icehouse baremetal” to “juno ironic” will NOT be supported. That should be accomplished by first upgrading from “icehouse baremetal” to “juno baremetal” and then to “juno ironic”.

Proposed change

At the start of a release cycle following the cycle in which this work is completed, the artifacts of baremetal will be delete from the Nova tree. This includes: the baremetal virt driver, baremetal host manager, ‘nova_bm’ database schema and its migration tests.

The API extension will be replaced by a read-only proxy API. This will forward the following API commands to Ironic: - baremetal-interface-list - baremetal-node-list - baremetal-node-show

Alternatives

Three alternatives have been discussed.

  • Do not provide any upgrade path; this met with significant opposition.

  • Provide a data-only migration (eg, require that instances be deleted prior to, or as part of, the migration). This was also met with opposition.

  • Rather than a data extract-and-load script, one could enroll instances via Ironic’s REST API. This would require ironic’s REST API to accept nodes that have non-null provision_state and power_state, which it expressly does not allow today. This change would require significant changes to the provisioning API and state management within the conductor service.

Data model impact

The nova_bm schema and all supporting DB migration tests may be deleted.

REST API impact

The baremetal extension to Nova’s REST API will be replaced with a read-only proxy API to Ironic. This will check policy, and forward the user’s token to Ironic for secondary validation (Ironic requires “admin” privileges).

The following commands will NOT be proxied: - baremetal-interface-add - baremetal-interface-remove - baremetal-node-create - baremetal-node-delete

The endpoints for these methods will return a 404 NOT FOUND.

Notifications impact

None

Security impact

None

Other end user impact

None

Performance Impact

None

Other deployer impact

None

Developer impact

None

Implementation

Assignee(s)

Primary assignee:

devananda

Other contributors:

adam_g romcheg

Work Items

  • Create new API proxy/extension

  • Database extraction-and-loading script (in Ironic’s tree)

  • Flavor update script (in Ironic’s tree)

  • Operator documentation (in Ironic’s tree)

  • Grenade tests (in Grenade)

Dependencies

This proposal depends primarily upon the acceptance of the nova.virt.ironic driver into the Nova codebase, and secondarily on grenade testing of the migration script and upon several open changes in tempest which will allow Ironic to pass tempest/api/compute.

Testing

A Grenade test will need to be developed that can:

  • deploy nova with the fake virt driver

  • populate nova_bm database with baremetal nodes and interfaces that map to local VMs

  • create dummy images in glance for nova-bm’s deploy kernel and ramdisk and create a flavor referencing them

  • install ironic, build and publish new deploy kernel and ramdisk

  • perform data migration

  • reconfigure nova to use ironic, start ironic, and restart nova-compute

  • run tempest

Documentation Impact

Upgrade documentation must be written and maintained for one release cycle.

The proposed upgrade path is:

  • build ironic deploy ramdisk and load it in glance

  • create empty ironic database

  • start maintenance period

  • stop nova-compute services which are configured to use the nova.virt.baremetal driver

  • update flavor metadata in Nova to reference new deploy kernel & ramdisk

  • extract data from nova_bm and import to ironic, using the provided tool. This tool must accept separate database credentials for each database.

  • start ironic services

  • observe ironic log files to ensure take over completed w/o errors

  • reconfigure nova-scheduler to use the ironic host manager, and, if desired, the exact match scheduler filters, then restart it

  • reconfigure nova-compute service to use the nova.virt.ironic driver and the ClusteredComputeManager, then restart it

  • observe nova-compute log files to ensure it has connected to ironic and is reporting available resources accurately

  • end maintenance period