watcher-specs/specs/pike/implemented/volume-migrate-action.rst

Volume migrate action

https://blueprints.launchpad.net/watcher/+spec/volume-migrate-action

Problem description

As of now, Watcher only provides Nova migrate action. Watcher needs cinder volume migrate action for optimizing storage provided by cinder.

Use Cases

• As a developer, I want to develop storage optimization strategy which migrates cinder volume.
• As a developer, I want to develop zone migration strategy which migrates cinder volume.

Proposed change

This spec adds storage migrate action.

The schema is like the following:

schema = Schema({
    'resource_id': str,  # should be a UUID
    'migration_type': str,  # choices -> "swap", "cold"
    'destination_node': str,
    'destination_type': str,
})

Resource_id and migration_type are mandatory parameters. Default migration_type is swap.

If migration_type is "cold", This action verifies that volume is detached and has no snapshots. If false, WatcherException.Invalid exception with the message "Invalid state for cold migration" is raised and the action ends with FAILED state. If true, the action continues.

If destination_node is added, first check if volume type of source node and destination node are the same. If true, this action migrates detached volume of resource_id to destination_node by calling Cinder migration API. If false, WatcherException.Invalid exception with the message "Volume type must be same for migrating" is raised and the action ends with FAILED state.

If destination_type is added, first check if volume type of source node and destination node are different. If true, this action migrates detached volume of resource_id to destination_type by calling Cinder retype API. If false, WatcherException.Invalid exception with the message "Volume type must be different for retyping" is raised and the action ends with FAILED state.

If migration_type is "swap" then destination_type is required. If destination_type has not been provided, WatcherException.Invalid exception with the message "destination type is required when migration type is swap" is raised. Moreover, the action verifies that volume is attached and instance status is active, paused, or resized. If false, WatcherException.Invalid exception with the message "Invalid state for swapping volume" is raised and the action ends with FAILED state. If true, the action swaps attached volume of resource id. This action proceeds the following steps:

• create a temporary user in the project which created source volume
• create destination volume of destination_type by the temporary user
• swap volume from source volume to destination volume by using Nova Update a volume attachment API
• delete source volume
• delete the temporary user

Temporary user password is determined randomly for each user to reduce security risk as much as possible.

The action execution diagram is below.

if "migration_type" +------------->if "migration_type" +------>ERROR
is 'cold'?              no         is 'swap'?              no
      +                                   +
      | yes                               | yes
      |                                   v
      |                            is "destination_type" +---->ERROR
      |                            given?                  no
      |                                   +
      |                                   |yes
      |                                   v
      v                            is volume attached
is volume detached                 and instance is active
and no snapshots? +----> ERROR     paused, or resized?    +--->ERROR
      +             no                    +                no
      |                                   | yes
      | yes                               v
      |                            5 steps described above
      |
      v
is "destination_node"+------------>is "destination_type" +---->ERROR
given ?                  no        given?                  no
      +                                   +
      | yes                               | yes
      |                                   |
      v                                   v
is volume type                     is volume type
the same?                          different?
      +---------------+                   +------------------+
      |               |                   |                  |
      | yes           | no                | yes              | no
      v               v                   v                  v
call cinder migrate  ERROR         call cinder retype       ERROR

Alternatives

None

Data model impact

None

REST API impact

None

Security impact

If migration_type is swap, temporary user password can be security risk.

Notifications impact

None

Other end user impact

If migration_type is swap, creation of temporary user or destination volume may exceed quota and result in error.

Performance Impact

None

Other deployer impact

Swap migration_type works for compute libvirt driver only.

The following is added in setup.cfg.

[entry_points]
watcher_actions =
    volume_migrate = watcher.applier.actions.storage_migration:VolumeMigrate

Developer impact

None

Implementation

Assignee(s)

Primary assignee:

<nakamura-h>

Work Items

• Add volume migrate action
• Add volume migrate action entry point in setup.cfg

Dependencies

None

Testing

Unit tests should be updated.

Documentation Impact

Architecture documentation will be updated since action driver requests cinder API by this spec.

References

• https://developer.openstack.org/api-ref/compute/?expanded=#update-a-volume-attachment
• https://docs.openstack.org/cinder/latest/devref/migration.html

History

None