openstack/cinder-specs
Code Issues Proposed changes
5016627f04
cinder-specs/specs/pike/client-reset-state.rst
Eric Harney cb6dcc2516 Client reset-state improvements 
Implements: blueprint client-reset-state-improvements

Change-Id: Ia375cad09aabb94d71090bcff76f04dab879d684
2017-03-15 10:27:55 -04:00

4.9 KiB
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Client reset-state improvements

https://blueprints.launchpad.net/cinder/+spec/client-reset-state-improvements

Improve "reset-state" in the cinder client shell.

Problem description

The reset-state implementation in the client shell has a few issues that merit cleaning up:

We have and are adding an <x>-reset-state operation for many objects in Cinder. This results in numerous commands when we could consolidate these into one command. Consolidating things into a single command makes more sense because this is intended to be a rarely-used admin fix-up tool, and not a prominent feature of our client.

The current reset-state model also defaults to unsafe behavior. It will reset an object to "available" if a user runs it on an object without other parameters. This is not a safe path to use as a default because we have no way to know if the object is actually in an "available" state and resetting it to "available" will result in odd problems later.

Use Cases

This functionality addresses admins who need to repair broken things in Cinder to workaround bugs or failed operations.

Proposed change

  • Add a new argument to "cinder reset-state" so that it can handle all of the types of objects we would like to reset the state of.

$ cinder reset-state --type volume --state available volume-abcd

$ cinder reset-state --type snapshot --state error abcd-1234

$ cinder reset-state --type backup --state error esdf-5678

This is trickier to keep from breaking compatibility, but worthwhile. The defaulting is done in the client. We could handle this by adding a stricter check in the client using the microversion checks, so that using microversion 3.30+ requires the user to specify the desired state, but when using older API versions, the previous behavior is kept. This does not correspond with an actual API change on the server, but should work as a way to handle compat here.

  • Decide that we will no longer add <x>-reset-state operations to the client shell.
  • (Optional:) We should consider looking at attach-status and

    migration-status resets as well. These are required to be specified manually but there may be cases where it would be more consistent to handle this for the caller.

    i.e. does it ever make sense to reset a volume to "available" and not clear its attach status?

Alternatives

  • Leave things as they are and keep adding new reset operations to the client which default to hazardous behavior.
  • Start fixing things in Cinder that require use of reset state in the first place. (We should do this, but it's a long, hard, project, and out of scope here.)

Data model impact

None

REST API impact

None

Security impact

None

Notifications impact

None

Other end user impact

The cinderclient CLI changes.

Performance Impact

None

Other deployer impact

None

Developer impact

  • We should design Cinder to not require use of reset-state as a "regular" thing.
    Currently there's a model, for some operations, of:
    1. Request operation
    2. Operation fails
    3. User is notified that the operation failed by the object now being in "error" state.
    4. For some operations, the admin is now expected to reset the state back to "available" to keep things functioning.
    This could be done as:
    1. Request operation
    2. Operation fails
    3. Object is put back into previous state instead of "error"
    4. Client polls for operation status via our async messaging
    5. User now knows what happened and the admin doesn't have to perform a reset. The object is left in its "true" state.
  • Should consider what the intersection of reset-state and force-detach looks like.

Implementation

Assignee(s)

Primary assignee:

eharney

Other contributors:

tommylikehu

Work Items

Dependencies

None

Testing

Covered by unit tests in the cinder client.

Documentation Impact

Cinder shell client documentation will need updates.

References