Rollback Mechanism

https://blueprints.launchpad.net/watcher/+spec/rollback-mechanism

Problem description

After every audit, there would be one actionplan to execute. The actionplan is a group of actions, such as:

• migrations

• change nova service state

• change node power state

• …

Sometimes, the users want to rollback one actionplan even after the actionplan successfully executed.

To tester, they usually make the env unbalance, so that there will be instances migration during audit. After that they need to migrate the instances back to the source host for next test.

Moreover, for host maintenance, it will migrate all instances from the maintaining host to others. After the host maintenance and active again, there is no mechanism to migrate the instances automatically back to the maintaining host.

Use Cases

As a QA of Watcher, I want to rollback the actionplan, so that I can easily restore the environment for next test.

As an openstack operator, I want to migrate the instances back to the source node after the node having been executed “host maintenance” strategy.

Proposed change

In watcher-api, we can add ‘rollback’ action to ActionPlan API. When the api recieves the rollback request and then distributes the request to watcher-decision-engine module.

In watcher-decision-engine, it retrives the actionplan and records every rollback of the actions which belong to the actionplan, then return the rollback result to watcher-api.

Because the compute data model changes by time, the actionplan is possible to rollback failed. To make the rollback mechanism to work as far as possible, only recent(default, recent in one hour) actionplan is allowed to rollback.

Alternatives

None

Data model impact

None

REST API impact

Rollback Action Plan

• /v1/action_plans/{actionplan_ident}/rollback

  • Method type: POST

  • actionplan_ident：UUID of the Action Plan

  • Normal http response code(200)

  • Expected error http response code(400,404)

Security impact

None

Notifications impact

None

Other end user impact

None

Performance Impact

None

Other deployer impact

None

Developer impact

None

Implementation

Assignee(s)

Primary assignee:

<sue>

Work Items

• ActionPlan rollback action API

• RollBack mechanism for one actionplan

Dependencies

None

Testing

Unit tests

Documentation Impact

• Add documentation about how to use the new feature

References

None

History

Revisions

Release Name	Description
Ussuri	Introduced