Audit tag in VM Metadata¶

https://blueprints.launchpad.net/watcher/+spec/audit-tag-vm-metadata

Problem description¶

Watcher optimizes workloads by live migrating VMs. This can be disruptive. There should be a feature for tenants to opt-in/opt-out some or all of their VMs from optimization. The solution we propose is to set a VM metadata “optimize” and watcher strategies should consider only those VMs that has “optimize” metadata enabled. This feature for strategies to check VM metadata should be optional and configurable.

Use Cases¶

As a tenant, I should opt-in/opt-out optimization of my VMs

As a strategy developer, I should be able to filter VMs that are approved for optimizing

Proposed change¶

The VMs will have an “optimize” metadata key. The compute cluster data model should also store the VM metadata information. We need to a have a configuration option “check_optimize_metadata” to enable this feature.

If “check_optimize_metadata” configuration option is enabled, strategy base class will include only those VMs that has optimize metadata. This will use the Audit Scope to exclude VMs by metadata.

Example -

"scope": [
     {"host_aggregates": [
       {"id": 1},
       {"id": 2},
       {"id": 3}
     ]},
     {"availability_zones": [
       {"name": "AZ1"},
       {"name": "AZ2"}
     ]},
     {"exclude": [
       {"instances": [
         {"uuid": "9766dff1-3c81-4de2-92ae-19e0d9adcec6"},
         {"uuid": "777541bb-ce4f-4bf3-8320-d5792d5cdf6e"}
       ]},
       {"instance_metadata": [
         {"optimize": "False"}
       ]},
       {"compute_nodes": [
         {"name": "compute1"}
       ]}
     ]}
   ]

By default “check_optimize_metadata” will be disabled and “optimize” metadata will not have any effect on the strategies - meaning the strategies will consider all VMs.

Alternatives¶

Data model impact¶

There will be changes to the cluster data model to include VM metadata.

REST API impact¶

Security impact¶

There is no security impact.

Notifications impact¶

Other end user impact¶

Performance Impact¶

Other deployer impact¶

Developer impact¶

Implementation¶

Assignee(s)¶

Primary assignee:: hvprash
Other contributors:: v-francoise pradeep-singh-u

Work Items¶

Platform owners or automations external to watcher will set the VM Metadata

# nova meta vm_name set optimize=True

Enhance the current compute cluster data model to now include the VM metadata in its representation.
Capability in Audit Scope to exclude by instance_metadata (https://github.com/openstack/watcher/blob/54f0758fc3ac47edb4bc3f6eb5e56bf53d4e02f8/watcher/decision_engine/scope/default.py).
Modify base strategy to filter VMs by metadata based on configuration option

def filter_instances_by_audit_tag(self, instances):
    if not self.config.check_optimize_metadata:
        return instances
    instances_to_migrate = []
    for instance in instances:
        optimize = True
        if instance.metadata:
            try:
                optimize = strutils.bool_from_string(
                    instance.metadata.get('optimize'))
            except ValueError:
                optimize = False
        if optimize:
            instances_to_migrate.append(instance)
    return instances_to_migrate

Dependencies¶

N/A

Testing¶

Unit tests on watcher Audit and Strategy
Unit tests for audit scope. Also tempest scenarios to create an Audit Template and define an Audit scope with “instance_metadata”

Documentation Impact¶

Update documentations and reference to configuration options.

References¶

N/A

History¶

N/A

Audit tag in VM Metadata