glance-specs/specs/kilo/metadata-multivalue-operators-support.rst

Support for multivalue operators in metadata catalog

https://blueprints.launchpad.net/glance/+spec/metadata-multivalue-operators-support

The metadata catalog provides data that user can pin to resources, e.g., flavors extra specs. These are used by scheduler to choose a host that satisfies the requirements provided in extra specs. Nova scheduler implements operators to combine multiple values under one key in extra specs: <or> and <all-in>. Unfortunately, the catalog does not provide which operator is suitable for a given property.

This blueprint aims at this problem by extending current jsons with suitable operators for each property.

Problem description

There is work being done in Horizon to provide support for multiple values for a single key in extra specs, however, Glance currently does not provide information about which operators are suitable for a given property. In compute-host-capabilities.json there is a property called cpu_info:features. Both operators - <all-in> and <or> can be used for this property. There are also properties like cpu_info:model where <or> is the only operator that should work.

Proposed change

To make end-user (e.g. Horizon) aware which operator can be used for a given property, this blueprint extends existing properties (and also properties inside objects) with a new section under key - "operators":

Currently an example property would be structured like this:

"cpu_info:features": {
    "title": "Features",
    "description": "Specifies CPU flags/features.",
    "type": "array",
    "items": {
        "type": "string",
        "enum": [
            "aes",
            "vme",
            "de"
        ]
    }
}

And after extension:

"cpu_info:features": {
    "title": "Features",
    "description": "Specifies CPU flags/features.",
    "operators": [
        "<or>",
        "<all-in>"
    ],
    "type": "array",
    "items": {
        "type": "string",
        "enum": [
            "aes",
            "vme",
            "de"
        ]
    }
}

The added section is:

"operators": [
    "<or>",
    "<all-in>"
]

This section will be optional, e.g., property that is integer does not need operator.

Also glance will not do any check on "operators" field. API consumer needs to take care to provide valid operators for nova scheduler. Currently there are three operators that are valid for nova scheduler and are usable with metadata definitions: <or>, <in> and <all-in>

Alternatives

None

Data model impact

This will not impact data model, because "operators" will be part of the blob stored in the json_schema column in the database table.

REST API impact

Example extended GET object body:

{
    "objects": [
        {
            "name": "object1",
            "namespace": "my-namespace",
            "description": "my-description",
            "properties": {
                "prop1": {
                    "title": "My Property",
                    "description": "More info here",
                    "operators": ["<all-in>"],
                    "type": "string",
                    "readonly": true
                }
            }
        }
    ],
    "first": "/v2/metadefs/objects?limit=1",
    "next": "/v2/metadefs/objects?marker=object1&limit=1",
    "schema": "/v2/schema/metadefs/objects"
}

Example POST/PUT body on objects:

{
    "name": "StorageQOS",
    "description": "Our available storage QOS.",
    "required": [
        "MyProperty"
    ],
    "properties": {
        "MyProperty": {
            "type": "string",
            "readonly": false,
            "description": "The My Property",
            "operators": ["<or>"],
            "enum": ["type1", "type2"]
        }
    }
}

Because "operators" field is optional API consumer needs to handle default value as it may be missing.

Security impact

None

Notifications impact

None

Other end user impact

None

Performance Impact

None

Other deployer impact

Upgrade of jsons or database in existing OpenStack installation will not be needed. "operators" section will not be mandatory so the installation can keep running without upgrade.

Also there is possibility that property/object will be missing operators even when the value has been added in the latest built-in metadata definition json templates, the upgrade process does not update existing database. Deployer needs to manually upgrade metadata definitions to the newest set.

Developer impact

None

Implementation

Assignee(s)

Primary assignee:

pawel-koniszewski

Other contributors:

None

Reviewers

Core reviewer(s):

lzy-dev

Work Items

• Extend existing metadata jsons with operators section.
• Extend API json schema with new option

Dependencies

Horizon blueprint that depends on this blueprint: https://blueprints.launchpad.net/horizon/+spec/metadata-widget-multivalue-selection

Nova blueprint that this blueprint depends on: https://blueprints.launchpad.net/nova/+spec/add-all-in-list-operator-to-extra-spec-ops

Testing

Current unit tests and functional tests will be extended to make sure that the new section is returned and that it is correct. Tests will also ensure that the operators part is optional.

Documentation Impact

The new attribute needs to be documented.

References

None