Open Stack

In Nova we are attempting to model[1] the glance image metadata and
properties using the Nova object model (now oslo.versionedobjects).

The one item I'm stuck on understanding is the 'locations' field
and more specifically the 'metadata' element in each location
entry


In the file glance/api/v2/images.py I can see this description
of the data format:

        'locations': {
            'type': 'array',
            'items': {
                'type': 'object',
                'properties': {
                    'url': {
                        'type': 'string',
                        'maxLength': 255,
                    },
                    'metadata': {
                        'type': 'object',
                    },
                },
                'required': ['url', 'metadata'],
            },
            'description': _('A set of URLs to access the image file kept in '
                             'external store'),


As you can see here, 'metadata' is just said to be of type 'object'.

Is there somewhere that actually describes what is valid contents
for this field ? Is it sufficient to assume the metadata will only
ever be a dict of strings, or can the metadata be a complex type
with arbitrarily nested data structures ?

Regards,
Daniel

[1] https://review.openstack.org/#/c/76234/
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