[openstack-dev] Is there a way to let nova schedule plugin fetch glance image metadata

Jay Pipes jaypipes at gmail.com
Thu Aug 14 01:29:36 UTC 2014

On 08/13/2014 08:31 PM, zhiwei wrote:
> Hi all,
> We wrote a nova schedule plugin that need to fetch image metadata by
> image_id, but encountered one thing, we did not have the glance context.
> Our solution is to configure OpenStack admin user and password to
> nova.conf, as you know this is not good.
> So, I want to ask if there are any other ways to do this?

You should not have to do a separate fetch of image metadata in a 
scheduler filter (which is what I believe you meant by "plugin" above?).

The filter object's host_passes() method has a filter_properties 
parameter that contains the request_spec, that in turn contains the 
image, which in turn contains the image "metadata". You can access it 
like so:

  def host_passes(self, host_state, filter_properties):
      request_spec = filter_properties['request_spec']
      image_info = request_spec['image']
      # Certain image attributes are accessed via top-level keys, like
      # size, disk_format, container_format and checksum
      image_size = image_info['size']
      # Other attributes can be accessed in the "properties" collection
      # of key/value pairs
      image_props =  image.get('properties', {})
      for key, value in image_props.items():
          # do something...


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