Cloned from launchpad blueprint https://blueprints.launchpad.net/ceilometer/+spec/improving-ceilometer-api-query-filtering.

Description:

The current version of Ceilometer API supports a simple query filtering option with a logical AND relation between the fields. This solution results in multiple calls towards the API, when there is a list of requested elements (samples or statistics). The API can be improved to support lists in the fields of a query filter. 

This improvement makes it possible to retrieve the samples of one or more meters for one or more resources in one API call and also supports to get the statistics of multiple resources with a single API request.

Specification URL (additional information):

https://wiki.openstack.org/wiki/File:Improving_Ceilometer_API_query_filtering.pdf