Comment 2 for bug 1719770

Including the stats call:

@pick_context_manager_reader
def compute_node_statistics(context):
    """Compute statistics over all compute nodes."""

    # TODO(sbauza): Remove the service_id filter in a later release
    # once we are sure that all compute nodes report the host field
    _filter = or_(models.Service.host == models.ComputeNode.host,
                  models.Service.id == models.ComputeNode.service_id)

    result = model_query(context,
                         models.ComputeNode, (
                             func.count(models.ComputeNode.id),
                             func.sum(models.ComputeNode.vcpus),
                             func.sum(models.ComputeNode.memory_mb),
                             func.sum(models.ComputeNode.local_gb),
                             func.sum(models.ComputeNode.vcpus_used),
                             func.sum(models.ComputeNode.memory_mb_used),
                             func.sum(models.ComputeNode.local_gb_used),
                             func.sum(models.ComputeNode.free_ram_mb),
                             func.sum(models.ComputeNode.free_disk_gb),
                             func.sum(models.ComputeNode.current_workload),
                             func.sum(models.ComputeNode.running_vms),
                             func.sum(models.ComputeNode.disk_available_least),
                         ), read_deleted="no").\
                         filter(models.Service.disabled == false()).\
                         filter(models.Service.binary == "nova-compute").\
                         filter(_filter).\
                         first()

    # Build a dict of the info--making no assumptions about result
    fields = ('count', 'vcpus', 'memory_mb', 'local_gb', 'vcpus_used',
              'memory_mb_used', 'local_gb_used', 'free_ram_mb', 'free_disk_gb',
              'current_workload', 'running_vms', 'disk_available_least')
    return {field: int(result[idx] or 0)
            for idx, field in enumerate(fields)}