cloudkitty/doc/source/user/rating/pyscripts.rst

PyScripts rating module

The PyScripts module allows you to create your own rating module. A script is supposed to process the given data and to set the different prices.

CAUTION: If you add several PyScripts, the order in which they will be executed is not guaranteed.

Custom module example

Price definitions

import decimal


# Price for each flavor. These are equivalent to hashmap field mappings.
flavors = {
    'm1.micro': decimal.Decimal(0.65),
    'm1.nano': decimal.Decimal(0.35),
    'm1.large': decimal.Decimal(2.67)
}

# Price per MB / GB for images and volumes. These are equivalent to
# hashmap service mappings.
image_mb_price = decimal.Decimal(0.002)
volume_gb_price = decimal.Decimal(0.35)

Price calculation functions

# These functions return the price of a service usage on a collect period.
# The price is always equivalent to the price per unit multiplied by
# the quantity.
def get_instance_price(item):
    if not item['metadata']['flavor_name'] in flavors:
        return 0
    else:
        return (decimal.Decimal(item['vol']['qty'])
               * flavors[item['metadata']['flavor_name']])

def get_image_price(item):
    if not item['vol']['qty']:
        return 0
    else:
        return decimal.Decimal(item['vol']['qty']) * image_mb_price


def get_volume_price(item):
    if not item['vol']['qty']:
        return 0
    else:
        return decimal.Decimal(item['vol']['qty']) * volume_gb_price

# Mapping each service to its price calculation function
services = {
    'instance': get_instance_price,
    'volume': get_volume_price,
    'image': get_image_price
}

Processing the data

def process(data):
    # The 'data' is a dictionary with the usage entries for each service
    # in a given period.
    usage_data = data['usage']

    for service_name, service_data in usage_data.items():
        # Do not calculate the price if the service has no
        # price calculation function
        if service_name in services.keys():
            # A service can have several items. For example,
            # each running instance is an item of the compute service
            for item in service_data:
                item['rating'] = {'price': services[service_name](item)}
    return data


# 'data' is passed as a global variable. The script is supposed to set the
# 'rating' element of each item in each service
data = process(data)

Using your Script for rating

Enabling the PyScripts module

To use your script for rating, you will need to enable the pyscripts module

$ cloudkitty module enable pyscripts
+-----------+---------+----------+
| Module    | Enabled | Priority |
+-----------+---------+----------+
| pyscripts | True    |        1 |
+-----------+---------+----------+

Adding the script to CloudKitty

Create the script and specify its name.

$ cloudkitty pyscript create my_awesome_script script.py
+-------------------+--------------------------------------+------------------------------------------+---------------------------------------+
| Name              | Script ID                            | Checksum                                 | Data                                  |
+-------------------+--------------------------------------+------------------------------------------+---------------------------------------+
| my_awesome_script | 78e1955a-4e7e-47e3-843c-524d8e6ad4c4 | 49e889018eb86b2035437ebb69093c0b6379f18c | from __future__ import print_function |
|                   |                                      |                                          | from cloudkitty import rating         |
|                   |                                      |                                          |                                       |
|                   |                                      |                                          | import decimal                        |
|                   |                                      |                                          |                                       |
|                   |                                      |                                          |         {...}                         |
|                   |                                      |                                          |                                       |
|                   |                                      |                                          | data = process(data)                  |
|                   |                                      |                                          |                                       |
+-------------------+--------------------------------------+------------------------------------------+---------------------------------------+