Apache Libcloud is a Python library which hides differences between different cloud provider APIs and allows you to manage different cloud resources through a unified and easy to use API. In this presentation we will go through the process of adding a new driver for a Cloud provider and submitting the changes but to the libcloud project

1. How to create a
libcloud driver from scratch
the NephoScale case

2. Libcloud
one library to rule them all

3. Supports many providers

4. What if your provider is not
supported?
● Clone
● Branch
● Write
● Test
● Merge back
Time to contribute

5. Tasklist
Backend actions
● list_nodes: list all nodes, including ip addresses, node state, metadata, etc
● list_images: list all the images the provider supports
● list_sizes: list different plans, providing data such as CPU, ram and disk size
● list_locations: List all available provider zones when applicable

6. Tasklist
Node actions
● create_node: create a node specifying it’s size, image, name and location
● deploy_node: create a node and deploy a public ssh key and optionally run a
deploy script
● reboot_node/shut down_node
● start_node/stop_node: start a stopped node, or stop a started one
● destroy_node: Delete the node

7. Getting ready
APIs and drivers
● Familiarize yourself with the provider API
● Choose a recent libcloud driver to base your code on
● Don’t break conventions. Do it the libcloud way

8. libcloud repo
Clone and extend
● Clone libcloud from https://github.com/apache/libcloud
● Libcloud drivers live in libcloud/compute/drivers
● They all inherit from the base driver at libcloud/compute/base.py
● Create your git branch
● Add your driver on libcloud/compute/providers.py

9. Create driver file
Create libcloud/compute/drivers/nephoscale.py
Specify the cloud provider API endpoint
API_HOST = 'api.nephoscale.com'
and the possible node states
NODE_STATE_MAP = {
'on': NodeState.RUNNING,
'off': NodeState.UNKNOWN,
'unknown': NodeState.UNKNOWN,
}

10. Writing the driver
We need to create a NodeDriver based driver
class NephoscaleNodeDriver(NodeDriver):
"""Nephoscale node driver class"""
type = Provider.NEPHOSCALE
api_name = 'nephoscale'
name = 'NephoScale'
website = 'http://www.nephoscale.com'
connectionCls = NephoscaleConnection
features = {'create_node': ['ssh_key']}
def list_locations(self):
...

11. Writing the Connection class
and write a Connection class
class NephoscaleConnection(ConnectionUserAndKey):
host = API_HOST
responseCls = NephoscaleResponse
def add_default_headers(self, headers):
user_b64 = base64.b64encode(b('%s:%s' % (self.user_id,
self.key)))
headers['Authorization'] = 'Basic %s' %
(user_b64.decode('utf-8'))
return headers

12. Writing the Response class
Response classes derive from JsonResponse or XMLRPCResponse
class NephoscaleResponse(JsonResponse):
"""Nephoscale API Response"""
def parse_error(self):
if self.status == httplib.UNAUTHORIZED:
raise InvalidCredsError('Authorization Failed')
if self.status == httplib.NOT_FOUND:
raise Exception("The resource you are looking for is not
found.")
return self.body

13. Keep consistency
Keep consistency, hardcode things when necessary
● Most of the times you don’t need to override deploy_node
● Libcloud standardizes things for providers (nodes/sizes/images/locations)
● When a provider does non-standard stuff, override
● Some providers don’t return enough details
● Hardcode only when necessary

14. Testing the driver
Test your driver often to make sure it works
user@user:~/dev/libcloud$ python
>>> from libcloud.compute.types import Provider
>>> from libcloud.compute.providers import get_driver
>>> driver = get_driver(Provider.NEPHOSCALE)
>>> conn = driver('user','correct_password')
>>> conn.list_nodes()
[<Node: uuid=e20bdbf7ef6890645f5b217e0bd2b5912b969cc1,
name=nepho-7, state=0, public_ips=['198.89.109.116'],
provider=NephoScale ...>]

15. Contributing to libcloud
Some ground rules and contribution workflow:
● Open a ticket on the tracker to notify any interested parties
● Write unit tests
● Follow code style (follow PEP8, use spaces for tabs, etc)
● Commit and open a pull request
● Wait for a review and make any changes pointed
● Create a patch with your changes and add it to your ticket

16. Thank you!
To check the driver in action, visit https://mist.io
More resources:
● https://libcloud.readthedocs.org/en/latest/development.html
● https://github.com/apache/libcloud
● https://libcloud.readthedocs.org/en/latest/developer_information.html
Special thanks to Tomaz, maintainer of libcloud and a very helpful guy :)