How to create a

libcloud driver from scratch

the NephoScale case

Libcloud

one library to rule them all

Supports many providers

What if your provider is not

supported?

● Clone

● Branch

● Write

● Test

● Merge back

Time to contribute

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

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

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

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

● Add your Provider class on libcloud/compute/types.py

Create driver fileCreate 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,

}

Writing the driverWe need to create a NodeDriver based driver

class NephoscaleNodeDriver(NodeDriver):"""Nephoscale node driver class"""

type = Provider.NEPHOSCALEapi_name = 'nephoscale'name = 'NephoScale'website = 'http://www.nephoscale.com'connectionCls = NephoscaleConnectionfeatures = {'create_node': ['ssh_key']}

def list_locations(self):...

Writing the Connection classand write a Connection class

class NephoscaleConnection(ConnectionUserAndKey):

host = API_HOSTresponseCls = 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

Writing the Response classResponse 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

Keep consistencyKeep 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

Testing the driverTest 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 ...>]

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

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 :)