Python SDK

Introduction

This document provides a brief setup guide for advanced users who want to use the Python SDK. This document assumes a good understanding of Python.

Setting Up Clouds.yaml

Background

Clouds.yaml allows a user to provide their credentials for a project separate to their script. This is strongly recommended for a number of reasons:

  • Prevents hard-coded credentials leaking in the script
  • Allows sharing of scripts for support reasons and to colleagues
  • Able to quickly switch between a testing and production project

Setup

  • Navigate to Openstack
  • Go to API Access
  • On the right click the dropdown to download the clouds.yaml file, not the RC file
  • Move this file to ~/.config/openstack you may need to create the parent directory

Your YAML file will look similar to:

clouds:
  openstack:
    auth:
      auth_url: https://openstack.stfc.ac.uk:5000/v3
      username: ...
  • Modify the project name (default openstack) to something descriptive
  • Add your password under the auth directive

For the above example:

clouds:
  my_proj_name:
    auth:
      auth_url: https://openstack.stfc.ac.uk:5000/v3
      username: exampleUser
      password: examplePassword

Accessing Multiple Projects

This process can be repeated if you require access to multiple projects.

  • Switch project and download YAML for additional project
  • Append the contents of this downloaded file under the clouds directive

Here is an example of a file with multiple projects:

clouds:
  my_proj_name:
    auth:
      auth_url: https://openstack.stfc.ac.uk:5000/v3
      username: ...
      password: ...
  proj_dev:
    auth:
      auth_url: https://openstack.stfc.ac.uk:5000/v3
      username: ...
      password: ...
  proj_prod:
    auth:
      auth_url: https://openstack.stfc.ac.uk:5000/v3
      username: ...
      password: ...

This provides targets called proj_one, proj_dev and proj_prod. This is especially useful for testing a script against a development environment and performing a one-line change to switch to production.

Auth in Python Script

Openstack will automatically go to ~/.config/openstack/ to check for a clouds.yaml file (note: lower-case).

Using the above examples, we can easily point to the project named my_proj_name like so:

import openstack

conn = openstack.connect(cloud='my_proj_name', region_name='RegionOne')

# Print the list of servers to prove were connected as expected
s = conn.compute.servers()
print(s)

Using the Openstack SDK

Important

Because the Openstack SDK dynamically populates the connection object with available methods most IDE type suggestions will be internal low-level methods and should be ignored.

For example set_metadata is always available instead of set_x_metadata, where x is a Openstack service.

The Openstack SDK dynamically populates the connection object at runtime. This is because Openstack fundamentally is a modular install with different plugins enabled by operators.

Instead Openstack adds “Proxies” to a connection object to represent what is available on the service. The list of proxies can be printed at runtime with:

import openstack

connection = openstack.connect(cloud='my_proj_name', region_name='RegionOne')
print(dir(connection))

Documentation

The full list of proxies can be viewed here.

Worked Example - Set Server Metadata

The compute proxy allows us to manipulate compute resources (i.e. instances).

Looking at the documentation linked above there are methods to get a list of server instances and a method to set metadata. If we want to set an arbitrary field of FOO=BAR on all servers we can do so using the compute module:

import openstack

connection = openstack.connect(cloud='my_proj_name', region_name='RegionOne')
server_list = connection.compute.servers()
for server in server_list:
    connection.compute.set_server_metadata(server, FOO='BAR')