Ansible

Ansible is a extra-simple Python API for doing 'remote things' over SSH.

While Func, which I co-wrote, aspired to avoid using SSH and have it's own daemon infrastructure, Ansible aspires to be quite different and more minimal, but still able to grow more modularly over time.

Principles

* Dead simple setup
* No server or client daemons, uses existing SSHd
* Only SSH keys are allowed for authentication
* usage of ssh-agent is more or less required
* plugins can be written in ANY language
* as with Func, API usage is an equal citizen to CLI usage
* use Python's multiprocessing capabilities to emulate Func's forkbomb logic

Requirements

For the server the tool is running from, only:

* python 2.6 -- or a backport of the multiprocessing module
* paramiko

Inventory file

The default inventory file (-H) is ~/.ansible_hosts and is a list of all hostnames to target with ansible, one per line. These can be hostnames or IPs

This list is further filtered by the pattern wildcard (-P) to target specific hosts.

Comamnd line usage example

Run a module by name with arguments

ssh-agent bash ssh-add ~/.ssh/id_rsa.pub ansible -p "*.example.com" -m modName -a "arg1 arg2"

API Example

The API is simple and returns basic datastructures.

import ansible runner = ansible.Runner(command='inventory', host_list=['xyz.example.com', '...']) data = runner.run()

{ 'xyz.example.com' : [ 'any kind of datastructure is returnable' ], 'foo.example.com' : None, # failed to connect, ... }

Additional options to runner include the number of forks, hostname exclusion pattern, library path, and so on. Read the source, it's not complicated.

Parallelism

Specify the number of forks to use, to run things in greater parallelism.

ansible -f 10 "*.example.com" -m modName -a "arg1 arg2"

10 forks. The default is 3. 5 is right out.

Bundled Modules

See the example library for modules, they can be written in any language and simply return JSON to stdout. The path to your ansible library is specified with the "-L" flag should you wish to use a different location than "~/ansible". There is potential for a sizeable community to build up around the library scripts.

Features not supported from Func (yet?)

• Delegation for treeish topologies
• Asynchronous modes for polling long running operations

Future plans

• Dead-simple declarative configuration management using a runbook style recipe file
• facts engine, including exec'ing facter if present

Author

Michael DeHaan michael.dehaan@gmail.com

http://michaeldehaan.net/