Ansible (software)
| Developer(s) | Michael DeHaan |
|---|---|
| Initial release | February 20, 2012 |
| Stable release | 1.9.0.1 / 26 March 2015 |
| Written in | Python |
| Operating system | GNU/Linux, Unix-like, Windows |
| Type | Configuration management, Orchestration engine |
| License | GNU General Public License |
| Website |
www |
Ansible is an open-source software platform for configuring and managing computers. It combines multi-node software deployment, ad hoc task execution, and configuration management.[1] It manages nodes over SSH or PowerShell and requires Python (2.4 or later) [2] to be installed on them. Modules work over JSON and standard output and can be written in any programming language. The system uses YAML to express reusable descriptions of systems.[3]
The platform was created by Michael DeHaan, the author of the provisioning server application Cobbler and co-author of the Func framework for remote administration.[4] It is included as part of the Fedora distribution of Linux, owned by Red Hat inc., and is also available for Red Hat Enterprise Linux, CentOS and Scientific Linux via Extra Packages for Enterprise Linux (EPEL) as well as other operating systems.[5] Ansible is commercially supported and sponsored by Ansible, Inc.[6]
It was named "Ansible" after the fictional instantaneous hyperspace communication system featured in Orson Scott Card's Ender's Game,[7] and originally invented by Ursula K. Le Guin for her 1966 novel Rocannon's World.
Architecture
As with most configuration management software, Ansible distinguishes two types of servers: controlling machines and nodes. First, there is a single controlling machine which is where orchestration begins. Nodes are managed by a controlling machine over SSH. The controlling machine describes the location of nodes through its inventory.
To orchestrate nodes, Ansible deploys modules to nodes over SSH. Modules are temporarily stored in the nodes and communicate with the controlling machine through a JSON protocol over the standard output.[8] When Ansible is not managing nodes, it does not consume resources because no daemons or programs are executing for Ansible in the background.[9]
In contrast with popular configuration management software such as Chef, Puppet and CFEngine, Ansible uses an agentless architecture.[9] With an agent-based architecture, nodes must have a locally installed daemon that communicates with a controlling machine. With an agentless architecture, nodes are not required to install and run background daemons to connect with a controlling machine. This type of architecture reduces the overhead on the network by preventing the nodes from polling the controlling machine.[9]
Design goals
The design goals of Ansible[8] include:
- Minimal in nature. Management systems should not impose additional dependencies on the environment.[9]
- Consistent.
- Secure. Ansible does not deploy vulnerable agents to nodes. Only OpenSSH is required, which is already critically tested.[9]
- Highly reliable. The idempotent resource model is applied to deployment to prevent side-effects from re-running scripts.[1]
- Low learning curve. Playbooks use an easy and descriptive language based on YAML.
Modules
Modules are considered to be the units of work in Ansible. Each module is mostly standalone and can be written in a standard scripting language such as Python, Perl, Ruby, bash, etc. One of the guiding properties of modules is idempotency which means that no operations are performed once an operation has placed a system into a desired state.[8]
Inventory configuration
The Inventory is a description of the nodes that can be accessed by Ansible.
By default, the Inventory is described by a configuration file, in INI format, whose
default location is in /etc/ansible/hosts. The configuration file
lists either the IP address or hostname of each node that is accessible by
Ansible. In addition, nodes can be assigned to groups.[10]
An example configuration file:
192.168.6.1 [webservers] foo.example.com bar.example.com
This configuration file specifies three nodes. The first node is specified by
an IP address and the latter two nodes are specified by hostnames.
Additionally, the latter two nodes are grouped under the
webservers group name.
Ansible can also be pointed towards a custom "Dynamic Inventory" script which can pull data from any different software system.
Playbooks
Playbooks express configurations, deployment, and orchestration in Ansible.[11] The Playbook format is YAML. Each Playbook maps a group of hosts to a set of roles. Each role is represented by calls to Ansible call tasks.
Platform support
Control machines must have Python 2.6. Operating systems supported on control machines include most Linux and Unix distributions such as Red Hat, Debian, CentOS, OS X, and BSD, among others.
Managed nodes must have Python 2.4 or later. For managed nodes with Python 2.5
or earlier, the python-simplejson package is also
required.[12] Ansible can manage Windows[13] nodes starting from version 1.7.[12]
Cloud integration
Ansible can deploy to virtualization environments and public and private cloud environments including VMWare, OpenStack, AWS, Eucalyptus Cloud, KVM, and CloudStack.[8]
Big data integration
Ansible can deploy big data, storage and analytics environments including Hadoop, Riak, and Aerospike. The problem addressed by Ansible in these environments includes the management of resource consumption of each node. Specifically, big data, storage, and analytics environments intend to be resource efficient by wasting as little CPU time and memory as possible. Furthermore, Ansible provides monitoring capabilities that measure quantities such as CPU resources available which can help in the supervision of these nodes.[8]
Users
Ansible is used by Atlassian, Twitter, OneKingsLane, Evernote, TrunkClub, edX, hootsuite, GoPro, NewsCred and Care.com, among others.[14]
See also
References
- ↑ 1.0 1.1 "Achieving Rolling Updates and Continuous Deployment with Zero Downtime" (PDF).
- ↑ "Getting Started | Ansible". 2014-02-06.
- ↑ "Ansible: CM, Deployment, and Ad Hoc Task Execution All in One". DZone. 18 April 2012.
- ↑ "An Interview with Ansible Author Michael DeHaan". Colo and Cloud. 17 April 2012.
- ↑ "Ansible". Linux Packages Search.
- ↑ "Ansible". Ansible. Retrieved 9 March 2013.
- ↑ "Ansible FAQ".
- ↑ 8.0 8.1 8.2 8.3 8.4 "Ansible in Depth" (PDF).
- ↑ 9.0 9.1 9.2 9.3 9.4 "The Benefits of Agentless Architecture" (PDF).
- ↑ "Inventory | Ansible". 2014-04-26.
- ↑ "Playbooks | Ansible". 2014-04-26.
- ↑ 12.0 12.1 "Getting | Started". 2014-02-06.
- ↑ "Ansible 1.7 is released - Windows beta and more!". 2014-08-07.
- ↑ "Ansible is Simple IT Automation". 2014-04-26.