Ansible/Groups
From charlesreid1
When defining playbooks and hosts, it is useful to be able to deal with multiple hosts at once. This page covers basic group operations in Ansible.
Contents
Why groups?
Groups allow you to perform actions in bulk on different hosts. For example, you can define which servers are part of your production or testing environment, or you can define which of the servers in a given environment runs a database backend and which runs a web esrver frontend.
Default group: all
By default, the group all refers to all hosts listed in the host file. To run a command on all Ansible nodes (for example, date):
ansible all -a "date"
can also use pattern matching:
ansible '*' -a "date"
Ansible hosts file
The following ansible hosts file demonstrates an application of groups: labeling which machines are local vagrant machines, versus staging or production machines:
newhampshire.example.com maryland.example.com virginia.example.com newyork.example.com rhodeisland.example.com redblue.example.com orangered.example.com [vagrant] vagrant1 ansible_host=127.0.0.1 ansible_port=2222 vagrant2 ansible_host=127.0.0.1 ansible_port=2200 vagrant3 ansible_host=127.0.0.1 ansible_port=2201
More complex groupings
A more complex grouping example is given in the hosts file on the Ansible/Full Stack Playbook page.
In that scenario, Ansible was being used to deploy a web application that had a Django frontend, an http server, an Nginx load balancer, Celery task queue, RabbitMQ message queue (for celery backend), and Postgres (data store).
This was being deployed into 3 environments: vagrant (local testing), staging (testing), and production, with different configurations in each environment.
To organize this, the following hosts file was used:
[production] delaware.example.com georgia.example.com maryland.example.com newhampshire.example.com newjersey.example.com newyork.example.com northcarolina.example.com pennsylvania.example.com rhodeisland.example.com virginia.example.com [staging] redblue.example.com orangered.example.com [vagrant] vagrant1 ansible_host=127.0.0.1 ansible_port=2222 vagrant2 ansible_host=127.0.0.1 ansible_port=2200 vagrant3 ansible_host=127.0.0.1 ansible_port=2201 [lb] delaware.example.com [web] georgia.example.com newhampshire.example.com newjersey.example.com redblue.example.com vagrant1 [task] newyork.example.com northcarolina.example.com maryland.example.com redblue.example.com vagrant2 [rabbitmq] pennsylvania.example.com orangered.example.com vagrant3 [db] rhodeisland.example.com virginia.example.com orangered.example.com vagrant3
Groups of groups
Ansible allows defining groups composed of other groups.
To define which groups in the above example relate to Django (the web server and the task manager backend), we would say:
[django:children] web task
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