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Optimizing Ansible Performance

Introduction​

Ansible is a powerful automation tool, but like any tool, its performance can be significantly affected by how it's used. This article aims to provide some practical tips and best practices to optimize Ansible performance for your tasks, making your automation faster and more efficient.

Understanding Ansible Performance​

Before diving into the optimization techniques, it's essential to understand how Ansible works. Ansible uses a push-based model where it connects to your nodes and pushes out small programs, called "Ansible modules". These modules are executed, and the results are removed when finished. The transportation of these modules, their execution, and the return of results are areas where optimization can take place.

Strategy​

Ansible uses strategies to decide how to execute the plays. By default, it uses the linear strategy, which works on a fixed number of hosts at a time. The free strategy allows each host to run until the end of the play as fast as it can. In general, using the free strategy can result in faster execution times for your plays. 

- hosts: all
  strategy: free
  tasks:
    - name: execute tasks as fast as possible
      ping:

Forks​

By default, Ansible communicates with five machines concurrently. This number is called forks. If you're managing a large number of machines, increasing the forks value can speed up the process.

ansible-playbook -i inventory.ini my_playbook.yml -f 10

In the above example, the -f 10 flag indicates that Ansible should use 10 forks, allowing it to communicate with ten machines concurrently.

Fact Caching​

By default, Ansible gathers facts about the systems it manages before executing any tasks. If your tasks don't rely on up-to-date facts, you can cache them to speed up playbook execution. You can enable fact caching in your ansible.cfg file.

[defaults]
fact_caching = jsonfile
fact_caching_connection = /tmp/ansible_fact_cache
fact_caching_timeout = 86400

Task Delegation​

Sometimes, not all tasks need to be performed on all hosts. You may have tasks that can be executed on a single host, with the results shared amongst all the others. In such cases, you can use delegate_to to specify the host to execute the task.

- hosts: all
  tasks:
    - name: execute task on a single host
      command: /opt/my_app/my_script.sh
      delegate_to: host1.example.com

Limiting Hosts​

When running your playbook, you can limit the hosts that you are managing by using the --limit option. This can speed up execution when you're only interested in a subset of hosts.

ansible-playbook -i inventory.ini my_playbook.yml --limit 'host1.example.com'

Mitogen for Ansible​

Mitogen is a library that can be used to boost Ansible's performance. It achieves this by establishing a Python interpreter on the remote system and reusing it across tasks. To use Mitogen, download it and update your ansible.cfg file.

[defaults]
strategy_plugins = /path/to/mitogen/ansible_mitogen/plugins/strategy
strategy = mitogen_linear

Conclusion​

Performance optimization is an ongoing journey, and these tips should give you a good starting point for improving Ansible's speed. A well-optimized Ansible setup can significantly reduce execution time, leading to more efficient and effective automation.

Remember, the best practices for optimizing Ansible performance depend on your specific use case, so remember to test these suggestions in your environment. Happy automating!