Tips and tricks¶
Ansible forks¶
The default MaxSessions setting for the OpenSSH Daemon is 10. Each Ansible fork makes use of a Session. By default, Ansible sets the number of forks to 5. However, you can increase the number of forks used in order to improve deployment performance in large environments.
Note that more than 10 forks will cause issues for any playbooks which use delegate_to or local_action in the tasks. It is recommended that the number of forks are not raised when executing against the Control Plane, as this is where delegation is most often used.
The number of forks used may be changed on a permanent basis by including the appropriate change to the ANSIBLE_FORKS in your .bashrc file. Alternatively it can be changed for a particular playbook execution by using the --forks CLI parameter. For example, the following executes the nova playbook against the control plane with 10 forks, then against the compute nodes with 50 forks.
# openstack-ansible --forks 10 os-nova-install.yml --limit compute_containers
# openstack-ansible --forks 50 os-nova-install.yml --limit compute_hosts
For more information about forks, please see the following references:
- OpenStack-Ansible Bug 1479812
- Ansible forks entry for ansible.cfg
- Ansible Performance Tuning
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