Virtual Environments¶
Python virtual environments provide a mechanism for isolating python packages from the system site packages and other virtual environments. Kolla-ansible largely avoids this problem by deploying services in Docker containers, however some python dependencies must be installed both on the Ansible control host and the target hosts.
Ansible Control Host¶
The kolla-ansible python package and its dependencies may be installed in a python virtual environment on the Ansible control host. For example:
python3 -m venv /path/to/venv
source /path/to/venv/bin/activate
pip install -U pip
pip install kolla-ansible
pip install 'ansible<2.10'
deactivate
To use the virtual environment, it should first be activated:
source /path/to/venv/bin/activate
(venv) kolla-ansible --help
The virtual environment can be deactivated when necessary:
(venv) deactivate
Note that the use of a virtual environment on the Ansible control host does not imply that a virtual environment will be used for execution of Ansible modules on the target hosts.
Target Hosts¶
Ansible supports remote execution of modules in a python virtual environment
via the ansible_python_interpreter variable. This may be configured to be
the path to a python interpreter installed in a virtual environment. For
example:
ansible_python_interpreter: /path/to/venv/bin/python
Note that ansible_python_interpreter cannot be templated.
Kolla-ansible provides support for creating a python virtual environment on the
target hosts as part of the bootstrap-servers command. The path to the
virtualenv is configured via the virtualenv variable, and access to
site-packages is controlled via virtualenv_site_packages. Typically we
will need to enable use of system site-packages from within this virtualenv, to
support the use of modules such as yum, apt, and selinux, which are not
available on PyPI.
When executing kolla-ansible commands other than bootstrap-servers, the
variable ansible_python_interpreter should be set to the python interpreter
installed in virtualenv.
