It's been a while since the 0.13 release of python-gitlab. For the 0.14 release I spent some time writing code examples to make the first steps of using the API easier. All the objects are not yet documented, but since there's been a lot of new features and some bug fixes I wanted to get things out there.

python-gitlab is a python package and a gitlab CLI to interact with the Gitlab API.

To install the 0.14 version using pip:

pip install --upgrade python-gitlab

Download the tarballs on pypi: https://pypi.python.org/pypi/python-gitlab

Documentation is available on read the docs: http://python-gitlab.readthedocs.io/en/stable/

Report bugs and send pull request on github, contributions are very welcome: http://github.com/gpocentek/python-gitlab


The problem

Ansible playbooks that can deploy applications in multiple contexts (for example a 1-node setup for tests, and multi-node setup with HA for production) might have to deal with rather complex variable definitions. The templating system provided by Ansible is a great help, but it can be difficult and very verbose to use it sometimes.

I recently had to solve a simple problem. Depending on the installation node of the HAProxy load balancer, the 15 balanced services had to listen on different ports to avoid conflicts.

One solution

Instead of computing the selected port using the template system, I chose to develop a module that would set the chosen ports as a fact on every target. The module is called once at the beginning of the playbook, and the ports are available as a variable in all the tasks.

The module

The module takes one mandatory boolean argument, with_haproxy.

The implementation looks like this (library/get_ports.py):

INTERNAL = {
    'service1': 11001,
    'service2': 11002
}
PUBLIC = {
    'service1': 1001,
    'service2': 1002
}

def main():
    module = AnsibleModule(
        argument_spec = dict(
            with_haproxy = dict(type='bool', required=True)
        )
    )

    with_haproxy = module.params['with_haproxy']
    ports = {'public': PUBLIC}
    ports['internal'] = INTERNAL if with_haproxy else PUBLIC

    module.exit_json(changed=False, result="success",
                     ansible_facts={'ports': ports})

    from ansible.module_utils.basic import *
    main()

The ansible_facts argument name is important, it will tell ansible to register this variable as a fact, so you don't need to use the register attribute in your task.

The ports dict holds the ports information for public and internal access. The ports.internal dict is used to configure the services ports. If HAProxy is used, they have custom (INTERNAL) ports to avoid conflicting with HAProxy. Otherwise they use the official (PUBLIC) port.

The playbook

To register the facts, the first task of the playbook looks like this:

- name: Register ports
  local_action:
    module: get_ports
    with_haproxy: true|false

- debug: var=ports.internal.service1
- debug: var=ports.internal.service2

The local_action module avoids a useless connection to the targets.

Note

If you have not written modules for Ansible yet, have a look at the tutorial. They can be written in any language, although using Python makes things a lot easier.