Introduction

The ensure-tox is simple. It's a ansible playbook for zuul to check if tox is install. It looks for tox, and if it can't found it, it install it via pip into a virtual environment for the current user. It can be very useful sometimes and particulary with the usage of ensure_global_symlinks variable.

Example with a bug fix

Recently with a colleague Bernard Cafarelli, we've fixed the upstream CI for oslo-cookiecutter. It is a project that makes it easy to create an oslo project. The problem came from a test script that tried to run the tox command in the newly created project. The tox command was therefore not visible in the virtualenv created by the new project. I could not reproduce the bug in local, because couldn't immediately identify the problem because I had tox installed on my machine. In such cases, ensure-tox comes in handy. With the use of the ensure_global_symlinks variable which allows to make a symlink into /usr/local/bin path. It is needed in this case, because the script expects to have tox in a more standard location. The ensure-tox role was already in use by the parent job. So we just had to add the use of the variable to fix the bug.

Zuul jobs

The oslo-cookiecutter project uses zuul-jobs. It is a project that contains a set of Zuul jobs and Ansible roles suitable for use by any Zuul system. This allows in one of his projects to be able to reuse already existing job, role and not to reinvent the wheel. In our case, oslo-cookiecutter uses the tox job from the zuul-jobs project. The tox job uses the ensure-tox role, as can be seen here. The tox playbook first performs the ensure-tox role. As explained previously, ensure-tox makes sure that tox is installed. If it is not installed, the role will install it in a virtualenv using the ensure-pip-virtualenv role. In our case, we had to use the ensure_global_symlinks variable. To have the tox command accessible in a path of the $PATH which allowed us to correct our problem. The zuul-jobs project contains many roles and playbooks. I will write an article soon to introduce zuul and zuul-jobs.

Conclusion

In conclusion, ensure-tox is very useful to ensure that the job has tox installed and to have a symlink on the host system for scripts that need it. This is quite specific to OpenStack, because few projects use zuul. But if you are using zuul for a python project. I recommend you to use zuul-jobs and ensure-tox too. To enjoy a multitude of jobs, playbooks and ansible roles for zuul already written.