Sending pull requests

Do you want to contribute to the bootstrap-vz project? Nice! Here is the basic workflow:

  • Read the development guidelines
  • Fork this repository.
  • Make any changes you want/need.
  • Check the coding style of your changes using tox by running tox -e flake8 and fix any warnings that may appear. This check will be repeated by Travis CI once you send a pull request, so it’s better if you check this beforehand.
  • If the change is significant (e.g. a new plugin, manifest setting or security fix) add your name and contribution to the changelog.
  • Commit your changes.
  • Squash the commits if needed. For instance, it is fine if you have multiple commits describing atomic units of work, but there’s no reason to have many little commits just because of corrected typos.
  • Push to your fork, preferably on a topic branch.
  • Send a pull request to the master branch.

Please try to be very descriptive about your changes when you write a pull request, stating what it does, why it is needed, which use cases this change covers, etc. You may be asked to rebase your work on the current branch state, so it can be merged cleanly. If you push a new commit to your pull request you will have to add a new comment to the PR, provided that you want us notified. Github will otherwise not send a notification.

Be aware that your modifications need to be properly documented. Please take a look at the documentation section to see how to do that.

Happy hacking! :-)

Development guidelines

The following guidelines should serve as general advice when developing providers or plugins for bootstrap-vz. Keep in mind that these guidelines are not rules , they are advice on how to better add value to the bootstrap-vz codebase.

The manifest should always fully describe the resulting image

The outcome of a bootstrapping process should never depend on settings specified elsewhere.

This allows others to easily reproduce any setup other people are running and makes it possible to share manifests. The official debian EC2 images for example can be reproduced using the manifests available in the manifest directory of bootstrap-vz.

The bootstrapper should always be able to run fully unattended

For end users, this guideline minimizes the risk of errors. Any required input would also be in direct conflict with the previous guideline that the manifest should always fully describe the resulting image.

Additionally developers may have to run the bootstrap process multiple times though, any prompts in the middle of that process may significantly slow down the development speed.

The bootstrapper should only need as much setup as the manifest requires

Having to shuffle specific paths on the host into place (e.g. /target has to be created manually) to get the bootstrapper running is going to increase the rate of errors made by users. Aim for minimal setup.

Exceptions are of course things such as the path to the VirtualBox Guest Additions ISO or tools like parted that need to be installed on the host.

Roll complexity into which tasks are added to the tasklist

If a run() function checks whether it should do any work or simply be skipped, consider doing that check in resolve_tasks() instead and avoid adding that task altogether. This allows people looking at the tasklist in the logfile to determine what work has been performed.

If a task says it will modify a file but then bails , a developer may get confused when looking at that file after bootstrapping. He could conclude that the file has either been overwritten or that the search & replace does not work correctly.

Control flow should be directed from the task graph

Avoid creating complicated run() functions. If necessary, split up a function into two semantically separate tasks.

This allows other tasks to interleave with the control-flow and add extended functionality (e.g. because volume creation and mounting are two separate tasks, the prebootstrapped plugin can replace the volume creation task with a task of its own that creates a volume from a snapshot instead, but still reuse the mount task).

Task classes should be treated as decorated run() functions

Tasks should not have any state, thats what the BootstrapInformation object is for.

Only add stuff to the BootstrapInformation object when really necessary

This is mainly to avoid clutter.

Use a json-schema to check for allowed settings

The json-schema may be verbose but it keeps the bulk of check work outside the python code, which is a big plus when it comes to readability. This only applies as long as the checks are simple. You can of course fall back to doing the check in python when that solution is considerably less complex.

When invoking external programs, use long options whenever possible

This makes the commands a lot easier to understand, since the option names usually hint at what they do.

When invoking external programs, don’t use full paths, rely on $PATH

This increases robustness when executable locations change. Example: Use log_call(['wget', ...]) instead of log_call(['/usr/bin/wget', ...]).

Coding style

bootstrap-vz is coded to comply closely with the PEP8 style guidelines. There however a few exceptions:

  • Max line length is 110 chars, not 80.
  • Multiple assignments may be aligned with spaces so that the = match vertically.
  • Ignore E221 & E241: Alignment of assignments
  • Ignore E501: The max line length is not 80 characters

The codebase can be checked for any violations quite easily, since those rules are already specified in the tox configuration file.

tox -e flake8


When developing a provider or plugin, make sure to update/create the README.rst located in provider/plugin folder. Any links to other rst files should be relative and work, when viewed on github. For information on how to build the documentation and how the various parts fit together, refer to the documentation about the documentation :-)