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Simplified, container-friendly provisioning

Project Description

Note

For the latest source, please visit the Bitbucket repository

Stuffer - simplified, container-friendly provisioning

Stuffer is a provisioning tool designed to be simple, and to be used in simple scenarios.

Documentation is hosted on http://stuffer.readthedocs.io.

Project status

Alpha. Raw but usable. The documentation is sparse. In some cases, it describes intentions, some of which are not implemented.

Use cases

Stuffer is primarily intended to be used for provisioing container images, Docker in particular. As a secondary use case, it can be used to provision non-production machines, e.g. developer machines.

More complex provisioning tools, such as Puppet, Chef, and Ansible, are intended for bringing a machine in an arbitrary state to a desired state. This turns out not to be possible in practice, and production machines manages with such tools tend to suffer from outdated dependency packages, etc.

Stuffer is primarily intended for building a machine from scratch to the desired state. Since the initial state is known, much of the complexity of existing provisioning tools is unnecessary. For example, during an image build, running services need not be considered or restarted.

Overview

Stuffer uses a Python embedded DSL for specifying provisioning directives. It is typically invoked with one or more command arguments on the command line, e.g.:

stuffer 'apt.Install("mercurial")'

Multiple arguments are concatenated into a multiple line Python recipe:

stuffer \
  'for pkg in "mercurial", "gradle", "python-nose":' \
  '  print("Installing", pkg)' \
  '  apt.Install(pkg)'

Reused recipes can be factored out into Python modules for easier reuse:

stuffer 'development.Tools()'

In development.py:

from stuffer.core import Group

class Tools(Group):
  def children(self):
    return [apt.Install(p) for p in "mercurial", "gradle", "python-nose"]

Stuffer comes with builtin knowledge of Docker best practices, which it can enforce for you:

Dockerfile:
  FROM phusion/baseimage:0.9.18

  RUN stuffer 'docker.Prologue()'  # Verifies e.g. that base image is sound.

  RUN stuffer ... # Install stuff

  RUN stuffer 'docker.Epilogue()'  # Cleans temporary files, warns about known anti-patterns in the statements above.

Design goals

Stuffer design gives priority to:

  • Simplicity of use. No knowledge about the tool should be required in order to use it for simple scenarios by copying examples. Some simplicity in the implementation is sacrificed in order to make the usage interface simple. Actions are named similarly to the corresponding shell commands.
  • Transparency. Whenever reasonable, actions are translated to shell commands. All actions are logged.
  • Ease of reuse. It should be simple to extract commands from snippets and convert them to reusable modules without a rewrite.
  • Docker cache friendliness. Images built with similar commands should be able to share a prefix of commands in order to benefit from Docker image caching.
  • No dislike factors. Provisioning tools tend to be loved and/or hated by users, for various reasons. There might be no reason to be passionately enamoured with stuffer, but there should be no reason to have a strong dislike for it, given that you approve of Python and Docker.
  • Ease of debugging. Debugging stuffer recipes should be as easy as debugging standard Python programs.
  • Avoid reinventing wheels. Use existing Python modules or external tools for tasks that have already been solved. Give priority to reusing existing code over minimising dependencies. In particular, use Python 3 and click to save boilerplate.

Moreover, the project model is design to facilitate sharing and reuse of code between users, see below.

DSL

The DSL is designed to be comprehensible by readers that are not familiar with stuffer. For example, the command apt.Install(“mypack”) runs “apt-get install mypack”. There is a balance between convenience and comprehensibility, and stuffer in most cases shuns magic that would create convenience in preference for more understandable code.

The DSL is also designed to make it easy to do things that are correct and work well with containers, and difficult to do things that do not harmonise with containers.

The DSL is designed to be tool friendly (with IntelliJ/PyCharm and pylint in particular), both for writing stuff files and for working on stuffer itself. For example, all imports are explicitly declared in order to make structure visible to tools.

Python conventions are used for naming, i.e. CamelCase classes and snake_case functions.

Collaboration model

Users are allowed to put recipes under sites/ for others to get inspired. This model may not scale, but as long as the number of users is small, there is value in sharing and showing each other code snippets, in order to extract pieces of common value.

Snippets worth reuse can be put under stuffer/contrib/. Files under stuffer/contrib are expected to be maintained by the contributor.

Routines for installing third-party software should also go under stuffer/contrib.

Contributing

New code should be covered with integration tests. Avoid unit tests - since the purpose of stuffer is integration, there is little value testing scenarios that are not authentic. Strive to figure out a way to test functionality with Docker containers.

In order to run the test suite, run tox in the project root directory. The continuous integration build also bulds the documentation (tox -e docs) and performs a distribution build (tox -e dist). See shippable.yml for the exact commands.

When tests pass, fork https://bitbucket.org/mapflat/stuffer, push your code to the fork and create a pull request.

Build and release

Continuous integration builds are run with Shippable. Shippable builds a release package for every merge or push to master branch and uploads it to https://pypi.python.org. In order to make a new release, you must update the version number in setup.py before merging to master.

Deployment

Install the latest version with pip3 install stuffer, depending on the default python version in your environment.

In order to create an installable distribution package from the source directory, run ./setup.py sdist from the project root directory. Install with pip3 install dist/stuffer-*.tar.gz.

Known issues

There is a name clash between the click command line parser library and a Ubuntu python package for handling the click packaging format. Hence, you might run into trouble if you have the former installed on your machine, or in the Docker images that you wish to build. At this point, you can either solv it by removin the conflicting package, or by installing stuffer in a virtual environment (virtualenv).

Release History

Release History

This version
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0.0.10

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0.0.9

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0.0.8

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0.0.7

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0.0.6

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0.0.5

History Node

0.0.1

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File Name & Checksum SHA256 Checksum Help Version File Type Upload Date
stuffer-0.0.10-py3-none-any.whl (21.2 kB) Copy SHA256 Checksum SHA256 py3 Wheel Jul 10, 2017
stuffer-0.0.10.tar.gz (11.6 kB) Copy SHA256 Checksum SHA256 Source Jul 10, 2017

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