Modularity

Summary

Modularity (formerly, Modularization) is an ongoing initiative in Fedora to resolve the issue of divergent, occasionally conflicting lifecycles of different components. A module provides functionality (for instance a web server) and includes well-integrated and -tested components (for instance Apache httpd and the libraries on which it depends). It can be deployed into production in various ways, for instance as "classic" RPM packages or a container image, and is updated as a whole. Different modules can emphasize new features, stability, security, etc. differently.

Modularity subsections

• FAQ
• Getting Started
• Development
• Architecture

Background

The modularity objective was introduced to Fedora as a next step to the Fedora Rings proposal. We have been through many discussions on this subject and false starts on development work. We are trying to capture what the project is and will be in this wiki page. By way of introduction it is probably useful to try to define what we mean by "modularity."

The first step in this project was the Fedora Rings proposal. The original proposal being adopted has resulted in a number of tangible changes with varying levels of success:

• The split into the three editions
• The creation of several Working Groups to further some of these goals, namely Envs & Stacks and Base
• The creation and implementation of COPR.

However, looking at the original Fedora Rings proposal, it seems that the simple metaphor of concentric rings doesn't actually work very well for our increasingly messy open source software world. For example, there ends up being a huge number of rings to represent the whole spectrum of "quality" for modules. Also, the rings have problems representing orthogonal concerns like build dependencies, not to mention docs and tests. As a result, much of this discussion has stagnated trying to force fit the solution to the problem.

Motivations

• Fedora Rings talk: for slides or Video
• 2014 Fedora Rings update: slides
• A recent talk at FOSDEM 2016 and reprised at devconf.cz 2016 and slides
• Concrete example: can we update docker at different speeds in, say, Fedora Atomic vs. Fedora Server? Mailing list thread at projectatomic.io
• A talk by Colin Charles at FOSDEM 2016: "Distributions from the view of a package"; slides, unfortunately, no video.

Context

The Modularity topic has a number of perspectives and goals, as a result, we will be posting a series of articles to the community blog outlining the problems and benefits. Hopefully, separating the perspectives in to dedicated posts will make the overall story clearer. As the articles are published, we will provide links to them below.

Conversations

• Mo Duffy wrote up a recap of a server-wg meeting
• Matthew Miller posted to devel asking for a minimum viable demo of security scanning for a container-based module

Blog Posts

• Modularity Use Case: Application Independence
• Why modularization matters to Sys Admins

LWN Article

• Modularizing Fedora (March 16, 2016) — Good overview from an outside-the-project perspective. (n.b. paywalled until March 31st)

Summary of Work

• The Aleph proposal made in the E&S Working Group allows for different levels of package quality.
• A playground proposal which would combine certain COPR repositories in to one unified repository for packages that are considered more production quality than COPR but not strong enough for inclusion in the main repos. A Change was also proposed.
• See Modularity_Working_Group#Tooling Prototypes for some existing tooling prototypes.

Fedora Objectives

Fedora has focused efforts related to the Modularization project through a number of Objectives.

• Objectives/Fedora Editions, Phase 2
  • Summary: Take the initial Server/Workstation/Cloud split from Fedora 21 from an experiment into solid production. Increase autonomy from FESCo and improve targeted outreach.
  • Objective Lead: Stephen Gallagher
  • Timeframe: F22 and F23 releases, ending shortly after Flock 2015.

• Objectives/Fedora Modularization, Requirements Phase
  • Summary: Requirements-gathering from stakeholders for "Rings" aspect of Fedora.next
  • Objective Lead: Langdon White
  • Timeframe: F23 release - Flock; will be updated with subsequent phase

• Objectives/Fedora Modularization, Prototype Phase
  • Summary: The goal of this phase is to deliver a functional implementation of modular Fedora.
  • Objective Lead: Langdon White
  • Timeframe: F25 release, with demo at conferences in early 2017.

How to Get Involved

See Modularity WG and Getting involved.