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DRAFT: MongoDB Documentation Build System Specification

This document address the operation and design of a build system for produce the MongoDB Manual, the content of which resides in this repository.

Requirements

The build system needs:

  • To build from and maintain multiple releases of documentation independently of each-other.

    For example, it must be able to build and publish changes to the documentation for 2.1.x without publishing changes to 1.8.x.

    We should assume that the documentation for each release is a branch of a git repository, but that there may be will be some topic branches in this that won't host release versions.

  • That every commit, push, or update to the repository will not result in documentation publication. Because:

    • Every change to the documentations need to be reviewed and/or edited (a la code review; commits may also merit backporting to other branches) publishing.
    • Changes to documentation need to be tested locally to ensure that modifications don't create cross referencing problems or produce other build errors. For right now this is a manual process.
  • That, at least for one non-default, "hyperalpha" branch (master(?)), commits and/or pushes do trigger a build of some sort. This might be for a separate repository, the implementation is not particularly important.

  • The system must make it difficult to publish the docs in a broken state and that changes to the documentation are reviewed and vetted by the documentation team and relevant engineers before publication. Ideally this means the documentation build system will operate locally.

Workflow

Branches

(Subject to change, depending on when the documentation becomes more feature complete and on the MongoDB release schedule. Additionally, the number of branches and the uses of these branches should remain independent of the build system. This will probably change over time.)

The following branches track documentation states that do not correspond directly to a specific release of the server.

  • "current" (tracks "master" in the server repository, and is the main page for the notional "docs.mongodb.org" site.)
  • "hyperalpha" (is always rebuilt following commits and provides a tighter feedback loop for documentation contributors outside of the docs team and without a more keen sense of restructured text.)

The following branches track specific versioned release series of the database server.

  • 1.8-release
  • 2.0-release
  • latest-development (i.e. odd numbered releases.)

Largely, the branching strategy of the documentation will mirror (albeit more simply) the branching strategy of the server. Latest development and current might end up being the same. The exact policy might be hard here.

Additional thoughts:

  • The documentation template itself will provide an interface for switching between branched version.
  • It would be possible to use this basic layout to underpin different versions of the docs for translation needs.
  • Not every branch in the repository is published. There will be some topic, testing, and related branches with various duration as needed that won't be published. A list of published branches needs to be specified in a text file (or similar) in or near the build system.

Public Contributions

(Where public equals, anyone outside of the docs team, including 10gen engineers, other staff, and the community.)

The "main" repository on github will have a master branch that tracks the "hyperalpha" branch. This is rebuilt regularly and is easily accessible on the web but is excluded from robots.txt and has no-follow links to avoid defusing the search results. Contributions come in the form of edits directly on github, or pull requests.

Then, with editing and review, changes from hyperalpha are batched and reviewed and merged into the "current" branch. The next section covers how the docs team works internally, and what happens to the "current" branch.

Documentation Workflow

(This describes the publication process, and how the docs team works internally.)

The "current" branch is published (on average) several times a week as needed, with changes reviewed by the docs team and engineers as needed and appropriate, and incorporates both ongoing documentation development and the "hyperalpha" branch. This is the main documentation visible on the website.

Releases branch from "current," around the release of the server, and after release only receive (mostly) minor patches and updates after release.

Alternately, the "main documentation" for "docs.mongodb.org" can point to the latest stable/production (even numbered) release.

To facilitate review and working builds, every commit or "push" to the current branch (or any other branch, other than hyperalpha) will not necessarily correspond to a publication run.

Operation and Implementation

Background

In the default operation, a Makefile controls Sphinx operations and builds. There is a third-party SCons interface that we could use as well, I don't think this matters. Using a system like this makes it easier to manage the collection of different build targets (html, man, pdf, pub.) It likely (though not certainly) seems to make sense to build on existing build system.

The build system for the driver documentation (i.e. build.py in the apidocs) repository allows us to build documentation (from Sphinx, in many cases) by pulling from git repositories and building from a specific git tag. The builds are then located (per driver) in versioned directories based on the tag name. A symbolic link named "current" points to the current version of the documentation. These builds are then checked into the apidocs repo, pushed to github, and then a command is issued on the web servers to pull the apidocs repo, into the "public" directory for api.mongodb.org."

While the apidocs approach is useful and is nearly what the new MongoDB documentation needs, it lacks:

  • Building from multiple branches.
  • Automatic/(near)-instant feedback for the "hyperalpha" branch (only)
  • Putting information related to the version/branch of the documentation in the display of the documentation itself.

Additionally, while storing previous builds of the documentation has some value for the drivers, it holds less value for the server docs.

Interface/Design

If we use git as a transport for deploying content to production, as with the "apidocs" repo; then the build system could consist of nothing more than a Makefile target in the existing documentation build system that builds the version of git's working copy and moves it to the "docs-publication repo" and from here the deployment process is identical to the driver docs.

In this case, we'd need to make sure that we provide some check to prevent people from (likely accidentally) building current/master/hyperalpha into a maintenance branch (for example.) This might require some way of ensuring that the remote branches are properly mapped to the local branches. The "hyperalpha," branch automated builds would probably then need to happen through some other method.

Problems here (can be addressed, but seem like potential hang ups:)

  • Checking to make sure that public branches referenced in the build process actually exist.
  • If people's local branches are misconfigured respective to remote branches they may/will end up building versions that don't make sense. It doesn't make much sense to enforce git use policy in this way, at least without a safe "make config-git-branches" target that ensures things are properly configured.
  • Having a build process that is itself versioned in a branched system that it must build, makes it difficult to update the build system. At the same time, putting the build system in the "transport" repository increases the complexity for people who (might) want to get involved with or test the documentation.

Open Questions and Considerations

  • The "read the docs provides some automation and chrome around Sphinx documentation workflow, and their system is open source (link above.) I think it's more than the MongoDB documentation needs, but might worth tracking.

  • How the templates get information about the public branches.

    Above I mention having a text file with a list of branches to build from. As part of the documentation build system we need a way of getting information about the different public branches into the actual display of the documentation.

  • Some of the content in the manual may be suitable for inclusion in the main server distribution, but this process needs to be automated and coordinated with build engineering/release management for the server project.

  • Heretofore, I've been building the docs using the "html" target. As we move to production I think we should move to using "dirhtml" and maybe doing a little bit of clean up of the Makefile. This is trivial, but we need to make a decision.

  • The build system needs to include support for including publishing PDF and ePUB editions of the manual, at least for the releases. (git might be a poor transport for this, we might not care.)

  • It might make sense to have some simple git-use helpers (or documentation!) for some of the more basic cherry picking, merging, and initial branch configuration tasks to lower the barrier for new people working on the docs and prevent simple errors.