This section outlines a number of common patterns used to maintain documentation.
- Single Source of Truth
- Issue tracker
- Version control and changelogs for the schema and documentation
- Governance process for normative changes to the schema and documentation
- Branch and release management
- Automated build processes
- Reproducible builds
- Deployment and rollback
Single Source of Truth¶
Consider a piece of documentation about how a field within the data standard works.
- This field will probably have a name and a description about how it is used.
- Someone will write that down somewhere.
- Someone else will share that with other people, via email, on a web page, in a pdf, in a presentation, as guidance in a data collection tool, etc
- Those people may introduce small changes, errors, or even improvements as they reproduce the information.
- Further, the ‘master’ description may change over time. How do people know whether the new description, or the old one is the correct one to use? Which (trusted) source should they use? An email someone sent, or the PDF they have in their hand, or…?
In a worst case, people might incorrectly copy the structural information about the standard, e.g. a field name, or where it is nested; or, they might miss a field from a list that's intended to be complete.
Establish a Single Source of Truth (SSOT) for documentation about how the standard works. Other copies should copy verbatim from this - any improvements should be made in the SSOT.
We use a GitHub repository to store our SSOT, as this provides very explicit and fine-grained versioning
In order to ensure documentation is pulled from the SSOT, copies should preferentially be made programmatically.
How do we keep track of suggested changes to the standard: new fields, bug fixes etc.
An issue tracker
We use GitHub issues.
Version control and changelogs for the schema and documentation¶
It is important to know who changed what and when in a standard, for purposes of:
- Auditing changes that have been made
- Reverting changes
- Understanding the context that lead to the way the standard is now
Using version control for the standard schema and documentation provides a full version history of changes. Tools like git/GitHub provide tooling to inspect who editing a specific line of a file. ("git blame")
A changelog provides a less granular view, that is easier/quicker for humans to read, to get a general overview of what has changed.
Both version control commits and changelog entries can link to issues in an issue tracker, to give more info and discussion about how/why the change happened.
e.g. for OCDS we have:
- Changelog - http://standard.open-contracting.org/latest/en/schema/changelog/
- History of every individual change to the OCDS docs/schema - https://github.com/open-contracting/standard/commits/1.1
- When was each line in any given file last changed - https://github.com/open-contracting/standard/blame/1.1/standard/schema/release-schema.json
Governance process for normative changes to the schema and documentation¶
There should be a revision process for substantial changes to a standard, that require a new Major/minor release (see Semantic Versioning). However, we also want to make minor fixes as part of a "patch" release.
A lighter weight review process for "patch" releases.
For OCDS patch releases, we have a 7 day comment period. e.g. https://groups.google.com/a/open-contracting.org/forum/#!topic/standard-discuss/oV5yG7fQF_0
Branch and release management¶
We want to provide multiple versions of the documentation and schema at one time.
Branches corresponding to different deploys of the standard. Tags for specific patch releases of the standard.
Deploying different copies of the docs for different versions of the standard.
Making it easy to deploy a copy for any branch.
Branches are named:
Releases are named:
Automated build processes¶
Normally, building the standard documentation and publishing the schema is a complicated process involving many steps to run and test. To save time, and to avoid mistakes, these need to be run automatically. Feedback needs to be given to the documentation or schema writers to check if their changes look correct. Also, checks regarding the integrity of the documentation and schema need to be run for every change made.
Use continuous integration to run the tests and publish a version of the docs for every branch in the standard documentation. This means that the integrity tests are run and you can see version of that branch schema/documentation online.
We use two different automated build services, for different projects:
(1) Read the docs is designed specifically for building Sphinx docs. It will rebuild a version of the documentation every time a commit if pushed to the corresponding branch on GitHub. Read the Docs being designed specifically for Sphinx is useful because it will automatically hosts the docs, and provides a version/language switcher out of the docs. It gives a lot of control (e.g. you can have whatever custom directives and theming you want, you can point a custom domain at it), but is less flexible than a generic build service. It also requires a manual step to add a new branch/version to the docs. We use Read the Docs for lots of smaller docs sites
(2) Travis - is a generic build service (again building every time something is pushed to GitHub), so requires a bit more setup than Read the Docs, but also gives you maximum flexibility over what commands get run. It can also run tests of the documentation/schema before the build. It doesn’t host docs, but can be set up to push the built docs to a hosting provider of your choice.
It is important to be able to see what the standard documentation used to look like:
- To audit changes where version control or changelogs are too confusing or not sufficient.
- To revert to a known good copy of the standard documentation, if something has gone wrong since.
In order to do this we need to be able to reproduce the same HTML (and other format) outputs for any given commit of the standard.
Version control provides a basis to do this, with a full history of commits to the standard and docs. However, the build process for the documentation may rely on external scripts and resources that may change independently of the standard's revision process.
The solution is to ensure that all external scripts and resources are pulled in at a specific version.
Some specific examples of how we pull in specific versions:
- Pin Python dependencies to a specific version
- When pulling in other git repositories, ask for a specific commit or tag
- Commit files that are pulled from non-versioned platforms - e.g. commit all .po files instead of fetching them from Transifex during the build.
- Always build from a clean repository checkout to ensure that you haven’t got any extra files, or uncommitted changes. (Travis and readthedocs do this by default).
Note that in some cases, reproducibility requirements might be relaxed. For example, a standard may be configured to always build with the latest version of an external theme, and so this would not be pinned.
Deployment and rollback¶
Sometimes the build process for a new version of a standard can go wrong.
Author-error can lead to mistakes in the standard, external dependencies may have been deleted from their source, or a key software service may be down.
'live' releases of a standard should be manually deployed, and it should be possible to rollback changes at any time if problems are detected.
The build and deployment process for the standard copies compiled static HTML files to the server in a folder named based on the branch and date of build.
A symlink from the branch name, to this datestamped folder is then created.
This allows an administrator with access to the server to instantly switch the symlink to point to any new or previous build as required.
The build process can be configured so that the symlink for full releases of the standard are only ever edited manually, preventing accidental changes to releases in use.
Currently we only use this approach for OCDS.