Continuous integration/Documentation generation

Documentation is automatically generated and published to doc.wikimedia.org. For increased flexibility and security, the static sites are generated inside labs instances, they are fetched from the CI master host which then rsync them to the documentation host (doc1001.eqiad.wmnet since January 9th 2019). This page documents the workflow, part of the technical implementation, and how to define a new job.

Zuul
Our reacts on two kinds of Gerrit events which are matched by two different pipelines:

ref-updated could covers the changes being merged, but the event is not associated with a Gerrit change number which prevents us from reporting back to the Gerrit interface. We thus use postmerge to report back in Gerrit so the user knows it has been generated and the publish pipeline which handles references updates matching ^refs/tags/.

In both case (change-merged or ref-updated) we trigger the same job to generate the documentation for any branch or tag. We thus need to namespace the documentation under doc.wikimedia.org based on the branch name or the tag name. The information is carried differently between events and the reference is slightly different between branch updates and tags. The conversion logic is carried by a which is associated to all the publish jobs. It injects to the Gearman function (and thus the Jenkins job environment) a variable DOC_SUBPATH which represents the version. Example:


 * change merged on REL1_24 branch: DOC_SUBPATH = REL1_24
 * refs/tags/1.24.0 updated: DOC_SUBPATH = 1.24.0

Reference:

We can thus reuse that DOC_SUBPATH parameter to easily namespace the jobs per versions.

Jenkins job builder definitions
Most of the logic is defined in Jenkins Job Builder  configuration file.

In a job definition, a  defines what steps to execute. We provide a builder macro called  that takes care of transferring the generated files to the web server of https://doc.wikimedia.org/. It takes two parameters:
 * 1)   Directory holding documentation files relative to workspace (without trailing slash)
 * 2)   Directory under https://doc.wikimedia.org/

Example job definition:

This will invoke the build scripts (doxygen and jsduck) and publish their results (respectively in doc/html and docs) to https://doc.wikimedia.org/myproject/.

To namespace the documentation based on project version, use the Zuul-generated  (derived from branch or tag name). Simply insert it in the  parameter. You will need to invoke the builder assert-env-doc_subpath. Example for MediaWiki (mediawiki-core-doxygen-publish job):

This publishes the documentation at https://doc.wikimedia.org/mediawiki-core/master/php/, and also publishes release branch documentation at, for example, https://doc.wikimedia.org/mediawiki-core/REL1_24/php/

Architecture
The documentations are ultimately published on doc.wikimedia.org which is a production machine (doc1001.eqiad.wmnet since January 2019). They are generated on labs instance part of the integration labs project which are not allowed to communicate with production machines.

A job publish-to-contint1001 executes on the CI Jenkins master node which fetch artifacts from the build workspace using rsync + ssh. The content is then rsynced to doc1001.eqiad.wmnet (rsync://doc1001.eqiad.wmnet/doc/).

Updating the doc.wikimedia.org site
The "static" content of the site is in the git repository. Most of the pages use light PHP to show a TOC, include a footer, etc. The git docroot repository is cloned on doc1001.eqiad.wmnet at /srv/docroot, that is done by puppet profile::doc.

After a change is merged, one has to update the docroot: ssh doc1001.eqiad.wmnet git -C /srv/docroot pull