Build system details for Firefox desktop


Thanks to cross-channel, we ship all versions of Firefox from a single localization repository, but each channel uses a different snapshot in time of that repository.

A job, called l10n-bumper, runs on Taskcluster every hour, and stores information on the l10n changesets to use for each build in a file called l10n-changesets.json:

  • For Nightly (mozilla-central), l10n-changesets.json always uses the revision default, and it’s only updated when changing the locales available in the build.
  • Beta builds (mozilla-beta) still use the tip of the l10n repository, but the actual hash is stored in l10n-changesets.json instead of default.
  • Before Release Candidate week, the l10n-bumper is manually stopped on mozilla-beta. Since the configuration change lands only on mozilla-beta, the l10n-bumper will automatically restart at the beginning of the next cycle, when the standard configuration is uplifted from mozilla-central.
  • When the Beta code is merged to Release, l10n-changesets.json moves together with the rest of the code to mozilla-release. That means that Release builds will use the same changesets as the last beta with the same version number, and any further change requires code uplifts.

Timeline and deadlines

This is how Beta looks like in a 4 weeks release cycle, with relevant milestones.

Beta cycle

On Monday, 8 days before the release, the l10n-bumper will stop updating l10n-changesets.json on mozilla-beta.

Once the code merges from Beta to Release, any changeset update would require a manual uplift to mozilla-release and a new Release Candidate (RC) build.

Timeline of all channels, 2 cycles

Updating release

When the code moves from mozilla-beta to mozilla-release, l10n-changesets.json is frozen, as l10n-bumper is not configured to run against the release branch.

In case of severe issues affecting one or more locales, it’s still possible to manually update the shipping changesets. A patch needs to be provided for l10n-changesets.json in mozilla-release branch and approved for uplift by Release Drivers (see for example this bug and associated patch). Note that a dot release is needed in order to ship the updated version to users. This script can be used to validate the updated JSON.

The same process applies to ESR versions, as long as the associated esr repository is included in the current version of cross-channel.