String extraction, translation and export tools for the 21st century. "Moving strings around so you don't have to"
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Shuttle: Magic localization dust

Shuttle is a website allowing for the automatic extraction and reintegration of localizable strings in a code base. In addition, it provides a workflow for translators and reviewers optimized for the efficient processing of many strings. Finally, for project managers, it provides a dashboard allowing them to view and manage the progress of a localization effort.

The typical Shuttle workflow is as follows:

  1. An engineer makes a commit to a Project, and marks that commit as requiring localization in Shuttle.
  2. Shuttle scans the commit for any localizable strings using its {Importer}s.
  3. New or modified localizable strings are marked as pending translation. They appear on the translators’ dashboard.
  4. Translators translate all these strings. They then appear on the reviewers’ dashboard.
  5. Reviewers review and approve translations.
  6. Once all translations applying to a commit are approved for all of a Project's required localizations, the Commit is marked as ready.
  7. When the commit is deployed, Shuttle provides a manifest of translated strings that is downloaded as part of the deploy artifact.

The whole process is extremely parallelizable: while one commit might be pending translation or review, an engineer can make additional commits with new copy, and they will also sit in the queue awaiting translation. Once any commit is fully localized, it is marked as ready for release.

Shuttle will refuse to deliver a manifest for a commit that has not been fully translated and reviewed. To prevent such deploys, engineers should add a test to their CI script that ensures that the manifest endpoint does not return 404.

Getting Started

Starting the server

Developing for Shuttle requires Ruby 1.9.3, PostgreSQL, Redis, and a modern version of libarchive. To run Shuttle for the first time:

  1. Clone this project.
  2. Install a modern version of libarchive, one that supports the GNU tar format. (The version that comes with Mac OS X does not.) On OS X, you can run

    brew install libarchive

    If you have an out-of-date libarchive version, you will see missing constant errors in the multifile exporters.

  3. Create a PostgreSQL user called shuttle, and make it the owner of two PostgreSQL databases, shuttle_development and shuttle_test:

    brew install postgresql
    createuser shuttle
    createdb -O shuttle shuttle_development
    createdb -O shuttle shuttle_test
  4. Install the libarchive gem using a modern version of libarchive. For Homebrew, run

    gem install libarchive -- --with-opt-dir=/usr/local/Cellar/libarchive/3.1.2
  5. Install Redis and ElasticSearch. For Homebrew, run

    brew install redis elasticsearch

    and follow the post-install instructions.

  6. You’ll need to run Bundler: bundle install
  7. Run rake db:migrate db:seed to seed the database.
  8. Run RAILS_ENV=test rake db:migrate to setup the test database.
  9. Verify that all specs pass with rspec spec
  10. To run the server, use rails server
  11. To run the job queue: bundle exec sidekiq -C config/sidekiq.yml to run the Sidekiq development server.
  12. Visit http://localhost:3000 and log in with the credentials:

    password: password123

Adding your first project

You are now an admin user on Shuttle. You can click the "Add Project" button to configure your first project. You will need at least read-only access to this project's Git repository. Set up the locale and importing settings as neessary.

Once the project has been added, you can add a commit for it to import strings from. For starters, try entering "HEAD". Once you click "Add", you should see your Sidekiq server output start to fill up with importers processing all the blobs in your HEAD commit. There may be a delay as the repository is checked out to tmp/repos for the first time.

Refresh the Shuttle home page. When you click on your project name, it should expand to show your commit. The progress bar should be orange and indeterminate, indicating that the commit is being processed. Once processing is finished, the Sidekiq log will quiet down and the progress bar should change to an empty (white) bar, indicating that no translations have been made yet.

Click the progress bar to expand the commit and get detailed status information. You should see three numbers. The badged number on the right is the total number of translatable strings found in your project. Inside the progress bar are two numbers separated by a slash. The first number is the number of finished translations across all required locales (should be zero), and the second number is the total number of required translations (should be the number of translatable strings times the number of required locales, minus any keys that are not applicable to certain locales).

Clicking on the commit's SHA will bring you to the GitHub webpage for that commit, if the project's repository URL is recognized as a GitHub project. The "Redo Import" button re-runs an import, in the event that the previous import completed abnormally. The "Status" button takes you to a detailed status page where you can see a list of strings in the project and their translation statuses.

The "Import and approve a localization" field allows you to import an existing localization. For example, if your Rails project already has an "fr.yml" file that you want to import into Shuttle (to save your translators the effort of retyping all those translations), you can use this field to do it.

These are the features typically used by users with the "monitor" role. As an admin you can also explore and use the tools used by translators: The translation/review panel, the global search page, and the glossary. Managing other users is an admin-specific feature.

One last important feature that admins have is the ability to visit the "/sidekiq" URL, which lets them monitor and manage Sidekiq workers.

Deploying to production

Shuttle does not come with a deploy script; you should use whatever deploy system you are comfortable. Your deploy script should, in addition to copying the code and starting the Rails server,

  1. stop and restart the Sidekiq workers (the Sidekiq gem has many scripts for this), and
  2. install the cron entries (the Whenever gem has scripts for this).


Comprehensive documentation is written in YARD- and Markdown-formatted comments throughout the source. To view this documentation as an HTML site, run rake yard.

CoffeeScript libraries are documented using the YARD format as well, but YARD does not as yet recognize them as documentable files. A .codoopts file is included in case you wish to use Codo to generate the CoffeeScript docs, but as of now Codo does not recognize the ERb files, and does not use the full set of Markdown syntax features used in the documenttion.



This is a pretty typical Rails website, save for the views, which are written using Erector. The views forgo the traditional Rails concepts of partials and templates in favor of analogous OOP concepts more familiar to software developers: methods and inheritance. All views inherit from an abstract Erector widget which provides layout; and all views have their content split into multiple private methods.

In addition to the usual helpers (in app/helpers), there are view mixins under app/views/additions that simplify view coding.

JavaScript files are organized into four possible locations:

  • Third-party JavaScript libraries are in vendor/assets/javascripts and loaded in the application.js manifest.
  • JavaScript modules or helpers that are not specific to a particular page or site area are in lib/assets/javascripts and also loaded in application.js.
  • JavaScript modules or helpers specific to a particular area of the site are in app/assets/javascripts and also loaded in application.js.
  • Small JavaScript snippets, glue code, or other code intended to add dynamic behavior to a specific page is in a .js file named the same as, and placed alongside, the .html.rb view file. For example, if app/views/projects/new.html.rb needed a bit of JS glue code, it would be placed in app/views/projects/new.js. This code is placed in a <SCRIPT> tag at the end of the view by the {Views::Layouts::Application#inline_javascript} method.

CSS files are similarly organized:

  • Third-party CSS files are in vendor/assets/stylesheets and loaded in the application.css manifest.
  • CSS styles or helpers global to the entire website are in lib/assets/stylesheets and also loaded in application.css.
  • CSS styles specific to a single page or a related group of pages are placed in app/assets/stylesheets and also loaded in application.css. Each <BODY> tag is given a class name equal to the controller name, and an ID equal to the controller and action name separated with a dash. For instance, the projects/new action's body would be <body class=projects id=projects-new>.


For information about requests and responses, see {ApplicationController}.


Each {Project} has multiple {Commit Commits}. When a Commit is created, it is scanned by {Importer Importers} for localizable strings. These strings are represented as {Translation} records. A base Translation is created in the project's base locale, and preapproved, and pending, untranslated Translations are created for each target locale. These families of Translations are grouped under {Key} records, one for each unique key in the Project. The newly created Translations are in the Project's base locale. Future imports reuse the existing Keys if the source copy is unchanged, otherwise generating new Keys and new Translations for the new source copy. {User Users} with the translator role then fill out pending Translations, and reviewers approve them.

When all of a Commit's Translations in all of a Project's required locales are marked as approved, the Commit is marked as ready. This Commit's translated copy can then be exported to a manifest file using an {Exporter}, or localized versions of project files can be generated and downloaded using a {Localizer}.

Because new source copy overwrites existing source copy, a translation memory consisting of {TranslationUnit TranslationUnits} is maintained. This is used by the content-matching system to provide match suggestions to translators.

Models make extensive use of advanced PostgreSQL features for efficiency and convenience. Cached counters are updated using triggers and rules, foreign key constraints and hooks are enforced at the database level, and validations are backed up by corresponding CHECK triggers. This helps ensure referential and data integrity even in situations where Rails fails, or outside of the Rails stack. See the various migrations to learn more about the triggers, rules, and constraints being used. See the app/models/concerns directory for the Active Record mixins that leverage these PostgreSQL features.

Observers are used for more high-level triggers, such as sending emails. See the classes in app/models/observers for more.

Models also use the HasMetadataColumn gem to reduce their width and incorporate schemaless data. Most models have a JSON-formatted metadata column to which new information can be added or removed without having to create new migrations.

Authentication and Authorization

Authentication is handled by Devise. Users log in using their email address and a password.

Shuttle uses a role-based authorization system. See the {User} model for details on the available user roles and their privileges.


Various Rake tasks are available under lib/tasks. These include tasks for importing locale data and development tasks.

Importing and Exporting

Shuttle provides a number of importer and exporter libraries that are capable of extracting strings or generating output in formats such as Rails i18n or iOS .strings files. These classes are in lib/importer and lib/exporter.

Some i18n platforms require that localizations be split across multiple files; normally, exporters only export a single file. To get around this restriction, these exporters will export gzip-compressed tarballs that can be expanded into the project's root directory.

Localization of files with inline copy

While importers can scan an entire project for localizable strings, exporters are built on the assumption that the exported file will contain only translated strings, and no other content or metadata. This will not work with, for example, xib files, which must be duplicated in their entirety (with the localized copy substituted for the original copy).

Shuttle handles this process with file localization. Importers that work with localizers (rather than exporters) also record metadata about where in the file the string came from. A localizer (under lib/localizer) recreates the original file and substitutes translated copy using the source information.


Fencing is the act of marking off portions of text as untranslatable (for example, HTML tags). These portions can be moved but not altered or deleted, in most cases. Fencing can also be used to mark off interpolation variables, such as %{count} in the Ruby i18n format.

A variety of fencers for common formats is provided under lib/fencer; they are not subclasses of an abstract superclass, but do all respond to the same informal interface.


All models, controllers, and library files are unit-tested with RSpec specs under the spec directory. Run unit tests with the rspec spec command. Views and JavaScript files are not specced. No integration or acceptance tests are written. Almost all unit tests use factories rather than mocks, putting them somewhat closer to integration tests.

To-Do Items

Translation view

  • Display meta-indication of special characters, esp. nonprinting ones
  • Translator ability to flag a translation with a question or issue, and then mark it resolved


  • Token object
  • Token explosions (UI)
  • Language metadata

Large-format translation view

  • Git context display

Finish account administration

  • Design and verify Devise account pages


  • Segmentation for large files
  • <STYLE>/<SCRIPT> tag content should not be localizable


  • Transifex API integration

Performance optimizations

  • Use PSQL trigger-based cached counters


  • Second reviewer role: integration review (by commit) (?)