Welcome to the World of Release Engineering!

Have you ever wondered how the apps and software you use daily transition from a developer's computer to your device, ready for use? This is the realm of Release Engineering, often dubbed Releng. It's a fascinating sub-discipline in software engineering that's all about transforming source code into the finished products we all love and use. Think of it like the bridge between creating software in small teams and producing it on a large, industrial scale.

Who is this Post for?

I wrote this post with a specific audience in mind: students, open source enthusiasts, and interns, especially those participating in programs like Outreachy or those looking to gain experience in open source contributions.

The Role of the Release Engineering Team

A release engineering team is the people who make sure application releases run smoothly. They integrate the efforts of different product development teams to produce a stable and safe product. Their job is to ensure that the software's production is repeatable, delivers predictable results, and scales.

Inside Firefox's Release Engineering

Delving into the real-world scenario of Firefox, the Firefox Release Engineering team focuses on continuous delivery, ensuring that each Firefox product is signed and published on schedule. We handle work from automating complex tasks to making sure updates reach your browser. We also develop and maintain web apps, libraries, and automation used to sign, repackage, and publish Firefox, web extensions, and Mozilla VPN on Desktop and Android platforms.

Signing 🔏 CI ✅ and CD 🚀

  • Application Signing: This process is akin to placing a digital seal of authenticity on software, ensuring its origin and integrity. Imagine signing a digital document to certify its credibility; similarly, application signing allows software authors to "sign" the software they publish and guarantee the application has not been altered since it was signed.

  • Continuous Integration (CI): Think of CI as the software's regular health check-up. It's a process where changes made by developers are frequently integrated into the codebase and tested. This routine helps the software remains healthy, catching potential issues early.

  • Continuous Deployment (CD): Continuous Deployment is the automated release of a software product. Imagine a conveyor belt in a factory continuously moving products to the shipping area; similarly, CD ensures that every change goes through all release phases with little human intervention. This means that new features, bug fixes, and updates are rapidly and reliably delivered, increasing the effectiveness of the engineering process.

The Firefox Release Train

Firefox's approach to releases is highly iterative and user-feedback driven, reflecting the changing nature of web browsers. The Phases of a Firefox Release are:

  1. Nightly: This initial phase, much like a rough draft, is crucial for spotting issues early, and is not yet fully tested.

  2. Beta: This phase is the software equivalent of a movie's rough cut, more refined than Nightly but still ironing out bugs.

  3. Release Candidate (RC): Similar to a movie's final cut, in this phase Firefox is almost ready for release (but possibly needs minor tweaks or bug fixes.)

  4. Stable Release: The grand premiere! The version Firefox's audience receives is polished and ready for widespread use.

  5. Extended Support Release (ESR): Designed for larger organizations, focusing on stability and security, sometimes at the expense of newer features.

Taskcluster and Taskgraph: The Backbone of Firefox's Release Automation

  • Taskcluster: This robust framework underpins Mozilla's CI and release processes. It's a versatile and scalable tool useful for constructing complex CI systems. For example, when code is added to Firefox, Taskcluster executes testing tasks that check if the codebase plus the new code work as intended.

  • Taskgraph: This Python library generates a directed acyclic graph (DAG) of tasks for Taskcluster. Visualize a DAG as a one-way street map without loops, guiding tasks forward until they are all complete.

Ship-It: The Launchpad for Firefox Releases

Ship-It serves as a control panel for Mozilla's release managers, making it easy to configure and execute the automated tasks necessary to deliver Firefox versions (beta, release, ESR, etc.) to their audience. This tool leverages the DAG generated by Taskgraph and executed by Taskcluster.

Balrog: Mozilla's Update Server

Balrog, Mozilla’s update server, functions like a reliable delivery service. It brings the latest and safest versions of Firefox, Mozilla VPN, and Thunderbird to people's devices.

There's a Lot to Learn About Release Engineering

Release engineering is a complex but interesting world. It ensures the software we depend on is created with attention and care. Whether it’s a nightly build or a stable release, each step in the release process plays a critical role in delivering a safe and enjoyable product. So, next time you update your Firefox browser, remember the intricate journey it took in the world of release engineering!