Traveling Ruby: Self-Contained, Portable Ruby Binaries for Easy Distribution

Traveling Ruby is an innovative project dedicated to providing self-contained, “portable” Ruby binaries. These binaries are designed to run seamlessly across various Linux distributions and macOS machines. While Windows support is also available, it comes with specific considerations that we will address later. The core purpose of Traveling Ruby is to empower Ruby application developers. It allows them to package these portable Ruby binaries directly with their applications. This approach streamlines distribution, enabling developers to deliver a single, comprehensive package to end-users. End users can then run the Ruby application without the often complex prerequisite of installing Ruby or managing gems separately.

Two-minute introductory video about Traveling Ruby, explaining portable Ruby binaries for cross-platform application distribution.

A Quick Introduction in 2 Minutes

Motivation Behind Portable Ruby Binaries

Ruby stands out as a versatile and beloved programming language. While widely recognized for web development, its capabilities extend far beyond. For years, Ruby has proven its effectiveness in crafting system administration automation scripts, developer command-line tools, and more. The success of tools like Heroku’s Toolbelt and Chef underscores Ruby’s suitability for these types of applications.

However, distributing Ruby applications to end-users, particularly those with limited technical expertise or no Ruby programming background, presents significant challenges. Requiring users to install Ruby beforehand or navigate RubyGems can easily lead to complications. Even users who already have Ruby installed may encounter issues, such as version incompatibilities. These hurdles represent real obstacles that can negatively impact user experience and, consequently, your reputation as a developer or software provider.

One common strategy to overcome these distribution challenges involves creating operating system-specific installation packages like DEBs, RPMs, or .pkgs. While effective in some respects, this method has notable drawbacks:

Extensive Development Effort: Building OS-specific packages demands substantial work. Developers must create separate packages not only for each operating system (macOS, Windows, Linux) but also for different versions of each OS. In the fragmented Linux ecosystem, each distribution and version adds to the complexity. Supporting, for example, two versions of CentOS/RHEL, two of Debian, and three of Ubuntu, along with a couple of recent macOS releases, would require creating nine distinct packages.
Heavyweight Tooling and Infrastructure: Typically, OS-specific packages must be built on their target operating system. This necessitates complex and resource-intensive build environments, often involving fleets of virtual machines (VMs). For instance, Ubuntu 18.04 DEBs must be built on Ubuntu 18.04, making it impossible to build them directly from a macOS development machine.

Chef, for example, adopted this approach and developed Omnibus, an automation system that orchestrates a VM army to build platform-specific packages. While functional, this system is undeniably heavyweight and cumbersome. It demands significant build infrastructure to achieve reasonable build times – a setup that can be both costly and complex to manage.

Fortunately, a more streamlined and efficient solution exists: Traveling Ruby.

The Streamlined Approach of Traveling Ruby

Traveling Ruby champions a simpler distribution model: packaging your application as a self-contained archive (tar.gz/zip). This archive includes a precompiled Ruby interpreter tailored for a specific platform, provided by the Traveling Ruby project itself, alongside all the gems your application needs. This approach eliminates the need for intricate build systems and heavyweight tooling.

Creating tar.gz/zip archives is straightforward and can be done on any platform using basic tools.
You can generate packages for any target OS, regardless of your development OS.

This drastically simplifies the release process. Instead of managing nearly ten packages and a VM farm, you can quickly generate just three packages from your development machine, covering the major platforms:

Linux x86_64
macOS
Windows (though with the Windows caveats mentioned earlier)

However, delivering a precompiled Ruby interpreter that works universally across diverse end-user systems is technically challenging. The following section delves into the reasons behind this difficulty. Traveling Ruby focuses on providing precompiled Ruby 2.4 binaries specifically engineered to address these challenges and ensure broad compatibility.

Getting Started with Traveling Ruby

To begin using Traveling Ruby, explore these tutorials:

[List of Tutorials (URLs would be here in a real article)]

Once you’ve completed the tutorials, delve into these guides for more advanced topics and in-depth understanding:

[List of Guides (URLs would be here in a real article)]

For real-world examples of how developers have successfully packaged their Ruby tools using Traveling Ruby, refer to these case studies:

[List of Real-World Examples (URLs would be here in a real article)]

Important Caveats and Considerations

Native Extensions

Limited Windows Support: Traveling Ruby’s native extension support is currently limited to Linux and macOS packages. Windows package creation does not yet include native extension support.
Specific Gem Compatibility: Traveling Ruby supports a curated selection of popular native extension gems, and even then, only specific versions are guaranteed to work. You cannot assume compatibility with arbitrary native extension gems.
Tutorial Guidance: Tutorial 3 (link provided earlier) specifically addresses native extensions and their handling within Traveling Ruby.

Windows Specifics

macOS or Linux Required for Windows Packaging: Currently, creating Windows packages with Traveling Ruby necessitates using macOS or Linux. The tutorials and documentation are not designed for a Windows-based Ruby development environment. This limitation stems from the documentation’s heavy reliance on standard Unix command-line tools not readily available on Windows. Future development may explore Ruby-based tooling to enable Windows-native documentation and package creation.
Ruby Version and Native Extension Restrictions: Windows support is currently limited to Ruby 2.4.10, and as previously mentioned, native extensions are not yet supported within Windows packages.

Building Traveling Ruby Binaries

The Traveling Ruby project provides pre-built binaries ready for application developers. The build systems used to create these binaries are available in this repository. As an application developer, you generally do not need to interact with the build system directly. It’s primarily relevant for contributors to the Traveling Ruby project, those seeking to reproduce the binaries, or developers needing to customize the binaries for specific purposes.

For details on the Linux build system, consult [linux/README.md](link to linux README).

For the macOS build system, see [osx/README.md](link to osx README).

Future Development and Roadmap

Rails Example: Providing a practical example demonstrating Traveling Ruby’s use with a Rails application.
Windows Native Extension Support: Extending native extension support to Windows packages.
Windows Build System Documentation: Documenting the Windows build system for advanced users and contributors.
Single Executable Output: Exploring options for creating a single executable file instead of a directory-based package for simpler distribution.
Inspiration from Similar Projects: Drawing insights from projects like enclose.io and ruby-packer. See [this Hacker News comment](Hacker News comment link) for a comparative analysis of these approaches.

Frequently Asked Questions (FAQ)

Why is Creating a Universal Precompiled Ruby Interpreter So Difficult?

You might assume that compiling a Ruby binary on a specific operating system would ensure compatibility for all users on that same OS, even the same version. However, this is not always the case. Two key issues can prevent binary compatibility across systems:

Library Dependencies: Compiled binaries depend on external libraries. During Ruby compilation, the build system might inadvertently link to non-standard libraries present on your development system but not universally available on end-user systems. Even different versions of the same OS can have varying library sets, making assumptions about library availability unreliable.
glibc Symbol Versioning (Linux): On Linux, the GNU C Library (glibc) introduces symbol versioning. Each function (symbol) within glibc can have multiple versions. This allows glibc developers to update function behavior without breaking backward compatibility. However, during linking, the linker often defaults to the newest symbol version. This can lead to binaries that depend on a recent glibc version, making them incompatible with older systems that have older glibc versions.

Unless you manually specify symbol versions for every dependency – an impractical task – it’s challenging to control glibc symbol linkage directly.

The most effective way to mitigate glibc symbol issues and prevent accidental linking to unwanted libraries is to use a tightly controlled build environment. For Linux, this environment typically includes an older glibc version. This controlled environment is sometimes referred to as a “holy build box.”

Traveling Ruby incorporates such a holy build box in its build process to ensure maximum binary compatibility.

Why Not Just Statically Link the Ruby Binary?

Static linking, while seemingly a solution, presents its own set of challenges and limitations in the context of Ruby:

Complexity of Static Linking: Achieving proper static linking is not as simple as adding a compiler flag. Compilers prefer dynamic linking, and forcing static linking often requires extensive manual modifications to build configurations and Makefiles.
Ruby Incompatibility with Static Linking to C Library: Ruby’s architecture is fundamentally incompatible with static linking to the C library on Linux. Statically linked executables cannot dynamically load shared libraries. Ruby extensions are implemented as shared libraries. A Ruby interpreter unable to load extensions would be severely limited in functionality, losing access to a vast ecosystem of gems and native functionalities.

Therefore, Traveling Ruby adopts a hybrid approach. The Ruby binaries are dynamically linked against the C library but are carefully built to use older glibc symbols, avoiding the symbol versioning problems. Furthermore, Traveling Ruby bundles carefully compiled versions of essential dependent shared libraries like OpenSSL, ncurses, and libedit to ensure consistency and portability.

Why is Bundling a Ruby Interpreter Crucial for End-User Experience?

End-users prioritize ease of use and immediate application access. Requiring them to install Ruby as a prerequisite introduces friction and potential points of failure. Here are common problems users encounter:

Installation Method Confusion: Numerous methods exist for installing Ruby (source compilation, package managers like apt-get and yum, version managers like RVM/rbenv/chruby). This choice overload can confuse less experienced users. Furthermore, not all methods are equally suitable. Package managers often provide outdated Ruby versions, while source compilation and version managers require pre-installed toolchains and libraries, adding complexity for users unfamiliar with development environments. Outdated or inaccurate online tutorials further compound this confusion.
Incorrect Installation and PATH Issues: Users might install Ruby incorrectly, placing it in a location not included in their system’s PATH environment variable. This leads to “command not found” errors when trying to run Ruby or Ruby-based applications. While PATH configuration is familiar to developers, it’s often opaque to general users.
RubyGems and Package Management Complexities: Even if users successfully install Ruby, distributing your application via RubyGems introduces another layer of potential problems:
- PATH Configuration after Gem Installation: On some systems, gems installed via RubyGems are not automatically added to the user’s PATH, leading to similar “command not found” issues.
- Permissions and sudo: Depending on the Ruby installation method and system configuration, gem install might require sudo (administrator privileges). Incorrect sudo usage can lead to permission problems within the user’s gem installation directory (GEM_HOME).
- sudo and Environment Variables: sudo often resets environment variables, which can be critical for Ruby’s proper functioning. Version managers like RVM, rbenv, and chruby rely heavily on specific environment variable configurations (PATH, RUBYLIB, GEM_HOME). Incorrect sudo usage can disrupt these configurations. While tools like rvmsudo exist for RVM to preserve environment variables, similar solutions are less readily available or understood for rbenv and chruby.

Addressing these issues through extensive documentation and user support is possible, as exemplified by projects like Phusion Passenger. However, creating and maintaining comprehensive, platform-specific Ruby installation instructions is a significant ongoing effort.

Traveling Ruby offers a simpler and more user-friendly alternative by eliminating the need for end-users to manage Ruby installation complexities altogether. While projects like Phusion Passenger, designed to integrate with existing Ruby installations, cannot directly leverage Traveling Ruby, it’s an ideal solution for packaging command-line tools and other Ruby applications intended for broad distribution.

Are These User Problems Really That Significant?

Yes. These seemingly minor installation hurdles can deter users from adopting your application and negatively impact your project’s reputation. Chef, for instance, faced considerable challenges due to user difficulties with RubyGems-based installation in its early days. While Chef now offers platform-specific packages (DEBs, RPMs), the perception of installation complexity persists for some users.

macOS Includes Ruby. Should I Still Bundle a Ruby Interpreter?

Yes. Even though macOS includes a system Ruby, bundling a Ruby interpreter with your application remains crucial. macOS Ruby versions vary across macOS releases. Even minor Ruby version differences can introduce compatibility issues. The keyword argument changes introduced in Ruby 2.7 and later are a prime example of potential breaking changes. Bundling Ruby guarantees consistent application behavior regardless of the user’s macOS version or system Ruby configuration, preventing unexpected compatibility problems caused by OS upgrades.

Does Traveling Ruby Support Windows?

Yes, Traveling Ruby offers [Windows support](link to Windows tutorial), but with the caveats detailed earlier, particularly regarding native extension limitations and the requirement to build Windows packages on macOS or Linux.

What is the Size Overhead of Packaging Ruby with Traveling Ruby?

A basic “hello world” application packaged with Traveling Ruby results in a compressed archive of approximately 6 MB. This relatively small overhead is a worthwhile trade-off for the significant gains in distribution simplicity and user experience.