jruby

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JRuby (http://www.jruby.org) is an implementation of Ruby (http://www.ruby-lang.org) on the JVM.

GitHub repo: https://github.com/cpuguy83/docker-jruby

Library reference

This content is imported from the official Docker Library docs, and is provided by the original uploader. You can view the Docker Store page for this image at https://store.docker.com/images/jruby

Supported tags and respective Dockerfile links

Quick reference

What is JRuby?

JRuby (http://www.jruby.org) is an implementation of Ruby (http://www.ruby-lang.org) on the JVM.

Ruby is a dynamic, reflective, object-oriented, general-purpose, open-source programming language. According to its authors, Ruby was influenced by Perl, Smalltalk, Eiffel, Ada, and Lisp. It supports multiple programming paradigms, including functional, object-oriented, and imperative. It also has a dynamic type system and automatic memory management.

wikipedia.org/wiki/Ruby_(programming_language)

JRuby leverages the robustness and speed of the JVM while providing the same Ruby that you already know and love. With JRuby you are able to take advantage of real native threads, enhanced garbage collection, and even import and use java libraries.

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How to use this image

Create a Dockerfile in your Ruby app project

FROM jruby:1.7-onbuild
CMD ["./your-daemon-or-script.rb"]

Put this file in the root of your app, next to the Gemfile.

This image includes multiple ONBUILD triggers which should be all you need to bootstrap most applications. The build will COPY . /usr/src/app and RUN bundle install.

You can then build and run the Ruby image:

$ docker build -t my-ruby-app .
$ docker run -it --name my-running-script my-ruby-app

Generate a Gemfile.lock

The onbuild tag expects a Gemfile.lock in your app directory. This docker run will help you generate one. Run it in the root of your app, next to the Gemfile:

$ docker run --rm -v "$PWD":/usr/src/app -w /usr/src/app jruby:1.7 bundle install --system

Run a single Ruby script

For many simple, single file projects, you may find it inconvenient to write a complete Dockerfile. In such cases, you can run a Ruby script by using the Ruby Docker image directly:

$ docker run -it --rm --name my-running-script -v "$PWD":/usr/src/myapp -w /usr/src/myapp jruby:1.7 jruby your-daemon-or-script.rb

Image Variants

The jruby images come in many flavors, each designed for a specific use case.

jruby:<version>

This is the defacto image. If you are unsure about what your needs are, you probably want to use this one. It is designed to be used both as a throw away container (mount your source code and start the container to start your app), as well as the base to build other images off of.

jruby:alpine

This image is based on the popular Alpine Linux project, available in the alpine official image. Alpine Linux is much smaller than most distribution base images (~5MB), and thus leads to much slimmer images in general.

This variant is highly recommended when final image size being as small as possible is desired. The main caveat to note is that it does use musl libc instead of glibc and friends, so certain software might run into issues depending on the depth of their libc requirements. However, most software doesn’t have an issue with this, so this variant is usually a very safe choice. See this Hacker News comment thread for more discussion of the issues that might arise and some pro/con comparisons of using Alpine-based images.

To minimize image size, it’s uncommon for additional related tools (such as git or bash) to be included in Alpine-based images. Using this image as a base, add the things you need in your own Dockerfile (see the alpine image description for examples of how to install packages if you are unfamiliar).

jruby:onbuild

The ONBUILD image variants are deprecated, and their usage is discouraged. For more details, see docker-library/official-images#2076.

While the onbuild variant is really useful for “getting off the ground running” (zero to Dockerized in a short period of time), it’s not recommended for long-term usage within a project due to the lack of control over when the ONBUILD triggers fire (see also docker/docker#5714, docker/docker#8240, docker/docker#11917).

Once you’ve got a handle on how your project functions within Docker, you’ll probably want to adjust your Dockerfile to inherit from a non-onbuild variant and copy the commands from the onbuild variant Dockerfile (moving the ONBUILD lines to the end and removing the ONBUILD keywords) into your own file so that you have tighter control over them and more transparency for yourself and others looking at your Dockerfile as to what it does. This also makes it easier to add additional requirements as time goes on (such as installing more packages before performing the previously-ONBUILD steps).

License

View license information for the software contained in this image.

As with all Docker images, these likely also contain other software which may be under other licenses (such as Bash, etc from the base distribution, along with any direct or indirect dependencies of the primary software being contained).

Some additional license information which was able to be auto-detected might be found in the repo-info repository’s jruby/ directory.

As for any pre-built image usage, it is the image user’s responsibility to ensure that any use of this image complies with any relevant licenses for all software contained within.

library, sample, jruby