The AusNimbus builder for Ruby applications provides a fast, secure and reliable Rack, Rails and Ruby hosting environment.

This document describes the behaviour and environment configuration when running your Ruby apps on AusNimbus.

Table of Contents

Runtime Environments

AusNimbus supports various Ruby versions.

The currently supported versions are 2.1, 2.2, 2.3, 2.4

Web Process

Your application's web processes must bind to port 8080.

AusNimbus handles SSL termination at the load balancer.

The recommended webserver is Puma and supports automatic optimization.

Dependency Management

The builder uses the bundler for installing dependencies.

Environment Configuration

The following environment variables are available for you to configure your Ruby environment:

NAME Description
RACK_ENV The Ruby application environment. (Default: "production")


Build Customization

Asset Compilation

When your app is running in RACK_ENV=production, the asset compilation task will be run by default.

If you wish to skip this process you may set the following environment variable:

NAME Description
DISABLE_ASSET_COMPILATION Set this variable to TRUE will skip the asset compilation process.

Configuring bundler

If you would like to use a custom rubygem mirror you may use the following environment variable:

NAME Description
RUBYGEM_MIRROR Set this variable to use a custom RubyGems mirror URL to download required gem packages during build process.

Using Puma

Configuring Puma

By default the builder will check to see if ./config/puma.rb exists. If it does not exist the default builder provided config will be used.

You may alternatively specify another location for your puma config:

Name Description
PUMA_CONFIG Path to your puma.rb config file.

Application Concurrency

If you are using the builder provided (fallback) Puma config we automatically tune the number of workers for you based on the app instance size.

Size Value
Small 2 Workers
Medium 4 Workers
Large 8 Workers
2xLarge 16 Workers

You may optionally change these default settings by configuring the following environment variable:

NAME Description
WEB_CONCURRENCY Set the number of Puma workers. By default, it is calculated as above.

If you are not using the default Puma config the calculated WEB_CONCURRENCY variable is still made available to you.


AusNimbus builders are split into two stages:

  • Build
  • Runtime

Both stages are completely extensible, allowing you to customize or completely overwrite each stage.

Build Stage (assemble)

If you want to customize the build stage, you need to add the executable .s2i/bin/assemble file in your repository.

This file should contain the logic required to build and install any dependencies your application requires.

If you only want to extend the build stage, you may use this example:


echo "Logic to include before"

# Run the default builder logic
. /usr/libexec/s2i/assemble

echo "Logic to include after"

Runtime Stage (run)

If you only want to change the executed command for the run stage you may the following environment variable.

NAME Description
APP_RUN Define a custom command to start your application. eg. rack --host --port 8080

NOTE: APP_RUN will overwrite any builder's runtime configuration (including the Debug Mode section)

Alternatively you may customize or overwrite the entire runtime stage by including the executable file .s2i/bin/run

This file should contain the logic required to execute your application.

If you only want to extend the run stage, you may use this example:


echo "Logic to include before"

# Run the default builder logic
. /usr/libexec/s2i/run

As the run script executes every time your application is deployed, scaled or restarted it's recommended to keep avoid including complex logic which may delay the start-up process of your application.

Persistent Environment Variables

The recommend approach is to set your environment variables in the AusNimbus dashboard.

However it is possible to store environment variables in code using the .s2i/environment file.

The file expects a key=value format eg.


Debug Mode

The AusNimbus builder provides a convenient environment variable to help you debug your application.

NAME Description
DEBUG Set to TRUE will enable common debug settings


Why aren't my changes being picked up

In order to dynamically pick up changes made in your application source code, you need to make following steps:

Ruby on Rails applications

Run the built Rails application with the RAILS_ENV=development or DEBUG=true environment variable

For other types of Ruby applications (Sinatra, Padrino, etc.)

Your application needs to be built with one of gems that reloads the server every time changes in source code are done. Some examples are:

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