Using Ruby gems

If you have server-side Ruby code in your modules, Puppet Server will run it via JRuby. Generally speaking, this only affects custom parser functions, types, and report processors. For the vast majority of cases this shouldn't pose any problems because JRuby is highly compatible with vanilla Ruby.

Puppet Server will not load gems from user specified GEM_HOME and GEM_PATH environment variables because puppetserver unsets GEM_PATH and manages GEM_HOME.

Note: Starting with Puppet Server 2.7.1, you can set custom Java arguments for the puppetserver gem command via the JAVA_ARGS_CLI environment variable, either temporarily on the command line or persistently by adding it to the sysconfig/default file. The JAVA_ARGS_CLI environment variable also controls the arguments used when running the puppetserver ruby and puppetserver irb subcommands. See the Server 2.7.1 release notes for details.

GEM_HOME values

Gems with packaged versions of Puppet Server

The value of GEM_HOME when starting the puppetserver process as root using a packaged version of puppetserver is:


This directory does not exist by default.

Gems when running Puppet Server from source

The value of GEM_HOME when starting the puppetserver process from the project root is:


Gems when running Puppet Server spec tests

The value of GEM_HOME when starting the puppetserver JRuby spec tests using rake spec from the project root is:


This directory is automatically populated by the rake spec task if it does not already exist. The directory may be safely removed and it will be re-populated the next time rake spec is run in your working copy.

Installing and removing gems

We isolate the Ruby load paths that are accessible to Puppet Server's JRuby interpreter, so that it doesn't load any gems or other code that you have installed on your system Ruby. If you want Puppet Server to load additional gems, use the Puppet Server-specific gem command to install them:

$ sudo puppetserver gem install <GEM NAME> --no-document

The puppetserver gem command is simply a wrapper around the usual Ruby gem command, so all of the usual arguments and flags should work as expected. For example, to show your locally installed gems, run:

$ puppetserver gem list

Or, if you're running from source:

$ lein gem -c ~/.puppetserver/puppetserver.conf list

The puppetserver gem command also respects the running user's ~/.gemrc file, which you can use to configure upstream sources or proxy settings. For example, consider a .gemrc file containing:

:sources: [ '', '' ]
http_proxy: ""

This configures the listed :sources as the puppetserver gem command's upstream sources, and uses the listed http_proxy, which you can confirm:

$ puppetserver gem environment | grep proxy
    - "http_proxy" => ""

As with the rest of Puppet Server's configuration, we recommend managing these settings with Puppet. You can manage Puppet Server's gem dependencies with the package provider shipped in puppetlabs-puppetserver_gem module.

Note: If you try to load a gem before it's been installed, the agent run will fail with a LoadError. If this happens, reload the server after installing the gem to resolve the issue.

Installing gems for use with development:

When running from source, JRuby uses a GEM_HOME of ./target/jruby-gems relative to the current working directory of the process. lein gem should be used to install gems into this location using jruby.

NOTE: ./target/jruby-gems is not used when running the JRuby spec tests, gems are instead automatically installed into and loaded from ./vendor/test_gems. If you need to install a gem for use both during development and testing make sure the gem is available in both directories.

As an example, the following command installs pry locally in the project. Note the use of -- to pass the following command line arguments to the gem script.

$ lein gem --config ~/.puppetserver/puppetserver.conf -- install pry \
Fetching: coderay-1.1.0.gem (100%)
Successfully installed coderay-1.1.0
Fetching: slop-3.6.0.gem (100%)
Successfully installed slop-3.6.0
Fetching: method_source-0.8.2.gem (100%)
Successfully installed method_source-0.8.2
Fetching: spoon-0.0.4.gem (100%)
Successfully installed spoon-0.0.4
Fetching: pry-0.10.1-java.gem (100%)
Successfully installed pry-0.10.1-java
5 gems installed

With the gem installed into the project tree pry can be invoked from inside Ruby code. For more detailed information on pry see Puppet Server: Debugging.

Gems with Native (C) Extensions

If, in your custom parser functions or report processors, you're using Ruby gems that require native (C) extensions, you won't be able to install these gems under JRuby. In many cases, however, there are drop-in replacements implemented in Java. For example, the popular Nokogiri gem for processing XML provides a completely compatible Java implementation that's automatically installed if you run gem install via JRuby or Puppet Server, so you shouldn't need to change your code at all.

In other cases, there may be a replacement gem available with a slightly different name; e.g., jdbc-mysql instead of mysql. The JRuby wiki C Extension Alternatives page discusses this issue further.

If you're using a gem that won't run on JRuby and you can't find a suitable replacement, please open a ticket on our Issue Tracker; we're definitely interested in helping provide solutions if there are common gems that are causing trouble for users!