The RPM Contrib Gem

The rpm_contrib gem contains instrumentation for the New Relic RPM agent contributed by the community of RPM users. It requires the RPM Agent to run.

To use the contrib gem, install the rpm_contrib gem from gemcutter. It will also install the required version of the newrelic_rpm gem if it's not already installed.

For Rails 2.1 and later, add this dependency to your in your environment.rb:

config.gem 'rpm_contrib'

For other frameworks, make sure you load rubygems if it isn't already, then just require the contrib gem:

require 'rubygems'
require 'rpm_contrib'

When you load the rpm_contrib gem, the newrelic_rpm gem will also be initialized. No need for a separate require statement for newrelic_rpm. The rpm_contrib gem must be loaded before the newrelic_rpm gem initializes.

Supported Frameworks

A number of frameworks are supported in the contrib gem. They are all turned on by default but you can add settings to your newrelic.yml to disable any of them.

Camping

Paperclip

Authlogic

MongoDB

Resque

To disable resque, add this to your newrelic.yml:

disable_resque: true

How to Add Custom Instrumentation

We encourage contributions to this project and will provide whatever assistance we can to those wishing to develop instrumentation for other open source Ruby libraries.

When adding instrumentation to this gem, be sure and get familiar with the RPM Agent API and contact [email protected] with any questions.

There are several extension points in the agent you can take advantage of with this gem.

Custom tracers which measure methods and give visibility to otherwise unmeasured libraries.
Samplers which sample some value about once a minute.
Dispatcher support for web request handlers which would otherwise be undetected. In order for the agent to turn on in 'auto' mode it needs to discover a web dispatcher, or be started manually.
Framework support, for alternatives to Rails like Camping or Ramaze

Custom Tracers

Custom tracers for frameworks should be added to the lib/rpm_contrib/instrumentation directory. These files are loaded at the time the Agent starts. They will not be loaded if the Agent does not start up.

It is important that you wrap any instrumentation with the checks necessary to determine if the code being instrumented is loaded. You can't add code to the contrib gem that will break when run in any other context besides yours.

For details on how to define custom tracers, refer to the support documentation on adding custom tracers. You can also get detailed information on the API from the Agent method tracing rdocs, especially the add_method_tracer docs.

A good example can be found in lib/rpm_contrib/instrumentation/paperclip.rb.

Samplers

You can add samplers which will record metrics approximately once a minute. Samplers are useful for capturing generic instrumentation for display in custom views.

Samplers should extend the NewRelic::Agent::Sampler class. They should be placed in the samplers directory.

Refer to examples in the RPM agent to see how to get started.

Supporting New Dispatchers

If you want to add support for a new dispatcher which is not being recognized by default by the RPM agent, add code to the rpm_contrib/detection directory. This code needs to define a module in the NewRelic::LocalEnvironment class. This module will be accessed at the time environment detection takes place, when the agent is initialized.

This module should define the method discover_dispatcher and return the name of the dispatcher if detected, or defer to super. See rpm_contrib/detection/camping.rb for a good example.

Supporting New Frameworks

Supporting new frameworks can be pretty involved and generally involves both adding custom instrumentation as well as framework and dispatcher detection.

In addition it will be necessary to define a new control class with the same name as the framework. This control class must go in new_relic/control.

Refer to the camping example in this gem to see how this is done in general.

If you decide to tackle any new frameworks, contact [email protected] and we'll be happy to help you work through it.

Note on Patches/Pull Requests

Fork the http://www.github.com/newrelic/rpm_contrib project.
Add instrumentation files to lib/rpm_contrib/instrumentation. These files will be loaded when the RPM agent is initialized.
Add samplers to lib/rpm_contrib/samplers. These classes are installed automatically when the RPM agent is initialized.
Add tests.
Commit, do not mess with the Rakefile, version, or history. (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)
Send me a pull request. Bonus points for topic branches.

Further Information

Refer to the Agent API Documentation.

See the support site for additional tips and documentation.

Contact [email protected] for help.