OpenTelemetry ActionPack Instrumentation

The Action Pack instrumentation is a community-maintained instrumentation for the Action Pack portion of the [Ruby on Rails][rails-home] web-application framework.

How do I get started?

Install the gem using:

gem install opentelemetry-instrumentation-action_pack

Or, if you use bundler, include opentelemetry-instrumentation-action_pack in your Gemfile.


To use the instrumentation, call use with the name of the instrumentation:

OpenTelemetry::SDK.configure do |c|
  c.use 'OpenTelemetry::Instrumentation::ActionPack'

Alternatively, you can also call use_all to install all the available instrumentation.

OpenTelemetry::SDK.configure do |c|

Active Support Instrumentation

Earlier versions of this instrumentation relied on patching custom dispatch hooks from Rails's Action Controller to extract request information.

This instrumentation now relies on ActiveSupport::Notifications and registers a custom Subscriber that listens to relevant events to modify the Rack span.

See the table below for details of what Rails Framework Hook Events are recorded by this instrumentation:

Event Name Subscribe? Creates Span? Notes
process_action.action_controller :white_check_mark: :x: It modifies the existing Rack span

Error Handling for Action Controller

If an error is triggered by Action Controller (such as a 500 internal server error), Action Pack will typically employ the default as the exceptions_app, as detailed in the documentation.

The error object will be retained within payload[:exception_object]. Additionally, its storage in request.env['action_dispatch.exception'] is contingent upon the configuration of action_dispatch.show_exceptions in Rails.


Example usage can be seen in the ./example/trace_demonstration.rb file here

How can I get involved?

The opentelemetry-instrumentation-action_pack gem source is on github, along with related gems including opentelemetry-api and opentelemetry-sdk.

The OpenTelemetry Ruby gems are maintained by the OpenTelemetry-Ruby special interest group (SIG). You can get involved by joining us in GitHub Discussions or attending our weekly meeting. See the meeting calendar for dates and times. For more information on this and other language SIGs, see the OpenTelemetry community page.


The opentelemetry-instrumentation-action_pack gem is distributed under the Apache 2.0 license. See LICENSE for more information.