Ruby on Rails

Packrat monitors your Ruby on Rails application deploys, creating a verification plan and validating that it performs as intended in production. This guide walks through the Packrat setup for a Rails application.

The packrat-rails gem sets up OpenTelemetry in your app and sends its exceptions, traces and logs to Packrat. It supports Rails 7.1 and newer.

Already running Datadog's tracer? Dual-ship from the Datadog Agent.

Prerequisites

1. Sign up for Packrat. It's free.

2. Copy your ingest key from the setup page. It starts with packrat_ingest_.

3. Install the Packrat CLI and sign in, so you can check what Packrat receives:

   curl -fsSL https://packrat.sh/cli | sh
   packrat login
   

Install the gem

1. Add packrat-rails

bundle add packrat-rails

2. Run the generator

bin/rails generate packrat --ingest-key=packrat_ingest_…

The generator creates config/initializers/packrat.rb:

Packrat.configure do |config|
  config.ingest_key = ENV.fetch("PACKRAT_INGEST_KEY", "packrat_ingest_…")
end

An ingest key can only send data, so you can commit the file. To keep the key out of the repository, run the generator without --ingest-key and set a PACKRAT_INGEST_KEY environment variable where the app runs.

The generator also adds the Packrat plugin for Claude Code to your repository's .claude/settings.json. Commit the file, and anyone who opens Claude Code in the repository gets the plugin. To skip this, pass --no-claude-code.

3. Restart the app

When the app boots, the gem writes one line to the Rails log. It names the service and environment your data arrives under:

Packrat: sending traces and logs for shop/production to https://ingest.packrat.sh (rack, action_pack, active_job, active_record, net_http, pg, logger)

The gem sends nothing from the test environment.

Check it works

Load a page. The first request reaches your setup screen within about a minute.

Run packrat status with your app's name, as <service>/<environment>:

packrat status --app shop/production

The output lists each signal (exceptions, traces, logs, metrics and replays), the sources that send it, when each source last sent, and whether Packrat keeps it. A signal with no source hasn't arrived yet. To see the names your apps report under, run packrat apps.

If nothing arrives, the quickstart lists what usually causes it.

Configuration

Packrat.configure sets the ingest key. Everything else is an environment variable:

The gem installs these instrumentations: rack, action_pack, action_view, active_job, active_record, net_http, pg, mysql2, sidekiq, redis, aws_sdk, concurrent_ruby, rake and logger. One for a library your app doesn't use installs nothing. For example, PACKRAT_OTEL_INSTRUMENTATIONS=faraday,-action_view adds Faraday (add opentelemetry-instrumentation-faraday to your bundle too) and removes Action View.

Your app's name in Packrat is <service>/<environment>:

• Service: OTEL_SERVICE_NAME, else service.name in OTEL_RESOURCE_ATTRIBUTES, else the application's module name (Shop::Application is shop).
• Environment: Rails.env, unless OTEL_RESOURCE_ATTRIBUTES names one.
• Version: BUILD_COMMIT, HEROKU_SLUG_COMMIT or SOURCE_VERSION. Packrat matches it to your deploys.

A standard OTEL_* variable that you set always wins over the gem's value.

Beside other tools

• Sentry: both run, and the gem doesn't change Sentry. If Sentry also dual-ships to Packrat, Packrat keeps exceptions and traces from whichever source sent them first. packrat status shows which.
• Your own OpenTelemetry setup: the gem leaves it as it is and adds a second exporter, to Packrat. If your exporter already sends to Packrat, the gem adds nothing.
• Session replays come from Sentry's browser SDK, whatever runs on your server. Follow the Sentry browser guide.

To configure OpenTelemetry yourself instead of using the gem, follow the Rails tab of the OpenTelemetry guide.