The New Relic Ruby agent requires the gem newrelic_rpm, and it includes distributed tracing that uses head-based sampling (standard distributed tracing). If you want distributed tracing to use tail-based sampling (Infinite Tracing), you need to add both newrelic_rpm and newrelic-infinite_tracing to your application's Gemfile. For more information, see: https://docs.newrelic.com/docs/understand-dependencies/distributed-tracing/get-started/introduction-distributed-tracing New Relic is a performance management system, developed by New Relic, Inc (http://www.newrelic.com). New Relic provides you with deep information about the performance of your web application as it runs in production. The New Relic Ruby agent is dual-purposed as a either a Gem or plugin, hosted on https://github.com/newrelic/newrelic-ruby-agent/