---
title: Rack and Metal support
source: https://docs.newrelic.com/docs/apm/agents/ruby-agent/frameworks/rack-metal-support
---

[Rack middlewares](https://docs.newrelic.com/docs/agents/ruby-agent/frameworks/rack-middlewares) are automatically instrumented with Ruby agent version 3.9.0 or higher.

The `NewRelic::Agent::Instrumentation::Rack` module is deprecated. After upgrading to Ruby agent version 3.9.0 or higher, New Relic recommends that you remove any references to this module from your code. For more information, see [Instrumenting Metal controllers](https://docs.newrelic.com/docs/agents/ruby-agent/frameworks/instrumenting-metal-controllers).