# Configuring Blackfire Continuous Profiler for Ruby

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[configuring continuous profiling](https://www.youtube-nocookie.com/embed/1q_E6fk2Q1Q?rel=0&showinfo=0&modestbranding=1&autoplay=0)

The Ruby continuous profiling is currently made across 3 dimensions:

- **CPU Time**: Time spent running on the CPU
- **Wall-time**: elapsed time per function call
- **Allocations**: Number of objects allocated

## Requirements

- Ruby >= 2.5
- [Blackfire Agent](../up-and-running/configuration/agent) >= 2.13.0

## Installation

1. Add the `datadog` gem to your `Gemfile` or `gems.rb` file:

    ```bash
    gem 'datadog', '~> 2.0'
    ```

    > **Note**
    >
    > Blackfire utilizes the open source Datadog profiler to collect continuous profiling traces and, via its [agent](../reference-guide/glossary#term-agent), sends it directly to Blackfire's ingesters where we process and analyze the data for your observability needs.
2. Install the gems running the `bundle install` command.
3. Enable the Ruby Continuous Profiler by defining these environment variables:

    - `DD_PROFILING_ENABLED=true`: controls the activation of the continuous profiler.
    - `DD_SERVICE=my-ruby-app`: sets the application name.
    - `DD_PROFILING_ALLOCATION_ENABLED=true`: enables allocation profiling
    - **`DD_TRACE_AGENT_URL=unix:///var/run/blackfire/agent.sock`: has Blackfire**

         Agent collect traces.
4. Add the `ddprofrb exec` command to your Ruby application start command:

    ```bash
    bundle exec ddprofrb exec ruby myrubyapp.rb
    
    # Rails example
    bundle exec ddprofrb exec bin/rails s
    ```

> **Note**
>
> Alternatively, start the profiler by adding the following code in your application's entry point if you can't start it using `ddprofrb exec`:
>
> ```bash
> require 'datadog/profiling/preload'
> ```

There is also some additional configuration that can be done using environment variables:

- `BLACKFIRE_LOG_FILE`: Sets the log file. The default is logging to `stderr`.
- `BLACKFIRE_LOG_LEVEL`: Sets the log level. The default is logging only errors.