Stackdriver Debugger Instrumentation

Stackdriver Debugger is a feature of the Google Cloud Platform that lets you inspect the state of an application at any code location without using logging statements and without stopping or slowing down your applications. Your users are not impacted during debugging. Using the production debugger you can capture the local variables and call stack and link it back to a specific line location in your source code. You can use this to analyze the production state of your application and understand the behavior of your code in production.

For general information about Stackdriver Debugger, read Stackdriver Debugger Documentation.

The Stackdriver Debugger Ruby library, google-cloud-debugger, provides an easy-to-use debugger instrumentation that reports state data, such as value of program variables and the call stack, to Stackdriver Debugger when the code at a breakpoint location is executed in your Ruby application. See the instrumenting your app section for how to debug your application, in both development and production.

Instrumenting Your App

This instrumentation library provides the following features to help you debug your applications in production:

  • Automatic application registration. It facilitates multiple running instances of same version of application when hosted in production.
  • A background debugger agent that runs side-by-side with your application that automatically collects state data when code is executed at breakpoint locations.
  • A Rack middleware and Railtie that automatically manages the debugger agent for Ruby on Rails and other Rack-based Ruby applications.

When this library is configured in your running application, and the source code and breakpoints are setup through the Google Cloud Console, You'll be able to interact with your application in real time through the Stackdriver Debugger UI. This library also integrates with Google App Engine Flexible to make debuggee application configuration more seemless.

Note that when no breakpoints are created, the debugger agent consumes very little resource and has no interference with the running application. Once breakpoints are created and depends on where the breakpoints are located, the debugger agent may add a little latency onto each request. The application performance will be back to normal after all breakpoints are finished being evaluated. Be aware the more breakpoints are created, or the harder to reach the breakpoints, the more resource the debugger agent would need to consume.


The default configuration enables Stackdriver instrumentation features to run on Google Cloud Platform. You can easily configure the instrumentation library if you want to run on a non Google Cloud environment or you want to customize the default behavior.

See the Configuration Guide for full configuration parameters.

Using instrumentation with Ruby on Rails

To install application instrumentation in your Ruby on Rails app, add this gem, google-cloud-debugger, to your Gemfile and update your bundle. Then add the following line to your config/application.rb file:

require "google/cloud/debugger/rails"

This will load a Railtie that automatically integrates with the Rails framework by injecting a Rack middleware.

Using instrumentation with Sinatra

To install application instrumentation in your Sinatra app, add this gem, google-cloud-debugger, to your Gemfile and update your bundle. Then add the following lines to your main application Ruby file:

require "google/cloud/debugger"
use Google::Cloud::Debugger::Middleware

This will install the debugger middleware in your application.

Using instrumentation with other Rack-based frameworks

To install application instrumentation in an app using another Rack-based web framework, add this gem, google-cloud-debugger, to your Gemfile and update your bundle. Then add install the debugger middleware in your middleware stack. In most cases, this means adding these lines to your Rack configuration file:

require "google/cloud/debugger"
use Google::Cloud::Debugger::Middleware

Some web frameworks have an alternate mechanism for modifying the middleware stack. Consult your web framework's documentation for more information.

The Stackdriver diagnostics suite

The debugger library is part of the Stackdriver diagnostics suite, which also includes error reporting, log analysis, and tracing analysis. If you include the stackdriver gem in your Gemfile, this debugger library will be included automatically. In addition, if you include the stackdriver gem in an application using Ruby On Rails, the Railties will be installed automatically. See the documentation for the "stackdriver" gem for more details.