Stackdriver Debugger

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:

  • 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.
  • An idiomatic Ruby API for registerying debuggee application, and querying or manipulating breakpoints in registered Ruby debuggee application. See Debugger API section for an introduction to Stackdriver Debugger API.

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.

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. The Railtie also takes in the following Rails configuration as parameter of the debugger agent initialization:

# Explicitly enable or disable Stackdriver Debugger Agent
config.google_cloud.use_debugger = true
# Shared Google Cloud Platform project identifier
config.google_cloud.project_id = "gcloud-project"
# Google Cloud Platform project identifier for Stackdriver Debugger only
config.google_cloud.debugger.project_id = "debugger-project"
# Shared Google Cloud authentication json file
config.google_cloud.