Documentation for: v1.0.4 v2.2.1

Web Console

Web Console is a debugging tool for your Ruby on Rails applications.

• Installation
• Configuration
• Usage
• FAQ
• Credits

Installation

Add the following to your Gemfile:

group :development do
  gem 'web-console'
end

Usage

The web console allows you to create an interactive Ruby session in your browser. Those sessions are launched automatically in case of an error and can also be launched manually in any page.

For example, calling console in a view will display a console in the current page in the context of the view binding.

<% console %>

Calling console in a controller will result in a console in the context of the controller action:

class PostsController < ApplicationController
  def new
    console
    @post = Post.new
  end
end

The method is defined in Kernel and you can invoke it any application code.

Only one console invocation per request is allowed. If you happen to have multiple ones, WebConsole::DoubleRenderError will be raised.

Configuration

Web Console allows you to execute arbitrary code on the server. Therefore, be very careful who you give access to.

config.web_console.permissions

By default, only requests coming from IPv4 and IPv6 localhosts are allowed.

config.web_console.permissions lets you control which IP's have access to the console.

You can whitelist single IP's or whole networks. Say you want to share your console with 192.168.0.100:

class Application < Rails::Application
  config.web_console.permissions = '192.168.0.100'
end

If you want to whitelist the whole private network:

Rails.application.configure do
  config.web_console.permissions = '192.168.0.0/16'
end

Take a note that IPv4 and IPv6 localhosts are always allowed. This wasn't the case in 2.0.

config.web_console.whiny_requests

When a console cannot be shown for a given IP address or content type, messages such as the following is printed in the server logs:

Cannot render console from 192.168.1.133! Allowed networks: 127.0.0.0/127.255.255.255, ::1

If you don't want to see this message anymore, set this option to false:

Rails.application.configure do
  config.web_console.whiny_requests = false
end

config.web_console.template_paths

If you want to style the console yourself, then you can place style.css at a directory pointed by config.web_console.template_paths:

Rails.application.configure do
  config.web_console.template_paths = 'app/views/web_console'
end

You may want to check the templates folder at the source tree for the files you may override.

config.web_console.mount_point

Usually the middleware of Web Console is mounted at /__web_console. If there is a need to change the path, then you can specify it by config.web_console.mount_point:

Rails.application.configure do
  config.web_console.mount_point = '/path/to/web_console'
end

FAQ

Where did /console go?

The remote terminal emulator was extracted in its own gem which is no longer bundled with Web Console.

If you miss this feature, check out rvt.

Why do I constantly get unavailable session errors?

All of Web Console sessions are stored in memory. If you happen to run on a multi-process server (like Unicorn), you may encounter unavailable session errors while the server is still running. This is because a request may hit a different worker (process) that doesn't have the desired session in memory. To avoid that, if you use such servers in development, configure them so they serve requests only out of one process.

Passenger

Enable sticky sessions for Passenger on Nginx or Passenger on Apache to prevent unavailable session errors.

How to inspect local and instance variables?

The interactive console executes Ruby code. Invoking instance_variables and local_variables will give you what you want.

Why does the console only appear on error pages but not when I call it?

This can be happening if you are using Rack::Deflater. Be sure that WebConsole::Middleware is used after Rack::Deflater. The easiest way to do this is to insert Rack::Deflater as early as possible

Rails.application.configure do
  config.middleware.insert(0, Rack::Deflater)
end

Why am I getting an undefined method web_console?

Make sure your configuration lives in config/environments/development.rb.

Credits

• Shoutout to Charlie Somerville for better_errors.
• Kudos to John Mair for binding_of_caller and debug_inspector.
• Thanks to Charles Oliver Nutter for all the JRuby feedback.
• Hugs and kisses to all of our contributors!