Rails ReadOnly Injector

Build Status Read the Docs Maintainability Test Coverage Gem Version

Easily switch a Rails site into 'read-only' mode, and back again, without restarting the server.


Add this line to your application's Gemfile:

gem 'rails_readonly_injector'

And then execute:

$ bundle

Or install it yourself as:

$ gem install rails_readonly_injector


In order to switch a complete site into read-only mode, you will first need to set the action to occur when an attempt to commit changes to the database is made, from within a controller. This action will be executed from within the context of the referring controller.

Usually, this won't need to change once the application has booted, so I recommend defining it within an initializer, as follows:

# config/initializers/rails_readonly_injector.rb
RailsReadonlyInjector.config do |config|
  config.controller_rescue_action = lambda do |context|
    # Define actions to be performed if changes to a read-only model are attempted to be committed to the database.
    # This lambda expression is evaluated from within the context of the referring controller.

    # You may want to set a redirect, or flash an error message, or something, here.
    # e.g.
    # flash[:danger] = 'The site is currently in read-only mode'
    # redirect_to readonly_page_url

When you want to switch a site into read-only mode, you can then simply

  • set RailsReadOnlyInjector.config.read_only to true, and then
  • call RailsReadonlyInjector.reload! to (re-)load the configuration.

Alternatively, you can also set read_only from within the configuration block inside the initializer.

If you want to reset the configuration to the defaults, you can simply call RailsReadonlyInjector.reset_configuration! from anywhere in your application.

If you want to check whether read-only mode is currently enabled, you can use RailsReadonlyInjector.in_read_only_mode?.

Configuration Options

The following configuration options can be set through RailsReadonlyInjector.config:

  • read_only => Whether the site should be in read-only mode. (Default: false)
  • classes_to_exclude => An array of classes that should be exempt from read-only mode. (Default: [])
  • classes_to_include => An array of classes that should be set to read-only mode. (Defaults to ActiveRecord::Base.descendants on Rails 3-4, and ApplicationRecord.descendants on Rails 5.0+)
  • controller_rescue_action => A lambda expression/Proc to execute when an ActiveRecord::ReadOnlyRecord error is raised, from within a controller.


After checking out the repo, run bundle install to install the dependencies.

RSpec specs and Cucumber features are stored in rspec_specs and cucumber_features, respectively. When bundle exec rake is run against an appraisal, the contents of these folders are copied to the necessary folders under the temporary rails application that bundle exec rake generates into tmp/rails_app.

To run tests for a specific version of Rails, simply run bundle exec appraisal {APPRAISAL} bundle exec rake, where {APPRAISAL} is one of the appraisals found under Appraisals. e.g. bundle exec appraisal rails_4_1 bundle exec rake

If you don't want to re-build the temporary application each time you run tests, you can execute the following rake tasks against an appraisal:

  • dev:run_features => Synchronises features from cucumber_features into the temporary rails application, and runs cucumber against the temporary application.
  • dev:run_specs => Synchronises specs from rspec_specs into the temporary rails application, and runs rspec against the temporary application.
  • dev:run_tests => Runs both dev:run_features and dev:run_specs, and ret on failure.


Bug reports and pull requests are welcome on GitHub at https://github.com/xtrasimplicity/rails_readonly_injector. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.


The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the RailsReadonlyInjector project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.