Allow usage with Rails 3

README.md

@@ -1,41 +1,36 @@
 # ActiveRecord::AllowConnectionFailure
 
-Welcome to your new gem! In this directory, you'll find the files you need to be able to package up your Ruby library into a gem. Put your Ruby code in the file `lib/active_record/allow_connection_failure`. To experiment with that code, run `bin/console` for an interactive prompt.
+This gem monkeypatches methods inside of `ActiveRecord::QueryCache` and
+`ActiveRecord::Migration::CheckPending`.
 
-TODO: Delete this and the text above, and describe your gem
+The intention is to allow a Rails application to boot without first establishing
+a database connection, enabling AR's query caching mechanism, and checking for
+any pending migrations.
 
-## Installation
+In practice, this is useful for situations in which you want to boot your app
+and check e.g. a `/status` endpoint which does not have a database/ORM
+(read: `ActiveRecord`) dependency.
 
-Add this line to your application's Gemfile:
+## Associated `Rails` PR
 
-```ruby
-gem 'active_record-allow_connection_failure'
-```
-
-And then execute:
-
-    $ bundle
-
-Or install it yourself as:
-
-    $ gem install active_record-allow_connection_failure
+For additional context, see the associated Rails
+[pull request](https://github.com/rails/rails/issues/22154).
 
 ## Usage
 
-TODO: Write usage instructions here
+Add this gem to your `Gemfile`:
 
-## Development
-
-After checking out the repo, run `bin/setup` to install dependencies. Then, run `rake spec` to run the tests. You can also run `bin/console` for an interactive prompt that will allow you to experiment.
-
-To install this gem onto your local machine, run `bundle exec rake install`. To release a new version, update the version number in `version.rb`, and then run `bundle exec rake release`, which will create a git tag for the version, push git commits and tags, and push the `.gem` file to [rubygems.org](https://rubygems.org).
+```ruby
+gem 'active_record-allow_connection_failure'
+```
 
 ## Contributing
 
-Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/active_record-allow_connection_failure. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the [Contributor Covenant](http://contributor-covenant.org) code of conduct.
-
+Bug reports and pull requests are welcome on GitHub at
+https://github.com/zipmark/active_record-allow_connection_failure. This project
+is intended to be a safe, welcoming space for collaboration, and contributors
+are expected to adhere to the [Contributor Covenant](http://contributor-covenant.org) code of conduct.
 
 ## License
 
 The gem is available as open source under the terms of the [MIT License](http://opensource.org/licenses/MIT).
-

active_record-allow_connection_failure.gemspec

@@ -20,8 +20,8 @@ Gem::Specification.new do |spec|
   spec.require_paths = ["lib"]
 
   spec.add_development_dependency "bundler", "~> 1.11"
-  spec.add_development_dependency "rake", "~> 10.0"
-  spec.add_development_dependency "rspec", "~> 3.0"
+  spec.add_development_dependency "rake",    "~> 10.0"
+  spec.add_development_dependency "rspec",   "~> 3.0"
 
-  spec.add_runtime_dependency     "rails", ">= 4.2"
+  spec.add_runtime_dependency     "rails", ">= 3.2"
 end

lib/active_record/allow_connection_failure.rb

@@ -5,51 +5,95 @@
 module ActiveRecord
   module AllowConnectionFailure
     # monkeypatches activerecord/lib/active_record/query_cache.rb
-    ActiveRecord::QueryCache.class_eval do
-      def self.run
-        if ActiveRecord::Base.connected?
-          connection    = ActiveRecord::Base.connection
-          enabled       = connection.query_cache_enabled
-          connection_id = ActiveRecord::Base.connection_id
-          connection.enable_query_cache!
-
-          [enabled, connection_id]
+    if Rails::VERSION::MAJOR == 3
+      ActiveRecord::QueryCache::BodyProxy.class_eval do
+        def close
+          @target.close if @target.respond_to?(:close)
+        ensure
+          ActiveRecord::Base.connection_id = @connection_id
+          if ActiveRecord::Base.connected?
+            ActiveRecord::Base.connection.clear_query_cache
+            unless @original_cache_value
+              ActiveRecord::Base.connection.disable_query_cache!
+            end
+          end
         end
       end
 
-      def self.complete(state)
-        if ActiveRecord::Base.connected?
-          enabled, connection_id = state
-
-          ActiveRecord::Base.connection_id = connection_id
-          ActiveRecord::Base.connection.clear_query_cache
-          ActiveRecord::Base.connection.disable_query_cache! unless enabled
+      ActiveRecord::QueryCache.class_eval do
+        def call(env)
+          begin
+            if ActiveRecord::Base.connected?
+              old = ActiveRecord::Base.connection.query_cache_enabled
+              ActiveRecord::Base.connection.enable_query_cache!
+            end
+
+            status, headers, body = @app.call(env)
+            [status, headers, ActiveRecord::QueryCache::BodyProxy.new(old, body, ActiveRecord::Base.connection_id)]
+          rescue Exception => e
+            raise e.inspect
+            ActiveRecord::Base.connection.clear_query_cache
+            unless old
+              ActiveRecord::Base.connection.disable_query_cache!
+            end
+            raise e
+          end
         end
       end
+
+      ActiveRecord::ModelSchema::ClassMethods.module_eval do
+        def clear_cache! # :nodoc:
+          connection.schema_cache.clear! if connected?
+        end
+      end
+    end
+
+    if Rails::VERSION::MAJOR >= 4
+      ActiveRecord::QueryCache.class_eval do
+        def self.run
+          if ActiveRecord::Base.connected?
+            connection    = ActiveRecord::Base.connection
+            enabled       = connection.query_cache_enabled
+            connection_id = ActiveRecord::Base.connection_id
+            connection.enable_query_cache!
 
-      def self.install_executor_hooks(executor = ActiveSupport::Executor)
-        executor.register_hook(self)
+            [enabled, connection_id]
+          end
+        end
+
+        def self.complete(state)
+          if ActiveRecord::Base.connected?
+            enabled, connection_id = state
 
-        executor.to_complete do
-          unless ActiveRecord::Base.connected? && ActiveRecord::Base.connection.transaction_open?
-            ActiveRecord::Base.clear_active_connections!
+            ActiveRecord::Base.connection_id = connection_id
+            ActiveRecord::Base.connection.clear_query_cache
+            ActiveRecord::Base.connection.disable_query_cache! unless enabled
           end
         end
-      end
-    end
 
-    # monkeypatches activerecord/lib/active_record/migration.rb
-    ActiveRecord::Migration::CheckPending.class_eval do
-      def call(env)
-        if ActiveRecord::Base.connected? && connection.supports_migrations?
-          mtime = ActiveRecord::Migrator.last_migration.mtime.to_i
-          if @last_check < mtime
-            ActiveRecord::Migration.check_pending!(connection)
-            @last_check = mtime
+        def self.install_executor_hooks(executor = ActiveSupport::Executor)
+          executor.register_hook(self)
+
+          executor.to_complete do
+            unless ActiveRecord::Base.connected? && ActiveRecord::Base.connection.transaction_open?
+              ActiveRecord::Base.clear_active_connections!
+            end
           end
         end
-        @app.call(env)
       end
-    end
-  end
+
+      ActiveRecord::Migration::CheckPending.class_eval do
+       def call(env)
+         if ActiveRecord::Base.connected? && connection.supports_migrations?
+           mtime = ActiveRecord::Migrator.last_migration.mtime.to_i
+           if @last_check < mtime
+             ActiveRecord::Migration.check_pending!(connection)
+             @last_check = mtime
+           end
+         end
+         @app.call(env)
+       end
+     end
+   end
+ end
 end