1 files changed, 52 insertions, 0 deletions
diff --git a/actionpack/lib/action_dispatch/middleware/failsafe.rb b/actionpack/lib/action_dispatch/middleware/failsafe.rb
new file mode 100644
index 0000000000..7379a696aa
--- /dev/null
+++ b/actionpack/lib/action_dispatch/middleware/failsafe.rb
@@ -0,0 +1,52 @@
+module ActionDispatch
+  class Failsafe
+    cattr_accessor :error_file_path
+    self.error_file_path = Rails.public_path if defined?(Rails.public_path)
+
+    def initialize(app)
+      @app = app
+    end
+
+    def call(env)
+      @app.call(env)
+    rescue Exception => exception
+      # Reraise exception in test environment
+      if env["rack.test"]
+        raise exception
+      else
+        failsafe_response(exception)
+      end
+    end
+
+    private
+      def failsafe_response(exception)
+        log_failsafe_exception(exception)
+        [500, {'Content-Type' => 'text/html'}, failsafe_response_body]
+      rescue Exception => failsafe_error # Logger or IO errors
+        $stderr.puts "Error during failsafe response: #{failsafe_error}"
+      end
+
+      def failsafe_response_body
+        error_path = "#{self.class.error_file_path}/500.html"
+        if File.exist?(error_path)
+          File.read(error_path)
+        else
+          "<html><body><h1>500 Internal Server Error</h1></body></html>"
+        end
+      end
+
+      def log_failsafe_exception(exception)
+        message = "/!\\ FAILSAFE /!\\  #{Time.now}\n  Status: 500 Internal Server Error\n"
+        message << "  #{exception}\n    #{exception.backtrace.join("\n    ")}" if exception
+        failsafe_logger.fatal(message)
+      end
+
+      def failsafe_logger
+        if defined?(Rails) && Rails.logger
+          Rails.logger
+        else
+          Logger.new($stderr)
+        end
+      end
+  end
+end