Slow newrelic_rpm gem with rubinius and rails 4.

gistfile1.txt

% ruby --version
rubinius 2.0.0.n198 (1.9.3 417f847d 2013-07-17 JI) [x86_64-apple-darwin12.4.0]

% rails --version
Rails 4.0.0

Create a new Rails app and switch to it's folder

% rails new TestApp
% cd TestApp

Install gems:

% bundle install

Create some controllers/models/views

% rails g scaffold test
$ rake db:migrate

Start the rails server:

% rails s

Open a webbrowser and go to http://localhost:3000/tests. Observe the rails log:


% Started GET "/tests" for 127.0.0.1 at 2013-08-09 11:00:47 +0200
% Processing by TestsController#index as HTML
%   Test Load (0.2ms)  SELECT "tests".* FROM "tests"
%   Rendered tests/index.html.erb within layouts/application (0.9ms)
% Completed 200 OK in 8ms (Views: 5.3ms | ActiveRecord: 0.2ms)


Particularly interesting is the response time of 8ms.

Next, add "gem 'newrelic_rpm'" to the Gemfile and run bundle install again.

Start the rails server and do the same http://localhost:3000/tests request. Now,
when observing the rails log you see something like this:


% Started GET "/tests" for 127.0.0.1 at 2013-08-09 11:01:37 +0200
% Processing by TestsController#index as HTML
%   Test Load (0.2ms)  SELECT "tests".* FROM "tests"
%   Rendered tests/index.html.erb within layouts/application (802.9ms)
% Completed 200 OK in 809ms (Views: 807.7ms | ActiveRecord: 0.2ms)


Note the response time has increased by a factor of 100! The CPU of the machine
went straight to 100%. This does not only happen on my Mac OS X 10.8 work
machine, but also when deploying to heroku.