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Derailed Benchmarks

A series of things you can use to benchmark a Rails app

Compatibility/Requirements

This gem has been tested and is known to work with Rails 3.2 using Ruby 2.1. It is not expected to work with older versions of Ruby. You'll need to install curl as well in the off chance you haven't already.

Install

Put this in your gemfile:

gem 'derailed_benchmarks', group: :development

Then run $ bundle install.

This part is important run this command to create a perf.rake

$ cat <<  EOF > perf.rake
  require 'bundler'
  Bundler.setup

  require 'derailed_benchmarks'
  require 'derailed_benchmarks/tasks'
EOF

The file should look like this:

$ cat perf.rake
  require 'bundler'
  Bundler.setup

  require 'derailed_benchmarks'
  require 'derailed_benchmarks/tasks'

This is done so the benchmarks will be loaded before your application, this is important for some benchmarks and less for others. This also prevents you from accidentally loading these benchmarks when you don't need them.

Run

To find out the tasks available you can use $ rake -f perf.rake -T which essentially says use the file perf.rake and list all the tasks.

$ rake -f perf.rake -T
rake perf:allocated_objects  # outputs allocated object diff after app is called TEST_COUNT times
rake perf:ips                # ips
rake perf:mem                # profiles ruby allocation
rake perf:ram_over_time      # outputs ram usage over time
rake perf:require_bench      # show memory usage caused by invoking require per gem
rake perf:stackprof          # sampling stack time
rake perf:test               # hits the url TEST_COUNT times

All the rake tasks accept configuration in the form of environment variables. For example, this command will measure the time it takes to hit your site 100,000 times:

$ rake -f perf.rake perf:test TEST_COUNT=100_000

Tests run against the production environment by default, but it's easy to change this if your app doesn't run locally with RAILS_ENV set to production. For example:

$ rake -f perf.rake perf:mem RAILS_ENV=development

Rack Setup

Using Rails? You don't need to do anything special. If you're using Rack, you need to tell us how to boot your app. In your perf.rake file add a task:

task :rack_load do
  DERAILED_APP = # your code here
end

Set the constant DERAILED_APP to your Rack app. See schneems/derailed_benchmarks#1 for more info.

Config

Here are the common environment variables.

PATH_TO_HIT

By default tasks will hit your homepage /. If you want to hit a different url use PATH_TO_HIT for example if you wanted to go to users/new you can execute:

PATH_TO_HIT=/users/new

USE_SERVER

All tests are run without a webserver by default, if you want to use a webserver set USE_SERVER to a Rack::Server compliant server, such as webrick.

USE_SERVER=webrick

TEST_COUNT

If the test contains an interation (most of them do), control how many times the test will loop before exiting with TEST_COUNT. To run 1 time you can execute

TEST_COUNT=1

Note some tasks have different defaults.

Task Specific notes

perf:mem

This task uses memory_profiler to see where memory is allocated while it is running. By default it will iterate once

perf:ips

Determines the number of times your app can serve a web request each second (iterations per second). Higher number is better. Note this will be much larger if you do not use a server.

perf:ram_over_time

Your app will use memory differently over time, this task records RSS memory usage every 5 seconds and outputs the value to STDOUT and to a file in tmp/. You can use this to build graphs (https://drive.google.com).

perf:require_bench

Shows the amount of memory (RAM) each library takes up when it is required.

action_controller/railtie: 1.06 mb
  action_controller: 0.72 mb
    action_controller/metal/live: 0.38 mb
      action_dispatch/http/response: 0.17 mb
        rack/request: 0.05 mb

License

MIT

Acknowledgements

Most of the commands are wrappers around other libraries, go check them out. Also thanks to @tenderlove as I cribbed some of the Rails init code in $ rake perf:setup from one of his projects.

kthksbye @schneems