em-postgresql-adapter

PostgreSQL fiber-based ActiveRecord 3.1.x connection adapter for Ruby 1.9.

IMPORTANT: If you need to use em-postgresql-adapter with ActiveRecord < 3.1 please use the https://github.com/leftbee/em-postgresql-adapter/tree/pre-3_1 branch instead.

Installation

Edit your Gemfile:

gem 'pg'
gem 'em-postgresql-adapter', :git => 'git://github.com/grid5000/em-postgresql-adapter.git'
gem 'rack-fiber_pool',  :require => 'rack/fiber_pool'
gem 'em-synchrony', :git     => 'git://github.com/igrigorik/em-synchrony.git',
                    :require => ['em-synchrony',
                                 'em-synchrony/activerecord']

Then edit your environment (i.e., production.rb, staging.rb, etc.) and make sure threadsafe! is enabled. Also make sure to install the Rack::FiberPool middleware as early in the stack as possible:

MyRails3App::Application.configure do
  # ...
  config.middleware.insert_before ActionDispatch::ShowExceptions, Rack::FiberPool
  config.threadsafe!
  # ...
end

And finally, edit your config/database.yml:

production:
  adapter: em_postgresql
  database: myapp_production
  username: root
  password:
  host: localhost
  pool: 6
  connections: 6

Benchmark

Using a modified aync_rails app https://github.com/igrigorik/async-rails:

class WidgetsController < ApplicationController
  def index
    Widget.find_by_sql("select pg_sleep(1)")
    render :text => "Oh hai"
  end
end

Results:

p:~ ruben$ ab -c 220 -n 2000 http://127.0.0.1:3000/widgets
This is ApacheBench, Version 2.3 <$Revision: 655654 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 127.0.0.1 (be patient)
Completed 200 requests
Completed 400 requests
Completed 600 requests
Completed 800 requests
Completed 1000 requests
Completed 1200 requests
Completed 1400 requests
Completed 1600 requests
Completed 1800 requests
Completed 2000 requests
Finished 2000 requests


Server Software:        thin
Server Hostname:        127.0.0.1
Server Port:            3000

Document Path:          /widgets
Document Length:        6 bytes

Concurrency Level:      220
Time taken for tests:   21.075 seconds
Complete requests:      2000
Failed requests:        0
Write errors:           0
Total transferred:      558000 bytes
HTML transferred:       12000 bytes
Requests per second:    94.90 [#/sec] (mean)
Time per request:       2318.292 [ms] (mean)
Time per request:       10.538 [ms] (mean, across all concurrent requests)
Transfer rate:          25.86 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    1   2.3      0      10
Processing:  1007 2219 297.2   2123    3571
Waiting:     1007 2215 298.4   2122    3569
Total:       1017 2220 297.0   2123    3574

Percentage of the requests served within a certain time (ms)
  50%   2123
  66%   2128
  75%   2134
  80%   2580
  90%   2645
  95%   2702
  98%   2865
  99%   3013
 100%   3574 (longest request)

Credits

Based on brianmario's mysql2 em adapter https://github.com/brianmario/mysql2 and oldmoe's neverblock-postgresql-adapter https://github.com/oldmoe/neverblock-postgresql-adapter.

License

This software is released under the MIT license.