config.ru

#!/usr/bin/env rackup

require File.expand_path('app', File.dirname(__FILE__))
Ramaze.start(:file => __FILE__, :started => true)
run Ramaze

god.conf

# Use a trailing '/' 
APP_ROOT = "/var/www/apps/my.domain.com/"

# The list of ports which our website is running on. We want to setup God monitoring for each of these ports as each port has a separate master  unicorn process. In our case we're just going to use one port
%w{15000}.each do |port|
  God.watch do |w|
    w.name = "my.domain.com-#{port}"
    w.interval = 30.seconds # default
    # Omit the trailing '/' after #{APP_ROOT}
    # Go into the website root before starting unicorn
    w.start = "cd #{APP_ROOT} && unicorn -l #{port} -c #{APP_ROOT}config/unicorn.conf" 
    # -QUIT = graceful shutdown, waits for workers to finish their current request before finishing
    w.stop = "kill -QUIT `cat #{APP_ROOT}tmp/pids/unicorn-master.pid`"
    # -USR2 = reexecute the running binary. A separate QUIT should be sent to the original process once the child is verified to be up and running.
    w.restart = "kill -USR2 `cat #{APP_ROOT}tmp/pids/unicorn-master.pid`"
    w.start_grace = 10.seconds
    w.restart_grace = 10.seconds

    # User under which to run the process
    w.uid = 'www-data'
    w.gid = 'www-data'
    
    # Cleanup the pid file (this is needed for processes running as a daemon)
    w.behavior(:clean_pid_file)

    # Conditions under which to start the process
    w.start_if do |start|
      start.condition(:process_running) do |c|
        c.interval = 5.seconds
        c.running = false
      end
    end
    
    # Conditions under which to restart the process
    w.restart_if do |restart|
      restart.condition(:memory_usage) do |c|
        c.above = 150.megabytes
        c.times = [3, 5] # 3 out of 5 intervals
      end
    
      restart.condition(:cpu_usage) do |c|
        c.above = 50.percent
        c.times = 5
      end
    end
    
    w.lifecycle do |on|
      on.condition(:flapping) do |c|
        c.to_state = [:start, :restart]
        c.times = 5
        c.within = 5.minute
        c.transition = :unmonitored
        c.retry_in = 10.minutes
        c.retry_times = 5
        c.retry_within = 2.hours
      end
    end
  end
end

nginx.conf

# replace my_web_app with any unique identifier
# replace the port number with any unused port
upstream my_web_app {
  server 127.0.0.1:15000 fail_timeout=0;
}

server {
  # replace my.domain.com with your web site's domain
  server_name    my.domain.com;

  keepalive_timeout 5;
  
  # you don't have to use my.domain.com in the path but I find its a useful convention
  # you also might want to write these logs to /var/log/nginx
  access_log    /var/www/apps/my.domain.com/log/nginx.access.log;
  error_log     /var/www/apps/my.domain.com/log/nginx.error.log;
  
  # path to the root of your application
  root /var/www/apps/my.domain.com/;
    
  location / {
    if (-f $request_filename) {
      access_log off;
      rewrite_log off;
      expires 30d;
      break;
    }

    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header Host $host;
    proxy_redirect off;

    if (!-f $request_filename) {
      # my_web_app needs to be the same as whatever upstream name you assigned above
      proxy_pass http://my_web_app;
      break;
    }
  }

}

unicorn.conf

# Unicorn says to use at least one worker process per core (particularly on dedicated servers)
worker_processes 4

APP_ROOT = "/var/www/apps/my.domain.com"

# The root directory of you app
working_directory APP_ROOT

# Port that worker processes listen on
# This can also be a unix socket
listen 15010, :tcp_nopush => true

# Location of master process PID file
pid "#{APP_ROOT}/tmp/pids/unicorn-master.pid"

# Location of stderr/stdout logs
stderr_path "#{APP_ROOT}/log/unicorn.stderr.log"
stdout_path "#{APP_ROOT}/log/unicorn.stdout.log"

# combine REE with "preload_app true" for memory savings
# http://rubyenterpriseedition.com/faq.html#adapt_apps_for_cow
preload_app true
GC.respond_to?(:copy_on_write_friendly=) and
GC.copy_on_write_friendly = true