capistrano unicorn integration

unicorn.rb

# Unicorn itself is configured in `config/unicorn.rb`. These are the tasks,
# that allow you to control the server through Capistrano's `cap` command.

# To understand how Unicorn reacts to each signal, you should really read
# http://unicorn.bogomips.org/SIGNALS.html

namespace :unicorn do
  task :start do
    env = fetch(:rails_env, "production")
    run <<-EOC
      cd #{current_path} && \
      bundle exec unicorn -c config/unicorn.rb -E #{env} -D
    EOC
  end

  task :stop do
    signal "QUIT"
  end

  task :restart do
    signal "USR2"
  end

  task :reload do
    signal "HUP"
  end

  namespace :workers do
    task :count do
      puts capture("ps -o ppid x | grep `cat #{pid_path}` | wc -l")
    end

    task :inc do
      signal "TTIN"
    end

    task :dec do
      signal "TTOU"
    end
  end

  def pid_path
    "#{shared_path}/pids/unicorn.pid"
  end

  def signal(sig)
    run "test -e #{pid_path} && kill -s #{sig} `cat #{pid_path}`"
  end
end

# Overwrite blank tasks to install our own environment specific behaviour.
# Here we have the `start`, `stop` and `restart` tasks, delegate to the
# unicorn specific implementations.

namespace :deploy do
  desc "Start unicorn"
  task :start, roles: :app do
    unicorn.start
  end

  desc "Stop unicorn"
  task :stop, roles: :app do
    unicorn.stop
  end

  desc "Restart unicorn, zero-downtime (server must be running)"
  task :restart, roles: :app do
    unicorn.restart
  end

  desc "Reload unicorn config files and restart workers"
  task :reload, roles: :app do
    unicorn.reload
  end
end