deploy.rb

#...

set :app_path, "#{deploy_to}/#{current_path}"

#...

desc "Deploys the current version to the server."
task :deploy => :environment do
  deploy do
    #...

    to :launch do
      invoke :'unicorn:restart'
      #...
    end
  end
end

namespace :unicorn do
  set :unicorn_pid, "#{deploy_to}/shared/pids/unicorn.pid"
  set :start_unicorn, %{
    cd #{app_path}
    bundle exec unicorn -c #{app_path}/config/unicorn.rb -E #{rails_env} -D
  }
 
#                                                                    Start task
# ------------------------------------------------------------------------------
  desc "Start unicorn"
  task :start => :environment do
    queue 'echo "-----> Start Unicorn"'
    queue! start_unicorn
  end
 
#                                                                     Stop task
# ------------------------------------------------------------------------------
  desc "Stop unicorn"
  task :stop do
    queue 'echo "-----> Stop Unicorn"'
    queue! %{
      test -s "#{unicorn_pid}" && kill -QUIT `cat "#{unicorn_pid}"` && echo "Stop Ok" && exit 0
      echo >&2 "Not running"
    }
  end
 
#                                                                  Restart task
# ------------------------------------------------------------------------------
  desc "Restart unicorn using 'upgrade'"
  task :restart => :environment do
    invoke 'unicorn:stop'
    invoke 'unicorn:start'
  end
end