Lock deploy in Capistrano (only 1 deploy at a moment)

deploy.rb

at_exit do
  deploy.unlock
end

set :deploy_lock_file, "#{shared_path}/tmp/deploing_lock_file"

namespace :deploy do

desc "Check if somebody already is deploing"
  task :check_lock do
    result = capture("if [ -f #{deploy_lock_file} ]; then cat #{deploy_lock_file}; else echo '0'; fi").strip
    if result != '0'
      run "echo '#{result} already deploing' 1>&2"
      exit
    end
  end

  desc "Mark that I'm deploing"
  task :lock do
    current_user = `whoami`.strip
    run "echo '#{current_user}' > #{deploy_lock_file}"
  end

  desc "Clear deploy lock file after deploy"
  task :unlock do
    run "rm #{deploy_lock_file}"
  end

end


before "deploy", "deploy:check_lock"; before "deploy:migrations", "deploy:check_lock"
before "deploy", "deploy:lock"; before "deploy:migrations", "deploy:lock"
after "deploy", "deploy:unlock"; after "deploy:migrations", "deploy:unlock"