Capistrano task which generates nginx passenger config

passenger.rb

# -- config/passenger.rb
#    require this file in the config/deploy.rb
 
 
Capistrano::Configuration.instance.load do
  # Config template path (config/passenger/template.nginx.conf)
  set :template_path,       File.expand_path('../passenger/template.nginx.conf', __FILE__)
  
  # Upload config to:
  set :config_deploy_path,  "#{deploy_to}/config/nginx_passenger.conf"
  
  # Nginx`s sites_enabled path
  # It should be included in nginx.conf (`include /opt/nginx/sites_enabled/*;`)
  set :config_enabled_path, "/opt/nginx/sites_enabled"
  
  # Nginx`s listen_address
  set :listen_address,      "0.0.0.0:80"
  
  namespace :passenger do
    desc "Generates nginx config"
    task :generate_nginx_config, roles: :app, except: {no_release: true} do
      template = File.read(template_path)
      
      # We can use capistrano variables in our template.
      # Get required var names:
      var_names = template.scan(/%{([^{}]*)}/).flatten.uniq
      
      # Then build the hash of names and values:
      config_vars = var_names.map do |var_name|
        name = var_name.to_sym
        [name, fetch(name)] 
      end
      config_vars = Hash[config_vars]
      
      # Prepare directories
      run "[[ -d #{deploy_to}/log ]] || mkdir -p #{deploy_to}/log"
      run "[[ -d #{deploy_to}/config ]] || mkdir -p #{deploy_to}/config"
      
      # Upload generated config
      top.put sprintf(template, config_vars), config_deploy_path, via: :scp
      
      # Create symlink in the nginx`s sites_enabled path
      run "ln -fs #{config_deploy_path} #{config_enabled_path}/01-#{domain}.conf"
    end
    
    desc "Restart nginx"
    task :restart_nginx, roles: :app do
      sudo "sh -c \"/etc/init.d/nginx configtest && /etc/init.d/nginx restart\"", pty: true
    end
  end
 
  before "passenger:restart_nginx", "passenger:generate_nginx_config"
end

template.nginx.conf

# -- config/passenger/template.nginx.conf
#    use any capistrano variables inside %{}
 
server {
  listen      %{listen_address};
  server_name www.%{domain};
  return 301 $scheme://%{domain}$request_uri;
}
 
server {
  listen      %{listen_address};
  server_name %{domain};
  error_log   %{deploy_to}/log/nginx.error.log debug;
  root        %{deploy_to}/current/public;
  passenger_enabled on;
  rails_env   %{rails_env};
}