a.rb

module Util
    def mongo_cluster_command_line_options
  #
    Mongoid.default_client # Force the setting to be parsed
    settings   = Map.for(Mongoid.clients[:default])
    address = settings[:uri]

  #
    unless address && address =~ %r`://`
      raise("no uri in #{ settings.inspect }")
    end

  #
    rest = address.dup

    scheme, rest = rest.split('://', 2)

    if rest =~ %r`@`
      auth, rest = rest.split('@', 2)
    end

    hosts_and_ports, rest = rest.split('/', 2)

    path_info = rest

  #
    list = []

    list_of = proc{|arg| Coerce.list_of_strings(arg)}
    esc  = proc{|arg| Shellwords.escape(arg.to_s)}

    list_of[hosts_and_ports].each do |host_and_port|
      string = "#{ scheme }://" if scheme
      string << "#{ auth }@" if auth
      string << "#{ host_and_port }"
      string << "/#{ path_info }" if path_info

      uri = URI.parse(string)

      db       = (uri.path.split('/').reject{|x| x.blank?}.first || settings[:database])
      host     = (uri.host || list_of[settings[:hosts]].first)
      port     = (uri.port || settings[:port])
      username = (uri.user || settings[:username])
      password = (uri.password || settings[:password])
      ssl      = !!(settings.get(:options, :ssl))

      options = {
        :db       => db,
        :host     => host,
        :port     => port,
        :username => username,
        :password => password,
        :ssl      => ssl
      }.select{|k,v| v.present?}

      list.push(options)
    end

  #
    list
  end

  def mongo_master_command_line_options
    mongo_cluster_command_line_options.each do |options|
      command = ['mongo']

      db       = options[:db]
      host     = options[:host]
      port     = options[:port]
      username = options[:username]
      password = options[:password]
      ssl      = options[:ssl]

      command << "#{ db.inspect }" if db.present?
      command << "--host #{ host.inspect }" if host.present?
      command << "--port #{ port.inspect }" if port.present?
      command << "--username #{ username.inspect }" if username.present?
      command << "--password #{ password.inspect }" if password.present?
      command << "--ssl" if ssl.present?

      mongo = command.join(' ')

      stdout = `echo 'print("ismaster=" + db.isMaster().ismaster);' | #{ mongo } 2>&1`

      if $?.success? && stdout =~ /ismaster=true/
        return options
      end
    end

    raise "no master connection options found in #{ mongo_cluster_command_line_options.inspect }"
  end

  extend Util
end