Synnefo » snf-ganeti

    if not utils.CheckDaemonAlive('/var/run/xend.pid', 'xend'):

      return "xend daemon is not running"

def CheckDaemonAlive(pid_file, process_string):

  """Check wether the specified daemon is alive.

  Args:

   - pid_file: file to read the daemon pid from, the file is

               expected to contain only a single line containing

               only the PID

   - process_string: a substring that we expect to find in

                     the command line of the daemon process

  Returns:

   - True if the daemon is judged to be alive (that is:

      - the PID file exists, is readable and contains a number

      - a process of the specified PID is running

      - that process contains the specified string in its

        command line

      - the process is not in state Z (zombie))

   - False otherwise

  """

  try:

    pid_file = file(pid_file, 'r')

    try:

      pid = int(pid_file.readline())

    finally:

      pid_file.close()

    cmdline_file_path = "/proc/%s/cmdline" % (pid)

    cmdline_file = open(cmdline_file_path, 'r')

    try:

      cmdline = cmdline_file.readline()

    finally:

      cmdline_file.close()

    if not process_string in cmdline:

      return False

    stat_file_path =  "/proc/%s/stat" % (pid)

    stat_file = open(stat_file_path, 'r')

    try:

      process_state = stat_file.readline().split()[2]

    finally:

      stat_file.close()

    if process_state == 'Z':

      return False

  except (IndexError, IOError, ValueError):

    return False

  return True