Synnefo » snf-ganeti » ganeti-local

import sys

def _BuildCmdEnvironment(env):

  """Builds the environment for an external program.

  """

  cmd_env = os.environ.copy()

  cmd_env["LC_ALL"] = "C"

  if env is not None:

    cmd_env.update(env)

  return cmd_env

def RunCmd(cmd, env=None, output=None, cwd="/"):

  @type cmd: string or list

  @param env: Additional environment variables

  if isinstance(cmd, basestring):

    strcmd = cmd

    shell = True

  else:

    strcmd = ShellQuoteArgs(cmd)

  if output:

    logging.debug("RunCmd %s, output file '%s'", strcmd, output)

    logging.debug("RunCmd %s", strcmd)

  cmd_env = _BuildCmdEnvironment(env)

def StartDaemon(cmd, env=None, cwd="/", output=None, output_fd=None,

                pidfile=None):

  """Start a daemon process after forking twice.

  @type cmd: string or list

  @param cmd: Command to run

  @type env: dict

  @param env: Additional environment variables

  @type cwd: string

  @param cwd: Working directory for the program

  @type output: string

  @param output: Path to file in which to save the output

  @type output_fd: int

  @param output_fd: File descriptor for output

  @type pidfile: string

  @param pidfile: Process ID file

  @rtype: int

  @return: Daemon process ID

  @raise errors.ProgrammerError: if we call this when forks are disabled

  """

  if no_fork:

    raise errors.ProgrammerError("utils.StartDaemon() called with fork()"

                                 " disabled")

  if output and not (bool(output) ^ (output_fd is not None)):

    raise errors.ProgrammerError("Only one of 'output' and 'output_fd' can be"

                                 " specified")

  if isinstance(cmd, basestring):

    cmd = ["/bin/sh", "-c", cmd]

  strcmd = ShellQuoteArgs(cmd)

  if output:

    logging.debug("StartDaemon %s, output file '%s'", strcmd, output)

  else:

    logging.debug("StartDaemon %s", strcmd)

  cmd_env = _BuildCmdEnvironment(env)

  # Create pipe for sending PID back

  (pidpipe_read, pidpipe_write) = os.pipe()

  try:

    try:

      # Create pipe for sending error messages

      (errpipe_read, errpipe_write) = os.pipe()

      try:

        try:

          # First fork

          pid = os.fork()

          if pid == 0:

            try:

              # Child process, won't return

              _RunCmdDaemonChild(errpipe_read, errpipe_write,

                                 pidpipe_read, pidpipe_write,

                                 cmd, cmd_env, cwd,

                                 output, output_fd, pidfile)

            finally:

              # Well, maybe child process failed

              os._exit(1)

        finally:

          _CloseFDNoErr(errpipe_write)

        # Wait for daemon to be started (or an error message to arrive) and read

        # up to 100 KB as an error message

        errormsg = RetryOnSignal(os.read, errpipe_read, 100 * 1024)

      finally:

        _CloseFDNoErr(errpipe_read)

    finally:

      _CloseFDNoErr(pidpipe_write)

    # Read up to 128 bytes for PID

    pidtext = RetryOnSignal(os.read, pidpipe_read, 128)

  finally:

    _CloseFDNoErr(pidpipe_read)

  # Try to avoid zombies by waiting for child process

  try:

    os.waitpid(pid, 0)

  except OSError:

    pass

  if errormsg:

    raise errors.OpExecError("Error when starting daemon process: %r" %

                             errormsg)

  try:

    return int(pidtext)

  except (ValueError, TypeError), err:

    raise errors.OpExecError("Error while trying to parse PID %r: %s" %

                             (pidtext, err))

def _RunCmdDaemonChild(errpipe_read, errpipe_write,

                       pidpipe_read, pidpipe_write,

                       args, env, cwd,

                       output, fd_output, pidfile):

  """Child process for starting daemon.

  """

  try:

    # Close parent's side

    _CloseFDNoErr(errpipe_read)

    _CloseFDNoErr(pidpipe_read)

    # First child process

    os.chdir("/")

    os.umask(077)

    os.setsid()

    # And fork for the second time

    pid = os.fork()

    if pid != 0:

      # Exit first child process

      os._exit(0) # pylint: disable-msg=W0212

    # Make sure pipe is closed on execv* (and thereby notifies original process)

    SetCloseOnExecFlag(errpipe_write, True)

    # List of file descriptors to be left open

    noclose_fds = [errpipe_write]

    # Open PID file

    if pidfile:

      try:

        # TODO: Atomic replace with another locked file instead of writing into

        # it after creating

        fd_pidfile = os.open(pidfile, os.O_WRONLY | os.O_CREAT, 0600)

        # Lock the PID file (and fail if not possible to do so). Any code

        # wanting to send a signal to the daemon should try to lock the PID

        # file before reading it. If acquiring the lock succeeds, the daemon is

        # no longer running and the signal should not be sent.

        LockFile(fd_pidfile)

        os.write(fd_pidfile, "%d\n" % os.getpid())

      except Exception, err:

        raise Exception("Creating and locking PID file failed: %s" % err)

      # Keeping the file open to hold the lock

      noclose_fds.append(fd_pidfile)

      SetCloseOnExecFlag(fd_pidfile, False)

    else:

      fd_pidfile = None

    # Open /dev/null

    fd_devnull = os.open(os.devnull, os.O_RDWR)

    assert not output or (bool(output) ^ (fd_output is not None))

    if fd_output is not None:

      pass

    elif output:

      # Open output file

      try:

        # TODO: Implement flag to set append=yes/no

        fd_output = os.open(output, os.O_WRONLY | os.O_CREAT, 0600)

      except EnvironmentError, err:

        raise Exception("Opening output file failed: %s" % err)

    else:

      fd_output = fd_devnull

    # Redirect standard I/O

    os.dup2(fd_devnull, 0)

    os.dup2(fd_output, 1)

    os.dup2(fd_output, 2)

    # Send daemon PID to parent

    RetryOnSignal(os.write, pidpipe_write, str(os.getpid()))

    # Close all file descriptors except stdio and error message pipe

    CloseFDs(noclose_fds=noclose_fds)

    # Change working directory

    os.chdir(cwd)

    if env is None:

      os.execvp(args[0], args)

    else:

      os.execvpe(args[0], args, env)

  except: # pylint: disable-msg=W0702

    try:

      # Report errors to original process

      buf = str(sys.exc_info()[1])

      RetryOnSignal(os.write, errpipe_write, buf)

    except: # pylint: disable-msg=W0702

      # Ignore errors in error handling

      pass

  os._exit(1) # pylint: disable-msg=W0212