vmware-nsx/quantum/openstack/common/processutils.py

# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright 2011 OpenStack Foundation.
# All Rights Reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.

"""
System-level utilities and helper functions.
"""

import os
import random
import shlex
import signal

from eventlet.green import subprocess
from eventlet import greenthread

from quantum.openstack.common.gettextutils import _
from quantum.openstack.common import log as logging


LOG = logging.getLogger(__name__)


class UnknownArgumentError(Exception):
    def __init__(self, message=None):
        super(UnknownArgumentError, self).__init__(message)


class ProcessExecutionError(Exception):
    def __init__(self, stdout=None, stderr=None, exit_code=None, cmd=None,
                 description=None):
        self.exit_code = exit_code
        self.stderr = stderr
        self.stdout = stdout
        self.cmd = cmd
        self.description = description

        if description is None:
            description = "Unexpected error while running command."
        if exit_code is None:
            exit_code = '-'
        message = ("%s\nCommand: %s\nExit code: %s\nStdout: %r\nStderr: %r"
                   % (description, cmd, exit_code, stdout, stderr))
        super(ProcessExecutionError, self).__init__(message)


class NoRootWrapSpecified(Exception):
    def __init__(self, message=None):
        super(NoRootWrapSpecified, self).__init__(message)


def _subprocess_setup():
    # Python installs a SIGPIPE handler by default. This is usually not what
    # non-Python subprocesses expect.
    signal.signal(signal.SIGPIPE, signal.SIG_DFL)


def execute(*cmd, **kwargs):
    """
    Helper method to shell out and execute a command through subprocess with
    optional retry.

    :param cmd:             Passed to subprocess.Popen.
    :type cmd:              string
    :param process_input:   Send to opened process.
    :type proces_input:     string
    :param check_exit_code: Single bool, int, or list of allowed exit
                            codes.  Defaults to [0].  Raise
                            :class:`ProcessExecutionError` unless
                            program exits with one of these code.
    :type check_exit_code:  boolean, int, or [int]
    :param delay_on_retry:  True | False. Defaults to True. If set to True,
                            wait a short amount of time before retrying.
    :type delay_on_retry:   boolean
    :param attempts:        How many times to retry cmd.
    :type attempts:         int
    :param run_as_root:     True | False. Defaults to False. If set to True,
                            the command is prefixed by the command specified
                            in the root_helper kwarg.
    :type run_as_root:      boolean
    :param root_helper:     command to prefix to commands called with
                            run_as_root=True
    :type root_helper:      string
    :param shell:           whether or not there should be a shell used to
                            execute this command. Defaults to false.
    :type shell:            boolean
    :returns:               (stdout, stderr) from process execution
    :raises:                :class:`UnknownArgumentError` on
                            receiving unknown arguments
    :raises:                :class:`ProcessExecutionError`
    """

    process_input = kwargs.pop('process_input', None)
    check_exit_code = kwargs.pop('check_exit_code', [0])
    ignore_exit_code = False
    delay_on_retry = kwargs.pop('delay_on_retry', True)
    attempts = kwargs.pop('attempts', 1)
    run_as_root = kwargs.pop('run_as_root', False)
    root_helper = kwargs.pop('root_helper', '')
    shell = kwargs.pop('shell', False)

    if isinstance(check_exit_code, bool):
        ignore_exit_code = not check_exit_code
        check_exit_code = [0]
    elif isinstance(check_exit_code, int):
        check_exit_code = [check_exit_code]

    if len(kwargs):
        raise UnknownArgumentError(_('Got unknown keyword args '
                                     'to utils.execute: %r') % kwargs)

    if run_as_root and os.geteuid() != 0:
        if not root_helper:
            raise NoRootWrapSpecified(
                message=('Command requested root, but did not specify a root '
                         'helper.'))
        cmd = shlex.split(root_helper) + list(cmd)

    cmd = map(str, cmd)

    while attempts > 0:
        attempts -= 1
        try:
            LOG.debug(_('Running cmd (subprocess): %s'), ' '.join(cmd))
            _PIPE = subprocess.PIPE  # pylint: disable=E1101

            if os.name == 'nt':
                preexec_fn = None
                close_fds = False
            else:
                preexec_fn = _subprocess_setup
                close_fds = True

            obj = subprocess.Popen(cmd,
                                   stdin=_PIPE,
                                   stdout=_PIPE,
                                   stderr=_PIPE,
                                   close_fds=close_fds,
                                   preexec_fn=preexec_fn,
                                   shell=shell)
            result = None
            if process_input is not None:
                result = obj.communicate(process_input)
            else:
                result = obj.communicate()
            obj.stdin.close()  # pylint: disable=E1101
            _returncode = obj.returncode  # pylint: disable=E1101
            if _returncode:
                LOG.debug(_('Result was %s') % _returncode)
                if not ignore_exit_code and _returncode not in check_exit_code:
                    (stdout, stderr) = result
                    raise ProcessExecutionError(exit_code=_returncode,
                                                stdout=stdout,
                                                stderr=stderr,
                                                cmd=' '.join(cmd))
            return result
        except ProcessExecutionError:
            if not attempts:
                raise
            else:
                LOG.debug(_('%r failed. Retrying.'), cmd)
                if delay_on_retry:
                    greenthread.sleep(random.randint(20, 200) / 100.0)
        finally:
            # NOTE(termie): this appears to be necessary to let the subprocess
            #               call clean something up in between calls, without
            #               it two execute calls in a row hangs the second one
            greenthread.sleep(0)