neutron/neutron/agent/linux/utils.py

# Copyright 2012 Locaweb.
# 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.

import fcntl
import glob
import os
import shlex
import socket
import struct
import tempfile

from eventlet.green import subprocess
from eventlet import greenthread

from neutron.common import constants
from neutron.common import utils
from neutron.openstack.common import excutils
from neutron.openstack.common import log as logging


LOG = logging.getLogger(__name__)


def create_process(cmd, root_helper=None, addl_env=None):
    """Create a process object for the given command.

    The return value will be a tuple of the process object and the
    list of command arguments used to create it.
    """
    if root_helper:
        cmd = shlex.split(root_helper) + cmd
    cmd = map(str, cmd)

    LOG.debug(_("Running command: %s"), cmd)
    env = os.environ.copy()
    if addl_env:
        env.update(addl_env)

    obj = utils.subprocess_popen(cmd, shell=False,
                                 stdin=subprocess.PIPE,
                                 stdout=subprocess.PIPE,
                                 stderr=subprocess.PIPE,
                                 env=env)

    return obj, cmd


def execute(cmd, root_helper=None, process_input=None, addl_env=None,
            check_exit_code=True, return_stderr=False, log_fail_as_error=True,
            extra_ok_codes=None):
    try:
        obj, cmd = create_process(cmd, root_helper=root_helper,
                                  addl_env=addl_env)
        _stdout, _stderr = (process_input and
                            obj.communicate(process_input) or
                            obj.communicate())
        obj.stdin.close()
        m = _("\nCommand: %(cmd)s\nExit code: %(code)s\nStdout: %(stdout)r\n"
              "Stderr: %(stderr)r") % {'cmd': cmd, 'code': obj.returncode,
                                       'stdout': _stdout, 'stderr': _stderr}

        extra_ok_codes = extra_ok_codes or []
        if obj.returncode and obj.returncode in extra_ok_codes:
            obj.returncode = None

        if obj.returncode and log_fail_as_error:
            LOG.error(m)
        else:
            LOG.debug(m)

        if obj.returncode and check_exit_code:
            raise RuntimeError(m)
    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)

    return return_stderr and (_stdout, _stderr) or _stdout


def get_interface_mac(interface):
    MAC_START = 18
    MAC_END = 24
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    info = fcntl.ioctl(s.fileno(), 0x8927,
        struct.pack('256s', interface[:constants.DEVICE_NAME_MAX_LEN]))
    return ''.join(['%02x:' % ord(char)
                    for char in info[MAC_START:MAC_END]])[:-1]


def replace_file(file_name, data):
    """Replaces the contents of file_name with data in a safe manner.

    First write to a temp file and then rename. Since POSIX renames are
    atomic, the file is unlikely to be corrupted by competing writes.

    We create the tempfile on the same device to ensure that it can be renamed.
    """

    base_dir = os.path.dirname(os.path.abspath(file_name))
    tmp_file = tempfile.NamedTemporaryFile('w+', dir=base_dir, delete=False)
    tmp_file.write(data)
    tmp_file.close()
    os.chmod(tmp_file.name, 0o644)
    os.rename(tmp_file.name, file_name)


def find_child_pids(pid):
    """Retrieve a list of the pids of child processes of the given pid."""

    try:
        raw_pids = execute(['ps', '--ppid', pid, '-o', 'pid='])
    except RuntimeError as e:
        # Unexpected errors are the responsibility of the caller
        with excutils.save_and_reraise_exception() as ctxt:
            # Exception has already been logged by execute
            no_children_found = 'Exit code: 1' in str(e)
            if no_children_found:
                ctxt.reraise = False
                return []
    return [x.strip() for x in raw_pids.split('\n') if x.strip()]


def _get_conf_base(cfg_root, uuid, ensure_conf_dir):
    conf_dir = os.path.abspath(os.path.normpath(cfg_root))
    conf_base = os.path.join(conf_dir, uuid)
    if ensure_conf_dir:
        if not os.path.isdir(conf_dir):
            os.makedirs(conf_dir, 0o755)
    return conf_base


def get_conf_file_name(cfg_root, uuid, cfg_file, ensure_conf_dir=False):
    """Returns the file name for a given kind of config file."""
    conf_base = _get_conf_base(cfg_root, uuid, ensure_conf_dir)
    return "%s.%s" % (conf_base, cfg_file)


def get_value_from_conf_file(cfg_root, uuid, cfg_file, converter=None):
    """A helper function to read a value from one of a config file."""
    file_name = get_conf_file_name(cfg_root, uuid, cfg_file)
    msg = _('Error while reading %s')

    try:
        with open(file_name, 'r') as f:
            try:
                return converter and converter(f.read()) or f.read()
            except ValueError:
                msg = _('Unable to convert value in %s')
    except IOError:
        msg = _('Unable to access %s')

    LOG.debug(msg % file_name)
    return None


def remove_conf_files(cfg_root, uuid):
    conf_base = _get_conf_base(cfg_root, uuid, False)
    for file_path in glob.iglob("%s.*" % conf_base):
        os.unlink(file_path)


def remove_conf_file(cfg_root, uuid, cfg_file):
    """Remove a config file."""
    conf_file = get_conf_file_name(cfg_root, uuid, cfg_file)
    if os.path.exists(conf_file):
        os.unlink(conf_file)