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#
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#

# Copyright (C) 2006, 2007 Google Inc.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301, USA.


"""Block device abstraction"""

import re
import time
import errno
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import pyparsing as pyp
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import os
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import logging
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from ganeti import utils
from ganeti import errors
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from ganeti import constants
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class BlockDev(object):
  """Block device abstract class.

  A block device can be in the following states:
    - not existing on the system, and by `Create()` it goes into:
    - existing but not setup/not active, and by `Assemble()` goes into:
    - active read-write and by `Open()` it goes into
    - online (=used, or ready for use)

  A device can also be online but read-only, however we are not using
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  the readonly state (LV has it, if needed in the future) and we are
  usually looking at this like at a stack, so it's easier to
  conceptualise the transition from not-existing to online and back
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  like a linear one.

  The many different states of the device are due to the fact that we
  need to cover many device types:
    - logical volumes are created, lvchange -a y $lv, and used
    - drbd devices are attached to a local disk/remote peer and made primary

  A block device is identified by three items:
    - the /dev path of the device (dynamic)
    - a unique ID of the device (static)
    - it's major/minor pair (dynamic)

  Not all devices implement both the first two as distinct items. LVM
  logical volumes have their unique ID (the pair volume group, logical
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  volume name) in a 1-to-1 relation to the dev path. For DRBD devices,
  the /dev path is again dynamic and the unique id is the pair (host1,
  dev1), (host2, dev2).
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  You can get to a device in two ways:
    - creating the (real) device, which returns you
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      an attached instance (lvcreate)
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    - attaching of a python instance to an existing (real) device

  The second point, the attachement to a device, is different
  depending on whether the device is assembled or not. At init() time,
  we search for a device with the same unique_id as us. If found,
  good. It also means that the device is already assembled. If not,
  after assembly we'll have our correct major/minor.

  """
  def __init__(self, unique_id, children):
    self._children = children
    self.dev_path = None
    self.unique_id = unique_id
    self.major = None
    self.minor = None
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    self.attached = False
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  def Assemble(self):
    """Assemble the device from its components.

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    Implementations of this method by child classes must ensure that:
      - after the device has been assembled, it knows its major/minor
        numbers; this allows other devices (usually parents) to probe
        correctly for their children
      - calling this method on an existing, in-use device is safe
      - if the device is already configured (and in an OK state),
        this method is idempotent
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    """
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    return True
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  def Attach(self):
    """Find a device which matches our config and attach to it.

    """
    raise NotImplementedError

  def Close(self):
    """Notifies that the device will no longer be used for I/O.

    """
    raise NotImplementedError

  @classmethod
  def Create(cls, unique_id, children, size):
    """Create the device.

    If the device cannot be created, it will return None
    instead. Error messages go to the logging system.

    Note that for some devices, the unique_id is used, and for other,
    the children. The idea is that these two, taken together, are
    enough for both creation and assembly (later).

    """
    raise NotImplementedError

  def Remove(self):
    """Remove this device.

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    This makes sense only for some of the device types: LV and file
    storeage. Also note that if the device can't attach, the removal
    can't be completed.
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    """
    raise NotImplementedError

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  def Rename(self, new_id):
    """Rename this device.

    This may or may not make sense for a given device type.

    """
    raise NotImplementedError

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  def Open(self, force=False):
    """Make the device ready for use.

    This makes the device ready for I/O. For now, just the DRBD
    devices need this.

    The force parameter signifies that if the device has any kind of
    --force thing, it should be used, we know what we are doing.

    """
    raise NotImplementedError

  def Shutdown(self):
    """Shut down the device, freeing its children.

    This undoes the `Assemble()` work, except for the child
    assembling; as such, the children on the device are still
    assembled after this call.

    """
    raise NotImplementedError

  def SetSyncSpeed(self, speed):
    """Adjust the sync speed of the mirror.

    In case this is not a mirroring device, this is no-op.

    """
    result = True
    if self._children:
      for child in self._children:
        result = result and child.SetSyncSpeed(speed)
    return result

  def GetSyncStatus(self):
    """Returns the sync status of the device.

    If this device is a mirroring device, this function returns the
    status of the mirror.

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    If sync_percent is None, it means the device is not syncing.
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    If estimated_time is None, it means we can't estimate
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    the time needed, otherwise it's the time left in seconds.

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    If is_degraded is True, it means the device is missing
    redundancy. This is usually a sign that something went wrong in
    the device setup, if sync_percent is None.

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    The ldisk parameter represents the degradation of the local
    data. This is only valid for some devices, the rest will always
    return False (not degraded).

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    @rtype: tuple
    @return: (sync_percent, estimated_time, is_degraded, ldisk)

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    """
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    return None, None, False, False
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  def CombinedSyncStatus(self):
    """Calculate the mirror status recursively for our children.

    The return value is the same as for `GetSyncStatus()` except the
    minimum percent and maximum time are calculated across our
    children.

    """
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    min_percent, max_time, is_degraded, ldisk = self.GetSyncStatus()
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    if self._children:
      for child in self._children:
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        c_percent, c_time, c_degraded, c_ldisk = child.GetSyncStatus()
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        if min_percent is None:
          min_percent = c_percent
        elif c_percent is not None:
          min_percent = min(min_percent, c_percent)
        if max_time is None:
          max_time = c_time
        elif c_time is not None:
          max_time = max(max_time, c_time)
        is_degraded = is_degraded or c_degraded
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        ldisk = ldisk or c_ldisk
    return min_percent, max_time, is_degraded, ldisk
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  def SetInfo(self, text):
    """Update metadata with info text.

    Only supported for some device types.

    """
    for child in self._children:
      child.SetInfo(text)

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  def Grow(self, amount):
    """Grow the block device.

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    @param amount: the amount (in mebibytes) to grow with
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    """
    raise NotImplementedError
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  def __repr__(self):
    return ("<%s: unique_id: %s, children: %s, %s:%s, %s>" %
            (self.__class__, self.unique_id, self._children,
             self.major, self.minor, self.dev_path))


class LogicalVolume(BlockDev):
  """Logical Volume block device.

  """
  def __init__(self, unique_id, children):
    """Attaches to a LV device.

    The unique_id is a tuple (vg_name, lv_name)

    """
    super(LogicalVolume, self).__init__(unique_id, children)
    if not isinstance(unique_id, (tuple, list)) or len(unique_id) != 2:
      raise ValueError("Invalid configuration data %s" % str(unique_id))
    self._vg_name, self._lv_name = unique_id
    self.dev_path = "/dev/%s/%s" % (self._vg_name, self._lv_name)
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    self._degraded = True
    self.major = self.minor = None
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    self.Attach()

  @classmethod
  def Create(cls, unique_id, children, size):
    """Create a new logical volume.

    """
    if not isinstance(unique_id, (tuple, list)) or len(unique_id) != 2:
      raise ValueError("Invalid configuration data %s" % str(unique_id))
    vg_name, lv_name = unique_id
    pvs_info = cls.GetPVInfo(vg_name)
    if not pvs_info:
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      raise errors.BlockDeviceError("Can't compute PV info for vg %s" %
                                    vg_name)
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    pvs_info.sort()
    pvs_info.reverse()
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    pvlist = [ pv[1] for pv in pvs_info ]
    free_size = sum([ pv[0] for pv in pvs_info ])

    # The size constraint should have been checked from the master before
    # calling the create function.
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    if free_size < size:
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      raise errors.BlockDeviceError("Not enough free space: required %s,"
                                    " available %s" % (size, free_size))
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    result = utils.RunCmd(["lvcreate", "-L%dm" % size, "-n%s" % lv_name,
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                           vg_name] + pvlist)
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    if result.failed:
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      raise errors.BlockDeviceError("%s - %s" % (result.fail_reason,
                                                result.output))
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    return LogicalVolume(unique_id, children)

  @staticmethod
  def GetPVInfo(vg_name):
    """Get the free space info for PVs in a volume group.

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    @param vg_name: the volume group name
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    @rtype: list
    @return: list of tuples (free_space, name) with free_space in mebibytes
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    """
    command = ["pvs", "--noheadings", "--nosuffix", "--units=m",
               "-opv_name,vg_name,pv_free,pv_attr", "--unbuffered",
               "--separator=:"]
    result = utils.RunCmd(command)
    if result.failed:
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      logging.error("Can't get the PV information: %s - %s",
                    result.fail_reason, result.output)
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      return None
    data = []
    for line in result.stdout.splitlines():
      fields = line.strip().split(':')
      if len(fields) != 4:
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        logging.error("Can't parse pvs output: line '%s'", line)
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        return None
      # skip over pvs from another vg or ones which are not allocatable
      if fields[1] != vg_name or fields[3][0] != 'a':
        continue
      data.append((float(fields[2]), fields[0]))

    return data

  def Remove(self):
    """Remove this logical volume.

    """
    if not self.minor and not self.Attach():
      # the LV does not exist
      return True
    result = utils.RunCmd(["lvremove", "-f", "%s/%s" %
                           (self._vg_name, self._lv_name)])
    if result.failed:
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      logging.error("Can't lvremove: %s - %s",
                    result.fail_reason, result.output)
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    return not result.failed

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  def Rename(self, new_id):
    """Rename this logical volume.

    """
    if not isinstance(new_id, (tuple, list)) or len(new_id) != 2:
      raise errors.ProgrammerError("Invalid new logical id '%s'" % new_id)
    new_vg, new_name = new_id
    if new_vg != self._vg_name:
      raise errors.ProgrammerError("Can't move a logical volume across"
                                   " volume groups (from %s to to %s)" %
                                   (self._vg_name, new_vg))
    result = utils.RunCmd(["lvrename", new_vg, self._lv_name, new_name])
    if result.failed:
      raise errors.BlockDeviceError("Failed to rename the logical volume: %s" %
                                    result.output)
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    self._lv_name = new_name
    self.dev_path = "/dev/%s/%s" % (self._vg_name, self._lv_name)

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  def Attach(self):
    """Attach to an existing LV.

    This method will try to see if an existing and active LV exists
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    which matches our name. If so, its major/minor will be
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    recorded.

    """
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    self.attached = False
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    result = utils.RunCmd(["lvs", "--noheadings", "--separator=,",
                           "-olv_attr,lv_kernel_major,lv_kernel_minor",
                           self.dev_path])
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    if result.failed:
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      logging.error("Can't find LV %s: %s, %s",
                    self.dev_path, result.fail_reason, result.output)
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      return False
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    out = result.stdout.strip().rstrip(',')
    out = out.split(",")
    if len(out) != 3:
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      logging.error("Can't parse LVS output, len(%s) != 3", str(out))
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      return False

    status, major, minor = out[:3]
    if len(status) != 6:
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      logging.error("lvs lv_attr is not 6 characters (%s)", status)
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      return False

    try:
      major = int(major)
      minor = int(minor)
    except ValueError, err:
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      logging.error("lvs major/minor cannot be parsed: %s", str(err))
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    self.major = major
    self.minor = minor
    self._degraded = status[0] == 'v' # virtual volume, i.e. doesn't backing
                                      # storage
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    self.attached = True
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    return True
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  def Assemble(self):
    """Assemble the device.

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    We alway run `lvchange -ay` on the LV to ensure it's active before
    use, as there were cases when xenvg was not active after boot
    (also possibly after disk issues).
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    """
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    result = utils.RunCmd(["lvchange", "-ay", self.dev_path])
    if result.failed:
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      logging.error("Can't activate lv %s: %s", self.dev_path, result.output)
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      return False
    return self.Attach()
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  def Shutdown(self):
    """Shutdown the device.

    This is a no-op for the LV device type, as we don't deactivate the
    volumes on shutdown.

    """
    return True

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  def GetSyncStatus(self):
    """Returns the sync status of the device.

    If this device is a mirroring device, this function returns the
    status of the mirror.

    For logical volumes, sync_percent and estimated_time are always
    None (no recovery in progress, as we don't handle the mirrored LV
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    case). The is_degraded parameter is the inverse of the ldisk
    parameter.
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    For the ldisk parameter, we check if the logical volume has the
    'virtual' type, which means it's not backed by existing storage
    anymore (read from it return I/O error). This happens after a
    physical disk failure and subsequent 'vgreduce --removemissing' on
    the volume group.
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    The status was already read in Attach, so we just return it.

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    @rtype: tuple
    @return: (sync_percent, estimated_time, is_degraded, ldisk)

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    """
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    return None, None, self._degraded, self._degraded
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  def Open(self, force=False):
    """Make the device ready for I/O.

    This is a no-op for the LV device type.

    """
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    pass
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  def Close(self):
    """Notifies that the device will no longer be used for I/O.

    This is a no-op for the LV device type.

    """
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    pass
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  def Snapshot(self, size):
    """Create a snapshot copy of an lvm block device.

    """
    snap_name = self._lv_name + ".snap"

    # remove existing snapshot if found
    snap = LogicalVolume((self._vg_name, snap_name), None)
    snap.Remove()

    pvs_info = self.GetPVInfo(self._vg_name)
    if not pvs_info:
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      raise errors.BlockDeviceError("Can't compute PV info for vg %s" %
                                    self._vg_name)
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    pvs_info.sort()
    pvs_info.reverse()
    free_size, pv_name = pvs_info[0]
    if free_size < size:
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      raise errors.BlockDeviceError("Not enough free space: required %s,"
                                    " available %s" % (size, free_size))
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    result = utils.RunCmd(["lvcreate", "-L%dm" % size, "-s",
                           "-n%s" % snap_name, self.dev_path])
    if result.failed:
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      raise errors.BlockDeviceError("command: %s error: %s - %s" %
                                    (result.cmd, result.fail_reason,
                                     result.output))
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    return snap_name

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  def SetInfo(self, text):
    """Update metadata with info text.

    """
    BlockDev.SetInfo(self, text)

    # Replace invalid characters
    text = re.sub('^[^A-Za-z0-9_+.]', '_', text)
    text = re.sub('[^-A-Za-z0-9_+.]', '_', text)

    # Only up to 128 characters are allowed
    text = text[:128]

    result = utils.RunCmd(["lvchange", "--addtag", text,
                           self.dev_path])
    if result.failed:
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      raise errors.BlockDeviceError("Command: %s error: %s - %s" %
                                    (result.cmd, result.fail_reason,
                                     result.output))
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  def Grow(self, amount):
    """Grow the logical volume.

    """
    # we try multiple algorithms since the 'best' ones might not have
    # space available in the right place, but later ones might (since
    # they have less constraints); also note that only recent LVM
    # supports 'cling'
    for alloc_policy in "contiguous", "cling", "normal":
      result = utils.RunCmd(["lvextend", "--alloc", alloc_policy,
                             "-L", "+%dm" % amount, self.dev_path])
      if not result.failed:
        return
    raise errors.BlockDeviceError("Can't grow LV %s: %s" %
                                  (self.dev_path, result.output))
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class DRBD8Status(object):
  """A DRBD status representation class.

  Note that this doesn't support unconfigured devices (cs:Unconfigured).

  """
  LINE_RE = re.compile(r"\s*[0-9]+:\s*cs:(\S+)\s+st:([^/]+)/(\S+)"
                       "\s+ds:([^/]+)/(\S+)\s+.*$")
  SYNC_RE = re.compile(r"^.*\ssync'ed:\s*([0-9.]+)%.*"
                       "\sfinish: ([0-9]+):([0-9]+):([0-9]+)\s.*$")

  def __init__(self, procline):
    m = self.LINE_RE.match(procline)
    if not m:
      raise errors.BlockDeviceError("Can't parse input data '%s'" % procline)
    self.cstatus = m.group(1)
    self.lrole = m.group(2)
    self.rrole = m.group(3)
    self.ldisk = m.group(4)
    self.rdisk = m.group(5)

    self.is_standalone = self.cstatus == "StandAlone"
    self.is_wfconn = self.cstatus == "WFConnection"
    self.is_connected = self.cstatus == "Connected"
    self.is_primary = self.lrole == "Primary"
    self.is_secondary = self.lrole == "Secondary"
    self.peer_primary = self.rrole == "Primary"
    self.peer_secondary = self.rrole == "Secondary"
    self.both_primary = self.is_primary and self.peer_primary
    self.both_secondary = self.is_secondary and self.peer_secondary

    self.is_diskless = self.ldisk == "Diskless"
    self.is_disk_uptodate = self.ldisk == "UpToDate"

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    self.is_in_resync = self.cstatus in ('SyncSource', 'SyncTarget')

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    m = self.SYNC_RE.match(procline)
    if m:
      self.sync_percent = float(m.group(1))
      hours = int(m.group(2))
      minutes = int(m.group(3))
      seconds = int(m.group(4))
      self.est_time = hours * 3600 + minutes * 60 + seconds
    else:
      self.sync_percent = None
      self.est_time = None

    self.is_sync_target = self.peer_sync_source = self.cstatus == "SyncTarget"
    self.peer_sync_target = self.is_sync_source = self.cstatus == "SyncSource"
    self.is_resync = self.is_sync_target or self.is_sync_source


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class BaseDRBD(BlockDev):
  """Base DRBD class.
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  This class contains a few bits of common functionality between the
  0.7 and 8.x versions of DRBD.

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  """
  _VERSION_RE = re.compile(r"^version: (\d+)\.(\d+)\.(\d+)"
                           r" \(api:(\d+)/proto:(\d+)(?:-(\d+))?\)")
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  _DRBD_MAJOR = 147
  _ST_UNCONFIGURED = "Unconfigured"
  _ST_WFCONNECTION = "WFConnection"
  _ST_CONNECTED = "Connected"
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  _STATUS_FILE = "/proc/drbd"

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  @staticmethod
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  def _GetProcData(filename=_STATUS_FILE):
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    """Return data from /proc/drbd.
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    """
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    stat = open(filename, "r")
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    try:
      data = stat.read().splitlines()
    finally:
      stat.close()
    if not data:
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      raise errors.BlockDeviceError("Can't read any data from %s" % filename)
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    return data
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  @staticmethod
  def _MassageProcData(data):
    """Transform the output of _GetProdData into a nicer form.
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    @return: a dictionary of minor: joined lines from /proc/drbd
        for that minor
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    """
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    lmatch = re.compile("^ *([0-9]+):.*$")
    results = {}
    old_minor = old_line = None
    for line in data:
      lresult = lmatch.match(line)
      if lresult is not None:
        if old_minor is not None:
          results[old_minor] = old_line
        old_minor = int(lresult.group(1))
        old_line = line
      else:
        if old_minor is not None:
          old_line += " " + line.strip()
    # add last line
    if old_minor is not None:
      results[old_minor] = old_line
    return results
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  @classmethod
  def _GetVersion(cls):
    """Return the DRBD version.
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    This will return a dict with keys:
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      - k_major
      - k_minor
      - k_point
      - api
      - proto
      - proto2 (only on drbd > 8.2.X)
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    """
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    proc_data = cls._GetProcData()
    first_line = proc_data[0].strip()
    version = cls._VERSION_RE.match(first_line)
    if not version:
      raise errors.BlockDeviceError("Can't parse DRBD version from '%s'" %
                                    first_line)
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    values = version.groups()
    retval = {'k_major': int(values[0]),
              'k_minor': int(values[1]),
              'k_point': int(values[2]),
              'api': int(values[3]),
              'proto': int(values[4]),
             }
    if values[5] is not None:
      retval['proto2'] = values[5]
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    return retval

  @staticmethod
  def _DevPath(minor):
    """Return the path to a drbd device for a given minor.
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    """
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    return "/dev/drbd%d" % minor
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  @classmethod
  def _GetUsedDevs(cls):
    """Compute the list of used DRBD devices.
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    """
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    data = cls._GetProcData()
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    used_devs = {}
    valid_line = re.compile("^ *([0-9]+): cs:([^ ]+).*$")
    for line in data:
      match = valid_line.match(line)
      if not match:
        continue
      minor = int(match.group(1))
      state = match.group(2)
      if state == cls._ST_UNCONFIGURED:
        continue
      used_devs[minor] = state, line
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    return used_devs
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  def _SetFromMinor(self, minor):
    """Set our parameters based on the given minor.
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    This sets our minor variable and our dev_path.
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    """
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    if minor is None:
      self.minor = self.dev_path = None
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      self.attached = False
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    else:
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      self.minor = minor
      self.dev_path = self._DevPath(minor)
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      self.attached = True
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  @staticmethod
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  def _CheckMetaSize(meta_device):
    """Check if the given meta device looks like a valid one.
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    This currently only check the size, which must be around
    128MiB.
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    """
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    result = utils.RunCmd(["blockdev", "--getsize", meta_device])
    if result.failed:
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      logging.error("Failed to get device size: %s - %s",
                    result.fail_reason, result.output)
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      return False
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    try:
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      sectors = int(result.stdout)
    except ValueError:
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      logging.error("Invalid output from blockdev: '%s'", result.stdout)
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      return False
    bytes = sectors * 512
    if bytes < 128 * 1024 * 1024: # less than 128MiB
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      logging.error("Meta device too small (%.2fMib)", (bytes / 1024 / 1024))
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      return False
    if bytes > (128 + 32) * 1024 * 1024: # account for an extra (big) PE on LVM
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      logging.error("Meta device too big (%.2fMiB)", (bytes / 1024 / 1024))
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      return False
    return True
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  def Rename(self, new_id):
    """Rename a device.
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    This is not supported for drbd devices.
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    """
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    raise errors.ProgrammerError("Can't rename a drbd device")
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class DRBD8(BaseDRBD):
  """DRBD v8.x block device.

  This implements the local host part of the DRBD device, i.e. it
  doesn't do anything to the supposed peer. If you need a fully
  connected DRBD pair, you need to use this class on both hosts.

  The unique_id for the drbd device is the (local_ip, local_port,
  remote_ip, remote_port) tuple, and it must have two children: the
  data device and the meta_device. The meta device is checked for
  valid size and is zeroed on create.

  """
  _MAX_MINORS = 255
  _PARSE_SHOW = None

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  # timeout constants
  _NET_RECONFIG_TIMEOUT = 60

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  def __init__(self, unique_id, children):
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    if children and children.count(None) > 0:
      children = []
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    super(DRBD8, self).__init__(unique_id, children)
    self.major = self._DRBD_MAJOR
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    version = self._GetVersion()
    if version['k_major'] != 8 :
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      raise errors.BlockDeviceError("Mismatch in DRBD kernel version and"
                                    " requested ganeti usage: kernel is"
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                                    " %s.%s, ganeti wants 8.x" %
                                    (version['k_major'], version['k_minor']))
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    if len(children) not in (0, 2):
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      raise ValueError("Invalid configuration data %s" % str(children))
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    if not isinstance(unique_id, (tuple, list)) or len(unique_id) != 6:
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      raise ValueError("Invalid configuration data %s" % str(unique_id))
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    (self._lhost, self._lport,
     self._rhost, self._rport,
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     self._aminor, self._secret) = unique_id
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    if (self._lhost is not None and self._lhost == self._rhost and
        self._lport == self._rport):
      raise ValueError("Invalid configuration data, same local/remote %s" %
                       (unique_id,))
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    self.Attach()

  @classmethod
  def _InitMeta(cls, minor, dev_path):
    """Initialize a meta device.

    This will not work if the given minor is in use.

    """
    result = utils.RunCmd(["drbdmeta", "--force", cls._DevPath(minor),
                           "v08", dev_path, "0", "create-md"])
    if result.failed:
      raise errors.BlockDeviceError("Can't initialize meta device: %s" %
                                    result.output)

  @classmethod
  def _FindUnusedMinor(cls):
    """Find an unused DRBD device.

    This is specific to 8.x as the minors are allocated dynamically,
    so non-existing numbers up to a max minor count are actually free.

    """
    data = cls._GetProcData()

    unused_line = re.compile("^ *([0-9]+): cs:Unconfigured$")
    used_line = re.compile("^ *([0-9]+): cs:")
    highest = None
    for line in data:
      match = unused_line.match(line)
      if match:
        return int(match.group(1))
      match = used_line.match(line)
      if match:
        minor = int(match.group(1))
        highest = max(highest, minor)
    if highest is None: # there are no minors in use at all
      return 0
    if highest >= cls._MAX_MINORS:
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      logging.error("Error: no free drbd minors!")
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      raise errors.BlockDeviceError("Can't find a free DRBD minor")
    return highest + 1

  @classmethod
  def _IsValidMeta(cls, meta_device):
    """Check if the given meta device looks like a valid one.

    """
    minor = cls._FindUnusedMinor()
    minor_path = cls._DevPath(minor)
    result = utils.RunCmd(["drbdmeta", minor_path,
                           "v08", meta_device, "0",
                           "dstate"])
    if result.failed:
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      logging.error("Invalid meta device %s: %s", meta_device, result.output)
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      return False
    return True

  @classmethod
  def _GetShowParser(cls):
    """Return a parser for `drbd show` output.

    This will either create or return an already-create parser for the
    output of the command `drbd show`.

    """
    if cls._PARSE_SHOW is not None:
      return cls._PARSE_SHOW

    # pyparsing setup
    lbrace = pyp.Literal("{").suppress()
    rbrace = pyp.Literal("}").suppress()
    semi = pyp.Literal(";").suppress()
    # this also converts the value to an int
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    number = pyp.Word(pyp.nums).setParseAction(lambda s, l, t: int(t[0]))
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    comment = pyp.Literal ("#") + pyp.Optional(pyp.restOfLine)
    defa = pyp.Literal("_is_default").suppress()
    dbl_quote = pyp.Literal('"').suppress()

    keyword = pyp.Word(pyp.alphanums + '-')

    # value types
    value = pyp.Word(pyp.alphanums + '_-/.:')
    quoted = dbl_quote + pyp.CharsNotIn('"') + dbl_quote
    addr_port = (pyp.Word(pyp.nums + '.') + pyp.Literal(':').suppress() +
                 number)
    # meta device, extended syntax
    meta_value = ((value ^ quoted) + pyp.Literal('[').suppress() +
                  number + pyp.Word(']').suppress())

    # a statement
    stmt = (~rbrace + keyword + ~lbrace +
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            pyp.Optional(addr_port ^ value ^ quoted ^ meta_value) +
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            pyp.Optional(defa) + semi +
            pyp.Optional(pyp.restOfLine).suppress())

    # an entire section
    section_name = pyp.Word(pyp.alphas + '_')
    section = section_name + lbrace + pyp.ZeroOrMore(pyp.Group(stmt)) + rbrace

    bnf = pyp.ZeroOrMore(pyp.Group(section ^ stmt))
    bnf.ignore(comment)

    cls._PARSE_SHOW = bnf

    return bnf

  @classmethod
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  def _GetShowData(cls, minor):
    """Return the `drbdsetup show` data for a minor.
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    """
    result = utils.RunCmd(["drbdsetup", cls._DevPath(minor), "show"])
    if result.failed:
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      logging.error("Can't display the drbd config: %s - %s",
                    result.fail_reason, result.output)
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      return None
    return result.stdout

  @classmethod
  def _GetDevInfo(cls, out):
    """Parse details about a given DRBD minor.

    This return, if available, the local backing device (as a path)
    and the local and remote (ip, port) information from a string
    containing the output of the `drbdsetup show` command as returned
    by _GetShowData.

    """
    data = {}
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    if not out:
      return data

    bnf = cls._GetShowParser()
    # run pyparse

    try:
      results = bnf.parseString(out)
    except pyp.ParseException, err:
      raise errors.BlockDeviceError("Can't parse drbdsetup show output: %s" %
                                    str(err))

    # and massage the results into our desired format
    for section in results:
      sname = section[0]
      if sname == "_this_host":
        for lst in section[1:]:
          if lst[0] == "disk":
            data["local_dev"] = lst[1]
          elif lst[0] == "meta-disk":
            data["meta_dev"] = lst[1]
            data["meta_index"] = lst[2]
          elif lst[0] == "address":
            data["local_addr"] = tuple(lst[1:])
      elif sname == "_remote_host":
        for lst in section[1:]:
          if lst[0] == "address":
            data["remote_addr"] = tuple(lst[1:])
    return data

  def _MatchesLocal(self, info):
    """Test if our local config matches with an existing device.

    The parameter should be as returned from `_GetDevInfo()`. This
    method tests if our local backing device is the same as the one in
    the info parameter, in effect testing if we look like the given
    device.

    """
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    if self._children:
      backend, meta = self._children
    else:
      backend = meta = None

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    if backend is not None:
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      retval = ("local_dev" in info and info["local_dev"] == backend.dev_path)
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    else:
      retval = ("local_dev" not in info)
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    if meta is not None:
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      retval = retval and ("meta_dev" in info and
                           info["meta_dev"] == meta.dev_path)
      retval = retval and ("meta_index" in info and
                           info["meta_index"] == 0)
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    else:
      retval = retval and ("meta_dev" not in info and
                           "meta_index" not in info)
    return retval

  def _MatchesNet(self, info):
    """Test if our network config matches with an existing device.

    The parameter should be as returned from `_GetDevInfo()`. This
    method tests if our network configuration is the same as the one
    in the info parameter, in effect testing if we look like the given
    device.

    """
    if (((self._lhost is None and not ("local_addr" in info)) and
         (self._rhost is None and not ("remote_addr" in info)))):
      return True

    if self._lhost is None:
      return False

    if not ("local_addr" in info and
            "remote_addr" in info):
      return False

    retval = (info["local_addr"] == (self._lhost, self._lport))
    retval = (retval and
              info["remote_addr"] == (self._rhost, self._rport))
    return retval

  @classmethod
  def _AssembleLocal(cls, minor, backend, meta):
    """Configure the local part of a DRBD device.

    This is the first thing that must be done on an unconfigured DRBD
    device. And it must be done only once.

    """
    if not cls._IsValidMeta(meta):
      return False
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    args = ["drbdsetup", cls._DevPath(minor), "disk",
            backend, meta, "0", "-e", "detach", "--create-device"]
    result = utils.RunCmd(args)
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    if result.failed:
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      logging.error("Can't attach local disk: %s", result.output)
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    return not result.failed

  @classmethod
  def _AssembleNet(cls, minor, net_info, protocol,
                   dual_pri=False, hmac=None, secret=None):
    """Configure the network part of the device.

    """
    lhost, lport, rhost, rport = net_info
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    if None in net_info:
      # we don't want network connection and actually want to make
      # sure its shutdown
      return cls._ShutdownNet(minor)

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    # Workaround for a race condition. When DRBD is doing its dance to
    # establish a connection with its peer, it also sends the
    # synchronization speed over the wire. In some cases setting the
    # sync speed only after setting up both sides can race with DRBD
    # connecting, hence we set it here before telling DRBD anything
    # about its peer.
    cls._SetMinorSyncSpeed(minor, constants.SYNC_SPEED)

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    args = ["drbdsetup", cls._DevPath(minor), "net",
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            "%s:%s" % (lhost, lport), "%s:%s" % (rhost, rport), protocol,
            "-A", "discard-zero-changes",
            "-B", "consensus",
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    if dual_pri:
      args.append("-m")
    if hmac and secret:
      args.extend(["-a", hmac, "-x", secret])
    result = utils.RunCmd(args)
    if result.failed:
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      logging.error("Can't setup network for dbrd device: %s - %s",
                    result.fail_reason, result.output)
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      return False

    timeout = time.time() + 10
    ok = False
    while time.time() < timeout:
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      info = cls._GetDevInfo(cls._GetShowData(minor))
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      if not "local_addr" in info or not "remote_addr" in info:
        time.sleep(1)
        continue
      if (info["local_addr"] != (lhost, lport) or
          info["remote_addr"] != (rhost, rport)):
        time.sleep(1)
        continue
      ok = True
      break
    if not ok:
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      logging.error("Timeout while configuring network")
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      return False
    return True

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  def AddChildren(self, devices):
    """Add a disk to the DRBD device.

    """
    if self.minor is None:
      raise errors.BlockDeviceError("Can't attach to dbrd8 during AddChildren")
    if len(devices) != 2:
      raise errors.BlockDeviceError("Need two devices for AddChildren")
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    info = self._GetDevInfo(self._GetShowData(self.minor))
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    if "local_dev" in info:
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      raise errors.BlockDeviceError("DRBD8 already attached to a local disk")
    backend, meta = devices
    if backend.dev_path is None or meta.dev_path is None:
      raise errors.BlockDeviceError("Children not ready during AddChildren")
    backend.Open()
    meta.Open()
    if not self._CheckMetaSize(meta.dev_path):
      raise errors.BlockDeviceError("Invalid meta device size")
    self._InitMeta(self._FindUnusedMinor(), meta.dev_path)
    if not self._IsValidMeta(meta.dev_path):
      raise errors.BlockDeviceError("Cannot initalize meta device")

    if not self._AssembleLocal(self.minor, backend.dev_path, meta.dev_path):
      raise errors.BlockDeviceError("Can't attach to local storage")
    self._children = devices

  def RemoveChildren(self, devices):
    """Detach the drbd device from local storage.

    """
    if self.minor is None:
      raise errors.BlockDeviceError("Can't attach to drbd8 during"
                                    " RemoveChildren")
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    # early return if we don't actually have backing storage
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    info = self._GetDevInfo(self._GetShowData(self.minor))
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    if "local_dev" not in info:
      return
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    if len(self._children) != 2:
      raise errors.BlockDeviceError("We don't have two children: %s" %
                                    self._children)
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    if self._children.count(None) == 2: # we don't actually have children :)
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      logging.error("Requested detach while detached")
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      return
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    if len(devices) != 2:
      raise errors.BlockDeviceError("We need two children in RemoveChildren")
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    for child, dev in zip(self._children, devices):
      if dev != child.dev_path:
        raise errors.BlockDeviceError("Mismatch in local storage"
                                      " (%s != %s) in RemoveChildren" %
                                      (dev, child.dev_path))
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    if not self._ShutdownLocal(self.minor):
      raise errors.BlockDeviceError("Can't detach from local storage")
    self._children = []

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  @classmethod
  def _SetMinorSyncSpeed(cls, minor, kbytes):
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    """Set the speed of the DRBD syncer.

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    This is the low-level implementation.

    @type minor: int
    @param minor: the drbd minor whose settings we change
    @type kbytes: int
    @param kbytes: the speed in kbytes/second
    @rtype: boolean
    @return: the success of the operation

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    """
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    result = utils.RunCmd(["drbdsetup", cls._DevPath(minor), "syncer",
                           "-r", "%d" % kbytes, "--create-device"])
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    if result.failed:
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      logging.error("Can't change syncer rate: %s - %s",
                    result.fail_reason, result.output)
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    return not result.failed

  def SetSyncSpeed(self, kbytes):
    """Set the speed of the DRBD syncer.

    @type kbytes: int
    @param kbytes: the speed in kbytes/second
    @rtype: boolean
    @return: the success of the operation

    """
    if self.minor is None:
      logging.info("Not attached during SetSyncSpeed")
      return False
    children_result = super(DRBD8, self).SetSyncSpeed(kbytes)
    return self._SetMinorSyncSpeed(self.minor, kbytes) and children_result
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  def GetProcStatus(self):
    """Return device data from /proc.

    """
    if self.minor is None:
      raise errors.BlockDeviceError("GetStats() called while not attached")
    proc_info = self._MassageProcData(self._GetProcData())
    if self.minor not in proc_info:
      raise errors.BlockDeviceError("Can't find myself in /proc (minor %d)" %
                                    self.minor)
    return DRBD8Status(proc_info[self.minor])

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  def GetSyncStatus(self):
    """Returns the sync status of the device.


    If sync_percent is None, it means all is ok
    If estimated_time is None, it means we can't esimate
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    the time needed, otherwise it's the time left in seconds.


    We set the is_degraded parameter to True on two conditions:
    network not connected or local disk missing.

    We compute the ldisk parameter based on wheter we have a local
    disk or not.
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    @rtype: tuple
    @return: (sync_percent, estimated_time, is_degraded, ldisk)

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    """
    if self.minor is None and not self.Attach():
      raise errors.BlockDeviceError("Can't attach to device in GetSyncStatus")
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    stats = self.GetProcStatus()
    ldisk = not stats.is_disk_uptodate
    is_degraded = not stats.is_connected
    return stats.sync_percent, stats.est_time, is_degraded or ldisk, ldisk
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  def Open(self, force=False):
    """Make the local state primary.

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    If the 'force' parameter is given, the '-o' option is passed to
    drbdsetup. Since this is a potentially dangerous operation, the
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    force flag should be only given after creation, when it actually
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    is mandatory.
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    """
    if self.minor is None and not self.Attach():
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      logging.error("DRBD cannot attach to a device during open")
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      return False
    cmd = ["drbdsetup", self.dev_path, "primary"]
    if force:
      cmd.append("-o")
    result = utils.RunCmd(cmd)
    if result.failed:
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      msg = ("Can't make drbd device primary: %s" % result.output)
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      logging.error(msg)
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      raise errors.BlockDeviceError(msg)
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  def Close(self):
    """Make the local state secondary.

    This will, of course, fail if the device is in use.

    """
    if self.minor is None and not self.Attach():
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      logging.info("Instance not attached to a device")
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      raise errors.BlockDeviceError("Can't find device")
    result = utils.RunCmd(["drbdsetup", self.dev_path, "secondary"])
    if result.failed:
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      msg = ("Can't switch drbd device to"
             " secondary: %s" % result.output)
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      logging.error(msg)
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      raise errors.BlockDeviceError(msg)
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  def DisconnectNet(self):
    """Removes network configuration.

    This method shutdowns the network side of the device.

    The method will wait up to a hardcoded timeout for the device to
    go into standalone after the 'disconnect' command before
    re-configuring it, as sometimes it takes a while for the
    disconnect to actually propagate and thus we might issue a 'net'
    command while the device is still connected. If the device will
    still be attached to the network and we time out, we raise an
    exception.

    """
    if self.minor is None:
      raise errors.BlockDeviceError("DRBD disk not attached in re-attach net")

    if None in (self._lhost, self._lport, self._rhost, self._rport):
      raise errors.BlockDeviceError("DRBD disk missing network info in"
                                    " DisconnectNet()")

    ever_disconnected = self._ShutdownNet(self.minor)
    timeout_limit = time.time() + self._NET_RECONFIG_TIMEOUT
    sleep_time = 0.100 # we start the retry time at 100 miliseconds
    while time.time() < timeout_limit:
      status = self.GetProcStatus()
      if status.is_standalone:
        break
      # retry the disconnect, it seems possible that due to a
      # well-time disconnect on the peer, my disconnect command might
      # be ingored and forgotten
      ever_disconnected = self._ShutdownNet(self.minor) or ever_disconnected
      time.sleep(sleep_time)
      sleep_time = min(2, sleep_time * 1.5)

    if not status.is_standalone:
      if ever_disconnected:
        msg = ("Device did not react to the"
               " 'disconnect' command in a timely manner")
      else:
        msg = ("Can't shutdown network, even after multiple retries")
      raise errors.BlockDeviceError(msg)

    reconfig_time = time.time() - timeout_limit + self._NET_RECONFIG_TIMEOUT
    if reconfig_time > 15: # hardcoded alert limit
      logging.debug("DRBD8.DisconnectNet: detach took %.3f seconds",
                    reconfig_time)

  def AttachNet(self, multimaster):
    """Reconnects the network.

    This method connects the network side of the device with a
    specified multi-master flag. The device needs to be 'Standalone'
    but have valid network configuration data.

    Args:
      - multimaster: init the network in dual-primary mode

    """
    if self.minor is None:
      raise errors.BlockDeviceError("DRBD disk not attached in AttachNet")

    if None in (self._lhost, self._lport, self._rhost, self._rport):
      raise errors.BlockDeviceError("DRBD disk missing network info in"
                                    " AttachNet()")

    status = self.GetProcStatus()

    if not status.is_standalone:
      raise errors.BlockDeviceError("Device is not standalone in AttachNet")

    return self._AssembleNet(self.minor,
                             (self._lhost, self._lport,
                              self._rhost, self._rport),
                             "C", dual_pri=multimaster)

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  def Attach(self):
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    """Check if our minor is configured.

    This doesn't do any device configurations - it only checks if the
    minor is in a state different from Unconfigured.

    Note that this function will not change the state of the system in
    any way (except in case of side-effects caused by reading from
    /proc).

    """
    used_devs = self._GetUsedDevs()
    if self._aminor in used_devs:
      minor = self._aminor
    else:
      minor = None

    self._SetFromMinor(minor)
    return minor is not None

  def Assemble(self):
    """Assemble the drbd.

    Method:
      - if we have a configured device, we try to ensure that it matches
        our config
      - if not, we create it from zero

    """
    result = super(DRBD8, self).Assemble()
    if not result:
      return result

    self.Attach()
    if self.minor is None:
      # local device completely unconfigured
      return self._FastAssemble()
    else:
      # we have to recheck the local and network status and try to fix
      # the device
      return self._SlowAssemble()

  def _SlowAssemble(self):
    """Assembles the DRBD device from a (partially) configured device.
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    In case of partially attached (local device matches but no network
    setup), we perform the network attach. If successful, we re-test
    the attach if can return success.

    """
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    for minor in (self._aminor,):
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      info = self._GetDevInfo(self._GetShowData(minor))
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      match_l = self._MatchesLocal(info)
      match_r = self._MatchesNet(info)
      if match_l and match_r:
        break
      if match_l and not match_r and "local_addr" not in info:
        res_r = self._AssembleNet(minor,
                                  (self._lhost, self._lport,
                                   self._rhost, self._rport),
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                                  constants.DRBD_NET_PROTOCOL,
                                  hmac=constants.DRBD_HMAC_ALG,
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                                  secret=self._secret
                                  )
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        if res_r:
          if self._MatchesNet(self._GetDevInfo(self._GetShowData(minor))):
            break
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      # the weakest case: we find something that is only net attached
      # even though we were passed some children at init time
      if match_r and "local_dev" not in info:
        break
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      # this case must be considered only if we actually have local
      # storage, i.e. not in diskless mode, because all diskless
      # devices are equal from the point of view of local
      # configuration
      if (match_l and "local_dev" in info and
          not match_r and "local_addr" in info):
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        # strange case - the device network part points to somewhere
        # else, even though its local storage is ours; as we own the
        # drbd space, we try to disconnect from the remote peer and
        # reconnect to our correct one
        if not self._ShutdownNet(minor):
          raise errors.BlockDeviceError("Device has correct local storage,"
                                        " wrong remote peer and is unable to"
                                        " disconnect in order to attach to"
                                        " the correct peer")
        # note: _AssembleNet also handles the case when we don't want
        # local storage (i.e. one or more of the _[lr](host|port) is
        # None)
        if (self._AssembleNet(minor, (self._lhost, self._lport,
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                                      self._rhost, self._rport),
                              constants.DRBD_NET_PROTOCOL,
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                              hmac=constants.DRBD_HMAC_ALG,
                              secret=self._secret) and
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            self._MatchesNet(self._GetDevInfo(self._GetShowData(minor)))):
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          break

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    else:
      minor = None

    self._SetFromMinor(minor)
    return minor is not None

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  def _FastAssemble(self):
    """Assemble the drbd device from zero.
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    This is run when in Assemble we detect our minor is unused.
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    """
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    # TODO: maybe completely tear-down the minor (drbdsetup ... down)
    # before attaching our own?
    minor = self._aminor
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    need_localdev_teardown = False
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    if self._children and self._children[0] and self._children[1]:
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      result = self._AssembleLocal(minor, self._children[0].dev_path,
                                   self._children[1].dev_path)
      if not result:
        return False
      need_localdev_teardown = True
    if self._lhost and self._lport and self._rhost and self._rport:
      result = self._AssembleNet(minor,
                                 (self._lhost, self._lport,
                                  self._rhost, self._rport),
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                                 constants.DRBD_NET_PROTOCOL,
                                 hmac=constants.DRBD_HMAC_ALG,
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                                 secret=self._secret)
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      if not result:
        if need_localdev_teardown:
          # we will ignore failures from this
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          logging.error("net setup failed, tearing down local device")
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          self._ShutdownAll(minor)
        return False
    self._SetFromMinor(minor)
    return True

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  @classmethod
  def _ShutdownLocal(cls, minor):
    """Detach from the local device.

    I/Os will continue to be served from the remote device. If we
    don't have a remote device, this operation will fail.

    """
    result = utils.RunCmd(["drbdsetup", cls._DevPath(minor), "detach"])
    if result.failed:
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      logging.error("Can't detach local device: %s", result.output)
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    return not result.failed

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  @classmethod
  def _ShutdownNet(cls, minor):
    """Disconnect from the remote peer.

    This fails if we don't have a local device.

    """
    result = utils.RunCmd(["drbdsetup", cls._DevPath(minor), "disconnect"])
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    if result.failed:
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      logging.error("Can't shutdown network: %s", result.output)
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    return not result.failed

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  @classmethod
  def _ShutdownAll(cls, minor):
    """Deactivate the device.

    This will, of course, fail if the device is in use.

    """
    result = utils.RunCmd(["drbdsetup", cls._DevPath(minor), "down"])
    if result.failed:
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      logging.error("Can't shutdown drbd device: %s", result.output)
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    return not result.failed

  def Shutdown(self):
    """Shutdown the DRBD device.

    """
    if self.minor is None and not self.Attach():
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