Synnefo » snf-ganeti

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# Copyright (C) 2006, 2007, 2010 Google Inc.

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# General Public License for more details.

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"""Block device abstraction"""

import re

import time

import errno

import pyparsing as pyp

import os

import logging

from ganeti import utils

from ganeti import errors

from ganeti import constants

from ganeti import objects

from ganeti import compat

from ganeti import netutils

# Size of reads in _CanReadDevice

_DEVICE_READ_SIZE = 128 * 1024

def _IgnoreError(fn, *args, **kwargs):

  """Executes the given function, ignoring BlockDeviceErrors.

  This is used in order to simplify the execution of cleanup or

  rollback functions.

  @rtype: boolean

  @return: True when fn didn't raise an exception, False otherwise

  """

  try:

    fn(*args, **kwargs)

    return True

  except errors.BlockDeviceError, err:

    logging.warning("Caught BlockDeviceError but ignoring: %s", str(err))

    return False

def _ThrowError(msg, *args):

  """Log an error to the node daemon and the raise an exception.

  @type msg: string

  @param msg: the text of the exception

  @raise errors.BlockDeviceError

  """

  if args:

    msg = msg % args

  logging.error(msg)

  raise errors.BlockDeviceError(msg)

def _CanReadDevice(path):

  """Check if we can read from the given device.

  This tries to read the first 128k of the device.

  """

  try:

    utils.ReadFile(path, size=_DEVICE_READ_SIZE)

    return True

  except EnvironmentError:

    logging.warning("Can't read from device %s", path, exc_info=True)

    return False

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

  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

  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

  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).

  You can get to a device in two ways:

    - creating the (real) device, which returns you

      an attached instance (lvcreate)

    - 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, size):

    self._children = children

    self.dev_path = None

    self.unique_id = unique_id

    self.major = None

    self.minor = None

    self.attached = False

    self.size = size

  def Assemble(self):

    """Assemble the device from its components.

    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

    """

    pass

  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.

    This makes sense only for some of the device types: LV and file

    storage. Also note that if the device can't attach, the removal

    can't be completed.

    """

    raise NotImplementedError

  def Rename(self, new_id):

    """Rename this device.

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

    """

    raise NotImplementedError

  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.

    If sync_percent is None, it means the device is not syncing.

    If estimated_time is None, it means we can't estimate

    the time needed, otherwise it's the time left in seconds.

    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.

    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).

    @rtype: objects.BlockDevStatus

    """

    return objects.BlockDevStatus(dev_path=self.dev_path,

                                  major=self.major,

                                  minor=self.minor,

                                  sync_percent=None,

                                  estimated_time=None,

                                  is_degraded=False,

                                  ldisk_status=constants.LDS_OKAY)

  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.

    @rtype: objects.BlockDevStatus

    """

    status = self.GetSyncStatus()

    min_percent = status.sync_percent

    max_time = status.estimated_time

    is_degraded = status.is_degraded

    ldisk_status = status.ldisk_status

    if self._children:

      for child in self._children:

        child_status = child.GetSyncStatus()

        if min_percent is None:

          min_percent = child_status.sync_percent

        elif child_status.sync_percent is not None:

          min_percent = min(min_percent, child_status.sync_percent)

        if max_time is None:

          max_time = child_status.estimated_time

        elif child_status.estimated_time is not None:

          max_time = max(max_time, child_status.estimated_time)

        is_degraded = is_degraded or child_status.is_degraded

        if ldisk_status is None:

          ldisk_status = child_status.ldisk_status

        elif child_status.ldisk_status is not None:

          ldisk_status = max(ldisk_status, child_status.ldisk_status)

    return objects.BlockDevStatus(dev_path=self.dev_path,

                                  major=self.major,

                                  minor=self.minor,

                                  sync_percent=min_percent,

                                  estimated_time=max_time,

                                  is_degraded=is_degraded,

                                  ldisk_status=ldisk_status)

  def SetInfo(self, text):

    """Update metadata with info text.

    Only supported for some device types.

    """

    for child in self._children:

      child.SetInfo(text)

  def Grow(self, amount):

    """Grow the block device.

    @param amount: the amount (in mebibytes) to grow with

    """

    raise NotImplementedError

  def GetActualSize(self):

    """Return the actual disk size.

    @note: the device needs to be active when this is called

    """

    assert self.attached, "BlockDevice not attached in GetActualSize()"

    result = utils.RunCmd(["blockdev", "--getsize64", self.dev_path])

    if result.failed:

      _ThrowError("blockdev failed (%s): %s",

                  result.fail_reason, result.output)

    try:

      sz = int(result.output.strip())

    except (ValueError, TypeError), err:

      _ThrowError("Failed to parse blockdev output: %s", str(err))

    return sz

  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.

  """

  _VALID_NAME_RE = re.compile("^[a-zA-Z0-9+_.-]*$")

  _INVALID_NAMES = frozenset([".", "..", "snapshot", "pvmove"])

  _INVALID_SUBSTRINGS = frozenset(["_mlog", "_mimage"])

  def __init__(self, unique_id, children, size):

    """Attaches to a LV device.

    The unique_id is a tuple (vg_name, lv_name)

    """

    super(LogicalVolume, self).__init__(unique_id, children, size)

    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._ValidateName(self._vg_name)

    self._ValidateName(self._lv_name)

    self.dev_path = utils.PathJoin("/dev", self._vg_name, self._lv_name)

    self._degraded = True

    self.major = self.minor = self.pe_size = self.stripe_count = None

    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 errors.ProgrammerError("Invalid configuration data %s" %

                                   str(unique_id))

    vg_name, lv_name = unique_id

    cls._ValidateName(vg_name)

    cls._ValidateName(lv_name)

    pvs_info = cls.GetPVInfo([vg_name])

    if not pvs_info:

      _ThrowError("Can't compute PV info for vg %s", vg_name)

    pvs_info.sort()

    pvs_info.reverse()

    pvlist = [ pv[1] for pv in pvs_info ]

    if compat.any(":" in v for v in pvlist):

      _ThrowError("Some of your PVs have the invalid character ':' in their"

                  " name, this is not supported - please filter them out"

                  " in lvm.conf using either 'filter' or 'preferred_names'")

    free_size = sum([ pv[0] for pv in pvs_info ])

    current_pvs = len(pvlist)

    stripes = min(current_pvs, constants.LVM_STRIPECOUNT)

    # The size constraint should have been checked from the master before

    # calling the create function.

    if free_size < size:

      _ThrowError("Not enough free space: required %s,"

                  " available %s", size, free_size)

    cmd = ["lvcreate", "-L%dm" % size, "-n%s" % lv_name]

    # If the free space is not well distributed, we won't be able to

    # create an optimally-striped volume; in that case, we want to try

    # with N, N-1, ..., 2, and finally 1 (non-stripped) number of

    # stripes

    for stripes_arg in range(stripes, 0, -1):

      result = utils.RunCmd(cmd + ["-i%d" % stripes_arg] + [vg_name] + pvlist)

      if not result.failed:

        break

    if result.failed:

      _ThrowError("LV create failed (%s): %s",

                  result.fail_reason, result.output)

    return LogicalVolume(unique_id, children, size)

  @staticmethod

  def _GetVolumeInfo(lvm_cmd, fields):

    """Returns LVM Volumen infos using lvm_cmd

    @param lvm_cmd: Should be one of "pvs", "vgs" or "lvs"

    @param fields: Fields to return

    @return: A list of dicts each with the parsed fields

    """

    if not fields:

      raise errors.ProgrammerError("No fields specified")

    sep = "|"

    cmd = [lvm_cmd, "--noheadings", "--nosuffix", "--units=m", "--unbuffered",

           "--separator=%s" % sep, "-o%s" % ",".join(fields)]

    result = utils.RunCmd(cmd)

    if result.failed:

      raise errors.CommandError("Can't get the volume information: %s - %s" %

                                (result.fail_reason, result.output))

    data = []

    for line in result.stdout.splitlines():

      splitted_fields = line.strip().split(sep)

      if len(fields) != len(splitted_fields):

        raise errors.CommandError("Can't parse %s output: line '%s'" %

                                  (lvm_cmd, line))

      data.append(splitted_fields)

    return data

  @classmethod

  def GetPVInfo(cls, vg_names, filter_allocatable=True):

    """Get the free space info for PVs in a volume group.

    @param vg_names: list of volume group names, if empty all will be returned

    @param filter_allocatable: whether to skip over unallocatable PVs

    @rtype: list

    @return: list of tuples (free_space, name) with free_space in mebibytes

    """

    try:

      info = cls._GetVolumeInfo("pvs", ["pv_name", "vg_name", "pv_free",

                                        "pv_attr"])

    except errors.GenericError, err:

      logging.error("Can't get PV information: %s", err)

      return None

    data = []

    for pv_name, vg_name, pv_free, pv_attr in info:

      # (possibly) skip over pvs which are not allocatable

      if filter_allocatable and pv_attr[0] != "a":

        continue

      # (possibly) skip over pvs which are not in the right volume group(s)

      if vg_names and vg_name not in vg_names:

        continue

      data.append((float(pv_free), pv_name, vg_name))

    return data

  @classmethod

  def GetVGInfo(cls, vg_names, filter_readonly=True):

    """Get the free space info for specific VGs.

    @param vg_names: list of volume group names, if empty all will be returned

    @param filter_readonly: whether to skip over readonly VGs

    @rtype: list

    @return: list of tuples (free_space, total_size, name) with free_space in

             MiB

    """

    try:

      info = cls._GetVolumeInfo("vgs", ["vg_name", "vg_free", "vg_attr",

                                        "vg_size"])

    except errors.GenericError, err:

      logging.error("Can't get VG information: %s", err)

      return None

    data = []

    for vg_name, vg_free, vg_attr, vg_size in info:

      # (possibly) skip over vgs which are not writable

      if filter_readonly and vg_attr[0] == "r":

        continue

      # (possibly) skip over vgs which are not in the right volume group(s)

      if vg_names and vg_name not in vg_names:

        continue

      data.append((float(vg_free), float(vg_size), vg_name))

    return data

  @classmethod

  def _ValidateName(cls, name):

    """Validates that a given name is valid as VG or LV name.

    The list of valid characters and restricted names is taken out of

    the lvm(8) manpage, with the simplification that we enforce both

    VG and LV restrictions on the names.

    """

    if (not cls._VALID_NAME_RE.match(name) or

        name in cls._INVALID_NAMES or

        compat.any(substring in name for substring in cls._INVALID_SUBSTRINGS)):

      _ThrowError("Invalid LVM name '%s'", name)

  def Remove(self):

    """Remove this logical volume.

    """

    if not self.minor and not self.Attach():

      # the LV does not exist

      return

    result = utils.RunCmd(["lvremove", "-f", "%s/%s" %

                           (self._vg_name, self._lv_name)])

    if result.failed:

      _ThrowError("Can't lvremove: %s - %s", result.fail_reason, result.output)

  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:

      _ThrowError("Failed to rename the logical volume: %s", result.output)

    self._lv_name = new_name

    self.dev_path = utils.PathJoin("/dev", self._vg_name, self._lv_name)

  def Attach(self):

    """Attach to an existing LV.

    This method will try to see if an existing and active LV exists

    which matches our name. If so, its major/minor will be

    recorded.

    """

    self.attached = False

    result = utils.RunCmd(["lvs", "--noheadings", "--separator=,",

                           "--units=m", "--nosuffix",

                           "-olv_attr,lv_kernel_major,lv_kernel_minor,"

                           "vg_extent_size,stripes", self.dev_path])

    if result.failed:

      logging.error("Can't find LV %s: %s, %s",

                    self.dev_path, result.fail_reason, result.output)

      return False

    # the output can (and will) have multiple lines for multi-segment

    # LVs, as the 'stripes' parameter is a segment one, so we take

    # only the last entry, which is the one we're interested in; note

    # that with LVM2 anyway the 'stripes' value must be constant

    # across segments, so this is a no-op actually

    out = result.stdout.splitlines()

    if not out: # totally empty result? splitlines() returns at least

                # one line for any non-empty string

      logging.error("Can't parse LVS output, no lines? Got '%s'", str(out))

      return False

    out = out[-1].strip().rstrip(',')

    out = out.split(",")

    if len(out) != 5:

      logging.error("Can't parse LVS output, len(%s) != 5", str(out))

      return False

    status, major, minor, pe_size, stripes = out

    if len(status) != 6:

      logging.error("lvs lv_attr is not 6 characters (%s)", status)

      return False

    try:

      major = int(major)

      minor = int(minor)

    except (TypeError, ValueError), err:

      logging.error("lvs major/minor cannot be parsed: %s", str(err))

    try:

      pe_size = int(float(pe_size))

    except (TypeError, ValueError), err:

      logging.error("Can't parse vg extent size: %s", err)

      return False

    try:

      stripes = int(stripes)

    except (TypeError, ValueError), err:

      logging.error("Can't parse the number of stripes: %s", err)

      return False

    self.major = major

    self.minor = minor

    self.pe_size = pe_size

    self.stripe_count = stripes

    self._degraded = status[0] == 'v' # virtual volume, i.e. doesn't backing

                                      # storage

    self.attached = True

    return True

  def Assemble(self):

    """Assemble the device.

    We always 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).

    """

    result = utils.RunCmd(["lvchange", "-ay", self.dev_path])

    if result.failed:

      _ThrowError("Can't activate lv %s: %s", self.dev_path, result.output)

  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.

    """

    pass

  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

    case). The is_degraded parameter is the inverse of the ldisk

    parameter.

    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.

    The status was already read in Attach, so we just return it.

    @rtype: objects.BlockDevStatus

    """

    if self._degraded:

      ldisk_status = constants.LDS_FAULTY

    else:

      ldisk_status = constants.LDS_OKAY

    return objects.BlockDevStatus(dev_path=self.dev_path,

                                  major=self.major,

                                  minor=self.minor,

                                  sync_percent=None,

                                  estimated_time=None,

                                  is_degraded=self._degraded,

                                  ldisk_status=ldisk_status)

  def Open(self, force=False):

    """Make the device ready for I/O.

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

    """

    pass

  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.

    """

    pass

  def Snapshot(self, size):

    """Create a snapshot copy of an lvm block device.

    @returns: tuple (vg, lv)

    """

    snap_name = self._lv_name + ".snap"

    # remove existing snapshot if found

    snap = LogicalVolume((self._vg_name, snap_name), None, size)

    _IgnoreError(snap.Remove)

    vg_info = self.GetVGInfo([self._vg_name])

    if not vg_info:

      _ThrowError("Can't compute VG info for vg %s", self._vg_name)

    free_size, _, _ = vg_info[0]

    if free_size < size:

      _ThrowError("Not enough free space: required %s,"

                  " available %s", size, free_size)

    result = utils.RunCmd(["lvcreate", "-L%dm" % size, "-s",

                           "-n%s" % snap_name, self.dev_path])

    if result.failed:

      _ThrowError("command: %s error: %s - %s",

                  result.cmd, result.fail_reason, result.output)

    return (self._vg_name, snap_name)