Synnefo » snf-ganeti

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#

# Copyright (C) 2006, 2007 Google Inc.

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# This program is free software; you can redistribute it and/or modify

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# the Free Software Foundation; either version 2 of the License, or

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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

# General Public License for more details.

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# You should have received a copy of the GNU General Public License

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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

# 02110-1301, USA.

"""Block device abstraction"""

import re

import time

import errno

import pyparsing as pyp

import os

from ganeti import utils

from ganeti import logger

from ganeti import errors

from ganeti import constants

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 (MD and LV have 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

    - md arrays are created or assembled 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 MD devices,

  the /dev path is dynamic and the unique ID is the UUID generated at

  array creation plus the slave list. 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, mdadm --create)

    - 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

  def Assemble(self):

    """Assemble the device from its components.

    If this is a plain block device (e.g. LVM) than assemble does

    nothing, as the LVM has no children and we don't put logical

    volumes offline.

    One guarantee is 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.

    """

    status = True

    for child in self._children:

      if not isinstance(child, BlockDev):

        raise TypeError("Invalid child passed of type '%s'" % type(child))

      if not status:

        break

      status = status and child.Assemble()

      if not status:

        break

      try:

        child.Open()

      except errors.BlockDeviceError:

        for child in self._children:

          child.Shutdown()

        raise

    if not status:

      for child in self._children:

        child.Shutdown()

    return status

  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 to a

    lesser degree, md devices. 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.

    Returns:

     (sync_percent, estimated_time, is_degraded, ldisk)

    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).

    """

    return None, None, False, False

  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.

    """

    min_percent, max_time, is_degraded, ldisk = self.GetSyncStatus()

    if self._children:

      for child in self._children:

        c_percent, c_time, c_degraded, c_ldisk = child.GetSyncStatus()

        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

        ldisk = ldisk or c_ldisk

    return min_percent, max_time, is_degraded, ldisk

  def SetInfo(self, text):

    """Update metadata with info text.

    Only supported for some device types.

    """

    for child in self._children:

      child.SetInfo(text)

  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)

    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:

      raise errors.BlockDeviceError("Can't compute PV info for vg %s" %

                                    vg_name)

    pvs_info.sort()

    pvs_info.reverse()

    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.

    if free_size < size:

      raise errors.BlockDeviceError("Not enough free space: required %s,"

                                    " available %s" % (size, free_size))

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

                           vg_name] + pvlist)

    if result.failed:

      raise errors.BlockDeviceError(result.fail_reason)

    return LogicalVolume(unique_id, children)

  @staticmethod

  def GetPVInfo(vg_name):

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

    Args:

      vg_name: the volume group name

    Returns:

      list of (free_space, name) with free_space in mebibytes

    """

    command = ["pvs", "--noheadings", "--nosuffix", "--units=m",

               "-opv_name,vg_name,pv_free,pv_attr", "--unbuffered",

               "--separator=:"]

    result = utils.RunCmd(command)

    if result.failed:

      logger.Error("Can't get the PV information: %s" % result.fail_reason)

      return None

    data = []

    for line in result.stdout.splitlines():

      fields = line.strip().split(':')

      if len(fields) != 4:

        logger.Error("Can't parse pvs output: line '%s'" % line)

        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:

      logger.Error("Can't lvremove: %s" % result.fail_reason)

    return not result.failed

  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)

    self._lv_name = new_name

    self.dev_path = "/dev/%s/%s" % (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.

    """

    result = utils.RunCmd(["lvdisplay", self.dev_path])

    if result.failed:

      logger.Error("Can't find LV %s: %s, %s" %

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

      return False

    match = re.compile("^ *Block device *([0-9]+):([0-9]+).*$")

    for line in result.stdout.splitlines():

      match_result = match.match(line)

      if match_result:

        self.major = int(match_result.group(1))

        self.minor = int(match_result.group(2))

        return True

    return False

  def Assemble(self):

    """Assemble the device.

    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).

    """

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

    if result.failed:

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

    return not result.failed

  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

  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.

    Returns:

     (sync_percent, estimated_time, is_degraded, ldisk)

    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.

    """

    result = utils.RunCmd(["lvs", "--noheadings", "-olv_attr", self.dev_path])

    if result.failed:

      logger.Error("Can't display lv: %s" % result.fail_reason)

      return None, None, True, True

    out = result.stdout.strip()

    # format: type/permissions/alloc/fixed_minor/state/open

    if len(out) != 6:

      logger.Debug("Error in lvs output: attrs=%s, len != 6" % out)

      return None, None, True, True

    ldisk = out[0] == 'v' # virtual volume, i.e. doesn't have

                          # backing storage

    return None, None, ldisk, ldisk

  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.

    """

    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:

      raise errors.BlockDeviceError("Can't compute PV info for vg %s" %

                                    self._vg_name)

    pvs_info.sort()

    pvs_info.reverse()

    free_size, pv_name = pvs_info[0]

    if free_size < size:

      raise errors.BlockDeviceError("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:

      raise errors.BlockDeviceError("command: %s error: %s" %

                                    (result.cmd, result.fail_reason))

    return snap_name

  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:

      raise errors.BlockDeviceError("Command: %s error: %s" %

                                    (result.cmd, result.fail_reason))

class MDRaid1(BlockDev):

  """raid1 device implemented via md.

  """

  def __init__(self, unique_id, children):

    super(MDRaid1, self).__init__(unique_id, children)

    self.major = 9

    self.Attach()

  def Attach(self):

    """Find an array which matches our config and attach to it.

    This tries to find a MD array which has the same UUID as our own.

    """

    minor = self._FindMDByUUID(self.unique_id)

    if minor is not None:

      self._SetFromMinor(minor)

    else:

      self.minor = None

      self.dev_path = None

    return (minor is not None)

  @staticmethod

  def _GetUsedDevs():

    """Compute the list of in-use MD devices.

    It doesn't matter if the used device have other raid level, just

    that they are in use.

    """

    mdstat = open("/proc/mdstat", "r")

    data = mdstat.readlines()

    mdstat.close()

    used_md = {}

    valid_line = re.compile("^md([0-9]+) : .*$")

    for line in data:

      match = valid_line.match(line)

      if match:

        md_no = int(match.group(1))

        used_md[md_no] = line

    return used_md

  @staticmethod

  def _GetDevInfo(minor):

    """Get info about a MD device.

    Currently only uuid is returned.

    """

    result = utils.RunCmd(["mdadm", "-D", "/dev/md%d" % minor])

    if result.failed:

      logger.Error("Can't display md: %s" % result.fail_reason)

      return None

    retval = {}

    for line in result.stdout.splitlines():

      line = line.strip()

      kv = line.split(" : ", 1)

      if kv:

        if kv[0] == "UUID":

          retval["uuid"] = kv[1].split()[0]

        elif kv[0] == "State":

          retval["state"] = kv[1].split(", ")

    return retval

  @staticmethod

  def _FindUnusedMinor():

    """Compute an unused MD minor.

    This code assumes that there are 256 minors only.

    """

    used_md = MDRaid1._GetUsedDevs()

    i = 0

    while i < 256:

      if i not in used_md:

        break

      i += 1

    if i == 256:

      logger.Error("Critical: Out of md minor numbers.")

      raise errors.BlockDeviceError("Can't find a free MD minor")

    return i

  @classmethod

  def _FindMDByUUID(cls, uuid):

    """Find the minor of an MD array with a given UUID.

    """

    md_list = cls._GetUsedDevs()

    for minor in md_list:

      info = cls._GetDevInfo(minor)

      if info and info["uuid"] == uuid:

        return minor

    return None

  @staticmethod

  def _ZeroSuperblock(dev_path):

    """Zero the possible locations for an MD superblock.

    The zero-ing can't be done via ``mdadm --zero-superblock`` as that

    fails in versions 2.x with the same error code as non-writable

    device.

    The superblocks are located at (negative values are relative to

    the end of the block device):

      - -128k to end for version 0.90 superblock

      - -8k to -12k for version 1.0 superblock (included in the above)

      - 0k to 4k for version 1.1 superblock

      - 4k to 8k for version 1.2 superblock

    To cover all situations, the zero-ing will be:

      - 0k to 128k

      - -128k to end

    As such, the minimum device size must be 128k, otherwise we'll get

    I/O errors.

    Note that this function depends on the fact that one can open,

    read and write block devices normally.

    """

    overwrite_size = 128 * 1024

    empty_buf = '\0' * overwrite_size

    fd = open(dev_path, "r+")

    try:

      fd.seek(0, 0)

      p1 = fd.tell()

      fd.write(empty_buf)

      p2 = fd.tell()

      logger.Debug("Zeroed %s from %d to %d" % (dev_path, p1, p2))

      fd.seek(-overwrite_size, 2)

      p1 = fd.tell()

      fd.write(empty_buf)

      p2 = fd.tell()

      logger.Debug("Zeroed %s from %d to %d" % (dev_path, p1, p2))

    finally:

      fd.close()

  @classmethod

  def Create(cls, unique_id, children, size):

    """Create a new MD raid1 array.

    """

    if not isinstance(children, (tuple, list)):

      raise ValueError("Invalid setup data for MDRaid1 dev: %s" %

                       str(children))

    for i in children:

      if not isinstance(i, BlockDev):

        raise ValueError("Invalid member in MDRaid1 dev: %s" % type(i))

    for i in children:

      try:

        cls._ZeroSuperblock(i.dev_path)

      except EnvironmentError, err:

        logger.Error("Can't zero superblock for %s: %s" %

                     (i.dev_path, str(err)))

        return None

    minor = cls._FindUnusedMinor()

    result = utils.RunCmd(["mdadm", "--create", "/dev/md%d" % minor,

                           "--auto=yes", "--force", "-l1",

                           "-n%d" % len(children)] +

                          [dev.dev_path for dev in children])

    if result.failed:

      logger.Error("Can't create md: %s: %s" % (result.fail_reason,

                                                result.output))

      return None

    info = cls._GetDevInfo(minor)

    if not info or not "uuid" in info:

      logger.Error("Wrong information returned from mdadm -D: %s" % str(info))

      return None

    return MDRaid1(info["uuid"], children)

  def Remove(self):

    """Stub remove function for MD RAID 1 arrays.

    We don't remove the superblock right now. Mark a to do.

    """

    #TODO: maybe zero superblock on child devices?

    return self.Shutdown()

  def Rename(self, new_id):

    """Rename a device.

    This is not supported for md raid1 devices.

    """

    raise errors.ProgrammerError("Can't rename a md raid1 device")

  def AddChildren(self, devices):

    """Add new member(s) to the md raid1.