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"""Block device abstraction - base class and utility functions"""

import logging

from ganeti import objects

from ganeti import constants

from ganeti import utils

from ganeti import errors

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 attachment 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, params):

    self._children = children

    self.dev_path = None

    self.unique_id = unique_id

    self.major = None

    self.minor = None

    self.attached = False

    self.size = size

    self.params = params

  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, params, excl_stor):

    """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 SetSyncParams(self, params):

    """Adjust the synchronization parameters of the mirror.

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

    @param params: dictionary of LD level disk parameters related to the

    synchronization.

    @rtype: list

    @return: a list of error messages, emitted both by the current node and by

    children. An empty list means no errors.

    """

    result = []

    if self._children:

      for child in self._children:

        result.extend(child.SetSyncParams(params))

    return result

  def PauseResumeSync(self, pause):

    """Pause/Resume the sync of the mirror.

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

    @param pause: Whether to pause or resume

    """

    result = True

    if self._children:

      for child in self._children:

        result = result and child.PauseResumeSync(pause)

    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, dryrun, backingstore):

    """Grow the block device.

    @type amount: integer

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

    @type dryrun: boolean

    @param dryrun: whether to execute the operation in simulation mode

        only, without actually increasing the size

    @param backingstore: whether to execute the operation on backing storage

        only, or on "logical" storage only; e.g. DRBD is logical storage,

        whereas LVM, file, RBD are backing storage

    """

    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))

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 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