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# Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Google Inc.

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# General Public License for more details.

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"""Module implementing the job queue handling."""

import errno

import os

from ganeti import constants

from ganeti import errors

from ganeti import runtime

from ganeti import utils

from ganeti import pathutils

JOBS_PER_ARCHIVE_DIRECTORY = 10000

def _ReadNumericFile(file_name):

  """Reads a file containing a number.

  @rtype: None or int

  @return: None if file is not found, otherwise number

  """

  try:

    return int(utils.ReadFile(file_name))

  except EnvironmentError, err:

    if err.errno in (errno.ENOENT, ):

      return None

    raise

def ReadSerial():

  """Read the serial file.

  The queue should be locked while this function is called.

  """

  return _ReadNumericFile(pathutils.JOB_QUEUE_SERIAL_FILE)

def ReadVersion():

  """Read the queue version.

  The queue should be locked while this function is called.

  """

  return _ReadNumericFile(pathutils.JOB_QUEUE_VERSION_FILE)

def InitAndVerifyQueue(must_lock):

  """Open and lock job queue.

  If necessary, the queue is automatically initialized.

  @type must_lock: bool

  @param must_lock: Whether an exclusive lock must be held.

  @rtype: utils.FileLock

  @return: Lock object for the queue. This can be used to change the

           locking mode.

  """

  getents = runtime.GetEnts()

  # Lock queue

  queue_lock = utils.FileLock.Open(pathutils.JOB_QUEUE_LOCK_FILE)

  try:

    # The queue needs to be locked in exclusive mode to write to the serial and

    # version files.

    if must_lock:

      queue_lock.Exclusive(blocking=True)

      holding_lock = True

    else:

      try:

        queue_lock.Exclusive(blocking=False)

        holding_lock = True

      except errors.LockError:

        # Ignore errors and assume the process keeping the lock checked

        # everything.

        holding_lock = False

    if holding_lock:

      # Verify version

      version = ReadVersion()

      if version is None:

        # Write new version file

        utils.WriteFile(pathutils.JOB_QUEUE_VERSION_FILE,

                        uid=getents.masterd_uid, gid=getents.masterd_gid,

                        data="%s\n" % constants.JOB_QUEUE_VERSION)

        # Read again

        version = ReadVersion()

      if version != constants.JOB_QUEUE_VERSION:

        raise errors.JobQueueError("Found job queue version %s, expected %s",

                                   version, constants.JOB_QUEUE_VERSION)

      serial = ReadSerial()

      if serial is None:

        # Write new serial file

        utils.WriteFile(pathutils.JOB_QUEUE_SERIAL_FILE,

                        uid=getents.masterd_uid, gid=getents.masterd_gid,

                        data="%s\n" % 0)

        # Read again

        serial = ReadSerial()

      if serial is None:

        # There must be a serious problem

        raise errors.JobQueueError("Can't read/parse the job queue"

                                   " serial file")

      if not must_lock:

        # There's no need for more error handling. Closing the lock

        # file below in case of an error will unlock it anyway.

        queue_lock.Unlock()

  except:

    queue_lock.Close()

    raise

  return queue_lock

def CheckDrainFlag():

  """Check if the queue is marked to be drained.

  This currently uses the queue drain file, which makes it a per-node flag.

  In the future this can be moved to the config file.

  @rtype: boolean

  @return: True if the job queue is marked drained

  """

  return os.path.exists(pathutils.JOB_QUEUE_DRAIN_FILE)

def SetDrainFlag(drain_flag):

  """Sets the drain flag for the queue.

  @type drain_flag: boolean

  @param drain_flag: Whether to set or unset the drain flag

  @attention: This function should only called the current holder of the queue

    lock

  """

  getents = runtime.GetEnts()

  if drain_flag:

    utils.WriteFile(pathutils.JOB_QUEUE_DRAIN_FILE, data="",

                    uid=getents.masterd_uid, gid=getents.masterd_gid)

  else:

    utils.RemoveFile(pathutils.JOB_QUEUE_DRAIN_FILE)

  assert (not drain_flag) ^ CheckDrainFlag()

def FormatJobID(job_id):

  """Convert a job ID to int format.

  Currently this just is a no-op that performs some checks, but if we

  want to change the job id format this will abstract this change.

  @type job_id: int or long

  @param job_id: the numeric job id

  @rtype: int

  @return: the formatted job id

  """

  if not isinstance(job_id, (int, long)):

    raise errors.ProgrammerError("Job ID '%s' not numeric" % job_id)

  if job_id < 0:

    raise errors.ProgrammerError("Job ID %s is negative" % job_id)

  return job_id

def GetArchiveDirectory(job_id):

  """Returns the archive directory for a job.

  @type job_id: str

  @param job_id: Job identifier

  @rtype: str

  @return: Directory name

  """

  return str(ParseJobId(job_id) / JOBS_PER_ARCHIVE_DIRECTORY)

def ParseJobId(job_id):

  """Parses a job ID and converts it to integer.

  """

  try:

    return int(job_id)

  except (ValueError, TypeError):

    raise errors.ParameterError("Invalid job ID '%s'" % job_id)