Synnefo » snf-ganeti

#

#

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

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# 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.

"""Module keeping state for Ganeti watcher.

"""

import os

import time

import logging

from ganeti import utils

from ganeti import serializer

from ganeti import errors

# Delete any record that is older than 8 hours; this value is based on

# the fact that the current retry counter is 5, and watcher runs every

# 5 minutes, so it takes around half an hour to exceed the retry

# counter, so 8 hours (16*1/2h) seems like a reasonable reset time

RETRY_EXPIRATION = 8 * 3600

KEY_RESTART_COUNT = "restart_count"

KEY_RESTART_WHEN = "restart_when"

KEY_BOOT_ID = "bootid"

def OpenStateFile(path):

  """Opens the state file and acquires a lock on it.

  @type path: string

  @param path: Path to state file

  """

  # The two-step dance below is necessary to allow both opening existing

  # file read/write and creating if not existing. Vanilla open will truncate

  # an existing file -or- allow creating if not existing.

  statefile_fd = os.open(path, os.O_RDWR | os.O_CREAT)

  # Try to acquire lock on state file. If this fails, another watcher instance

  # might already be running or another program is temporarily blocking the

  # watcher from running.

  try:

    utils.LockFile(statefile_fd)

  except errors.LockError, err:

    logging.error("Can't acquire lock on state file %s: %s", path, err)

    return None

  return os.fdopen(statefile_fd, "w+")

class WatcherState(object):

  """Interface to a state file recording restart attempts.

  """

  def __init__(self, statefile):

    """Open, lock, read and parse the file.

    @type statefile: file

    @param statefile: State file object

    """

    self.statefile = statefile

    try:

      state_data = self.statefile.read()

      if not state_data:

        self._data = {}

      else:

        self._data = serializer.Load(state_data)

    except Exception, msg: # pylint: disable=W0703

      # Ignore errors while loading the file and treat it as empty

      self._data = {}

      logging.warning(("Invalid state file. Using defaults."

                       " Error message: %s"), msg)

    if "instance" not in self._data:

      self._data["instance"] = {}

    if "node" not in self._data:

      self._data["node"] = {}

    self._orig_data = serializer.Dump(self._data)

  def Save(self, filename):

    """Save state to file, then unlock and close it.

    """

    assert self.statefile

    serialized_form = serializer.Dump(self._data)

    if self._orig_data == serialized_form:

      logging.debug("Data didn't change, just touching status file")

      os.utime(filename, None)

      return

    # We need to make sure the file is locked before renaming it, otherwise

    # starting ganeti-watcher again at the same time will create a conflict.

    fd = utils.WriteFile(filename,

                         data=serialized_form,

                         prewrite=utils.LockFile, close=False)

    self.statefile = os.fdopen(fd, "w+")

  def Close(self):

    """Unlock configuration file and close it.

    """

    assert self.statefile

    # Files are automatically unlocked when closing them

    self.statefile.close()

    self.statefile = None

  def GetNodeBootID(self, name):

    """Returns the last boot ID of a node or None.

    """

    ndata = self._data["node"]

    if name in ndata and KEY_BOOT_ID in ndata[name]:

      return ndata[name][KEY_BOOT_ID]

    return None

  def SetNodeBootID(self, name, bootid):

    """Sets the boot ID of a node.

    """

    assert bootid

    ndata = self._data["node"]

    ndata.setdefault(name, {})[KEY_BOOT_ID] = bootid

  def NumberOfRestartAttempts(self, instance_name):

    """Returns number of previous restart attempts.

    @type instance_name: string

    @param instance_name: the name of the instance to look up

    """

    idata = self._data["instance"]

    if instance_name in idata:

      return idata[instance_name][KEY_RESTART_COUNT]

    return 0

  def MaintainInstanceList(self, instances):

    """Perform maintenance on the recorded instances.

    @type instances: list of string

    @param instances: the list of currently existing instances

    """

    idict = self._data["instance"]

    # First, delete obsolete instances

    obsolete_instances = set(idict).difference(instances)

    for inst in obsolete_instances:

      logging.debug("Forgetting obsolete instance %s", inst)

      idict.pop(inst, None)

    # Second, delete expired records

    earliest = time.time() - RETRY_EXPIRATION

    expired_instances = [i for i in idict

                         if idict[i][KEY_RESTART_WHEN] < earliest]

    for inst in expired_instances:

      logging.debug("Expiring record for instance %s", inst)

      idict.pop(inst, None)

  def RecordRestartAttempt(self, instance_name):

    """Record a restart attempt.

    @type instance_name: string

    @param instance_name: the name of the instance being restarted

    """

    idata = self._data["instance"]

    inst = idata.setdefault(instance_name, {})

    inst[KEY_RESTART_WHEN] = time.time()

    inst[KEY_RESTART_COUNT] = inst.get(KEY_RESTART_COUNT, 0) + 1

  def RemoveInstance(self, instance_name):

    """Update state to reflect that a machine is running.

    This method removes the record for a named instance (as we only

    track down instances).

    @type instance_name: string

    @param instance_name: the name of the instance to remove from books

    """

    idata = self._data["instance"]

    idata.pop(instance_name, None)