cmdlib.py

#
#

# Copyright (C) 2006, 2007, 2008 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.
#
# 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 implementing the master-side code."""

# pylint: disable-msg=W0201,C0302

# W0201 since most LU attributes are defined in CheckPrereq or similar
# functions

# C0302: since we have waaaay to many lines in this module

import os
import os.path
import time
import re
import platform
import logging
import copy
import OpenSSL

from ganeti import ssh
from ganeti import utils
from ganeti import errors
from ganeti import hypervisor
from ganeti import locking
from ganeti import constants
from ganeti import objects
from ganeti import serializer
from ganeti import ssconf
from ganeti import uidpool
from ganeti import compat
from ganeti import masterd

import ganeti.masterd.instance # pylint: disable-msg=W0611


# Modifiable default values; need to define these here before the
# actual LUs

def _EmptyList():
  """Returns an empty list.

  """
  return []


def _EmptyDict():
  """Returns an empty dict.

  """
  return {}


# Some basic types
def _TNotNone(val):
  """Checks if the given value is not None.

  """
  return val is not None


def _TNone(val):
  """Checks if the given value is None.

  """
  return val is None


def _TBool(val):
  """Checks if the given value is a boolean.

  """
  return isinstance(val, bool)


def _TInt(val):
  """Checks if the given value is an integer.

  """
  return isinstance(val, int)


def _TFloat(val):
  """Checks if the given value is a float.

  """
  return isinstance(val, float)


def _TString(val):
  """Checks if the given value is a string.

  """
  return isinstance(val, basestring)


def _TTrue(val):
  """Checks if a given value evaluates to a boolean True value.

  """
  return bool(val)


def _TElemOf(target_list):
  """Builds a function that checks if a given value is a member of a list.

  """
  return lambda val: val in target_list


# Container types
def _TList(val):
  """Checks if the given value is a list.

  """
  return isinstance(val, list)


def _TDict(val):
  """Checks if the given value is a dictionary.

  """
  return isinstance(val, dict)


# Combinator types
def _TAnd(*args):
  """Combine multiple functions using an AND operation.

  """
  def fn(val):
    return compat.all(t(val) for t in args)
  return fn


def _TOr(*args):
  """Combine multiple functions using an AND operation.

  """
  def fn(val):
    return compat.any(t(val) for t in args)
  return fn


# Type aliases

# non-empty string
_TNEString = _TAnd(_TString, _TTrue)


# positive integer
_TPInt = _TAnd(_TInt, lambda v: v >= 0)


def _TListOf(my_type):
  """Checks if a given value is a list with all elements of the same type.

  """
  return _TAnd(_TList,
               lambda lst: compat.all(lst, my_type))


def _TDictOf(key_type, val_type):
  """Checks a dict type for the type of its key/values.

  """
  return _TAnd(_TDict,
               lambda my_dict: (compat.all(my_dict.keys(), key_type) and
                                compat.all(my_dict.values(), val_type)))


# End types
class LogicalUnit(object):
  """Logical Unit base class.

  Subclasses must follow these rules:
    - implement ExpandNames
    - implement CheckPrereq (except when tasklets are used)
    - implement Exec (except when tasklets are used)
    - implement BuildHooksEnv
    - redefine HPATH and HTYPE
    - optionally redefine their run requirements:
        REQ_BGL: the LU needs to hold the Big Ganeti Lock exclusively

  Note that all commands require root permissions.

  @ivar dry_run_result: the value (if any) that will be returned to the caller
      in dry-run mode (signalled by opcode dry_run parameter)
  @cvar _OP_DEFS: a list of opcode attributes and the defaults values
      they should get if not already existing

  """
  HPATH = None
  HTYPE = None
  _OP_REQP = []
  _OP_DEFS = []
  REQ_BGL = True

  def __init__(self, processor, op, context, rpc):
    """Constructor for LogicalUnit.

    This needs to be overridden in derived classes in order to check op
    validity.

    """
    self.proc = processor
    self.op = op
    self.cfg = context.cfg
    self.context = context
    self.rpc = rpc
    # Dicts used to declare locking needs to mcpu
    self.needed_locks = None
    self.acquired_locks = {}
    self.share_locks = dict.fromkeys(locking.LEVELS, 0)
    self.add_locks = {}
    self.remove_locks = {}
    # Used to force good behavior when calling helper functions
    self.recalculate_locks = {}
    self.__ssh = None
    # logging
    self.LogWarning = processor.LogWarning # pylint: disable-msg=C0103
    self.LogInfo = processor.LogInfo # pylint: disable-msg=C0103
    self.LogStep = processor.LogStep # pylint: disable-msg=C0103
    # support for dry-run
    self.dry_run_result = None
    # support for generic debug attribute
    if (not hasattr(self.op, "debug_level") or
        not isinstance(self.op.debug_level, int)):
      self.op.debug_level = 0

    # Tasklets
    self.tasklets = None

    for aname, aval in self._OP_DEFS:
      if not hasattr(self.op, aname):
        if callable(aval):
          dval = aval()
        else:
          dval = aval
        setattr(self.op, aname, dval)

    for attr_name, test in self._OP_REQP:
      if not hasattr(op, attr_name):
        raise errors.OpPrereqError("Required parameter '%s' missing" %
                                   attr_name, errors.ECODE_INVAL)
      attr_val = getattr(op, attr_name, None)
      if not callable(test):
        raise errors.ProgrammerError("Validation for parameter '%s' failed,"
                                     " given type is not a proper type (%s)" %
                                     (attr_name, test))
      if not test(attr_val):
        raise errors.OpPrereqError("Parameter '%s' has invalid type" %
                                   attr_name, errors.ECODE_INVAL)

    self.CheckArguments()

  def __GetSSH(self):
    """Returns the SshRunner object

    """
    if not self.__ssh:
      self.__ssh = ssh.SshRunner(self.cfg.GetClusterName())
    return self.__ssh

  ssh = property(fget=__GetSSH)

  def CheckArguments(self):
    """Check syntactic validity for the opcode arguments.

    This method is for doing a simple syntactic check and ensure
    validity of opcode parameters, without any cluster-related
    checks. While the same can be accomplished in ExpandNames and/or
    CheckPrereq, doing these separate is better because:

      - ExpandNames is left as as purely a lock-related function
      - CheckPrereq is run after we have acquired locks (and possible
        waited for them)

    The function is allowed to change the self.op attribute so that
    later methods can no longer worry about missing parameters.

    """
    pass

  def ExpandNames(self):
    """Expand names for this LU.

    This method is called before starting to execute the opcode, and it should
    update all the parameters of the opcode to their canonical form (e.g. a
    short node name must be fully expanded after this method has successfully
    completed). This way locking, hooks, logging, ecc. can work correctly.

    LUs which implement this method must also populate the self.needed_locks
    member, as a dict with lock levels as keys, and a list of needed lock names
    as values. Rules:

      - use an empty dict if you don't need any lock
      - if you don't need any lock at a particular level omit that level
      - don't put anything for the BGL level
      - if you want all locks at a level use locking.ALL_SET as a value

    If you need to share locks (rather than acquire them exclusively) at one
    level you can modify self.share_locks, setting a true value (usually 1) for
    that level. By default locks are not shared.

    This function can also define a list of tasklets, which then will be
    executed in order instead of the usual LU-level CheckPrereq and Exec
    functions, if those are not defined by the LU.

    Examples::

      # Acquire all nodes and one instance
      self.needed_locks = {
        locking.LEVEL_NODE: locking.ALL_SET,
        locking.LEVEL_INSTANCE: ['instance1.example.tld'],
      }
      # Acquire just two nodes
      self.needed_locks = {
        locking.LEVEL_NODE: ['node1.example.tld', 'node2.example.tld'],
      }
      # Acquire no locks
      self.needed_locks = {} # No, you can't leave it to the default value None

    """
    # The implementation of this method is mandatory only if the new LU is
    # concurrent, so that old LUs don't need to be changed all at the same
    # time.
    if self.REQ_BGL:
      self.needed_locks = {} # Exclusive LUs don't need locks.
    else:
      raise NotImplementedError

  def DeclareLocks(self, level):
    """Declare LU locking needs for a level

    While most LUs can just declare their locking needs at ExpandNames time,
    sometimes there's the need to calculate some locks after having acquired
    the ones before. This function is called just before acquiring locks at a
    particular level, but after acquiring the ones at lower levels, and permits
    such calculations. It can be used to modify self.needed_locks, and by
    default it does nothing.

    This function is only called if you have something already set in
    self.needed_locks for the level.

    @param level: Locking level which is going to be locked
    @type level: member of ganeti.locking.LEVELS

    """

  def CheckPrereq(self):
    """Check prerequisites for this LU.

    This method should check that the prerequisites for the execution
    of this LU are fulfilled. It can do internode communication, but
    it should be idempotent - no cluster or system changes are
    allowed.

    The method should raise errors.OpPrereqError in case something is
    not fulfilled. Its return value is ignored.

    This method should also update all the parameters of the opcode to
    their canonical form if it hasn't been done by ExpandNames before.

    """
    if self.tasklets is not None:
      for (idx, tl) in enumerate(self.tasklets):
        logging.debug("Checking prerequisites for tasklet %s/%s",
                      idx + 1, len(self.tasklets))
        tl.CheckPrereq()
    else:
      pass

  def Exec(self, feedback_fn):
    """Execute the LU.

    This method should implement the actual work. It should raise
    errors.OpExecError for failures that are somewhat dealt with in
    code, or expected.

    """
    if self.tasklets is not None:
      for (idx, tl) in enumerate(self.tasklets):
        logging.debug("Executing tasklet %s/%s", idx + 1, len(self.tasklets))
        tl.Exec(feedback_fn)
    else:
      raise NotImplementedError

  def BuildHooksEnv(self):
    """Build hooks environment for this LU.

    This method should return a three-node tuple consisting of: a dict
    containing the environment that will be used for running the
    specific hook for this LU, a list of node names on which the hook
    should run before the execution, and a list of node names on which
    the hook should run after the execution.

    The keys of the dict must not have 'GANETI_' prefixed as this will
    be handled in the hooks runner. Also note additional keys will be
    added by the hooks runner. If the LU doesn't define any
    environment, an empty dict (and not None) should be returned.

    No nodes should be returned as an empty list (and not None).

    Note that if the HPATH for a LU class is None, this function will
    not be called.

    """
    raise NotImplementedError

  def HooksCallBack(self, phase, hook_results, feedback_fn, lu_result):
    """Notify the LU about the results of its hooks.

    This method is called every time a hooks phase is executed, and notifies
    the Logical Unit about the hooks' result. The LU can then use it to alter
    its result based on the hooks.  By default the method does nothing and the
    previous result is passed back unchanged but any LU can define it if it
    wants to use the local cluster hook-scripts somehow.

    @param phase: one of L{constants.HOOKS_PHASE_POST} or
        L{constants.HOOKS_PHASE_PRE}; it denotes the hooks phase
    @param hook_results: the results of the multi-node hooks rpc call
    @param feedback_fn: function used send feedback back to the caller
    @param lu_result: the previous Exec result this LU had, or None
        in the PRE phase
    @return: the new Exec result, based on the previous result
        and hook results

    """
    # API must be kept, thus we ignore the unused argument and could
    # be a function warnings
    # pylint: disable-msg=W0613,R0201
    return lu_result

  def _ExpandAndLockInstance(self):
    """Helper function to expand and lock an instance.

    Many LUs that work on an instance take its name in self.op.instance_name
    and need to expand it and then declare the expanded name for locking. This
    function does it, and then updates self.op.instance_name to the expanded
    name. It also initializes needed_locks as a dict, if this hasn't been done
    before.

    """
    if self.needed_locks is None:
      self.needed_locks = {}
    else:
      assert locking.LEVEL_INSTANCE not in self.needed_locks, \
        "_ExpandAndLockInstance called with instance-level locks set"
    self.op.instance_name = _ExpandInstanceName(self.cfg,
                                                self.op.instance_name)
    self.needed_locks[locking.LEVEL_INSTANCE] = self.op.instance_name

  def _LockInstancesNodes(self, primary_only=False):
    """Helper function to declare instances' nodes for locking.

    This function should be called after locking one or more instances to lock
    their nodes. Its effect is populating self.needed_locks[locking.LEVEL_NODE]
    with all primary or secondary nodes for instances already locked and
    present in self.needed_locks[locking.LEVEL_INSTANCE].

    It should be called from DeclareLocks, and for safety only works if
    self.recalculate_locks[locking.LEVEL_NODE] is set.

    In the future it may grow parameters to just lock some instance's nodes, or
    to just lock primaries or secondary nodes, if needed.

    If should be called in DeclareLocks in a way similar to::

      if level == locking.LEVEL_NODE:
        self._LockInstancesNodes()

    @type primary_only: boolean
    @param primary_only: only lock primary nodes of locked instances

    """
    assert locking.LEVEL_NODE in self.recalculate_locks, \
      "_LockInstancesNodes helper function called with no nodes to recalculate"

    # TODO: check if we're really been called with the instance locks held

    # For now we'll replace self.needed_locks[locking.LEVEL_NODE], but in the
    # future we might want to have different behaviors depending on the value
    # of self.recalculate_locks[locking.LEVEL_NODE]
    wanted_nodes = []
    for instance_name in self.acquired_locks[locking.LEVEL_INSTANCE]:
      instance = self.context.cfg.GetInstanceInfo(instance_name)
      wanted_nodes.append(instance.primary_node)
      if not primary_only:
        wanted_nodes.extend(instance.secondary_nodes)

    if self.recalculate_locks[locking.LEVEL_NODE] == constants.LOCKS_REPLACE:
      self.needed_locks[locking.LEVEL_NODE] = wanted_nodes
    elif self.recalculate_locks[locking.LEVEL_NODE] == constants.LOCKS_APPEND:
      self.needed_locks[locking.LEVEL_NODE].extend(wanted_nodes)

    del self.recalculate_locks[locking.LEVEL_NODE]


class NoHooksLU(LogicalUnit): # pylint: disable-msg=W0223
  """Simple LU which runs no hooks.

  This LU is intended as a parent for other LogicalUnits which will
  run no hooks, in order to reduce duplicate code.

  """
  HPATH = None
  HTYPE = None

  def BuildHooksEnv(self):
    """Empty BuildHooksEnv for NoHooksLu.

    This just raises an error.

    """
    assert False, "BuildHooksEnv called for NoHooksLUs"


class Tasklet:
  """Tasklet base class.

  Tasklets are subcomponents for LUs. LUs can consist entirely of tasklets or
  they can mix legacy code with tasklets. Locking needs to be done in the LU,
  tasklets know nothing about locks.

  Subclasses must follow these rules:
    - Implement CheckPrereq
    - Implement Exec

  """
  def __init__(self, lu):
    self.lu = lu

    # Shortcuts
    self.cfg = lu.cfg
    self.rpc = lu.rpc

  def CheckPrereq(self):
    """Check prerequisites for this tasklets.

    This method should check whether the prerequisites for the execution of
    this tasklet are fulfilled. It can do internode communication, but it
    should be idempotent - no cluster or system changes are allowed.

    The method should raise errors.OpPrereqError in case something is not
    fulfilled. Its return value is ignored.

    This method should also update all parameters to their canonical form if it
    hasn't been done before.

    """
    pass

  def Exec(self, feedback_fn):
    """Execute the tasklet.

    This method should implement the actual work. It should raise
    errors.OpExecError for failures that are somewhat dealt with in code, or
    expected.

    """
    raise NotImplementedError


def _GetWantedNodes(lu, nodes):
  """Returns list of checked and expanded node names.

  @type lu: L{LogicalUnit}
  @param lu: the logical unit on whose behalf we execute
  @type nodes: list
  @param nodes: list of node names or None for all nodes
  @rtype: list
  @return: the list of nodes, sorted
  @raise errors.ProgrammerError: if the nodes parameter is wrong type

  """
  if not nodes:
    raise errors.ProgrammerError("_GetWantedNodes should only be called with a"
      " non-empty list of nodes whose name is to be expanded.")

  wanted = [_ExpandNodeName(lu.cfg, name) for name in nodes]
  return utils.NiceSort(wanted)


def _GetWantedInstances(lu, instances):
  """Returns list of checked and expanded instance names.

  @type lu: L{LogicalUnit}
  @param lu: the logical unit on whose behalf we execute
  @type instances: list
  @param instances: list of instance names or None for all instances
  @rtype: list
  @return: the list of instances, sorted
  @raise errors.OpPrereqError: if the instances parameter is wrong type
  @raise errors.OpPrereqError: if any of the passed instances is not found

  """
  if instances:
    wanted = [_ExpandInstanceName(lu.cfg, name) for name in instances]
  else:
    wanted = utils.NiceSort(lu.cfg.GetInstanceList())
  return wanted


def _GetUpdatedParams(old_params, update_dict,
                      use_default=True, use_none=False):
  """Return the new version of a parameter dictionary.

  @type old_params: dict
  @param old_params: old parameters
  @type update_dict: dict
  @param update_dict: dict containing new parameter values, or
      constants.VALUE_DEFAULT to reset the parameter to its default
      value
  @param use_default: boolean
  @type use_default: whether to recognise L{constants.VALUE_DEFAULT}
      values as 'to be deleted' values
  @param use_none: boolean
  @type use_none: whether to recognise C{None} values as 'to be
      deleted' values
  @rtype: dict
  @return: the new parameter dictionary

  """
  params_copy = copy.deepcopy(old_params)
  for key, val in update_dict.iteritems():
    if ((use_default and val == constants.VALUE_DEFAULT) or
        (use_none and val is None)):
      try:
        del params_copy[key]
      except KeyError:
        pass
    else:
      params_copy[key] = val
  return params_copy


def _CheckOutputFields(static, dynamic, selected):
  """Checks whether all selected fields are valid.

  @type static: L{utils.FieldSet}
  @param static: static fields set
  @type dynamic: L{utils.FieldSet}
  @param dynamic: dynamic fields set

  """
  f = utils.FieldSet()
  f.Extend(static)
  f.Extend(dynamic)

  delta = f.NonMatching(selected)
  if delta:
    raise errors.OpPrereqError("Unknown output fields selected: %s"
                               % ",".join(delta), errors.ECODE_INVAL)


def _CheckBooleanOpField(op, name):
  """Validates boolean opcode parameters.

  This will ensure that an opcode parameter is either a boolean value,
  or None (but that it always exists).

  """
  val = getattr(op, name, None)
  if not (val is None or isinstance(val, bool)):
    raise errors.OpPrereqError("Invalid boolean parameter '%s' (%s)" %
                               (name, str(val)), errors.ECODE_INVAL)
  setattr(op, name, val)


def _CheckGlobalHvParams(params):
  """Validates that given hypervisor params are not global ones.

  This will ensure that instances don't get customised versions of
  global params.

  """
  used_globals = constants.HVC_GLOBALS.intersection(params)
  if used_globals:
    msg = ("The following hypervisor parameters are global and cannot"
           " be customized at instance level, please modify them at"
           " cluster level: %s" % utils.CommaJoin(used_globals))
    raise errors.OpPrereqError(msg, errors.ECODE_INVAL)


def _CheckNodeOnline(lu, node):
  """Ensure that a given node is online.

  @param lu: the LU on behalf of which we make the check
  @param node: the node to check
  @raise errors.OpPrereqError: if the node is offline

  """
  if lu.cfg.GetNodeInfo(node).offline:
    raise errors.OpPrereqError("Can't use offline node %s" % node,
                               errors.ECODE_INVAL)


def _CheckNodeNotDrained(lu, node):
  """Ensure that a given node is not drained.

  @param lu: the LU on behalf of which we make the check
  @param node: the node to check
  @raise errors.OpPrereqError: if the node is drained

  """
  if lu.cfg.GetNodeInfo(node).drained:
    raise errors.OpPrereqError("Can't use drained node %s" % node,
                               errors.ECODE_INVAL)


def _CheckNodeHasOS(lu, node, os_name, force_variant):
  """Ensure that a node supports a given OS.

  @param lu: the LU on behalf of which we make the check
  @param node: the node to check
  @param os_name: the OS to query about
  @param force_variant: whether to ignore variant errors
  @raise errors.OpPrereqError: if the node is not supporting the OS

  """
  result = lu.rpc.call_os_get(node, os_name)
  result.Raise("OS '%s' not in supported OS list for node %s" %
               (os_name, node),
               prereq=True, ecode=errors.ECODE_INVAL)
  if not force_variant:
    _CheckOSVariant(result.payload, os_name)


def _RequireFileStorage():
  """Checks that file storage is enabled.

  @raise errors.OpPrereqError: when file storage is disabled

  """
  if not constants.ENABLE_FILE_STORAGE:
    raise errors.OpPrereqError("File storage disabled at configure time",
                               errors.ECODE_INVAL)


def _CheckDiskTemplate(template):
  """Ensure a given disk template is valid.

  """
  if template not in constants.DISK_TEMPLATES:
    msg = ("Invalid disk template name '%s', valid templates are: %s" %
           (template, utils.CommaJoin(constants.DISK_TEMPLATES)))
    raise errors.OpPrereqError(msg, errors.ECODE_INVAL)
  if template == constants.DT_FILE:
    _RequireFileStorage()


def _CheckStorageType(storage_type):
  """Ensure a given storage type is valid.

  """
  if storage_type not in constants.VALID_STORAGE_TYPES:
    raise errors.OpPrereqError("Unknown storage type: %s" % storage_type,
                               errors.ECODE_INVAL)
  if storage_type == constants.ST_FILE:
    _RequireFileStorage()
  return True


def _GetClusterDomainSecret():
  """Reads the cluster domain secret.

  """
  return utils.ReadOneLineFile(constants.CLUSTER_DOMAIN_SECRET_FILE,
                               strict=True)


def _CheckInstanceDown(lu, instance, reason):
  """Ensure that an instance is not running."""
  if instance.admin_up:
    raise errors.OpPrereqError("Instance %s is marked to be up, %s" %
                               (instance.name, reason), errors.ECODE_STATE)

  pnode = instance.primary_node
  ins_l = lu.rpc.call_instance_list([pnode], [instance.hypervisor])[pnode]
  ins_l.Raise("Can't contact node %s for instance information" % pnode,
              prereq=True, ecode=errors.ECODE_ENVIRON)

  if instance.name in ins_l.payload:
    raise errors.OpPrereqError("Instance %s is running, %s" %
                               (instance.name, reason), errors.ECODE_STATE)


def _ExpandItemName(fn, name, kind):
  """Expand an item name.

  @param fn: the function to use for expansion
  @param name: requested item name
  @param kind: text description ('Node' or 'Instance')
  @return: the resolved (full) name
  @raise errors.OpPrereqError: if the item is not found

  """
  full_name = fn(name)
  if full_name is None:
    raise errors.OpPrereqError("%s '%s' not known" % (kind, name),
                               errors.ECODE_NOENT)
  return full_name


def _ExpandNodeName(cfg, name):
  """Wrapper over L{_ExpandItemName} for nodes."""
  return _ExpandItemName(cfg.ExpandNodeName, name, "Node")


def _ExpandInstanceName(cfg, name):
  """Wrapper over L{_ExpandItemName} for instance."""
  return _ExpandItemName(cfg.ExpandInstanceName, name, "Instance")


def _BuildInstanceHookEnv(name, primary_node, secondary_nodes, os_type, status,
                          memory, vcpus, nics, disk_template, disks,
                          bep, hvp, hypervisor_name):
  """Builds instance related env variables for hooks

  This builds the hook environment from individual variables.

  @type name: string
  @param name: the name of the instance
  @type primary_node: string
  @param primary_node: the name of the instance's primary node
  @type secondary_nodes: list
  @param secondary_nodes: list of secondary nodes as strings
  @type os_type: string
  @param os_type: the name of the instance's OS
  @type status: boolean
  @param status: the should_run status of the instance
  @type memory: string
  @param memory: the memory size of the instance
  @type vcpus: string
  @param vcpus: the count of VCPUs the instance has
  @type nics: list
  @param nics: list of tuples (ip, mac, mode, link) representing
      the NICs the instance has
  @type disk_template: string
  @param disk_template: the disk template of the instance
  @type disks: list
  @param disks: the list of (size, mode) pairs
  @type bep: dict
  @param bep: the backend parameters for the instance
  @type hvp: dict
  @param hvp: the hypervisor parameters for the instance
  @type hypervisor_name: string
  @param hypervisor_name: the hypervisor for the instance
  @rtype: dict
  @return: the hook environment for this instance

  """
  if status:
    str_status = "up"
  else:
    str_status = "down"
  env = {
    "OP_TARGET": name,
    "INSTANCE_NAME": name,
    "INSTANCE_PRIMARY": primary_node,
    "INSTANCE_SECONDARIES": " ".join(secondary_nodes),
    "INSTANCE_OS_TYPE": os_type,
    "INSTANCE_STATUS": str_status,
    "INSTANCE_MEMORY": memory,
    "INSTANCE_VCPUS": vcpus,
    "INSTANCE_DISK_TEMPLATE": disk_template,
    "INSTANCE_HYPERVISOR": hypervisor_name,
  }

  if nics:
    nic_count = len(nics)
    for idx, (ip, mac, mode, link) in enumerate(nics):
      if ip is None:
        ip = ""
      env["INSTANCE_NIC%d_IP" % idx] = ip
      env["INSTANCE_NIC%d_MAC" % idx] = mac
      env["INSTANCE_NIC%d_MODE" % idx] = mode
      env["INSTANCE_NIC%d_LINK" % idx] = link
      if mode == constants.NIC_MODE_BRIDGED:
        env["INSTANCE_NIC%d_BRIDGE" % idx] = link
  else:
    nic_count = 0

  env["INSTANCE_NIC_COUNT"] = nic_count

  if disks:
    disk_count = len(disks)
    for idx, (size, mode) in enumerate(disks):
      env["INSTANCE_DISK%d_SIZE" % idx] = size
      env["INSTANCE_DISK%d_MODE" % idx] = mode
  else:
    disk_count = 0

  env["INSTANCE_DISK_COUNT"] = disk_count

  for source, kind in [(bep, "BE"), (hvp, "HV")]:
    for key, value in source.items():
      env["INSTANCE_%s_%s" % (kind, key)] = value

  return env


def _NICListToTuple(lu, nics):
  """Build a list of nic information tuples.

  This list is suitable to be passed to _BuildInstanceHookEnv or as a return
  value in LUQueryInstanceData.

  @type lu:  L{LogicalUnit}
  @param lu: the logical unit on whose behalf we execute
  @type nics: list of L{objects.NIC}
  @param nics: list of nics to convert to hooks tuples

  """
  hooks_nics = []
  cluster = lu.cfg.GetClusterInfo()
  for nic in nics:
    ip = nic.ip
    mac = nic.mac
    filled_params = cluster.SimpleFillNIC(nic.nicparams)
    mode = filled_params[constants.NIC_MODE]
    link = filled_params[constants.NIC_LINK]
    hooks_nics.append((ip, mac, mode, link))
  return hooks_nics


def _BuildInstanceHookEnvByObject(lu, instance, override=None):
  """Builds instance related env variables for hooks from an object.

  @type lu: L{LogicalUnit}
  @param lu: the logical unit on whose behalf we execute
  @type instance: L{objects.Instance}
  @param instance: the instance for which we should build the
      environment
  @type override: dict
  @param override: dictionary with key/values that will override
      our values
  @rtype: dict
  @return: the hook environment dictionary

  """
  cluster = lu.cfg.GetClusterInfo()
  bep = cluster.FillBE(instance)
  hvp = cluster.FillHV(instance)
  args = {
    'name': instance.name,
    'primary_node': instance.primary_node,
    'secondary_nodes': instance.secondary_nodes,
    'os_type': instance.os,
    'status': instance.admin_up,
    'memory': bep[constants.BE_MEMORY],
    'vcpus': bep[constants.BE_VCPUS],
    'nics': _NICListToTuple(lu, instance.nics),
    'disk_template': instance.disk_template,
    'disks': [(disk.size, disk.mode) for disk in instance.disks],
    'bep': bep,
    'hvp': hvp,
    'hypervisor_name': instance.hypervisor,
  }
  if override:
    args.update(override)
  return _BuildInstanceHookEnv(**args) # pylint: disable-msg=W0142


def _AdjustCandidatePool(lu, exceptions):
  """Adjust the candidate pool after node operations.

  """
  mod_list = lu.cfg.MaintainCandidatePool(exceptions)
  if mod_list:
    lu.LogInfo("Promoted nodes to master candidate role: %s",
               utils.CommaJoin(node.name for node in mod_list))
    for name in mod_list:
      lu.context.ReaddNode(name)
  mc_now, mc_max, _ = lu.cfg.GetMasterCandidateStats(exceptions)
  if mc_now > mc_max:
    lu.LogInfo("Note: more nodes are candidates (%d) than desired (%d)" %
               (mc_now, mc_max))


def _DecideSelfPromotion(lu, exceptions=None):
  """Decide whether I should promote myself as a master candidate.

  """
  cp_size = lu.cfg.GetClusterInfo().candidate_pool_size
  mc_now, mc_should, _ = lu.cfg.GetMasterCandidateStats(exceptions)
  # the new node will increase mc_max with one, so:
  mc_should = min(mc_should + 1, cp_size)
  return mc_now < mc_should


def _CheckNicsBridgesExist(lu, target_nics, target_node):
  """Check that the brigdes needed by a list of nics exist.

  """
  cluster = lu.cfg.GetClusterInfo()
  paramslist = [cluster.SimpleFillNIC(nic.nicparams) for nic in target_nics]
  brlist = [params[constants.NIC_LINK] for params in paramslist
            if params[constants.NIC_MODE] == constants.NIC_MODE_BRIDGED]
  if brlist:
    result = lu.rpc.call_bridges_exist(target_node, brlist)
    result.Raise("Error checking bridges on destination node '%s'" %
                 target_node, prereq=True, ecode=errors.ECODE_ENVIRON)


def _CheckInstanceBridgesExist(lu, instance, node=None):
  """Check that the brigdes needed by an instance exist.

  """
  if node is None:
    node = instance.primary_node
  _CheckNicsBridgesExist(lu, instance.nics, node)


def _CheckOSVariant(os_obj, name):
  """Check whether an OS name conforms to the os variants specification.

  @type os_obj: L{objects.OS}
  @param os_obj: OS object to check
  @type name: string
  @param name: OS name passed by the user, to check for validity

  """
  if not os_obj.supported_variants:
    return
  try:
    variant = name.split("+", 1)[1]
  except IndexError:
    raise errors.OpPrereqError("OS name must include a variant",
                               errors.ECODE_INVAL)

  if variant not in os_obj.supported_variants:
    raise errors.OpPrereqError("Unsupported OS variant", errors.ECODE_INVAL)


def _GetNodeInstancesInner(cfg, fn):
  return [i for i in cfg.GetAllInstancesInfo().values() if fn(i)]


def _GetNodeInstances(cfg, node_name):
  """Returns a list of all primary and secondary instances on a node.

  """

  return _GetNodeInstancesInner(cfg, lambda inst: node_name in inst.all_nodes)


def _GetNodePrimaryInstances(cfg, node_name):
  """Returns primary instances on a node.

  """
  return _GetNodeInstancesInner(cfg,
                                lambda inst: node_name == inst.primary_node)


def _GetNodeSecondaryInstances(cfg, node_name):
  """Returns secondary instances on a node.

  """
  return _GetNodeInstancesInner(cfg,
                                lambda inst: node_name in inst.secondary_nodes)


def _GetStorageTypeArgs(cfg, storage_type):
  """Returns the arguments for a storage type.

  """
  # Special case for file storage
  if storage_type == constants.ST_FILE:
    # storage.FileStorage wants a list of storage directories
    return [[cfg.GetFileStorageDir()]]

  return []


def _FindFaultyInstanceDisks(cfg, rpc, instance, node_name, prereq):
  faulty = []

  for dev in instance.disks:
    cfg.SetDiskID(dev, node_name)

  result = rpc.call_blockdev_getmirrorstatus(node_name, instance.disks)
  result.Raise("Failed to get disk status from node %s" % node_name,
               prereq=prereq, ecode=errors.ECODE_ENVIRON)

  for idx, bdev_status in enumerate(result.payload):
    if bdev_status and bdev_status.ldisk_status == constants.LDS_FAULTY:
      faulty.append(idx)

  return faulty


class LUPostInitCluster(LogicalUnit):
  """Logical unit for running hooks after cluster initialization.

  """
  HPATH = "cluster-init"
  HTYPE = constants.HTYPE_CLUSTER
  _OP_REQP = []

  def BuildHooksEnv(self):
    """Build hooks env.

    """
    env = {"OP_TARGET": self.cfg.GetClusterName()}
    mn = self.cfg.GetMasterNode()
    return env, [], [mn]

  def Exec(self, feedback_fn):
    """Nothing to do.

    """
    return True


class LUDestroyCluster(LogicalUnit):
  """Logical unit for destroying the cluster.

  """
  HPATH = "cluster-destroy"
  HTYPE = constants.HTYPE_CLUSTER
  _OP_REQP = []

  def BuildHooksEnv(self):
    """Build hooks env.

    """
    env = {"OP_TARGET": self.cfg.GetClusterName()}
    return env, [], []

  def CheckPrereq(self):
    """Check prerequisites.

    This checks whether the cluster is empty.

    Any errors are signaled by raising errors.OpPrereqError.

    """
    master = self.cfg.GetMasterNode()

    nodelist = self.cfg.GetNodeList()
    if len(nodelist) != 1 or nodelist[0] != master:
      raise errors.OpPrereqError("There are still %d node(s) in"
                                 " this cluster." % (len(nodelist) - 1),
                                 errors.ECODE_INVAL)