Synnefo » snf-ganeti

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#

# Copyright (C) 2012, 2013 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 implementing the iallocator code."""

from ganeti import compat

from ganeti import constants

from ganeti import errors

from ganeti import ht

from ganeti import outils

from ganeti import opcodes

from ganeti import rpc

from ganeti import serializer

from ganeti import utils

import ganeti.masterd.instance as gmi

_STRING_LIST = ht.TListOf(ht.TString)

_JOB_LIST = ht.TListOf(ht.TListOf(ht.TStrictDict(True, False, {

   # pylint: disable=E1101

   # Class '...' has no 'OP_ID' member

   "OP_ID": ht.TElemOf([opcodes.OpInstanceFailover.OP_ID,

                        opcodes.OpInstanceMigrate.OP_ID,

                        opcodes.OpInstanceReplaceDisks.OP_ID]),

   })))

_NEVAC_MOVED = \

  ht.TListOf(ht.TAnd(ht.TIsLength(3),

                     ht.TItems([ht.TNonEmptyString,

                                ht.TNonEmptyString,

                                ht.TListOf(ht.TNonEmptyString),

                                ])))

_NEVAC_FAILED = \

  ht.TListOf(ht.TAnd(ht.TIsLength(2),

                     ht.TItems([ht.TNonEmptyString,

                                ht.TMaybeString,

                                ])))

_NEVAC_RESULT = ht.TAnd(ht.TIsLength(3),

                        ht.TItems([_NEVAC_MOVED, _NEVAC_FAILED, _JOB_LIST]))

_INST_NAME = ("name", ht.TNonEmptyString)

_INST_UUID = ("inst_uuid", ht.TNonEmptyString)

class _AutoReqParam(outils.AutoSlots):

  """Meta class for request definitions.

  """

  @classmethod

  def _GetSlots(mcs, attrs):

    """Extract the slots out of REQ_PARAMS.

    """

    params = attrs.setdefault("REQ_PARAMS", [])

    return [slot for (slot, _) in params]

class IARequestBase(outils.ValidatedSlots):

  """A generic IAllocator request object.

  """

  __metaclass__ = _AutoReqParam

  MODE = NotImplemented

  REQ_PARAMS = []

  REQ_RESULT = NotImplemented

  def __init__(self, **kwargs):

    """Constructor for IARequestBase.

    The constructor takes only keyword arguments and will set

    attributes on this object based on the passed arguments. As such,

    it means that you should not pass arguments which are not in the

    REQ_PARAMS attribute for this class.

    """

    outils.ValidatedSlots.__init__(self, **kwargs)

    self.Validate()

  def Validate(self):

    """Validates all parameters of the request.

    """

    assert self.MODE in constants.VALID_IALLOCATOR_MODES

    for (param, validator) in self.REQ_PARAMS:

      if not hasattr(self, param):

        raise errors.OpPrereqError("Request is missing '%s' parameter" % param,

                                   errors.ECODE_INVAL)

      value = getattr(self, param)

      if not validator(value):

        raise errors.OpPrereqError(("Request parameter '%s' has invalid"

                                    " type %s/value %s") %

                                    (param, type(value), value),

                                    errors.ECODE_INVAL)

  def GetRequest(self, cfg):

    """Gets the request data dict.

    @param cfg: The configuration instance

    """

    raise NotImplementedError

  def ValidateResult(self, ia, result):

    """Validates the result of an request.

    @param ia: The IAllocator instance

    @param result: The IAllocator run result

    @raises ResultValidationError: If validation fails

    """

    if ia.success and not self.REQ_RESULT(result):

      raise errors.ResultValidationError("iallocator returned invalid result,"

                                         " expected %s, got %s" %

                                         (self.REQ_RESULT, result))

class IAReqInstanceAlloc(IARequestBase):

  """An instance allocation request.

  """

  # pylint: disable=E1101

  MODE = constants.IALLOCATOR_MODE_ALLOC

  REQ_PARAMS = [

    _INST_NAME,

    ("memory", ht.TNonNegativeInt),

    ("spindle_use", ht.TNonNegativeInt),

    ("disks", ht.TListOf(ht.TDict)),

    ("disk_template", ht.TString),

    ("os", ht.TString),

    ("tags", _STRING_LIST),

    ("nics", ht.TListOf(ht.TDict)),

    ("vcpus", ht.TInt),

    ("hypervisor", ht.TString),

    ("node_whitelist", ht.TMaybeListOf(ht.TNonEmptyString)),

    ]

  REQ_RESULT = ht.TList

  def RequiredNodes(self):

    """Calculates the required nodes based on the disk_template.

    """

    if self.disk_template in constants.DTS_INT_MIRROR:

      return 2

    else:

      return 1

  def GetRequest(self, cfg):

    """Requests a new instance.

    The checks for the completeness of the opcode must have already been

    done.

    """

    disk_space = gmi.ComputeDiskSize(self.disk_template, self.disks)

    return {

      "name": self.name,

      "disk_template": self.disk_template,

      "tags": self.tags,

      "os": self.os,

      "vcpus": self.vcpus,

      "memory": self.memory,

      "spindle_use": self.spindle_use,

      "disks": self.disks,

      "disk_space_total": disk_space,

      "nics": self.nics,

      "required_nodes": self.RequiredNodes(),

      "hypervisor": self.hypervisor,

      }

  def ValidateResult(self, ia, result):

    """Validates an single instance allocation request.

    """

    IARequestBase.ValidateResult(self, ia, result)

    if ia.success and len(result) != self.RequiredNodes():

      raise errors.ResultValidationError("iallocator returned invalid number"

                                         " of nodes (%s), required %s" %

                                         (len(result), self.RequiredNodes()))

class IAReqMultiInstanceAlloc(IARequestBase):

  """An multi instance allocation request.

  """

  # pylint: disable=E1101

  MODE = constants.IALLOCATOR_MODE_MULTI_ALLOC

  REQ_PARAMS = [

    ("instances", ht.TListOf(ht.TInstanceOf(IAReqInstanceAlloc))),

    ]

  _MASUCCESS = \

    ht.TListOf(ht.TAnd(ht.TIsLength(2),

                       ht.TItems([ht.TNonEmptyString,

                                  ht.TListOf(ht.TNonEmptyString),

                                  ])))

  _MAFAILED = ht.TListOf(ht.TNonEmptyString)

  REQ_RESULT = ht.TAnd(ht.TList, ht.TIsLength(2),

                       ht.TItems([_MASUCCESS, _MAFAILED]))

  def GetRequest(self, cfg):

    return {

      "instances": [iareq.GetRequest(cfg) for iareq in self.instances],

      }

class IAReqRelocate(IARequestBase):

  """A relocation request.

  """

  # pylint: disable=E1101

  MODE = constants.IALLOCATOR_MODE_RELOC

  REQ_PARAMS = [

    _INST_UUID,

    ("relocate_from_node_uuids", _STRING_LIST),

    ]

  REQ_RESULT = ht.TList

  def GetRequest(self, cfg):

    """Request an relocation of an instance

    The checks for the completeness of the opcode must have already been

    done.

    """

    instance = cfg.GetInstanceInfo(self.inst_uuid)

    if instance is None:

      raise errors.ProgrammerError("Unknown instance '%s' passed to"

                                   " IAllocator" % self.inst_uuid)

    if instance.disk_template not in constants.DTS_MIRRORED:

      raise errors.OpPrereqError("Can't relocate non-mirrored instances",

                                 errors.ECODE_INVAL)

    if (instance.disk_template in constants.DTS_INT_MIRROR and

        len(instance.secondary_nodes) != 1):

      raise errors.OpPrereqError("Instance has not exactly one secondary node",

                                 errors.ECODE_STATE)

    disk_sizes = [{constants.IDISK_SIZE: disk.size} for disk in instance.disks]

    disk_space = gmi.ComputeDiskSize(instance.disk_template, disk_sizes)

    return {

      "name": instance.name,

      "disk_space_total": disk_space,

      "required_nodes": 1,

      "relocate_from": cfg.GetNodeNames(self.relocate_from_node_uuids),

      }

  def ValidateResult(self, ia, result):

    """Validates the result of an relocation request.

    """

    IARequestBase.ValidateResult(self, ia, result)

    node2group = dict((name, ndata["group"])

                      for (name, ndata) in ia.in_data["nodes"].items())

    fn = compat.partial(self._NodesToGroups, node2group,

                        ia.in_data["nodegroups"])

    instance = ia.cfg.GetInstanceInfo(self.inst_uuid)

    request_groups = fn(ia.cfg.GetNodeNames(self.relocate_from_node_uuids) +

                        ia.cfg.GetNodeNames([instance.primary_node]))

    result_groups = fn(result + ia.cfg.GetNodeNames([instance.primary_node]))

    if ia.success and not set(result_groups).issubset(request_groups):

      raise errors.ResultValidationError("Groups of nodes returned by"

                                         " iallocator (%s) differ from original"

                                         " groups (%s)" %

                                         (utils.CommaJoin(result_groups),

                                          utils.CommaJoin(request_groups)))

  @staticmethod

  def _NodesToGroups(node2group, groups, nodes):

    """Returns a list of unique group names for a list of nodes.

    @type node2group: dict

    @param node2group: Map from node name to group UUID

    @type groups: dict

    @param groups: Group information

    @type nodes: list

    @param nodes: Node names

    """

    result = set()

    for node in nodes:

      try:

        group_uuid = node2group[node]

      except KeyError:

        # Ignore unknown node

        pass

      else:

        try:

          group = groups[group_uuid]

        except KeyError:

          # Can't find group, let's use UUID

          group_name = group_uuid

        else:

          group_name = group["name"]

        result.add(group_name)

    return sorted(result)

class IAReqNodeEvac(IARequestBase):

  """A node evacuation request.

  """

  # pylint: disable=E1101

  MODE = constants.IALLOCATOR_MODE_NODE_EVAC

  REQ_PARAMS = [

    ("instances", _STRING_LIST),

    ("evac_mode", ht.TElemOf(constants.IALLOCATOR_NEVAC_MODES)),

    ]

  REQ_RESULT = _NEVAC_RESULT

  def GetRequest(self, cfg):

    """Get data for node-evacuate requests.

    """

    return {

      "instances": self.instances,

      "evac_mode": self.evac_mode,

      }

class IAReqGroupChange(IARequestBase):

  """A group change request.

  """

  # pylint: disable=E1101

  MODE = constants.IALLOCATOR_MODE_CHG_GROUP

  REQ_PARAMS = [

    ("instances", _STRING_LIST),

    ("target_groups", _STRING_LIST),

    ]

  REQ_RESULT = _NEVAC_RESULT

  def GetRequest(self, cfg):

    """Get data for node-evacuate requests.

    """

    return {

      "instances": self.instances,

      "target_groups": self.target_groups,

      }

class IAllocator(object):

  """IAllocator framework.

  An IAllocator instance has three sets of attributes:

    - cfg that is needed to query the cluster

    - input data (all members of the _KEYS class attribute are required)

    - four buffer attributes (in|out_data|text), that represent the

      input (to the external script) in text and data structure format,

      and the output from it, again in two formats

    - the result variables from the script (success, info, nodes) for

      easy usage

  """

  # pylint: disable=R0902

  # lots of instance attributes

  def __init__(self, cfg, rpc_runner, req):

    self.cfg = cfg

    self.rpc = rpc_runner

    self.req = req

    # init buffer variables

    self.in_text = self.out_text = self.in_data = self.out_data = None

    # init result fields

    self.success = self.info = self.result = None

    self._BuildInputData(req)

  def _ComputerClusterDataNodeInfo(self, node_list, cluster_info,

                                   hypervisor_name):

    """Prepare and execute node info call.

    @type node_list: list of strings

    @param node_list: list of nodes' UUIDs

    @type cluster_info: L{objects.Cluster}

    @param cluster_info: the cluster's information from the config

    @type hypervisor_name: string

    @param hypervisor_name: the hypervisor name

    @rtype: same as the result of the node info RPC call

    @return: the result of the node info RPC call

    """

    es_flags = rpc.GetExclusiveStorageForNodes(self.cfg, node_list)

    storage_units = utils.storage.GetStorageUnitsOfCluster(

        self.cfg, include_spindles=True)

    hvspecs = [(hypervisor_name, cluster_info.hvparams[hypervisor_name])]

    return self.rpc.call_node_info(node_list, storage_units, hvspecs, es_flags)

  def _ComputeClusterData(self):

    """Compute the generic allocator input data.

    This is the data that is independent of the actual operation.

    """

    cluster_info = self.cfg.GetClusterInfo()

    # cluster data

    data = {

      "version": constants.IALLOCATOR_VERSION,

      "cluster_name": self.cfg.GetClusterName(),

      "cluster_tags": list(cluster_info.GetTags()),

      "enabled_hypervisors": list(cluster_info.enabled_hypervisors),

      "ipolicy": cluster_info.ipolicy,

      }

    ninfo = self.cfg.GetAllNodesInfo()

    iinfo = self.cfg.GetAllInstancesInfo().values()

    i_list = [(inst, cluster_info.FillBE(inst)) for inst in iinfo]

    # node data

    node_list = [n.uuid for n in ninfo.values() if n.vm_capable]

    if isinstance(self.req, IAReqInstanceAlloc):

      hypervisor_name = self.req.hypervisor

      node_whitelist = self.req.node_whitelist

    elif isinstance(self.req, IAReqRelocate):

      hypervisor_name = self.cfg.GetInstanceInfo(self.req.inst_uuid).hypervisor

      node_whitelist = None

    else:

      hypervisor_name = cluster_info.primary_hypervisor

      node_whitelist = None

    has_lvm = utils.storage.IsLvmEnabled(cluster_info.enabled_disk_templates)

    node_data = self._ComputerClusterDataNodeInfo(node_list, cluster_info,

                                                  hypervisor_name)

    node_iinfo = \

      self.rpc.call_all_instances_info(node_list,

                                       cluster_info.enabled_hypervisors,

                                       cluster_info.hvparams)

    data["nodegroups"] = self._ComputeNodeGroupData(self.cfg)

    config_ndata = self._ComputeBasicNodeData(self.cfg, ninfo, node_whitelist)

    data["nodes"] = self._ComputeDynamicNodeData(ninfo, node_data, node_iinfo,

                                                 i_list, config_ndata, has_lvm)

    assert len(data["nodes"]) == len(ninfo), \

        "Incomplete node data computed"

    data["instances"] = self._ComputeInstanceData(self.cfg, cluster_info,

                                                  i_list)

    self.in_data = data

  @staticmethod

  def _ComputeNodeGroupData(cfg):

    """Compute node groups data.

    """

    cluster = cfg.GetClusterInfo()

    ng = dict((guuid, {

      "name": gdata.name,

      "alloc_policy": gdata.alloc_policy,

      "networks": [net_uuid for net_uuid, _ in gdata.networks.items()],

      "ipolicy": gmi.CalculateGroupIPolicy(cluster, gdata),

      "tags": list(gdata.GetTags()),

      })

      for guuid, gdata in cfg.GetAllNodeGroupsInfo().items())

    return ng

  @staticmethod

  def _ComputeBasicNodeData(cfg, node_cfg, node_whitelist):

    """Compute global node data.

    @rtype: dict

    @returns: a dict of name: (node dict, node config)

    """

    # fill in static (config-based) values

    node_results = dict((ninfo.name, {

      "tags": list(ninfo.GetTags()),

      "primary_ip": ninfo.primary_ip,

      "secondary_ip": ninfo.secondary_ip,

      "offline": (ninfo.offline or

                  not (node_whitelist is None or

                       ninfo.name in node_whitelist)),

      "drained": ninfo.drained,

      "master_candidate": ninfo.master_candidate,

      "group": ninfo.group,

      "master_capable": ninfo.master_capable,

      "vm_capable": ninfo.vm_capable,

      "ndparams": cfg.GetNdParams(ninfo),

      })

      for ninfo in node_cfg.values())

    return node_results

  @staticmethod

  def _GetAttributeFromHypervisorNodeData(hv_info, node_name, attr):

    """Extract an attribute from the hypervisor's node information.

    This is a helper function to extract data from the hypervisor's information

    about the node, as part of the result of a node_info query.

    @type hv_info: dict of strings

    @param hv_info: dictionary of node information from the hypervisor

    @type node_name: string

    @param node_name: name of the node

    @type attr: string

    @param attr: key of the attribute in the hv_info dictionary

    @rtype: integer

    @return: the value of the attribute

    @raises errors.OpExecError: if key not in dictionary or value not

      integer

    """

    if attr not in hv_info:

      raise errors.OpExecError("Node '%s' didn't return attribute"

                               " '%s'" % (node_name, attr))

    value = hv_info[attr]

    if not isinstance(value, int):

      raise errors.OpExecError("Node '%s' returned invalid value"

                               " for '%s': %s" %

                               (node_name, attr, value))

    return value

  @staticmethod

  def _ComputeStorageDataFromNodeInfo(node_info, node_name, has_lvm):

    """Extract storage data from node info (_not_ legacy node info).

    @type node_info: see result of the RPC call node info

    @param node_info: the result of the RPC call node info

    @type node_name: string

    @param node_name: the node's name

    @type has_lvm: boolean

    @param has_lvm: whether or not LVM storage information is requested

    @rtype: 4-tuple of integers

    @return: tuple of storage info (total_disk, free_disk, total_spindles,

       free_spindles)

    """

    (_, space_info, _) = node_info

    # TODO: replace this with proper storage reporting

    if has_lvm:

      lvm_vg_info = utils.storage.LookupSpaceInfoByStorageType(

         space_info, constants.ST_LVM_VG)

      if not lvm_vg_info:

        raise errors.OpExecError("Node '%s' didn't return LVM vg space info."

                                 % (node_name))

      total_disk = lvm_vg_info["storage_size"]

      free_disk = lvm_vg_info["storage_free"]

      lvm_pv_info = utils.storage.LookupSpaceInfoByStorageType(

         space_info, constants.ST_LVM_PV)

      if not lvm_vg_info:

        raise errors.OpExecError("Node '%s' didn't return LVM pv space info."

                                 % (node_name))

      total_spindles = lvm_pv_info["storage_size"]

      free_spindles = lvm_pv_info["storage_free"]

    else:

      # we didn't even ask the node for VG status, so use zeros

      total_disk = free_disk = 0

      total_spindles = free_spindles = 0

    return (total_disk, free_disk, total_spindles, free_spindles)

  @staticmethod

  def _ComputeInstanceMemory(instance_list, node_instances_info, node_uuid,

                             input_mem_free):

    """Compute memory used by primary instances.

    @rtype: tuple (int, int, int)

    @returns: A tuple of three integers: 1. the sum of memory used by primary

      instances on the node (including the ones that are currently down), 2.

      the sum of memory used by primary instances of the node that are up, 3.

      the amount of memory that is free on the node considering the current

      usage of the instances.

    """

    i_p_mem = i_p_up_mem = 0

    mem_free = input_mem_free

    for iinfo, beinfo in instance_list:

      if iinfo.primary_node == node_uuid:

        i_p_mem += beinfo[constants.BE_MAXMEM]

        if iinfo.name not in node_instances_info[node_uuid].payload:

          i_used_mem = 0

        else:

          i_used_mem = int(node_instances_info[node_uuid]

                           .payload[iinfo.name]["memory"])

        i_mem_diff = beinfo[constants.BE_MAXMEM] - i_used_mem

        mem_free -= max(0, i_mem_diff)

        if iinfo.admin_state == constants.ADMINST_UP:

          i_p_up_mem += beinfo[constants.BE_MAXMEM]

    return (i_p_mem, i_p_up_mem, mem_free)

  def _ComputeDynamicNodeData(self, node_cfg, node_data, node_iinfo, i_list,

                              node_results, has_lvm):

    """Compute global node data.

    @param node_results: the basic node structures as filled from the config

    """

    #TODO(dynmem): compute the right data on MAX and MIN memory

    # make a copy of the current dict

    node_results = dict(node_results)

    for nuuid, nresult in node_data.items():

      ninfo = node_cfg[nuuid]

      assert ninfo.name in node_results, "Missing basic data for node %s" % \

                                         ninfo.name

      if not (ninfo.offline or ninfo.drained):

        nresult.Raise("Can't get data for node %s" % ninfo.name)

        node_iinfo[nuuid].Raise("Can't get node instance info from node %s" %

                                ninfo.name)

        (_, _, (hv_info, )) = nresult.payload

        mem_free = self._GetAttributeFromHypervisorNodeData(hv_info, ninfo.name,

                                                            "memory_free")

        (i_p_mem, i_p_up_mem, mem_free) = self._ComputeInstanceMemory(

             i_list, node_iinfo, nuuid, mem_free)

        (total_disk, free_disk, total_spindles, free_spindles) = \

            self._ComputeStorageDataFromNodeInfo(nresult.payload, ninfo.name,

                                                 has_lvm)

        # compute memory used by instances

        pnr_dyn = {

          "total_memory": self._GetAttributeFromHypervisorNodeData(

              hv_info, ninfo.name, "memory_total"),

          "reserved_memory": self._GetAttributeFromHypervisorNodeData(

              hv_info, ninfo.name, "memory_dom0"),

          "free_memory": mem_free,

          "total_disk": total_disk,

          "free_disk": free_disk,

          "total_spindles": total_spindles,

          "free_spindles": free_spindles,

          "total_cpus": self._GetAttributeFromHypervisorNodeData(

              hv_info, ninfo.name, "cpu_total"),

          "i_pri_memory": i_p_mem,

          "i_pri_up_memory": i_p_up_mem,

          }

        pnr_dyn.update(node_results[ninfo.name])

        node_results[ninfo.name] = pnr_dyn

    return node_results

  @staticmethod

  def _ComputeInstanceData(cfg, cluster_info, i_list):

    """Compute global instance data.

    """

    instance_data = {}

    for iinfo, beinfo in i_list:

      nic_data = []

      for nic in iinfo.nics:

        filled_params = cluster_info.SimpleFillNIC(nic.nicparams)

        nic_dict = {

          "mac": nic.mac,

          "ip": nic.ip,

          "mode": filled_params[constants.NIC_MODE],

          "link": filled_params[constants.NIC_LINK],

          }

        if filled_params[constants.NIC_MODE] == constants.NIC_MODE_BRIDGED:

          nic_dict["bridge"] = filled_params[constants.NIC_LINK]

        nic_data.append(nic_dict)

      pir = {

        "tags": list(iinfo.GetTags()),

        "admin_state": iinfo.admin_state,

        "vcpus": beinfo[constants.BE_VCPUS],

        "memory": beinfo[constants.BE_MAXMEM],

        "spindle_use": beinfo[constants.BE_SPINDLE_USE],

        "os": iinfo.os,

        "nodes": [cfg.GetNodeName(iinfo.primary_node)] +

                 cfg.GetNodeNames(iinfo.secondary_nodes),

        "nics": nic_data,

        "disks": [{constants.IDISK_SIZE: dsk.size,

                   constants.IDISK_MODE: dsk.mode,

                   constants.IDISK_SPINDLES: dsk.spindles}

                  for dsk in iinfo.disks],

        "disk_template": iinfo.disk_template,

        "disks_active": iinfo.disks_active,

        "hypervisor": iinfo.hypervisor,

        }

      pir["disk_space_total"] = gmi.ComputeDiskSize(iinfo.disk_template,

                                                    pir["disks"])

      instance_data[iinfo.name] = pir

    return instance_data

  def _BuildInputData(self, req):

    """Build input data structures.

    """

    self._ComputeClusterData()

    request = req.GetRequest(self.cfg)

    request["type"] = req.MODE

    self.in_data["request"] = request

    self.in_text = serializer.Dump(self.in_data)

  def Run(self, name, validate=True, call_fn=None):

    """Run an instance allocator and return the results.

    """

    if call_fn is None:

      call_fn = self.rpc.call_iallocator_runner

    result = call_fn(self.cfg.GetMasterNode(), name, self.in_text)

    result.Raise("Failure while running the iallocator script")

    self.out_text = result.payload

    if validate:

      self._ValidateResult()

  def _ValidateResult(self):

    """Process the allocator results.

    This will process and if successful save the result in

    self.out_data and the other parameters.

    """

    try:

      rdict = serializer.Load(self.out_text)

    except Exception, err:

      raise errors.OpExecError("Can't parse iallocator results: %s" % str(err))

    if not isinstance(rdict, dict):

      raise errors.OpExecError("Can't parse iallocator results: not a dict")

    # TODO: remove backwards compatiblity in later versions