Synnefo

# -*- coding: utf-8 -*-

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"""Business logic for reconciliation

Reconcile the contents of the DB with the actual state of the

Ganeti backend.

Let D be the set of VMs in the DB, G the set of VMs in Ganeti.

RULES:

    R1. Stale servers in DB:

            For any v in D but not in G:

            Set deleted=True.

    R2. Orphan instances in Ganet:

            For any v in G with deleted=True in D:

            Issue OP_INSTANCE_DESTROY.

    R3. Unsynced operstate:

            For any v whose operating state differs between G and V:

            Set the operating state in D based on the state in G.

In the code, D, G are Python dicts mapping instance ids to operating state.

For D, the operating state is chosen from VirtualMachine.OPER_STATES.

For G, the operating state is True if the machine is up, False otherwise.

"""

from django.conf import settings

import logging

import itertools

import bitarray

from datetime import datetime, timedelta

from django.db import transaction

from synnefo.db.models import (Backend, VirtualMachine, Flavor,

                               pooled_rapi_client, Network,

                               BackendNetwork, BridgePoolTable,

                               MacPrefixPoolTable)

from synnefo.db import pools

from synnefo.logic import utils, rapi, backend as backend_mod

logger = logging.getLogger()

logging.basicConfig()

BUILDING_NIC_TIMEOUT = timedelta(seconds=120)

class BackendReconciler(object):

    def __init__(self, backend, logger, options=None):

        self.backend = backend

        self.log = logger

        self.client = backend.get_client()

        if options is None:

            self.options = {}

        else:

            self.options = options

    def close(self):

        self.backend.put_client(self.client)

    @transaction.commit_on_success

    def reconcile(self):

        log = self.log

        backend = self.backend

        log.debug("Reconciling backend %s", backend)

        self.db_servers = get_database_servers(backend)

        self.db_servers_keys = set(self.db_servers.keys())

        log.debug("Got servers info from database.")

        self.gnt_servers = get_ganeti_servers(backend)

        self.gnt_servers_keys = set(self.gnt_servers.keys())

        log.debug("Got servers info from Ganeti backend.")

        self.gnt_jobs = get_ganeti_jobs(backend)

        log.debug("Got jobs from Ganeti backend")

        self.event_time = datetime.now()

        self.stale_servers = self.reconcile_stale_servers()

        self.orphan_servers = self.reconcile_orphan_servers()

        self.unsynced_servers = self.reconcile_unsynced_servers()

        self.close()

    def get_build_status(self, db_server):

        job_id = db_server.backendjobid

        if job_id in self.gnt_jobs:

            gnt_job_status = self.gnt_jobs[job_id]["status"]

            if gnt_job_status == rapi.JOB_STATUS_ERROR:

                return "ERROR"

            elif gnt_job_status not in rapi.JOB_STATUS_FINALIZED:

                return "RUNNING"

            else:

                return "FINALIZED"

        else:

            return "ERROR"

    def reconcile_stale_servers(self):

        # Detect stale servers

        stale = []

        stale_keys = self.db_servers_keys - self.gnt_servers_keys

        for server_id in stale_keys:

            db_server = self.db_servers[server_id]

            if db_server.operstate == "BUILD":

                build_status = self.get_build_status(db_server)

                if build_status == "ERROR":

                    # Special handling of BUILD eerrors

                    self.reconcile_building_server(db_server)

                elif build_status != "RUNNING":

                    stale.append(server_id)

            elif (db_server.operstate == "ERROR" and

                  db_server.action != "DESTROY"):

                # Servers at building ERROR are stale only if the user has

                # asked to destroy them.

                pass

            else:

                stale.append(server_id)

        # Report them

        if stale:

            self.log.info("Found stale servers %s at backend %s",

                          ", ".join(map(str, stale)), self.backend)

        else:

            self.log.debug("No stale servers at backend %s", self.backend)

        # Fix them

        if stale and self.options["fix_stale"]:

            for server_id in stale:

                vm = get_locked_server(server_id)

                backend_mod.process_op_status(

                    vm=vm,

                    etime=self.event_time,

                    jobid=-0,

                    opcode='OP_INSTANCE_REMOVE', status='success',

                    logmsg='Reconciliation: simulated Ganeti event')

            self.log.debug("Simulated Ganeti removal for stale servers.")

    def reconcile_orphan_servers(self):

        orphans = self.gnt_servers_keys - self.db_servers_keys

        if orphans:

            self.log.info("Found orphan servers %s at backend %s",

                          ", ".join(map(str, orphans)), self.backend)

        else:

            self.log.debug("No orphan servers at backend %s", self.backend)

        if orphans and self.options["fix_orphans"]:

            for server_id in orphans:

                server_name = utils.id_to_instance_name(server_id)

                self.client.DeleteInstance(server_name)

            self.log.debug("Issued OP_INSTANCE_REMOVE for orphan servers.")

    def reconcile_unsynced_servers(self):

        #log = self.log

        for server_id in self.db_servers_keys & self.gnt_servers_keys:

            db_server = self.db_servers[server_id]

            gnt_server = self.gnt_servers[server_id]

            if db_server.operstate == "BUILD":

                build_status = self.get_build_status(db_server)

                if build_status == "RUNNING":

                    # Do not reconcile building VMs

                    continue

                elif build_status == "ERROR":

                    # Special handling of build errors

                    self.reconcile_building_server(db_server)

                    continue

            self.reconcile_unsynced_operstate(server_id, db_server,

                                              gnt_server)

            self.reconcile_unsynced_flavor(server_id, db_server,

                                           gnt_server)

            self.reconcile_unsynced_nics(server_id, db_server, gnt_server)

            self.reconcile_unsynced_disks(server_id, db_server, gnt_server)

            if db_server.task is not None:

                self.reconcile_pending_task(server_id, db_server)

    def reconcile_building_server(self, db_server):

        self.log.info("Server '%s' is BUILD in DB, but 'ERROR' in Ganeti.",

                      db_server.id)

        if self.options["fix_unsynced"]:

            fix_opcode = "OP_INSTANCE_CREATE"

            vm = get_locked_server(db_server.id)

            backend_mod.process_op_status(

                vm=vm,

                etime=self.event_time,

                jobid=-0,

                opcode=fix_opcode, status='error',

                logmsg='Reconciliation: simulated Ganeti event')

            self.log.debug("Simulated Ganeti error build event for"

                           " server '%s'", db_server.id)

    def reconcile_unsynced_operstate(self, server_id, db_server, gnt_server):

        if db_server.operstate != gnt_server["state"]:

            self.log.info("Server '%s' is '%s' in DB and '%s' in Ganeti.",

                          server_id, db_server.operstate, gnt_server["state"])

            if self.options["fix_unsynced"]:

                vm = get_locked_server(server_id)

                # If server is in building state, you will have first to

                # reconcile it's creation, to avoid wrong quotas

                if db_server.operstate == "BUILD":

                    backend_mod.process_op_status(

                        vm=vm, etime=self.event_time, jobid=-0,

                        opcode="OP_INSTANCE_CREATE", status='success',

                        logmsg='Reconciliation: simulated Ganeti event')

                fix_opcode = "OP_INSTANCE_STARTUP"\

                    if gnt_server["state"] == "STARTED"\

                    else "OP_INSTANCE_SHUTDOWN"

                backend_mod.process_op_status(

                    vm=vm, etime=self.event_time, jobid=-0,

                    opcode=fix_opcode, status='success',

                    logmsg='Reconciliation: simulated Ganeti event')

                self.log.debug("Simulated Ganeti state event for server '%s'",

                               server_id)

    def reconcile_unsynced_flavor(self, server_id, db_server, gnt_server):

        db_flavor = db_server.flavor

        gnt_flavor = gnt_server["flavor"]

        if (db_flavor.ram != gnt_flavor["ram"] or

           db_flavor.cpu != gnt_flavor["vcpus"]):

            try:

                gnt_flavor = Flavor.objects.get(

                    ram=gnt_flavor["ram"],

                    cpu=gnt_flavor["vcpus"],

                    disk=db_flavor.disk,

                    disk_template=db_flavor.disk_template)

            except Flavor.DoesNotExist:

                self.log.warning("Server '%s' has unknown flavor.", server_id)

                return

            self.log.info("Server '%s' has flavor '%s' in DB and '%s' in"

                          " Ganeti", server_id, db_flavor, gnt_flavor)

            if self.options["fix_unsynced_flavors"]:

                vm = get_locked_server(server_id)

                old_state = vm.operstate

                opcode = "OP_INSTANCE_SET_PARAMS"

                beparams = {"vcpus": gnt_flavor.cpu,

                            "minmem": gnt_flavor.ram,

                            "maxmem": gnt_flavor.ram}

                backend_mod.process_op_status(

                    vm=vm, etime=self.event_time, jobid=-0,

                    opcode=opcode, status='success',

                    job_fields={"beparams": beparams},

                    logmsg='Reconciliation: simulated Ganeti event')

                # process_op_status with beparams will set the vmstate to

                # shutdown. Fix this be returning it to old state

                vm = VirtualMachine.objects.get(pk=server_id)

                vm.operstate = old_state

                vm.save()

                self.log.debug("Simulated Ganeti flavor event for server '%s'",

                               server_id)

    def reconcile_unsynced_nics(self, server_id, db_server, gnt_server):

        building_time = self.event_time - BUILDING_NIC_TIMEOUT

        db_nics = db_server.nics.exclude(state="BUILD",

                                         created__lte=building_time) \

                                .order_by("id")

        gnt_nics = gnt_server["nics"]

        gnt_nics_parsed = backend_mod.process_ganeti_nics(gnt_nics)

        nics_changed = len(db_nics) != len(gnt_nics)

        for db_nic, gnt_nic in zip(db_nics, sorted(gnt_nics_parsed.items())):

            gnt_nic_id, gnt_nic = gnt_nic

            if (db_nic.id == gnt_nic_id) and\

               backend_mod.nics_are_equal(db_nic, gnt_nic):

                continue

            else:

                nics_changed = True

                break

        if nics_changed:

            msg = "Found unsynced NICs for server '%s'.\n"\

                  "\tDB:\n\t\t%s\n\tGaneti:\n\t\t%s"

            db_nics_str = "\n\t\t".join(map(format_db_nic, db_nics))

            gnt_nics_str = "\n\t\t".join(map(format_gnt_nic,

                                         sorted(gnt_nics_parsed.items())))

            self.log.info(msg, server_id, db_nics_str, gnt_nics_str)

            if self.options["fix_unsynced_nics"]:

                vm = get_locked_server(server_id)

                backend_mod.process_net_status(vm=vm,

                                               etime=self.event_time,

                                               nics=gnt_nics)

    def reconcile_unsynced_disks(self, server_id, db_server, gnt_server):

        pass

    def reconcile_pending_task(self, server_id, db_server):

        job_id = db_server.task_job_id

        pending_task = False

        if job_id not in self.gnt_jobs:

            pending_task = True

        else:

            gnt_job_status = self.gnt_jobs[job_id]["status"]

            if gnt_job_status in rapi.JOB_STATUS_FINALIZED:

                pending_task = True

        if pending_task:

            db_server = get_locked_server(server_id)

            if db_server.task_job_id != job_id:

                # task has changed!

                return

            self.log.info("Found server '%s' with pending task: '%s'",

                          server_id, db_server.task)

            if self.options["fix_pending_tasks"]:

                db_server.task = None

                db_server.task_job_id = None

                db_server.save()

                self.log.info("Cleared pending task for server '%s", server_id)

NIC_MSG = ": %s\t".join(["ID", "State", "IP", "Network", "MAC", "Index",

                         "Firewall"]) + ": %s"

def format_db_nic(nic):

    return NIC_MSG % (nic.id, nic.state, nic.ipv4_address, nic.network_id,

                      nic.mac, nic.index, nic.firewall_profile)

def format_gnt_nic(nic):

    nic_name, nic = nic

    return NIC_MSG % (nic_name, nic["state"], nic["ipv4_address"],

                      nic["network"].id, nic["mac"], nic["index"],

                      nic["firewall_profile"])

#

# Networks

#

def get_networks_from_ganeti(backend):

    prefix = settings.BACKEND_PREFIX_ID + 'net-'

    networks = {}

    with pooled_rapi_client(backend) as c:

        for net in c.GetNetworks(bulk=True):

            if net['name'].startswith(prefix):

                id = utils.id_from_network_name(net['name'])

                networks[id] = net

    return networks

def hanging_networks(backend, GNets):

    """Get networks that are not connected to all Nodegroups.

    """

    def get_network_groups(group_list):

        groups = set()

        for (name, mode, link) in group_list:

            groups.add(name)

        return groups

    with pooled_rapi_client(backend) as c:

        groups = set(c.GetGroups())

    hanging = {}

    for id, info in GNets.items():

        group_list = get_network_groups(info['group_list'])

        if group_list != groups:

            hanging[id] = groups - group_list

    return hanging

def get_online_backends():

    return Backend.objects.filter(offline=False)

def get_database_servers(backend):

    servers = backend.virtual_machines.select_related("flavor")\

                                      .prefetch_related("nics__ips__subnet")\

                                      .filter(deleted=False)

    return dict([(s.id, s) for s in servers])

def get_ganeti_servers(backend):

    gnt_instances = backend_mod.get_instances(backend)

    # Filter out non-synnefo instances

    snf_backend_prefix = settings.BACKEND_PREFIX_ID

    gnt_instances = filter(lambda i: i["name"].startswith(snf_backend_prefix),

                           gnt_instances)

    gnt_instances = map(parse_gnt_instance, gnt_instances)

    return dict([(i["id"], i) for i in gnt_instances if i["id"] is not None])

def parse_gnt_instance(instance):

    try:

        instance_id = utils.id_from_instance_name(instance['name'])

    except Exception:

        logger.error("Ignoring instance with malformed name %s",

                     instance['name'])

        return (None, None)

    beparams = instance["beparams"]

    vcpus = beparams["vcpus"]

    ram = beparams["maxmem"]

    state = instance["oper_state"] and "STARTED" or "STOPPED"

    return {

        "id": instance_id,

        "state": state,  # FIX

        "updated": datetime.fromtimestamp(instance["mtime"]),

        "disks": disks_from_instance(instance),

        "nics": nics_from_instance(instance),

        "flavor": {"vcpus": vcpus,

                   "ram": ram},

        "tags": instance["tags"]

    }

def nics_from_instance(i):

    ips = zip(itertools.repeat('ip'), i['nic.ips'])

    names = zip(itertools.repeat('name'), i['nic.names'])

    macs = zip(itertools.repeat('mac'), i['nic.macs'])

    networks = zip(itertools.repeat('network'), i['nic.networks.names'])

    # modes = zip(itertools.repeat('mode'), i['nic.modes'])

    # links = zip(itertools.repeat('link'), i['nic.links'])

    # nics = zip(ips,macs,modes,networks,links)

    nics = zip(ips, names, macs, networks)

    nics = map(lambda x: dict(x), nics)

    #nics = dict(enumerate(nics))

    tags = i["tags"]

    for tag in tags:

        t = tag.split(":")

        if t[0:2] == ["synnefo", "network"]:

            if len(t) != 4:

                logger.error("Malformed synefo tag %s", tag)

                continue

            nic_name = t[2]

            firewall = t[3]

            [nic.setdefault("firewall", firewall)

             for nic in nics if nic["name"] == nic_name]

    return nics

def get_ganeti_jobs(backend):

    gnt_jobs = backend_mod.get_jobs(backend)

    return dict([(int(j["id"]), j) for j in gnt_jobs])

def disks_from_instance(i):

    return dict([(index, {"size": size})

                 for index, size in enumerate(i["disk.sizes"])])

class NetworkReconciler(object):

    def __init__(self, logger, fix=False):

        self.log = logger

        self.fix = fix

    @transaction.commit_on_success

    def reconcile_networks(self):

        # Get models from DB

        self.backends = Backend.objects.exclude(offline=True)

        self.networks = Network.objects.filter(deleted=False)

        self.event_time = datetime.now()

        # Get info from all ganeti backends

        self.ganeti_networks = {}

        self.ganeti_hanging_networks = {}

        for b in self.backends:

            g_nets = get_networks_from_ganeti(b)

            self.ganeti_networks[b] = g_nets

            g_hanging_nets = hanging_networks(b, g_nets)

            self.ganeti_hanging_networks[b] = g_hanging_nets

        self._reconcile_orphan_networks()

        for network in self.networks:

            self._reconcile_network(network)

    @transaction.commit_on_success

    def _reconcile_network(self, network):

        """Reconcile a network with corresponging Ganeti networks.

        Reconcile a Network and the associated BackendNetworks with the

        corresponding Ganeti networks in all Ganeti backends.

        """

        if network.subnets.filter(ipversion=4, dhcp=True).exists():

            ip_pools = network.get_ip_pools()  # X-Lock on IP pools

        else:

            ip_pools = None

        for bend in self.backends:

            bnet = get_backend_network(network, bend)

            gnet = self.ganeti_networks[bend].get(network.id)

            if bnet is None and gnet is not None:

                # Network exists in backend but not in DB for this backend

                bnet = self.reconcile_parted_network(network, bend)

            if bnet is None:

                continue

            if gnet is None:

                # Network does not exist in Ganeti. If the network action

                # is DESTROY, we have to mark as deleted in DB, else we

                # have to create it in Ganeti.

                if network.action == "DESTROY":

                    if bnet.operstate != "DELETED":

                        self.reconcile_stale_network(bnet)

                else:

                    self.reconcile_missing_network(network, bend)

                # Skip rest reconciliation!

                continue

            try:

                hanging_groups = self.ganeti_hanging_networks[bend][network.id]

            except KeyError:

                # Network is connected to all nodegroups

                hanging_groups = []

            if hanging_groups:

                # CASE-3: Ganeti networks not connected to all nodegroups

                self.reconcile_hanging_groups(network, bend,

                                              hanging_groups)

                continue

            if bnet.operstate != 'ACTIVE':

                # CASE-4: Unsynced network state. At this point the network

                # exists and is connected to all nodes so is must be

                # active!

                self.reconcile_unsynced_network(network, bend, bnet)

            # Check that externally reserved IPs of the network in Ganeti are

            # also externally reserved to the IP pool

            externally_reserved = gnet['external_reservations']

            if externally_reserved and ip_pools is not None:

                for ip in externally_reserved.split(","):

                    ip = ip.strip()

                    for ip_pool in ip_pools:

                        if ip_pool.contains(ip):

                            if not ip_pool.is_reserved(ip):

                                msg = ("D: IP '%s' is reserved for network"

                                       " '%s' in backend '%s' but not in DB.")

                                self.log.info(msg, ip, network, bend)

                                if self.fix:

                                    ip_pool.reserve(ip, external=True)

                                    ip_pool.save()

                                    self.log.info("F: Reserved IP '%s'", ip)

        if network.state != "ACTIVE":

            network = Network.objects.select_for_update().get(id=network.id)

            backend_mod.update_network_state(network)

    def reconcile_parted_network(self, network, backend):

        self.log.info("D: Missing DB entry for network %s in backend %s",

                      network, backend)

        if self.fix:

            network.create_backend_network(backend)

            self.log.info("F: Created DB entry")

            bnet = get_backend_network(network, backend)

            return bnet

    def reconcile_stale_network(self, backend_network):

        self.log.info("D: Stale DB entry for network %s in backend %s",

                      backend_network.network, backend_network.backend)

        if self.fix:

            backend_network = BackendNetwork.objects.select_for_update()\

                                                    .get(id=backend_network.id)

            backend_mod.process_network_status(

                backend_network, self.event_time, 0,

                "OP_NETWORK_REMOVE",

                "success",

                "Reconciliation simulated event")

            self.log.info("F: Reconciled event: OP_NETWORK_REMOVE")

    def reconcile_missing_network(self, network, backend):

        self.log.info("D: Missing Ganeti network %s in backend %s",

                      network, backend)

        if self.fix:

            backend_mod.create_network(network, backend)

            self.log.info("F: Issued OP_NETWORK_CONNECT")

    def reconcile_hanging_groups(self, network, backend, hanging_groups):

        self.log.info('D: Network %s in backend %s is not connected to '

                      'the following groups:', network, backend)

        self.log.info('-  ' + '\n-  '.join(hanging_groups))

        if self.fix:

            for group in hanging_groups:

                self.log.info('F: Connecting network %s to nodegroup %s',

                              network, group)

                backend_mod.connect_network(network, backend, depends=[],

                                            group=group)

    def reconcile_unsynced_network(self, network, backend, backend_network):

        self.log.info("D: Unsynced network %s in backend %s", network, backend)

        if self.fix:

            self.log.info("F: Issuing OP_NETWORK_CONNECT")

            backend_network = BackendNetwork.objects.select_for_update()\

                                                    .get(id=backend_network.id)

            backend_mod.process_network_status(

                backend_network, self.event_time, 0,

                "OP_NETWORK_CONNECT",

                "success",

                "Reconciliation simulated eventd")

    def _reconcile_orphan_networks(self):

        db_networks = self.networks

        ganeti_networks = self.ganeti_networks

        # Detect Orphan Networks in Ganeti

        db_network_ids = set([net.id for net in db_networks])

        for back_end, ganeti_networks in ganeti_networks.items():

            ganeti_network_ids = set(ganeti_networks.keys())

            orphans = ganeti_network_ids - db_network_ids

            if len(orphans) > 0:

                self.log.info('D: Orphan Networks in backend %s:',

                              back_end.clustername)

                self.log.info('-  ' + '\n-  '.join([str(o) for o in orphans]))

                if self.fix:

                    for net_id in orphans:

                        self.log.info('Disconnecting and deleting network %d',

                                      net_id)

                        try:

                            network = Network.objects.get(id=net_id)

                            backend_mod.delete_network(network,

                                                       backend=back_end)

                        except Network.DoesNotExist:

                            self.log.info("Not entry for network %s in DB !!",

                                          net_id)

def get_backend_network(network, backend):

    try:

        return BackendNetwork.objects.get(network=network, backend=backend)

    except BackendNetwork.DoesNotExist:

        return None

class PoolReconciler(object):

    def __init__(self, logger, fix=False):

        self.log = logger

        self.fix = fix

    def reconcile(self):

        self.reconcile_bridges()

        self.reconcile_mac_prefixes()

        networks = Network.objects.prefetch_related("subnets")\

                                  .filter(deleted=False)

        for network in networks:

            for subnet in network.subnets.all():

                if subnet.ipversion == 4 and subnet.dhcp:

                    self.reconcile_ip_pool(network)

    @transaction.commit_on_success

    def reconcile_bridges(self):

        networks = Network.objects.filter(deleted=False,

                                          flavor="PHYSICAL_VLAN")

        check_unique_values(objects=networks, field='link', logger=self.log)

        try:

            pool = BridgePoolTable.get_pool()

        except pools.EmptyPool:

            self.log.info("There is no available pool for bridges.")

            return

        # Since pool is locked, no new networks may be created

        used_bridges = set(networks.values_list('link', flat=True))

        check_pool_consistent(pool=pool, pool_class=pools.BridgePool,

                              used_values=used_bridges, fix=self.fix,

                              logger=self.log)

    @transaction.commit_on_success

    def reconcile_mac_prefixes(self):

        networks = Network.objects.filter(deleted=False, flavor="MAC_FILTERED")

        check_unique_values(objects=networks, field='mac_prefix',

                            logger=self.log)

        try:

            pool = MacPrefixPoolTable.get_pool()

        except pools.EmptyPool:

            self.log.info("There is no available pool for MAC prefixes.")

            return

        # Since pool is locked, no new network may be created

        used_mac_prefixes = set(networks.values_list('mac_prefix', flat=True))

        check_pool_consistent(pool=pool, pool_class=pools.MacPrefixPool,

                              used_values=used_mac_prefixes, fix=self.fix,

                              logger=self.log)

    @transaction.commit_on_success

    def reconcile_ip_pool(self, network):

        # Check that all NICs have unique IPv4 address

        nics = network.ips.exclude(address__isnull=True).all()

        check_unique_values(objects=nics, field="address", logger=self.log)

        for ip_pool in network.get_ip_pools():

            # IP pool is now locked, so no new IPs may be created

            used_ips = ip_pool.pool_table.subnet\

                              .ips.exclude(address__isnull=True)\

                              .exclude(deleted=True)\

                              .values_list("address", flat=True)

            used_ips = filter(lambda x: ip_pool.contains(x), used_ips)

            check_pool_consistent(pool=ip_pool,

                                  pool_class=pools.IPPool,

                                  used_values=used_ips,

                                  fix=self.fix, logger=self.log)

def check_unique_values(objects, field, logger):

    used_values = list(objects.values_list(field, flat=True))

    if len(used_values) != len(set(used_values)):

        duplicate_values = [v for v in used_values if used_values.count(v) > 1]

        for value in duplicate_values:

            filter_args = {field: value}

            using_objects = objects.filter(**filter_args)

            msg = "Value '%s' is used as %s for more than one objects: %s"

            logger.error(msg, value, field, ",".join(map(str, using_objects)))

        return False

    logger.debug("Values for field '%s' are unique.", field)

    return True

def check_pool_consistent(pool, pool_class, used_values, fix, logger):

    dummy_pool = create_empty_pool(pool, pool_class)

    [dummy_pool.reserve(value) for value in used_values]

    if dummy_pool.available != pool.available:

        msg = "'%s' is not consistent!\nPool: %s\nUsed: %s"

        pool_diff = dummy_pool.available ^ pool.available

        for index in pool_diff.itersearch(bitarray.bitarray("1")):

            value = pool.index_to_value(int(index))

            msg = "%s is incosistent! Value '%s' is %s but should be %s."

            value1 = pool.is_available(value) and "available" or "unavailable"

            value2 = dummy_pool.is_available(value) and "available"\

                or "unavailable"

            logger.error(msg, pool, value, value1, value2)

        if fix:

            pool.available = dummy_pool.available

            pool.save()

            logger.info("Fixed available map of pool '%s'", pool)

def create_empty_pool(pool, pool_class):

    pool_row = pool.pool_table

    pool_row.available_map = ""

    pool_row.reserved_map = ""

    return pool_class(pool_row)

def get_locked_server(server_id):

    return VirtualMachine.objects.select_for_update().get(id=server_id)