A set of Neutron drivers for the VMware NSX.
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# Copyright 2013 VMware, Inc.
# All Rights Reserved
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
import copy
import random
from neutron_lib import constants
from neutron_lib import exceptions
from oslo_log import log
from oslo_serialization import jsonutils
from oslo_service import loopingcall
from oslo_utils import timeutils
import six
from neutron import context
from neutron.db import external_net_db
from neutron.db import l3_db
from neutron.db import models_v2
from neutron.extensions import l3
from vmware_nsx._i18n import _, _LE, _LI, _LW
from vmware_nsx.api_client import exception as api_exc
from vmware_nsx.common import exceptions as nsx_exc
from vmware_nsx.common import nsx_utils
from vmware_nsx.nsxlib import mh as nsxlib
from vmware_nsx.nsxlib.mh import router as routerlib
from vmware_nsx.nsxlib.mh import switch as switchlib
# Maximum page size for a single request
# NOTE(salv-orlando): This might become a version-dependent map should the
# limit be raised in future versions
MAX_PAGE_SIZE = 5000
LOG = log.getLogger(__name__)
class NsxCache(object):
"""A simple Cache for NSX resources.
Associates resource id with resource hash to rapidly identify
updated resources.
Each entry in the cache also stores the following information:
- changed: the resource in the cache has been altered following
an update or a delete
- hit: the resource has been visited during an update (and possibly
left unchanged)
- data: current resource data
- data_bk: backup of resource data prior to its removal
"""
def __init__(self):
# Maps an uuid to the dict containing it
self._uuid_dict_mappings = {}
# Dicts for NSX cached resources
self._lswitches = {}
self._lswitchports = {}
self._lrouters = {}
def __getitem__(self, key):
# uuids are unique across the various types of resources
# TODO(salv-orlando): Avoid lookups over all dictionaries
# when retrieving items
# Fetch lswitches, lports, or lrouters
resources = self._uuid_dict_mappings[key]
return resources[key]
def _clear_changed_flag_and_remove_from_cache(self, resources):
# Clear the 'changed' attribute for all items
# NOTE(arosen): the copy.copy is to avoid: 'RuntimeError:
# dictionary changed size during iteration' for py3
for uuid, item in copy.copy(resources).items():
if item.pop('changed', None) and not item.get('data'):
# The item is not anymore in NSX, so delete it
del resources[uuid]
del self._uuid_dict_mappings[uuid]
LOG.debug("Removed item %s from NSX object cache", uuid)
def _update_resources(self, resources, new_resources, clear_changed=True):
if clear_changed:
self._clear_changed_flag_and_remove_from_cache(resources)
def do_hash(item):
return hash(jsonutils.dumps(item))
# Parse new data and identify new, deleted, and updated resources
for item in new_resources:
item_id = item['uuid']
if resources.get(item_id):
new_hash = do_hash(item)
if new_hash != resources[item_id]['hash']:
resources[item_id]['hash'] = new_hash
resources[item_id]['changed'] = True
resources[item_id]['data_bk'] = (
resources[item_id]['data'])
resources[item_id]['data'] = item
# Mark the item as hit in any case
resources[item_id]['hit'] = True
LOG.debug("Updating item %s in NSX object cache", item_id)
else:
resources[item_id] = {'hash': do_hash(item)}
resources[item_id]['hit'] = True
resources[item_id]['changed'] = True
resources[item_id]['data'] = item
# add an uuid to dict mapping for easy retrieval
# with __getitem__
self._uuid_dict_mappings[item_id] = resources
LOG.debug("Added item %s to NSX object cache", item_id)
def _delete_resources(self, resources):
# Mark for removal all the elements which have not been visited.
# And clear the 'hit' attribute.
for to_delete in [k for (k, v) in six.iteritems(resources)
if not v.pop('hit', False)]:
resources[to_delete]['changed'] = True
resources[to_delete]['data_bk'] = (
resources[to_delete].pop('data', None))
def _get_resource_ids(self, resources, changed_only):
if changed_only:
return [k for (k, v) in six.iteritems(resources)
if v.get('changed')]
return resources.keys()
def get_lswitches(self, changed_only=False):
return self._get_resource_ids(self._lswitches, changed_only)
def get_lrouters(self, changed_only=False):
return self._get_resource_ids(self._lrouters, changed_only)
def get_lswitchports(self, changed_only=False):
return self._get_resource_ids(self._lswitchports, changed_only)
def update_lswitch(self, lswitch):
self._update_resources(self._lswitches, [lswitch], clear_changed=False)
def update_lrouter(self, lrouter):
self._update_resources(self._lrouters, [lrouter], clear_changed=False)
def update_lswitchport(self, lswitchport):
self._update_resources(self._lswitchports, [lswitchport],
clear_changed=False)
def process_updates(self, lswitches=None,
lrouters=None, lswitchports=None):
self._update_resources(self._lswitches, lswitches)
self._update_resources(self._lrouters, lrouters)
self._update_resources(self._lswitchports, lswitchports)
return (self._get_resource_ids(self._lswitches, changed_only=True),
self._get_resource_ids(self._lrouters, changed_only=True),
self._get_resource_ids(self._lswitchports, changed_only=True))
def process_deletes(self):
self._delete_resources(self._lswitches)
self._delete_resources(self._lrouters)
self._delete_resources(self._lswitchports)
return (self._get_resource_ids(self._lswitches, changed_only=True),
self._get_resource_ids(self._lrouters, changed_only=True),
self._get_resource_ids(self._lswitchports, changed_only=True))
class SyncParameters(object):
"""Defines attributes used by the synchronization procedure.
chunk_size: Actual chunk size
extra_chunk_size: Additional data to fetch because of chunk size
adjustment
current_chunk: Counter of the current data chunk being synchronized
Page cursors: markers for the next resource to fetch.
'start' means page cursor unset for fetching 1st page
init_sync_performed: True if the initial synchronization concluded
"""
def __init__(self, min_chunk_size):
self.chunk_size = min_chunk_size
self.extra_chunk_size = 0
self.current_chunk = 0
self.ls_cursor = 'start'
self.lr_cursor = 'start'
self.lp_cursor = 'start'
self.init_sync_performed = False
self.total_size = 0
def _start_loopingcall(min_chunk_size, state_sync_interval, func,
initial_delay=5):
"""Start a loopingcall for the synchronization task."""
# Start a looping call to synchronize operational status
# for neutron resources
if not state_sync_interval:
# do not start the looping call if specified
# sync interval is 0
return
state_synchronizer = loopingcall.DynamicLoopingCall(
func, sp=SyncParameters(min_chunk_size))
state_synchronizer.start(
initial_delay=initial_delay,
periodic_interval_max=state_sync_interval)
return state_synchronizer
class NsxSynchronizer(object):
LS_URI = nsxlib._build_uri_path(
switchlib.LSWITCH_RESOURCE, fields='uuid,tags,fabric_status',
relations='LogicalSwitchStatus')
LR_URI = nsxlib._build_uri_path(
routerlib.LROUTER_RESOURCE, fields='uuid,tags,fabric_status',
relations='LogicalRouterStatus')
LP_URI = nsxlib._build_uri_path(
switchlib.LSWITCHPORT_RESOURCE,
parent_resource_id='*',
fields='uuid,tags,fabric_status_up',
relations='LogicalPortStatus')
def __init__(self, plugin, cluster, state_sync_interval,
req_delay, min_chunk_size, max_rand_delay=0,
initial_delay=5):
random.seed()
self._nsx_cache = NsxCache()
# Store parameters as instance members
# NOTE(salv-orlando): apologies if it looks java-ish
self._plugin = plugin
self._cluster = cluster
self._req_delay = req_delay
self._sync_interval = state_sync_interval
self._max_rand_delay = max_rand_delay
# Validate parameters
if self._sync_interval < self._req_delay:
err_msg = (_("Minimum request delay:%(req_delay)s must not "
"exceed synchronization interval:%(sync_interval)s") %
{'req_delay': self._req_delay,
'sync_interval': self._sync_interval})
LOG.error(err_msg)
raise nsx_exc.NsxPluginException(err_msg=err_msg)
# Backoff time in case of failures while fetching sync data
self._sync_backoff = 1
# Store the looping call in an instance variable to allow unit tests
# for controlling its lifecycle
self._sync_looping_call = _start_loopingcall(
min_chunk_size, state_sync_interval,
self._synchronize_state, initial_delay=initial_delay)
def _get_tag_dict(self, tags):
return dict((tag.get('scope'), tag['tag']) for tag in tags)
def synchronize_network(self, context, neutron_network_data,
lswitches=None):
"""Synchronize a Neutron network with its NSX counterpart.
This routine synchronizes a set of switches when a Neutron
network is mapped to multiple lswitches.
"""
if not lswitches:
# Try to get logical switches from nsx
try:
lswitches = nsx_utils.fetch_nsx_switches(
context.session, self._cluster,
neutron_network_data['id'])
except exceptions.NetworkNotFound:
# TODO(salv-orlando): We should be catching
# api_exc.ResourceNotFound here
# The logical switch was not found
LOG.warning(_LW("Logical switch for neutron network %s not "
"found on NSX."), neutron_network_data['id'])
lswitches = []
else:
for lswitch in lswitches:
self._nsx_cache.update_lswitch(lswitch)
# By default assume things go wrong
status = constants.NET_STATUS_ERROR
# In most cases lswitches will contain a single element
for ls in lswitches:
if not ls:
# Logical switch was deleted
break
ls_status = ls['_relations']['LogicalSwitchStatus']
if not ls_status['fabric_status']:
status = constants.NET_STATUS_DOWN
break
else:
# No switch was down or missing. Set status to ACTIVE unless
# there were no switches in the first place!
if lswitches:
status = constants.NET_STATUS_ACTIVE
# Update db object
if status == neutron_network_data['status']:
# do nothing
return
with context.session.begin(subtransactions=True):
try:
network = self._plugin._get_network(context,
neutron_network_data['id'])
except exceptions.NetworkNotFound:
pass
else:
network.status = status
LOG.debug("Updating status for neutron resource %(q_id)s to:"
" %(status)s",
{'q_id': neutron_network_data['id'],
'status': status})
def _synchronize_lswitches(self, ctx, ls_uuids, scan_missing=False):
if not ls_uuids and not scan_missing:
return
neutron_net_ids = set()
neutron_nsx_mappings = {}
# TODO(salvatore-orlando): Deal with the case the tag
# has been tampered with
for ls_uuid in ls_uuids:
# If the lswitch has been deleted, get backup copy of data
lswitch = (self._nsx_cache[ls_uuid].get('data') or
self._nsx_cache[ls_uuid].get('data_bk'))
tags = self._get_tag_dict(lswitch['tags'])
neutron_id = tags.get('quantum_net_id')
neutron_net_ids.add(neutron_id)
neutron_nsx_mappings[neutron_id] = (
neutron_nsx_mappings.get(neutron_id, []) +
[self._nsx_cache[ls_uuid]])
# Fetch neutron networks from database
filters = {'router:external': [False]}
if not scan_missing:
filters['id'] = neutron_net_ids
networks = self._plugin._get_collection(
ctx, models_v2.Network, self._plugin._make_network_dict,
filters=filters)
for network in networks:
lswitches = neutron_nsx_mappings.get(network['id'], [])
lswitches = [lsw.get('data') for lsw in lswitches]
self.synchronize_network(ctx, network, lswitches)
def synchronize_router(self, context, neutron_router_data,
lrouter=None):
"""Synchronize a neutron router with its NSX counterpart."""
if not lrouter:
# Try to get router from nsx
try:
# This query will return the logical router status too
nsx_router_id = nsx_utils.get_nsx_router_id(
context.session, self._cluster, neutron_router_data['id'])
if nsx_router_id:
lrouter = routerlib.get_lrouter(
self._cluster, nsx_router_id)
except exceptions.NotFound:
# NOTE(salv-orlando): We should be catching
# api_exc.ResourceNotFound here
# The logical router was not found
LOG.warning(_LW("Logical router for neutron router %s not "
"found on NSX."), neutron_router_data['id'])
if lrouter:
# Update the cache
self._nsx_cache.update_lrouter(lrouter)
# Note(salv-orlando): It might worth adding a check to verify neutron
# resource tag in nsx entity matches a Neutron id.
# By default assume things go wrong
status = constants.NET_STATUS_ERROR
if lrouter:
lr_status = (lrouter['_relations']
['LogicalRouterStatus']
['fabric_status'])
status = (lr_status and
constants.NET_STATUS_ACTIVE
or constants.NET_STATUS_DOWN)
# Update db object
if status == neutron_router_data['status']:
# do nothing
return
with context.session.begin(subtransactions=True):
try:
router = self._plugin._get_router(context,
neutron_router_data['id'])
except l3.RouterNotFound:
pass
else:
router.status = status
LOG.debug("Updating status for neutron resource %(q_id)s to:"
" %(status)s",
{'q_id': neutron_router_data['id'],
'status': status})
def _synchronize_lrouters(self, ctx, lr_uuids, scan_missing=False):
if not lr_uuids and not scan_missing:
return
# TODO(salvatore-orlando): Deal with the case the tag
# has been tampered with
neutron_router_mappings = {}
for lr_uuid in lr_uuids:
lrouter = (self._nsx_cache[lr_uuid].get('data') or
self._nsx_cache[lr_uuid].get('data_bk'))
tags = self._get_tag_dict(lrouter['tags'])
neutron_router_id = tags.get('q_router_id')
if neutron_router_id:
neutron_router_mappings[neutron_router_id] = (
self._nsx_cache[lr_uuid])
else:
LOG.warning(_LW("Unable to find Neutron router id for "
"NSX logical router: %s"), lr_uuid)
# Fetch neutron routers from database
filters = ({} if scan_missing else
{'id': neutron_router_mappings.keys()})
routers = self._plugin._get_collection(
ctx, l3_db.Router, self._plugin._make_router_dict,
filters=filters)
for router in routers:
lrouter = neutron_router_mappings.get(router['id'])
self.synchronize_router(
ctx, router, lrouter and lrouter.get('data'))
def synchronize_port(self, context, neutron_port_data,
lswitchport=None, ext_networks=None):
"""Synchronize a Neutron port with its NSX counterpart."""
# Skip synchronization for ports on external networks
if not ext_networks:
ext_networks = [net['id'] for net in context.session.query(
models_v2.Network).join(
external_net_db.ExternalNetwork,
(models_v2.Network.id ==
external_net_db.ExternalNetwork.network_id))]
if neutron_port_data['network_id'] in ext_networks:
with context.session.begin(subtransactions=True):
neutron_port_data['status'] = constants.PORT_STATUS_ACTIVE
return
if not lswitchport:
# Try to get port from nsx
try:
ls_uuid, lp_uuid = nsx_utils.get_nsx_switch_and_port_id(
context.session, self._cluster, neutron_port_data['id'])
if lp_uuid:
lswitchport = switchlib.get_port(
self._cluster, ls_uuid, lp_uuid,
relations='LogicalPortStatus')
except (exceptions.PortNotFoundOnNetwork):
# NOTE(salv-orlando): We should be catching
# api_exc.ResourceNotFound here instead
# of PortNotFoundOnNetwork when the id exists but
# the logical switch port was not found
LOG.warning(_LW("Logical switch port for neutron port %s "
"not found on NSX."), neutron_port_data['id'])
lswitchport = None
else:
# If lswitchport is not None, update the cache.
# It could be none if the port was deleted from the backend
if lswitchport:
self._nsx_cache.update_lswitchport(lswitchport)
# Note(salv-orlando): It might worth adding a check to verify neutron
# resource tag in nsx entity matches Neutron id.
# By default assume things go wrong
status = constants.PORT_STATUS_ERROR
if lswitchport:
lp_status = (lswitchport['_relations']
['LogicalPortStatus']
['fabric_status_up'])
status = (lp_status and
constants.PORT_STATUS_ACTIVE
or constants.PORT_STATUS_DOWN)
# Update db object
if status == neutron_port_data['status']:
# do nothing
return
with context.session.begin(subtransactions=True):
try:
port = self._plugin._get_port(context,
neutron_port_data['id'])
except exceptions.PortNotFound:
pass
else:
port.status = status
LOG.debug("Updating status for neutron resource %(q_id)s to:"
" %(status)s",
{'q_id': neutron_port_data['id'],
'status': status})
def _synchronize_lswitchports(self, ctx, lp_uuids, scan_missing=False):
if not lp_uuids and not scan_missing:
return
# Find Neutron port id by tag - the tag is already
# loaded in memory, no reason for doing a db query
# TODO(salvatore-orlando): Deal with the case the tag
# has been tampered with
neutron_port_mappings = {}
for lp_uuid in lp_uuids:
lport = (self._nsx_cache[lp_uuid].get('data') or
self._nsx_cache[lp_uuid].get('data_bk'))
tags = self._get_tag_dict(lport['tags'])
neutron_port_id = tags.get('q_port_id')
if neutron_port_id:
neutron_port_mappings[neutron_port_id] = (
self._nsx_cache[lp_uuid])
# Fetch neutron ports from database
# At the first sync we need to fetch all ports
filters = ({} if scan_missing else
{'id': neutron_port_mappings.keys()})
# TODO(salv-orlando): Work out a solution for avoiding
# this query
ext_nets = [net['id'] for net in ctx.session.query(
models_v2.Network).join(
external_net_db.ExternalNetwork,
(models_v2.Network.id ==
external_net_db.ExternalNetwork.network_id))]
ports = self._plugin._get_collection(
ctx, models_v2.Port, self._plugin._make_port_dict,
filters=filters)
for port in ports:
lswitchport = neutron_port_mappings.get(port['id'])
self.synchronize_port(
ctx, port, lswitchport and lswitchport.get('data'),
ext_networks=ext_nets)
def _get_chunk_size(self, sp):
# NOTE(salv-orlando): Try to use __future__ for this routine only?
ratio = ((float(sp.total_size) / float(sp.chunk_size)) /
(float(self._sync_interval) / float(self._req_delay)))
new_size = max(1.0, ratio) * float(sp.chunk_size)
return int(new_size) + (new_size - int(new_size) > 0)
def _fetch_data(self, uri, cursor, page_size):
# If not cursor there is nothing to retrieve
if cursor:
if cursor == 'start':
cursor = None
# Chunk size tuning might, in some conditions, make it larger
# than 5,000, which is the maximum page size allowed by the NSX
# API. In this case the request should be split in multiple
# requests. This is not ideal, and therefore a log warning will
# be emitted.
num_requests = page_size // (MAX_PAGE_SIZE + 1) + 1
if num_requests > 1:
LOG.warning(_LW("Requested page size is %(cur_chunk_size)d. "
"It might be necessary to do %(num_requests)d "
"round-trips to NSX for fetching data. Please "
"tune sync parameters to ensure chunk size "
"is less than %(max_page_size)d"),
{'cur_chunk_size': page_size,
'num_requests': num_requests,
'max_page_size': MAX_PAGE_SIZE})
# Only the first request might return the total size,
# subsequent requests will definitely not
results, cursor, total_size = nsxlib.get_single_query_page(
uri, self._cluster, cursor,
min(page_size, MAX_PAGE_SIZE))
for _req in range(num_requests - 1):
# If no cursor is returned break the cycle as there is no
# actual need to perform multiple requests (all fetched)
# This happens when the overall size of resources exceeds
# the maximum page size, but the number for each single
# resource type is below this threshold
if not cursor:
break
req_results, cursor = nsxlib.get_single_query_page(
uri, self._cluster, cursor,
min(page_size, MAX_PAGE_SIZE))[:2]
results.extend(req_results)
# reset cursor before returning if we queried just to
# know the number of entities
return results, cursor if page_size else 'start', total_size
return [], cursor, None
def _fetch_nsx_data_chunk(self, sp):
base_chunk_size = sp.chunk_size
chunk_size = base_chunk_size + sp.extra_chunk_size
LOG.info(_LI("Fetching up to %s resources "
"from NSX backend"), chunk_size)
fetched = ls_count = lr_count = lp_count = 0
lswitches = lrouters = lswitchports = []
if sp.ls_cursor or sp.ls_cursor == 'start':
(lswitches, sp.ls_cursor, ls_count) = self._fetch_data(
self.LS_URI, sp.ls_cursor, chunk_size)
fetched = len(lswitches)
if fetched < chunk_size and sp.lr_cursor or sp.lr_cursor == 'start':
(lrouters, sp.lr_cursor, lr_count) = self._fetch_data(
self.LR_URI, sp.lr_cursor, max(chunk_size - fetched, 0))
fetched += len(lrouters)
if fetched < chunk_size and sp.lp_cursor or sp.lp_cursor == 'start':
(lswitchports, sp.lp_cursor, lp_count) = self._fetch_data(
self.LP_URI, sp.lp_cursor, max(chunk_size - fetched, 0))
fetched += len(lswitchports)
if sp.current_chunk == 0:
# No cursors were provided. Then it must be possible to
# calculate the total amount of data to fetch
sp.total_size = ls_count + lr_count + lp_count
LOG.debug("Total data size: %d", sp.total_size)
sp.chunk_size = self._get_chunk_size(sp)
# Calculate chunk size adjustment
sp.extra_chunk_size = sp.chunk_size - base_chunk_size
LOG.debug("Fetched %(num_lswitches)d logical switches, "
"%(num_lswitchports)d logical switch ports,"
"%(num_lrouters)d logical routers",
{'num_lswitches': len(lswitches),
'num_lswitchports': len(lswitchports),
'num_lrouters': len(lrouters)})
return (lswitches, lrouters, lswitchports)
def _synchronize_state(self, sp):
# If the plugin has been destroyed, stop the LoopingCall
if not self._plugin:
raise loopingcall.LoopingCallDone()
start = timeutils.utcnow()
# Reset page cursor variables if necessary
if sp.current_chunk == 0:
sp.ls_cursor = sp.lr_cursor = sp.lp_cursor = 'start'
LOG.info(_LI("Running state synchronization task. Chunk: %s"),
sp.current_chunk)
# Fetch chunk_size data from NSX
try:
(lswitches, lrouters, lswitchports) = (
self._fetch_nsx_data_chunk(sp))
except (api_exc.RequestTimeout, api_exc.NsxApiException):
sleep_interval = self._sync_backoff
# Cap max back off to 64 seconds
self._sync_backoff = min(self._sync_backoff * 2, 64)
LOG.exception(_LE("An error occurred while communicating with "
"NSX backend. Will retry synchronization "
"in %d seconds"), sleep_interval)
return sleep_interval
LOG.debug("Time elapsed querying NSX: %s",
timeutils.utcnow() - start)
if sp.total_size:
num_chunks = ((sp.total_size / sp.chunk_size) +
(sp.total_size % sp.chunk_size != 0))
else:
num_chunks = 1
LOG.debug("Number of chunks: %d", num_chunks)
# Find objects which have changed on NSX side and need
# to be synchronized
LOG.debug("Processing NSX cache for updated objects")
(ls_uuids, lr_uuids, lp_uuids) = self._nsx_cache.process_updates(
lswitches, lrouters, lswitchports)
# Process removed objects only at the last chunk
scan_missing = (sp.current_chunk == num_chunks - 1 and
not sp.init_sync_performed)
if sp.current_chunk == num_chunks - 1:
LOG.debug("Processing NSX cache for deleted objects")
self._nsx_cache.process_deletes()
ls_uuids = self._nsx_cache.get_lswitches(
changed_only=not scan_missing)
lr_uuids = self._nsx_cache.get_lrouters(
changed_only=not scan_missing)
lp_uuids = self._nsx_cache.get_lswitchports(
changed_only=not scan_missing)
LOG.debug("Time elapsed hashing data: %s",
timeutils.utcnow() - start)
# Get an admin context
ctx = context.get_admin_context()
# Synchronize with database
self._synchronize_lswitches(ctx, ls_uuids,
scan_missing=scan_missing)
self._synchronize_lrouters(ctx, lr_uuids,
scan_missing=scan_missing)
self._synchronize_lswitchports(ctx, lp_uuids,
scan_missing=scan_missing)
# Increase chunk counter
LOG.info(_LI("Synchronization for chunk %(chunk_num)d of "
"%(total_chunks)d performed"),
{'chunk_num': sp.current_chunk + 1,
'total_chunks': num_chunks})
sp.current_chunk = (sp.current_chunk + 1) % num_chunks
added_delay = 0
if sp.current_chunk == 0:
# Ensure init_sync_performed is True
if not sp.init_sync_performed:
sp.init_sync_performed = True
# Add additional random delay
added_delay = random.randint(0, self._max_rand_delay)
LOG.debug("Time elapsed at end of sync: %s",
timeutils.utcnow() - start)
return self._sync_interval / num_chunks + added_delay