/usr/lib/python2.7/dist-packages/swift/common/ring/builder.py is in python-swift 2.7.0-0ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 | # Copyright (c) 2010-2012 OpenStack Foundation
#
# 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 errno
import itertools
import logging
import math
import random
import six.moves.cPickle as pickle
from copy import deepcopy
from contextlib import contextmanager
from array import array
from collections import defaultdict
import six
from six.moves import range
from time import time
from swift.common import exceptions
from swift.common.ring import RingData
from swift.common.ring.utils import tiers_for_dev, build_tier_tree, \
validate_and_normalize_address
# we can't store None's in the replica2part2dev array, so we high-jack
# the max value for magic to represent the part is not currently
# assigned to any device.
NONE_DEV = 2 ** 16 - 1
MAX_BALANCE = 999.99
MAX_BALANCE_GATHER_COUNT = 3
class RingValidationWarning(Warning):
pass
try:
# python 2.7+
from logging import NullHandler
except ImportError:
# python 2.6
class NullHandler(logging.Handler):
def emit(self, *a, **kw):
pass
class RingBuilder(object):
"""
Used to build swift.common.ring.RingData instances to be written to disk
and used with swift.common.ring.Ring instances. See bin/swift-ring-builder
for example usage.
The instance variable devs_changed indicates if the device information has
changed since the last balancing. This can be used by tools to know whether
a rebalance request is an isolated request or due to added, changed, or
removed devices.
:param part_power: number of partitions = 2**part_power.
:param replicas: number of replicas for each partition
:param min_part_hours: minimum number of hours between partition changes
"""
def __init__(self, part_power, replicas, min_part_hours):
if part_power > 32:
raise ValueError("part_power must be at most 32 (was %d)"
% (part_power,))
if replicas < 1:
raise ValueError("replicas must be at least 1 (was %.6f)"
% (replicas,))
if min_part_hours < 0:
raise ValueError("min_part_hours must be non-negative (was %d)"
% (min_part_hours,))
self.part_power = part_power
self.replicas = replicas
self.min_part_hours = min_part_hours
self.parts = 2 ** self.part_power
self.devs = []
self.devs_changed = False
self.version = 0
self.overload = 0.0
# _replica2part2dev maps from replica number to partition number to
# device id. So, for a three replica, 2**23 ring, it's an array of
# three 2**23 arrays of device ids (unsigned shorts). This can work a
# bit faster than the 2**23 array of triplet arrays of device ids in
# many circumstances. Making one big 2**23 * 3 array didn't seem to
# have any speed change; though you're welcome to try it again (it was
# a while ago, code-wise, when I last tried it).
self._replica2part2dev = None
# _last_part_moves is an array of unsigned bytes representing
# the number of hours since a given partition was last moved.
# This is used to guarantee we don't move a partition twice
# within a given number of hours (24 is my usual test). Removing
# a device overrides this behavior as it's assumed that's only
# done because of device failure.
self._last_part_moves = None
# _last_part_moves_epoch indicates the time the offsets in
# _last_part_moves is based on.
self._last_part_moves_epoch = 0
self._last_part_gather_start = 0
self._dispersion_graph = {}
self.dispersion = 0.0
self._remove_devs = []
self._ring = None
self.logger = logging.getLogger("swift.ring.builder")
if not self.logger.handlers:
self.logger.disabled = True
# silence "no handler for X" error messages
self.logger.addHandler(NullHandler())
@contextmanager
def debug(self):
"""
Temporarily enables debug logging, useful in tests, e.g.
with rb.debug():
rb.rebalance()
"""
self.logger.disabled = False
try:
yield
finally:
self.logger.disabled = True
@property
def min_part_seconds_left(self):
"""Get the total seconds until a rebalance can be performed"""
elapsed_seconds = int(time() - self._last_part_moves_epoch)
return max((self.min_part_hours * 3600) - elapsed_seconds, 0)
def weight_of_one_part(self):
"""
Returns the weight of each partition as calculated from the
total weight of all the devices.
"""
try:
return self.parts * self.replicas / \
sum(d['weight'] for d in self._iter_devs())
except ZeroDivisionError:
raise exceptions.EmptyRingError('There are no devices in this '
'ring, or all devices have been '
'deleted')
@classmethod
def from_dict(cls, builder_data):
b = cls(1, 1, 1) # Dummy values
b.copy_from(builder_data)
return b
def copy_from(self, builder):
"""
Reinitializes this RingBuilder instance from data obtained from the
builder dict given. Code example::
b = RingBuilder(1, 1, 1) # Dummy values
b.copy_from(builder)
This is to restore a RingBuilder that has had its b.to_dict()
previously saved.
"""
if hasattr(builder, 'devs'):
self.part_power = builder.part_power
self.replicas = builder.replicas
self.min_part_hours = builder.min_part_hours
self.parts = builder.parts
self.devs = builder.devs
self.devs_changed = builder.devs_changed
self.overload = builder.overload
self.version = builder.version
self._replica2part2dev = builder._replica2part2dev
self._last_part_moves_epoch = builder._last_part_moves_epoch
self._last_part_moves = builder._last_part_moves
self._last_part_gather_start = builder._last_part_gather_start
self._remove_devs = builder._remove_devs
else:
self.part_power = builder['part_power']
self.replicas = builder['replicas']
self.min_part_hours = builder['min_part_hours']
self.parts = builder['parts']
self.devs = builder['devs']
self.devs_changed = builder['devs_changed']
self.overload = builder.get('overload', 0.0)
self.version = builder['version']
self._replica2part2dev = builder['_replica2part2dev']
self._last_part_moves_epoch = builder['_last_part_moves_epoch']
self._last_part_moves = builder['_last_part_moves']
self._last_part_gather_start = builder['_last_part_gather_start']
self._dispersion_graph = builder.get('_dispersion_graph', {})
self.dispersion = builder.get('dispersion')
self._remove_devs = builder['_remove_devs']
self._ring = None
# Old builders may not have a region defined for their devices, in
# which case we default it to 1.
for dev in self._iter_devs():
dev.setdefault("region", 1)
if not self._last_part_moves_epoch:
self._last_part_moves_epoch = 0
def __deepcopy__(self, memo):
return type(self).from_dict(deepcopy(self.to_dict(), memo))
def to_dict(self):
"""
Returns a dict that can be used later with copy_from to
restore a RingBuilder. swift-ring-builder uses this to
pickle.dump the dict to a file and later load that dict into
copy_from.
"""
return {'part_power': self.part_power,
'replicas': self.replicas,
'min_part_hours': self.min_part_hours,
'parts': self.parts,
'devs': self.devs,
'devs_changed': self.devs_changed,
'version': self.version,
'overload': self.overload,
'_replica2part2dev': self._replica2part2dev,
'_last_part_moves_epoch': self._last_part_moves_epoch,
'_last_part_moves': self._last_part_moves,
'_last_part_gather_start': self._last_part_gather_start,
'_dispersion_graph': self._dispersion_graph,
'dispersion': self.dispersion,
'_remove_devs': self._remove_devs}
def change_min_part_hours(self, min_part_hours):
"""
Changes the value used to decide if a given partition can be moved
again. This restriction is to give the overall system enough time to
settle a partition to its new location before moving it to yet another
location. While no data would be lost if a partition is moved several
times quickly, it could make that data unreachable for a short period
of time.
This should be set to at least the average full partition replication
time. Starting it at 24 hours and then lowering it to what the
replicator reports as the longest partition cycle is best.
:param min_part_hours: new value for min_part_hours
"""
self.min_part_hours = min_part_hours
def set_replicas(self, new_replica_count):
"""
Changes the number of replicas in this ring.
If the new replica count is sufficiently different that
self._replica2part2dev will change size, sets
self.devs_changed. This is so tools like
bin/swift-ring-builder can know to write out the new ring
rather than bailing out due to lack of balance change.
"""
old_slots_used = int(self.parts * self.replicas)
new_slots_used = int(self.parts * new_replica_count)
if old_slots_used != new_slots_used:
self.devs_changed = True
self.replicas = new_replica_count
def set_overload(self, overload):
self.overload = overload
def get_ring(self):
"""
Get the ring, or more specifically, the swift.common.ring.RingData.
This ring data is the minimum required for use of the ring. The ring
builder itself keeps additional data such as when partitions were last
moved.
"""
# We cache the self._ring value so multiple requests for it don't build
# it multiple times. Be sure to set self._ring = None whenever the ring
# will need to be rebuilt.
if not self._ring:
# Make devs list (with holes for deleted devices) and not including
# builder-specific extra attributes.
devs = [None] * len(self.devs)
for dev in self._iter_devs():
devs[dev['id']] = dict((k, v) for k, v in dev.items()
if k not in ('parts', 'parts_wanted'))
# Copy over the replica+partition->device assignments, the device
# information, and the part_shift value (the number of bits to
# shift an unsigned int >I right to obtain the partition for the
# int).
if not self._replica2part2dev:
self._ring = RingData([], devs, 32 - self.part_power)
else:
self._ring = \
RingData([array('H', p2d) for p2d in
self._replica2part2dev],
devs, 32 - self.part_power)
return self._ring
def add_dev(self, dev):
"""
Add a device to the ring. This device dict should have a minimum of the
following keys:
====== ===============================================================
id unique integer identifier amongst devices. Defaults to the next
id if the 'id' key is not provided in the dict
weight a float of the relative weight of this device as compared to
others; this indicates how many partitions the builder will try
to assign to this device
region integer indicating which region the device is in
zone integer indicating which zone the device is in; a given
partition will not be assigned to multiple devices within the
same (region, zone) pair if there is any alternative
ip the ip address of the device
port the tcp port of the device
device the device's name on disk (sdb1, for example)
meta general use 'extra' field; for example: the online date, the
hardware description
====== ===============================================================
.. note::
This will not rebalance the ring immediately as you may want to
make multiple changes for a single rebalance.
:param dev: device dict
:returns: id of device (not used in the tree anymore, but unknown
users may depend on it)
"""
if 'id' not in dev:
dev['id'] = 0
if self.devs:
try:
dev['id'] = self.devs.index(None)
except ValueError:
dev['id'] = len(self.devs)
if dev['id'] < len(self.devs) and self.devs[dev['id']] is not None:
raise exceptions.DuplicateDeviceError(
'Duplicate device id: %d' % dev['id'])
# Add holes to self.devs to ensure self.devs[dev['id']] will be the dev
while dev['id'] >= len(self.devs):
self.devs.append(None)
dev['weight'] = float(dev['weight'])
dev['parts'] = 0
self.devs[dev['id']] = dev
self.devs_changed = True
self.version += 1
return dev['id']
def set_dev_weight(self, dev_id, weight):
"""
Set the weight of a device. This should be called rather than just
altering the weight key in the device dict directly, as the builder
will need to rebuild some internal state to reflect the change.
.. note::
This will not rebalance the ring immediately as you may want to
make multiple changes for a single rebalance.
:param dev_id: device id
:param weight: new weight for device
"""
if any(dev_id == d['id'] for d in self._remove_devs):
raise ValueError("Can not set weight of dev_id %s because it "
"is marked for removal" % (dev_id,))
self.devs[dev_id]['weight'] = weight
self.devs_changed = True
self.version += 1
def remove_dev(self, dev_id):
"""
Remove a device from the ring.
.. note::
This will not rebalance the ring immediately as you may want to
make multiple changes for a single rebalance.
:param dev_id: device id
"""
dev = self.devs[dev_id]
dev['weight'] = 0
self._remove_devs.append(dev)
self.devs_changed = True
self.version += 1
def rebalance(self, seed=None):
"""
Rebalance the ring.
This is the main work function of the builder, as it will assign and
reassign partitions to devices in the ring based on weights, distinct
zones, recent reassignments, etc.
The process doesn't always perfectly assign partitions (that'd take a
lot more analysis and therefore a lot more time -- I had code that did
that before). Because of this, it keeps rebalancing until the device
skew (number of partitions a device wants compared to what it has) gets
below 1% or doesn't change by more than 1% (only happens with ring that
can't be balanced no matter what).
:returns: (number_of_partitions_altered, resulting_balance,
number_of_removed_devices)
"""
# count up the devs, and cache some stuff
num_devices = 0
for dev in self._iter_devs():
dev['tiers'] = tiers_for_dev(dev)
if dev['weight'] > 0:
num_devices += 1
if num_devices < self.replicas:
raise exceptions.RingValidationError(
"Replica count of %(replicas)s requires more "
"than %(num_devices)s devices" % {
'replicas': self.replicas,
'num_devices': num_devices,
})
if seed is not None:
random.seed(seed)
self._ring = None
old_replica2part2dev = copy.deepcopy(self._replica2part2dev)
if self._last_part_moves is None:
self.logger.debug("New builder; performing initial balance")
self._last_part_moves = array('B', itertools.repeat(0, self.parts))
self._update_last_part_moves()
replica_plan = self._build_replica_plan()
self._set_parts_wanted(replica_plan)
assign_parts = defaultdict(list)
# gather parts from replica count adjustment
self._adjust_replica2part2dev_size(assign_parts)
# gather parts from failed devices
removed_devs = self._gather_parts_from_failed_devices(assign_parts)
# gather parts for dispersion (N.B. this only picks up parts that
# *must* disperse according to the replica plan)
self._gather_parts_for_dispersion(assign_parts, replica_plan)
# we'll gather a few times, or until we archive the plan
for gather_count in range(MAX_BALANCE_GATHER_COUNT):
self._gather_parts_for_balance(assign_parts, replica_plan)
if not assign_parts:
# most likely min part hours
finish_status = 'Unable to finish'
break
assign_parts_list = list(assign_parts.items())
# shuffle the parts to be reassigned, we have no preference on the
# order in which the replica plan is fulfilled.
random.shuffle(assign_parts_list)
# reset assign_parts map for next iteration
assign_parts = defaultdict(list)
num_part_replicas = sum(len(r) for p, r in assign_parts_list)
self.logger.debug("Gathered %d parts", num_part_replicas)
self._reassign_parts(assign_parts_list, replica_plan)
self.logger.debug("Assigned %d parts", num_part_replicas)
if not sum(d['parts_wanted'] < 0 for d in
self._iter_devs()):
finish_status = 'Finished'
break
else:
finish_status = 'Unable to finish'
self.logger.debug('%s rebalance plan after %s attempts' % (
finish_status, gather_count + 1))
self.devs_changed = False
self.version += 1
changed_parts = self._build_dispersion_graph(old_replica2part2dev)
# clean up the cache
for dev in self._iter_devs():
dev.pop('tiers', None)
return changed_parts, self.get_balance(), removed_devs
def _build_dispersion_graph(self, old_replica2part2dev=None):
"""
Build a dict of all tiers in the cluster to a list of the number of
parts with a replica count at each index. The values of the dict will
be lists of length the maximum whole replica + 1 so that the
graph[tier][3] is the number of parts with in the tier with 3 replicas
and graph [tier][0] is the number of parts not assigned in this tier.
i.e.
{
<tier>: [
<number_of_parts_with_0_replicas>,
<number_of_parts_with_1_replicas>,
...
<number_of_parts_with_n_replicas>,
],
...
}
:param old_replica2part2dev: if called from rebalance, the
old_replica2part2dev can be used to count moved moved parts.
:returns: number of parts with different assignments than
old_replica2part2dev if provided
"""
# Since we're going to loop over every replica of every part we'll
# also count up changed_parts if old_replica2part2dev is passed in
old_replica2part2dev = old_replica2part2dev or []
# Compare the partition allocation before and after the rebalance
# Only changed device ids are taken into account; devices might be
# "touched" during the rebalance, but actually not really moved
changed_parts = 0
int_replicas = int(math.ceil(self.replicas))
max_allowed_replicas = self._build_max_replicas_by_tier()
parts_at_risk = 0
dispersion_graph = {}
# go over all the devices holding each replica part by part
for part_id, dev_ids in enumerate(
six.moves.zip(*self._replica2part2dev)):
# count the number of replicas of this part for each tier of each
# device, some devices may have overlapping tiers!
replicas_at_tier = defaultdict(int)
for rep_id, dev in enumerate(iter(
self.devs[dev_id] for dev_id in dev_ids)):
for tier in (dev.get('tiers') or tiers_for_dev(dev)):
replicas_at_tier[tier] += 1
# IndexErrors will be raised if the replicas are increased or
# decreased, and that actually means the partition has changed
try:
old_device = old_replica2part2dev[rep_id][part_id]
except IndexError:
changed_parts += 1
continue
if old_device != dev['id']:
changed_parts += 1
part_at_risk = False
# update running totals for each tiers' number of parts with a
# given replica count
for tier, replicas in replicas_at_tier.items():
if tier not in dispersion_graph:
dispersion_graph[tier] = [self.parts] + [0] * int_replicas
dispersion_graph[tier][0] -= 1
dispersion_graph[tier][replicas] += 1
if replicas > max_allowed_replicas[tier]:
part_at_risk = True
# this part may be at risk in multiple tiers, but we only count it
# as at_risk once
if part_at_risk:
parts_at_risk += 1
self._dispersion_graph = dispersion_graph
self.dispersion = 100.0 * parts_at_risk / self.parts
return changed_parts
def validate(self, stats=False):
"""
Validate the ring.
This is a safety function to try to catch any bugs in the building
process. It ensures partitions have been assigned to real devices,
aren't doubly assigned, etc. It can also optionally check the even
distribution of partitions across devices.
:param stats: if True, check distribution of partitions across devices
:returns: if stats is True, a tuple of (device_usage, worst_stat), else
(None, None). device_usage[dev_id] will equal the number of
partitions assigned to that device. worst_stat will equal the
number of partitions the worst device is skewed from the
number it should have.
:raises RingValidationError: problem was found with the ring.
"""
# "len" showed up in profiling, so it's just computed once.
dev_len = len(self.devs)
parts_on_devs = sum(d['parts'] for d in self._iter_devs())
if not self._replica2part2dev:
raise exceptions.RingValidationError(
'_replica2part2dev empty; did you forget to rebalance?')
parts_in_map = sum(len(p2d) for p2d in self._replica2part2dev)
if parts_on_devs != parts_in_map:
raise exceptions.RingValidationError(
'All partitions are not double accounted for: %d != %d' %
(parts_on_devs, parts_in_map))
if stats:
# dev_usage[dev_id] will equal the number of partitions assigned to
# that device.
dev_usage = array('I', (0 for _junk in range(dev_len)))
for part2dev in self._replica2part2dev:
for dev_id in part2dev:
dev_usage[dev_id] += 1
for dev in self._iter_devs():
if not isinstance(dev['port'], int):
raise exceptions.RingValidationError(
"Device %d has port %r, which is not an integer." %
(dev['id'], dev['port']))
int_replicas = int(math.ceil(self.replicas))
rep2part_len = map(len, self._replica2part2dev)
# check the assignments of each part's replicas
for part in range(self.parts):
devs_for_part = []
for replica, part_len in enumerate(rep2part_len):
if part_len <= part:
# last replica may be short on parts because of floating
# replica count
if replica + 1 < int_replicas:
raise exceptions.RingValidationError(
"The partition assignments of replica %r were "
"shorter than expected (%s < %s) - this should "
"only happen for the last replica" % (
replica,
len(self._replica2part2dev[replica]),
self.parts,
))
break
dev_id = self._replica2part2dev[replica][part]
if dev_id >= dev_len or not self.devs[dev_id]:
raise exceptions.RingValidationError(
"Partition %d, replica %d was not allocated "
"to a device." %
(part, replica))
devs_for_part.append(dev_id)
if len(devs_for_part) != len(set(devs_for_part)):
raise exceptions.RingValidationError(
"The partition %s has been assigned to "
"duplicate devices %r" % (
part, devs_for_part))
if stats:
weight_of_one_part = self.weight_of_one_part()
worst = 0
for dev in self._iter_devs():
if not dev['weight']:
if dev_usage[dev['id']]:
# If a device has no weight, but has partitions, then
# its overage is considered "infinity" and therefore
# always the worst possible. We show MAX_BALANCE for
# convenience.
worst = MAX_BALANCE
break
continue
skew = abs(100.0 * dev_usage[dev['id']] /
(dev['weight'] * weight_of_one_part) - 100.0)
if skew > worst:
worst = skew
return dev_usage, worst
return None, None
def _build_balance_per_dev(self):
"""
Build a map of <device_id> => <balance> where <balance> is a float
representing the percentage difference from the desired amount of
partitions a given device wants and the amount it has.
N.B. this method only considers a device's weight and the parts
assigned, not the parts wanted according to the replica plan.
"""
weight_of_one_part = self.weight_of_one_part()
balance_per_dev = {}
for dev in self._iter_devs():
if not dev['weight']:
if dev['parts']:
# If a device has no weight, but has partitions, then its
# overage is considered "infinity" and therefore always the
# worst possible. We show MAX_BALANCE for convenience.
balance = MAX_BALANCE
else:
balance = 0
else:
balance = 100.0 * dev['parts'] / (
dev['weight'] * weight_of_one_part) - 100.0
balance_per_dev[dev['id']] = balance
return balance_per_dev
def get_balance(self):
"""
Get the balance of the ring. The balance value is the highest
percentage off the desired amount of partitions a given device
wants. For instance, if the "worst" device wants (based on its
weight relative to the sum of all the devices' weights) 123
partitions and it has 124 partitions, the balance value would
be 0.83 (1 extra / 123 wanted * 100 for percentage).
:returns: balance of the ring
"""
balance_per_dev = self._build_balance_per_dev()
return max(abs(b) for b in balance_per_dev.values())
def get_required_overload(self, weighted=None, wanted=None):
"""
Returns the minimum overload value required to make the ring maximally
dispersed.
The required overload is the largest percentage change of any single
device from its weighted replicanth to its wanted replicanth (note
under weighted devices have a negative percentage change) to archive
dispersion - that is to say a single device that must be overloaded by
5% is worse than 5 devices in a single tier overloaded by 1%.
"""
weighted = weighted or self._build_weighted_replicas_by_tier()
wanted = wanted or self._build_wanted_replicas_by_tier()
max_overload = 0.0
for dev in self._iter_devs():
tier = (dev['region'], dev['zone'], dev['ip'], dev['id'])
if not dev['weight']:
if tier not in wanted or not wanted[tier]:
continue
raise exceptions.RingValidationError(
'Device %s has zero weight and '
'should not want any replicas' % (tier,))
required = (wanted[tier] - weighted[tier]) / weighted[tier]
self.logger.debug('%s wants %s and is weighted for %s so '
'therefore requires %s overload' % (
tier, wanted[tier], weighted[tier],
required))
if required > max_overload:
max_overload = required
return max_overload
def pretend_min_part_hours_passed(self):
"""
Override min_part_hours by marking all partitions as having been moved
255 hours ago and last move epoch to 'the beginning of time'. This can
be used to force a full rebalance on the next call to rebalance.
"""
for part in range(self.parts):
self._last_part_moves[part] = 0xff
self._last_part_moves_epoch = 0
def get_part_devices(self, part):
"""
Get the devices that are responsible for the partition,
filtering out duplicates.
:param part: partition to get devices for
:returns: list of device dicts
"""
devices = []
for dev in self._devs_for_part(part):
if dev not in devices:
devices.append(dev)
return devices
def _iter_devs(self):
"""
Returns an iterator all the non-None devices in the ring. Note that
this means list(b._iter_devs())[some_id] may not equal b.devs[some_id];
you will have to check the 'id' key of each device to obtain its
dev_id.
"""
for dev in self.devs:
if dev is not None:
yield dev
def _build_tier2children(self):
"""
Wrap helper build_tier_tree so exclude zero-weight devices.
"""
return build_tier_tree(d for d in self._iter_devs() if d['weight'])
def _set_parts_wanted(self, replica_plan):
"""
Sets the parts_wanted key for each of the devices to the number of
partitions the device wants based on its relative weight. This key is
used to sort the devices according to "most wanted" during rebalancing
to best distribute partitions. A negative parts_wanted indicates the
device is "overweight" and wishes to give partitions away if possible.
:param replica_plan: a dict of dicts, as returned from
_build_replica_plan, that that maps
each tier to it's target replicanths.
"""
tier2children = self._build_tier2children()
parts_by_tier = defaultdict(int)
def place_parts(tier, parts):
parts_by_tier[tier] = parts
sub_tiers = sorted(tier2children[tier])
if not sub_tiers:
return
to_place = defaultdict(int)
for t in sub_tiers:
to_place[t] = int(math.floor(
replica_plan[t]['target'] * self.parts))
parts -= to_place[t]
# if there's some parts left over, just throw 'em about
sub_tier_gen = itertools.cycle(sorted(
sub_tiers, key=lambda t: replica_plan[t]['target']))
while parts:
t = next(sub_tier_gen)
to_place[t] += 1
parts -= 1
for t, p in to_place.items():
place_parts(t, p)
total_parts = int(self.replicas * self.parts)
place_parts((), total_parts)
# belts & suspenders/paranoia - at every level, the sum of
# parts_by_tier should be total_parts for the ring
tiers = ['cluster', 'regions', 'zones', 'servers', 'devices']
for i, tier_name in enumerate(tiers):
parts_at_tier = sum(parts_by_tier[t] for t in parts_by_tier
if len(t) == i)
if parts_at_tier != total_parts:
raise exceptions.RingValidationError(
'%s != %s at tier %s' % (
parts_at_tier, total_parts, tier_name))
for dev in self._iter_devs():
if not dev['weight']:
# With no weight, that means we wish to "drain" the device. So
# we set the parts_wanted to a really large negative number to
# indicate its strong desire to give up everything it has.
dev['parts_wanted'] = -self.parts * self.replicas
else:
tier = (dev['region'], dev['zone'], dev['ip'], dev['id'])
dev['parts_wanted'] = parts_by_tier[tier] - dev['parts']
def _update_last_part_moves(self):
"""
Updates how many hours ago each partition was moved based on the
current time. The builder won't move a partition that has been moved
more recently than min_part_hours.
"""
elapsed_hours = int(time() - self._last_part_moves_epoch) / 3600
if elapsed_hours <= 0:
return
for part in range(self.parts):
# The "min(self._last_part_moves[part] + elapsed_hours, 0xff)"
# which was here showed up in profiling, so it got inlined.
last_plus_elapsed = self._last_part_moves[part] + elapsed_hours
if last_plus_elapsed < 0xff:
self._last_part_moves[part] = last_plus_elapsed
else:
self._last_part_moves[part] = 0xff
self._last_part_moves_epoch = int(time())
def _gather_parts_from_failed_devices(self, assign_parts):
"""
Update the map of partition => [replicas] to be reassigned from
removed devices.
"""
# First we gather partitions from removed devices. Since removed
# devices usually indicate device failures, we have no choice but to
# reassign these partitions. However, we mark them as moved so later
# choices will skip other replicas of the same partition if possible.
if self._remove_devs:
dev_ids = [d['id'] for d in self._remove_devs if d['parts']]
if dev_ids:
for part, replica in self._each_part_replica():
dev_id = self._replica2part2dev[replica][part]
if dev_id in dev_ids:
self._replica2part2dev[replica][part] = NONE_DEV
self._last_part_moves[part] = 0
assign_parts[part].append(replica)
self.logger.debug(
"Gathered %d/%d from dev %d [dev removed]",
part, replica, dev_id)
removed_devs = 0
while self._remove_devs:
remove_dev_id = self._remove_devs.pop()['id']
self.logger.debug("Removing dev %d", remove_dev_id)
self.devs[remove_dev_id] = None
removed_devs += 1
return removed_devs
def _adjust_replica2part2dev_size(self, to_assign):
"""
Make sure that the lengths of the arrays in _replica2part2dev
are correct for the current value of self.replicas.
Example:
self.part_power = 8
self.replicas = 2.25
self._replica2part2dev will contain 3 arrays: the first 2 of
length 256 (2**8), and the last of length 64 (0.25 * 2**8).
Update the mapping of partition => [replicas] that need assignment.
"""
fractional_replicas, whole_replicas = math.modf(self.replicas)
whole_replicas = int(whole_replicas)
removed_parts = 0
new_parts = 0
desired_lengths = [self.parts] * whole_replicas
if fractional_replicas:
desired_lengths.append(int(self.parts * fractional_replicas))
if self._replica2part2dev is not None:
# If we crossed an integer threshold (say, 4.1 --> 4),
# we'll have a partial extra replica clinging on here. Clean
# up any such extra stuff.
for part2dev in self._replica2part2dev[len(desired_lengths):]:
for dev_id in part2dev:
dev_losing_part = self.devs[dev_id]
dev_losing_part['parts'] -= 1
removed_parts -= 1
self._replica2part2dev = \
self._replica2part2dev[:len(desired_lengths)]
else:
self._replica2part2dev = []
for replica, desired_length in enumerate(desired_lengths):
if replica < len(self._replica2part2dev):
part2dev = self._replica2part2dev[replica]
if len(part2dev) < desired_length:
# Not long enough: needs to be extended and the
# newly-added pieces assigned to devices.
for part in range(len(part2dev), desired_length):
to_assign[part].append(replica)
part2dev.append(NONE_DEV)
new_parts += 1
elif len(part2dev) > desired_length:
# Too long: truncate this mapping.
for part in range(desired_length, len(part2dev)):
dev_losing_part = self.devs[part2dev[part]]
dev_losing_part['parts'] -= 1
removed_parts -= 1
self._replica2part2dev[replica] = part2dev[:desired_length]
else:
# Mapping not present at all: make one up and assign
# all of it.
for part in range(desired_length):
to_assign[part].append(replica)
new_parts += 1
self._replica2part2dev.append(
array('H', itertools.repeat(NONE_DEV, desired_length)))
self.logger.debug(
"%d new parts and %d removed parts from replica-count change",
new_parts, removed_parts)
def _gather_parts_for_dispersion(self, assign_parts, replica_plan):
"""
Update the map of partition => [replicas] to be reassigned from
insufficiently-far-apart replicas.
"""
# Now we gather partitions that are "at risk" because they aren't
# currently sufficient spread out across the cluster.
for part in range(self.parts):
if self._last_part_moves[part] < self.min_part_hours:
continue
# First, add up the count of replicas at each tier for each
# partition.
replicas_at_tier = defaultdict(int)
for dev in self._devs_for_part(part):
for tier in dev['tiers']:
replicas_at_tier[tier] += 1
# Now, look for partitions not yet spread out enough.
undispersed_dev_replicas = []
for replica in self._replicas_for_part(part):
dev_id = self._replica2part2dev[replica][part]
if dev_id == NONE_DEV:
continue
dev = self.devs[dev_id]
if all(replicas_at_tier[tier] <=
replica_plan[tier]['max']
for tier in dev['tiers']):
continue
undispersed_dev_replicas.append((dev, replica))
if not undispersed_dev_replicas:
continue
undispersed_dev_replicas.sort(
key=lambda dr: dr[0]['parts_wanted'])
for dev, replica in undispersed_dev_replicas:
# the min part hour check is ignored iff a device has more
# than one replica of a part assigned to it - which would have
# only been possible on rings built with older version of code
if (self._last_part_moves[part] < self.min_part_hours and
not replicas_at_tier[dev['tiers'][-1]] > 1):
continue
dev['parts_wanted'] += 1
dev['parts'] -= 1
assign_parts[part].append(replica)
self.logger.debug(
"Gathered %d/%d from dev %d [dispersion]",
part, replica, dev['id'])
self._replica2part2dev[replica][part] = NONE_DEV
for tier in dev['tiers']:
replicas_at_tier[tier] -= 1
self._last_part_moves[part] = 0
def _gather_parts_for_balance_can_disperse(self, assign_parts, start,
replica_plan):
"""
Update the map of partition => [replicas] to be reassigned from
overweight drives where the replicas can be better dispersed to
another failure domain.
:param assign_parts: the map of partition => [replica] to update
:param start: offset into self.parts to begin search
:param replica_plan: replicanth targets for tiers
"""
# Last, we gather partitions from devices that are "overweight" because
# they have more partitions than their parts_wanted.
for offset in range(self.parts):
part = (start + offset) % self.parts
if self._last_part_moves[part] < self.min_part_hours:
continue
# For each part we'll look at the devices holding those parts and
# see if any are overweight, keeping track of replicas_at_tier as
# we go
overweight_dev_replica = []
replicas_at_tier = defaultdict(int)
for replica in self._replicas_for_part(part):
dev_id = self._replica2part2dev[replica][part]
if dev_id == NONE_DEV:
continue
dev = self.devs[dev_id]
for tier in dev['tiers']:
replicas_at_tier[tier] += 1
if dev['parts_wanted'] < 0:
overweight_dev_replica.append((dev, replica))
if not overweight_dev_replica:
continue
overweight_dev_replica.sort(
key=lambda dr: dr[0]['parts_wanted'])
for dev, replica in overweight_dev_replica:
if self._last_part_moves[part] < self.min_part_hours:
break
if any(replica_plan[tier]['min'] <=
replicas_at_tier[tier] <
replica_plan[tier]['max']
for tier in dev['tiers']):
continue
# this is the most overweight_device holding a replica
# of this part that can shed it according to the plan
dev['parts_wanted'] += 1
dev['parts'] -= 1
assign_parts[part].append(replica)
self.logger.debug(
"Gathered %d/%d from dev %d [weight disperse]",
part, replica, dev['id'])
self._replica2part2dev[replica][part] = NONE_DEV
for tier in dev['tiers']:
replicas_at_tier[tier] -= 1
self._last_part_moves[part] = 0
def _gather_parts_for_balance(self, assign_parts, replica_plan):
"""
Gather parts that look like they should move for balance reasons.
A simple gather of parts that looks dispersible normally works out,
we'll switch strategies if things don't be seem to moving...
"""
# pick a random starting point on the other side of the ring
quarter_turn = (self.parts // 4)
random_half = random.randint(0, self.parts / 2)
start = (self._last_part_gather_start + quarter_turn +
random_half) % self.parts
self.logger.debug('Gather start is %s '
'(Last start was %s)' % (
start, self._last_part_gather_start))
self._last_part_gather_start = start
self._gather_parts_for_balance_can_disperse(
assign_parts, start, replica_plan)
if not assign_parts:
self._gather_parts_for_balance_forced(assign_parts, start)
def _gather_parts_for_balance_forced(self, assign_parts, start, **kwargs):
"""
Update the map of partition => [replicas] to be reassigned from
overweight drives without restriction, parts gathered from this method
may be placed back onto devices that are no better (or worse) than the
device from which they are gathered.
This method allows devices to flop around enough to unlock replicas
that would have otherwise potentially been locked because of
dispersion - it should be used as a last resort.
:param assign_parts: the map of partition => [replica] to update
:param start: offset into self.parts to begin search
"""
for offset in range(self.parts):
part = (start + offset) % self.parts
if self._last_part_moves[part] < self.min_part_hours:
continue
overweight_dev_replica = []
for replica in self._replicas_for_part(part):
dev_id = self._replica2part2dev[replica][part]
if dev_id == NONE_DEV:
continue
dev = self.devs[dev_id]
if dev['parts_wanted'] < 0:
overweight_dev_replica.append((dev, replica))
if not overweight_dev_replica:
continue
overweight_dev_replica.sort(
key=lambda dr: dr[0]['parts_wanted'])
for dev, replica in overweight_dev_replica:
if self._last_part_moves[part] < self.min_part_hours:
break
# this is the most overweight_device holding a replica of this
# part we don't know where it's going to end up - but we'll
# pick it up and hope for the best.
dev['parts_wanted'] += 1
dev['parts'] -= 1
assign_parts[part].append(replica)
self.logger.debug(
"Gathered %d/%d from dev %d [weight forced]",
part, replica, dev['id'])
self._replica2part2dev[replica][part] = NONE_DEV
self._last_part_moves[part] = 0
def _reassign_parts(self, reassign_parts, replica_plan):
"""
For an existing ring data set, partitions are reassigned similarly to
the initial assignment.
The devices are ordered by how many partitions they still want and
kept in that order throughout the process.
The gathered partitions are iterated through, assigning them to
devices according to the "most wanted" while keeping the replicas as
"far apart" as possible.
Two different regions are considered the farthest-apart things,
followed by zones, then different ip within a zone; the
least-far-apart things are different devices with the same ip in the
same zone.
:param reassign_parts: An iterable of (part, replicas_to_replace)
pairs. replicas_to_replace is an iterable of the
replica (an int) to replace for that partition.
replicas_to_replace may be shared for multiple
partitions, so be sure you do not modify it.
"""
parts_available_in_tier = defaultdict(int)
for dev in self._iter_devs():
dev['sort_key'] = self._sort_key_for(dev)
# Note: this represents how many partitions may be assigned to a
# given tier (region/zone/server/disk). It does not take into
# account how many partitions a given tier wants to shed.
#
# If we did not do this, we could have a zone where, at some
# point during assignment, number-of-parts-to-gain equals
# number-of-parts-to-shed. At that point, no further placement
# into that zone would occur since its parts_available_in_tier
# would be 0. This would happen any time a zone had any device
# with partitions to shed, which is any time a device is being
# removed, which is a pretty frequent operation.
wanted = max(dev['parts_wanted'], 0)
for tier in dev['tiers']:
parts_available_in_tier[tier] += wanted
available_devs = \
sorted((d for d in self._iter_devs() if d['weight']),
key=lambda x: x['sort_key'])
tier2devs = defaultdict(list)
tier2sort_key = defaultdict(tuple)
tier2dev_sort_key = defaultdict(list)
max_tier_depth = 0
for dev in available_devs:
for tier in dev['tiers']:
tier2devs[tier].append(dev) # <-- starts out sorted!
tier2dev_sort_key[tier].append(dev['sort_key'])
tier2sort_key[tier] = dev['sort_key']
if len(tier) > max_tier_depth:
max_tier_depth = len(tier)
tier2children_sets = build_tier_tree(available_devs)
tier2children = defaultdict(list)
tier2children_sort_key = {}
tiers_list = [()]
depth = 1
while depth <= max_tier_depth:
new_tiers_list = []
for tier in tiers_list:
child_tiers = list(tier2children_sets[tier])
child_tiers.sort(key=tier2sort_key.__getitem__)
tier2children[tier] = child_tiers
tier2children_sort_key[tier] = map(
tier2sort_key.__getitem__, child_tiers)
new_tiers_list.extend(child_tiers)
tiers_list = new_tiers_list
depth += 1
for part, replace_replicas in reassign_parts:
# always update part_moves for min_part_hours
self._last_part_moves[part] = 0
# count up where these replicas be
replicas_at_tier = defaultdict(int)
for dev in self._devs_for_part(part):
for tier in dev['tiers']:
replicas_at_tier[tier] += 1
for replica in replace_replicas:
# Find a new home for this replica
tier = ()
# This used to be a cute, recursive function, but it's been
# unrolled for performance.
depth = 1
while depth <= max_tier_depth:
# Choose the roomiest tier among those that don't
# already have their max replicas assigned according
# to the replica_plan.
candidates = [t for t in tier2children[tier] if
replicas_at_tier[t] <
replica_plan[t]['max']]
if not candidates:
raise Exception('no home for %s/%s %s' % (
part, replica, {t: (
replicas_at_tier[t],
replica_plan[t]['max'],
) for t in tier2children[tier]}))
tier = max(candidates, key=lambda t:
parts_available_in_tier[t])
depth += 1
dev = tier2devs[tier][-1]
dev['parts_wanted'] -= 1
dev['parts'] += 1
for tier in dev['tiers']:
parts_available_in_tier[tier] -= 1
replicas_at_tier[tier] += 1
self._replica2part2dev[replica][part] = dev['id']
self.logger.debug(
"Placed %d/%d onto dev %d", part, replica, dev['id'])
# Just to save memory and keep from accidental reuse.
for dev in self._iter_devs():
del dev['sort_key']
@staticmethod
def _sort_key_for(dev):
return (dev['parts_wanted'], random.randint(0, 0xFFFF), dev['id'])
def _build_max_replicas_by_tier(self, bound=math.ceil):
"""
Returns a defaultdict of (tier: replica_count) for all tiers in the
ring excluding zero weight devices.
There will always be a () entry as the root of the structure, whose
replica_count will equal the ring's replica_count.
Then there will be (region,) entries for each region, indicating the
maximum number of replicas the region might have for any given
partition.
Next there will be (region, zone) entries for each zone, indicating
the maximum number of replicas in a given region and zone. Anything
greater than 1 indicates a partition at slightly elevated risk, as if
that zone were to fail multiple replicas of that partition would be
unreachable.
Next there will be (region, zone, ip_port) entries for each node,
indicating the maximum number of replicas stored on a node in a given
region and zone. Anything greater than 1 indicates a partition at
elevated risk, as if that ip_port were to fail multiple replicas of
that partition would be unreachable.
Last there will be (region, zone, ip_port, device) entries for each
device, indicating the maximum number of replicas the device shares
with other devices on the same node for any given partition.
Anything greater than 1 indicates a partition at serious risk, as the
data on that partition will not be stored distinctly at the ring's
replica_count.
Example return dict for the common SAIO setup::
{(): 3.0,
(1,): 3.0,
(1, 1): 1.0,
(1, 1, '127.0.0.1:6010'): 1.0,
(1, 1, '127.0.0.1:6010', 0): 1.0,
(1, 2): 1.0,
(1, 2, '127.0.0.1:6020'): 1.0,
(1, 2, '127.0.0.1:6020', 1): 1.0,
(1, 3): 1.0,
(1, 3, '127.0.0.1:6030'): 1.0,
(1, 3, '127.0.0.1:6030', 2): 1.0,
(1, 4): 1.0,
(1, 4, '127.0.0.1:6040'): 1.0,
(1, 4, '127.0.0.1:6040', 3): 1.0}
"""
# Used by walk_tree to know what entries to create for each recursive
# call.
tier2children = self._build_tier2children()
def walk_tree(tier, replica_count):
if len(tier) == 4:
# special case for device, it's not recursive
replica_count = min(1, replica_count)
mr = {tier: replica_count}
if tier in tier2children:
subtiers = tier2children[tier]
for subtier in subtiers:
submax = bound(float(replica_count) / len(subtiers))
mr.update(walk_tree(subtier, submax))
return mr
mr = defaultdict(float)
mr.update(walk_tree((), self.replicas))
return mr
def _build_weighted_replicas_by_tier(self):
"""
Returns a dict mapping <tier> => replicanths for all tiers in
the ring based on their weights.
"""
weight_of_one_part = self.weight_of_one_part()
# assign each device some replicanths by weight (can't be > 1)
weighted_replicas_for_dev = {}
devices_with_room = []
for dev in self._iter_devs():
if not dev['weight']:
continue
weighted_replicas = (
dev['weight'] * weight_of_one_part / self.parts)
if weighted_replicas < 1:
devices_with_room.append(dev['id'])
else:
weighted_replicas = 1
weighted_replicas_for_dev[dev['id']] = weighted_replicas
while True:
remaining = self.replicas - sum(weighted_replicas_for_dev.values())
if remaining < 1e-10:
break
devices_with_room = [d for d in devices_with_room if
weighted_replicas_for_dev[d] < 1]
rel_weight = remaining / sum(
weighted_replicas_for_dev[d] for d in devices_with_room)
for d in devices_with_room:
weighted_replicas_for_dev[d] = min(
1, weighted_replicas_for_dev[d] * (rel_weight + 1))
weighted_replicas_by_tier = defaultdict(float)
for dev in self._iter_devs():
if not dev['weight']:
continue
assigned_replicanths = weighted_replicas_for_dev[dev['id']]
dev_tier = (dev['region'], dev['zone'], dev['ip'], dev['id'])
for i in range(len(dev_tier) + 1):
tier = dev_tier[:i]
weighted_replicas_by_tier[tier] += assigned_replicanths
# belts & suspenders/paranoia - at every level, the sum of
# weighted_replicas should be very close to the total number of
# replicas for the ring
tiers = ['cluster', 'regions', 'zones', 'servers', 'devices']
for i, tier_name in enumerate(tiers):
replicas_at_tier = sum(weighted_replicas_by_tier[t] for t in
weighted_replicas_by_tier if len(t) == i)
if abs(self.replicas - replicas_at_tier) > 1e-10:
raise exceptions.RingValidationError(
'%s != %s at tier %s' % (
replicas_at_tier, self.replicas, tier_name))
return weighted_replicas_by_tier
def _build_wanted_replicas_by_tier(self):
"""
Returns a defaultdict of (tier: replicanths) for all tiers in the ring
based on unique-as-possible (full dispersion) with respect to their
weights and device counts.
N.B. _build_max_replicas_by_tier calculates the upper bound on the
replicanths each tier may hold irrespective of the weights of the
tier; this method will calculate the minimum replicanth <=
max_replicas[tier] that will still solve dispersion. However it is
not guaranteed to return a fully dispersed solution if failure domains
are over-weighted for their device count.
"""
weighted_replicas = self._build_weighted_replicas_by_tier()
dispersed_replicas = {
t: {
'min': math.floor(r),
'max': math.ceil(r),
} for (t, r) in
self._build_max_replicas_by_tier(bound=float).items()
}
# watch out for device limited tiers
num_devices = defaultdict(int)
for d in self._iter_devs():
if d['weight'] <= 0:
continue
for t in (d.get('tiers') or tiers_for_dev(d)):
num_devices[t] += 1
num_devices[()] += 1
tier2children = self._build_tier2children()
wanted_replicas = defaultdict(float)
def place_replicas(tier, replicanths):
if replicanths > num_devices[tier]:
raise exceptions.RingValidationError(
'More than replicanths (%s) than devices (%s) '
'in tier (%s)' % (replicanths, num_devices[tier], tier))
wanted_replicas[tier] = replicanths
sub_tiers = sorted(tier2children[tier])
if not sub_tiers:
return
to_place = defaultdict(float)
remaining = replicanths
tiers_to_spread = sub_tiers
device_limited = False
while True:
rel_weight = remaining / sum(weighted_replicas[t]
for t in tiers_to_spread)
for t in tiers_to_spread:
replicas = to_place[t] + (
weighted_replicas[t] * rel_weight)
if replicas < dispersed_replicas[t]['min']:
replicas = dispersed_replicas[t]['min']
elif (replicas > dispersed_replicas[t]['max'] and
not device_limited):
replicas = dispersed_replicas[t]['max']
if replicas > num_devices[t]:
replicas = num_devices[t]
to_place[t] = replicas
remaining = replicanths - sum(to_place.values())
if remaining < -1e-10:
tiers_to_spread = [
t for t in sub_tiers
if to_place[t] > dispersed_replicas[t]['min']
]
elif remaining > 1e-10:
tiers_to_spread = [
t for t in sub_tiers
if (num_devices[t] > to_place[t] <
dispersed_replicas[t]['max'])
]
if not tiers_to_spread:
device_limited = True
tiers_to_spread = [
t for t in sub_tiers
if to_place[t] < num_devices[t]
]
else:
# remaining is "empty"
break
for t in sub_tiers:
self.logger.debug('Planning %s on %s',
to_place[t], t)
place_replicas(t, to_place[t])
# place all replicas in the cluster tier
place_replicas((), self.replicas)
# belts & suspenders/paranoia - at every level, the sum of
# wanted_replicas should be very close to the total number of
# replicas for the ring
tiers = ['cluster', 'regions', 'zones', 'servers', 'devices']
for i, tier_name in enumerate(tiers):
replicas_at_tier = sum(wanted_replicas[t] for t in
wanted_replicas if len(t) == i)
if abs(self.replicas - replicas_at_tier) > 1e-10:
raise exceptions.RingValidationError(
'%s != %s at tier %s' % (
replicas_at_tier, self.replicas, tier_name))
return wanted_replicas
def _build_target_replicas_by_tier(self):
"""
Build a map of <tier> => <target_replicas> accounting for device
weights, unique-as-possible dispersion and overload.
<tier> - a tuple, describing each tier in the ring topology
<target_replicas> - a float, the target replicanths at the tier
"""
weighted_replicas = self._build_weighted_replicas_by_tier()
wanted_replicas = self._build_wanted_replicas_by_tier()
max_overload = self.get_required_overload(weighted=weighted_replicas,
wanted=wanted_replicas)
if max_overload <= 0.0:
return wanted_replicas
else:
overload = min(self.overload, max_overload)
self.logger.debug("Using effective overload of %f", overload)
target_replicas = defaultdict(float)
for tier, weighted in weighted_replicas.items():
m = (wanted_replicas[tier] - weighted) / max_overload
target_replicas[tier] = m * overload + weighted
# belts & suspenders/paranoia - at every level, the sum of
# target_replicas should be very close to the total number
# of replicas for the ring
tiers = ['cluster', 'regions', 'zones', 'servers', 'devices']
for i, tier_name in enumerate(tiers):
replicas_at_tier = sum(target_replicas[t] for t in
target_replicas if len(t) == i)
if abs(self.replicas - replicas_at_tier) > 1e-10:
raise exceptions.RingValidationError(
'%s != %s at tier %s' % (
replicas_at_tier, self.replicas, tier_name))
return target_replicas
def _build_replica_plan(self):
"""
Wraps return value of _build_target_replicas_by_tier to include
pre-calculated min and max values for each tier.
:returns: a dict, mapping <tier> => <replica_plan>, where
<replica_plan> is itself a dict
<replica_plan> include at least the following keys:
min - the minimum number of replicas at the tier
target - the target replicanths at the tier
max - the maximum number of replicas at the tier
"""
# replica part-y planner!
target_replicas = self._build_target_replicas_by_tier()
replica_plan = defaultdict(
lambda: {'min': 0, 'target': 0, 'max': 0})
replica_plan.update({
t: {
'min': math.floor(r + 1e-10),
'target': r,
'max': math.ceil(r - 1e-10),
} for (t, r) in
target_replicas.items()
})
return replica_plan
def _devs_for_part(self, part):
"""
Returns a list of devices for a specified partition.
Deliberately includes duplicates.
"""
if self._replica2part2dev is None:
return []
devs = []
for part2dev in self._replica2part2dev:
if part >= len(part2dev):
continue
dev_id = part2dev[part]
if dev_id == NONE_DEV:
continue
devs.append(self.devs[dev_id])
return devs
def _replicas_for_part(self, part):
"""
Returns a list of replicas for a specified partition.
These can be used as indices into self._replica2part2dev
without worrying about IndexErrors.
"""
return [replica for replica, part2dev
in enumerate(self._replica2part2dev)
if part < len(part2dev)]
def _each_part_replica(self):
"""
Generator yielding every (partition, replica) pair in the ring.
"""
for replica, part2dev in enumerate(self._replica2part2dev):
for part in range(len(part2dev)):
yield (part, replica)
@classmethod
def load(cls, builder_file, open=open):
"""
Obtain RingBuilder instance of the provided builder file
:param builder_file: path to builder file to load
:return: RingBuilder instance
"""
try:
fp = open(builder_file, 'rb')
except IOError as e:
if e.errno == errno.ENOENT:
raise exceptions.FileNotFoundError(
'Ring Builder file does not exist: %s' % builder_file)
elif e.errno in [errno.EPERM, errno.EACCES]:
raise exceptions.PermissionError(
'Ring Builder file cannot be accessed: %s' % builder_file)
else:
raise
else:
with fp:
try:
builder = pickle.load(fp)
except Exception:
# raise error during unpickling as UnPicklingError
raise exceptions.UnPicklingError(
'Ring Builder file is invalid: %s' % builder_file)
if not hasattr(builder, 'devs'):
builder_dict = builder
builder = RingBuilder(1, 1, 1)
builder.copy_from(builder_dict)
for dev in builder.devs:
# really old rings didn't have meta keys
if dev and 'meta' not in dev:
dev['meta'] = ''
# NOTE(akscram): An old ring builder file don't contain
# replication parameters.
if dev:
if 'ip' in dev:
dev.setdefault('replication_ip', dev['ip'])
if 'port' in dev:
dev.setdefault('replication_port', dev['port'])
return builder
def save(self, builder_file):
"""Serialize this RingBuilder instance to disk.
:param builder_file: path to builder file to save
"""
with open(builder_file, 'wb') as f:
pickle.dump(self.to_dict(), f, protocol=2)
def search_devs(self, search_values):
"""Search devices by parameters.
:param search_values: a dictionary with search values to filter
devices, supported parameters are id,
region, zone, ip, port, replication_ip,
replication_port, device, weight, meta
:returns: list of device dicts
"""
matched_devs = []
for dev in self.devs:
if not dev:
continue
matched = True
for key in ('id', 'region', 'zone', 'ip', 'port', 'replication_ip',
'replication_port', 'device', 'weight', 'meta'):
if key in search_values:
value = search_values.get(key)
if value is not None:
if key == 'meta':
if value not in dev.get(key):
matched = False
elif key == 'ip' or key == 'replication_ip':
cdev = ''
try:
cdev = validate_and_normalize_address(
dev.get(key, ''))
except ValueError:
pass
if cdev != value:
matched = False
elif dev.get(key) != value:
matched = False
if matched:
matched_devs.append(dev)
return matched_devs
def increase_partition_power(self):
""" Increases ring partition power by one.
Devices will be assigned to partitions like this:
OLD: 0, 3, 7, 5, 2, 1, ...
NEW: 0, 0, 3, 3, 7, 7, 5, 5, 2, 2, 1, 1, ...
"""
new_replica2part2dev = []
for replica in self._replica2part2dev:
new_replica = array('H')
for device in replica:
new_replica.append(device)
new_replica.append(device) # append device a second time
new_replica2part2dev.append(new_replica)
self._replica2part2dev = new_replica2part2dev
for device in self._iter_devs():
device['parts'] *= 2
# We need to update the time when a partition has been moved the last
# time. Since this is an array of all partitions, we need to double it
# two
new_last_part_moves = []
for partition in self._last_part_moves:
new_last_part_moves.append(partition)
new_last_part_moves.append(partition)
self._last_part_moves = new_last_part_moves
self.part_power += 1
self.parts *= 2
self.version += 1
|