services/keep-balance/balance_test.go

   1 // Copyright (C) The Arvados Authors. All rights reserved.
   2 //
   3 // SPDX-License-Identifier: AGPL-3.0
   4
   5 package main
   6
   7 import (
   8         "crypto/md5"
   9         "fmt"
  10         "sort"
  11         "strconv"
  12         "testing"
  13         "time"
  14
  15         "git.curoverse.com/arvados.git/sdk/go/arvados"
  16
  17         check "gopkg.in/check.v1"
  18 )
  19
  20 // Test with Gocheck
  21 func Test(t *testing.T) {
  22         check.TestingT(t)
  23 }
  24
  25 var _ = check.Suite(&balancerSuite{})
  26
  27 type balancerSuite struct {
  28         Balancer
  29         srvs            []*KeepService
  30         blks            map[string]tester
  31         knownRendezvous [][]int
  32         signatureTTL    int64
  33 }
  34
  35 const (
  36         // index into knownRendezvous
  37         known0 = 0
  38 )
  39
  40 type slots []int
  41
  42 type tester struct {
  43         known       int
  44         desired     map[string]int
  45         current     slots
  46         timestamps  []int64
  47         shouldPull  slots
  48         shouldTrash slots
  49
  50         shouldPullMounts  []string
  51         shouldTrashMounts []string
  52
  53         expectResult balanceResult
  54 }
  55
  56 func (bal *balancerSuite) SetUpSuite(c *check.C) {
  57         bal.knownRendezvous = nil
  58         for _, str := range []string{
  59                 "3eab2d5fc9681074",
  60                 "097dba52e648f1c3",
  61                 "c5b4e023f8a7d691",
  62                 "9d81c02e76a3bf54",
  63         } {
  64                 var slots []int
  65                 for _, c := range []byte(str) {
  66                         pos, _ := strconv.ParseUint(string(c), 16, 4)
  67                         slots = append(slots, int(pos))
  68                 }
  69                 bal.knownRendezvous = append(bal.knownRendezvous, slots)
  70         }
  71
  72         bal.signatureTTL = 3600
  73 }
  74
  75 func (bal *balancerSuite) SetUpTest(c *check.C) {
  76         bal.srvs = make([]*KeepService, 16)
  77         bal.KeepServices = make(map[string]*KeepService)
  78         for i := range bal.srvs {
  79                 srv := &KeepService{
  80                         KeepService: arvados.KeepService{
  81                                 UUID: fmt.Sprintf("zzzzz-bi6l4-%015x", i),
  82                         },
  83                 }
  84                 srv.mounts = []*KeepMount{{
  85                         KeepMount: arvados.KeepMount{
  86                                 UUID: fmt.Sprintf("zzzzz-mount-%015x", i),
  87                         },
  88                         KeepService: srv,
  89                 }}
  90                 bal.srvs[i] = srv
  91                 bal.KeepServices[srv.UUID] = srv
  92         }
  93
  94         bal.MinMtime = time.Now().UnixNano() - bal.signatureTTL*1e9
  95         bal.cleanupMounts()
  96 }
  97
  98 func (bal *balancerSuite) TestPerfect(c *check.C) {
  99         bal.try(c, tester{
 100                 desired:     map[string]int{"default": 2},
 101                 current:     slots{0, 1},
 102                 shouldPull:  nil,
 103                 shouldTrash: nil})
 104 }
 105
 106 func (bal *balancerSuite) TestDecreaseRepl(c *check.C) {
 107         bal.try(c, tester{
 108                 desired:     map[string]int{"default": 2},
 109                 current:     slots{0, 2, 1},
 110                 shouldTrash: slots{2}})
 111 }
 112
 113 func (bal *balancerSuite) TestDecreaseReplToZero(c *check.C) {
 114         bal.try(c, tester{
 115                 desired:     map[string]int{"default": 0},
 116                 current:     slots{0, 1, 3},
 117                 shouldTrash: slots{0, 1, 3}})
 118 }
 119
 120 func (bal *balancerSuite) TestIncreaseRepl(c *check.C) {
 121         bal.try(c, tester{
 122                 desired:    map[string]int{"default": 4},
 123                 current:    slots{0, 1},
 124                 shouldPull: slots{2, 3}})
 125 }
 126
 127 func (bal *balancerSuite) TestSkipReadonly(c *check.C) {
 128         bal.srvList(0, slots{3})[0].ReadOnly = true
 129         bal.try(c, tester{
 130                 desired:    map[string]int{"default": 4},
 131                 current:    slots{0, 1},
 132                 shouldPull: slots{2, 4}})
 133 }
 134
 135 func (bal *balancerSuite) TestFixUnbalanced(c *check.C) {
 136         bal.try(c, tester{
 137                 desired:    map[string]int{"default": 2},
 138                 current:    slots{2, 0},
 139                 shouldPull: slots{1}})
 140         bal.try(c, tester{
 141                 desired:    map[string]int{"default": 2},
 142                 current:    slots{2, 7},
 143                 shouldPull: slots{0, 1}})
 144         // if only one of the pulls succeeds, we'll see this next:
 145         bal.try(c, tester{
 146                 desired:     map[string]int{"default": 2},
 147                 current:     slots{2, 1, 7},
 148                 shouldPull:  slots{0},
 149                 shouldTrash: slots{7}})
 150         // if both pulls succeed, we'll see this next:
 151         bal.try(c, tester{
 152                 desired:     map[string]int{"default": 2},
 153                 current:     slots{2, 0, 1, 7},
 154                 shouldTrash: slots{2, 7}})
 155
 156         // unbalanced + excessive replication => pull + trash
 157         bal.try(c, tester{
 158                 desired:     map[string]int{"default": 2},
 159                 current:     slots{2, 5, 7},
 160                 shouldPull:  slots{0, 1},
 161                 shouldTrash: slots{7}})
 162 }
 163
 164 func (bal *balancerSuite) TestMultipleReplicasPerService(c *check.C) {
 165         for _, srv := range bal.srvs {
 166                 for i := 0; i < 3; i++ {
 167                         m := *(srv.mounts[0])
 168                         srv.mounts = append(srv.mounts, &m)
 169                 }
 170         }
 171         bal.try(c, tester{
 172                 desired:    map[string]int{"default": 2},
 173                 current:    slots{0, 0},
 174                 shouldPull: slots{1}})
 175         bal.try(c, tester{
 176                 desired:    map[string]int{"default": 2},
 177                 current:    slots{2, 2},
 178                 shouldPull: slots{0, 1}})
 179         bal.try(c, tester{
 180                 desired:     map[string]int{"default": 2},
 181                 current:     slots{0, 0, 1},
 182                 shouldTrash: slots{0}})
 183         bal.try(c, tester{
 184                 desired:     map[string]int{"default": 2},
 185                 current:     slots{1, 1, 0},
 186                 shouldTrash: slots{1}})
 187         bal.try(c, tester{
 188                 desired:     map[string]int{"default": 2},
 189                 current:     slots{1, 0, 1, 0, 2},
 190                 shouldTrash: slots{0, 1, 2}})
 191         bal.try(c, tester{
 192                 desired:     map[string]int{"default": 2},
 193                 current:     slots{1, 1, 1, 0, 2},
 194                 shouldTrash: slots{1, 1, 2}})
 195         bal.try(c, tester{
 196                 desired:     map[string]int{"default": 2},
 197                 current:     slots{1, 1, 2},
 198                 shouldPull:  slots{0},
 199                 shouldTrash: slots{1}})
 200         bal.try(c, tester{
 201                 desired:     map[string]int{"default": 2},
 202                 current:     slots{1, 1, 0},
 203                 timestamps:  []int64{12345678, 12345678, 12345679},
 204                 shouldTrash: nil})
 205         bal.try(c, tester{
 206                 desired:    map[string]int{"default": 2},
 207                 current:    slots{1, 1},
 208                 shouldPull: slots{0}})
 209 }
 210
 211 func (bal *balancerSuite) TestIncreaseReplTimestampCollision(c *check.C) {
 212         // For purposes of increasing replication, we assume identical
 213         // replicas are distinct.
 214         bal.try(c, tester{
 215                 desired:    map[string]int{"default": 4},
 216                 current:    slots{0, 1},
 217                 timestamps: []int64{12345678, 12345678},
 218                 shouldPull: slots{2, 3}})
 219 }
 220
 221 func (bal *balancerSuite) TestDecreaseReplTimestampCollision(c *check.C) {
 222         // For purposes of decreasing replication, we assume identical
 223         // replicas are NOT distinct.
 224         bal.try(c, tester{
 225                 desired:    map[string]int{"default": 2},
 226                 current:    slots{0, 1, 2},
 227                 timestamps: []int64{12345678, 12345678, 12345678}})
 228         bal.try(c, tester{
 229                 desired:    map[string]int{"default": 2},
 230                 current:    slots{0, 1, 2},
 231                 timestamps: []int64{12345678, 10000000, 10000000}})
 232 }
 233
 234 func (bal *balancerSuite) TestDecreaseReplBlockTooNew(c *check.C) {
 235         oldTime := bal.MinMtime - 3600
 236         newTime := bal.MinMtime + 3600
 237         // The excess replica is too new to delete.
 238         bal.try(c, tester{
 239                 desired:    map[string]int{"default": 2},
 240                 current:    slots{0, 1, 2},
 241                 timestamps: []int64{oldTime, newTime, newTime + 1},
 242                 expectResult: balanceResult{
 243                         have: 3,
 244                         want: 2,
 245                         classState: map[string]balancedBlockState{"default": {
 246                                 desired:      2,
 247                                 surplus:      1,
 248                                 unachievable: false}}}})
 249         // The best replicas are too new to delete, but the excess
 250         // replica is old enough.
 251         bal.try(c, tester{
 252                 desired:     map[string]int{"default": 2},
 253                 current:     slots{0, 1, 2},
 254                 timestamps:  []int64{newTime, newTime + 1, oldTime},
 255                 shouldTrash: slots{2}})
 256 }
 257
 258 func (bal *balancerSuite) TestCleanupMounts(c *check.C) {
 259         bal.srvs[3].mounts[0].KeepMount.ReadOnly = true
 260         bal.srvs[3].mounts[0].KeepMount.DeviceID = "abcdef"
 261         bal.srvs[14].mounts[0].KeepMount.DeviceID = "abcdef"
 262         c.Check(len(bal.srvs[3].mounts), check.Equals, 1)
 263         bal.cleanupMounts()
 264         c.Check(len(bal.srvs[3].mounts), check.Equals, 0)
 265         bal.try(c, tester{
 266                 known:      0,
 267                 desired:    map[string]int{"default": 2},
 268                 current:    slots{1},
 269                 shouldPull: slots{2}})
 270 }
 271
 272 func (bal *balancerSuite) TestVolumeReplication(c *check.C) {
 273         bal.srvs[0].mounts[0].KeepMount.Replication = 2  // srv 0
 274         bal.srvs[14].mounts[0].KeepMount.Replication = 2 // srv e
 275         bal.cleanupMounts()
 276         // block 0 rendezvous is 3,e,a -- so slot 1 has repl=2
 277         bal.try(c, tester{
 278                 known:      0,
 279                 desired:    map[string]int{"default": 2},
 280                 current:    slots{1},
 281                 shouldPull: slots{0}})
 282         bal.try(c, tester{
 283                 known:      0,
 284                 desired:    map[string]int{"default": 2},
 285                 current:    slots{0, 1},
 286                 shouldPull: nil})
 287         bal.try(c, tester{
 288                 known:       0,
 289                 desired:     map[string]int{"default": 2},
 290                 current:     slots{0, 1, 2},
 291                 shouldTrash: slots{2}})
 292         bal.try(c, tester{
 293                 known:       0,
 294                 desired:     map[string]int{"default": 3},
 295                 current:     slots{0, 2, 3, 4},
 296                 shouldPull:  slots{1},
 297                 shouldTrash: slots{4},
 298                 expectResult: balanceResult{
 299                         have: 4,
 300                         want: 3,
 301                         classState: map[string]balancedBlockState{"default": {
 302                                 desired:      3,
 303                                 surplus:      1,
 304                                 unachievable: false}}}})
 305         bal.try(c, tester{
 306                 known:       0,
 307                 desired:     map[string]int{"default": 3},
 308                 current:     slots{0, 1, 2, 3, 4},
 309                 shouldTrash: slots{2, 3, 4}})
 310         bal.try(c, tester{
 311                 known:       0,
 312                 desired:     map[string]int{"default": 4},
 313                 current:     slots{0, 1, 2, 3, 4},
 314                 shouldTrash: slots{3, 4},
 315                 expectResult: balanceResult{
 316                         have: 6,
 317                         want: 4,
 318                         classState: map[string]balancedBlockState{"default": {
 319                                 desired:      4,
 320                                 surplus:      2,
 321                                 unachievable: false}}}})
 322         // block 1 rendezvous is 0,9,7 -- so slot 0 has repl=2
 323         bal.try(c, tester{
 324                 known:   1,
 325                 desired: map[string]int{"default": 2},
 326                 current: slots{0},
 327                 expectResult: balanceResult{
 328                         have: 2,
 329                         want: 2,
 330                         classState: map[string]balancedBlockState{"default": {
 331                                 desired:      2,
 332                                 surplus:      0,
 333                                 unachievable: false}}}})
 334         bal.try(c, tester{
 335                 known:      1,
 336                 desired:    map[string]int{"default": 3},
 337                 current:    slots{0},
 338                 shouldPull: slots{1}})
 339         bal.try(c, tester{
 340                 known:      1,
 341                 desired:    map[string]int{"default": 4},
 342                 current:    slots{0},
 343                 shouldPull: slots{1, 2}})
 344         bal.try(c, tester{
 345                 known:      1,
 346                 desired:    map[string]int{"default": 4},
 347                 current:    slots{2},
 348                 shouldPull: slots{0, 1}})
 349         bal.try(c, tester{
 350                 known:      1,
 351                 desired:    map[string]int{"default": 4},
 352                 current:    slots{7},
 353                 shouldPull: slots{0, 1, 2},
 354                 expectResult: balanceResult{
 355                         have: 1,
 356                         want: 4,
 357                         classState: map[string]balancedBlockState{"default": {
 358                                 desired:      4,
 359                                 surplus:      -3,
 360                                 unachievable: false}}}})
 361         bal.try(c, tester{
 362                 known:       1,
 363                 desired:     map[string]int{"default": 2},
 364                 current:     slots{1, 2, 3, 4},
 365                 shouldPull:  slots{0},
 366                 shouldTrash: slots{3, 4}})
 367         bal.try(c, tester{
 368                 known:       1,
 369                 desired:     map[string]int{"default": 2},
 370                 current:     slots{0, 1, 2},
 371                 shouldTrash: slots{1, 2},
 372                 expectResult: balanceResult{
 373                         have: 4,
 374                         want: 2,
 375                         classState: map[string]balancedBlockState{"default": {
 376                                 desired:      2,
 377                                 surplus:      2,
 378                                 unachievable: false}}}})
 379 }
 380
 381 func (bal *balancerSuite) TestDeviceRWMountedByMultipleServers(c *check.C) {
 382         bal.srvs[0].mounts[0].KeepMount.DeviceID = "abcdef"
 383         bal.srvs[9].mounts[0].KeepMount.DeviceID = "abcdef"
 384         bal.srvs[14].mounts[0].KeepMount.DeviceID = "abcdef"
 385         // block 0 belongs on servers 3 and e, which have different
 386         // device IDs.
 387         bal.try(c, tester{
 388                 known:      0,
 389                 desired:    map[string]int{"default": 2},
 390                 current:    slots{1},
 391                 shouldPull: slots{0}})
 392         // block 1 belongs on servers 0 and 9, which both report
 393         // having a replica, but the replicas are on the same device
 394         // ID -- so we should pull to the third position (7).
 395         bal.try(c, tester{
 396                 known:      1,
 397                 desired:    map[string]int{"default": 2},
 398                 current:    slots{0, 1},
 399                 shouldPull: slots{2}})
 400         // block 1 can be pulled to the doubly-mounted device, but the
 401         // pull should only be done on the first of the two servers.
 402         bal.try(c, tester{
 403                 known:      1,
 404                 desired:    map[string]int{"default": 2},
 405                 current:    slots{2},
 406                 shouldPull: slots{0}})
 407         // block 0 has one replica on a single device mounted on two
 408         // servers (e,9 at positions 1,9). Trashing the replica on 9
 409         // would lose the block.
 410         bal.try(c, tester{
 411                 known:      0,
 412                 desired:    map[string]int{"default": 2},
 413                 current:    slots{1, 9},
 414                 shouldPull: slots{0},
 415                 expectResult: balanceResult{
 416                         have: 1,
 417                         classState: map[string]balancedBlockState{"default": {
 418                                 desired:      2,
 419                                 surplus:      -1,
 420                                 unachievable: false}}}})
 421         // block 0 is overreplicated, but the second and third
 422         // replicas are the same replica according to DeviceID
 423         // (despite different Mtimes). Don't trash the third replica.
 424         bal.try(c, tester{
 425                 known:   0,
 426                 desired: map[string]int{"default": 2},
 427                 current: slots{0, 1, 9},
 428                 expectResult: balanceResult{
 429                         have: 2,
 430                         classState: map[string]balancedBlockState{"default": {
 431                                 desired:      2,
 432                                 surplus:      0,
 433                                 unachievable: false}}}})
 434         // block 0 is overreplicated; the third and fifth replicas are
 435         // extra, but the fourth is another view of the second and
 436         // shouldn't be trashed.
 437         bal.try(c, tester{
 438                 known:       0,
 439                 desired:     map[string]int{"default": 2},
 440                 current:     slots{0, 1, 5, 9, 12},
 441                 shouldTrash: slots{5, 12},
 442                 expectResult: balanceResult{
 443                         have: 4,
 444                         classState: map[string]balancedBlockState{"default": {
 445                                 desired:      2,
 446                                 surplus:      2,
 447                                 unachievable: false}}}})
 448 }
 449
 450 func (bal *balancerSuite) TestChangeStorageClasses(c *check.C) {
 451         // For known blocks 0/1/2/3, server 9 is slot 9/1/14/0 in
 452         // probe order. For these tests we give it two mounts, one
 453         // with classes=[special], one with
 454         // classes=[special,special2].
 455         bal.srvs[9].mounts = []*KeepMount{{
 456                 KeepMount: arvados.KeepMount{
 457                         Replication:    1,
 458                         StorageClasses: []string{"special"},
 459                         UUID:           "zzzzz-mount-special00000009",
 460                         DeviceID:       "9-special",
 461                 },
 462                 KeepService: bal.srvs[9],
 463         }, {
 464                 KeepMount: arvados.KeepMount{
 465                         Replication:    1,
 466                         StorageClasses: []string{"special", "special2"},
 467                         UUID:           "zzzzz-mount-special20000009",
 468                         DeviceID:       "9-special-and-special2",
 469                 },
 470                 KeepService: bal.srvs[9],
 471         }}
 472         // For known blocks 0/1/2/3, server 13 (d) is slot 5/3/11/1 in
 473         // probe order. We give it two mounts, one with
 474         // classes=[special3], one with classes=[default].
 475         bal.srvs[13].mounts = []*KeepMount{{
 476                 KeepMount: arvados.KeepMount{
 477                         Replication:    1,
 478                         StorageClasses: []string{"special2"},
 479                         UUID:           "zzzzz-mount-special2000000d",
 480                         DeviceID:       "13-special2",
 481                 },
 482                 KeepService: bal.srvs[13],
 483         }, {
 484                 KeepMount: arvados.KeepMount{
 485                         Replication:    1,
 486                         StorageClasses: []string{"default"},
 487                         UUID:           "zzzzz-mount-00000000000000d",
 488                         DeviceID:       "13-default",
 489                 },
 490                 KeepService: bal.srvs[13],
 491         }}
 492         // Pull to slot 9 because that's the only server with the
 493         // desired class "special".
 494         bal.try(c, tester{
 495                 known:            0,
 496                 desired:          map[string]int{"default": 2, "special": 1},
 497                 current:          slots{0, 1},
 498                 shouldPull:       slots{9},
 499                 shouldPullMounts: []string{"zzzzz-mount-special00000009"}})
 500         // If some storage classes are not satisfied, don't trash any
 501         // excess replicas. (E.g., if someone desires repl=1 on
 502         // class=durable, and we have two copies on class=volatile, we
 503         // should wait for pull to succeed before trashing anything).
 504         bal.try(c, tester{
 505                 known:            0,
 506                 desired:          map[string]int{"special": 1},
 507                 current:          slots{0, 1},
 508                 shouldPull:       slots{9},
 509                 shouldPullMounts: []string{"zzzzz-mount-special00000009"}})
 510         // Once storage classes are satisfied, trash excess replicas
 511         // that appear earlier in probe order but aren't needed to
 512         // satisfy the desired classes.
 513         bal.try(c, tester{
 514                 known:       0,
 515                 desired:     map[string]int{"special": 1},
 516                 current:     slots{0, 1, 9},
 517                 shouldTrash: slots{0, 1}})
 518         // Pull to slot 5, the best server with class "special2".
 519         bal.try(c, tester{
 520                 known:            0,
 521                 desired:          map[string]int{"special2": 1},
 522                 current:          slots{0, 1},
 523                 shouldPull:       slots{5},
 524                 shouldPullMounts: []string{"zzzzz-mount-special2000000d"}})
 525         // Pull to slot 5 and 9 to get replication 2 in desired class
 526         // "special2".
 527         bal.try(c, tester{
 528                 known:            0,
 529                 desired:          map[string]int{"special2": 2},
 530                 current:          slots{0, 1},
 531                 shouldPull:       slots{5, 9},
 532                 shouldPullMounts: []string{"zzzzz-mount-special20000009", "zzzzz-mount-special2000000d"}})
 533         // Slot 0 has a replica in "default", slot 1 has a replica
 534         // in "special"; we need another replica in "default", i.e.,
 535         // on slot 2.
 536         bal.try(c, tester{
 537                 known:      1,
 538                 desired:    map[string]int{"default": 2, "special": 1},
 539                 current:    slots{0, 1},
 540                 shouldPull: slots{2}})
 541         // Pull to best probe position 0 (despite wrong storage class)
 542         // if it's impossible to achieve desired replication in the
 543         // desired class (only slots 1 and 3 have special2).
 544         bal.try(c, tester{
 545                 known:      1,
 546                 desired:    map[string]int{"special2": 3},
 547                 current:    slots{3},
 548                 shouldPull: slots{0, 1}})
 549         // Trash excess replica.
 550         bal.try(c, tester{
 551                 known:       3,
 552                 desired:     map[string]int{"special": 1},
 553                 current:     slots{0, 1},
 554                 shouldTrash: slots{1}})
 555         // Leave one copy on slot 1 because slot 0 (server 9) only
 556         // gives us repl=1.
 557         bal.try(c, tester{
 558                 known:   3,
 559                 desired: map[string]int{"special": 2},
 560                 current: slots{0, 1}})
 561 }
 562
 563 // Clear all servers' changesets, balance a single block, and verify
 564 // the appropriate changes for that block have been added to the
 565 // changesets.
 566 func (bal *balancerSuite) try(c *check.C, t tester) {
 567         bal.setupLookupTables()
 568         blk := &BlockState{
 569                 Replicas: bal.replList(t.known, t.current),
 570                 Desired:  t.desired,
 571         }
 572         for i, t := range t.timestamps {
 573                 blk.Replicas[i].Mtime = t
 574         }
 575         for _, srv := range bal.srvs {
 576                 srv.ChangeSet = &ChangeSet{}
 577         }
 578         result := bal.balanceBlock(knownBlkid(t.known), blk)
 579
 580         var didPull, didTrash slots
 581         var didPullMounts, didTrashMounts []string
 582         for i, srv := range bal.srvs {
 583                 var slot int
 584                 for probeOrder, srvNum := range bal.knownRendezvous[t.known] {
 585                         if srvNum == i {
 586                                 slot = probeOrder
 587                         }
 588                 }
 589                 for _, pull := range srv.Pulls {
 590                         didPull = append(didPull, slot)
 591                         didPullMounts = append(didPullMounts, pull.To.UUID)
 592                         c.Check(pull.SizedDigest, check.Equals, knownBlkid(t.known))
 593                 }
 594                 for _, trash := range srv.Trashes {
 595                         didTrash = append(didTrash, slot)
 596                         didTrashMounts = append(didTrashMounts, trash.From.UUID)
 597                         c.Check(trash.SizedDigest, check.Equals, knownBlkid(t.known))
 598                 }
 599         }
 600
 601         for _, list := range []slots{didPull, didTrash, t.shouldPull, t.shouldTrash} {
 602                 sort.Sort(sort.IntSlice(list))
 603         }
 604         c.Check(didPull, check.DeepEquals, t.shouldPull)
 605         c.Check(didTrash, check.DeepEquals, t.shouldTrash)
 606         if t.shouldPullMounts != nil {
 607                 sort.Strings(didPullMounts)
 608                 c.Check(didPullMounts, check.DeepEquals, t.shouldPullMounts)
 609         }
 610         if t.shouldTrashMounts != nil {
 611                 sort.Strings(didTrashMounts)
 612                 c.Check(didTrashMounts, check.DeepEquals, t.shouldTrashMounts)
 613         }
 614         if t.expectResult.have > 0 {
 615                 c.Check(result.have, check.Equals, t.expectResult.have)
 616         }
 617         if t.expectResult.want > 0 {
 618                 c.Check(result.want, check.Equals, t.expectResult.want)
 619         }
 620         if t.expectResult.classState != nil {
 621                 c.Check(result.classState, check.DeepEquals, t.expectResult.classState)
 622         }
 623 }
 624
 625 // srvList returns the KeepServices, sorted in rendezvous order and
 626 // then selected by idx. For example, srvList(3, slots{0, 1, 4})
 627 // returns the the first-, second-, and fifth-best servers for storing
 628 // bal.knownBlkid(3).
 629 func (bal *balancerSuite) srvList(knownBlockID int, order slots) (srvs []*KeepService) {
 630         for _, i := range order {
 631                 srvs = append(srvs, bal.srvs[bal.knownRendezvous[knownBlockID][i]])
 632         }
 633         return
 634 }
 635
 636 // replList is like srvList but returns an "existing replicas" slice,
 637 // suitable for a BlockState test fixture.
 638 func (bal *balancerSuite) replList(knownBlockID int, order slots) (repls []Replica) {
 639         nextMnt := map[*KeepService]int{}
 640         mtime := time.Now().UnixNano() - (bal.signatureTTL+86400)*1e9
 641         for _, srv := range bal.srvList(knownBlockID, order) {
 642                 // round-robin repls onto each srv's mounts
 643                 n := nextMnt[srv]
 644                 nextMnt[srv] = (n + 1) % len(srv.mounts)
 645
 646                 repls = append(repls, Replica{srv.mounts[n], mtime})
 647                 mtime++
 648         }
 649         return
 650 }
 651
 652 // generate the same data hashes that are tested in
 653 // sdk/go/keepclient/root_sorter_test.go
 654 func knownBlkid(i int) arvados.SizedDigest {
 655         return arvados.SizedDigest(fmt.Sprintf("%x+64", md5.Sum([]byte(fmt.Sprintf("%064x", i)))))
 656 }