forked from keybase/client
-
Notifications
You must be signed in to change notification settings - Fork 0
/
disk_block_cache_wrapped.go
623 lines (572 loc) · 18.6 KB
/
disk_block_cache_wrapped.go
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
// Copyright 2017 Keybase Inc. All rights reserved.
// Use of this source code is governed by a BSD
// license that can be found in the LICENSE file.
package libkbfs
import (
"path/filepath"
"sync"
"github.com/keybase/client/go/kbfs/data"
"github.com/keybase/client/go/kbfs/kbfsblock"
"github.com/keybase/client/go/kbfs/kbfscrypto"
"github.com/keybase/client/go/kbfs/kbfsmd"
"github.com/keybase/client/go/kbfs/kbfssync"
"github.com/keybase/client/go/kbfs/tlf"
"github.com/pkg/errors"
ldberrors "github.com/syndtr/goleveldb/leveldb/errors"
"golang.org/x/net/context"
)
const (
workingSetCacheFolderName = "kbfs_block_cache"
syncCacheFolderName = "kbfs_sync_cache"
)
// diskBlockCacheConfig specifies the interfaces that a DiskBlockCacheStandard
// needs to perform its functions. This adheres to the standard libkbfs Config
// API.
type diskBlockCacheConfig interface {
codecGetter
logMaker
clockGetter
diskLimiterGetter
initModeGetter
blockCacher
}
type diskBlockCacheWrapped struct {
config diskBlockCacheConfig
storageRoot string
// Protects the caches
mtx sync.RWMutex
workingSetCache *DiskBlockCacheLocal
syncCache *DiskBlockCacheLocal
deleteGroup kbfssync.RepeatedWaitGroup
}
var _ DiskBlockCache = (*diskBlockCacheWrapped)(nil)
func (cache *diskBlockCacheWrapped) enableCache(
typ diskLimitTrackerType, cacheFolder string, mode InitMode) (err error) {
cache.mtx.Lock()
defer cache.mtx.Unlock()
var cachePtr **DiskBlockCacheLocal
switch typ {
case syncCacheLimitTrackerType:
cachePtr = &cache.syncCache
case workingSetCacheLimitTrackerType:
cachePtr = &cache.workingSetCache
default:
return errors.New("invalid disk cache type")
}
if *cachePtr != nil {
// We already have a cache of the desired type. Thus, this method is
// idempotent.
return nil
}
if mode.IsTestMode() {
*cachePtr, err = newDiskBlockCacheLocalForTest(
cache.config, typ)
} else {
cacheStorageRoot := filepath.Join(cache.storageRoot, cacheFolder)
*cachePtr, err = newDiskBlockCacheLocal(
cache.config, typ, cacheStorageRoot, mode)
}
return err
}
func newDiskBlockCacheWrapped(
config diskBlockCacheConfig, storageRoot string, mode InitMode) (
cache *diskBlockCacheWrapped, err error) {
cache = &diskBlockCacheWrapped{
config: config,
storageRoot: storageRoot,
}
err = cache.enableCache(
workingSetCacheLimitTrackerType, workingSetCacheFolderName, mode)
if err != nil {
return nil, err
}
syncCacheErr := cache.enableCache(
syncCacheLimitTrackerType, syncCacheFolderName, mode)
if syncCacheErr != nil {
log := config.MakeLogger("DBC")
log.Warning("Could not initialize sync block cache.")
// We still return success because the working set cache successfully
// initialized.
}
return cache, nil
}
func (cache *diskBlockCacheWrapped) getCacheLocked(
cacheType DiskBlockCacheType) (*DiskBlockCacheLocal, error) {
if cacheType == DiskBlockSyncCache {
if cache.syncCache == nil {
return nil, errors.New("Sync cache not enabled")
}
return cache.syncCache, nil
}
return cache.workingSetCache, nil
}
// DoesCacheHaveSpace implements the DiskBlockCache interface for
// diskBlockCacheWrapped.
func (cache *diskBlockCacheWrapped) DoesCacheHaveSpace(
ctx context.Context, cacheType DiskBlockCacheType) (bool, int64, error) {
cache.mtx.RLock()
defer cache.mtx.RUnlock()
c, err := cache.getCacheLocked(cacheType)
if err != nil {
return false, 0, err
}
return c.DoesCacheHaveSpace(ctx)
}
// IsSyncCacheEnabled returns true if the sync cache is enabled.
func (cache *diskBlockCacheWrapped) IsSyncCacheEnabled() bool {
return cache.syncCache != nil
}
func (cache *diskBlockCacheWrapped) rankCachesLocked(
preferredCacheType DiskBlockCacheType) (
primaryCache, secondaryCache *DiskBlockCacheLocal) {
if preferredCacheType != DiskBlockWorkingSetCache {
if cache.syncCache == nil {
log := cache.config.MakeLogger("DBC")
log.Warning("Sync cache is preferred, but there is no sync cache")
return cache.workingSetCache, nil
}
return cache.syncCache, cache.workingSetCache
}
return cache.workingSetCache, cache.syncCache
}
func (cache *diskBlockCacheWrapped) moveBetweenCachesWithBlockLocked(
ctx context.Context, tlfID tlf.ID, blockID kbfsblock.ID, buf []byte,
serverHalf kbfscrypto.BlockCryptKeyServerHalf,
prefetchStatus PrefetchStatus, newCacheType DiskBlockCacheType) {
primaryCache, secondaryCache := cache.rankCachesLocked(newCacheType)
// Move the block into its preferred cache.
err := primaryCache.Put(ctx, tlfID, blockID, buf, serverHalf)
if err != nil {
// The cache will log the non-fatal error, so just return.
return
}
if prefetchStatus == FinishedPrefetch {
// Don't propagate a finished status to the primary
// cache, since the status needs to be with respect to
// that particular cache (i.e., if the primary cache
// is the sync cache, all the child blocks must be in
// the sync cache, for this block to be considered
// synced, and we can't verify that here).
prefetchStatus = TriggeredPrefetch
}
if prefetchStatus != NoPrefetch {
_ = primaryCache.UpdateMetadata(ctx, blockID, prefetchStatus)
}
// Remove the block from the non-preferred cache (which is
// set to be the secondary cache at this point).
cache.deleteGroup.Add(1)
go func() {
defer cache.deleteGroup.Done()
// Don't catch the errors -- this is just best effort.
_, _, _ = secondaryCache.Delete(ctx, []kbfsblock.ID{blockID})
}()
}
// Get implements the DiskBlockCache interface for diskBlockCacheWrapped.
func (cache *diskBlockCacheWrapped) Get(
ctx context.Context, tlfID tlf.ID, blockID kbfsblock.ID,
preferredCacheType DiskBlockCacheType) (
buf []byte, serverHalf kbfscrypto.BlockCryptKeyServerHalf,
prefetchStatus PrefetchStatus, err error) {
cache.mtx.RLock()
defer cache.mtx.RUnlock()
primaryCache, secondaryCache := cache.rankCachesLocked(preferredCacheType)
// Check both caches if the primary cache doesn't have the block.
buf, serverHalf, prefetchStatus, err = primaryCache.Get(ctx, tlfID, blockID)
if _, isNoSuchBlockError := errors.Cause(err).(data.NoSuchBlockError); isNoSuchBlockError &&
secondaryCache != nil {
buf, serverHalf, prefetchStatus, err = secondaryCache.Get(
ctx, tlfID, blockID)
if err != nil {
return nil, kbfscrypto.BlockCryptKeyServerHalf{}, NoPrefetch, err
}
if preferredCacheType != DiskBlockAnyCache {
cache.moveBetweenCachesWithBlockLocked(
ctx, tlfID, blockID, buf, serverHalf, prefetchStatus,
preferredCacheType)
}
}
return buf, serverHalf, prefetchStatus, err
}
// GetMetadata implements the DiskBlockCache interface for
// diskBlockCacheWrapped.
func (cache *diskBlockCacheWrapped) GetMetadata(ctx context.Context,
blockID kbfsblock.ID) (metadata DiskBlockCacheMetadata, err error) {
cache.mtx.RLock()
defer cache.mtx.RUnlock()
if cache.syncCache != nil {
md, err := cache.syncCache.GetMetadata(ctx, blockID)
switch errors.Cause(err) {
case nil:
return md, nil
case ldberrors.ErrNotFound:
default:
return md, err
}
}
return cache.workingSetCache.GetMetadata(ctx, blockID)
}
func (cache *diskBlockCacheWrapped) moveBetweenCachesLocked(
ctx context.Context, tlfID tlf.ID, blockID kbfsblock.ID,
newCacheType DiskBlockCacheType) (moved bool) {
_, secondaryCache := cache.rankCachesLocked(newCacheType)
buf, serverHalf, prefetchStatus, err := secondaryCache.Get(
ctx, tlfID, blockID)
if err != nil {
// The block isn't in the secondary cache, so there's nothing to move.
return false
}
cache.moveBetweenCachesWithBlockLocked(
ctx, tlfID, blockID, buf, serverHalf, prefetchStatus, newCacheType)
return true
}
// GetPefetchStatus implements the DiskBlockCache interface for
// diskBlockCacheWrapped.
func (cache *diskBlockCacheWrapped) GetPrefetchStatus(
ctx context.Context, tlfID tlf.ID, blockID kbfsblock.ID,
cacheType DiskBlockCacheType) (prefetchStatus PrefetchStatus, err error) {
cache.mtx.RLock()
defer cache.mtx.RUnlock()
// Try the sync cache first unless working set cache is required.
if cacheType != DiskBlockWorkingSetCache {
if cache.syncCache == nil {
return NoPrefetch, errors.New("Sync cache not enabled")
}
md, err := cache.syncCache.GetMetadata(ctx, blockID)
switch errors.Cause(err) {
case nil:
return md.PrefetchStatus(), nil
case ldberrors.ErrNotFound:
if cacheType == DiskBlockSyncCache {
// Try moving the block and getting it again.
moved := cache.moveBetweenCachesLocked(
ctx, tlfID, blockID, cacheType)
if moved {
md, err := cache.syncCache.GetMetadata(ctx, blockID)
if err != nil {
return NoPrefetch, err
}
return md.PrefetchStatus(), nil
}
return NoPrefetch, err
}
// Otherwise try the working set cache below.
default:
return NoPrefetch, err
}
}
md, err := cache.workingSetCache.GetMetadata(ctx, blockID)
if err != nil {
return NoPrefetch, err
}
return md.PrefetchStatus(), nil
}
// Put implements the DiskBlockCache interface for diskBlockCacheWrapped.
func (cache *diskBlockCacheWrapped) Put(ctx context.Context, tlfID tlf.ID,
blockID kbfsblock.ID, buf []byte,
serverHalf kbfscrypto.BlockCryptKeyServerHalf,
cacheType DiskBlockCacheType) error {
// This is a write operation but we are only reading the pointers to the
// caches. So we use a read lock.
cache.mtx.RLock()
defer cache.mtx.RUnlock()
if cacheType == DiskBlockSyncCache && cache.syncCache != nil {
workingSetCache := cache.workingSetCache
err := cache.syncCache.Put(ctx, tlfID, blockID, buf, serverHalf)
if err == nil {
cache.deleteGroup.Add(1)
go func() {
defer cache.deleteGroup.Done()
// Don't catch the errors -- this is just best effort.
_, _, _ = workingSetCache.Delete(ctx, []kbfsblock.ID{blockID})
}()
return nil
}
// Otherwise drop through and put it into the working set cache.
}
// No need to put it in the working cache if it's already in the
// sync cache.
if cache.syncCache != nil {
_, _, _, err := cache.syncCache.Get(ctx, tlfID, blockID)
if err == nil {
return nil
}
}
return cache.workingSetCache.Put(ctx, tlfID, blockID, buf, serverHalf)
}
// Delete implements the DiskBlockCache interface for diskBlockCacheWrapped.
func (cache *diskBlockCacheWrapped) Delete(ctx context.Context,
blockIDs []kbfsblock.ID, cacheType DiskBlockCacheType) (
numRemoved int, sizeRemoved int64, err error) {
// This is a write operation but we are only reading the pointers to the
// caches. So we use a read lock.
cache.mtx.RLock()
defer cache.mtx.RUnlock()
if cache.syncCache == nil && cacheType == DiskBlockSyncCache {
return 0, 0, errors.New("Sync cache not enabled")
} else if cache.syncCache != nil &&
(cacheType == DiskBlockAnyCache || cacheType == DiskBlockSyncCache) {
numRemoved, sizeRemoved, err = cache.syncCache.Delete(ctx, blockIDs)
if err != nil {
return 0, 0, err
}
if cacheType == DiskBlockSyncCache {
return numRemoved, sizeRemoved, err
}
}
wsNumRemoved, wsSizeRemoved, err := cache.workingSetCache.Delete(
ctx, blockIDs)
if err != nil {
return 0, 0, err
}
return wsNumRemoved + numRemoved, wsSizeRemoved + sizeRemoved, nil
}
// UpdateMetadata implements the DiskBlockCache interface for
// diskBlockCacheWrapped.
func (cache *diskBlockCacheWrapped) UpdateMetadata(
ctx context.Context, tlfID tlf.ID, blockID kbfsblock.ID,
prefetchStatus PrefetchStatus, cacheType DiskBlockCacheType) error {
// This is a write operation but we are only reading the pointers to the
// caches. So we use a read lock.
cache.mtx.RLock()
defer cache.mtx.RUnlock()
primaryCache, secondaryCache := cache.rankCachesLocked(cacheType)
err := primaryCache.UpdateMetadata(ctx, blockID, prefetchStatus)
_, isNoSuchBlockError := errors.Cause(err).(data.NoSuchBlockError)
if !isNoSuchBlockError {
return err
}
if cacheType == DiskBlockSyncCache {
// Try moving the block and getting it again.
moved := cache.moveBetweenCachesLocked(
ctx, tlfID, blockID, cacheType)
if moved {
err = primaryCache.UpdateMetadata(ctx, blockID, prefetchStatus)
}
return err
}
err = secondaryCache.UpdateMetadata(ctx, blockID, prefetchStatus)
_, isNoSuchBlockError = errors.Cause(err).(data.NoSuchBlockError)
if !isNoSuchBlockError {
return err
}
// Try one last time in the primary cache, in case of this
// sequence of events:
// 0) Block exists in secondary.
// 1) UpdateMetadata checks primary, gets NoSuchBlockError.
// 2) Other goroutine writes block to primary.
// 3) Other goroutine deletes block from primary.
// 4) UpdateMetadata checks secondary, gets NoSuchBlockError.
return primaryCache.UpdateMetadata(ctx, blockID, prefetchStatus)
}
// ClearAllTlfBlocks implements the DiskBlockCache interface for
// diskBlockCacheWrapper.
func (cache *diskBlockCacheWrapped) ClearAllTlfBlocks(
ctx context.Context, tlfID tlf.ID, cacheType DiskBlockCacheType) error {
cache.mtx.RLock()
defer cache.mtx.RUnlock()
c, err := cache.getCacheLocked(cacheType)
if err != nil {
return err
}
return c.ClearAllTlfBlocks(ctx, tlfID)
}
// GetLastUnrefRev implements the DiskBlockCache interface for
// diskBlockCacheWrapped.
func (cache *diskBlockCacheWrapped) GetLastUnrefRev(
ctx context.Context, tlfID tlf.ID, cacheType DiskBlockCacheType) (
kbfsmd.Revision, error) {
cache.mtx.RLock()
defer cache.mtx.RUnlock()
c, err := cache.getCacheLocked(cacheType)
if err != nil {
return kbfsmd.RevisionUninitialized, err
}
return c.GetLastUnrefRev(ctx, tlfID)
}
// PutLastUnrefRev implements the DiskBlockCache interface for
// diskBlockCacheWrapped.
func (cache *diskBlockCacheWrapped) PutLastUnrefRev(
ctx context.Context, tlfID tlf.ID, rev kbfsmd.Revision,
cacheType DiskBlockCacheType) error {
cache.mtx.RLock()
defer cache.mtx.RUnlock()
c, err := cache.getCacheLocked(cacheType)
if err != nil {
return err
}
return c.PutLastUnrefRev(ctx, tlfID, rev)
}
// Status implements the DiskBlockCache interface for diskBlockCacheWrapped.
func (cache *diskBlockCacheWrapped) Status(
ctx context.Context) map[string]DiskBlockCacheStatus {
// This is a write operation but we are only reading the pointers to the
// caches. So we use a read lock.
cache.mtx.RLock()
defer cache.mtx.RUnlock()
statuses := make(map[string]DiskBlockCacheStatus, 2)
if cache.workingSetCache != nil {
for name, status := range cache.workingSetCache.Status(ctx) {
statuses[name] = status
}
}
if cache.syncCache == nil {
return statuses
}
for name, status := range cache.syncCache.Status(ctx) {
statuses[name] = status
}
return statuses
}
// Mark implements the DiskBlockCache interface for diskBlockCacheWrapped.
func (cache *diskBlockCacheWrapped) Mark(
ctx context.Context, blockID kbfsblock.ID, tag string,
cacheType DiskBlockCacheType) error {
cache.mtx.RLock()
defer cache.mtx.RUnlock()
c, err := cache.getCacheLocked(cacheType)
if err != nil {
return err
}
return c.Mark(ctx, blockID, tag)
}
// DeleteUnmarked implements the DiskBlockCache interface for
// diskBlockCacheWrapped.
func (cache *diskBlockCacheWrapped) DeleteUnmarked(
ctx context.Context, tlfID tlf.ID, tag string,
cacheType DiskBlockCacheType) error {
cache.mtx.RLock()
defer cache.mtx.RUnlock()
c, err := cache.getCacheLocked(cacheType)
if err != nil {
return err
}
return c.DeleteUnmarked(ctx, tlfID, tag)
}
func (cache *diskBlockCacheWrapped) waitForDeletes(ctx context.Context) error {
return cache.deleteGroup.Wait(ctx)
}
// AddHomeTLF implements the DiskBlockCache interface for diskBlockCacheWrapped.
func (cache *diskBlockCacheWrapped) AddHomeTLF(ctx context.Context,
tlfID tlf.ID) error {
cache.mtx.RLock()
defer cache.mtx.RUnlock()
if cache.syncCache == nil {
return errors.New("Sync cache not enabled")
}
return cache.syncCache.AddHomeTLF(ctx, tlfID)
}
// ClearHomeTLFs implements the DiskBlockCache interface for
// diskBlockCacheWrapped.
func (cache *diskBlockCacheWrapped) ClearHomeTLFs(ctx context.Context) error {
cache.mtx.RLock()
defer cache.mtx.RUnlock()
if cache.syncCache == nil {
return errors.New("Sync cache not enabled")
}
return cache.syncCache.ClearHomeTLFs(ctx)
}
// GetTlfSize implements the DiskBlockCache interface for
// diskBlockCacheWrapped.
func (cache *diskBlockCacheWrapped) GetTlfSize(
ctx context.Context, tlfID tlf.ID, cacheType DiskBlockCacheType) (
size uint64, err error) {
cache.mtx.RLock()
defer cache.mtx.RUnlock()
if cacheType != DiskBlockWorkingSetCache && cache.syncCache != nil {
// Either sync cache only, or both.
syncSize, err := cache.syncCache.GetTlfSize(ctx, tlfID)
if err != nil {
return 0, err
}
size += syncSize
}
if cacheType != DiskBlockSyncCache {
// Either working set cache only, or both.
workingSetSize, err := cache.workingSetCache.GetTlfSize(ctx, tlfID)
if err != nil {
return 0, err
}
size += workingSetSize
}
return size, nil
}
// GetTlfSize implements the DiskBlockCache interface for
// diskBlockCacheWrapped.
func (cache *diskBlockCacheWrapped) GetTlfIDs(
ctx context.Context, cacheType DiskBlockCacheType) (
tlfIDs []tlf.ID, err error) {
cache.mtx.RLock()
defer cache.mtx.RUnlock()
if cacheType != DiskBlockWorkingSetCache && cache.syncCache != nil {
// Either sync cache only, or both.
tlfIDs, err = cache.syncCache.GetTlfIDs(ctx)
if err != nil {
return nil, err
}
}
if cacheType != DiskBlockSyncCache {
// Either working set cache only, or both.
wsTlfIDs, err := cache.workingSetCache.GetTlfIDs(ctx)
if err != nil {
return nil, err
}
// Uniquify them if needed.
if len(tlfIDs) == 0 {
tlfIDs = wsTlfIDs
} else {
s := make(map[tlf.ID]bool, len(tlfIDs)+len(wsTlfIDs))
for _, id := range tlfIDs {
s[id] = true
}
for _, id := range wsTlfIDs {
s[id] = true
}
tlfIDs = make([]tlf.ID, 0, len(s))
for id := range s {
tlfIDs = append(tlfIDs, id)
}
}
}
return tlfIDs, nil
}
// WaitUntilStarted implements the DiskBlockCache interface for
// diskBlockCacheWrapped.
func (cache *diskBlockCacheWrapped) WaitUntilStarted(
cacheType DiskBlockCacheType) (err error) {
cache.mtx.RLock()
defer cache.mtx.RUnlock()
if cacheType != DiskBlockWorkingSetCache && cache.syncCache != nil {
err = cache.syncCache.WaitUntilStarted()
if err != nil {
return err
}
}
if cacheType != DiskBlockSyncCache {
err = cache.workingSetCache.WaitUntilStarted()
if err != nil {
return err
}
}
return nil
}
// Shutdown implements the DiskBlockCache interface for diskBlockCacheWrapped.
func (cache *diskBlockCacheWrapped) Shutdown(ctx context.Context) <-chan struct{} {
cache.mtx.Lock()
defer cache.mtx.Unlock()
wsCh := cache.workingSetCache.Shutdown(ctx)
var syncCh <-chan struct{}
if cache.syncCache != nil {
syncCh = cache.syncCache.Shutdown(ctx)
} else {
ch := make(chan struct{})
close(ch)
syncCh = ch
}
retCh := make(chan struct{})
go func() {
<-wsCh
<-syncCh
close(retCh)
}()
return retCh
}