-
Notifications
You must be signed in to change notification settings - Fork 9.7k
/
kvstore.go
458 lines (389 loc) · 11.5 KB
/
kvstore.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
// Copyright 2015 The etcd Authors
//
// 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.
package mvcc
import (
"encoding/binary"
"errors"
"math"
"sync"
"time"
"github.com/coreos/etcd/lease"
"github.com/coreos/etcd/mvcc/backend"
"github.com/coreos/etcd/mvcc/mvccpb"
"github.com/coreos/etcd/pkg/schedule"
"github.com/coreos/pkg/capnslog"
"golang.org/x/net/context"
)
var (
keyBucketName = []byte("key")
metaBucketName = []byte("meta")
consistentIndexKeyName = []byte("consistent_index")
scheduledCompactKeyName = []byte("scheduledCompactRev")
finishedCompactKeyName = []byte("finishedCompactRev")
ErrCompacted = errors.New("mvcc: required revision has been compacted")
ErrFutureRev = errors.New("mvcc: required revision is a future revision")
ErrCanceled = errors.New("mvcc: watcher is canceled")
ErrClosed = errors.New("mvcc: closed")
plog = capnslog.NewPackageLogger("github.com/coreos/etcd", "mvcc")
)
const (
// markedRevBytesLen is the byte length of marked revision.
// The first `revBytesLen` bytes represents a normal revision. The last
// one byte is the mark.
markedRevBytesLen = revBytesLen + 1
markBytePosition = markedRevBytesLen - 1
markTombstone byte = 't'
)
var restoreChunkKeys = 10000 // non-const for testing
// ConsistentIndexGetter is an interface that wraps the Get method.
// Consistent index is the offset of an entry in a consistent replicated log.
type ConsistentIndexGetter interface {
// ConsistentIndex returns the consistent index of current executing entry.
ConsistentIndex() uint64
}
type store struct {
ReadView
WriteView
// mu read locks for txns and write locks for non-txn store changes.
mu sync.RWMutex
ig ConsistentIndexGetter
b backend.Backend
kvindex index
le lease.Lessor
// revMuLock protects currentRev and compactMainRev.
// Locked at end of write txn and released after write txn unlock lock.
// Locked before locking read txn and released after locking.
revMu sync.RWMutex
// currentRev is the revision of the last completed transaction.
currentRev int64
// compactMainRev is the main revision of the last compaction.
compactMainRev int64
// bytesBuf8 is a byte slice of length 8
// to avoid a repetitive allocation in saveIndex.
bytesBuf8 []byte
fifoSched schedule.Scheduler
stopc chan struct{}
}
// NewStore returns a new store. It is useful to create a store inside
// mvcc pkg. It should only be used for testing externally.
func NewStore(b backend.Backend, le lease.Lessor, ig ConsistentIndexGetter) *store {
s := &store{
b: b,
ig: ig,
kvindex: newTreeIndex(),
le: le,
currentRev: 1,
compactMainRev: -1,
bytesBuf8: make([]byte, 8),
fifoSched: schedule.NewFIFOScheduler(),
stopc: make(chan struct{}),
}
s.ReadView = &readView{s}
s.WriteView = &writeView{s}
if s.le != nil {
s.le.SetRangeDeleter(func() lease.TxnDelete { return s.Write() })
}
tx := s.b.BatchTx()
tx.Lock()
tx.UnsafeCreateBucket(keyBucketName)
tx.UnsafeCreateBucket(metaBucketName)
tx.Unlock()
s.b.ForceCommit()
if err := s.restore(); err != nil {
// TODO: return the error instead of panic here?
panic("failed to recover store from backend")
}
return s
}
func (s *store) compactBarrier(ctx context.Context, ch chan struct{}) {
if ctx == nil || ctx.Err() != nil {
s.mu.Lock()
select {
case <-s.stopc:
default:
f := func(ctx context.Context) { s.compactBarrier(ctx, ch) }
s.fifoSched.Schedule(f)
}
s.mu.Unlock()
return
}
close(ch)
}
func (s *store) Hash() (hash uint32, revision int64, err error) {
s.b.ForceCommit()
h, err := s.b.Hash(DefaultIgnores)
return h, s.currentRev, err
}
func (s *store) Compact(rev int64) (<-chan struct{}, error) {
s.mu.Lock()
defer s.mu.Unlock()
s.revMu.Lock()
defer s.revMu.Unlock()
if rev <= s.compactMainRev {
ch := make(chan struct{})
f := func(ctx context.Context) { s.compactBarrier(ctx, ch) }
s.fifoSched.Schedule(f)
return ch, ErrCompacted
}
if rev > s.currentRev {
return nil, ErrFutureRev
}
start := time.Now()
s.compactMainRev = rev
rbytes := newRevBytes()
revToBytes(revision{main: rev}, rbytes)
tx := s.b.BatchTx()
tx.Lock()
tx.UnsafePut(metaBucketName, scheduledCompactKeyName, rbytes)
tx.Unlock()
// ensure that desired compaction is persisted
s.b.ForceCommit()
keep := s.kvindex.Compact(rev)
ch := make(chan struct{})
var j = func(ctx context.Context) {
if ctx.Err() != nil {
s.compactBarrier(ctx, ch)
return
}
if !s.scheduleCompaction(rev, keep) {
s.compactBarrier(nil, ch)
return
}
close(ch)
}
s.fifoSched.Schedule(j)
indexCompactionPauseDurations.Observe(float64(time.Since(start) / time.Millisecond))
return ch, nil
}
// DefaultIgnores is a map of keys to ignore in hash checking.
var DefaultIgnores map[backend.IgnoreKey]struct{}
func init() {
DefaultIgnores = map[backend.IgnoreKey]struct{}{
// consistent index might be changed due to v2 internal sync, which
// is not controllable by the user.
{Bucket: string(metaBucketName), Key: string(consistentIndexKeyName)}: {},
}
}
func (s *store) Commit() {
s.mu.Lock()
defer s.mu.Unlock()
tx := s.b.BatchTx()
tx.Lock()
s.saveIndex(tx)
tx.Unlock()
s.b.ForceCommit()
}
func (s *store) Restore(b backend.Backend) error {
s.mu.Lock()
defer s.mu.Unlock()
close(s.stopc)
s.fifoSched.Stop()
s.b = b
s.kvindex = newTreeIndex()
s.currentRev = 1
s.compactMainRev = -1
s.fifoSched = schedule.NewFIFOScheduler()
s.stopc = make(chan struct{})
return s.restore()
}
func (s *store) restore() error {
reportDbTotalSizeInBytesMu.Lock()
b := s.b
reportDbTotalSizeInBytes = func() float64 { return float64(b.Size()) }
reportDbTotalSizeInBytesMu.Unlock()
min, max := newRevBytes(), newRevBytes()
revToBytes(revision{main: 1}, min)
revToBytes(revision{main: math.MaxInt64, sub: math.MaxInt64}, max)
keyToLease := make(map[string]lease.LeaseID)
// restore index
tx := s.b.BatchTx()
tx.Lock()
_, finishedCompactBytes := tx.UnsafeRange(metaBucketName, finishedCompactKeyName, nil, 0)
if len(finishedCompactBytes) != 0 {
s.compactMainRev = bytesToRev(finishedCompactBytes[0]).main
plog.Printf("restore compact to %d", s.compactMainRev)
}
_, scheduledCompactBytes := tx.UnsafeRange(metaBucketName, scheduledCompactKeyName, nil, 0)
scheduledCompact := int64(0)
if len(scheduledCompactBytes) != 0 {
scheduledCompact = bytesToRev(scheduledCompactBytes[0]).main
}
// index keys concurrently as they're loaded in from tx
rkvc, revc := restoreIntoIndex(s.kvindex)
for {
keys, vals := tx.UnsafeRange(keyBucketName, min, max, int64(restoreChunkKeys))
if len(keys) == 0 {
break
}
// rkvc blocks if the total pending keys exceeds the restore
// chunk size to keep keys from consuming too much memory.
restoreChunk(rkvc, keys, vals, keyToLease)
if len(keys) < restoreChunkKeys {
// partial set implies final set
break
}
// next set begins after where this one ended
newMin := bytesToRev(keys[len(keys)-1][:revBytesLen])
newMin.sub++
revToBytes(newMin, min)
}
close(rkvc)
s.currentRev = <-revc
// keys in the range [compacted revision -N, compaction] might all be deleted due to compaction.
// the correct revision should be set to compaction revision in the case, not the largest revision
// we have seen.
if s.currentRev < s.compactMainRev {
s.currentRev = s.compactMainRev
}
if scheduledCompact <= s.compactMainRev {
scheduledCompact = 0
}
for key, lid := range keyToLease {
if s.le == nil {
panic("no lessor to attach lease")
}
err := s.le.Attach(lid, []lease.LeaseItem{{Key: key}})
if err != nil {
plog.Errorf("unexpected Attach error: %v", err)
}
}
tx.Unlock()
if scheduledCompact != 0 {
s.Compact(scheduledCompact)
plog.Printf("resume scheduled compaction at %d", scheduledCompact)
}
return nil
}
type revKeyValue struct {
key []byte
kv mvccpb.KeyValue
kstr string
}
func restoreIntoIndex(idx index) (chan<- revKeyValue, <-chan int64) {
rkvc, revc := make(chan revKeyValue, restoreChunkKeys), make(chan int64, 1)
go func() {
currentRev := int64(1)
defer func() { revc <- currentRev }()
// restore the tree index from streaming the unordered index.
kiCache := make(map[string]*keyIndex, restoreChunkKeys)
for rkv := range rkvc {
ki, ok := kiCache[rkv.kstr]
// purge kiCache if many keys but still missing in the cache
if !ok && len(kiCache) >= restoreChunkKeys {
i := 10
for k := range kiCache {
delete(kiCache, k)
if i--; i == 0 {
break
}
}
}
// cache miss, fetch from tree index if there
if !ok {
ki = &keyIndex{key: rkv.kv.Key}
if idxKey := idx.KeyIndex(ki); idxKey != nil {
kiCache[rkv.kstr], ki = idxKey, idxKey
ok = true
}
}
rev := bytesToRev(rkv.key)
currentRev = rev.main
if ok {
if isTombstone(rkv.key) {
ki.tombstone(rev.main, rev.sub)
continue
}
ki.put(rev.main, rev.sub)
} else if !isTombstone(rkv.key) {
ki.restore(revision{rkv.kv.CreateRevision, 0}, rev, rkv.kv.Version)
idx.Insert(ki)
kiCache[rkv.kstr] = ki
}
}
}()
return rkvc, revc
}
func restoreChunk(kvc chan<- revKeyValue, keys, vals [][]byte, keyToLease map[string]lease.LeaseID) {
for i, key := range keys {
rkv := revKeyValue{key: key}
if err := rkv.kv.Unmarshal(vals[i]); err != nil {
plog.Fatalf("cannot unmarshal event: %v", err)
}
rkv.kstr = string(rkv.kv.Key)
if isTombstone(key) {
delete(keyToLease, rkv.kstr)
} else if lid := lease.LeaseID(rkv.kv.Lease); lid != lease.NoLease {
keyToLease[rkv.kstr] = lid
} else {
delete(keyToLease, rkv.kstr)
}
kvc <- rkv
}
}
func (s *store) Close() error {
close(s.stopc)
s.fifoSched.Stop()
return nil
}
func (a *store) Equal(b *store) bool {
if a.currentRev != b.currentRev {
return false
}
if a.compactMainRev != b.compactMainRev {
return false
}
return a.kvindex.Equal(b.kvindex)
}
func (s *store) saveIndex(tx backend.BatchTx) {
if s.ig == nil {
return
}
bs := s.bytesBuf8
binary.BigEndian.PutUint64(bs, s.ig.ConsistentIndex())
// put the index into the underlying backend
// tx has been locked in TxnBegin, so there is no need to lock it again
tx.UnsafePut(metaBucketName, consistentIndexKeyName, bs)
}
func (s *store) ConsistentIndex() uint64 {
// TODO: cache index in a uint64 field?
tx := s.b.BatchTx()
tx.Lock()
defer tx.Unlock()
_, vs := tx.UnsafeRange(metaBucketName, consistentIndexKeyName, nil, 0)
if len(vs) == 0 {
return 0
}
return binary.BigEndian.Uint64(vs[0])
}
// appendMarkTombstone appends tombstone mark to normal revision bytes.
func appendMarkTombstone(b []byte) []byte {
if len(b) != revBytesLen {
plog.Panicf("cannot append mark to non normal revision bytes")
}
return append(b, markTombstone)
}
// isTombstone checks whether the revision bytes is a tombstone.
func isTombstone(b []byte) bool {
return len(b) == markedRevBytesLen && b[markBytePosition] == markTombstone
}
// revBytesRange returns the range of revision bytes at
// the given revision.
func revBytesRange(rev revision) (start, end []byte) {
start = newRevBytes()
revToBytes(rev, start)
end = newRevBytes()
endRev := revision{main: rev.main, sub: rev.sub + 1}
revToBytes(endRev, end)
return start, end
}