mvcc: allows mvcc/backend to hash kv state by rev

mvcc/backend/backend.go

@@ -52,6 +52,7 @@ type Backend interface {
 
 	Snapshot() Snapshot
 	Hash(ignores map[IgnoreKey]struct{}) (uint32, error)
+	HashBucket(bucket []byte, f func(rev []byte) bool) (uint32, error)
 	// Size returns the current size of the backend.
 	Size() int64
 	Defrag() error
@@ -240,6 +241,37 @@ func (b *backend) Hash(ignores map[IgnoreKey]struct{}) (uint32, error) {
 	return h.Sum32(), nil
 }
 
+func (b *backend) HashBucket(bucket []byte, f func(rev []byte) bool) (hash uint32, err error) {
+	h := crc32.New(crc32.MakeTable(crc32.Castagnoli))
+
+	b.mu.RLock()
+	defer b.mu.RUnlock()
+
+	err = b.db.View(func(tx *bolt.Tx) error {
+		b := tx.Bucket(bucket)
+		if b == nil {
+			return fmt.Errorf("bucket not found %v", string(bucket))
+		}
+		h.Write(bucket)
+		b.ForEach(func(k, v []byte) error {
+			if !f(k) {
+				return nil
+			}
+
+			h.Write(k)
+			h.Write(v)
+			return nil
+		})
+		return nil
+	})
+
+	if err != nil {
+		return 0, err
+	}
+
+	return h.Sum32(), nil
+}
+
 func (b *backend) Size() int64 {
 	return atomic.LoadInt64(&b.size)
 }

mvcc/kv.go

@@ -107,10 +107,14 @@ type KV interface {
 	// Write creates a write transaction.
 	Write() TxnWrite
 
-	// Hash retrieves the hash of KV state and revision.
-	// This method is designed for consistency checking purposes.
+	// Hash retrieves the hash of all states including leases.
+	// This method is designed to check consistency of all states.
 	Hash() (hash uint32, revision int64, err error)
 
+	// HashByRev retrieves the hash of the KV state at a revision.
+	// This method is designed to check consistency of the KV space.
+	HashByRev(rev int64) (hash uint32, compactRev int64, err error)
+
 	// Compact frees all superseded keys with revisions less than rev.
 	Compact(rev int64) (<-chan struct{}, error)
 

mvcc/kvstore.go

@@ -42,8 +42,12 @@ var (
 	ErrFutureRev = errors.New("mvcc: required revision is a future revision")
 	ErrCanceled  = errors.New("mvcc: watcher is canceled")
 	ErrClosed    = errors.New("mvcc: closed")
+	ErrTimeout   = errors.New("mvcc: req hash timeout")
 
 	plog = capnslog.NewPackageLogger("github.com/coreos/etcd", "mvcc")
+
+	// hashTimeout is the max waiting time on the ongoing compaction.
+	hashTimeout = time.Duration(10) * time.Second
 )
 
 const (
@@ -98,11 +102,15 @@ type store struct {
 	fifoSched schedule.Scheduler
 
 	stopc chan struct{}
+
+	compactc 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 {
+	closedc := make(chan struct{})
+	close(closedc)
 	s := &store{
 		b:       b,
 		ig:      ig,
@@ -116,7 +124,8 @@ func NewStore(b backend.Backend, le lease.Lessor, ig ConsistentIndexGetter) *sto
 		bytesBuf8: make([]byte, 8),
 		fifoSched: schedule.NewFIFOScheduler(),
 
-		stopc: make(chan struct{}),
+		stopc:    make(chan struct{}),
+		compactc: closedc,
 	}
 	s.ReadView = &readView{s}
 	s.WriteView = &writeView{s}
@@ -160,6 +169,42 @@ func (s *store) Hash() (hash uint32, revision int64, err error) {
 	return h, s.currentRev, err
 }
 
+func (s *store) HashByRev(rev int64) (hash uint32, compactRev int64, err error) {
+	for {
+		s.mu.RLock()
+		compactMainRev := s.compactMainRev
+		currentRev := s.currentRev
+		compactc := s.compactc
+		s.mu.RUnlock()
+		if rev < compactMainRev {
+			return 0, compactMainRev, ErrCompacted
+		} else if rev > currentRev {
+			return 0, compactMainRev, ErrFutureRev
+		}
+		select {
+		case <-compactc:
+		case <-s.stopc:
+			return 0, 0, ErrClosed
+		}
+		s.mu.Lock()
+		if s.compactc == compactc {
+			defer s.mu.Unlock()
+			break
+		}
+		s.mu.Unlock()
+	}
+	s.b.ForceCommit()
+
+	upper := revision{main: rev + 1}
+	f := func(r []byte) bool {
+		return upper.GreaterThan(bytesToRev(r))
+	}
+
+	hash, err = s.b.HashBucket(keyBucketName, f)
+
+	return hash, s.compactMainRev, err
+}
+
 func (s *store) Compact(rev int64) (<-chan struct{}, error) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
@@ -192,6 +237,7 @@ func (s *store) Compact(rev int64) (<-chan struct{}, error) {
 
 	keep := s.kvindex.Compact(rev)
 	ch := make(chan struct{})
+	s.compactc = ch
 	var j = func(ctx context.Context) {
 		if ctx.Err() != nil {
 			s.compactBarrier(ctx, ch)

mvcc/kvstore_test.go

@@ -638,6 +638,7 @@ type fakeBackend struct {
 func (b *fakeBackend) BatchTx() backend.BatchTx                                    { return b.tx }
 func (b *fakeBackend) ReadTx() backend.ReadTx                                      { return b.tx }
 func (b *fakeBackend) Hash(ignores map[backend.IgnoreKey]struct{}) (uint32, error) { return 0, nil }
+func (b *fakeBackend) HashBucket([]byte, func([]byte) bool) (uint32, error)        { return 0, nil }
 func (b *fakeBackend) Size() int64                                                 { return 0 }
 func (b *fakeBackend) Snapshot() backend.Snapshot                                  { return nil }
 func (b *fakeBackend) ForceCommit()                                                {}