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

etcdserver/api/v3rpc/maintenance.go

@@ -128,11 +128,24 @@ func (ms *maintenanceServer) Snapshot(sr *pb.SnapshotRequest, srv pb.Maintenance
 }
 
 func (ms *maintenanceServer) Hash(ctx context.Context, r *pb.HashRequest) (*pb.HashResponse, error) {
-	h, compactRev, err := ms.kg.KV().HashByRev(r.Revision)
+	var (
+		h          uint32
+		rev        int64
+		compactRev int64
+		err        error
+	)
+
+	if r.Revision == 0 {
+		h, rev, err = ms.kg.KV().Hash()
+	} else {
+		h, rev, compactRev, err = ms.kg.KV().HashByRev(r.Revision)
+	}
+
 	if err != nil {
 		return nil, togRPCError(err)
 	}
-	resp := &pb.HashResponse{Header: &pb.ResponseHeader{}, Hash: h, CompactRevision: compactRev}
+
+	resp := &pb.HashResponse{Header: &pb.ResponseHeader{Revision: rev}, Hash: h, CompactRevision: compactRev}
 	ms.hdr.fill(resp.Header)
 	return resp, nil
 }

mvcc/backend/backend.go

@@ -52,6 +52,9 @@ type Backend interface {
 
 	Snapshot() Snapshot
 	Hash(ignores map[IgnoreKey]struct{}) (uint32, error)
+	// HashBucket hashes key value pairs of the given bucket.
+	// the func f determines whether the key should be hashed or not.
+	HashBucket(bucket []byte, f func(key []byte) bool) (uint32, error)
 	// Size returns the current size of the backend.
 	Size() int64
 	Defrag() error
@@ -240,6 +243,37 @@ 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 +107,12 @@ 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 computes the hash of the KV's backend.
 	Hash() (hash uint32, revision int64, err error)
 
+	// HashByRev computes the hash of all MVCC keys up to a given revision.
+	HashByRev(rev int64) (hash uint32, revision int64, compactRev int64, err error)
+
 	// Compact frees all superseded keys with revisions less than rev.
 	Compact(rev int64) (<-chan struct{}, error)
 

mvcc/kvstore.go

@@ -98,11 +98,15 @@ 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 +120,8 @@ 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 +165,42 @@ func (s *store) Hash() (hash uint32, revision int64, err error) {
 	return h, s.currentRev, err
 }
 
+func (s *store) HashByRev(rev int64) (hash uint32, currentRev int64, 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, 0, compactMainRev, ErrCompacted
+		} else if rev > currentRev {
+			return 0, currentRev, 0, ErrFutureRev
+		}
+		select {
+		case <-compactc:
+		case <-s.stopc:
+			return 0, 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.currentRev, s.compactMainRev, err
+}
+
 func (s *store) Compact(rev int64) (<-chan struct{}, error) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
@@ -192,6 +233,7 @@ 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()                                                {}