Merge pull request #3516 from xiang90/hash_improved

storage: support hash state

storage/kv.go

@@ -40,6 +40,10 @@ type KV interface {
 
 	Compact(rev int64) error
 
+	// Get the hash of KV state.
+	// This method is designed for consistency checking purpose.
+	Hash() (uint32, error)
+
 	// Write a snapshot to the given io writer
 	Snapshot(w io.Writer) (int64, error)
 

storage/kv_test.go

@@ -608,6 +608,28 @@ func TestKVCompactBad(t *testing.T) {
 	}
 }
 
+func TestKVHash(t *testing.T) {
+	hashes := make([]uint32, 3)
+
+	for i := 0; i < len(hashes); i++ {
+		var err error
+		kv := New(tmpPath)
+		kv.Put([]byte("foo0"), []byte("bar0"))
+		kv.Put([]byte("foo1"), []byte("bar0"))
+		hashes[i], err = kv.Hash()
+		if err != nil {
+			t.Fatalf("failed to get hash: %v", err)
+		}
+		cleanup(kv, tmpPath)
+	}
+
+	for i := 1; i < len(hashes); i++ {
+		if hashes[i-1] != hashes[i] {
+			t.Errorf("hash[%d](%d) != hash[%d](%d)", i-1, hashes[i-1], i, hashes[i])
+		}
+	}
+}
+
 func TestKVRestore(t *testing.T) {
 	tests := []func(kv KV){
 		func(kv KV) {

storage/kvstore.go

@@ -2,6 +2,7 @@ package storage
 
 import (
 	"errors"
+	"hash/crc32"
 	"io"
 	"log"
 	"math"
@@ -203,6 +204,15 @@ func (s *store) Compact(rev int64) error {
 	return nil
 }
 
+func (s *store) Hash() (uint32, error) {
+	h := crc32.New(crc32.MakeTable(crc32.Castagnoli))
+	_, err := s.Snapshot(h)
+	if err != nil {
+		return 0, err
+	}
+	return h.Sum32(), nil
+}
+
 func (s *store) Snapshot(w io.Writer) (int64, error) {
 	s.b.ForceCommit()
 	return s.b.Snapshot(w)