mvcc: add TestHashKVWhenCompacting to kvstore_test

mvcc/kvstore_test.go

@@ -22,6 +22,8 @@ import (
 	mrand "math/rand"
 	"os"
 	"reflect"
+	"strconv"
+	"sync"
 	"testing"
 	"time"
 
@@ -510,6 +512,82 @@ func TestRestoreContinueUnfinishedCompaction(t *testing.T) {
 	t.Errorf("key for rev %+v still exists, want deleted", bytesToRev(revbytes))
 }
 
+// TestHashKVWhenCompacting ensures that HashKV returns correct hash when compacting.
+func TestHashKVWhenCompacting(t *testing.T) {
+	b, tmpPath := backend.NewDefaultTmpBackend()
+	s := NewStore(b, &lease.FakeLessor{}, nil)
+	defer os.Remove(tmpPath)
+
+	rev := 1000
+	for i := 2; i <= rev; i++ {
+		s.Put([]byte("foo"), []byte("bar"+strconv.Itoa(i)), lease.NoLease)
+	}
+
+	hashCompactc := make(chan struct {
+		hash       uint32
+		compactRev int64
+	}, 1)
+
+	donec := make(chan struct{})
+	var wg sync.WaitGroup
+	for i := 0; i < 10; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			for {
+				hash, _, compactRev, err := s.HashByRev(int64(rev))
+				if err != nil {
+					t.Fatal(err)
+				}
+				select {
+				case <-donec:
+					return
+				case hashCompactc <- struct {
+					hash       uint32
+					compactRev int64
+				}{hash, compactRev}:
+				}
+			}
+		}()
+	}
+
+	go func() {
+		defer close(donec)
+		revHash := make(map[int64]uint32)
+		for round := 0; round < 1000; round++ {
+			select {
+			case r := <-hashCompactc:
+				if revHash[r.compactRev] == 0 {
+					revHash[r.compactRev] = r.hash
+					break
+				}
+				if r.hash != revHash[r.compactRev] {
+					t.Fatalf("Hashes differ (current %v) != (saved %v)", r.hash, revHash[r.compactRev])
+				}
+			}
+		}
+	}()
+
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		for i := 100; i >= 0; i-- {
+			_, err := s.Compact(int64(rev - 1 - i))
+			if err != nil {
+				t.Fatal(err)
+			}
+			time.Sleep(10)
+		}
+	}()
+
+	select {
+	case <-donec:
+		wg.Wait()
+	case <-time.After(10 * time.Second):
+		testutil.FatalStack(t, "timeout")
+	}
+}
+
 func TestTxnPut(t *testing.T) {
 	// assign arbitrary size
 	bytesN := 30