Enhance TestDB_Concurrent_WriteTo to check consistent read

Signed-off-by: Benjamin Wang <benjamin.ahrtr@gmail.com>

db_test.go

@@ -668,68 +668,95 @@ func TestDB_BeginRW(t *testing.T) {
 }
 
 // TestDB_Concurrent_WriteTo checks that issuing WriteTo operations concurrently
-// with commits does not produce corrupted db files.
-func TestDB_Concurrent_WriteTo(t *testing.T) {
-	o := &bolt.Options{NoFreelistSync: false}
+// with commits does not produce corrupted db files. It also verifies that all
+// readonly transactions, which are created based on the same data view, should
+// always read the same data.
+func TestDB_Concurrent_WriteTo_and_ConsistentRead(t *testing.T) {
+	o := &bolt.Options{
+		NoFreelistSync: false,
+		PageSize:       4096,
+	}
 	db := btesting.MustCreateDBWithOption(t, o)
 
+	wtxs, rtxs := 50, 5
+	bucketName := []byte("data")
+
+	var dataLock sync.Mutex
+	dataCache := make(map[int][]map[string]string)
+
 	var wg sync.WaitGroup
-	wtxs, rtxs := 5, 5
 	wg.Add(wtxs * rtxs)
-	f := func(tx *bolt.Tx) {
+	f := func(round int, tx *bolt.Tx) {
 		defer wg.Done()
-		f, err := os.CreateTemp("", "bolt-")
-		if err != nil {
-			panic(err)
-		}
-		time.Sleep(time.Duration(rand.Intn(20)+1) * time.Millisecond)
-		_, err = tx.WriteTo(f)
-		if err != nil {
-			panic(err)
-		}
+		time.Sleep(time.Duration(rand.Intn(200)+10) * time.Millisecond)
+		f := filepath.Join(t.TempDir(), fmt.Sprintf("%d-bolt-", round))
+		err := tx.CopyFile(f, 0600)
+		require.NoError(t, err)
+
+		// read all the data
+		b := tx.Bucket(bucketName)
+		data := make(map[string]string)
+		err = b.ForEach(func(k, v []byte) error {
+			data[string(k)] = string(v)
+			return nil
+		})
+		require.NoError(t, err)
+
+		// cache the data
+		dataLock.Lock()
+		dataSlice := dataCache[round]
+		dataSlice = append(dataSlice, data)
+		dataCache[round] = dataSlice
+		dataLock.Unlock()
+
 		err = tx.Rollback()
-		if err != nil {
-			panic(err)
-		}
-		f.Close()
+		require.NoError(t, err)
 
 		copyOpt := *o
-		snap := btesting.MustOpenDBWithOption(t, f.Name(), &copyOpt)
+		snap := btesting.MustOpenDBWithOption(t, f, &copyOpt)
 		defer snap.MustClose()
 		snap.MustCheck()
 	}
 
-	tx1, err := db.Begin(true)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if _, err := tx1.CreateBucket([]byte("abc")); err != nil {
-		t.Fatal(err)
-	}
-	if err := tx1.Commit(); err != nil {
-		t.Fatal(err)
-	}
+	err := db.Update(func(tx *bolt.Tx) error {
+		_, err := tx.CreateBucket(bucketName)
+		return err
+	})
+	require.NoError(t, err)
 
 	for i := 0; i < wtxs; i++ {
 		tx, err := db.Begin(true)
-		if err != nil {
-			t.Fatal(err)
-		}
-		if err := tx.Bucket([]byte("abc")).Put([]byte{0}, []byte{0}); err != nil {
-			t.Fatal(err)
-		}
+		require.NoError(t, err)
+
+		b := tx.Bucket(bucketName)
+
 		for j := 0; j < rtxs; j++ {
 			rtx, rerr := db.Begin(false)
-			if rerr != nil {
-				t.Fatal(rerr)
+			require.NoError(t, rerr)
+			go f(i, rtx)
+
+			for k := 0; k < 10; k++ {
+				key, value := fmt.Sprintf("key_%d", rand.Intn(10)), fmt.Sprintf("value_%d", rand.Intn(100))
+				perr := b.Put([]byte(key), []byte(value))
+				require.NoError(t, perr)
 			}
-			go f(rtx)
-		}
-		if err := tx.Commit(); err != nil {
-			t.Fatal(err)
 		}
+		err = tx.Commit()
+		require.NoError(t, err)
 	}
 	wg.Wait()
+
+	// compare the data. The data generated in the same round
+	// should be exactly the same.
+	for round, dataSlice := range dataCache {
+		data0 := dataSlice[0]
+
+		for i := 1; i < len(dataSlice); i++ {
+			datai := dataSlice[i]
+			same := reflect.DeepEqual(data0, datai)
+			require.True(t, same, fmt.Sprintf("found inconsistent data in round %d, data[0]: %v, data[%d] : %v", round, data0, i, datai))
+		}
+	}
 }
 
 // Ensure that opening a transaction while the DB is closed returns an error.