Function TestDiscardStatsMove

value_test.go:1071–1130

Regression test for https://github.com/dgraph-io/badger/issues/926

(t *testing.T)

// Regression test for https://github.com/dgraph-io/badger/issues/926
func TestDiscardStatsMove(t *testing.T) {
	dir, err := ioutil.TempDir("", "badger-test")
	require.NoError(t, err)
	ops := getTestOptions(dir)
	ops.ValueLogMaxEntries = 1
	db, err := Open(ops)
	require.NoError(t, err)

	stat := make(map[uint32]int64, ops.ValueThreshold+10)
	for i := uint32(0); i < uint32(ops.ValueThreshold+10); i++ {
		stat[i] = 0
	}

	db.vlog.lfDiscardStats.Lock()
	db.vlog.lfDiscardStats.m = stat
	encodedDS, _ := json.Marshal(db.vlog.lfDiscardStats.m)
	db.vlog.lfDiscardStats.Unlock()
	entries := []*Entry{{
		Key: y.KeyWithTs(lfDiscardStatsKey, 1),
		// The discard stat value is more than value threshold.
		Value: encodedDS,
	}}
	// Push discard stats entry to the write channel.
	req, err := db.sendToWriteCh(entries)
	require.NoError(t, err)
	req.Wait()

	// Unset discard stats. We've already pushed the stats. If we don't unset it then it will be
	// pushed again on DB close. Also, the first insertion was in vlog file 1, this insertion would
	// be in value log file 3.
	db.vlog.lfDiscardStats.Lock()
	db.vlog.lfDiscardStats.m = nil
	db.vlog.lfDiscardStats.Unlock()

	// Push more entries so that we get more than 1 value log files.
	require.NoError(t, db.Update(func(txn *Txn) error {
		e := NewEntry([]byte("f"), []byte("1"))
		return txn.SetEntry(e)
	}))
	require.NoError(t, db.Update(func(txn *Txn) error {
		e := NewEntry([]byte("ff"), []byte("1"))
		return txn.SetEntry(e)
	}))

	tr := trace.New("Badger.ValueLog", "GC")
	// Use first value log file for GC. This value log file contains the discard stats.
	lf := db.vlog.filesMap[0]
	require.NoError(t, db.vlog.rewrite(lf, tr))
	require.NoError(t, db.Close())

	db, err = Open(ops)
	// discardStats will be populate using vlog.populateDiscardStats(), which pushes discard stats
	// to vlog.lfDiscardStats.flushChan. Hence wait for some time, for discard stats to be updated.
	time.Sleep(1 * time.Second)
	require.NoError(t, err)
	db.vlog.lfDiscardStats.RLock()
	require.Equal(t, stat, db.vlog.lfDiscardStats.m)
	db.vlog.lfDiscardStats.RUnlock()