Function TestSnapshotUnknownEncodingFallsBackToWAL

tsdb/head_test.go:5017–5097

TestSnapshotUnknownEncodingFallsBackToWAL verifies that a snapshot containing an unknown chunk encoding causes the entire snapshot load to fail and fall back to full WAL replay, recovering all series without data loss.

(t *testing.T)

// an unknown chunk encoding causes the entire snapshot load to fail and fall back
// to full WAL replay, recovering all series without data loss.
func TestSnapshotUnknownEncodingFallsBackToWAL(t *testing.T) {
	head, _ := newTestHead(t, 120*4, compression.None, false)
	defer func() {
		head.opts.EnableMemorySnapshotOnShutdown = false
		require.NoError(t, head.Close())
	}()

	floatHist := tsdbutil.GenerateTestGaugeFloatHistograms(1)[0]
	lblsFloatHist := labels.FromStrings("floathist", "bar")
	lblsFloat := labels.FromStrings("foo", "bar")

	app := head.Appender(context.Background())
	_, err := app.AppendHistogram(0, lblsFloatHist, 99, nil, floatHist)
	require.NoError(t, err)
	_, err = app.Append(0, lblsFloat, 99, 99.0)
	require.NoError(t, err)
	require.NoError(t, app.Commit())

	head.opts.EnableMemorySnapshotOnShutdown = true
	require.NoError(t, head.Close())

	// Find the snapshot and corrupt the encoding byte of the float histogram series.
	snapDir, _, _, err := LastChunkSnapshot(head.opts.ChunkDirRoot)
	require.NoError(t, err)

	sr, err := wlog.NewSegmentsReader(snapDir)
	require.NoError(t, err)
	r := wlog.NewReader(sr)
	syms := labels.NewSymbolTable()
	rdec := record.NewDecoder(syms, promslog.NewNopLogger())
	var (
		records [][]byte
		mutated bool
	)
	for r.Next() {
		rec := append([]byte(nil), r.Record()...)
		if rec[0] == chunkSnapshotRecordTypeSeries {
			buf := encoding.Decbuf{B: rec}
			_ = buf.Byte() // flag
			_ = buf.Be64() // ref
			lset := rdec.DecodeLabels(&buf)
			_ = buf.Be64int64() // chunkRange
			if buf.Uvarint() == 1 && lset.Get("floathist") == "bar" {
				_ = buf.Be64int64() // minTime
				_ = buf.Be64int64() // maxTime
				encPos := len(rec) - buf.Len()
				require.Equal(t, byte(chunkenc.EncFloatHistogram), rec[encPos],
					"expected float histogram encoding at computed offset")
				rec[encPos] = 0xFF
				mutated = true
			}
		}
		records = append(records, rec)
	}
	require.NoError(t, r.Err())
	require.NoError(t, sr.Close())
	require.True(t, mutated, "expected to find and corrupt the float histogram series record")