From ff0dc757587cada63ca948d2d5eb00bf090d63e0 Mon Sep 17 00:00:00 2001
From: Ganesh Vernekar <15064823+codesome@users.noreply.github.com>
Date: Thu, 14 Jul 2022 13:58:03 +0530
Subject: [PATCH] Replay WBL even if OOO Time Window is 0 (#296)

* Replay WBL even if OOO Time Window is 0

Signed-off-by: Ganesh Vernekar <ganeshvern@gmail.com>

* Apply feedback

Signed-off-by: Ganesh Vernekar <ganeshvern@gmail.com>
---
 tsdb/db.go      |  7 +++++-
 tsdb/db_test.go | 61 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 67 insertions(+), 1 deletion(-)

diff --git a/tsdb/db.go b/tsdb/db.go
index f2ddd454f..f14cb974f 100644
--- a/tsdb/db.go
+++ b/tsdb/db.go
@@ -787,7 +787,12 @@ func open(dir string, l log.Logger, r prometheus.Registerer, opts *Options, rngs
 		if err != nil {
 			return nil, err
 		}
-		if opts.OutOfOrderTimeWindow > 0 {
+		// Check if there is a WBL on disk, in which case we should replay that data.
+		wblSize, err := fileutil.DirSize(wblDir)
+		if err != nil && !os.IsNotExist(err) {
+			return nil, err
+		}
+		if opts.OutOfOrderTimeWindow > 0 || wblSize > 0 {
 			wblog, err = wal.NewSize(l, r, wblDir, segmentSize, opts.WALCompression)
 			if err != nil {
 				return nil, err
diff --git a/tsdb/db_test.go b/tsdb/db_test.go
index 436f0ac10..4b01a3534 100644
--- a/tsdb/db_test.go
+++ b/tsdb/db_test.go
@@ -5291,3 +5291,64 @@ func TestNoGapAfterRestartWithOOO(t *testing.T) {
 		})
 	}
 }
+
+func TestWblReplayAfterOOODisableAndRestart(t *testing.T) {
+	dir := t.TempDir()
+
+	opts := DefaultOptions()
+	opts.OutOfOrderTimeWindow = 60 * time.Minute.Milliseconds()
+	opts.AllowOverlappingQueries = true
+	opts.AllowOverlappingCompaction = true
+
+	db, err := Open(dir, nil, nil, opts, nil)
+	require.NoError(t, err)
+	db.DisableCompactions()
+	t.Cleanup(func() {
+		require.NoError(t, db.Close())
+	})
+
+	series1 := labels.FromStrings("foo", "bar1")
+	var allSamples []tsdbutil.Sample
+	addSamples := func(fromMins, toMins int64) {
+		app := db.Appender(context.Background())
+		for min := fromMins; min <= toMins; min++ {
+			ts := min * time.Minute.Milliseconds()
+			_, err := app.Append(0, series1, ts, float64(ts))
+			require.NoError(t, err)
+			allSamples = append(allSamples, sample{t: ts, v: float64(ts)})
+		}
+		require.NoError(t, app.Commit())
+	}
+
+	// In-order samples.
+	addSamples(290, 300)
+	// OOO samples.
+	addSamples(250, 260)
+
+	verifySamples := func(expSamples []tsdbutil.Sample) {
+		sort.Slice(expSamples, func(i, j int) bool {
+			return expSamples[i].T() < expSamples[j].T()
+		})
+
+		expRes := map[string][]tsdbutil.Sample{
+			series1.String(): expSamples,
+		}
+
+		q, err := db.Querier(context.Background(), math.MinInt64, math.MaxInt64)
+		require.NoError(t, err)
+
+		actRes := query(t, q, labels.MustNewMatcher(labels.MatchRegexp, "foo", "bar.*"))
+		require.Equal(t, expRes, actRes)
+	}
+
+	verifySamples(allSamples)
+
+	// Restart DB with OOO disabled.
+	require.NoError(t, db.Close())
+	opts.OutOfOrderTimeWindow = 0
+	db, err = Open(db.dir, nil, nil, opts, nil)
+	require.NoError(t, err)
+
+	// We can still query OOO samples when OOO is disabled.
+	verifySamples(allSamples)
+}