From 2171f6409f7157888df9637a635664c67b7ca844 Mon Sep 17 00:00:00 2001
From: benclive <ben.clive@grafana.com>
Date: Tue, 28 May 2024 09:47:34 +0100
Subject: [PATCH] fix: Fix panic on requesting out-of-order Pattern samples
 (#13010)

---
 pkg/pattern/drain/chunk.go      |  8 ++++++++
 pkg/pattern/drain/chunk_test.go | 26 ++++++++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/pkg/pattern/drain/chunk.go b/pkg/pattern/drain/chunk.go
index 9b1e34e2e3a1..133329946758 100644
--- a/pkg/pattern/drain/chunk.go
+++ b/pkg/pattern/drain/chunk.go
@@ -66,6 +66,11 @@ func (c Chunk) ForRange(start, end, step model.Time) []logproto.PatternSample {
 			return c.Samples[i].Timestamp >= end
 		})
 	}
+
+	if c.Samples[lo].Timestamp > c.Samples[hi-1].Timestamp {
+		return nil
+	}
+
 	if step == TimeResolution {
 		return c.Samples[lo:hi]
 	}
@@ -110,6 +115,9 @@ func (c *Chunks) Add(ts model.Time) {
 		*c = append(*c, newChunk(t))
 		return
 	}
+	if ts.Before(last.Samples[len(last.Samples)-1].Timestamp) {
+		return
+	}
 	last.Samples = append(last.Samples, logproto.PatternSample{
 		Timestamp: t,
 		Value:     1,
diff --git a/pkg/pattern/drain/chunk_test.go b/pkg/pattern/drain/chunk_test.go
index 4863a6629729..17429da594e1 100644
--- a/pkg/pattern/drain/chunk_test.go
+++ b/pkg/pattern/drain/chunk_test.go
@@ -21,6 +21,9 @@ func TestAdd(t *testing.T) {
 	cks.Add(model.TimeFromUnixNano(time.Hour.Nanoseconds()) + TimeResolution + 1)
 	require.Equal(t, 2, len(cks))
 	require.Equal(t, 1, len(cks[1].Samples))
+	cks.Add(model.TimeFromUnixNano(time.Hour.Nanoseconds()) - TimeResolution)
+	require.Equal(t, 2, len(cks))
+	require.Equalf(t, 1, len(cks[1].Samples), "Older samples should not be added if they arrive out of order")
 }
 
 func TestIterator(t *testing.T) {
@@ -52,6 +55,7 @@ func TestForRange(t *testing.T) {
 		c        *Chunk
 		start    model.Time
 		end      model.Time
+		step     model.Time
 		expected []logproto.PatternSample
 	}{
 		{
@@ -180,6 +184,28 @@ func TestForRange(t *testing.T) {
 				{Timestamp: 4, Value: 10},
 			},
 		},
+		{
+			name: "Out-of-order samples generate nil result",
+			c: &Chunk{Samples: []logproto.PatternSample{
+				{Timestamp: 5, Value: 2},
+				{Timestamp: 3, Value: 2},
+			}},
+			start:    4,
+			end:      6,
+			expected: nil,
+		},
+		{
+			name: "Internally out-of-order samples generate nil result",
+			c: &Chunk{Samples: []logproto.PatternSample{
+				{Timestamp: 1, Value: 2},
+				{Timestamp: 5, Value: 2},
+				{Timestamp: 3, Value: 2},
+				{Timestamp: 7, Value: 2},
+			}},
+			start:    2,
+			end:      6,
+			expected: nil,
+		},
 	}
 
 	for _, tc := range testCases {