fix: infinite loop in index writer

pkg/model/labels_test.go

@@ -68,6 +68,42 @@ func TestLabelsUnique(t *testing.T) {
 	}
 }
 
+func Test_LabelsBuilder_Unique(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    Labels
+		add      Labels
+		expected Labels
+	}{
+		{
+			name: "duplicates in input are preserved",
+			input: Labels{
+				{Name: "unique", Value: "yes"},
+				{Name: "unique", Value: "no"},
+			},
+			add: Labels{
+				{Name: "foo", Value: "bar"},
+				{Name: "foo", Value: "baz"},
+			},
+			expected: Labels{
+				{Name: "foo", Value: "baz"},
+				{Name: "unique", Value: "yes"},
+				{Name: "unique", Value: "no"},
+			},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			builder := NewLabelsBuilder(test.input)
+			for _, l := range test.add {
+				builder.Set(l.Name, l.Value)
+			}
+			assert.Equal(t, test.expected, builder.Labels())
+		})
+	}
+}
+
 func TestLabels_SessionID_Order(t *testing.T) {
 	input := []Labels{
 		{

pkg/phlaredb/labels/labels.go

@@ -60,6 +60,7 @@ func CreateProfileLabels(enforceOrder bool, p *profilev1.Profile, externalLabels
 		} else {
 			sort.Sort(lbs)
 		}
+		lbs = lbs.Unique()
 		profilesLabels[pos] = lbs
 		seriesRefs[pos] = model.Fingerprint(lbs.Hash())
 

pkg/phlaredb/phlaredb_test.go

@@ -281,6 +281,35 @@ func TestMergeProfilesStacktraces(t *testing.T) {
 	})
 }
 
+// See https://github.com/grafana/pyroscope/pull/3356
+func Test_HeadFlush_DuplicateLabels(t *testing.T) {
+	defer goleak.VerifyNone(t, goleak.IgnoreCurrent())
+
+	// ingest some sample data
+	var (
+		ctx     = testContext(t)
+		testDir = contextDataDir(ctx)
+		end     = time.Unix(0, int64(time.Hour))
+		start   = end.Add(-time.Minute)
+		step    = 15 * time.Second
+	)
+
+	db, err := New(ctx, Config{
+		DataPath:         testDir,
+		MaxBlockDuration: time.Duration(100000) * time.Minute,
+	}, NoLimit, ctx.localBucketClient)
+	require.NoError(t, err)
+	defer func() {
+		require.NoError(t, db.Close())
+	}()
+
+	ingestProfiles(t, db, cpuProfileGenerator, start.UnixNano(), end.UnixNano(), step,
+		&typesv1.LabelPair{Name: "namespace", Value: "my-namespace"},
+		&typesv1.LabelPair{Name: "pod", Value: "my-pod"},
+		&typesv1.LabelPair{Name: "pod", Value: "not-my-pod"},
+	)
+}
+
 func TestMergeProfilesPprof(t *testing.T) {
 	defer goleak.VerifyNone(t, goleak.IgnoreCurrent())
 

pkg/phlaredb/tsdb/index/index.go

@@ -942,7 +942,10 @@ func (w *Writer) writePostingsToTmpFiles() error {
 		// using more memory than a single label name can.
 		for len(names) > 0 {
 			if w.labelNames[names[0]]+c > maxPostings {
-				break
+				if c > 0 {
+					break
+				}
+				return fmt.Errorf("corruption detected when writing postings to index: label %q has %d uses, but maxPostings is %d", names[0], w.labelNames[names[0]], maxPostings)
 			}
 			batchNames = append(batchNames, names[0])
 			c += w.labelNames[names[0]]
@@ -1016,7 +1019,6 @@ func (w *Writer) writePostingsToTmpFiles() error {
 			return w.ctx.Err()
 		default:
 		}
-
 	}
 	return nil
 }

pkg/phlaredb/tsdb/index/index_test.go

@@ -584,3 +584,18 @@ func TestDecoder_Postings_WrongInput(t *testing.T) {
 	_, _, err := (&Decoder{}).Postings([]byte("the cake is a lie"))
 	require.Error(t, err)
 }
+
+func TestWriter_ShouldReturnErrorOnSeriesWithDuplicatedLabelNames(t *testing.T) {
+	w, err := NewWriter(context.Background(), filepath.Join(t.TempDir(), "index"))
+	require.NoError(t, err)
+
+	require.NoError(t, w.AddSymbol("__name__"))
+	require.NoError(t, w.AddSymbol("metric_1"))
+	require.NoError(t, w.AddSymbol("metric_2"))
+
+	require.NoError(t, w.AddSeries(0, phlaremodel.LabelsFromStrings("__name__", "metric_1", "__name__", "metric_2"), 0))
+
+	err = w.Close()
+	require.Error(t, err)
+	require.ErrorContains(t, err, "corruption detected when writing postings to index")
+}