From ae711852559722dbad0797195a89fd39ee0d2324 Mon Sep 17 00:00:00 2001
From: Bryan Boreham <bjboreham@gmail.com>
Date: Wed, 7 Jan 2026 14:56:10 +0000
Subject: [PATCH 1/2] Scraping: add a test for relabel with keep and drop
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Marvin Rösch <marvinroesch99@gmail.com>
Signed-off-by: Bryan Boreham <bjboreham@gmail.com>
---
 scrape/scrape_test.go | 44 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/scrape/scrape_test.go b/scrape/scrape_test.go
index eab1499158..270d1909dd 100644
--- a/scrape/scrape_test.go
+++ b/scrape/scrape_test.go
@@ -5982,3 +5982,47 @@ func TestScrapeLoopDisableStalenessMarkerInjection(t *testing.T) {
 		}
 	}
 }
+
+func TestDropsSeriesFromRelabeling(t *testing.T) {
+	s := teststorage.New(t)
+	defer s.Close()
+	ctx := t.Context()
+
+	target := &Target{}
+	relabelConfig := []*relabel.Config{
+		{
+			SourceLabels: model.LabelNames{"__name__"},
+			Regex:        relabel.MustNewRegexp(".*_total$"),
+			Action:       relabel.Keep,
+		},
+		{
+			SourceLabels: model.LabelNames{"__name__"},
+			Regex:        relabel.MustNewRegexp("test_metric_2_total$"),
+			Action:       relabel.Drop,
+		},
+	}
+	metricsText := []byte(`
+# HELP test_metric_1_total This is a counter
+# TYPE test_metric_1_total counter
+test_metric_1_total 123
+# HELP test_metric_2_total This is a counter
+# TYPE test_metric_2_total counter
+test_metric_2_total 234
+# HELP disk_usage_bytes This is a gauge
+# TYPE disk_usage_bytes gauge
+disk_usage_bytes 456
+`)
+
+	sl := newBasicScrapeLoop(t, ctx, &testScraper{}, s.Appender, 0)
+	sl.sampleMutator = func(l labels.Labels) labels.Labels {
+		return mutateSampleLabels(l, target, true, relabelConfig)
+	}
+
+	slApp := sl.appender(ctx)
+	total, added, seriesAdded, err := sl.append(slApp, metricsText, "text/plain", time.Time{})
+	require.NoError(t, err)
+	require.NoError(t, slApp.Rollback())
+	require.Equal(t, 3, total)
+	require.Equal(t, 1, added)
+	require.Equal(t, 1, seriesAdded)
+}

From 66c8e31956777630949b1be5009d1a7e6de83921 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marvin=20R=C3=B6sch?= <marvinroesch99@gmail.com>
Date: Wed, 7 Jan 2026 15:27:01 +0100
Subject: [PATCH 2/2] [BUGFIX] Scraping: drop sample if relabeling config says
 so
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Signed-off-by: Marvin Rösch <marvinroesch99@gmail.com>
---
 scrape/scrape.go | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/scrape/scrape.go b/scrape/scrape.go
index b653873bad..a8cd15d30c 100644
--- a/scrape/scrape.go
+++ b/scrape/scrape.go
@@ -716,7 +716,9 @@ func mutateSampleLabels(lset labels.Labels, target *Target, honor bool, rc []*re
 		}
 	}
 
-	relabel.ProcessBuilder(lb, rc...)
+	if keep := relabel.ProcessBuilder(lb, rc...); !keep {
+		return labels.EmptyLabels()
+	}
 
 	return lb.Labels()
 }