Merge pull request #2731 from brancz/lset-non-cloned

notifier: clone and not reuse LabelSet in AM discovery

notifier/notifier.go

@@ -500,6 +500,7 @@ func alertmanagerFromGroup(tg *config.TargetGroup, cfg *config.AlertmanagerConfi
 	var res []alertmanager
 
 	for _, lset := range tg.Targets {
+		lset = lset.Clone()
 		// Set configured scheme as the initial scheme label for overwrite.
 		lset[model.SchemeLabel] = model.LabelValue(cfg.Scheme)
 		lset[pathLabel] = model.LabelValue(postPath(cfg.PathPrefix))
@@ -510,7 +511,8 @@ func alertmanagerFromGroup(tg *config.TargetGroup, cfg *config.AlertmanagerConfi
 				lset[ln] = lv
 			}
 		}
-		lset := relabel.Process(lset, cfg.RelabelConfigs...)
+
+		lset = relabel.Process(lset, cfg.RelabelConfigs...)
 		if lset == nil {
 			continue
 		}

notifier/notifier_test.go

@@ -418,3 +418,30 @@ type alertmanagerMock struct {
 func (a alertmanagerMock) url() string {
 	return a.urlf()
 }
+
+func TestLabelSetNotReused(t *testing.T) {
+	tg := makeInputTargetGroup()
+	_, err := alertmanagerFromGroup(tg, &config.AlertmanagerConfig{})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if !reflect.DeepEqual(tg, makeInputTargetGroup()) {
+		t.Fatal("Target modified during alertmanager extraction")
+	}
+}
+
+func makeInputTargetGroup() *config.TargetGroup {
+	return &config.TargetGroup{
+		Targets: []model.LabelSet{
+			model.LabelSet{
+				model.AddressLabel:            model.LabelValue("1.1.1.1:9090"),
+				model.LabelName("notcommon1"): model.LabelValue("label"),
+			},
+		},
+		Labels: model.LabelSet{
+			model.LabelName("common"): model.LabelValue("label"),
+		},
+		Source: "testsource",
+	}
+}