Meta labels sd 3693 (#3805)

Always keep the discovered labels up to date.

add test that DiscoveredLabels are always updated

scrape/scrape.go

@@ -301,6 +301,10 @@ func (sp *scrapePool) sync(targets []*Target) {
 			sp.loops[hash] = l
 
 			go l.run(interval, timeout, nil)
+		} else {
+			// Need to keep the most updated labels information
+			// for displaying it in the Service Discovery web page.
+			sp.targets[hash].SetDiscoveredLabels(t.DiscoveredLabels())
 		}
 	}
 

scrape/scrape_test.go

@@ -96,6 +96,40 @@ func TestDroppedTargetsList(t *testing.T) {
 	}
 }
 
+// TestDiscoveredLabelsUpdate checks that DiscoveredLabels are updated
+// even when new labels don't affect the target `hash`.
+func TestDiscoveredLabelsUpdate(t *testing.T) {
+
+	sp := &scrapePool{}
+	// These are used when syncing so need this to avoid a panic.
+	sp.config = &config.ScrapeConfig{
+		ScrapeInterval: model.Duration(1),
+		ScrapeTimeout:  model.Duration(1),
+	}
+	sp.targets = make(map[uint64]*Target)
+	t1 := &Target{
+		discoveredLabels: labels.Labels{
+			labels.Label{
+				Name:  "label",
+				Value: "name",
+			},
+		},
+	}
+	sp.targets[t1.hash()] = t1
+
+	t2 := &Target{
+		discoveredLabels: labels.Labels{
+			labels.Label{
+				Name:  "labelNew",
+				Value: "nameNew",
+			},
+		},
+	}
+	sp.sync([]*Target{t2})
+
+	testutil.Equals(t, t2.DiscoveredLabels(), sp.targets[t1.hash()].DiscoveredLabels())
+}
+
 type testLoop struct {
 	startFunc func(interval, timeout time.Duration, errc chan<- error)
 	stopFunc  func()

scrape/target.go

@@ -115,6 +115,11 @@ func (t *Target) DiscoveredLabels() labels.Labels {
 	return lset
 }
 
+// SetDiscoveredLabels sets new DiscoveredLabels
+func (t *Target) SetDiscoveredLabels(l labels.Labels) {
+	t.discoveredLabels = l
+}
+
 // URL returns a copy of the target's URL.
 func (t *Target) URL() *url.URL {
 	params := url.Values{}