Drop series for federation if latest sample is stale.

web/federate.go

@@ -26,6 +26,7 @@ import (
 
 	"github.com/prometheus/prometheus/pkg/labels"
 	"github.com/prometheus/prometheus/pkg/timestamp"
+	"github.com/prometheus/prometheus/pkg/value"
 	"github.com/prometheus/prometheus/promql"
 	"github.com/prometheus/prometheus/storage"
 )
@@ -99,6 +100,13 @@ func (h *Handler) federation(w http.ResponseWriter, req *http.Request) {
 				continue
 			}
 		}
+		// The exposition formats do not support stale markers, so drop them. This
+		// is good enough for staleness handling of federated data, as the
+		// interval-based limits on staleness will do the right thing for supported
+		// use cases (which is to say federating aggregated time series).
+		if value.IsStaleNaN(v) {
+			continue
+		}
 
 		vec = append(vec, promql.Sample{
 			Metric: s.Labels(),

web/federate_test.go

@@ -75,6 +75,18 @@ test_metric2{foo="boo",instance="i"} 1 6000000
 		code:   200,
 		body: `# TYPE test_metric_without_labels untyped
 test_metric_without_labels{instance=""} 1001 6000000
+`,
+	},
+	"test_stale_metric": {
+		params: "match[]=test_metric_stale",
+		code:   200,
+		body:   ``,
+	},
+	"test_old_metric": {
+		params: "match[]=test_metric_old",
+		code:   200,
+		body: `# TYPE test_metric_old untyped
+test_metric_old{instance=""} 981 5880000
 `,
 	},
 	"{foo='boo'}": {
@@ -104,6 +116,8 @@ test_metric1{foo="bar",instance="i"} 10000 6000000
 test_metric1{foo="boo",instance="i"} 1 6000000
 # TYPE test_metric2 untyped
 test_metric2{foo="boo",instance="i"} 1 6000000
+# TYPE test_metric_old untyped
+test_metric_old{instance=""} 981 5880000
 # TYPE test_metric_without_labels untyped
 test_metric_without_labels{instance=""} 1001 6000000
 `,
@@ -111,7 +125,9 @@ test_metric_without_labels{instance=""} 1001 6000000
 	"empty label value matches everything that doesn't have that label": {
 		params: "match[]={foo='',__name__=~'.%2b'}",
 		code:   200,
-		body: `# TYPE test_metric_without_labels untyped
+		body: `# TYPE test_metric_old untyped
+test_metric_old{instance=""} 981 5880000
+# TYPE test_metric_without_labels untyped
 test_metric_without_labels{instance=""} 1001 6000000
 `,
 	},
@@ -123,6 +139,8 @@ test_metric1{foo="bar",instance="i"} 10000 6000000
 test_metric1{foo="boo",instance="i"} 1 6000000
 # TYPE test_metric2 untyped
 test_metric2{foo="boo",instance="i"} 1 6000000
+# TYPE test_metric_old untyped
+test_metric_old{instance=""} 981 5880000
 # TYPE test_metric_without_labels untyped
 test_metric_without_labels{instance=""} 1001 6000000
 `,
@@ -136,6 +154,8 @@ test_metric1{foo="bar",instance="i",zone="ie"} 10000 6000000
 test_metric1{foo="boo",instance="i",zone="ie"} 1 6000000
 # TYPE test_metric2 untyped
 test_metric2{foo="boo",instance="i",zone="ie"} 1 6000000
+# TYPE test_metric_old untyped
+test_metric_old{foo="baz",instance="",zone="ie"} 981 5880000
 # TYPE test_metric_without_labels untyped
 test_metric_without_labels{foo="baz",instance="",zone="ie"} 1001 6000000
 `,
@@ -151,6 +171,8 @@ test_metric1{foo="bar",instance="i"} 10000 6000000
 test_metric1{foo="boo",instance="i"} 1 6000000
 # TYPE test_metric2 untyped
 test_metric2{foo="boo",instance="i"} 1 6000000
+# TYPE test_metric_old untyped
+test_metric_old{instance="baz"} 981 5880000
 # TYPE test_metric_without_labels untyped
 test_metric_without_labels{instance="baz"} 1001 6000000
 `,
@@ -164,6 +186,8 @@ func TestFederation(t *testing.T) {
 			test_metric1{foo="boo",instance="i"}    1+0x100
 			test_metric2{foo="boo",instance="i"}    1+0x100
 			test_metric_without_labels 1+10x100
+			test_metric_stale                       1+10x99 stale
+			test_metric_old                         1+10x98
 	`)
 	if err != nil {
 		t.Fatal(err)