lib/promscrape: support filtering targets via scrapePool GET param in /api/v1/targets API (#8611)

This improves compatibility with Prometheus `/api/v1/targets` API.

https://github.com/VictoriaMetrics/VictoriaMetrics/issues/5343

---------

Signed-off-by: hagen1778 <roman@victoriametrics.com>
Co-authored-by: Zakhar Bessarab <z.bessarab@victoriametrics.com>

(cherry picked from commit a2ba37be68)
Signed-off-by: hagen1778 <roman@victoriametrics.com>

app/vmagent/main.go

@@ -443,8 +443,10 @@ func requestHandler(w http.ResponseWriter, r *http.Request) bool {
 	case "/prometheus/api/v1/targets", "/api/v1/targets":
 		promscrapeAPIV1TargetsRequests.Inc()
 		w.Header().Set("Content-Type", "application/json")
+		// https://prometheus.io/docs/prometheus/latest/querying/api/#targets
 		state := r.FormValue("state")
-		promscrape.WriteAPIV1Targets(w, state)
+		scrapePool := r.FormValue("scrapePool")
+		promscrape.WriteAPIV1Targets(w, state, scrapePool)
 		return true
 	case "/prometheus/target_response", "/target_response":
 		promscrapeTargetResponseRequests.Inc()

docs/victoriametrics/changelog/CHANGELOG.md

@@ -19,6 +19,7 @@ See also [LTS releases](https://docs.victoriametrics.com/lts-releases/).
 ## tip
 
 * FEATURE: [dashboards/single](https://grafana.com/grafana/dashboards/10229), [dashboards/cluster](https://grafana.com/grafana/dashboards/11176): remove panel `Storage full ETA` as it could have showing incorrect predictions and result in user's confusion. See more details in [this PR](https://github.com/VictoriaMetrics/VictoriaMetrics/pull/8492).
+* FEATURE: [vmsingle](https://docs.victoriametrics.com/single-server-victoriametrics/), [vmagent](https://docs.victoriametrics.com/vmagent/): support filtering targets via `scrapePool` GET param in `/api/v1/targets` API.
 
 * BUGFIX: [vmgateway](https://docs.victoriametrics.com/vmgateway): properly set the `Host` header when routing requests to `-write.url` and `-read.url`, which is needed for reverse proxies like Traefik.
 * BUGFIX: [vmalert](https://docs.victoriametrics.com/vmalert/) for [VictoriaMetrics enterprise](https://docs.victoriametrics.com/enterprise.html): properly attach tenant labels `vm_account_id` and `vm_project_id` to alerting rules when enabling `-clusterMode`. Previously, these labels were lost in alert messages to Alertmanager. Bug was introduced in [v1.112.0](https://github.com/VictoriaMetrics/VictoriaMetrics/releases/tag/v1.112.0).

lib/promscrape/targetstatus.go

@@ -68,13 +68,13 @@ func WriteServiceDiscovery(w http.ResponseWriter, r *http.Request) {
 }
 
 // WriteAPIV1Targets writes /api/v1/targets to w according to https://prometheus.io/docs/prometheus/latest/querying/api/#targets
-func WriteAPIV1Targets(w io.Writer, state string) {
+func WriteAPIV1Targets(w io.Writer, state, scrapePool string) {
 	if state == "" {
 		state = "any"
 	}
 	fmt.Fprintf(w, `{"status":"success","data":{"activeTargets":`)
 	if state == "active" || state == "any" {
-		tsmGlobal.WriteActiveTargetsJSON(w)
+		tsmGlobal.WriteActiveTargetsJSON(w, scrapePool)
 	} else {
 		fmt.Fprintf(w, `[]`)
 	}
@@ -254,16 +254,24 @@ func (tsm *targetStatusMap) getActiveTargetStatuses() []targetStatus {
 }
 
 // WriteActiveTargetsJSON writes `activeTargets` contents to w according to https://prometheus.io/docs/prometheus/latest/querying/api/#targets
-func (tsm *targetStatusMap) WriteActiveTargetsJSON(w io.Writer) {
+func (tsm *targetStatusMap) WriteActiveTargetsJSON(w io.Writer, scrapePoolFilter string) {
 	tss := tsm.getActiveTargetStatuses()
 	fmt.Fprintf(w, `[`)
-	for i, ts := range tss {
+	var needComma bool
+	for _, ts := range tss {
+		scrapePool := ts.sw.Config.jobNameOriginal
+		if scrapePoolFilter != "" && scrapePool != scrapePoolFilter {
+			continue
+		}
+		if needComma {
+			fmt.Fprintf(w, `,`)
+		}
 		fmt.Fprintf(w, `{"discoveredLabels":`)
 		writeLabelsJSON(w, ts.sw.Config.OriginalLabels)
 		fmt.Fprintf(w, `,"labels":`)
 		writeLabelsJSON(w, ts.sw.Config.Labels)
 		// see https://github.com/VictoriaMetrics/VictoriaMetrics/issues/5343
-		fmt.Fprintf(w, `,"scrapePool":%s`, stringsutil.JSONString(ts.sw.Config.jobNameOriginal))
+		fmt.Fprintf(w, `,"scrapePool":%s`, stringsutil.JSONString(scrapePool))
 		fmt.Fprintf(w, `,"scrapeUrl":%s`, stringsutil.JSONString(ts.sw.Config.ScrapeURL))
 		errMsg := ""
 		if ts.err != nil {
@@ -278,9 +286,7 @@ func (tsm *targetStatusMap) WriteActiveTargetsJSON(w io.Writer) {
 			state = "down"
 		}
 		fmt.Fprintf(w, `,"health":%s}`, stringsutil.JSONString(state))
-		if i+1 < len(tss) {
-			fmt.Fprintf(w, `,`)
-		}
+		needComma = true
 	}
 	fmt.Fprintf(w, `]`)
 }

lib/promscrape/targetstatus_test.go

@@ -0,0 +1,60 @@
+package promscrape
+
+import (
+	"bytes"
+	"encoding/json"
+	"reflect"
+	"testing"
+
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/promutil"
+)
+
+func TestWriteActiveTargetsJSON(t *testing.T) {
+	tsm := newTargetStatusMap()
+	tsm.Register(&scrapeWork{
+		Config: &ScrapeWork{
+			jobNameOriginal: "foo",
+			OriginalLabels: promutil.NewLabelsFromMap(map[string]string{
+				"__address__": "host1:80",
+			}),
+		},
+	})
+	tsm.Register(&scrapeWork{
+		Config: &ScrapeWork{
+			jobNameOriginal: "bar",
+			OriginalLabels: promutil.NewLabelsFromMap(map[string]string{
+				"__address__": "host2:80",
+			}),
+		},
+	})
+
+	type activeTarget struct {
+		DiscoveredLabels map[string]string `json:"discoveredLabels"`
+		ScrapePool       string            `json:"scrapePool"`
+	}
+	f := func(scrapePoolFilter string, exp []activeTarget) {
+		t.Helper()
+		b := &bytes.Buffer{}
+		tsm.WriteActiveTargetsJSON(b, scrapePoolFilter)
+
+		var got []activeTarget
+		if err := json.Unmarshal(b.Bytes(), &got); err != nil {
+			t.Fatal(err)
+		}
+		if !reflect.DeepEqual(got, exp) {
+			t.Fatalf("unexpected response; \ngot\n %s; \nwant\n %s", got, exp)
+		}
+	}
+
+	f("", []activeTarget{
+		{ScrapePool: "foo", DiscoveredLabels: map[string]string{"__address__": "host1:80"}},
+		{ScrapePool: "bar", DiscoveredLabels: map[string]string{"__address__": "host2:80"}},
+	})
+	f("foo", []activeTarget{
+		{ScrapePool: "foo", DiscoveredLabels: map[string]string{"__address__": "host1:80"}},
+	})
+	f("bar", []activeTarget{
+		{ScrapePool: "bar", DiscoveredLabels: map[string]string{"__address__": "host2:80"}},
+	})
+	f("unknown", []activeTarget{})
+}