api: tests for /target/metadata API endpoint

This commit introduces several test cases for the current /targets/metadata API endpoint.

To achieve so, we use a mock of the metadataStore and inject it to the targets under test.

Currently, three success cases are covered: with a metric name, with a target matcher, and with both. As for the failure scenario, the one where we couldn't match against a particular metric is covered.

Signed-off-by: gotjosh <josue@grafana.com>

web/api/v1/api_test.go

@@ -43,6 +43,7 @@ import (
 	"github.com/prometheus/prometheus/config"
 	"github.com/prometheus/prometheus/pkg/gate"
 	"github.com/prometheus/prometheus/pkg/labels"
+	"github.com/prometheus/prometheus/pkg/textparse"
 	"github.com/prometheus/prometheus/pkg/timestamp"
 	"github.com/prometheus/prometheus/prompb"
 	"github.com/prometheus/prometheus/promql"
@@ -55,6 +56,28 @@ import (
 	"github.com/prometheus/prometheus/util/testutil"
 )
 
+// testMetaStore satisfies the scrape.MetricMetadataStore interface.
+// It is used to inject specific metadata as part of a test case.
+type testMetaStore struct {
+	Metadata []scrape.MetricMetadata
+}
+
+func (s *testMetaStore) ListMetadata() []scrape.MetricMetadata {
+	return s.Metadata
+}
+
+func (s *testMetaStore) GetMetadata(metric string) (scrape.MetricMetadata, bool) {
+	for _, m := range s.Metadata {
+		if metric == m.Metric {
+			return m, true
+		}
+	}
+
+	return scrape.MetricMetadata{}, false
+}
+
+// testTargetRetriever represents a list of targets to scrape.
+// It is used to represent targets as part of test cases.
 type testTargetRetriever struct {
 	activeTargets  map[string][]*scrape.Target
 	droppedTargets map[string][]*scrape.Target
@@ -113,6 +136,20 @@ func (t testTargetRetriever) TargetsDropped() map[string][]*scrape.Target {
 	return t.droppedTargets
 }
 
+func (t testTargetRetriever) setMetadataStoreForTargets(identifier string, metadata scrape.MetricMetadataStore) error {
+	targets, ok := t.activeTargets[identifier]
+
+	if !ok {
+		return errors.New("targets not found")
+	}
+
+	for _, at := range targets {
+		at.SetMetadataStore(metadata)
+	}
+
+	return nil
+}
+
 type testAlertmanagerRetriever struct{}
 
 func (t testAlertmanagerRetriever) Alertmanagers() []*url.URL {
@@ -250,48 +287,7 @@ func TestEndpoints(t *testing.T) {
 
 		algr.RuleGroups()
 
-		targets := []*testTargetParams{
-			{
-				Identifier: "test",
-				Labels: labels.FromMap(map[string]string{
-					model.SchemeLabel:      "http",
-					model.AddressLabel:     "example.com:8080",
-					model.MetricsPathLabel: "/metrics",
-					model.JobLabel:         "test",
-				}),
-				DiscoveredLabels: nil,
-				Params:           url.Values{},
-				Reports:          []*testReport{{scrapeStart, 70 * time.Millisecond, nil}},
-				Active:           true,
-			},
-			{
-				Identifier: "blackbox",
-				Labels: labels.FromMap(map[string]string{
-					model.SchemeLabel:      "http",
-					model.AddressLabel:     "localhost:9115",
-					model.MetricsPathLabel: "/probe",
-					model.JobLabel:         "blackbox",
-				}),
-				DiscoveredLabels: nil,
-				Params:           url.Values{"target": []string{"example.com"}},
-				Reports:          []*testReport{{scrapeStart, 100 * time.Millisecond, errors.New("failed")}},
-				Active:           true,
-			},
-			{
-				Identifier: "blackbox",
-				Labels:     nil,
-				DiscoveredLabels: labels.FromMap(map[string]string{
-					model.SchemeLabel:      "http",
-					model.AddressLabel:     "http://dropped.example.com:9115",
-					model.MetricsPathLabel: "/probe",
-					model.JobLabel:         "blackbox",
-				}),
-				Params: url.Values{},
-				Active: false,
-			},
-		}
-
-		testTargetRetriever := newTestTargetRetriever(targets)
+		testTargetRetriever := setupTestTargetRetriever(t)
 
 		api := &API{
 			Queryable:             suite.Storage(),
@@ -355,48 +351,7 @@ func TestEndpoints(t *testing.T) {
 
 		algr.RuleGroups()
 
-		targets := []*testTargetParams{
-			{
-				Identifier: "test",
-				Labels: labels.FromMap(map[string]string{
-					model.SchemeLabel:      "http",
-					model.AddressLabel:     "example.com:8080",
-					model.MetricsPathLabel: "/metrics",
-					model.JobLabel:         "test",
-				}),
-				DiscoveredLabels: nil,
-				Params:           url.Values{},
-				Reports:          []*testReport{{scrapeStart, 70 * time.Millisecond, nil}},
-				Active:           true,
-			},
-			{
-				Identifier: "blackbox",
-				Labels: labels.FromMap(map[string]string{
-					model.SchemeLabel:      "http",
-					model.AddressLabel:     "localhost:9115",
-					model.MetricsPathLabel: "/probe",
-					model.JobLabel:         "blackbox",
-				}),
-				DiscoveredLabels: nil,
-				Params:           url.Values{"target": []string{"example.com"}},
-				Reports:          []*testReport{{scrapeStart, 100 * time.Millisecond, errors.New("failed")}},
-				Active:           true,
-			},
-			{
-				Identifier: "blackbox",
-				Labels:     nil,
-				DiscoveredLabels: labels.FromMap(map[string]string{
-					model.SchemeLabel:      "http",
-					model.AddressLabel:     "http://dropped.example.com:9115",
-					model.MetricsPathLabel: "/probe",
-					model.JobLabel:         "blackbox",
-				}),
-				Params: url.Values{},
-				Active: false,
-			},
-		}
-
-		testTargetRetriever := newTestTargetRetriever(targets)
+		testTargetRetriever := setupTestTargetRetriever(t)
 
 		api := &API{
 			Queryable:             remote,
@@ -450,6 +405,76 @@ func TestLabelNames(t *testing.T) {
 	}
 }
 
+func setupTestTargetRetriever(t *testing.T) *testTargetRetriever {
+	t.Helper()
+
+	targets := []*testTargetParams{
+		{
+			Identifier: "test",
+			Labels: labels.FromMap(map[string]string{
+				model.SchemeLabel:      "http",
+				model.AddressLabel:     "example.com:8080",
+				model.MetricsPathLabel: "/metrics",
+				model.JobLabel:         "test",
+			}),
+			DiscoveredLabels: nil,
+			Params:           url.Values{},
+			Reports:          []*testReport{{scrapeStart, 70 * time.Millisecond, nil}},
+			Active:           true,
+		},
+		{
+			Identifier: "blackbox",
+			Labels: labels.FromMap(map[string]string{
+				model.SchemeLabel:      "http",
+				model.AddressLabel:     "localhost:9115",
+				model.MetricsPathLabel: "/probe",
+				model.JobLabel:         "blackbox",
+			}),
+			DiscoveredLabels: nil,
+			Params:           url.Values{"target": []string{"example.com"}},
+			Reports:          []*testReport{{scrapeStart, 100 * time.Millisecond, errors.New("failed")}},
+			Active:           true,
+		},
+		{
+			Identifier: "blackbox",
+			Labels:     nil,
+			DiscoveredLabels: labels.FromMap(map[string]string{
+				model.SchemeLabel:      "http",
+				model.AddressLabel:     "http://dropped.example.com:9115",
+				model.MetricsPathLabel: "/probe",
+				model.JobLabel:         "blackbox",
+			}),
+			Params: url.Values{},
+			Active: false,
+		},
+	}
+	targetRetriever := newTestTargetRetriever(targets)
+
+	targetRetriever.setMetadataStoreForTargets("test", &testMetaStore{
+		Metadata: []scrape.MetricMetadata{
+			{
+				Metric: "go_threads",
+				Type:   textparse.MetricTypeGauge,
+				Help:   "Number of OS threads created.",
+				Unit:   "",
+			},
+		},
+	})
+
+	targetRetriever.setMetadataStoreForTargets("blackbox", &testMetaStore{
+		Metadata: []scrape.MetricMetadata{
+			{
+				Metric: "prometheus_tsdb_storage_blocks_bytes",
+				Type:   textparse.MetricTypeGauge,
+				Help:   "The number of bytes that are currently used for local storage by all blocks.",
+				Unit:   "",
+			},
+		},
+	})
+
+	return targetRetriever
+}
+
 func setupRemote(s storage.Storage) *httptest.Server {
 	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		req, err := remote.DecodeReadRequest(r)
@@ -926,6 +951,73 @@ func testEndpoints(t *testing.T, api *API, testLabelAPI bool) {
 				},
 			},
 		},
+		// With a matching metric.
+		{
+			endpoint: api.targetMetadata,
+			query: url.Values{
+				"metric": []string{"go_threads"},
+			},
+			response: []metricMetadata{
+				{
+					Target: labels.FromMap(map[string]string{
+						"job": "test",
+					}),
+					Help: "Number of OS threads created.",
+					Type: textparse.MetricTypeGauge,
+					Unit: "",
+				},
+			},
+		},
+		// With a matching target.
+		{
+			endpoint: api.targetMetadata,
+			query: url.Values{
+				"match_target": []string{"{job=\"blackbox\"}"},
+			},
+			response: []metricMetadata{
+				{
+					Target: labels.FromMap(map[string]string{
+						"job": "blackbox",
+					}),
+					Metric: "prometheus_tsdb_storage_blocks_bytes",
+					Help:   "The number of bytes that are currently used for local storage by all blocks.",
+					Type:   textparse.MetricTypeGauge,
+					Unit:   "",
+				},
+			},
+		},
+		// Without a target or metric.
+		{
+			endpoint: api.targetMetadata,
+			response: []metricMetadata{
+				{
+					Target: labels.FromMap(map[string]string{
+						"job": "test",
+					}),
+					Metric: "go_threads",
+					Help:   "Number of OS threads created.",
+					Type:   textparse.MetricTypeGauge,
+					Unit:   "",
+				},
+				{
+					Target: labels.FromMap(map[string]string{
+						"job": "blackbox",
+					}),
+					Metric: "prometheus_tsdb_storage_blocks_bytes",
+					Help:   "The number of bytes that are currently used for local storage by all blocks.",
+					Type:   textparse.MetricTypeGauge,
+					Unit:   "",
+				},
+			},
+		},
+		// Without a matching metric.
+		{
+			endpoint: api.targetMetadata,
+			query: url.Values{
+				"match_target": []string{"{job=\"non-existentblackbox\"}"},
+			},
+			errType: errorNotFound,
+		},
 		{
 			endpoint: api.alertmanagers,
 			response: &AlertmanagerDiscovery{