chore: Introduce FlatMetricFamily struct to flatten prometheus metric output

test/e2e/logs_self_monitor_healthy_test.go

@@ -101,17 +101,18 @@ var _ = Describe(suite.ID(), Label(suite.LabelSelfMonitoringLogsHealthy), Ordere
 				// Pushing metrics to the metric gateway triggers an alert.
 				// It makes the self-monitor call the webhook, which in turn increases the counter.
 				assert.ManagerEmitsMetric(proxyClient,
-					Equal("controller_runtime_webhook_requests_total"),
+					HaveName(Equal("controller_runtime_webhook_requests_total")),
 					SatisfyAll(
-						WithLabels(HaveKeyWithValue("webhook", "/api/v2/alerts")),
-						WithValue(BeNumerically(">", 0)),
+						HaveLabels(HaveKeyWithValue("webhook", "/api/v2/alerts")),
+						HaveMetricValue(BeNumerically(">", 0)),
 					))
 			})
 
 			It("Ensures that telemetry_self_monitor_prober_requests_total is emitted", func() {
-				assert.ManagerEmitsMetric(proxyClient,
-					Equal("telemetry_self_monitor_prober_requests_total"),
-					WithValue(BeNumerically(">", 0)),
+				assert.ManagerEmitsMetric(
+					proxyClient,
+					HaveName(Equal("telemetry_self_monitor_prober_requests_total")),
+					HaveMetricValue(BeNumerically(">", 0)),
 				)
 			})
 		})

test/e2e/metrics_self_monitor_healthy_test.go

@@ -124,17 +124,17 @@ var _ = Describe(suite.ID(), Label(suite.LabelSelfMonitoringMetricsHealthy), Ord
 				// Pushing metrics to the metric gateway triggers an alert.
 				// It makes the self-monitor call the webhook, which in turn increases the counter.
 				assert.ManagerEmitsMetric(proxyClient,
-					Equal("controller_runtime_webhook_requests_total"),
+					HaveName(Equal("controller_runtime_webhook_requests_total")),
 					SatisfyAll(
-						WithLabels(HaveKeyWithValue("webhook", "/api/v2/alerts")),
-						WithValue(BeNumerically(">", 0)),
+						HaveLabels(HaveKeyWithValue("webhook", "/api/v2/alerts")),
+						HaveMetricValue(BeNumerically(">", 0)),
 					))
 			})
 
 			It("Ensures that telemetry_self_monitor_prober_requests_total is emitted", func() {
 				assert.ManagerEmitsMetric(proxyClient,
-					Equal("telemetry_self_monitor_prober_requests_total"),
-					WithValue(BeNumerically(">", 0)),
+					HaveName(Equal("telemetry_self_monitor_prober_requests_total")),
+					HaveMetricValue(BeNumerically(">", 0)),
 				)
 			})
 		})

test/e2e/traces_self_monitor_healthy_test.go

@@ -119,17 +119,17 @@ var _ = Describe(suite.ID(), Label(suite.LabelSelfMonitoringTracesHealthy), Orde
 				// Pushing metrics to the metric gateway triggers an alert.
 				// It makes the self-monitor call the webhook, which in turn increases the counter.
 				assert.ManagerEmitsMetric(proxyClient,
-					Equal("controller_runtime_webhook_requests_total"),
+					HaveName(Equal("controller_runtime_webhook_requests_total")),
 					SatisfyAll(
-						WithLabels(HaveKeyWithValue("webhook", "/api/v2/alerts")),
-						WithValue(BeNumerically(">", 0)),
+						HaveLabels(HaveKeyWithValue("webhook", "/api/v2/alerts")),
+						HaveMetricValue(BeNumerically(">", 0)),
 					))
 			})
 
 			It("Ensures that telemetry_self_monitor_prober_requests_total is emitted", func() {
 				assert.ManagerEmitsMetric(proxyClient,
-					Equal("telemetry_self_monitor_prober_requests_total"),
-					WithValue(BeNumerically(">", 0)),
+					HaveName(Equal("telemetry_self_monitor_prober_requests_total")),
+					HaveMetricValue(BeNumerically(">", 0)),
 				)
 			})
 		})

test/testkit/assert/monitoring.go

@@ -18,7 +18,7 @@ func EmitsOTelCollectorMetrics(proxyClient *apiserverproxy.Client, metricsURL st
 		resp, err := proxyClient.Get(metricsURL)
 		g.Expect(err).NotTo(HaveOccurred())
 		g.Expect(resp).To(HaveHTTPStatus(http.StatusOK))
-		g.Expect(resp).To(HaveHTTPBody(ContainMetricFamily(WithName(ContainSubstring("otelcol")))))
+		g.Expect(resp).To(HaveHTTPBody(HaveFlatMetricFamilies(ContainElement(HaveName(ContainSubstring("otelcol"))))))
 
 		err = resp.Body.Close()
 		g.Expect(err).NotTo(HaveOccurred())
@@ -27,8 +27,7 @@ func EmitsOTelCollectorMetrics(proxyClient *apiserverproxy.Client, metricsURL st
 
 func ManagerEmitsMetric(
 	proxyClient *apiserverproxy.Client,
-	nameMatcher types.GomegaMatcher,
-	metricMatcher types.GomegaMatcher) {
+	matchers ...types.GomegaMatcher) {
 	Eventually(func(g Gomega) {
 		telemetryManagerMetricsURL := proxyClient.ProxyURLForService(
 			kitkyma.TelemetryManagerMetricsServiceName.Namespace,
@@ -39,10 +38,7 @@ func ManagerEmitsMetric(
 		g.Expect(err).NotTo(HaveOccurred())
 		g.Expect(resp).To(HaveHTTPStatus(http.StatusOK))
 
-		g.Expect(resp).To(HaveHTTPBody(ContainMetricFamily(SatisfyAll(
-			WithName(nameMatcher),
-			ContainMetric(metricMatcher),
-		))))
+		g.Expect(resp).To(HaveHTTPBody(HaveFlatMetricFamilies(ContainElement(SatisfyAll(matchers...)))))
 
 		err = resp.Body.Close()
 		g.Expect(err).NotTo(HaveOccurred())

test/testkit/matchers/prometheus/prometheus_matcher.go

@@ -5,70 +5,34 @@ import (
 
 	"github.com/onsi/gomega"
 	"github.com/onsi/gomega/types"
-	prommodel "github.com/prometheus/client_model/go"
 	"github.com/prometheus/common/expfmt"
 )
 
-func WithMetricFamilies(matcher types.GomegaMatcher) types.GomegaMatcher {
-	return gomega.WithTransform(func(responseBody []byte) ([]*prommodel.MetricFamily, error) {
+func HaveFlatMetricFamilies(matcher types.GomegaMatcher) types.GomegaMatcher {
+	return gomega.WithTransform(func(responseBody []byte) ([]FlatMetricFamily, error) {
 		var parser expfmt.TextParser
 		mfs, _ := parser.TextToMetricFamilies(bytes.NewReader(responseBody)) //nolint:errcheck // ignore duplicate metrics parsing error and try extract metric
 
-		var result []*prommodel.MetricFamily
+		fmfs := flattenAllMetricFamily(mfs)
 
-		for _, mf := range mfs {
-			result = append(result, mf)
-		}
-
-		return result, nil
-	}, matcher)
-}
-
-func ContainMetricFamily(matcher types.GomegaMatcher) types.GomegaMatcher {
-	return WithMetricFamilies(gomega.ContainElement(matcher))
-}
-
-func WithName(matcher types.GomegaMatcher) types.GomegaMatcher {
-	return gomega.WithTransform(func(mf *prommodel.MetricFamily) string {
-		return mf.GetName()
+		return fmfs, nil
 	}, matcher)
 }
 
-func WithMetrics(matcher types.GomegaMatcher) types.GomegaMatcher {
-	return gomega.WithTransform(func(mf *prommodel.MetricFamily) []*prommodel.Metric {
-		return mf.GetMetric()
+func HaveName(matcher types.GomegaMatcher) types.GomegaMatcher {
+	return gomega.WithTransform(func(fmf FlatMetricFamily) string {
+		return fmf.Name
 	}, matcher)
 }
 
-func ContainMetric(matcher types.GomegaMatcher) types.GomegaMatcher {
-	return WithMetrics(gomega.ContainElement(matcher))
-}
-
-func WithValue(matcher types.GomegaMatcher) types.GomegaMatcher {
-	return gomega.WithTransform(func(m *prommodel.Metric) (float64, error) {
-		if m.Gauge != nil {
-			return m.Gauge.GetValue(), nil
-		}
-
-		if m.Counter != nil {
-			return m.Counter.GetValue(), nil
-		}
-
-		if m.Untyped != nil {
-			return m.Untyped.GetValue(), nil
-		}
-
-		return 0, nil
+func HaveMetricValue(matcher types.GomegaMatcher) types.GomegaMatcher {
+	return gomega.WithTransform(func(fmf FlatMetricFamily) float64 {
+		return fmf.MetricValues
 	}, matcher)
 }
 
-func WithLabels(matcher types.GomegaMatcher) types.GomegaMatcher {
-	return gomega.WithTransform(func(m *prommodel.Metric) (map[string]string, error) {
-		labels := make(map[string]string)
-		for _, l := range m.Label {
-			labels[l.GetName()] = l.GetValue()
-		}
-
-		return labels, nil
+func HaveLabels(matcher types.GomegaMatcher) types.GomegaMatcher {
+	return gomega.WithTransform(func(fmf FlatMetricFamily) map[string]string {
+		return fmf.Labels
 	}, matcher)
 }

test/testkit/matchers/prometheus/prometheus_matcher_test.go

@@ -5,46 +5,46 @@ import (
 	. "github.com/onsi/gomega"
 )
 
-var _ = Describe("ContainMetric", Label("metrics"), func() {
+var _ = Describe("HaveFlatMetricFamilies", Label("metrics"), func() {
 	Context("with nil input", func() {
-		It("should fail", func() {
-			success, err := ContainMetricFamily(WithName(Equal("foo_metric"))).Match(nil)
+		It("should error", func() {
+			success, err := HaveFlatMetricFamilies(ContainElement(HaveName(Equal("foo_metric")))).Match(nil)
 			Expect(err).Should(HaveOccurred())
 			Expect(success).Should(BeFalse())
 		})
 	})
 
 	Context("with empty input", func() {
 		It("should fail", func() {
-			success, err := ContainMetricFamily(WithName(Equal("foo_metric"))).Match([]byte{})
+			success, err := HaveFlatMetricFamilies(ContainElement(HaveName(Equal("foo_metric")))).Match([]byte{})
 			Expect(err).ShouldNot(HaveOccurred())
 			Expect(success).Should(BeFalse())
 		})
 	})
 
 	Context("with invalid input", func() {
 		It("should fail", func() {
-			success, err := ContainMetricFamily(WithName(Equal("foo_metric"))).Match([]byte{1, 2, 3})
+			success, err := HaveFlatMetricFamilies(ContainElement(HaveName(Equal("foo_metric")))).Match([]byte{1, 2, 3})
 			Expect(err).ShouldNot(HaveOccurred())
 			Expect(success).Should(BeFalse())
 		})
 	})
 
-	Context("with having metrics", func() {
-		It("should succeed", func() {
+	Context("with HaveName", func() {
+		It("should apply matcher", func() {
 			fileBytes := `
 # HELP fluentbit_uptime Number of seconds that Fluent Bit has been running.
 # TYPE fluentbit_uptime counter
 fluentbit_uptime{hostname="telemetry-fluent-bit-dglkf"} 5489
 # HELP fluentbit_input_bytes_total Number of input bytes.
 # TYPE fluentbit_input_bytes_total counter
 fluentbit_input_bytes_total{name="tele-tail"} 5217998`
-			Expect([]byte(fileBytes)).Should(ContainMetricFamily(WithName(Equal("fluentbit_uptime"))))
+			Expect([]byte(fileBytes)).Should(HaveFlatMetricFamilies(ContainElement(HaveName(Equal("fluentbit_uptime")))))
 		})
 	})
 })
 
-var _ = Describe("WithLabels", func() {
+var _ = Describe("with HaveLabels", func() {
 	It("should apply matcher", func() {
 		fileBytes := `
 # HELP fluentbit_uptime Number of seconds that Fluent Bit has been running.
@@ -54,14 +54,14 @@ fluentbit_uptime{hostname="telemetry-fluent-bit-dglkf"} 5489
 # TYPE fluentbit_input_bytes_total counter
 fluentbit_input_bytes_total{name="tele-tail"} 5000
 `
-		Expect([]byte(fileBytes)).Should(ContainMetricFamily(SatisfyAll(
-			WithName(Equal("fluentbit_input_bytes_total")),
-			ContainMetric(WithLabels(HaveKeyWithValue("name", "tele-tail"))),
-		)))
+		Expect([]byte(fileBytes)).Should(HaveFlatMetricFamilies(ContainElement(SatisfyAll(
+			HaveName(Equal("fluentbit_input_bytes_total")),
+			HaveLabels(HaveKeyWithValue("name", "tele-tail")),
+		))))
 	})
 })
 
-var _ = Describe("WithValue", func() {
+var _ = Describe("with HaveValue", func() {
 	It("should apply matcher", func() {
 		fileBytes := `
 # HELP fluentbit_uptime Number of seconds that Fluent Bit has been running.
@@ -71,12 +71,10 @@ fluentbit_uptime{hostname="telemetry-fluent-bit-dglkf"} 5489
 # TYPE fluentbit_input_bytes_total counter
 fluentbit_input_bytes_total{name="tele-tail"} 5000
 `
-		Expect([]byte(fileBytes)).Should(ContainMetricFamily(SatisfyAll(
-			WithName(Equal("fluentbit_input_bytes_total")),
-			ContainMetric(SatisfyAll(
-				WithLabels(HaveKeyWithValue("name", "tele-tail")),
-				WithValue(BeNumerically(">=", 0)),
-			)),
-		)))
+		Expect([]byte(fileBytes)).Should(HaveFlatMetricFamilies(ContainElement(SatisfyAll(
+			HaveName(Equal("fluentbit_input_bytes_total")),
+			HaveLabels(HaveKeyWithValue("name", "tele-tail")),
+			HaveMetricValue(BeNumerically(">=", 0)),
+		))))
 	})
 })

test/testkit/matchers/prometheus/prommetric_utils.go

@@ -0,0 +1,68 @@
+package prometheus
+
+import prommodel "github.com/prometheus/client_model/go"
+
+// FlatMetricFamily holds all necessary information about a prometheus MetricFamily.
+// Gomega doesn't handle deeply nested data structure very well and generates large, unreadable diffs when paired with
+// the deeply nested structure of pmetrics.
+//
+// Introducing a go struct with a flat data structure by extracting necessary information from different levels of
+// metricfamily makes accessing the information easier and improves readability of the output.
+type FlatMetricFamily struct {
+	Name         string
+	MetricValues float64
+	Labels       map[string]string
+}
+
+// flattenAllMetricFamily flattens an array of prometheus MetricFamily to a slice of FlatMetricFamily.
+// It converts the deeply nested MetricFamily to a flat struct, making it more readable in the test output.
+func flattenAllMetricFamily(mfs map[string]*prommodel.MetricFamily) []FlatMetricFamily {
+	var fmf []FlatMetricFamily
+	for _, mf := range mfs {
+		fmf = append(fmf, flattenMetricFamily(mf)...)
+	}
+
+	return fmf
+}
+
+// flattenMetricFamily converts a single MetricFamily into a slice of FlatMetricFamily
+// It loops through all the metrics in a MetricFamily and appends it to the FlatMetricFamily slice.
+func flattenMetricFamily(mf *prommodel.MetricFamily) []FlatMetricFamily {
+	var fmf []FlatMetricFamily
+
+	for _, m := range mf.Metric {
+		v := getValuePerMetric(m)
+		fmf = append(fmf, FlatMetricFamily{
+			Name:         mf.GetName(),
+			MetricValues: v,
+			Labels:       labelsToMap(m.GetLabel()),
+		})
+	}
+
+	return fmf
+}
+
+func labelsToMap(l []*prommodel.LabelPair) map[string]string {
+	labels := make(map[string]string)
+	for _, l := range l {
+		labels[l.GetName()] = l.GetValue()
+	}
+
+	return labels
+}
+
+func getValuePerMetric(m *prommodel.Metric) float64 {
+	if m.Gauge != nil {
+		return m.Gauge.GetValue()
+	}
+
+	if m.Counter != nil {
+		return m.Counter.GetValue()
+	}
+
+	if m.Untyped != nil {
+		return m.Untyped.GetValue()
+	}
+
+	return 0
+}