feat: expose telemetry compatibility mode metric

Makefile

@@ -34,7 +34,7 @@ TOOLS_PKG_NAMES_CLEAN  := $(shell grep -E $(TOOLS_MOD_REGEX) < $(TOOLS_MOD_DIR)/
 TOOLS_BIN_NAMES  := $(addprefix $(TOOLS_BIN_DIR)/, $(notdir $(TOOLS_PKG_NAMES_CLEAN)))
 
 .PHONY: install-tools
-install-tools: $(TOOLS_BIN_NAMES) $(POPULATE_IMAGES)
+install-tools: $(TOOLS_BIN_NAMES) $(POPULATE_IMAGES) $(PROMLINTER)
 
 $(TOOLS_BIN_DIR):
 	if [ ! -d $@ ]; then mkdir -p $@; fi
@@ -55,6 +55,8 @@ STRINGER         := $(TOOLS_BIN_DIR)/stringer
 WSL		 := $(TOOLS_BIN_DIR)/wsl
 K3D              := $(TOOLS_BIN_DIR)/k3d
 POPULATE_IMAGES  := $(TOOLS_BIN_DIR)/populate-images
+PROMLINTER       := $(TOOLS_BIN_DIR)/promlinter
+GOMPLATE         := $(TOOLS_BIN_DIR)/gomplate
 
 .PHONY: $(POPULATE_IMAGES)
 $(POPULATE_IMAGES):
@@ -222,3 +224,7 @@ deploy-experimental: manifests-experimental $(KUSTOMIZE) ## Deploy resources bas
 .PHONY: undeploy-experimental
 undeploy-experimental: $(KUSTOMIZE) ## Undeploy resources based on the development variant from the K8s cluster specified in ~/.kube/config. Call with ignore-not-found=true to ignore resource not found errors during deletion.
 	$(KUSTOMIZE) build config/development | kubectl delete --ignore-not-found=$(ignore-not-found) -f -
+
+.PHONY: update-metrics-docs
+ update-metrics-docs: $(PROMLINTER) $(GOMPLATE) # Update metrics documentation
+	@metrics=$$(mktemp).json; echo $${metrics}; $(PROMLINTER) list -ojson . > $${metrics}; $(GOMPLATE) -d telemetry=$${metrics} -f hack/telemetry-internal-metrics.md.tpl > docs/contributor/telemetry-internal-metrics.md

docs/contributor/telemetry-internal-metrics.md

@@ -0,0 +1,10 @@
+<!-- The table below was generated automatically -->
+<!-- Please do not edit it directly. If you want to change it, please update the template and regenerate the file with make target  update-metrics-docs -->
+# Metrics Emitted by Kyma Telemetry Manager
+
+| Metric                                                          | Description                                                                                   |
+|-----------------------------------------------------------------|:----------------------------------------------------------------------------------------------|
+| **telemetry_otelcol_metrics_compatibility_mode** | Indicates if the OpenTelemetry internal metrics compatibility mode is enabled (1) or disabled (0) |
+| **telemetry_self_monitor_prober_in_flight_requests** | The current number of in-flight requests initiated by the self-monitoring prober. |
+| **telemetry_self_monitor_prober_requests_total** | Total number of requests initiated by the self-monitoring prober. |
+| **telemetry_self_monitor_prober_duration_seconds** | A histogram of latencies for requests initiated by the self-monitoring prober. |

hack/telemetry-internal-metrics.md.tpl

@@ -0,0 +1,9 @@
+<!-- The table below was generated automatically -->
+<!-- Please do not edit it directly. If you want to change it, please update the template and regenerate the file with make target  update-metrics-docs -->
+# Metrics Emitted by Kyma Telemetry Manager
+
+| Metric                                                          | Description                                                                                   |
+|-----------------------------------------------------------------|:----------------------------------------------------------------------------------------------|
+{{- range (ds "telemetry") }}
+| **{{.Name}}** | {{.Help}} |
+{{- end }}

internal/reconciler/telemetry/reconciler.go

@@ -78,6 +78,7 @@ type Reconciler struct {
 	healthCheckers            healthCheckers
 	overridesHandler          OverridesHandler
 	selfMonitorApplierDeleter SelfMonitorApplierDeleter
+	metricsEmitter            telemetryMetricsEmitter
 }
 
 func New(
@@ -98,6 +99,7 @@ func New(
 		},
 		overridesHandler:          overridesHandler,
 		selfMonitorApplierDeleter: selfMonitorApplierDeleter,
+		metricsEmitter:            NewTelemetryMetricsEmitter(),
 	}
 }
 
@@ -129,6 +131,8 @@ func (r *Reconciler) Reconcile(ctx context.Context, req ctrl.Request) (ctrl.Resu
 		}
 	}
 
+	r.metricsEmitter.updateCompatibilityModeMetric(telemetryutils.GetCompatibilityModeFromTelemetry(ctx, r.Client, telemetry.Namespace))
+
 	requeue := telemetry.Status.State == operatorv1alpha1.StateWarning
 
 	return ctrl.Result{Requeue: requeue}, err

internal/reconciler/telemetry/telemetry_metric_emitter.go

@@ -0,0 +1,25 @@
+package telemetry
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+	"sigs.k8s.io/controller-runtime/pkg/metrics"
+)
+
+var compatibilityModeGauge = prometheus.NewGauge(prometheus.GaugeOpts{
+	Name: "telemetry_otelcol_metrics_compatibility_mode",
+	Help: "Indicates if the OpenTelemetry internal metrics compatibility mode is enabled (1) or disabled (0)",
+})
+
+type telemetryMetricsEmitter struct{}
+
+func NewTelemetryMetricsEmitter() telemetryMetricsEmitter {
+	metrics.Registry.MustRegister(compatibilityModeGauge)
+	return telemetryMetricsEmitter{}
+}
+func (e telemetryMetricsEmitter) updateCompatibilityModeMetric(compatibilityMode bool) {
+	if compatibilityMode {
+		compatibilityModeGauge.Set(1)
+	} else {
+		compatibilityModeGauge.Set(0)
+	}
+}