From 57168d307ac51edd8b499b5a3b5cd8b77cc74586 Mon Sep 17 00:00:00 2001
From: Sebastian Widmer <widmer.sebastian@gmail.com>
Date: Thu, 23 Feb 2023 09:12:49 +0100
Subject: [PATCH] Expose link between organization and billing-entity as a
 Prometheus metric (#104)

---
 controller.go                                 |  6 +++
 controllers/org_billing_ref_link_metric.go    | 53 +++++++++++++++++++
 .../org_billing_ref_link_metric_test.go       | 41 ++++++++++++++
 3 files changed, 100 insertions(+)
 create mode 100644 controllers/org_billing_ref_link_metric.go
 create mode 100644 controllers/org_billing_ref_link_metric_test.go

diff --git a/controller.go b/controller.go
index c286a4cc..2e6712bf 100644
--- a/controller.go
+++ b/controller.go
@@ -15,6 +15,7 @@ import (
 	ctrl "sigs.k8s.io/controller-runtime"
 	"sigs.k8s.io/controller-runtime/pkg/healthz"
 	"sigs.k8s.io/controller-runtime/pkg/log/zap"
+	"sigs.k8s.io/controller-runtime/pkg/metrics"
 	"sigs.k8s.io/controller-runtime/pkg/webhook"
 
 	"github.com/spf13/cobra"
@@ -107,6 +108,11 @@ func setupManager(usernamePrefix, rolePrefix string, memberRoles []string, beRef
 		return nil, err
 	}
 
+	metrics.Registry.MustRegister(
+		&controllers.OrgBillingRefLinkMetric{
+			Client: mgr.GetClient(),
+		})
+
 	ur := &controllers.UserReconciler{
 		Client:   mgr.GetClient(),
 		Scheme:   mgr.GetScheme(),
diff --git a/controllers/org_billing_ref_link_metric.go b/controllers/org_billing_ref_link_metric.go
new file mode 100644
index 00000000..bdbc4eb4
--- /dev/null
+++ b/controllers/org_billing_ref_link_metric.go
@@ -0,0 +1,53 @@
+package controllers
+
+import (
+	"context"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"sigs.k8s.io/controller-runtime/pkg/client"
+
+	orgv1 "github.com/appuio/control-api/apis/organization/v1"
+)
+
+//+kubebuilder:rbac:groups="rbac.appuio.io",resources=organizations,verbs=get;list;watch
+//+kubebuilder:rbac:groups="organization.appuio.io",resources=organizations,verbs=get;list;watch
+
+var desc = prometheus.NewDesc(
+	"control_api_organization_billing_entity_ref",
+	"Link between an organization and a billing entity",
+	[]string{"organization", "billing_entity"},
+	nil,
+)
+
+// OrgBillingRefLinkMetric is a Prometheus collector that exposes the link between an organization and a billing entity.
+type OrgBillingRefLinkMetric struct {
+	client.Client
+}
+
+var _ prometheus.Collector = &OrgBillingRefLinkMetric{}
+
+// Describe implements prometheus.Collector.
+// Sends the static description of the metric to the provided channel.
+func (o *OrgBillingRefLinkMetric) Describe(ch chan<- *prometheus.Desc) {
+	ch <- desc
+}
+
+// Collect implements prometheus.Collector.
+// Sends a metric for each organization and its billing entity to the provided channel.
+func (o *OrgBillingRefLinkMetric) Collect(ch chan<- prometheus.Metric) {
+	orgs := &orgv1.OrganizationList{}
+	if err := o.List(context.Background(), orgs); err != nil {
+		ch <- prometheus.NewInvalidMetric(desc, err)
+		return
+	}
+
+	for _, org := range orgs.Items {
+		ch <- prometheus.MustNewConstMetric(
+			desc,
+			prometheus.GaugeValue,
+			1,
+			org.Name,
+			org.Spec.BillingEntityRef,
+		)
+	}
+}
diff --git a/controllers/org_billing_ref_link_metric_test.go b/controllers/org_billing_ref_link_metric_test.go
new file mode 100644
index 00000000..8be10b3c
--- /dev/null
+++ b/controllers/org_billing_ref_link_metric_test.go
@@ -0,0 +1,41 @@
+package controllers_test
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/prometheus/client_golang/prometheus/testutil"
+	"github.com/stretchr/testify/require"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+
+	orgv1 "github.com/appuio/control-api/apis/organization/v1"
+	"github.com/appuio/control-api/controllers"
+)
+
+func TestOrgBillingRefLinkMetric(t *testing.T) {
+	c := prepareTest(t, &orgv1.Organization{
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "test-org",
+		},
+		Spec: orgv1.OrganizationSpec{
+			BillingEntityRef: "test-billing-entity",
+		},
+	}, &orgv1.Organization{
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "blub-org",
+		},
+		Spec: orgv1.OrganizationSpec{
+			BillingEntityRef: "be-1734",
+		},
+	})
+
+	require.NoError(t,
+		testutil.CollectAndCompare(&controllers.OrgBillingRefLinkMetric{c}, strings.NewReader(`
+# HELP control_api_organization_billing_entity_ref Link between an organization and a billing entity
+# TYPE control_api_organization_billing_entity_ref gauge
+control_api_organization_billing_entity_ref{billing_entity="be-1734",organization="blub-org"} 1
+control_api_organization_billing_entity_ref{billing_entity="test-billing-entity",organization="test-org"} 1
+`),
+			"control_api_organization_billing_entity_ref"),
+	)
+}