feat(metrics): provide metrics for tenant quotas

Signed-off-by: Lukas Boettcher <1340215+lukasboettcher@users.noreply.github.com>

Author: lukasboettcher

controllers/tenant/cleanup.go

@@ -0,0 +1,50 @@
+// Copyright 2020-2023 Project Capsule Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package tenant
+
+import (
+	"context"
+
+	"sigs.k8s.io/controller-runtime/pkg/controller/controllerutil"
+
+	capsulev1beta2 "github.com/projectcapsule/capsule/api/v1beta2"
+	"github.com/projectcapsule/capsule/pkg/metrics"
+)
+
+func (r *Manager) handleMetricsCleanup(ctx context.Context, tenant *capsulev1beta2.Tenant) (err error) {
+	metricsFinalizer := "capsule.clastix.io/metrics-cleanup"
+
+	// examine DeletionTimestamp to determine if object is under deletion
+	if tenant.ObjectMeta.DeletionTimestamp.IsZero() { //nolint:nestif
+		// The object is not being deleted, so if it does not have our finalizer,
+		// then lets add the finalizer and update the object. This is equivalent
+		// to registering our finalizer.
+		if !controllerutil.ContainsFinalizer(tenant, metricsFinalizer) {
+			controllerutil.AddFinalizer(tenant, metricsFinalizer)
+
+			if err := r.Update(ctx, tenant); err != nil {
+				return err
+			}
+		}
+	} else {
+		// The object is being deleted
+		if controllerutil.ContainsFinalizer(tenant, metricsFinalizer) {
+			// our finalizer is present, so handle the removal of the metrics
+			r.Log.Info("Removing ResourceQuota metrics because Tenant " + tenant.Name + " is being deleted")
+
+			// remove all metrics of the deleted tenant
+			metrics.TenantResourceUsage.DeletePartialMatch(map[string]string{"tenant": tenant.Name})
+			metrics.TenantResourceLimit.DeletePartialMatch(map[string]string{"tenant": tenant.Name})
+
+			// remove our finalizer from the list and update it.
+			controllerutil.RemoveFinalizer(tenant, metricsFinalizer)
+
+			if err := r.Update(ctx, tenant); err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}

controllers/tenant/manager.go

@@ -133,6 +133,15 @@ func (r Manager) Reconcile(ctx context.Context, request ctrl.Request) (result ct
 		return
 	}
 
+	// Handle cleanup of metrics if the tenant was deleted
+	r.Log.Info("Setting up metrics cleanup")
+
+	if err = r.handleMetricsCleanup(ctx, instance); err != nil {
+		r.Log.Error(err, "Cannot setup metrics cleanup")
+
+		return
+	}
+
 	r.Log.Info("Tenant reconciling completed")
 
 	return ctrl.Result{}, err

controllers/tenant/resourcequotas.go

@@ -23,6 +23,7 @@ import (
 
 	capsulev1beta2 "github.com/projectcapsule/capsule/api/v1beta2"
 	"github.com/projectcapsule/capsule/pkg/api"
+	"github.com/projectcapsule/capsule/pkg/metrics"
 	"github.com/projectcapsule/capsule/pkg/utils"
 )
 
@@ -51,6 +52,18 @@ func (r *Manager) syncResourceQuotas(ctx context.Context, tenant *capsulev1beta2
 	if typeLabel, err = utils.GetTypeLabel(&corev1.ResourceQuota{}); err != nil {
 		return err
 	}
+
+	// Remove prior metrics, to avoid cleaning up for metrics of deleted ResourceQuotas
+	metrics.TenantResourceUsage.DeletePartialMatch(map[string]string{"tenant": tenant.Name})
+	metrics.TenantResourceLimit.DeletePartialMatch(map[string]string{"tenant": tenant.Name})
+
+	// Expose the namespace quota and usage as metrics for the tenant
+	metrics.TenantResourceUsage.WithLabelValues(tenant.Name, "namespaces", "").Set(float64(tenant.Status.Size))
+
+	if tenant.Spec.NamespaceOptions != nil && tenant.Spec.NamespaceOptions.Quota != nil {
+		metrics.TenantResourceLimit.WithLabelValues(tenant.Name, "namespaces", "").Set(float64(*tenant.Spec.NamespaceOptions.Quota))
+	}
+
 	//nolint:nestif
 	if tenant.Spec.ResourceQuota.Scope == api.ResourceQuotaScopeTenant {
 		group := new(errgroup.Group)
@@ -102,6 +115,19 @@ func (r *Manager) syncResourceQuotas(ctx context.Context, tenant *capsulev1beta2
 
 					r.Log.Info("Computed " + name.String() + " quota for the whole Tenant is " + quantity.String())
 
+					// Expose usage and limit metrics for the resource (name) of the ResourceQuota (index)
+					metrics.TenantResourceUsage.WithLabelValues(
+						tenant.Name,
+						name.String(),
+						strconv.Itoa(index),
+					).Set(float64(quantity.MilliValue()) / 1000)
+
+					metrics.TenantResourceLimit.WithLabelValues(
+						tenant.Name,
+						name.String(),
+						strconv.Itoa(index),
+					).Set(float64(hardQuota.MilliValue()) / 1000)
+
 					switch quantity.Cmp(resourceQuota.Hard[name]) {
 					case 0:
 						// The Tenant is matching exactly the Quota:

pkg/metrics/metrics.go

@@ -0,0 +1,30 @@
+// Copyright 2020-2023 Project Capsule Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package metrics
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+	"sigs.k8s.io/controller-runtime/pkg/metrics"
+)
+
+var (
+	metricsPrefix = "capsule_"
+
+	TenantResourceUsage = prometheus.NewGaugeVec(prometheus.GaugeOpts{
+		Name: metricsPrefix + "tenant_resource_usage",
+		Help: "Current resource usage for a given resource in a tenant",
+	}, []string{"tenant", "resource", "resourcequotaindex"})
+
+	TenantResourceLimit = prometheus.NewGaugeVec(prometheus.GaugeOpts{
+		Name: metricsPrefix + "tenant_resource_limit",
+		Help: "Current resource limit for a given resource in a tenant",
+	}, []string{"tenant", "resource", "resourcequotaindex"})
+)
+
+func init() {
+	metrics.Registry.MustRegister(
+		TenantResourceUsage,
+		TenantResourceLimit,
+	)
+}