feat: Export Prometheus compatible metrics (#123)

* feat: Export Prometheus compatible metrics

Signed-off-by: jannfis <jann@mistrust.net>

* adapt spelling action configuration

Signed-off-by: jannfis <jann@mistrust.net>

* adapt spelling action configuration

Signed-off-by: jannfis <jann@mistrust.net>

1 files changed, 187 insertions, 0 deletions

diff --git a/pkg/metrics/metrics.go b/pkg/metrics/metrics.go
new file mode 100644
index 0000000..08c8f4b
--- /dev/null
+++ b/pkg/metrics/metrics.go
@@ -0,0 +1,187 @@
+package metrics
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+// TODO: These should not be global vars with this package
+var epm *EndpointMetrics
+var apm *ApplicationMetrics
+var cpm *ClientMetrics
+
+// EndpointMetrics stores metrics for registry endpoints
+type EndpointMetrics struct {
+	requestsTotal  *prometheus.CounterVec
+	requestsFailed *prometheus.CounterVec
+}
+
+// ApplicationMetrics stores metrics for applications
+type ApplicationMetrics struct {
+	applicationsTotal        prometheus.Gauge
+	imagesWatchedTotal       *prometheus.GaugeVec
+	imagesUpdatedTotal       *prometheus.CounterVec
+	imagesUpdatedErrorsTotal *prometheus.CounterVec
+}
+
+// ClientMetrics stores metrics for K8s and ArgoCD clients
+type ClientMetrics struct {
+	argoCDRequestsTotal        *prometheus.CounterVec
+	argoCDRequestsErrorsTotal  *prometheus.CounterVec
+	kubeAPIRequestsTotal       prometheus.Counter
+	kubeAPIRequestsErrorsTotal prometheus.Counter
+}
+
+// StartMetricsServer starts a new HTTP server for metrics on given port
+func StartMetricsServer(port int) chan error {
+	errCh := make(chan error)
+	go func() {
+		http.Handle("/metrics", promhttp.Handler())
+		errCh <- http.ListenAndServe(fmt.Sprintf(":%d", port), nil)
+	}()
+	return errCh
+}
+
+// NewEndpointMetrics returns a new endpoint metrics object
+func NewEndpointMetrics() *EndpointMetrics {
+	metrics := &EndpointMetrics{}
+
+	metrics.requestsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
+		Name: "argocd_image_updater_registry_requests_total",
+		Help: "The total number of requests to this endpoint",
+	}, []string{"registry"})
+	metrics.requestsFailed = promauto.NewCounterVec(prometheus.CounterOpts{
+		Name: "argocd_image_updater_registry_requests_failed_total",
+		Help: "The number of failed requests to this endpoint",
+	}, []string{"registry"})
+
+	return metrics
+}
+
+// NewApplicationsMetrics returns a new application metrics object
+func NewApplicationsMetrics() *ApplicationMetrics {
+	metrics := &ApplicationMetrics{}
+
+	metrics.applicationsTotal = promauto.NewGauge(prometheus.GaugeOpts{
+		Name: "argocd_image_updater_applications_watched_total",
+		Help: "The total number of applications watched by Argo CD Image Updater",
+	})
+
+	metrics.imagesWatchedTotal = promauto.NewGaugeVec(prometheus.GaugeOpts{
+		Name: "argocd_image_updater_images_watched_total",
+		Help: "Number of images watched by Argo CD Image Updater",
+	}, []string{"application"})
+
+	metrics.imagesUpdatedTotal = promauto.NewCounterVec(prometheus.CounterOpts{
+		Name: "argocd_image_updater_images_updated_total",
+		Help: "Number of images updates by Argo CD Image Updater",
+	}, []string{"application"})
+
+	metrics.imagesUpdatedErrorsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
+		Name: "argocd_image_updater_images_errors_total",
+		Help: "Number of errors reported by Argo CD Image Updater",
+	}, []string{"application"})
+
+	return metrics
+}
+
+// NewClientMetrics returns a new client metrics object
+func NewClientMetrics() *ClientMetrics {
+	metrics := &ClientMetrics{}
+
+	metrics.argoCDRequestsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
+		Name: "argocd_image_updater_argocd_api_requests_total",
+		Help: "The total number of Argo CD API requests performed by the Argo CD Image Updater",
+	}, []string{"argocd_server"})
+
+	metrics.argoCDRequestsErrorsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
+		Name: "argocd_image_updater_argocd_api_errors_total",
+		Help: "The total number of Argo CD API requests resulting in error",
+	}, []string{"argocd_server"})
+
+	metrics.kubeAPIRequestsTotal = promauto.NewCounter(prometheus.CounterOpts{
+		Name: "argocd_image_updater_k8s_api_requests_total",
+		Help: "The total number of Argo CD API requests resulting in error",
+	})
+
+	metrics.kubeAPIRequestsErrorsTotal = promauto.NewCounter(prometheus.CounterOpts{
+		Name: "argocd_image_updater_k8s_api_errors_total",
+		Help: "The total number of Argo CD API requests resulting in error",
+	})
+
+	return metrics
+}
+
+// Endpoint returns the global EndpointMetrics object
+func Endpoint() *EndpointMetrics {
+	return epm
+}
+
+// Applications returns the global ApplicationMetrics object
+func Applications() *ApplicationMetrics {
+	return apm
+}
+
+// Clients returns the global ClientMetrics object
+func Clients() *ClientMetrics {
+	return cpm
+}
+
+// IncreaseRequest increases the request counter of EndpointMetrics object
+func (epm *EndpointMetrics) IncreaseRequest(registryURL string, isFailed bool) {
+	epm.requestsTotal.WithLabelValues(registryURL).Inc()
+	if isFailed {
+		epm.requestsFailed.WithLabelValues(registryURL).Inc()
+	}
+}
+
+// SetNumberOfApplications sets the total number of currently watched applications
+func (apm *ApplicationMetrics) SetNumberOfApplications(num int) {
+	apm.applicationsTotal.Set(float64(num))
+}
+
+// SetNumberOfImagesWatched sets the total number of currently watched images for given application
+func (apm *ApplicationMetrics) SetNumberOfImagesWatched(application string, num int) {
+	apm.imagesWatchedTotal.WithLabelValues(application).Set(float64(num))
+}
+
+// IncreaseImageUpdate increases the number of image updates for given application
+func (apm *ApplicationMetrics) IncreaseImageUpdate(application string, by int) {
+	apm.imagesUpdatedTotal.WithLabelValues(application).Add(float64(by))
+}
+
+// IncreaseUpdateErrors increases the number of errors for given application occured during update process
+func (apm *ApplicationMetrics) IncreaseUpdateErrors(application string, by int) {
+	apm.imagesUpdatedErrorsTotal.WithLabelValues(application).Add(float64(by))
+}
+
+// IncreaseArgoCDClientRequest increases the number of Argo CD API requests for given server
+func (cpm *ClientMetrics) IncreaseArgoCDClientRequest(server string, by int) {
+	cpm.argoCDRequestsTotal.WithLabelValues(server).Add(float64(by))
+}
+
+// IncreaseArgoCDClientError increases the number of failed Argo CD API requests for given server
+func (cpm *ClientMetrics) IncreaseArgoCDClientError(server string, by int) {
+	cpm.argoCDRequestsErrorsTotal.WithLabelValues(server).Add(float64(by))
+}
+
+// IncreaseK8sClientRequest increases the number of K8s API requests
+func (cpm *ClientMetrics) IncreaseK8sClientRequest(by int) {
+	cpm.kubeAPIRequestsTotal.Add(float64(by))
+}
+
+// IncreaseK8sClientRequest increases the number of failed K8s API requests
+func (cpm *ClientMetrics) IncreaseK8sClientError(by int) {
+	cpm.kubeAPIRequestsErrorsTotal.Add(float64(by))
+}
+
+// TODO: This is a lazy workaround, better initialize it somehwere else
+func init() {
+	epm = NewEndpointMetrics()
+	apm = NewApplicationsMetrics()
+	cpm = NewClientMetrics()
+}