Add prometheus

stats/prometheus.go

@@ -0,0 +1,123 @@
+package stats
+
+import (
+	"context"
+	"net"
+	"net/http"
+	"time"
+
+	"github.com/9seconds/mtg/v2/events"
+	"github.com/9seconds/mtg/v2/mtglib"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+type prometheusProcessor struct {
+	streams map[string]*streamInfo
+	factory *PrometheusFactory
+}
+
+func (p prometheusProcessor) EventStart(evt mtglib.EventStart) {
+	sInfo := &streamInfo{
+		createdAt: evt.CreatedAt,
+		clientIP:  evt.RemoteIP,
+	}
+	p.streams[evt.StreamID()] = sInfo
+
+	p.factory.metricActiveConnections.WithLabelValues(sInfo.IPType()).Inc()
+}
+
+func (p prometheusProcessor) EventFinish(evt mtglib.EventFinish) {
+	sInfo, ok := p.streams[evt.StreamID()]
+	if !ok {
+		return
+	}
+
+	defer delete(p.streams, evt.StreamID())
+
+	duration := evt.CreatedAt.Sub(sInfo.createdAt)
+
+	p.factory.metricActiveConnections.WithLabelValues(sInfo.IPType()).Dec()
+	p.factory.metricSessionDuration.Observe(float64(duration) / float64(time.Second))
+}
+
+func (p prometheusProcessor) EventConcurrencyLimited(evt mtglib.EventConcurrencyLimited) {
+	p.factory.metricConcurrencyLimited.Inc()
+}
+
+func (p prometheusProcessor) Shutdown() {
+	p.streams = make(map[string]*streamInfo)
+}
+
+type PrometheusFactory struct {
+	httpServer *http.Server
+
+	metricActiveConnections  *prometheus.GaugeVec
+	metricConcurrencyLimited prometheus.Counter
+	metricSessionDuration    prometheus.Histogram
+}
+
+func (p *PrometheusFactory) Make() events.Observer {
+	return prometheusProcessor{
+		streams: make(map[string]*streamInfo),
+		factory: p,
+	}
+}
+
+func (p *PrometheusFactory) Serve(listener net.Listener) error {
+	return p.httpServer.Serve(listener)
+}
+
+func (p *PrometheusFactory) Close() error {
+	return p.httpServer.Shutdown(context.Background())
+}
+
+func NewPrometheus(metricPrefix, httpPath string) *PrometheusFactory {
+	registry := prometheus.NewPedanticRegistry()
+	httpHandler := promhttp.HandlerFor(registry, promhttp.HandlerOpts{
+		EnableOpenMetrics: true,
+	})
+	mux := http.NewServeMux()
+
+	mux.Handle(httpPath, httpHandler)
+
+	factory := &PrometheusFactory{
+		httpServer: &http.Server{
+			Handler: mux,
+		},
+
+		metricActiveConnections: prometheus.NewGaugeVec(prometheus.GaugeOpts{
+			Namespace: metricPrefix,
+			Name:      MetricActiveConnection,
+			Help:      "A number of connections under active processing.",
+		}, []string{TagIPType}),
+		metricSessionDuration: prometheus.NewHistogram(prometheus.HistogramOpts{
+			Namespace: metricPrefix,
+			Name:      MetricSessionDuration,
+			Help:      "Session duration.",
+			Buckets: []float64{ // per 30 seconds
+				30,
+				60,
+				90,
+				120,
+				150,
+				180,
+				210,
+				240,
+				270,
+				300,
+			},
+		}),
+		metricConcurrencyLimited: prometheus.NewCounter(prometheus.CounterOpts{
+			Namespace: metricPrefix,
+			Name:      MetricConcurrencyLimited,
+			Help:      "A number of sessions that were rejected by concurrency limiter.",
+		}),
+	}
+
+	registry.MustRegister(factory.metricActiveConnections)
+	registry.MustRegister(factory.metricSessionDuration)
+	registry.MustRegister(factory.metricConcurrencyLimited)
+
+	return factory
+}