Add metrics server to be included on each agent, including methods to…

… stop, start and register metrics

gossip/metrics.go

@@ -0,0 +1,63 @@
+/*
+   Copyright 2018 Banco Bilbao Vizcaya Argentaria, S.A.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package gossip
+
+import (
+	"context"
+	"net/http"
+	"time"
+
+	"github.com/bbva/qed/api/metricshttp"
+	"github.com/bbva/qed/log"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+type metricsServer struct {
+	server   *http.Server
+	registry *prometheus.Registry
+}
+
+func newMetricsServer(addr string) *metricsServer {
+	r := prometheus.NewRegistry()
+	return &metricsServer{
+		server: &http.Server{
+			Addr:    addr,
+			Handler: metricshttp.NewMetricsHTTP(r),
+		},
+		registry: r,
+	}
+}
+
+func (m metricsServer) start() {
+	if err := m.server.ListenAndServe(); err != http.ErrServerClosed {
+		log.Errorf("Can't start metrics HTTP server: %s", err)
+	}
+}
+
+func (m metricsServer) shutdown() {
+	ctx, _ := context.WithTimeout(context.Background(), 5*time.Second)
+	m.server.Shutdown(ctx)
+}
+
+func (m metricsServer) register(metric prometheus.Collector) {
+	if err := m.registry.Register(metric); err != nil {
+		log.Infof("metric not registered:", err)
+	} else {
+		log.Infof("metric registered.")
+	}
+}
+