Add helpers to stop and start metrics/profile servers

These are used throughout the Submariner project.

Signed-off-by: Stephen Kitt <[email protected]>

pkg/http/server.go

@@ -0,0 +1,78 @@
+/*
+SPDX-License-Identifier: Apache-2.0
+
+Copyright Contributors to the Submariner project.
+
+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 http
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"net/http/pprof"
+	"time"
+
+	"github.com/pkg/errors"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"github.com/submariner-io/admiral/pkg/log"
+	logf "sigs.k8s.io/controller-runtime/pkg/log"
+)
+
+var logger = log.Logger{Logger: logf.Log}
+
+type EndpointType int
+
+const (
+	Metrics EndpointType = 1 << iota
+	Profile
+	all = Metrics | Profile
+)
+
+type StopFunc func()
+
+// StartServer starts an HTTP server providing access to Prometheus metrics
+// and/or profiling information.
+// endpoints specifies the endpoints to provide; it can be Metrics, Profile, or both (ored).
+// port specifies the TCP port on which the server listens.
+// The returned function should be called to shut down the server, typically at process exit
+// using defer in the main() function.
+func StartServer(endpoints EndpointType, port int) StopFunc {
+	if endpoints&all == 0 {
+		return func() {}
+	}
+
+	srv := &http.Server{Addr: fmt.Sprintf(":%d", port), ReadHeaderTimeout: 60 * time.Second}
+
+	if endpoints&Metrics != 0 {
+		http.Handle("/metrics", promhttp.Handler())
+	}
+
+	if endpoints&Profile != 0 {
+		http.HandleFunc("/debug", pprof.Profile)
+	}
+
+	go func() {
+		if err := srv.ListenAndServe(); !errors.Is(err, http.ErrServerClosed) {
+			logger.Errorf(err, "Error starting metrics/profile HTTP server")
+		}
+	}()
+
+	return func() {
+		if err := srv.Shutdown(context.TODO()); err != nil {
+			logger.Errorf(err, "Error shutting down metrics/profile HTTP server")
+		}
+	}
+}