dotcloud/docker

package main

import (
    "context"
    "net"
    "net/http"
    "strings"
    "time"

    "github.com/containerd/log"
    metrics "github.com/docker/go-metrics"
)

func startMetricsServer(addr string) error {
    if addr == "" {
        return nil
    }
    if err := allocateDaemonPort(addr); err != nil {
        return err
    }
    l, err := net.Listen("tcp", addr)
    if err != nil {
        return err
    }
    mux := http.NewServeMux()
    mux.Handle("/metrics", metrics.Handler())
    go func() {
        log.G(context.TODO()).Infof("metrics API listening on %s", l.Addr())
        srv := &http.Server{
            Handler:           mux,
            ReadHeaderTimeout: 5 * time.Minute, // "G112: Potential Slowloris Attack (gosec)"; not a real concern for our use, so setting a long timeout.
        }
        if err := srv.Serve(l); err != nil && !strings.Contains(err.Error(), "use of closed network connection") {
            log.G(context.TODO()).WithError(err).Error("error serving metrics API")
        }
    }()
    return nil
}