cmd/metric-receiver: restore minimal metrics server

Change-Id: I33ac9d7ccf21f41ef3077c64506df63607ed6b15

cmd/metric-receiver/main.go

@@ -0,0 +1,49 @@
+// Copyright (C) 2019 Storj Labs, Inc.
+// See LICENSE for copying information.
+
+package main
+
+import (
+	"flag"
+	"fmt"
+
+	"github.com/spf13/cobra"
+
+	"storj.io/common/telemetry"
+	"storj.io/private/process"
+)
+
+var (
+	addr = flag.String("addr", ":9000", "address to listen for metrics on")
+)
+
+func main() {
+	process.Exec(&cobra.Command{
+		Use:   "metric-receiver",
+		Short: "receive metrics",
+		RunE:  run,
+	})
+}
+
+func run(cmd *cobra.Command, args []string) (err error) {
+	ctx, _ := process.Ctx(cmd)
+	s, err := telemetry.Listen(*addr)
+	if err != nil {
+		return err
+	}
+	defer printError(s.Close)
+
+	fmt.Printf("listening on %s\n", s.Addr())
+	return s.Serve(ctx, telemetry.HandlerFunc(handle))
+}
+
+func handle(application, instance string, key []byte, val float64) {
+	fmt.Printf("%s %s %s %v\n", application, instance, string(key), val)
+}
+
+func printError(fn func() error) {
+	err := fn()
+	if err != nil {
+		fmt.Println(err)
+	}
+}