[#164] scripts: Add metrics description exporter

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

scripts/export-metrics/main.go

@@ -0,0 +1,56 @@
+package main
+
+import (
+	"encoding/json"
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"os"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/metrics"
+)
+
+var (
+	node = flag.String("node", "", "File to export storage node metrics to.")
+	ir   = flag.String("ir", "", "File to export innerring node metrics to.")
+)
+
+func main() {
+	flag.Parse()
+
+	if *node != "" && *ir != "" {
+		fmt.Println("-node and -ir flags are mutually exclusive")
+		os.Exit(1)
+	}
+
+	var filename string
+	switch {
+	case *node != "":
+		_ = metrics.NewNodeMetrics()
+		filename = *node
+	case *ir != "":
+		_ = metrics.NewInnerRingMetrics()
+		filename = *ir
+
+	default:
+		flag.Usage()
+		os.Exit(1)
+	}
+
+	ds, err := metrics.DescribeAll()
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Could not parse metric descriptions: %v\n", err)
+		os.Exit(1)
+	}
+
+	data, err := json.Marshal(ds)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Could not parse marshal: %v\n", err)
+		os.Exit(1)
+	}
+
+	if err := ioutil.WriteFile(filename, data, 0644); err != nil {
+		fmt.Fprintf(os.Stderr, "Could write to file: %v\n", err)
+		os.Exit(1)
+	}
+}