Initial version of code

Author: Linus Wallgren

go.mod

@@ -0,0 +1 @@
+module github.com/AiflooAB/prometheus-mac-proxy

main.go

@@ -0,0 +1,10 @@
+package main
+
+import (
+	"github.com/AiflooAB/prometheus-mac-proxy/pkg/mac"
+	"github.com/AiflooAB/prometheus-mac-proxy/pkg/proxy"
+)
+
+func main() {
+	proxy.Start(mac.NewFileTransformer)
+}

pkg/mac/mac.go

@@ -0,0 +1,72 @@
+package mac
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"os"
+	"regexp"
+	"strings"
+
+	"github.com/AiflooAB/prometheus-mac-proxy/pkg/proxy"
+)
+
+type macTransformer struct {
+	ipmac map[string]string
+}
+
+func NewFileTransformer() proxy.Transformer {
+	return &macTransformer{
+		ipmac: readIPMacMap(),
+	}
+}
+
+func (trans *macTransformer) Transform(line string) string {
+	mac := getMac(trans.ipmac, line)
+
+	return strings.Replace(line, "ip=", fmt.Sprintf("mac=\"%s\",ip=", mac), 1)
+}
+
+var ipRegex = regexp.MustCompile(`ip="(.+?)"`)
+
+func getMac(ipmac map[string]string, line string) string {
+	matches := ipRegex.FindStringSubmatch(line)
+	if len(matches) >= 1 {
+		ip := matches[1]
+		mac, found := ipmac[ip]
+		if found {
+			return mac
+		}
+	}
+	return "UNKNOWN"
+}
+
+func readIPMacMap() map[string]string {
+	ipmac := make(map[string]string)
+	file, err := os.Open("./all") // TODO
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		line := scanner.Text()
+		ip, mac := parsePromscanLine(line)
+		ipmac[ip] = mac
+	}
+
+	if err := scanner.Err(); err != nil {
+		fmt.Fprintf(os.Stderr, "Got error while reading file: %v\n", err)
+	}
+
+	return ipmac
+}
+
+func parsePromscanLine(line string) (string, string) {
+	var datetime string
+	var ip string
+	var mac string
+	fmt.Sscanf(line, "%s %s %s", &datetime, &ip, &mac)
+	return ip, mac
+}

pkg/mac/mac_test.go

@@ -0,0 +1,44 @@
+package mac
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestTransformPrometheusline(t *testing.T) {
+	tests := []struct {
+		name     string
+		ipmac    map[string]string
+		line     string
+		expected string
+	}{
+		{
+			"Missing mac",
+			map[string]string{},
+			`fping_response_duration_seconds_bucket{ip="192.168.1.153",le="0.4096"} 7652`,
+			`fping_response_duration_seconds_bucket{mac="UNKNOWN",ip="192.168.1.153",le="0.4096"} 7652`,
+		},
+		{
+			"Simple mac exists",
+			map[string]string{"192.168.1.153": "00:11:22:33:44:55:66"},
+			`fping_response_duration_seconds_bucket{ip="192.168.1.153",le="0.4096"} 7652`,
+			`fping_response_duration_seconds_bucket{mac="00:11:22:33:44:55:66",ip="192.168.1.153",le="0.4096"} 7652`,
+		},
+		{
+			"Unrelated line",
+			map[string]string{},
+			`# TYPE go_memstats_next_gc_bytes gauge`,
+			`# TYPE go_memstats_next_gc_bytes gauge`,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			transformer := &macTransformer{ipmac: test.ipmac}
+			parsed := transformer.Transform(test.line)
+			if !reflect.DeepEqual(test.expected, parsed) {
+				t.Errorf("\n%+v\n!=\n%+v", test.expected, parsed)
+			}
+		})
+	}
+}

pkg/proxy/proxy.go

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+package proxy
+
+import (
+	"bufio"
+	"io"
+	"log"
+	"net/http"
+)
+
+type Transformer interface {
+	Transform(string) string
+}
+
+func Start(transformerConstructor func() Transformer) {
+	handleHTTP := func(w http.ResponseWriter, req *http.Request) {
+		resp, err := http.Get("http://localhost:9299/metrics")
+
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusServiceUnavailable)
+			return
+		}
+		defer resp.Body.Close()
+
+		copyHeader(w.Header(), resp.Header)
+		w.WriteHeader(resp.StatusCode)
+
+		transformer := transformerConstructor()
+
+		scanner := bufio.NewScanner(resp.Body)
+		for scanner.Scan() {
+			line := scanner.Text()
+
+			io.WriteString(w, transformer.Transform(line))
+			w.Write([]byte("\n"))
+		}
+	}
+
+	http.HandleFunc("/metrics", handleHTTP)
+	log.Fatal(http.ListenAndServe("0.0.0.0:19299", nil))
+}
+
+func copyHeader(dst, src http.Header) {
+	for k, vv := range src {
+		for _, v := range vv {
+			dst.Add(k, v)
+		}
+	}
+}