main.go

package main

import (
	"encoding/binary"
	"fmt"
	io_prometheus_client "github.com/prometheus/client_model/go"
	"google.golang.org/protobuf/proto"
	"io"
	"net/http"
)

func main() {
	url := "http://localhost:8888/metrics"

	req, err := http.NewRequest("GET", url, nil)
	if err != nil {
		panic(err)
	}
	req.Header.Set("Accept", "application/vnd.google.protobuf; proto=io.prometheus.client.MetricFamily; encoding=delimited")

	client := &http.Client{}
	resp, err := client.Do(req)
	if err != nil {
		panic(err)
	}
	defer resp.Body.Close()

	for {
		// First read varint size
		sizeBuf := make([]byte, 10) // Max varint size for 64-bit int
		var bytesRead int
		for i := 0; i < len(sizeBuf); i++ {
			n, err := resp.Body.Read(sizeBuf[i : i+1])
			if err != nil {
				if err == io.EOF {
					return // Done reading
				}
				panic(fmt.Sprintf("Failed reading size: %v", err))
			}
			bytesRead += n
			if sizeBuf[i]&0x80 == 0 {
				break // End of varint
			}
		}
		size, _ := binary.Uvarint(sizeBuf[:bytesRead])

		// Now read the message of that size
		msgBuf := make([]byte, size)
		_, err = io.ReadFull(resp.Body, msgBuf)
		if err != nil {
			panic(fmt.Sprintf("Failed reading message body: %v", err))
		}

		mf := &io_prometheus_client.MetricFamily{}
		err = proto.Unmarshal(msgBuf, mf)
		if err != nil {
			panic(fmt.Sprintf("Failed to unmarshal: %v", err))
		}

		fmt.Printf("Metric: %s, Type: %s\n", mf.GetName(), mf.GetType().String())

		for _, m := range mf.Metric {
			fmt.Print("  Labels: {")
			for i, label := range m.Label {
				if i > 0 {
					fmt.Print(", ")
				}
				fmt.Printf("%s=\"%s\"", label.GetName(), label.GetValue())
			}
			fmt.Println("}")
		}
	}
}