personal/q3k/minecraft/plugin/hscloud/bridge/main.go

package main

import (
	"flag"
	"fmt"
	"log"
	"net/http"

	"google.golang.org/grpc"

	pb "code.hackerspace.pl/hscloud/personal/q3k/minecraft/plugin/hscloud/proto"
)

var (
	flagPlugin string
	flagListen string
)

func main() {
	flag.StringVar(&flagPlugin, "plugin", "minecraft.wypierdolzpolski.pl:2137", "address of gRPC plugin")
	flag.StringVar(&flagListen, "listen", "0.0.0.0:8081", "address to listen at")
	flag.Parse()

	conn, err := grpc.Dial(flagPlugin, grpc.WithInsecure())
	if err != nil {
		log.Fatalf("Dial(%q): %v", flagPlugin, err)
	}

	client := pb.NewIntrospectorClient(conn)

	http.HandleFunc("/metrics", func(w http.ResponseWriter, r *http.Request) {
		res, err := client.Status(r.Context(), &pb.StatusRequest{})
		if err != nil {
			http.Error(w, "internal server error", 500)
			log.Printf("Status error: %v", err)
		}

		fmt.Fprintf(w, "# HELP minecraft_players_online Total number of players online.\n")
		fmt.Fprintf(w, "# TYPE minecraft_players_online gauge\n")
		fmt.Fprintf(w, "minecraft_players_online %d\n", len(res.Players))
	})

	log.Printf("Listening on %s", flagListen)
	err = http.ListenAndServe(flagListen, nil)
	if err != nil {
		log.Fatalf("ListenAndServe: %v", err)
	}
}