feat: add signal-bound server supervisor command

server/cmd/game-server-supervisor/main.go

@@ -0,0 +1,71 @@
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"os"
+	"os/signal"
+	"syscall"
+	"time"
+
+	"github.com/cosmic-clash/cosmic-clash/server/supervisor"
+)
+
+const usageText = `Usage: game-server-supervisor [options] -- <game-server-command> [args...]
+
+The child command is started only after an allocated Agones endpoint has been
+validated and, when configured, an explicit process-ready probe succeeds.
+SIGTERM/SIGINT requests authenticated drain before the bounded grace deadline.
+`
+
+func main() {
+	args := os.Args[1:]
+	separator := -1
+	for i, arg := range args {
+		if arg == "--" {
+			separator = i
+			break
+		}
+	}
+	if separator < 0 || separator == len(args)-1 {
+		fmt.Fprint(os.Stderr, usageText)
+		os.Exit(2)
+	}
+
+	options := flag.NewFlagSet("game-server-supervisor", flag.ContinueOnError)
+	options.SetOutput(os.Stderr)
+	sdkBaseURL := options.String("sdk-base-url", "", "Agones SDK REST base URL; empty enables direct mode")
+	readyURL := options.String("ready-url", "", "explicit process-ready probe URL")
+	drainURL := options.String("drain-url", "", "loopback drain URL")
+	drainTokenEnv := options.String("drain-token-env", "COSMIC_CLASH_DRAIN_TOKEN", "environment variable containing the drain bearer token")
+	transport := options.String("transport", "enet", "enet or steam_sdr")
+	grace := options.Duration("drain-grace", supervisor.DefaultDrainGrace, "maximum graceful drain duration")
+	if err := options.Parse(args[:separator]); err != nil {
+		os.Exit(2)
+	}
+
+	token := ""
+	if *drainTokenEnv != "" {
+		token = os.Getenv(*drainTokenEnv)
+	}
+	s, err := supervisor.New(supervisor.Config{
+		Command:      args[separator+1:],
+		SDKBaseURL:   *sdkBaseURL,
+		ReadyURL:     *readyURL,
+		DrainURL:     *drainURL,
+		DrainToken:   token,
+		Transport:    *transport,
+		ReadyTimeout: 30 * time.Second,
+	})
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "game-server-supervisor: %v\n", err)
+		os.Exit(2)
+	}
+	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
+	defer stop()
+	if err := s.Run(ctx, *grace); err != nil {
+		fmt.Fprintf(os.Stderr, "game-server-supervisor: %v\n", err)
+		os.Exit(1)
+	}
+}