chore: Adds basic commands and protocol.

api/gosrc/externalbackendlauncher/main.go

@@ -0,0 +1,133 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+	"time"
+
+	"git.greysoh.dev/imterah/nextnet/backendlauncher"
+	"github.com/charmbracelet/log"
+)
+
+type WriteLogger struct {
+	UseError bool
+}
+
+func (writer WriteLogger) Write(p []byte) (n int, err error) {
+	logSplit := strings.Split(string(p), "\n")
+
+	for _, line := range logSplit {
+		if writer.UseError {
+			log.Errorf("application: %s", line)
+		} else {
+			log.Infof("application: %s", line)
+		}
+	}
+
+	return len(p), err
+}
+
+func main() {
+	tempDir, err := os.MkdirTemp("", "nextnet-sockets-")
+	logLevel := os.Getenv("NEXTNET_LOG_LEVEL")
+
+	if logLevel != "" {
+		switch logLevel {
+		case "debug":
+			log.SetLevel(log.DebugLevel)
+
+		case "info":
+			log.SetLevel(log.InfoLevel)
+
+		case "warn":
+			log.SetLevel(log.WarnLevel)
+
+		case "error":
+			log.SetLevel(log.ErrorLevel)
+
+		case "fatal":
+			log.SetLevel(log.FatalLevel)
+		}
+	}
+
+	if len(os.Args) != 3 {
+		log.Fatalf("missing arguments! example: ./externalbackendlauncher <backend executable> <file with backend arguments>")
+	}
+
+	executablePath := os.Args[1]
+	executableParamsPath := os.Args[2]
+
+	_, err = os.ReadFile(executableParamsPath)
+
+	if err != nil {
+		log.Fatalf("could not read backend parameters: %s", err.Error())
+	}
+
+	_, err = os.Stat(executablePath)
+
+	if err != nil {
+		log.Fatalf("failed backend checks: %s", err.Error())
+	}
+
+	log.Debug("running socket acquisition")
+
+	sockPath, sockListener, err := backendlauncher.GetUnixSocket(tempDir)
+
+	if err != nil {
+		log.Fatalf("failed to acquire unix socket: %s", err.Error())
+	}
+
+	log.Debugf("acquisition was successful: %s", sockPath)
+
+	go func() {
+		log.Debug("entering execution loop (in auxiliary goroutine)...")
+
+		for {
+			log.Info("waiting for Unix socket connections...")
+			sock, err := sockListener.Accept()
+
+			if err != nil {
+				log.Warnf("failed to accept socket connection: %s", err.Error())
+			}
+
+			defer sock.Close()
+		}
+	}()
+
+	log.Debug("entering execution loop (in main goroutine)...")
+
+	stdout := WriteLogger{
+		UseError: false,
+	}
+
+	stderr := WriteLogger{
+		UseError: true,
+	}
+
+	for {
+		log.Info("starting process...")
+		// TODO: can we reuse cmd?
+		cmd := exec.Command(executablePath)
+		cmd.Env = append(cmd.Env, fmt.Sprintf("NEXTNET_API_SOCK=%s", sockPath))
+
+		cmd.Stdout = stdout
+		cmd.Stderr = stderr
+
+		err := cmd.Run()
+
+		if err != nil {
+			if err, ok := err.(*exec.ExitError); ok {
+				log.Warnf("backend died with exit code '%d' and with error '%s'", err.ExitCode(), err.Error())
+			} else {
+				log.Warnf("backend died with error: %s", err.Error())
+			}
+		} else {
+			log.Info("process exited gracefully.")
+		}
+
+		log.Info("sleeping 5 seconds, and then restarting process")
+		time.Sleep(5 * time.Millisecond)
+	}
+}