main.go

package main

import (
	"io"
	"log"
	"os"
	"os/exec"
	"sync"
)

///////////////////
// Setup Logging //
///////////////////

const defaultLog = "/tmp/go-entrypoint.log"

type logger struct {
	filename string
	*log.Logger
}

var instance *logger
var once sync.Once

func getLogger() *logger {
	once.Do(func() {
		instance = createLogger(defaultLog)
	})
	return instance
}

func createLogger(fname string) *logger {
	file, _ := os.OpenFile(fname, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0777)

	return &logger{
		filename: fname,
		Logger:   log.New(file, "go-entrypoint: ", log.Lshortfile),
	}
}

///////////////////
// Setup Command //
///////////////////

func setupCommand(processPath, filePath string) (*exec.Cmd, io.WriteCloser) {
	cmd := exec.Command(processPath, filePath)

	// Create stdin pipe
	in, err := cmd.StdinPipe()
	if err != nil {
		panic(err)
	}
	return cmd, in

}

//////////
// Main //
//////////

func main() {
	logger := getLogger()
	logger.Println("Inside a go process!")

	p := "/opt/python/bin/python"
	f := "reflector.py"
	logger.Printf("Setting up: %s %s\n", p, f)
	cmd, cin := setupCommand(p, f)
	defer cin.Close()

	logger.Println("Starting External Process...")

	cmd.Stdout = os.Stdout
	cmd.Stdin = os.Stdin
	cmd.Stderr = os.Stderr

	if err := cmd.Start(); err != nil {
		panic(err)
	}
	err := cmd.Wait()

	if err != nil {
		logger.Println("Non-zero exit code: ", err)
	}

	logger.Println("Exiting from golang...")
}