log.go


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package proxy

import (
	"log"
	"os"
	"path/filepath"
)

var logWriter *LogWriter

type LogWriter struct {
	f *os.File
}

// Write writes the input data to os.Stderr and the log file.
// It returns the number of bytes written and an error.
func (lw *LogWriter) Write(p []byte) (n int, err error) {
	n, err = os.Stderr.Write(p)
	if err != nil {
		return
	}

	return lw.f.Write(p)
}

func init() {
	log.SetPrefix("[proxy] ")
	log.SetFlags(log.Flags() | log.Lmsgprefix)

	executable, err := os.Executable()
	if err != nil {
		log.Fatal(err)
	}

	path := filepath.Dir(executable) + "/latest.log"
	f, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0666)
	if err != nil {
		log.Fatal(err)
	}

	go func() {
		defer f.Close()
		select {}
	}()

	logWriter = &LogWriter{f}
	log.SetOutput(logWriter)
}