devlogforward/main.go

package main

import (
	"encoding/json"
	"flag"
	"log"
	"net"
	"os"
	"strings"
	"text/template"
	"time"

	"gopkg.in/mcuadros/go-syslog.v2"
)

func udpConnect(addr string) (conn *net.UDPConn) {
	if addr != "" {
		uaddr, err := net.ResolveUDPAddr("udp4", addr)
		if err != nil {
			log.Printf("error resolving udp address: %s (%s)\n", addr, err)
		}
		if uaddr != nil {
			conn, err = net.DialUDP("udp4", nil, uaddr)
			if err != nil {
				log.Printf("error connecting to udp address: %s (%s)", addr, err)
			} else {
				log.Printf("udp client initialized")
			}
		}
	}

	return
}

type mapFlag map[string]string

func (i *mapFlag) String() string {
	return ""
}
func (i *mapFlag) Set(v string) error {
	s := strings.Split(v, "=")
	if len(s) > 1 && s[0] != "" {
		(*i)[s[0]] = strings.Join(s[1:], "=")
	}
	return nil
}

func main() {
	socketFile := flag.String("socket", "/dev/log", "socket file")
	stdoutTpl := flag.String("stdoutTpl", "[{{.timestamp}}] {{.content}}", "stdout line template, variables are: timestamp, content, facility, hostname, priority, severity, tag")
	udpAddr := flag.String("udpAddr", "", "udp address, format is host:port")
	udpTpl := flag.String("udpTpl", "{{ json . }}", "udp line template, see stdoutTpl for variables")
	customVars := make(mapFlag)
	flag.Var(&customVars, "var", "custom variable, pe. type=error, can be used multiple times")

	flag.Parse()

	fMap := template.FuncMap{
		"json": func(i interface{}) string {
			b, _ := json.Marshal(i)
			return string(b)
		},
	}

	stdoutTemplate := template.Must(template.New("stdout").Funcs(fMap).Parse(*stdoutTpl + "\n"))
	udpTemplate := template.Must(template.New("udp").Funcs(fMap).Parse(*udpTpl + "\n"))

	udpConnection := udpConnect(*udpAddr)
	go func() {
		for range time.Tick(time.Second * 60) {
			if udpConnection == nil {
				udpConnection = udpConnect(*udpAddr)
			}
		}
	}()

	channel := make(syslog.LogPartsChannel, 1000)
	handler := syslog.NewChannelHandler(channel)

	udpChannel := make(syslog.LogPartsChannel, 1000)

	server := syslog.NewServer()
	// server.SetFormat(syslog.RFC5424)
	server.SetFormat(syslog.Automatic)
	server.SetHandler(handler)
	//err := server.ListenUDP("0.0.0.0:514")
	if _, err := os.Stat(*socketFile); err == nil {
		os.Remove(*socketFile)
	}
	err := server.ListenUnixgram(*socketFile)

	if err != nil {
		panic(err)
	}

	os.Chmod(*socketFile, 0666)

	err = server.Boot()
	if err != nil {
		panic(err)
	}

	go func(channel syslog.LogPartsChannel) {
		for logParts := range channel {
			for k, v := range customVars {
				logParts[k] = v
			}
			stdoutTemplate.Execute(os.Stdout, logParts)
			udpChannel <- logParts
			// fmt.Println(logParts)
		}
	}(channel)

	go func(channel syslog.LogPartsChannel) {
		for logParts := range channel {
			if udpConnection != nil {
				err := udpTemplate.Execute(udpConnection, logParts)
				if err != nil {
					log.Printf("error executing udp template: %s", err)
				}
			}
		}
	}(udpChannel)

	server.Wait()
}