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udp_server.go
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udp_server.go
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package main
// udp_server - UDP Server implementation with optional support to send UDP messages
// to StompAMQ endpoint
//
// Copyright (c) 2020 - Valentin Kuznetsov <[email protected]>
//
import (
"bytes"
"encoding/json"
"errors"
"flag"
"fmt"
"log"
"net"
"net/http"
"net/url"
"os"
"runtime"
"strings"
"time"
"github.com/go-stomp/stomp"
rotatelogs "github.com/lestrrat-go/file-rotatelogs"
)
// version of the code
var version string
// global pointer to Stomp connection
var stompConn *stomp.Conn
// Configuration stores server configuration parameters
type Configuration struct {
Port int `json:"port"` // server port number
IPAddr string `json:"ipAddr"` // server ip address to bind
MonitorPort int `json:"monitorPort"` // server monitor port number
MonitorInterval int `json:"monitorInterval"` // server monitor interval
BufSize int `json:"bufSize"` // buffer size
StompURI string `json:"stompURI"` // StompAMQ URI
StompLogin string `json:"stompLogin"` // StompAQM login name
StompPassword string `json:"stompPassword"` // StompAQM password
StompIterations int `json:"stompIterations"` // Stomp iterations
SendTimeout int `json:"sendTimeout"` // heartbeat send timeout in seconds
RecvTimeout int `json:"recvTimeout"` // heartbeat recv timeout in seconds
HeartBeatGracePeriod float64 `json:"heartBeatGracePeriod"` // is used to calculate the read heart-beat timeout
Endpoint string `json:"endpoint"` // StompAMQ endpoint
ContentType string `json:"contentType"` // ContentType of UDP packet
LogFile string `json:"logFile"` // log file name
Verbose bool `json:"verbose"` // verbose output
}
// custom rotate logger
type rotateLogWriter struct {
RotateLogs *rotatelogs.RotateLogs
}
func (w rotateLogWriter) Write(data []byte) (int, error) {
return w.RotateLogs.Write([]byte(utcMsg(data)))
}
// helper function to use proper UTC message in a logger
func utcMsg(data []byte) string {
s := string(data)
v, e := url.QueryUnescape(s)
if e == nil {
return v
}
return s
}
var Config Configuration
// parseConfig parse given config file
func parseConfig(configFile string) error {
data, err := os.ReadFile(configFile)
if err != nil {
log.Println("Unable to read", err)
return err
}
err = json.Unmarshal(data, &Config)
if err != nil {
log.Println("Unable to parse", err)
return err
}
// default values
if Config.Port == 0 {
Config.Port = 9331 // default port
}
if Config.MonitorPort == 0 {
Config.MonitorPort = 9330 // default port
}
if Config.MonitorInterval == 0 {
Config.MonitorInterval = 10 // default 10 seconds
}
if Config.BufSize == 0 {
Config.BufSize = 1024 // 1 KByte
}
if Config.StompIterations == 0 {
Config.StompIterations = 3 // number of Stomp attempts
}
if Config.ContentType == "" {
Config.ContentType = "application/json"
}
if Config.HeartBeatGracePeriod == 0 {
Config.HeartBeatGracePeriod = 1
}
if Config.SendTimeout == 0 {
Config.SendTimeout = 600 // in seconds
}
if Config.RecvTimeout == 0 {
Config.RecvTimeout = 0 // in seconds
}
return nil
}
func info() string {
goVersion := runtime.Version()
tstamp := time.Now().Format("2006-02-01")
return fmt.Sprintf("UDPServer git=%s go=%s date=%s", version, goVersion, tstamp)
}
// StompConnection returns Stomp connection
func StompConnection() (*stomp.Conn, error) {
if Config.StompURI == "" {
err := errors.New("Unable to connect to Stomp, not URI")
return nil, err
}
if Config.StompLogin == "" {
err := errors.New("Unable to connect to Stomp, not login")
return nil, err
}
if Config.StompPassword == "" {
err := errors.New("Unable to connect to Stomp, not password")
return nil, err
}
conn, err := stomp.Dial("tcp",
Config.StompURI,
stomp.ConnOpt.Login(Config.StompLogin, Config.StompPassword),
stomp.ConnOpt.HeartBeat(time.Duration(Config.SendTimeout)*time.Second, time.Duration(Config.RecvTimeout)*time.Second),
stomp.ConnOpt.HeartBeatGracePeriodMultiplier(Config.HeartBeatGracePeriod),
)
if err != nil {
log.Printf("Unable to connect to %s, error %v", Config.StompURI, err)
}
if Config.Verbose {
log.Printf("connected to StompAMQ server %s %v", Config.StompURI, conn)
}
return conn, err
}
func sendDataToStomp(data []byte) {
for i := 0; i < Config.StompIterations; i++ {
err := stompConn.Send(Config.Endpoint, Config.ContentType, data)
if err != nil {
if i == Config.StompIterations-1 {
log.Printf("unable to send data to %s, data %s, error %v, iteration %d", Config.Endpoint, string(data), err, i)
} else {
log.Printf("unable to send data to %s, error %v, iteration %d", Config.Endpoint, err, i)
}
if stompConn != nil {
stompConn.Disconnect()
}
stompConn, err = StompConnection()
} else {
if Config.Verbose {
log.Printf("send data to StompAMQ endpoint %s", Config.Endpoint)
}
return
}
}
}
// udp server implementation
func udpServer() {
const maxFailedPacketLength = 1000 // maximum length of the failed packet to be printed
udpAddr := &net.UDPAddr{Port: Config.Port}
// if configuration provides explicitly IPAddr to bind use it here
if Config.IPAddr != "" {
udpAddr = &net.UDPAddr{
Port: Config.Port,
IP: net.ParseIP(Config.IPAddr),
}
}
conn, err := net.ListenUDP("udp", udpAddr)
if err != nil {
panic(err)
}
defer conn.Close()
log.Printf("UDP server %s\n", conn.LocalAddr().String())
stompConn, err = StompConnection()
// defer stomp connection if it exists
if stompConn != nil {
defer stompConn.Disconnect()
}
// set initial buffer size to handle UDP packets
bufSize := Config.BufSize
for {
// create a buffer we'll use to read the UDP packets
buffer := make([]byte, bufSize)
// read UDP packets
rlen, remote, err := conn.ReadFromUDP(buffer[:])
if err != nil {
log.Printf("Unable to read UDP packet, error %v", err)
// clear-up our buffer
buffer = buffer[:0]
continue
}
data := buffer[:rlen]
// if we receive ping message from monitoring server
// we will send POST HTTP request to it with our pong reply
if string(data) == "ping" {
if Config.Verbose {
log.Println("received monitor", string(data))
}
// send POST request to monitoring server, but don't care about response
s := []byte("pong")
rurl := fmt.Sprintf("http://localhost:%d", Config.MonitorPort)
http.Post(rurl, "text/plain", bytes.NewBuffer(s))
// clean-up our buffer
buffer = buffer[:0]
continue
}
// try to parse the data, we are expecting JSON
var packet map[string]interface{}
err = json.Unmarshal(data, &packet)
if err != nil {
log.Printf("unable to unmarshal UDP packet into JSON, error %v\n", err)
e := string(err.Error())
if strings.Contains(e, "invalid character") {
// truncate the malformed JSON if it exceeds the maximum length
// and dump it
failedData := string(data)
if len(failedData) > maxFailedPacketLength {
failedData = failedData[:maxFailedPacketLength] + "..."
}
log.Println(failedData)
} else if strings.Contains(e, "unexpected end of JSON input") {
// let's increse buf size to adjust to the packet size
bufSize = bufSize * 2
if bufSize > 1024*Config.BufSize {
log.Fatalf("unable to unmarshal UDP packet into JSON with buffer size %d", bufSize)
}
}
// at this point we already read from UDP connection and our
// message didn't fit into buffer therefore we may skip the rest
// clear-up our buffer and continue
buffer = buffer[:0]
continue
}
// dump message to our log
if Config.Verbose {
sdata := strings.TrimSpace(string(data))
log.Printf("received: %s from %s\n", sdata, remote)
}
// check if the message has a key named "type" and rename it to "read_type"
if val, ok := packet["type"]; ok {
packet["read_type"] = val
delete(packet, "type")
}
// send data to Stomp endpoint
if Config.Endpoint != "" && stompConn != nil {
newData, err := json.Marshal(packet)
if err != nil {
log.Printf("unable to marshal UDP packet into JSON, error %v\n", err)
// truncate the failed packet if it exceeds the maximum length
failedPacket := fmt.Sprint(packet)
if len(failedPacket) > maxFailedPacketLength {
failedPacket = failedPacket[:maxFailedPacketLength] + "..."
}
log.Println(failedPacket) // dump the truncated message to the log
// clear-up our buffer
buffer = buffer[:0]
continue
}
if Config.Verbose {
sNewData := strings.TrimSpace(string(newData))
log.Printf("sent to AMQ: %s\n", sNewData)
}
sendDataToStomp(newData)
}
// clear-up our buffer
buffer = buffer[:0]
}
}
func main() {
var config string
flag.StringVar(&config, "config", "", "configuration file")
var version bool
flag.BoolVar(&version, "version", false, "version")
flag.Parse()
if version {
log.Println(info())
os.Exit(0)
}
err := parseConfig(config)
// set log file or log output
if Config.LogFile != "" {
logName := Config.LogFile + "-%Y%m%d"
hostname, err := os.Hostname()
if err == nil {
logName = Config.LogFile + "-" + hostname + "-%Y%m%d"
}
rl, err := rotatelogs.New(logName)
if err == nil {
rotlogs := rotateLogWriter{RotateLogs: rl}
log.SetOutput(rotlogs)
}
log.SetFlags(log.LstdFlags | log.Lshortfile)
} else {
// log time, filename, and line number
if Config.Verbose {
log.SetFlags(log.LstdFlags | log.Lshortfile)
} else {
log.SetFlags(log.LstdFlags)
}
}
if err == nil {
udpServer()
}
log.Fatal(err)
}