You need to pass the WaitGroup as a pointer. This way, connectionsCount
creates a WaitGroup, increments it's counts, passes a copy of it to count
and then waits on the original; count, however, only Done()s its copy.
go vet should probably complain about that, as it contains an appropriate
marker to not be copied.
On Wed, Dec 21, 2016 at 10:35 AM, DM <subharaj.ma...@gmail.com> wrote:
> I am trying write a small golang program which will periodically execute lsof
> -i:<port> to check number of open TCP connections at a port. Code looks
> like below:-
>
> package main
>
> import (
> "fmt"
> "log"
> "os/exec"
> "strings"
> "sync"
> "time"
> )
>
> type Lsof struct {
> Command string
> Pid string
> User string
> Fd string
> Type string
> Device string
> SizeOff string
> Node string
> Name string
> TCPState string
> }
>
> //var result = make([]*Lsof, 0)
> var ports = []int{30001, 30002}
>
> func main() {
> done := make(chan bool)
> ticker := time.NewTicker(5 * time.Millisecond)
> go func() {
> for t := range ticker.C {
> fmt.Println("Tick at", t)
> connectionsCount()
> }
> }()
> <-done
> }
>
> func connectionsCount() {
> var wg sync.WaitGroup
> wg.Add(len(ports))
> for _, v := range ports {
> go count(v, wg)
> }
> wg.Wait()
> }
>
> func count(port int, wg sync.WaitGroup) {
> defer wg.Done()
> var tcpState = make(map[string]int)
> out, err := exec.Command("/bin/sh", "-c", fmt.Sprintf("lsof -i:%d",
> port)).Output()
> if err != nil {
> log.Fatal(err)
> }
> //fmt.Println(string(out))
> num := strings.Split(string(out), "\n")
> for no, n := range num {
> if no == 0 {
> continue
> }
> n = strings.TrimSpace(n)
> if len(n) <= 0 {
> continue
> }
> i := 0
> temp := strings.Split(n, " ")
> cleanedVal := make([]string, 10)
> for _, v := range temp {
> v = strings.TrimSpace(v)
> if len(v) <= 0 {
> continue
> }
> cleanedVal[i] = v
> i++
> }
> if len(cleanedVal) < 8 {
> //log.Println(n)
> continue
> }
> l := new(Lsof)
> l.Command = cleanedVal[0]
> l.Pid = cleanedVal[1]
> l.User = cleanedVal[2]
> l.Fd = cleanedVal[3]
> l.Type = cleanedVal[4]
> l.Device = cleanedVal[5]
> l.SizeOff = cleanedVal[6]
> l.Node = cleanedVal[7]
> l.Name = cleanedVal[8]
> if l.Node == "TCP" {
> l.TCPState = cleanedVal[9]
> count, ok := tcpState[l.TCPState]
> if !ok {
> tcpState[l.TCPState] = 1
> } else {
> tcpState[l.TCPState] = count + 1
> }
> }
> //fmt.Printf("\n%+v", *l)
> //result = append(result, l)
> }
> fmt.Printf("Port=%d ", port)
> for k, v := range tcpState {
> fmt.Printf("{TCP State=%s,Value=%d},", k, v)
> }
> fmt.Println()
> }
>
>
> But on running the program I am seeing the ticker is not ticking
> periodically. It is just ticking once:-
>
> Tick at 2016-12-21 14:37:03.847694697 +0530 ISTPort=30002 {TCP
> State=(LISTEN),Value=2},Port=30001 {TCP State=(LISTEN),Value=2},
>
> Can someone let me know what is going wrong?
>
> - Go Version - 1.7.3
>
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