portping - connect to massive ip:port addresses and find out what are not connectable

portping.go

/*
    Connect to massive ip:port addresses and find out what are not connectable.
    
    Port variant of PingInfoView.
    
    It only accepts input from a CSV file with following format:
        10.12.15.121:8080,xxxxx,zzzzzz
        10.12.15.4:8080,aaaaa,bbbbbb
        10.12.15.35:8080,ddddd,eeeeee
        ...
 */

package main

import (
    "bufio"
    "encoding/csv"
    "fmt"
    "io"
    "log"
    "net"
    "os"
    "time"
)


type VipInfo struct {
    Addr  string
    VipName string
    Lb string
}


func IsConnectable(addr string) bool {
    conn, err := net.DialTimeout("tcp", addr, 300*time.Millisecond)
    if err != nil {
        return false
    }

    defer conn.Close()

    return true
}


func GetUnconnectableVips(vips []VipInfo) []string {
    rv := []string{}
    sem := make(chan bool, 200)
    for i := 0; i < len(vips); i++ {
        sem <- true
        vip := vips[i]
        addr := vip.Addr
        vipName := vip.VipName
        lb := vip.Lb
        go func(addr string) {
            if ! IsConnectable(addr) {
                msg := fmt.Sprintf("%20s, %30s, %25s", addr, vipName, lb)
                rv = append(rv, msg)
            }
            <- sem
        }(addr)
    }
    for i := 0; i < cap(sem); i++ {
        sem <- true
    }
    return rv
}


func usage() {
    fmt.Fprintf(os.Stderr, "usage: %s csv_file\n", os.Args[0])
    fmt.Println("csv_file must be in format like '10.12.15.121:8080,xxxxx,zzzzzz'.")
    os.Exit(2)
}


func main(){
    if len(os.Args) != 2 {
        usage()
    }

    csvFile, _ := os.Open(os.Args[1])
    reader := csv.NewReader(bufio.NewReader(csvFile))
    var vips []VipInfo
    for {
        line, err := reader.Read()
        if err == io.EOF {
            break
        } else if err != nil {
            log.Fatal(err)
        }
        vips = append(vips, VipInfo{
            Addr: line[0],
            VipName: line[1],
            Lb:  line[2],
        })
    }

    fmt.Println("running portping...")

    unconnectableVips := GetUnconnectableVips(vips)

    for i := 0; i < len(unconnectableVips); i++ {
        vipLb := unconnectableVips[i]
        fmt.Printf("%s, not able to connect\n", vipLb)
    }

    fmt.Println("(all other VIPs are good)")
}

x_example_input.csv

x_example_output.txt

$ wc -l x_example_input.csv
3353 example_input.csv
$
$ time ./portping lvslb-vips.csv
running portping...
  10.12.15.121:8080,    xxxxx,    zzzzzz,    not able to connect
    10.12.15.4:8080,    aaaaa,    bbbbbb,    not able to connect
   10.12.15.35:8080,    ddddd,    eeeeee,    not able to connect
(all other VIPs are good)

real	0m0.368s
user	0m0.071s
sys	0m0.172s
$
$ while true; do echo -n $(date) '- ' ; ./portping lvslb-vips.csv; echo; sleep 10; done
Sun Jan 7 14:42:33 -07 2018 - running portping...
  10.12.15.121:8080,    xxxxx,    zzzzzz,    not able to connect
    10.12.15.4:8080,    aaaaa,    bbbbbb,    not able to connect
   10.12.15.35:8080,    ddddd,    eeeeee,    not able to connect
(all other VIPs are good)

Sun Jan 7 14:42:39 -07 2018 - running portping...
  10.12.15.121:8080,    xxxxx,    zzzzzz,    not able to connect
    10.12.15.4:8080,    aaaaa,    bbbbbb,    not able to connect
   10.12.15.35:8080,    ddddd,    eeeeee,    not able to connect
(all other VIPs are good)

^C
$