Go to check EC2 environment? Or DNS domain name?

user2671513 Published at Dev

user2671513

I want to see if the program is being run in EC2 or not.

One way is to run hostname -d in EC2 to get the DNS domain name.

How do I get this DNS domain name in Go.

I looked at the net package using http://golang.org/pkg/net/#LookupNS

But I need to pass an argument.

How do I check if it's in EC2 or not?

Thanks

fabrizioM

You can see if there is an interface with a specific name with this function:

package main

import (
    "log"
    "net"
    "strings"
)

func trace(fmt string, args ...interface{}) {
    log.Printf(fmt, args...)
}

func HasAddrWithName(name string) (bool, error) {
    ifaces, err := net.Interfaces()
    if err != nil {
        return false, err
    }
    for _, iface := range ifaces {
        addrs, err := iface.Addrs()
        if err != nil {
            trace("%s", err)
            continue
        }
        for _, addr := range addrs {
            ipaddr, _, err := net.ParseCIDR(addr.String())
            if err != nil {
                trace("%s", err)
                continue
            }
            hosts, err := net.LookupAddr(ipaddr.String())
            if err != nil {
                trace("%s", err)
                continue
            }
            for idx, h := range hosts {
                trace("%d: %s\n", idx, h)
                if strings.Contains(h, name) {
                    return true, nil
                }
            }
        }
    }
    return false, nil
}

func main() {
    hasAddr, err := HasAddrWithName(".ec2.internal")
    if err != nil {
        log.Fatal(err)
    }
    if hasAddr {
        log.Println("inside ec2")
        return
    }

    log.Println("Not inside ec2")
}

The function will try to find all the interface an resolve the ip to a dns name. if the name contains the specific string returns true.

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