go-netutil

netutil.RRDialer has the same interface of net.Dial. With this package, You can request to a specific IP address with priority as you like.

In golang, net.LookupIP returns IP addresses after sortBy6724, that is defined in src/net/addrselect.go. Because of this, address for net.Dial might connect to a fixed ip address in some case. For example, source IP and destination IP are in the same local area network like "10.0.0.0/16" or "192.168.0.0/24". In my case, in a AWS VPC network, http.Client always connect to a specific IP address of ELB from an EC2 instance. This will ruin the effects of DNS round robin.

You can change the priority of each address with this package.

netutil.DefaultRRDialer sort a list of address by random priority.

Installation

go get github.com/ReSTARTR/go-netutil

Usage

netutil.RRDialer

netutil.DefaultRRDialer uses netutil.DefaultSort for sorting IP addresses. netutil.DefaultSort sorts IPs randomly.

import (
	"net/http"
	"github.com/ReSTARTR/go-netutil"
)

func main() {
	req, _ := http.NewRequest("GET",  "https://example.com/foo/bar", nil)
	client := http.Client{
		Transport: &http.Transport {
			Dial: netutil.DefaultRRDialer.Dial,
		},
	}
	res, _ := client.Do(req)
	_ = res
}

You can set a specific netutil.RRDialer.Sort function.

dialer := netutil.Dialer{
	Sort: func(ips []net.IP) ([]net.IP) {
		sort.Sort(ByFoo(ips))
		return ips
	},
}
client := http.Client{
	Transport: &http.Transport {
		Dial: dialer.Dial,
	},
}
client.Do(req)

Contribution

• Fork (https://github.com/ReSTARTR/go-netutil/fork)
• Create a feature branch
• Commit your changes
• Rebase your local changes against the master branch
• Run test suite with the make test command and confirm that it passes
• Create a new Pull Request

Author

ReSTARTR