resolvermt

README

Resolver MT

This package provides a multithreaded and thread-safe DNS resolver client for Go. It is used to quickly resolve DNS queries in applications that need to perform requests concurrently, while also respecting a limit of queries per second for each resolver.

Create a new resolver client and set the resolvers to use, the limit of queries per second and the total number of goroutines to create. When done, close the connections by calling Client.Close().

package resolvermt_test

import (
	"fmt"

	"github.com/d3mondev/resolvermt"
)

func main() {
	resolvers := []string{
		"8.8.8.8",
		"9.9.9.10",
		"1.1.1.1",
	}

	domains := []string{
		"www.google.com",
		"facebook.com",
		"uber.com",
		"apple.com",
		"blogger.com",
		"instagram.com",
		"linkedin.com",
		"en.wikipedia.org",
		"cloudflare.com",
		"wordpress.org",
	}

	client := resolvermt.New(resolvers, 3, 10, 5)
	defer client.Close()

	results := client.Resolve(domains, resolvermt.TypeA)

	for _, record := range results {
		fmt.Printf("%s %s %s\n", record.Question, record.Type, record.Answer)
	}
}

Output:

www.google.com A 172.217.13.164
uber.com A 104.36.195.150
facebook.com A 31.13.67.35
apple.com A 17.253.144.10
instagram.com A 34.226.174.41
instagram.com A 54.86.160.135
instagram.com A 54.210.252.14
instagram.com A 52.87.69.127
instagram.com A 54.205.161.210
instagram.com A 54.174.36.241
instagram.com A 54.165.128.247
instagram.com A 3.208.131.236
blogger.com A 172.217.165.41
cloudflare.com A 104.16.132.229
cloudflare.com A 104.16.133.229
linkedin.com A 13.107.42.14
en.wikipedia.org CNAME dyna.wikimedia.org
en.wikipedia.org A 208.80.154.224
wordpress.org A 198.143.164.252

In its current implementation, the client will create at least one or more sockets per resolver to send and receive DNS queries. As each socket uses an open file descriptor, it is easy to hit the limit of open file descriptors in the OS. If this happens, the client will handle the failed connections but the performance may suffer with a large number of resolvers and threads. If you are trying to run a large number of requests concurrently (100+), increase the limit with ulimit -n 102400. A future version may change the way queries are made to prevent this.

Documentation

Overview

Example

package main

import (
	"fmt"

	"github.com/d3mondev/resolvermt"
)

func main() {
	resolvers := []string{
		"8.8.8.8",
		"9.9.9.10",
		"1.1.1.1",
	}

	domains := []string{
		"www.google.com",
		"facebook.com",
		"uber.com",
		"apple.com",
		"blogger.com",
		"instagram.com",
		"linkedin.com",
		"en.wikipedia.org",
		"cloudflare.com",
		"wordpress.org",
	}

	client := resolvermt.New(resolvers, 3, 10, 5)
	defer client.Close()

	results := client.Resolve(domains, resolvermt.TypeA)

	for _, record := range results {
		fmt.Printf("%s %s %s\n", record.Question, record.Type, record.Answer)
	}
}

Index

• type Client
  • func New(resolvers []string, retryCount int, queriesPerSecond int, maxConcurrency int) Client
• type RRtype
  • func (t RRtype) String() string
• type Record

Examples

• Package

Types

type Client

type Client interface {
	Resolve(domains []string, rrtype RRtype) []Record
	QueryCount() int
	Close()
}

Client is used to send DNS requests to resolvers concurrently.

func New

func New(resolvers []string, retryCount int, queriesPerSecond int, maxConcurrency int) Client

New returns a Client that will respect the retry count, queries per seconds and a maximum number of concurrent queries that can happen at the same time. It is important to call Close on the client when done in order to free the UDP connections it creates.

type RRtype

type RRtype uint16

RRtype resource record type.

const (
	// TypeA A record
	TypeA RRtype = RRtype(dns.TypeA)

	// TypeAAAA AAAA record
	TypeAAAA RRtype = RRtype(dns.TypeAAAA)

	// TypeCNAME CNAME record
	TypeCNAME RRtype = RRtype(dns.TypeCNAME)

	// TypeTXT TXT record
	TypeTXT RRtype = RRtype(dns.TypeTXT)

	// TypeMX MX record
	TypeMX RRtype = RRtype(dns.TypeMX)

	// TypeNS NS record
	TypeNS RRtype = RRtype(dns.TypeNS)
)

func (RRtype) String

func (t RRtype) String() string

type Record

type Record struct {
	Question string
	Type     RRtype
	Answer   string
}

Record contains a DNS record entry returned by Client.Resolve.