dns-fast-resolver

A custom dns.lookup based on dns.Resolver with timeout and cancellation handlers. This is intendent to be used as replacement for the standard dns.lookup in cases when more than 100 connections are required. Currently, socket.connect uses dns.lookup by default which is not intended for concurrent request (see Implementation considerations). Under the hood, this function performs a DNS query on the network and the results may differ from ping and dns.lookup.

Table of contents

• Installation
• How to use
• API
• Speed test
• Testing

Installation

$ npm install dns-fast-resolver --save

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How to use

With request module

const request = require('request')
const { fastResolver } = require('dns-fast-resolver')

request({
    url: 'http://google.com',
    method: 'GET',
    lookup: fastResolver
}, (error, response, body) => {
    // ...
})

Direct usage

const { fastResolver } = require('dns-fast-resolver')

fastResolver('google.com', {}, (error, address, family) => {
    // ...
})

Resolving IPv4 addresses only, specify param {family: 4}. In that case, you will avoid spending time on useless searching for IPv6. Apply the same technique if you are looking for IPv6 addresses only.

fastResolver('google.com', {family: 4}, (error, address, family) => {
   // address === "172.217.165.14"
   // family === 4
});

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API

fastResolver(hostname[, options], callback)

Uses same definition as dns.lookup

• hostname <string> When hostname is an IP address, the callback returns the same IP value without making any attempt to resolve it.
• options <integer> | <Object>
  • family <integer> The record family. Must be 4, 6, or 0. The value 0 indicates that IPv4 and IPv6 addresses are both returned. Default: 0.
  • hints <number> One or more supported getaddrinfo flags. Multiple flags may be passed by bitwise ORing their values.
  • all <boolean> When true, the callback returns all resolved addresses in an array. Otherwise, returns a single address. Default: false.
  • verbatim <boolean> When true, the callback receives IPv4 and IPv6 addresses in the order the DNS resolver returned them. When false, IPv4 addresses are placed before IPv6 addresses. Default: currently false (addresses are reordered) but this is expected to change in the not too distant future. New code should use { verbatim: true }.
  • timeout <integer> Number of miliseconds to wait before the resolving request is canceled. Default value 4000 (4s).

  In rare cases, hostnames may need more than 4 seconds to be resolved. Use the timeout option to adjust the waiting time.

  • servers <string[]> Array of RFC 5952 formatted addresses. (Example: ['4.4.4.4', '[2001:4860:4860::8888]', '4.4.4.4:1053', '[2001:4860:4860::8888]:1053']) ]`
• callback <Function>
  • err <Error>
  • address <string> A string representation of an IPv4 or IPv6 address.
  • family <integer> 4 or 6, denoting the family of address, or 0 if the address is not an IPv4 or IPv6 address. 0 is a likely indicator of a bug in the name resolution service used by the operating system.

Resolves a host name (e.g. 'wikipedia.org') into the first found A (IPv4) or AAAA (IPv6) record. All option properties are optional. If options is an integer, then it must be 4 or 6 – if options is not provided, then IPv4 and IPv6 addresses are both returned if found.

With the all option set to true, the arguments for callback change to (err, addresses), with addresses being an array of objects with the properties address and family.

On error, err is an Error object, where err.code is the error code. Keep in mind that err.code will be set to 'ENOTFOUND' not only when the host name does not exist but also when the lookup fails in other ways such as no available file descriptors.

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Speed test

Output from speed test unit test using default settings

`dns-fast-resolver`  invalid  63, valid 937, resolved  6.3%, duration  3.96s
`dns.Resolver`       invalid 558, valid 442, resolved 55.8%, duration 10.41s
`dns.lookup`         invalid  62, valid 938, resolved  6.2%, duration 93.86s

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Testing

Run all tests

$ npm run unit-test

Run test with 1000 websites

$ npm run unit-test -- --grep "resolve \"_top_1000_sites.js\" - strict"

Run speed test test

$ npm run unit-test -- --grep "speed test"

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