A cacheable dns.lookup(…) that respects the TTL. 

A cacheable dns.lookup(…) that respects TTL

sindresorhus

szmarczak

cacheable-lookup

A cacheable dns.lookup(…) that respects the TTL

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  "description": "A cacheable dns.lookup(…) that respects the TTL",

    "test": "xo && nyc --reporter=lcovonly --reporter=text ava && tsd"

    "url": "git+https://github.com/szmarczak/cacheable-lookup.git"

    "url": "https://github.com/szmarczak/cacheable-lookup/issues"

  "homepage": "https://github.com/szmarczak/cacheable-lookup#readme",

> A cacheable [`dns.lookup(…)`](https://nodejs.org/api/dns.html#dns_dns_lookup_hostname_options_callback) that respects TTL :tada:

[![Node CI](https://github.com/szmarczak/cacheable-lookup/workflows/Node%20CI/badge.svg)](https://github.com/szmarczak/cacheable-lookup/actions)

[![Coverage Status](https://coveralls.io/repos/github/szmarczak/cacheable-lookup/badge.svg?branch=master)](https://coveralls.io/github/szmarczak/cacheable-lookup?branch=master)

[![npm](https://img.shields.io/npm/dm/cacheable-lookup.svg)](https://www.npmjs.com/package/cacheable-lookup)

[![install size](https://packagephobia.now.sh/badge?p=cacheable-lookup)](https://packagephobia.now.sh/result?p=cacheable-lookup)

Making lots of HTTP requests? You can save some time by caching DNS lookups :zap:

const CacheableLookup = require('cacheable-lookup');

http.get('https://example.com', {lookup: cacheable.lookup}, response => {

### Attaching CacheableLookup to an Agent

http.get('https://example.com', response => {

Returns a new instance of `CacheableLookup`.

Type: `Map` | [`Keyv`](https://github.com/lukechilds/keyv/)

Custom cache instance. If `undefined`, it will create a new one.

**Note**: If you decide to use Keyv instead of the native implementation, the performance will drop by 10x. Memory leaks may occur as it doesn't provide any way to remove all the deprecated values at once.

The maximum lifetime of the entries received from the specifed DNS server (TTL in seconds).

If set to `0`, it will make a new DNS query each time.

**Pro Tip**: This shouldn't be lower than your DNS server response time in order to prevent bottlenecks. For example, if you use Cloudflare, this value should be greater than `0.01`.

The lifetime of the entries received from the OS (TTL in seconds).

**Note**: This option is independent, `options.maxTtl` does not affect this.

The time how long it needs to remember failed queries (TTL in seconds).

The time how long it needs to remember queries that threw `ENOTFOUND` (TTL in seconds).

Type: `dns.Resolver | dns.promises.Resolver`

Default: [`new dns.promises.Resolver()`](https://nodejs.org/api/dns.html#dns_class_dns_resolver)

An instance of [DNS Resolver](https://nodejs.org/api/dns.html#dns_class_dns_resolver) used to make DNS queries.

The full path to the `hosts` file. Set this to `false` to prevent loading entries from the `hosts` file.

The IP address (can be an IPv4 or IPv6 address).

**Note**: This is not present when using the native `dns.lookup(...)`!

The timestamp (`Date.now() + ttl * 1000`) when the entry expires.

When `options.all` is `false`, then `callback(error, address, family, expires, ttl)` is called.

When `options.all` is `true`, then `callback(error, entries)` is called.

The DNS servers used to make queries. Can be overridden - doing so will trigger `cacheableLookup.updateInterfaceInfo()`.

#### [lookup(hostname, options, callback)](https://nodejs.org/api/dns.html#dns_dns_lookup_hostname_options_callback)

The asynchronous version of `dns.lookup(…)`.

Returns an [entry object](#entry-object).

If `options.all` is true, returns an array of entry objects.

**Note**: If entry(ies) were not found, it will return `undefined` by default.

The same as the [`dns.lookup(…)`](https://nodejs.org/api/dns.html#dns_dns_lookup_hostname_options_callback) options.

An asynchronous function which returns cached DNS lookup entries.

This is the base for `lookupAsync(hostname, options)` and `lookup(hostname, options, callback)`.

Returns an array of objects with `address`, `family`, `ttl` and `expires` properties.

An asynchronous function which makes two DNS queries: A and AAAA. The result is cached.

This is used by `query(hostname)` if no entry in the database is present.

const {readFile} = require('fs').promises;

const {readFile, stat} = require('fs').promises;

const isWindows = process.platform === 'win32';

const hostsPath = isWindows ? `${process.env.SystemDrive}\\Windows\\System32\\drivers\\etc\\hosts` : '/etc/hosts';

const hostnameRegExp = /^(?:(?:[a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9-]*[a-zA-Z0-9])\.)*(?:[A-Za-z0-9]|[A-Za-z0-9][A-Za-z0-9-]*[A-Za-z0-9])$/;

const isHostname = hostname => hostnameRegExp.test(hostname);

const whitespaceRegExp = /[^\S\r\n]{2,}/g;

const startsWithWhitespaceRegExp = /^[^\S\r\n]+/gm;

// TODO: Remove this when https://github.com/nodejs/node/issues/33096 gets fixed

const watchFile = (path, callback, onError) => {

	const interval = setInterval(async () => {

			if (previousTime !== null && mtimeMs !== previousTime) {

	constructor(customHostsPath = hostsPath) {

			if (typeof this._hostsPath !== 'string') {

			watchFile(this._hostsPath, (currentTime, previousTime) => {

			let lines = await readFile(this._hostsPath, fileOptions);

			lines = lines.replace(whitespaceRegExp, ' ');

			lines = lines.replace(tabRegExp, ' ');

			lines = lines.replace(startsWithWhitespaceRegExp, '');

						for (const entry of this._hosts[hostname]) {

						this._hosts[hostname].expires = Infinity;

		{
		"name": "cacheable-lookup",
		"version": "4.2.0",
		"version": "4.2.1",
		"description": "A cacheable dns.lookup(…) that respects the TTL",
		@@ -5,0 +5,0 @@ "engines": {

		'use strict';
		const {watchFile} = require('fs');
		const {readFile} = require('fs').promises;
		const {readFile, stat} = require('fs').promises;
		const {isIP} = require('net');
		@@ -20,2 +19,23 @@

		// TODO: Remove this when https://github.com/nodejs/node/issues/33096 gets fixed
		const watchFile = (path, callback, onError) => {
		let previousTime = null;

		const interval = setInterval(async () => {
		try {
		const {mtimeMs} = await stat(path);

		if (previousTime !== null && mtimeMs !== previousTime) {
		callback(mtimeMs, previousTime);
		}

		previousTime = mtimeMs;
		} catch (error) {
		clearInterval(interval);

		onError(error);
		}
		}, 1000 * 60).unref();
		};

		class HostsResolver {
		@@ -42,2 +62,4 @@ constructor(customHostsPath = hostsPath) {
		}
		}, error => {
		this._error = error;
		});
		@@ -44,0 +66,0 @@

		@@ -89,3 +89,3 @@ # cacheable-lookup

		The time how long it needs to remember failed queries (TTL in seconds).
		The time how long it needs to remember queries that threw `ENOTFOUND` (TTL in seconds).

		@@ -92,0 +92,0 @@ Note: This option is independent, `options.maxTtl` does not affect this.

Improved metrics