SIBS2024/node_modules/cacheable-lookup

cacheable-lookup

A cacheable dns.lookup(…) that respects TTL :tada:

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

Usage

Using the lookup option

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

const cacheable = new CacheableLookup();

http.get('http://example.com', {lookup: cacheable.lookup}, response => {
	// Handle the response here
});

Attaching CacheableLookup to an Agent

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

const cacheable = new CacheableLookup();
cacheable.install(http.globalAgent);

http.get('http://example.com', response => {
	// Handle the response here
});

API

new CacheableLookup(options)

Returns a new instance of CacheableLookup.

options

Type: object
Default: {}

Options used to cache the DNS lookups.

cache

Type: Map | Keyv
Default: new Map()

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.

Tip: QuickLRU is fully compatible with the Map API, you can use it to limit the amount of cached entries. Example:

const http = require('http');
const CacheableLookup = require('cacheable-lookup');
const QuickLRU = require('quick-lru');

const cacheable = new CacheableLookup({
	cache: new QuickLRU({maxSize: 1000})
});

http.get('http://example.com', {lookup: cacheable.lookup}, response => {
	// Handle the response here
});

options.maxTtl

Type: number
Default: Infinity

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.

options.fallbackDuration

Type: number
Default: 3600 (1 hour)

When the DNS server responds with ENOTFOUND or ENODATA and the OS reports that the entry is available, it will use dns.lookup(...) directly for the requested hostnames for the specified amount of time (in seconds).

If you don’t query internal hostnames (such as localhost, database.local etc.), it is strongly recommended to set this value to 0.

options.errorTtl

Type: number
Default: 0.15

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

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

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.

options.resolver

Type: dns.Resolver | dns.promises.Resolver
Default: new dns.promises.Resolver()

An instance of DNS Resolver used to make DNS queries.

options.lookup

Type: Function
Default: dns.lookup

The fallback function to use when the DNS server responds with ENOTFOUND or ENODATA.

Note: This has no effect if the fallbackDuration option is less than 1.

Entry object

Type: object

address

Type: string

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

family

Type: number

The IP family (4 or 6).

expires

Type: number

Note: This is not present when falling back to dns.lookup(...)!

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

ttl

Note: This is not present when falling back to dns.lookup(...)!

The time in seconds for its lifetime.

Entry object (callback-style)

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.

CacheableLookup instance

servers

Type: Array

The DNS servers used to make queries. Can be overridden - doing so will clear the cache.

lookup(hostname, options, callback)

lookupAsync(hostname, options)

The asynchronous version of dns.lookup(…).

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

hostname

Type: string

options

Type: object

The same as the dns.lookup(…) options.

query(hostname)

An asynchronous function which returns cached DNS lookup entries.
This is the base for lookupAsync(hostname, options) and lookup(hostname, options, callback).

Note: This function has no options.

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

queryAndCache(hostname)

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.

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

updateInterfaceInfo()

Updates interface info. For example, you need to run this when you plug or unplug your WiFi driver.

Note: Running updateInterfaceInfo() will trigger clear() only on network interface removal.

clear(hostname?)

Clears the cache for the given hostname. If the hostname argument is not present, the entire cache will be emptied.

High performance

Performed on:

• Query: example.com
• CPU: i7-7700k
• CPU governor: performance

CacheableLookup#lookupAsync                x 2,896,251 ops/sec ±1.07% (85 runs sampled)
CacheableLookup#lookupAsync.all            x 2,842,664 ops/sec ±1.11% (88 runs sampled)
CacheableLookup#lookupAsync.all.ADDRCONFIG x 2,598,283 ops/sec ±1.21% (88 runs sampled)
CacheableLookup#lookup                     x 2,565,913 ops/sec ±1.56% (85 runs sampled)
CacheableLookup#lookup.all                 x 2,609,039 ops/sec ±1.01% (86 runs sampled)
CacheableLookup#lookup.all.ADDRCONFIG      x 2,416,242 ops/sec ±0.89% (85 runs sampled)
dns#lookup                                 x 7,272     ops/sec ±0.36% (86 runs sampled)
dns#lookup.all                             x 7,249     ops/sec ±0.40% (86 runs sampled)
dns#lookup.all.ADDRCONFIG                  x 5,693     ops/sec ±0.28% (85 runs sampled)
Fastest is CacheableLookup#lookupAsync.all

Related

• cacheable-request - Wrap native HTTP requests with RFC compliant cache support

License

MIT