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'use strict'
const { LRUCache } = require('lru-cache')
const dns = require('dns')
// this is a factory so that each request can have its own opts (i.e. ttl)
// while still sharing the cache across all requests
const cache = new LRUCache({ max: 50 })
const getOptions = ({
family = 0,
hints = dns.ADDRCONFIG,
all = false,
verbatim = undefined,
ttl = 5 * 60 * 1000,
lookup = dns.lookup,
}) => ({
// hints and lookup are returned since both are top level properties to (net|tls).connect
hints,
lookup: (hostname, ...args) => {
const callback = args.pop() // callback is always last arg
const lookupOptions = args[0] ?? {}
const options = {
family,
hints,
all,
verbatim,
...(typeof lookupOptions === 'number' ? { family: lookupOptions } : lookupOptions),
}
const key = JSON.stringify({ hostname, ...options })
if (cache.has(key)) {
const cached = cache.get(key)
return process.nextTick(callback, null, ...cached)
}
lookup(hostname, options, (err, ...result) => {
if (err) {
return callback(err)
}
cache.set(key, result, { ttl })
return callback(null, ...result)
})
},
})
module.exports = {
cache,
getOptions,
}
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