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const LRUCache = require('lru-cache')
const dns = require('dns')
const defaultOptions = exports.defaultOptions = {
family: undefined,
hints: dns.ADDRCONFIG,
all: false,
verbatim: undefined,
}
const lookupCache = exports.lookupCache = new LRUCache({ max: 50 })
// this is a factory so that each request can have its own opts (i.e. ttl)
// while still sharing the cache across all requests
exports.getLookup = (dnsOptions) => {
return (hostname, options, callback) => {
if (typeof options === 'function') {
callback = options
options = null
} else if (typeof options === 'number') {
options = { family: options }
}
options = { ...defaultOptions, ...options }
const key = JSON.stringify({
hostname,
family: options.family,
hints: options.hints,
all: options.all,
verbatim: options.verbatim,
})
if (lookupCache.has(key)) {
const [address, family] = lookupCache.get(key)
process.nextTick(callback, null, address, family)
return
}
dnsOptions.lookup(hostname, options, (err, address, family) => {
if (err) {
return callback(err)
}
lookupCache.set(key, [address, family], { ttl: dnsOptions.ttl })
return callback(null, address, family)
})
}
}
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