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node_modules/make-fetch-happen/lib/dns.js

@@ -0,0 +1,49 @@
+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)
+    })
+  }
+}