Add lookup option to override dns lookups #1574
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Add `lookup` option to allow overriding default dns resolving. This can be used to add caching or other customization.
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The cause of this is that when proxying api requests to a hostname, node will perform a dns query for every single request, which adds unnecessary overhead. While I was investigating I found nodejs/node#5893 and understood that there is no built in dns caching in node and that it seemingly bypasses OS dns cache. Adding a dns cache into
http-proxywould clearly not be optimal, but by exposing thelookupoption forrequest()we can customize the dns lookup thathttp-proxyperforms and add our own cache, or inject https://www.npmjs.com/package/dns-lookup-cache or something similiar. (fixes #653)This configuration would also allow to customize the DNS lookup (fixes #1315)
One problem with this is that the
request()lookupoption is only available in node v12 and later, so using the option when running node 8/10 would not have any effect. shouldn't implode either, but does nothing.