DeuxHuitHuit/algolia-webcrawler

/**
 * DNS cache implementation
 */

'use strict';

const dns = require('dns');
const cache = new Map();
dns._lookup = dns.lookup;
dns.lookup = (domain, family, done) => {
    if (!done) {
        done = family;
        family = null;
    }

    if (cache.has(domain)) {
        const ip = cache.get(domain);
        const ipv = ip.indexOf('.') !== -1 ? 4 : 6;

        return process.nextTick(() => done(null, ip, ipv));
    }

    dns._lookup(domain, family, (err, ip, ipv) => {
        if (err) {
            return done(err);
        }
        cache.set(domain, ip);
        done(null, ip, ipv);
    });
};