electrode-keepalive provides an HttpAgent capable of maintaining available sockets using IP address instead of hostname lookup. This allows for graceful handling of dns changes/failover when changes occur in routing configuration. This is particularly important when using keep-alive enabled connections. It resolves part of the problems in this issue

const ElectrodeKeepAlive = require("electrode-keepalive");

const opts = {
  keepAlive: true,
  keepAliveMsecs: 30000, // socket send keep alive ping every 30 secs
  maxSockets: 100,
  maxFreeSockets: 10
};

const keepAlive = new ElectrodeKeepAlive(opts);

const dnsOptions = {};

keepAlive.preLookup("www.google.com", dnsOptions, (err) => {
  request({url: "http://www.google.com", agent: keepAlive.agent});
});

Since this module works by overriding http.Agent's synchronous getName method to return the IP instead of hostname, it has to use a pre-populated DNS mapping. Before the mapping is populated, it can't use IP. To avoid that in your first request, you should always call the preLookup method first.

instance.agent - Read only instance property to access the http/https agent.

instance.https - Read only instance property. If true, then the agent is an https agent.

ElectrodeKeepAlive.DNS_CACHE - Internal DNS mapping object.

constructor(options)

Creates an instance of ElectrodeKeepAlive.

• options should be the default http agent settings that are passed through to the underlying implementation. Additionally the following options are supported:

  • https - If true, then creates an https Agent.
  • expiry - The duration (in milliseconds) that ip entries in the DNS mapping will be refreshed. Default is 5000ms.

instance.preLookup(host, options, callback)

Allows ElectrodeKeepAlive to do a DNS lookup on the host first to populate its DNS mapping.

The arguments matches Node dns module lookup.

instance.clearDnsCache() - Wipes out current DNS mapping.

instance.getName(options)

The internal method to override http agent's default getName. Not intended for public use.