async-keepalive

electrode-keepalive

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

Usage

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.

APIs

Properties

agent

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

https

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

static DNS_CACHE

ElectrodeKeepAlive.DNS_CACHE - Internal DNS mapping object.

Methods

constructor

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.

preLookup

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.

clearDnsCache

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

getName

instance.getName(options)

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

Changelog

[0.2.1]

Fixed

• Initialization without opts.expiry passed causes TypeError.