agent-base

Turn a function into an `http.Agent` instance

This module provides an http.Agent generator. That is, you pass it an async callback function, and it returns a new http.Agent instance that will invoke the given callback function when sending outbound HTTP requests.

Some subclasses:

Here's some more interesting uses of agent-base. Send a pull request to list yours!

http-proxy-agent: An HTTP(s) proxy http.Agent implementation for HTTP endpoints
https-proxy-agent: An HTTP(s) proxy http.Agent implementation for HTTPS endpoints
pac-proxy-agent: A PAC file proxy http.Agent implementation for HTTP and HTTPS
socks-proxy-agent: A SOCKS (v4a) proxy http.Agent implementation for HTTP and HTTPS

Installation

Install with npm:

$ npm install agent-base

Example

Here's a minimal example that creates a new net.Socket connection to the server for every HTTP request (i.e. the equivalent of agent: false option):

var net = require('net');
var tls = require('tls');
var url = require('url');
var http = require('http');
var agent = require('agent-base');

var endpoint = 'http://nodejs.org/api/';
var parsed = url.parse(endpoint);

// This is the important part!
parsed.agent = agent(function (req, opts) {
  var socket;
  // `secureEndpoint` is true when using the https module
  if (opts.secureEndpoint) {
    socket = tls.connect(opts);
  } else {
    socket = net.connect(opts);
  }
  return socket;
});

// Everything else works just like normal...
http.get(parsed, function (res) {
  console.log('"response" event!', res.headers);
  res.pipe(process.stdout);
});

Returning a Promise or using an async function is also supported:

agent(async function (req, opts) {
  await sleep(1000);
  // etc…
});

Return another http.Agent instance to “pass through” the responsibility for that HTTP request to that agent:

agent(function (req, opts) {
  return opts.secureEndpoint ? https.globalAgent : http.globalAgent;
});

API

Agent(Function callback[, Object options]) → http.Agent

Creates a base http.Agent that will execute the callback function callback for every HTTP request that it is used as the agent for. The callback function is responsible for creating a stream.Duplex instance of some kind that will be used as the underlying socket in the HTTP request.

The options object accepts the following properties:

timeout - Number - Timeout for the callback() function in milliseconds. Defaults to Infinity (optional).

The callback function should have the following signature:

callback(http.ClientRequest req, Object options, Function cb) → undefined

The ClientRequest req can be accessed to read request headers and and the path, etc. The options object contains the options passed to the http.request()/https.request() function call, and is formatted to be directly passed to net.connect()/tls.connect(), or however else you want a Socket to be created. Pass the created socket to the callback function cb once created, and the HTTP request will continue to proceed.

If the https module is used to invoke the HTTP request, then the secureEndpoint property on options will be set to true.

License

(The MIT License)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the ‘Software’), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED ‘AS IS’, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.