agent-base

What is agent-base?

The agent-base package is a module for Node.js that allows you to create custom HTTP/HTTPS Agents. It is used to implement custom proxying behavior, connection pooling, and other HTTP client enhancements. It provides a simple way to extend the core `http.Agent` class to customize the behavior of HTTP requests.

What are agent-base's main functionalities?

Custom HTTP Agent

This feature allows you to create a custom HTTP agent by providing a function that handles HTTP requests. The function can perform custom logic and must return a stream, socket, or an existing agent.

const agent = require('agent-base');

function myAgent(request, options) {
  // Custom logic for handling HTTP requests
  return new Promise((resolve, reject) => {
    // Resolve with a custom stream, socket, or an existing agent
    resolve(myCustomStreamOrSocket);
  });
}

module.exports = agent(myAgent);

HTTPS Agent with Custom Certificate

This feature demonstrates how to create an HTTPS agent with a custom certificate. The agent is created by extending the `https.Agent` class and adding custom options, such as SSL key and certificate.

const agent = require('agent-base');
const https = require('https');
const fs = require('fs');

const options = {
  key: fs.readFileSync('key.pem'),
  cert: fs.readFileSync('cert.pem')
};

const httpsAgent = agent((req, opts) => {
  return new Promise((resolve, reject) => {
    opts = Object.assign({}, opts, options);
    resolve(new https.Agent(opts));
  });
});

module.exports = httpsAgent;

Other packages similar to agent-base

http-proxy-agent

The http-proxy-agent package provides an HTTP Agent implementation that connects to a specified HTTP proxy server. It is similar to agent-base in that it allows you to customize the behavior of HTTP requests, but it is specifically designed for proxying.

https-proxy-agent

Similar to http-proxy-agent, https-proxy-agent is an HTTPS Agent implementation for proxying HTTPS requests. It provides similar functionality to agent-base but is tailored for HTTPS connections through a proxy server.

socks-proxy-agent

The socks-proxy-agent package is an HTTP Agent that connects to a SOCKS proxy server. It is another example of a package that extends the functionality of the core HTTP Agent, similar to agent-base, but with a focus on SOCKS proxy support.

README

agent-base

Turn a function into an http.Agent instance

This module is a thin wrapper around the base http.Agent class.

It provides an abstract class that must define a connect() function, which is responsible for creating the underlying socket that the HTTP client requests will use.

The connect() function may return an arbitrary Duplex stream, or another http.Agent instance to delegate the request to, and may be asynchronous (by defining an async function).

Instances of this agent can be used with the http and https modules. To differentiate, the options parameter in the connect() function includes a secureEndpoint property, which can be checked to determine what type of socket should be returned.

Some subclasses:

Here are 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 proxy http.Agent implementation for HTTP and HTTPS

Example

Here's a minimal example that creates a new net.Socket or tls.Socket based on the secureEndpoint property. This agent can be used with both the http and https modules.

import * as net from 'net';
import * as tls from 'tls';
import * as http from 'http';
import { Agent } from 'agent-base';

class MyAgent extends Agent {
  connect(req, opts) {
    // `secureEndpoint` is true when using the "https" module
    if (opts.secureEndpoint) {
      return tls.connect(opts);
    } else {
      return net.connect(opts);
    }
  }
});

// Keep alive enabled means that `connect()` will only be
// invoked when a new connection needs to be created
const agent = new MyAgent({ keepAlive: true });

// Pass the `agent` option when creating the HTTP request
http.get('http://nodejs.org/api/', { agent }, (res) => {
  console.log('"response" event!', res.headers);
  res.pipe(process.stdout);
});