better-https-proxy-agent

better-https-proxy-agent
========================

An agent for HTTPS through an HTTP(S) proxy server using the CONNECT method.

This is similar to https-proxy-agent
but it leverages functionality available in the NodeJS http.Agent,
https.Agent, http.request
and/or https.request
to provide:

* connection pooling
* timeout
* TLS session resumption
* authentication (basic or client certificate)
* TLS options
* potentially anything else the NodeJS modules support

All of the above apply both to connections _to_ the proxy, as well as
connections _through_ the proxy.

It was partly inspired by this
blog post
and related gist.

Basic usage
-----------

``
npm install better-https-proxy-agent
`

`javascript
const { Agent } = require('better-https-proxy-agent');
const fs = require('fs');
const https = require('https');

/*
* Options suitable for https.Agent. These are applied to the HTTPS agent which
* manages the proxied connections between the client and the final endpoint.
*/
const httpsAgentOptions = {
keepAlive: true,
timeout: 55000,
maxSockets: 20,
maxFreeSockets: 5,
maxCachedSessions: 500
};

/*
* Options suitable for http(s).request. These are used to make the request to
* the proxy server.
*
* You should provide host here (unless you want the default localhost).
*
* protocol will default to http:. If you need to connect to the proxy over
* HTTPS, set protocol to https:. http.request or https.request will be
* used accordingly.
*
* You may include an agent here; if you do not, a default agent will be
* constructed which will be reused for connections to the proxy. If you wish
* to use the global agent, explicitly provide http(s).globalAgent.
*
* Using an agent for connection pooling will not work, because connections use
* the HTTP CONNECT method; such connection cannot be reused, and furthermore
* are removed from any agent as soon as a response is received. However, an
* additional maxSockets option is provided directly in this options object
* for the purpose of limiting the number of concurrent connections to a proxy.
*/
const proxyRequestOptions = {
protocol: "https:",
host: "proxy.example.com",
port: 3128,
timeout: 123000,
maxSockets: 100,
cert: fs.readFileSync("proxy_auth_cert.pem"),
key: fs.readFileSync("proxy_auth_key.pem"),
passphrase: "secret"
};

const agent = new Agent(httpsAgentOptions, proxyRequestOptions);

https.request("https://api.example.com", {
agent,
cert: fs.readFileSync("api_auth_cert.pem"),
key: fs.readFileSync("api_auth_key.pem"),
passphrase: "secret"
});
`

Caveats
-------

You can get yourself into a bit of trouble if you use maxSockets to limit the
connections _to_ the proxy, and also pool connections _through_ the proxy. You
can tie up all your proxy connections with connections through to a particular
host, or few hosts (say api.example.com): the connections _through_ the proxy
will be pooled and remain open, holding the corresponding connections _to_ the
proxy open also. When you go to make a new connection to a different host (say
to www.example.com) no connection _through_ the proxy can be reused, and no
new connection _to_ the proxy can be opened either. This module isn't smart
enough to close pooled connections _through_ the proxy so that you can open a
new connection _to_ the proxy.

The timeout that is set on an HTTPS request that uses the proxy agent will be
used to set the 'request timeout' (for requests _through_ the proxy), including
how long to wait for the proxy to connect to the target server, after the
connection to the proxy has already been made. The timeout in the
proxyRequestOptions (or agent provided in the proxyRequestOptions)
controls how long to wait for a connection to be made to the proxy itself.
Since it is a two-step process to connect _to_ the proxy and then connect
_through_ the proxy, these two timeouts are cumulative, which may not be what
the caller of https.request expects.

Furthermore, the timeout in the proxyRequestOptions (or agent provided in
proxyRequestOptions) applies to inactivity on the proxy connection. This can
occur during requests _through_ the proxy, or between them if keepAlive is
true in the httpsAgentOptions. More directly, the timeout for in-flight
requests _through_ the proxy is governed by any timeout option set on them,
and the timeout for kept-alive connections is governed by timeout in the
httpsAgentOptions. Consequently, timeout in proxyRequestOptions` should be
set higher than both of these other timeouts or it will gazump them, cutting
them short.

Licence
-------

MIT.