express-upstream
Version:
Express.js proxy middleware to pass requests to upstream server
100 lines (99 loc) • 3.55 kB
JavaScript
// express-upstream.ts
import * as http from "http";
import * as https from "https";
import { URL } from "url";
const defaultPorts = {
"http:": 80,
"https:": 443,
};
const ignoreHeaders = {
"cache-control": 1,
"content-security-policy": 1,
"cookie": 1,
"date": 1,
"host": 1,
"referer": 1,
"set-cookie": 1,
"te": 1,
"transfer-encoding": 1,
"vary": 1,
};
const defaultAgentOptions = {
// Keep sockets around in a pool to be used by other requests in the future. Default = false
keepAlive: true,
// Socket timeout in milliseconds. This will set the timeout after the socket is connected.
timeout: 10000,
};
/**
* Express.js proxy middleware to pass requests to upstream server
* @see https://github.com/kawanet/express-upstream/
* @returns RequestHandler
*/
export const upstream = (server, options) => {
if (!options)
options = {};
const { ignoreStatus, logger } = options;
const url = new URL(server);
const protoPort = defaultPorts[url.protocol];
if (!protoPort || !url.hostname) {
throw new Error("Invalid upstream: " + server);
}
const { port } = url;
let httpAgent;
let httpsAgent;
return (req, res, next) => {
const reqOpts = {};
reqOpts.method = req.method;
reqOpts.protocol = url.protocol;
reqOpts.host = url.hostname;
if (port)
reqOpts.port = port;
reqOpts.agent = (protoPort === 443) ?
(options.httpsAgent || httpsAgent || (httpsAgent = new https.Agent(defaultAgentOptions))) :
(options.httpAgent || httpAgent || (httpAgent = new http.Agent(defaultAgentOptions)));
reqOpts.path = url.pathname.replace(/\/$/, "") + req.url;
const reqURL = [url.protocol, "//" + url.host, reqOpts.path].join("");
if (logger)
logger.log(reqURL);
// copy request headers
const headers = reqOpts.headers = {};
Object.keys(req.headers).filter(key => !ignoreHeaders[key]).forEach(key => headers[key] = req.headers[key]);
headers.host = url.host;
let started = 0;
const reqUp = http.request(reqOpts, resUp => {
if (started++)
return;
// copy response headers
const { headers, statusCode } = resUp;
// fallback to the next RequestHandler when upstream response 404 Not Found
if (allowNext(statusCode)) {
if (resUp.socket?.destroy && !resUp.socket.destroyed)
resUp.socket.destroy();
return next();
}
res.status(statusCode);
Object.keys(headers).filter(key => !ignoreHeaders[key]).forEach(key => res.setHeader(key, headers[key]));
// pipe response body
resUp.pipe(res);
});
reqUp.once("error", err => {
if (logger)
logger.log(err + "");
if (started++)
return;
const statusCode = 502;
// fallback to the next RequestHandler
if (allowNext(statusCode)) {
if (reqUp.socket?.destroy && !reqUp.socket.destroyed)
reqUp.socket.destroy();
return next();
}
res.status(statusCode).end();
});
// pipe request body
req.pipe(reqUp);
function allowNext(statusCode) {
return (ignoreStatus && ignoreStatus.test(String(statusCode)) && req.method === "GET");
}
};
};