perpen/pure-node-reverse-proxy.js

## pure-node-reverse-proxy.js
/*
https://node-a/pod/3 -> pod-home app
https://node-a/pod/3/wetty -> http://localhost:3031
https://node-a/pod/3/theia -> http://localhost:3032
*/

const http = require('http');
const url = require('url');
const fs = require('fs');
const path = require('path');

const PORT = 8080;
const INTERFACE = '127.0.0.1';
const USER = null;
const POD_PORT_RANGE_START = 3000
const POD_PORT_RANGE_WIDTH = 10

const HOME_PATH_RX = new RegExp('^/pod/(\\d+)/?$');

function home(req, res) {
    var matches = HOME_PATH_RX.exec(req.url);
    if (!matches) return false;

    var pod_number = parseInt(matches[1]);

    const config = {};

    res.setHeader('Content-type', 'text/html');
    const html = `
      <html>
        <head>
          <title>${config.pod_number}@node-a</title>
        </head>
        <body>
          <div>
            <h2>pod ${config.pod_number}@node-a</h2>
            Owner: ${config.user_display_name} (${config.user})<br>
            <a href="/pod/${config.pod_number}/wetty/">wetty</a> <br>
            <a href="/pod/${config.pod_number}/theia/">theia</a> <br>
          </div>
          <div>
            <h1>idea</h1>
            <h2>pod ${config.pod_number}@node-a</h2>
            Owner: ${config.user_display_name} (${config.user})<br>
            <br>
            To start <a href="/pod/${config.pod_number}/wetty/">wetty</a> enter the password for Joe:
            <input type="password" name="password"/>
          </div>
        </body>
      </html>`;

    res.end(html);
    return true;
};

const UI_PATH_RX = new RegExp('^(/pod/(\\d+))((/(wetty|theia))(/.*)?)$');

function ui(req, res) {

    console.log("Request for " + req.url);

    var proxy_params;
    {
        var matches = UI_PATH_RX.exec(req.url);
        if (!matches) return false;

        req.headers['host'] = "127.0.0.1";
        // used to rewrite response cookies from post()
        req.ui_context = matches[1] + matches[4];
        var pod_number = parseInt(matches[2]);
        var pod_port = POD_PORT_RANGE_START + POD_PORT_RANGE_WIDTH * pod_number + 1;

        proxy_params = {
            host: "127.0.0.1",
            port: pod_port,
            method: req.method,
            path: (matches[6] || '/'),
            headers: req.headers
        };
    }
    if (proxy_params == null) {
        return false;
    }
    console.log(proxy_params);

    var proxy_req = http.request(proxy_params, function(proxy_res) {
        var cooks = proxy_res.headers['set-cookie'];
        if (cooks) {
            var new_cooks = [cooks[0].replace(/^(.* Path=)(.*)$/, "$1" + req.ui_context + "$2")];
            proxy_res.headers['set-cookie'] = new_cooks;
        }
        if (proxy_res.headers.connection) {
            if (req.headers.connection) {
                proxy_res.headers.connection = req.headers.connection;
            } else {
                proxy_res.headers.connection = 'close';
            }
        }

        res.writeHead(proxy_res.statusCode, proxy_res.headers);
        // FIXME ???
        if (proxy_res.statusCode === 304) {
            res.end();
            return;
        }
        proxy_res.addListener('data', function(chunk) {
            res.write(chunk, 'binary');
        });
        proxy_res.addListener('end', function() {
            res.end();
        });
    });

    proxy_req.on('error', function(e) {
        console.log("Request for " + req.url + " failed - back-end server caused exception : " + e);
        res.writeHead(503, {
            'content-type': 'text/html'
        });
        res.end('An error was encountered talking to the back-end server.');
        return;
    });

    req.addListener('data', function(chunk) {
        proxy_req.write(chunk, 'binary');
    });
    req.addListener('end', function() {
        proxy_req.end();
    });

    return true;
}

function fileHandler(req, res) {
  console.log(`${req.method} ${req.url}`);

  const parsedUrl = url.parse(req.url);
  let pathname = `.${parsedUrl.pathname}`;

  const allowed = [
    './favicon.ico',
  ];
  if (!allowed.includes(pathname)) {
    const msg = `File not allowed: ${pathname}`;
    console.log(msg);
    res.statusCode = 401;
    res.end(msg);
    return;
  }

  const ext = path.parse(pathname).ext;
  const map = {
    '.ico': 'image/x-icon',
    '.html': 'text/html',
    '.js': 'text/javascript',
    '.json': 'application/json',
    '.css': 'text/css',
    '.png': 'image/png',
    '.jpg': 'image/jpeg'
  };

  fs.exists(pathname, function (exist) {
    if(!exist) {
      const msg = `File not found: ${pathname}`;
      console.log(msg);
      res.statusCode = 404;
      res.end(msg);
      return;
    }

    fs.readFile(pathname, function(err, data) {
      if (err){
        const msg = `Error getting the file: ${err}.`;
        console.log(msg);
        res.statusCode = 500;
        res.end(msg);
      } else {
        res.setHeader('Content-type', map[ext] || 'text/plain' );
        res.end(data);
      }
    });
  })
};

//////////////////////////////////////////////////

process.on('uncaughtException', function(err) {
    console.log("ERROR:" + err);
    console.log(err.stack);
});

const handler = function(req, res) {
    home(req, res) || ui(req, res) || fileHandler(req, res);
}

http.createServer().addListener("request", handler).listen(PORT, INTERFACE);

if (USER) {
    console.log("Switching to user " + USER);
    process.setuid(USER);
}

console.log(`Serving on ${INTERFACE}:${PORT}`);
	/*
	https://node-a/pod/3 -> pod-home app
	https://node-a/pod/3/wetty -> http://localhost:3031
	https://node-a/pod/3/theia -> http://localhost:3032
	*/

	const http = require('http');
	const url = require('url');
	const fs = require('fs');
	const path = require('path');

	const PORT = 8080;
	const INTERFACE = '127.0.0.1';
	const USER = null;
	const POD_PORT_RANGE_START = 3000
	const POD_PORT_RANGE_WIDTH = 10

	const HOME_PATH_RX = new RegExp('^/pod/(\\d+)/?$');

	function home(req, res) {
	var matches = HOME_PATH_RX.exec(req.url);
	if (!matches) return false;

	var pod_number = parseInt(matches[1]);

	const config = {};

	res.setHeader('Content-type', 'text/html');
	const html = `
	<html>
	<head>
	<title>${config.pod_number}@node-a</title>
	</head>
	<body>
	<div>
	<h2>pod ${config.pod_number}@node-a</h2>
	Owner: ${config.user_display_name} (${config.user})<br>
	<a href="/pod/${config.pod_number}/wetty/">wetty</a> <br>
	<a href="/pod/${config.pod_number}/theia/">theia</a> <br>
	</div>
	<div>
	<h1>idea</h1>
	<h2>pod ${config.pod_number}@node-a</h2>
	Owner: ${config.user_display_name} (${config.user})<br>
	<br>
	To start <a href="/pod/${config.pod_number}/wetty/">wetty</a> enter the password for Joe:
	<input type="password" name="password"/>
	</div>
	</body>
	</html>`;

	res.end(html);
	return true;
	};

	const UI_PATH_RX = new RegExp('^(/pod/(\\d+))((/(wetty\|theia))(/.*)?)$');

	function ui(req, res) {

	console.log("Request for " + req.url);

	var proxy_params;
	{
	var matches = UI_PATH_RX.exec(req.url);
	if (!matches) return false;

	req.headers['host'] = "127.0.0.1";
	// used to rewrite response cookies from post()
	req.ui_context = matches[1] + matches[4];
	var pod_number = parseInt(matches[2]);
	var pod_port = POD_PORT_RANGE_START + POD_PORT_RANGE_WIDTH * pod_number + 1;

	proxy_params = {
	host: "127.0.0.1",
	port: pod_port,
	method: req.method,
	path: (matches[6] \|\| '/'),
	headers: req.headers
	};
	}
	if (proxy_params == null) {
	return false;
	}
	console.log(proxy_params);

	var proxy_req = http.request(proxy_params, function(proxy_res) {
	var cooks = proxy_res.headers['set-cookie'];
	if (cooks) {
	var new_cooks = [cooks[0].replace(/^(.* Path=)(.*)$/, "$1" + req.ui_context + "$2")];
	proxy_res.headers['set-cookie'] = new_cooks;
	}
	if (proxy_res.headers.connection) {
	if (req.headers.connection) {
	proxy_res.headers.connection = req.headers.connection;
	} else {
	proxy_res.headers.connection = 'close';
	}
	}

	res.writeHead(proxy_res.statusCode, proxy_res.headers);
	// FIXME ???
	if (proxy_res.statusCode === 304) {
	res.end();
	return;
	}
	proxy_res.addListener('data', function(chunk) {
	res.write(chunk, 'binary');
	});
	proxy_res.addListener('end', function() {
	res.end();
	});
	});

	proxy_req.on('error', function(e) {
	console.log("Request for " + req.url + " failed - back-end server caused exception : " + e);
	res.writeHead(503, {
	'content-type': 'text/html'
	});
	res.end('An error was encountered talking to the back-end server.');
	return;
	});

	req.addListener('data', function(chunk) {
	proxy_req.write(chunk, 'binary');
	});
	req.addListener('end', function() {
	proxy_req.end();
	});

	return true;
	}

	function fileHandler(req, res) {
	console.log(`${req.method} ${req.url}`);

	const parsedUrl = url.parse(req.url);
	let pathname = `.${parsedUrl.pathname}`;

	const allowed = [
	'./favicon.ico',
	];
	if (!allowed.includes(pathname)) {
	const msg = `File not allowed: ${pathname}`;
	console.log(msg);
	res.statusCode = 401;
	res.end(msg);
	return;
	}

	const ext = path.parse(pathname).ext;
	const map = {
	'.ico': 'image/x-icon',
	'.html': 'text/html',
	'.js': 'text/javascript',
	'.json': 'application/json',
	'.css': 'text/css',
	'.png': 'image/png',
	'.jpg': 'image/jpeg'
	};

	fs.exists(pathname, function (exist) {
	if(!exist) {
	const msg = `File not found: ${pathname}`;
	console.log(msg);
	res.statusCode = 404;
	res.end(msg);
	return;
	}

	fs.readFile(pathname, function(err, data) {
	if (err){
	const msg = `Error getting the file: ${err}.`;
	console.log(msg);
	res.statusCode = 500;
	res.end(msg);
	} else {
	res.setHeader('Content-type', map[ext] \|\| 'text/plain' );
	res.end(data);
	}
	});
	})
	};

	//////////////////////////////////////////////////

	process.on('uncaughtException', function(err) {
	console.log("ERROR:" + err);
	console.log(err.stack);
	});

	const handler = function(req, res) {
	home(req, res) \|\| ui(req, res) \|\| fileHandler(req, res);
	}

	http.createServer().addListener("request", handler).listen(PORT, INTERFACE);

	if (USER) {
	console.log("Switching to user " + USER);
	process.setuid(USER);
	}

	console.log(`Serving on ${INTERFACE}:${PORT}`);