Hi,
I am trying to write a proxy server in nodejs using node-http-proxy module by
nodejitsu. Since I am new to nodejs so I have tried to use the
modifyResponse-middleware.js example from [1] as a starting point.
var fs = require('fs'),
util = require('util'),
colors = require('colors'),
http = require('http'),
connect = require('connect'),
httpProxy = require('http-proxy'),
request = require('request'),
Promise = require('es6-promise').Promise,
crypto = require('crypto');
function get_sha1(data) {
var shasum = crypto.createHash('sha1');
shasum.update(data);
return shasum.digest('hex');
}
function process_data(url, data) {
// Asynchronously process data and write final data to a file on filesystem
at 'data/test-out' + tag + '.html'
// It returns back a promise that can perform operations with final data
when it is made available.
// ...
}
//
// Basic Connect App
//
connect.createServer(
function (req, res, next) {
var _write = res.write, _writeHead = res.writeHead, url = '';
url = req.url + '-at-'+ req.client._httpMessage.connection._idleStart;
tag = get_sha1(url);
res.writeHead = function (statusCode, reason, headers) {
res.removeHeader('Content-Length');
if (headers) {
delete headers['content-length'];
}
_writeHead.apply(res, arguments);
};
res.write = function (data) {
var promise = process_data(url, data);
promise.then(function (result) {
console.log(result);
// Read ndata from file created by async promise fulfillment
ndata = fs.readFileSync('data/test-out' + tag + '.html');
_write.call(res, ndata);
}, function (err) {
console.log(err);
_write.call(res, data);
});
};
next();
},
function (req, res) {
proxy.web(req, res);
}
).listen(8013);
//
// Http Proxy Server
//
var proxy = httpProxy.createProxyServer({
target: 'https://www.google.com'
});
proxy.on('error', function (e) {
util.puts('Error occured while serving request'.red);
console.log(e);
});
util.puts('Proxy Server'.blue + ' started '.green.bold + 'on port '.blue +
'8013'.yellow);
In the example as highlighted I have a function call to process_data that
returns a promise. This promise asynchronously make available the new data from
the data got from proxied server upon fulfilment. But the problem that I am
facing is that before the promise is fulfilled or failed the response write
method completes and the client receives an empty response.
Kindly let me know how I can make this async processing work here in context of
the nodejs connect based server.
Thanks.
Ashish Sharma
--
[1]:
https://github.com/nodejitsu/node-http-proxy/blob/master/examples/middleware/modifyResponse-middleware.js
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