Prevent headers from being sent twice

Created by: samalba

In some cases, when there is an error, the headers are sent twice which throws an exception. I was able to reproduce by doing this:

$ nc localhost 1080 << EOF
> GET / HTTP/1.1
> Host: foobar
>
> EOF

`foobar' is a valid proxied website. A proxy using node-http-proxy is running on localhost:1080.

This produces the following error:

http.js:708
    throw new Error('Can\'t set headers after they are sent.');
          ^
Error: Can't set headers after they are sent.
    at ServerResponse.OutgoingMessage.setHeader (http.js:708:11)
    at /Users/shad/Dropbox/work/hipache/node_modules/http-proxy/lib/node-http-proxy/http-proxy.js:332:13
    at Array.forEach (native)
    at ClientRequest.<anonymous> (/Users/shad/Dropbox/work/hipache/node_modules/http-proxy/lib/node-http-proxy/http-proxy.js:328:35)
    at ClientRequest.g (events.js:175:14)
    at ClientRequest.EventEmitter.emit (events.js:95:17)
    at HTTPParser.parserOnIncomingClient [as onIncoming] (http.js:1630:21)
    at HTTPParser.parserOnHeadersComplete [as onHeadersComplete] (http.js:119:23)
    at Socket.socketOnData [as ondata] (http.js:1528:20)
    at TCP.onread (net.js:495:27)

The problem here is that netcat does not read anything. I tried with a script that reads the response and the error does not occur. The simple `if' statement I added prevents the bug to happen and everything then works normally.

Created by: indexzero

@samalba Could you add a test case for this?

Created by: samalba

I could yes, however I tried to run the tests and they're hanging on my machine: http://pastie.org/private/syspc2w6h0yl98u1kivnw

Did a miss a step? I tested this fix by running hipache's test (https://github.com/dotcloud/hipache/blob/master/test/test_parseerror.py#L95). However I'd be glad to provide one for node-http-proxy!

Created by: indexzero

What node version are you on?

Created by: indexzero

That's a good test; would love to see it in node.js. Create a net.Server instance and write a bad header line to it. Should be straight-forward.

Created by: bwaters

Please merge, I'm having this problem too.

Created by: bfx81

Me too... pleaseeeeee

Created by: indexzero

@bwaters @bfx81 We will merge when there is a test for this.

Created by: kadishmal

I'm getting the same problem.

Created by: bfx81

I've tested the patch and this didn't solve the problem... checked at a "lower" level in http.js nodejs core module. This solved my problem https://github.com/bfx81/node/commit/0149cce82838f98ea80191127a5bf84b21081cfd

Created by: bfx81

Sorry not sure anymore... this problem happens in a very chaotic way!

Created by: bslayton

What's the latest with this bug?

Did someone find a way to reproduce the bug ?

Created by: davidsteinberger

I was hit today by that nasty Error: Can't render headers after they are sent to the client. error.

It obviously is caused by setting headers after some data has already been sent. It took me a while but I found that in my case the proxyError-event handler is causing that issue: Data has already been sent, the proxyError-handler sets the header 'Content-Type' and it blows up.

For the time being I simple commented out the writeHead-call: //res.writeHead(500, { 'Content-Type': 'text/plain' });

Created by: achselschweisz

Is this issue resolved yet? Admittedly it is hard to reproduce. I encountered the

Error: Can't render headers after they are sent to the client.
    at ServerResponse.OutgoingMessage._renderHeaders (http.js:733:11)
    at ServerResponse.writeHead (http.js:1150:20)
    at ClientRequest.proxyError (/opt/napp/router/node_modules/http-proxy/lib/node-http-proxy/http-proxy.js:203:9)
    at ClientRequest.g (events.js:175:14)
    at ClientRequest.EventEmitter.emit (events.js:95:17)
    at Socket.socketErrorListener (http.js:1547:9)
    at Socket.EventEmitter.emit (events.js:95:17)
    at net.js:441:14
    at process._tickCallback (node.js:415:13)

today.

Created by: jcrugzz

@achselschweisz checkout the caronte branch. It is a complete refactor that will become node-http-proxy 1.0. Please open a new issue if you find this to be the case

Created by: samalba

Nice! @jcrugzz any ETA for this 1.0 release?

Created by: achselschweisz

cheers, I will try that and report back (btw., just had the error again). I cannot though offer any help in reproducing the problem since this happens sporadically when streaming data to services which are proxied through node-http-proxy. Just now it took a few hours, numerous requests and about 40GiB of streaming data to make this bugger reappear.

Created by: kahnvex

I am experiencing this same error, using https://github.com/drewzboto/grunt-connect-proxy to proxy to my backend API in development. Only happens on file upload. Don't know if I am being naive or if I am experiencing the same issue.

Error: Can't render headers after they are sent to the client.
    at ServerResponse.OutgoingMessage._renderHeaders (http.js:733:11)
    at ServerResponse.res._renderHeaders (/Users/kahnjw/Documents/stompdrop/frontside/node_modules/grunt-contrib-connect/node_modules/connect/lib/patch.js:69:27)
    at ServerResponse.writeHead (http.js:1150:20)
    at ServerResponse.res.writeHead (/Users/kahnjw/Documents/stompdrop/frontside/node_modules/grunt-contrib-connect/node_modules/connect/lib/patch.js:75:22)
    at ClientRequest.proxyError (/Users/kahnjw/Documents/stompdrop/frontside/node_modules/grunt-connect-proxy/node_modules/http-proxy/lib/node-http-proxy/http-proxy.js:203:9)
    at ClientRequest.g (events.js:180:16)
    at ClientRequest.EventEmitter.emit (events.js:95:17)
    at Socket.socketErrorListener (http.js:1547:9)
    at Socket.EventEmitter.emit (events.js:95:17)
    at onwriteError (_stream_writable.js:233:10)
    at onwrite (_stream_writable.js:251:5)
    at WritableState.onwrite (_stream_writable.js:97:5)
    at fireErrorCallbacks (net.js:438:13)
    at Socket._destroy (net.js:472:3)
    at Object.afterWrite (net.js:718:10)

If it seems like the same issue I'd be interested to know.

Created by: kahnvex

Nevermind, im dumb

Created by: indexzero

Despite @samalba never submitting a test for this I'm going to roll this into the last 0.10.x maintenance release because the logic is sound.

@samalba write moar tests!

Created by: indexzero

Cherry-picked. Thanks!

Created by: inian

I am still getting this error when trying to proxy http://www.amazon.de/ website. Can someone reproduce the bug for this website?

Created by: nolanlawson

FWIW, I'm seeing this error constantly as well, using http-proxy version 0.10.4, when I set up an http-proxy in front of CouchDB:

http.js:731
    throw new Error('Can\'t render headers after they are sent to the client.'
    ^
Error: Can't render headers after they are sent to the client.
    at ServerResponse.OutgoingMessage._renderHeaders (http.js:731:11)
    at ServerResponse.writeHead (http.js:1148:20)
    at ClientRequest.proxyError (/Users/nolan/workspace/pouchdb/node_modules/http-proxy/lib/node-http-proxy/http-proxy.js:213:9)
    at ClientRequest.g (events.js:180:16)
    at ClientRequest.EventEmitter.emit (events.js:95:17)
    at Socket.socketOnData (http.js:1588:9)
    at TCP.onread (net.js:527:27)

Whose responsibility is it to fix a bug like this? Node? This module? The implementor (e.g. proxy.on('error')? I'm not sure.

Created by: nolanlawson

Ah wait, I am using a super old version of this module. Please ignore the above comment.