How to set up an apache proxy for Meteor/SockJS and WebSocket?
apache, meteor, proxy, sockjs, websocket
Solution
We use this for Apache and a SockJS app behind Apache. Apache is doing WebSocket proxy automatically, but you have to rewrite the scheme to ws otherwise it fallbacks to XHR. But only if the connection is a WebSocket handshake. Adding the following will fix your problem :) (note: change the `localhost:3000` accordingly to your own backend url.
RewriteEngine on
RewriteCond %{HTTP:UPGRADE} ^websocket$ [NC]
RewriteCond %{HTTP:CONNECTION} Upgrade [NC]
RewriteRule .* ws://localhost:3000%{REQUEST_URI} [P]
Problem
I have an apache proxy for a meteor app and apache and meteor are on two separate machines. I need it that way as apache has to serve a lot of real websites and it wouldn't be a good idea to install the meteor app on this machine due to its limited resources. However the WebSocket handshake fails with response code 400 "Can upgrade only to websocket" if I try to connect from the outside via the proxy. Everything works fine when I connect from within the LAN directly to the meteor machine. When WebSocket fails SockJS/Meteor falls back to XHR but unfortunately this brings up some bugs in the app in question. So I really need WebSocket to work in most of the cases. I patched my apache installation with the patch mentioned here: https://stackoverflow.com/a/16998664 That looked like it went well but nothing changed... My apache proxy directives currently are as follows: ``` ProxyRequests Off ProxyPreserveHost On ModPagespeed Off <proxy> Order deny,allow Allow from all </proxy> ProxyPass / http://10.0.2.6:3000/ ProxyPassReverse / http://10.0.2.6:3000/ ``` And I even know what's triggering the problem. The apache proxy messes around with the header. The original request header of the packet in question leaving my machine looks like this: ``` GET /sockjs/430/minw4r_o/websocket HTTP/1.1 Upgrade: websocket Connection: Upgrade Host: example.com Origin: http://example.com Pragma: no-cache Cache-Control: no-cache Sec-WebSocket-Key: myKey Sec-WebSocket-Version: 13 Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits, x-webkit-deflate-frame User-Agent: My Agent ``` While the packet gets forwarded from the apache proxy like this: ``` GET /sockjs/430/minw4r_o/websocket HTTP/1.1 Host: example.com Origin: http://example.com Pragma: no-cache Cache-Control: no-cache Sec-WebSocket-Key: myKey Sec-WebSocket-Version: 13 Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits, x-webkit-deflate-frame User-Agent: My Agent X-Forwarded-For: 24.xxx.xxx.xxx X-Forwarded-Host: example.com X-Forwarded-Server: example.com Connection: Keep-Alive ``` So "Upgrade" gets removed and "Connection" altered and so the websocket handshake fails. Now I could try to always set "Upgrade" to "websocket" with a RequestHeader directive. However this doesn't feel right and I guess it would bring up other problems and so I was wondering if there is a real solution to this problem? Or is this something the patch from https://stackoverflow.com/a/16998664 should address and something went wrong on my end applying it? From what I have read switching to nginx could make this setup easier. I will consider this but when possible I'd like to do this with apache as nginx would make other things more complicated and cost me a lot of time.