How to get Vaadin Push work through Apache HTTP server?

Question

I'm trying to get Vaadin 7.1.5 Push to work on Apache Tomcat 7.0.42 + Apache HTTP server (2.2.14 with mod_proxy_wstunnel).

The Vaadin application and push with WebSocket works fine when I access Tomcat directly (ie. http://mydomain:8080/myapp). The problem arises when I try to access it by using the Apache modules mod_proxy & mod_proxy_wstunnel. What happens is that the application hangs, the loading indicator gets red and I get this error in the push request in the browser console:

HTTP Status 501 - Websocket protocol not supported
type Status report
message Websocket protocol not supported
description The server does not support the functionality needed to fulfill this request.

Apache Tomcat/7.0.42

Before Push was needed, I used mod_jk to forward requests from http://mydomain/myapp to http://mydomain:8080/myapp. Apparenly mod_jk doesn't support WebSocket so I chose to use ProxyPass directive. Here's my Apache config:

ProxyPass               /myapp/PUSH/ ws://localhost:8080/myapp/PUSH/
ProxyPassReverse        /myapp/PUSH/ ws://localhost:8080/myapp/PUSH/

ProxyPass               /myapp/VAADIN/ http://localhost:8080/myapp/VAADIN/
ProxyPassReverse        /myapp/VAADIN/ http://localhost:8080/myapp/VAADIN/
ProxyPass               /myapp http://localhost:8080/myapp
ProxyPassReverse        /myapp http://localhost:8080/myapp

I was suspecting that mod_proxy_wstunnel was to blame, but apparently it works fine when I proxy http://echo.websocket.org. I found out that the 501 error is thrown by Atmosphere, but I don't have a clue how to debug it. If I remove the ws proxy (so the push uses HTTP instead of WS), I get an instant "Session expired" error.

Does anyone know how to properly proxy push requests from Apache HTTP server to Apache Tomcat?

Answer 1

I solved this by making sure the path of ProxyPass (and ProxyPassReverse) is identical to the context of the application and creating a new NIO connector in tomcat's server.xml config:

<Connector port="8081" protocol="org.apache.coyote.http11.Http11NioProtocol"
           connectionTimeout="20000"
           redirectPort="8443"
           proxyName="mydomain"
           proxyPort="80" />

I'm quite sure there is a way to use a path that is different from the application context, but this works for me.

UPDATE: Note that this solution doesn't work with browsers that don't support websocket (eg. IE <= 9). I suspect it has something to do with the HTTP streaming as fallback method..