Problem

Confluence 6.x is configured with Apache 2.4 using SSL and Websockets as described in this guide: Securing your Atlassian applications with Apache using SSL

However, when trying to use collaborative editing, you get an error in the browser and the editor does not load. 

Diagnosis

Environment

• Confluence 6 or higher
• Apache 2.4.9 or earlier (Not Apache 2.2, as it does not support Websockets at all)
  • If you are on Apache 2.2, please upgrade to the latest version of 2.4 and check if the issue persists
• SSL configured in Apache and/or Tomcat level

• The appropriate modules are loaded, specifically mod_proxy_wstunnel.so

Diagnostic Steps

• Looking at the web requests on your browser's developer tools, we see the following:

  • Requests to Synchrony (e.g. https://servername.domain/synchrony/sockjs/v1/info?t=1485365) work and return a 200 OK status. 
  • Requests to Websockets (e.g. wss://servername.domain/synchrony/sockjs/v1/808/k1g3xete/websocket) return a 404 not found error. 

  

• Confirm Apache is configured following our guides:
  • Securing your Atlassian applications with Apache using SSL
• Check that the proxy parameters have been added to your confluence_install/conf/server.xml file: Cross Site Request Forgery (CSRF) protection changes in Atlassian REST

• Confirm the following modules are all loading properly from Apache:

  LoadModule proxy_module /usr/lib/apache2/modules/mod_proxy.so
  LoadModule proxy_http_module /usr/lib/apache2/modules/mod_proxy_http.so
  LoadModule proxy_wstunnel_module /usr/lib/apache2/modules/mod_proxy_wstunnel.so
  LoadModule rewrite_module /usr/lib/apache2/modules/mod_rewrite.so

Cause

The following bug breaks the SSL handshake because it sends plain-text requests to the Websockets URL, as opposed to SSL requests:  Plain-text request is sent to WSS URL (which should be over SSL) in mod_proxy_wstunnel

Workaround

Workarounds are ways to temporally circumvent a problem, although it still exists in the application.

• A workaround is described in the following post from Stackoverflow: http://stackoverflow.com/a/22873747

• Use a different proxy:

  • Running Confluence behind NGINX with SSL
  • Proxying Atlassian server applications with Microsoft Internet Information Services (IIS)
  • How to configure Amazon Web Service Application Load Balancer with Confluence

Resolution

Upgrade to Apache 2.4.10 or higher. For some operating systems there is a fix available that has been tested using Apache version 2.4.6-45.