Check the logs

You can find the Confluence application logs at <home-directory>/logs/atlassian-confluence.log and Synchrony specific logs at   <home-directory>/logs/atlassian-synchrony.log .

Restart Synchrony

If Synchrony is managed by Confluence, go to  > General Configuration > Collaborative editing and choose Restart Synchrony.  

If you run your own standalone Synchrony cluster, manually restart Synchrony on each node. 

Check port 8091 is available

Synchrony runs on port 8091 by default. If this port is already in use by another application on your server you can use the the synchrony.port system property to change it to an available port.  

(If you're using Confluence 6.0.3 or earlier you'll need to use reza.port instead of synchrony.port.)

See Configuring System Properties to find out how to change this. 

For Confluence Data Center the way you run Synchrony is a little different. See Configuring Synchrony for more information.

Reverse proxy issues

If you have configured your reverse proxy, but can't edit pages, here's some things to check in your configuration:

• Go to installation-directory>/conf/server.xml  and check the Connector directive. Make sure that you have correct values for <protocol> and <proxyName>. See the examples in the guides below for more information.  
• The http connector always needs to be present in the <installation-directory>/conf/server.xml file, even if you're configuring SSL or using the AJP connector. The Synchrony health check uses HTTP and will fail if this connector is not present. Alternatively, if you do not want to include the http connector, you can use the synchrony.proxy.healthcheck.disabled system property to disable the health check. 
• If you're using Apache, make sure you're using Apache 2.4 (with WebSockets support) and all required modules have been enabled (mod-proxy, mod_rewrite, proxy_wstunnel).
• If you're using Apache and want to connect directly to Synchrony, in your proxy config file, make sure you've included /synchrony and that the order of the Confluence and Synchrony directives and location blocks is correct. See the examples in the guides below for more information. 

See Administering Collaborative Editing to find out more about possible proxy and SSL configurations then check out the following guides for more information on how to include Synchrony in your reverse proxy config, if you want to connect direct to Synchrony:

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

Forward proxy issues

If you're using a forward or outbound proxy, you will need to add the IP that Synchrony listens on to your config to ensure it is bypassed. See Configuring Web Proxy Support for Confluence for more info.

By default, the IP is 127.0.0.1, or it will be the value of the synchrony.host system property, if you've customized the hostname or IP that Confluence uses to connect to Synchrony. 

Websocket issues

Collaborative editing works best with a WebSocket connection. If one can't be established due to a timeout, or a proxy server or firewall that doesn't allow WebSocket connections, the editor will attempt to connect via an XML HTTP Request (XHR).

You can use http://websocket.org/echo.html to perform a quick HTML5 WebSocket test against an echo server.

It's possible to verify the websocket connection using the developer tools in your browser. In the following example, we'll use Chrome to check the websocket connection:

1. Open the Chrome Developer Tools (Shift + CTRL + J)
2. Select the Network tab
3. Select the WS filter to show only WebSocket traffic
4. Edit a Confluence page
5. Select the websocket connection: ws://<confluence-url>/synchrony-proxy/v1/bayeux-sync1
6. Select the Frames/Messages tab to see the traffic between browser and the WebSocket.

SSL issues

Synchrony cannot accept direct HTTPS connections, so you will need to terminate SSL at your reverse proxy or load balancer, or at Tomcat if you are not using a reverse proxy.

Memory issues

If you experience out of memory errors related to Synchrony, you can change the heap size allocated to Synchrony using the synchrony.memory.max system property.

If you're Confluence 6.0.3 or earlier you'll need to use reza.memory.max instead of synchrony.memory.max.

See Configuring System Properties to find out how to change this.  

For Confluence Data Center the way you run Synchrony is a little different. See Configuring Synchrony for more information.

Multiple Synchrony processes

If you see an error immediatley in the editor, but Confluence reports that Synchrony is running, check to make sure that you only have one Synchrony process running. 

If you do have multiple Synchrony processes running, stop Confluence, kill the additional Synchrony processes and then restart Confluence.

You can avoid this problem by always using stop-confluence.sh / stop-confluence.bat to stop Confluence, rather than simply closing the Tomcat window. 

Mixed Synchrony modes in cluster

If you're running Confluence in a cluster, all of your Confluence nodes must connect to Synchrony in the same way.

If users are able to use collaborative editing on one Confluence node, but not on another Confluence node, go to  > General Configuration > Clustering, then on each node choose Collaborative editing. 

Make sure all of your Confluence nodes are reporting the same Synchrony mode - either Managed by Confluence, or Standalone Synchrony cluster. 

You can access all nodes in this way, you don't need to hit a specific node in your browser.

Incompatible browser extensions

Some third party browser extensions that interact with the editor, such as Grammarly, may not function correctly with collaborative editing. See (Archived) Confluence Collaborative Editing blocks Grammarly Extension to find out how to disable Grammarly for just your Confluence site.

Firewall or anti-virus interference

We've had a few reports of firewalls or anti-virus software blocking some requests to the server, resulting in unexpected behavior in the editor. You may need to add Confluence to your whitelist / trusted URLs if you experience issues. See Weird Page or Editor Behaviors with Kaspersky Internet Security for more information.

Too many people in the editor

A maximum of 12 people can edit a page at the same time. This means that people can't enter the editor if there are already 12 other people editing the page, and will need to wait until someone leaves.  

Administrators can increase or decrease this limit using a the confluence.collab.edit.user.limit system property.