Summary

When attempting to create a new Confluence page, the page editor freezes:

• if there is a Reverse Proxy configured to intercept errors 
• and when Collaborative Editing is switched ON. 
  
  

Such an error message can be seen from page editor:

"Something went wrong after loading the editor. Copy your unsaved changes and refresh the page to keep editing."

Environment

• Confluence version 7.9.0 with Collaborative Editing turned ON
• NGINX is used as a Reverse Proxy and it is intercepting errors for Confluence and Synchrony, with such directives:

# Server Section in nginx.conf for the Confluence and Synchrony sites
server {
	[...]
	error_page 404 /404.html;
	proxy_intercept_errors     on;
	[...]
}

Diagnosis

• Check the Reverse Proxy configuration details for Confluence and Synchrony to confirm the directives used.

Cause

After hitting the Create button in Confluence, such a trace can be seen in the logs:

INFO [async-dispatch-5] [synchrony.middleware.logging]  {:request {:remote-addr "127.0.0.1", :uri "/synchrony/v1/data/Synchrony-92cb3632-7851-314b-9957-47c5a6223ec9/confluence-851970", :request-method :post, :query-string "state-at=@head&state-format=type-tagged&rewrite-request=true&cached=true", "x-forwarded-for" "127.0.0.1"}, :response {:status 404}}

 Intercepting this 404 can cause the Confluence application to detect that its Synchrony component is unresponsive and freeze. 

Solution

• Remove the lines below from the Reverse Proxy Configuration for Confluence and Synchrony sections.

	error_page 404 /404.html;
	proxy_intercept_errors     on;

 We do have an existing improvement request for Confluence to handle such situation gracefully under  CONFSERVER-55946 - Getting issue details... STATUS