Confluence stops communicating, any ideas?

[Erkki_Aalto]

One of our installations of Confluence 5.5.7 on RHEL 6 stopped suddenly responding. Confluence is behind an Apache ajp proxy The Apache error logs give messages like

[Thu Apr 09 12:04:43 2015] [error] (70007)The timeout specified has expired: ajp_ilink_receive() can't receive header (error log)

[Wed Apr 08 14:56:49 2015] [error] ajp_read_header: ajp_ilink_receive failed[Wed Apr 08 14:56:49 2015] [error] (70007)The timeout specified has expired: proxy: read response failed from (null) (localhost) (ssl error log)

Confluence and Tomcat think everything is fine: the logs contain no error messages.

This started  suddenly without any changes made to the configuration. Restart and boot won't help. Any ideas what this could be?

[Erkki_Aalto · Accepted solution]

Yes, there was some kind of deadlock in the Crowd server and it made Confluence noncommunicative. Restarting the Crowd server helped!

[Erkki_Aalto]

Indeed, the Crowd server (RHEL7) was patched and booted at the time the problem appeared. Unbelievable, but cannot be a coincidence.

[Erkki_Aalto]

We are using Crowd 2.8.0 for authentication. Did not mention it as this did not look like an authentication problem.