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?