CPU Usage Spikes to 100 percent on Virtual Server and Confluence Becomes Unavailable
Symptoms
Suddenly, when attempting to connect to Confluence, there is no response from the server resulting in a timeout. Also, the CPU usage is pegged at 100% or close to it but we may have plenty of available memory. This situation may resolve after some time and seem to come back at random.
At some situation, the virtual server always starts at 100% CPU usage. However, Confluence doesn't become slow and there's no timeout error in the log. If this is the case, proceed to Resolution : Alternative.
Cause
An alternative cause for instances with a very large user base is CONF-30581 - Getting issue details... STATUS . If disabling this plugin doesn't improve your CPU usage, then this is not the problem.
An option called 'memory ballooning' may be enabled on the server which swaps unused memory of the virtual machine out to harddisk. When the JVM goes to garbage collect against the heap, this process can take a very long time and tax the CPU heavily.
Resolution
Disable memory ballooning for the virtual machine.
Alternative
Upgrade / uninstall all the incompatible plugins to the highest compatible version.