Problem

Confluence is causing large CPU spikes intermittently on Windows. Confluence performance becomes slow and sometimes crashes entirely.

Diagnosis

Follow Generating a Thread Dump Externally to generate multiple thread dumps. Check for blocked threads that contain a lock for java.security.SecureRandom

The following is an example blocked thread:

"http-nio-80-exec-7" #166 daemon prio=5 os_prio=0 tid=0x000000002f05e000 nid=0x1764 waiting for monitor entry [0x0000000043323000]
   java.lang.Thread.State: BLOCKED (on object monitor)
	at java.security.SecureRandom.nextBytes(Unknown Source)
	- waiting to lock <0x00000006873088c8> (a java.security.SecureRandom)
	at java.util.UUID.randomUUID(Unknown Source)
	at com.atlassian.confluence.content.render.xhtml.editor.macro.DefaultMacroIdSupplier.get(DefaultMacroIdSupplier.java:19)

Cause

There is a known issue with Java and Tomcat in he library used for random number generation in Sun's JVM which relies on /dev/random. This random number generator can block the application server process from starting 'because on some operating systems /dev/random waits for a certain amount of "noise" to be generated on the host machine before returning a result' (see Avoiding JVM Delays Caused by Random Number Generation).

Workaround

1. Stop Confluence
2. Add the flag -Djava.security.egd=file:/dev/urandom to the Java arguments to use dev/urandom by following Configuring System Properties
3. Start Confluence