Problem

Confluence becomes unresponsive and sees spikes in CPU usage.

The following appears in the catalina.out log"

15-Dec-2017 01:38:05.706 WARNING [ContainerBackgroundProcessor[StandardEngine[Standalone]]] org.apache.catalina.valves.StuckThreadDetectionValve.notifyStuckThreadDetected Thread "http-nio-8444-exec-17" (id=205) has been active for 63,519 milliseconds (since 12/14/17 11:27 AM) to serve the same request for https://confluence.com/confluence/display/AB/page+title and may be stuck (configured threshold for this StuckThreadDetectionValve is 60 seconds). There is/are 2 thread(s) in total that are monitored by this Valve and may be stuck.
 java.lang.Throwable
	at java.util.regex.Pattern$Curly.match0(Pattern.java:4274)
	at java.util.regex.Pattern$Curly.match(Pattern.java:4236)
	at java.util.regex.Pattern$Curly.match0(Pattern.java:4281)
	at java.util.regex.Pattern$Curly.match(Pattern.java:4236)
	at java.util.regex.Pattern$Slice.match(Pattern.java:3974)
	at java.util.regex.Pattern$Curly.match0(Pattern.java:4274)
	at java.util.regex.Pattern$Curly.match(Pattern.java:4236)
	at java.util.regex.Pattern$BmpCharProperty.match(Pattern.java:3800)
	at java.util.regex.Pattern$Start.match(Pattern.java:3463)
	at java.util.regex.Matcher.search(Matcher.java:1248)
	at java.util.regex.Matcher.find(Matcher.java:637)
	at ch.bitvoodoo.confluence.plugins.viewtracker.util.Utils.containsTrackingMacro(Utils.java:61)

Environment

• Versions 5.1.1 or 5.1.2 of the  plugin is installed
  
  

Diagnostic Steps

• Create 6 external thread dumps each spaced 10 seconds apart: Generating a Thread Dump Externally

• Look for this long running thread:

  "http-nio-8444-exec-3" #191 daemon prio=5 os_prio=0 tid=0x00007fc67905b000 nid=0x2e24 runnable [0x00007fc601714000]
     java.lang.Thread.State: RUNNABLE
  	at java.util.regex.Pattern$Curly.match0(Pattern.java:4274)
  	at java.util.regex.Pattern$Curly.match(Pattern.java:4236)
  	at java.util.regex.Pattern$Curly.match0(Pattern.java:4281)
  	at java.util.regex.Pattern$Curly.match(Pattern.java:4236)
  	at java.util.regex.Pattern$Slice.match(Pattern.java:3974)
  	at java.util.regex.Pattern$Curly.match0(Pattern.java:4274)
  	at java.util.regex.Pattern$Curly.match(Pattern.java:4236)
  	at java.util.regex.Pattern$BmpCharProperty.match(Pattern.java:3800)
  	at java.util.regex.Pattern$Start.match(Pattern.java:3463)
  	at java.util.regex.Matcher.search(Matcher.java:1248)
  	at java.util.regex.Matcher.find(Matcher.java:637)
  	at ch.bitvoodoo.confluence.plugins.viewtracker.util.Utils.containsTrackingMacro(Utils.java:61)

• Or you can try disabling the plugin and monitor the application to see if the issue is resolved

Cause

This is caused by a bug in the plugin: VIEWTRACKER-171.

Resolution

Uninstall the plugin and install an earlier version, or upgrade past the fix version when the bugfix is released.