Purpose

When Confluence is behaving slowly, and you need more information as to what part of it is being slow, this page provides a way of collecting thread dumps (a breakdown of what every thread is doing for a Java process) and the output of top (shows what each native OS thread is consuming as far as resources are concerned). This breakdown could normally be collected with something like jProfiler as per Use jProfiler to analyse Jira application performance - in this example we're using native (free) tools to collect information.

 This will only work for *nix systems and needs jstack to be installed (should be by default). For Windows please see Generating a Thread Dump Externally.

Resolution

• Create a script called dump_reports on /tmp directory and paste the block command below:

  #!/bin/bash
  CONFLUENCE_PID=`ps aux |grep -i confluence |awk '{print $2}' |head -n1`
  DUMP_HOME="/tmp/dump_home"
  COUNT=0
  if [ ! -d $DUMP_HOME ]; then
  	mkdir $DUMP_HOME
  fi
  while true; do
  	top -b -H -p $CONFLUENCE_PID -n 1 |grep CPU -A 5 | awk '{print  $(2-1), "\t", $9}' |head -n 6 > $DUMP_HOME/confluence_cpu_usage.`date +%s`.txt; jstack $CONFLUENCE_PID > $DUMP_HOME/confluence_threads.`date +%s`.txt
  	sleep 10 
  	COUNT=$(($COUNT + 1));
  	if [ $COUNT -gt 5 ]; then
  		echo ""
  		break
  		exit 1
  	fi
  done
  LIST=`ls -l $DUMP_HOME/confluence_cpu* |awk '{print $9}'`
  for b in $LIST; do
  	echo "" > $DUMP_HOME/threads.txt
  	CONVERT=`cat $b |grep -v PID | awk '{print $1}'`
  		for i in $CONVERT; do
  			printf '%x\n' $i >> $DUMP_HOME/threads.txt
  		done
  	paste $b $DUMP_HOME/threads.txt >> $DUMP_HOME/threads_result.txt
  done

• Then give permissions to the script with the following command:

  chmod +x /tmp/dump_reports

• Now you can run the script:

  /tmp/dump_reports

• The result will be something like that:

  PID 	 %CPU	
  6149 	 2.0	1805
  5872 	 0.0	16f0
  5873 	 0.0	16f1
  5874 	 0.0	16f2
  5875 	 0.0	16f3
  
  PID 	 %CPU	
  5880 	 57.4	16f8
  6393 	 45.5	18f9
  

• Above we can see the PID of the thread, the percentual of CPU usage and the hexadecimal PID which can be used to read the confluence_threads files within the logs more detailed about what is happening.