How to Enable Garbage Collection (GC) Logging

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Purpose

Garbage collection logs are useful when trying to isolate issues within Java-based applications as they will pinpoint blocked, hung or stuck threads that may be causing downstream effects in the application. It is always useful to collect at least 10 minutes of garbage collection logs, but analysis accuracy is often increased by the amount of recent log data to review.

Solution

For Linux

Add the following parameters into your Confluence System Properties, in the <confluence-install>/bin/setenv.sh file (be sure to enter the path for your <confluence-home> directory)

-Xloggc:<confluence-home>/logs/`date +%F_%H-%M-%S`-gc.log -XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+PrintTenuringDistribution -XX:+PrintGCCause
-XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=10 -XX:GCLogFileSize=5M

The parameter -XX:+PrintGCCause was introduced within Java 1.7.0_45 and will not work if you are using a version of Java prior to that version. Please check the version of Java that is being used by your instance of Confluence prior to using this flag.

For Windows

Batch file

If you start Confluence using 'start-confluence.bat', add the below code to setenv.bat

rem Create a timestamp with date and time, replacing ' ' with '0' and '/' with '-'
set atlassian_timestamp=%DATE:~-4%.%DATE:~4,2%.%DATE:~7,2%_%TIME:~0,2%.%TIME:~3,2%.%TIME:~6,2%
set atlassian_timestamp=%atlassian_timestamp: =0%
set atlassian_timestamp=%atlassian_timestamp:/=-%
set atlassian_logsdir=%~dp0..\logs

set CATALINA_OPTS=%CATALINA_OPTS% -Xloggc:"%atlassian_logsdir%\gc-%atlassian_timestamp%.log"
set CATALINA_OPTS=%CATALINA_OPTS% -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=10 -XX:GCLogFileSize=5M -XX:+PrintGCCause
set CATALINA_OPTS=%CATALINA_OPTS% -XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+PrintTenuringDistribution 

NB: This will create the garbage collection logs in the <confluence-install> directory.

Service

If you start Windows as a service, add the below to the service by following these steps (be sure to enter the path for your <confluence-home> directory)

-Xloggc:<confluence-home>\logs\gc-%t.log
-XX:+PrintGCDetails
-XX:+PrintGCDateStamps
-XX:+PrintGCCause
-XX:+PrintTenuringDistribution
-XX:+UseGCLogFileRotation
-XX:NumberOfGCLogFiles=10
-XX:GCLogFileSize=5M
Description

Garbage collection logs are useful when trying to isolate issues within Java-based applications as they will pinpoint blocked, hung or stuck threads that may be causing downstream effects in the application. It is always useful to collect at least 10 minutes of garbage collection logs, but analysis accuracy is often increased by the amount of recent log data to review.

Product Confluence, Bitbucket, Jira, Bamboo
Last modified on Oct 12, 2018

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