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https://issues.apache.org/jira/browse/LOG4J2-1176?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14984384#comment-14984384
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Remko Popma commented on LOG4J2-1176:
-------------------------------------
Yourkit is indeed a fine project. We should get an [open source
license|https://www.yourkit.com/purchase/#licenses] for it. I finally made some
progress on this.
# One leak was caused by the StatusLogger. Objects were retained in the
ParameterizedMessage objects kept in the StatusLogger's bounded queue of
StatusData objects. I introduced a special MessageFactory for StatusLogger that
does not keep a reference to the parameter objects. (in master in commit
abc0f948)
# Another leak is caused by the design of OutputStreamManager: it has a
reference to the layout of the first Appender it was created for. The leak
occurs as follows: DefaultConfiguration creates a ConsoleAppender with a
PatternLayout. PatternLayout has a reference to its Configuration. As a result,
the OutputStreamManager retained in AbstractManager.MAP keeps a reference to
the first DefaultConfiguration (whether this config is STOPPED or not).
Still thinking on how to fix #2.
> Memory leak from first loaded web app when log4j jars are in Tomcat's lib
> folder
> --------------------------------------------------------------------------------
>
> Key: LOG4J2-1176
> URL: https://issues.apache.org/jira/browse/LOG4J2-1176
> Project: Log4j 2
> Issue Type: Bug
> Components: Configurators, Web/Servlet
> Affects Versions: 2.4.1, 2.5
> Environment: Tomcat 7.0.50 or Tomcat 7.0.65, jdk1.8.0_51, Win 10
> Reporter: Remko Popma
> Fix For: 2.5
>
> Attachments: webapp.war
>
>
> When the log4j2 jar files are in $catalina.home/lib, the first web
> application that is loaded will be reported by Tomcat as having a memory leak
> from loaded classes.
> *1. Steps to reproduce*
> # Install Tomcat 7.0.65 afresh
> # Copy log4j-api-2.5-SNAPSHOT.jar, log4j-core-2.5-SNAPSHOT.jar,
> log4j-web-2.5-SNAPSHOT.jar into $catalina.home/lib.
> # (Optional) place a log4j2.xml config file with status="true" in
> $catalina.home/lib. This helps to confirm that the web app which is loaded
> first causes the warning.
> # Edit $catalina.home/conf/catalina.properties: add
> {{log4j2.disable.jmx=true}} (eliminate JMX as the culprit)
> # Edit $catalina.home/conf/tomcat-users.xml to give yourself permission to
> access the Tomcat Web App Manager
> # Start Tomcat
> # Open the [Manager App|http://localhost:8080/manager/html]
> # Reload the Tomcat Documentation (/docs) web app
> # Click the "Find Leaks" button under Diagnostics at the bottom of the
> Manager App page
> The following warning is displayed:
> {quote}
> The following web applications were stopped (reloaded, undeployed), but their
> classes from previous runs are still loaded in memory, thus causing a memory
> leak (use a profiler to confirm):
> /docs
> {quote}
> *2. Use custom web app to prove the web app loaded first always has this
> issue*
> Use the attached web app to test the order of deployment.
> # Restart Tomcat
> # Deploy web app (containing its own log4j2.xml)
> # Restart Tomcat again (note that the custom web app is loaded first)
> # Reload /docs app: no memory leak
> # Reload /webapp: gives memory leak warning
> Different order:
> # Undeploy custom web app
> # Restart Tomcat ( /docs web app is loaded first)
> # Deploy custom web app
> # Reload /docs app: gives memory leak warning
> # Reload /webapp: no memory leak
> I have tried to use [Eclipse Memory Analyzer|https://eclipse.org/mat/] to
> find out where the leak is, but without success.
> (Note that the problem also happens with the default configuration (when no
> log4j2.xml config is found), this may narrow things down a little... Perhaps
> this has something to do with the StatusLogger?)
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