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https://issues.apache.org/jira/browse/LOG4J2-2157?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16300396#comment-16300396
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Gary Gregory commented on LOG4J2-2157:
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Indeed, that seems to be a problem. I'll try to take a look this week unless
someone else beats me to it.
> Don't create exit message in traceExit(R) when logging is disabled
> ------------------------------------------------------------------
>
> Key: LOG4J2-2157
> URL: https://issues.apache.org/jira/browse/LOG4J2-2157
> Project: Log4j 2
> Issue Type: Improvement
> Affects Versions: 2.10.0
> Reporter: Malte Skoruppa
> Labels: performance
>
> We recently added a
>
> {{return traceExit(retvalue);}}
> to a given method in our project, where before we simply had
> {{return retvalue;}}
> We then noticed that the running time of our software skyrocketed because of
> this change (the given method that this traceExit call was added to is called
> _very_ often). On a particular test case, the execution time grew from 3
> minutes to 15 minutes.
> The surprising thing: *This happened even when logging at TRACE level was
> disabled.*
> After profiling, we found out that traceExit(R) _always_ internally generates
> a message, even when logging at TRACE level is disabled. This can become
> extremely costly when traceExit(R) is called very often, and it doesn't make
> any sense because these messages are not logged anyway.
> +Technical explanation:+
> Essentially, in org.apache.logging.log4j.spi.AbstractLogger, the method
> traceExit(final R result) calls the method exit(final String fqcn, final
> String format, final R result), which in turn makes the call
> logIfEnabled(fqcn, Level.TRACE, EXIT_MARKER, exitMsg(format, result), null).
> This means that exitMsg(format, result) is always called, even when logging
> on TRACE level is disabled. Thus, a StringBuilder is invoked every time,
> which constructs a String and then throws it away because logging is disabled
> anyway.
> This implies that traceExit(R) can only be used for methods that are not
> called very often. For methods that are called often, calling traceExit(R)
> cannot be sensibly used because it utterly kills performance.
> Could you fix this? It seems unnecessary to call exitMsg(final String format,
> final Object result) when logging is disabled anyway.
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