[jira] [Comment Edited] (LOG4J2-2031) Log4j2 log file not reflecting application log function calls

["Remko Popma (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LOG4J2-2031?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16153768#comment-16153768 ] 

Remko Popma edited comment on LOG4J2-2031 at 9/5/17 3:01 PM:
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I haven't looked in great detail, but some initial observations:
* the PatternLayout uses location ( {{%L}} ). This is implemented by walking the stack trace for every log event. This is [known to be very slow|https://logging.apache.org/log4j/2.x/performance.html#asyncLoggingWithLocation].
* rollover is configured in the test to be size-based after 20MB, and I suspect that the test spends a lot of its time doing rollovers. What is measured in this test is likely very different from   the actual logging performance in your real-life application. 
* you can get another small performance boost by using one of the predefined date formats like {{%d\{DEFAULT\}}}. (These use a highly optimized custom formatter.)
* the tests also include initialization time in their measurement. Log4j2 is slower to initialize than Log4j-1.2. We're aware of that but don't have plans to optimize that area. Not sure how important  startup time is for your applications, but may I suggest adding a separate loop (with the same number of iterations) that is not measured, before starting to measure? That will also allow the JVM to warm up and should give more realistic results. 

I need to run your example to see what's causing the reordering. 


was (Author: remkop@yahoo.com):
I haven't looked in great detail, but some initial observations:
* the PatternLayout uses location ( {{%L}} ). This is implemented by walking the stack trace for every log event. This is [known to be very slow|https://logging.apache.org/log4j/2.x/performance.html#asyncLoggingWithLocation].
* rollover is configured in the test to be size-based after 20MB, and I suspect that the test spends a lot of its time doing rollovers. What is measured in this test is likely very different from   the actual logging performance in your real-life application. 
* you can get another small performance boost by using one of the predefined date formats like {{%d\{DEFAULT\}}}. (These use a highly optimized custom formatter.)

I need to run your example to see what's causing the reordering. 

> Log4j2 log file not reflecting application log function calls
> -------------------------------------------------------------
>
>                 Key: LOG4J2-2031
>                 URL: https://issues.apache.org/jira/browse/LOG4J2-2031
>             Project: Log4j 2
>          Issue Type: Bug
>          Components: Appenders
>    Affects Versions: 2.8.2, 2.9.0
>         Environment: Windows, Sun Java 8.
>            Reporter: Colin McDowell
>             Fix For: 2.9.1
>
>         Attachments: CapacityTest.java, log4j2.xml, pom2.xml
>
>   Original Estimate: 672h
>  Remaining Estimate: 672h
>
> Was hoping to move our numerous J2EE projects from Log4j to Log4j2 for the performance improvements.  I put together a small test case that writes a string pattern to a Rolling File.  There is a 6 digit sequence number at the start of the log message.  This allows me to quickly see if all the log requests are making it into the log file. I attach the test case and log4j2.xml.  The log4j2.xml uses an asynchronous appender.
> What I observe in the output log file is that after a short interval (120 or so entries) the logged are appearing in the wrong order, and entries can be missing.  The missing entries issues especially shows up when rolling to the next log file.
> Perhaps there is a deliberate decision to not to guarantee log file accurately for speed.  However we need the logs to accurately reflect what the application is logging.  I have also noticed the performance is 25% worse in Log4j2 than Log4j when not using the asynchronous appender.  So that rather kills us using Log4j2 at the moment.



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