[jira] [Commented] (LOG4J2-1382) Performance regression in RewriteAppender

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

    [ https://issues.apache.org/jira/browse/LOG4J2-1382?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15276246#comment-15276246 ] 

Remko Popma commented on LOG4J2-1382:
-------------------------------------

RingBufferLogEvent has a method {{initializeBuilder(Log4jLogEvent.Builder)}} for this purpose. Planning to copy this.

> Performance regression in RewriteAppender
> -----------------------------------------
>
>                 Key: LOG4J2-1382
>                 URL: https://issues.apache.org/jira/browse/LOG4J2-1382
>             Project: Log4j 2
>          Issue Type: Bug
>          Components: Appenders
>    Affects Versions: 2.6
>            Reporter: Remko Popma
>            Assignee: Remko Popma
>             Fix For: 2.6
>
>
> While working on LOG4J2-1179, I ran into these benchmark results:
> {code}
> Benchmark                                                         Mode  Samples           Score            Error  Units
> o.a.l.l.p.j.Log4j2AppenderComparisonBenchmark.appenderRewrite    thrpt        5    44263670.008 ±   17389305.070  ops/s
> o.a.l.l.p.j.Log4j2AppenderComparisonBenchmark.end2endRewrite     thrpt        5       37254.554 ±      16440.919  ops/s
> {code}
> In plain English: directly calling RewriteAppender.append(LogEvent) can do 44 million ops/sec, but when calling rewriteLogger.debug(msg) to invoke a logger that calls this appender, all of a sudden throughput drops to 37 _thousand_ ops/sec. That's 1000x slower. Fishy...
> Turns out that when rewriting the event we are now including caller location information (taking a snapshot of the stack and walking it). Ouch.
> This is a regression caused by the garbage-free stuff. Rewriting the event makes a copy of the event and avoids calling LogEvent.getSource() only if the event is an instance of Log4jLogEvent, but now we are passing in MutableLogEvent. 
> The fix is to update Log4jLogEvent.Builder to also avoid calling getSource when copying from a MutableLogEvent.



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