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From "Remko Popma (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LOG4J2-1297) Document "gc-free" configuration and performance
Date Tue, 23 Feb 2016 20:31:18 GMT

    [ https://issues.apache.org/jira/browse/LOG4J2-1297?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15159593#comment-15159593

Remko Popma commented on LOG4J2-1297:

I don't see an easy way to handle LOG4J2-1282 at the moment. An additional complication is
that StrSubstitutor is involved, and that class is not exactly GC-free...

> Document "gc-free" configuration and performance
> ------------------------------------------------
>                 Key: LOG4J2-1297
>                 URL: https://issues.apache.org/jira/browse/LOG4J2-1297
>             Project: Log4j 2
>          Issue Type: New Feature
>          Components: Documentation
>    Affects Versions: 2.5
>            Reporter: Remko Popma
>            Assignee: Remko Popma
> Update the site with a description of which configurations are GC-free (i.e., that don't
create temporary objects in steady running state).
> Currently that means
> * Loggers are all asynchronous (Log4jContextSelector is set to org.apache.logging.log4j.core.async.AsyncLoggerContextSelector)
> * the configuration does not contain a <Properties> section
> * the "steady-state" appenders are either RandomAccessFile or RollingRandomAccessFile
Appenders (logging to any other appender will cause temporary objects to be created - including
> * the Layout is a PatternLayout that uses one of the pre-defined date formats, does not
have any regular expression replacements, and does not have lookups (TODO: may need to restrict
this further)
> * in user code, when logging a parameterized message, the number of parameters is no
more than ... (TBD pending discussion in LOG4J2-1278)
> * in user code, when logging a parameterized message, parameters of primitive type are
boxed in a reused StringBuilder (Log4j provides a utility to make this relatively painless)
> Furthermore, we need to explain that some of this functionality depends on ThreadLocals
and so is disabled by default in web applications to prevent memory leaks. The page should
also explain how to manually switch off the use of ThreadLocals.
> Finally, the page should show a performance test comparison similar to the [performance
section|http://logging.apache.org/log4j/2.x/manual/async.html#Performance] on the Async Loggers
page. I'm thinking a comparison between Logback, Log4j-1, Log4j-2.0, Log4j-2.6 "classic" and
Log4j-2.6 "gc-free" would be ideal.

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