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https://issues.apache.org/jira/browse/LOG4J2-812?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14147598#comment-14147598
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Remko Popma commented on LOG4J2-812:
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You're right that just dropping in FastDateFormat to replace SimpleDateFormat
is not enough. It is the synchronized blocks that are the problem. You have a
good point that this synchronized block is not just making SimpleDateFormat
thread-safe, but is also used to cache the previous result.
Perhaps the caching logic is no longer needed if we use a faster date
formatter, or a thread-local like you suggest?
I think the next step is to do some performance measurements to compare these
options.
> Performance optimization: avoid use of synchronized SimpleDateFormat in
> DatePatternConverter
> -----------------------------------------------------------------------------------------------
>
> Key: LOG4J2-812
> URL: https://issues.apache.org/jira/browse/LOG4J2-812
> Project: Log4j 2
> Issue Type: Bug
> Components: Pattern Converters, Performance Benchmarks
> Affects Versions: 2.0.2
> Reporter: Mohit Anchlia
> Assignee: Remko Popma
> Fix For: 2.2
>
>
> Threads seem to be blocking on class
> org.apache.loggin.log4j.core.pattern.DatePatternConverter. It's short
> lived but is visible in profiler. It also is adding on to CPU. Here is the
> mail conversation on the mailing list:
> {quote}
> Ralph Goers [email protected] via logging.apache.org
> The converter uses a SimpleDateFormat which is not thread safe and so is
> synchronized. I am sure there might be minor optimizations that could be done
> to this
> What I would do is modify DatePatternConverter to
> a) use Java 8’s java.time.format.DateTimeFormatter if running on Java 8
> b) use Joda Time’s DateTimeFormat if it is present.
> c) create a pool of SimpleDateFormat objects and use those.
> Please create a Jira issue for this.
> Ralph
> {quote}
> ----
> One alternative that was suggested on the mailing list is to use commons
> lang FastDateFormat to format log timestamps.
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