[LOG4J2-3560] Logger$PrivateConfig.filter(Level, Marker, String) allocates empty varargs array

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.18.0
• Fix Version/s: 2.18.1
• Component/s: Core
• Assignee: Carter Kozak
• Reporter: David Schlosnagle
• Created: 23/Jul/22 05:53
• Updated: 22/Aug/22 21:06
• Resolved: 27/Jul/22 18:02

Description

While reviewing some JFR profiles, I notice significant allocations of Object[] due to use of some isEnabled conditions that ends up using empty varargs invoking org.apache.logging.log4j.core.Filter#filter(Logger, Level, Marker, String, Object...), for example the following call trace:

at org.apache.logging.log4j.core.Logger$PrivateConfig.filter(Level, Marker, String)
at org.apache.logging.log4j.core.Logger.isEnabled(Level, Marker, String)

We can avoid allocation on this hot path when invoking Filter#filter(Logger, Level, Marker, String, Object...) by reusing an empty object array for the varargs.

Issue Links

• relates to: LOG4J2-3566 DefaultLogBuilder is not garbage-free
• links to: GitHub Pull Request #974