[LOG4J2-1341] (GC) Avoid allocating temporary objects in Pattern Converters for PatternLayout

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 2.5
• Component/s: Pattern Converters
• Epic Link: GC-free
• Assignee: Unassigned
• Reporter: Remko Popma
• Created: 31/Mar/16 07:04
• Updated: 17/Jul/19 15:27

Description

To do
The following pattern converters can be modified to avoid creating temporary objects in their format method:

• all done

Investigate
The following pattern converters may be difficult to modify since they rely on JDK components that create temporary objects:

• ExtendedThrowablePatternConverter
• RegexReplacementConverter
• RootThrowablePatternConverter
• ThrowablePatternConverter
• UuidPatternConverter
• ClassNamePatternConverter (location information requires creating StackTraceElements)
• FileLocationPatternConverter
• FullLocationPatternConverter
• LineLocationPatternConverter
• MethodLocationPatternConverter

Done
The following pattern converters already do not allocate temporary objects in their format method:

• AbstractStyleNameConverter (since 2.8)
• HighlightConverter (since 2.7, thanks to Richard Zschech)
• StyleConverter (since 2.7, thanks to Richard Zschech)
• DatePatternConverter
• EqualsIgnoreCaseReplacementConverter (since 2.8)
• EqualsReplacementConverter (since 2.8)
• EncodingPatternConverter (since 2.8)
• IntegerPatternConverter (since 2.8)
• LevelPatternConverter
• LineSeparatorPatternConverter
• LiteralPatternConverter (unless literal contains '${')
• LoggerPatternConverter
• MapPatternConverter (since 2.8 - note that constructing a MapMessage is not garbage-free)
• MarkerPatternConverter (since 2.8)
• MarkerSimpleNamePatternConverter
• MaxLengthConverter (since 2.8)
• MdcPatternConverter (since 2.7)
• MessagePatternConverter (unless a Jansi or HTML renderer is configured or message has '${' lookups)
• NamePatternConverter
• NanoTimePatternConverter
• NdcPatternConverter (since 2.8 ContextStack implementations implement the StringBuilderFormattable interface - note that the ThreadContext stack is cloned for each log event and is not garbage-free)
• RelativeTimePatternConverter (since 2.8)
• SequenceNumberPatternConverter (since 2.8)
• ThreadIdPatternConverter
• ThreadNamePatternConverter
• ThreadPriorityPatternConverter
• VariablesNotEmptyReplacementConverter (since 2.8)

Issue Links

• is related to: LOG4J2-1367 Performance improvement for %highlight with Normal
• links to: GitHub Pull Request #34
• links to: GitHub Pull Request #35
• links to: GitHub Pull Request #36