[LOG4J2-1595] (GC) Avoid allocating temporary objects in Filter implementations

• Type: New Feature
• Status: Resolved
• Priority: Major
• Resolution: Incomplete
• Affects Version/s: 2.6.2
• Fix Version/s: 2.8
• Component/s: Filters
• Epic Link: GC-free
• Assignee: Remko Popma
• Reporter: Remko Popma
• Created: 18/Sep/16 10:57
• Updated: 13/Nov/16 12:51
• Resolved: 13/Nov/16 12:51

Description

Review current Filter implementation classes and change them to be garbage-free where feasible. Document on the web site which filters are garbage free and which are not.

Current status

• BurstFilter (allocates, non-trivial to change)
• CompositeFilter (adding & removing elements produces garbage for thread safety, no allocation in steady state) - since 2.6
• DynamicThresholdFilter (garbage free since 2.6)
• LevelRangeFilter (garbage free since 2.8)
• MapFilter (garbage free since 2.8, but logging a MapMessage still allocates)
• MarkerFilter (garbage free since 2.8)
• RegexFilter (not garbagefree due to JDK regex library)
• ScriptFilter (not garbagefree: creates new Binding object for each event)
• StructuredDataFilter (garbage free since 2.8)
• ThreadContextMapFilter (garbage free since 2.8)
• ThresholdFilter (garbage free since 2.8)
• TimeFilter (uses Calendar to calculate millisSinceMidnight for each event. Can refactor by reusing some of the FixedDateFormat logic.)

Issue Links

• supercedes: LOG4J2-1590 AbstractFilter should call vararg method from methods with unrolled parameters