[LOG4J2-1349] Garbage-free ThreadContext map

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.5
• Fix Version/s: 2.7
• Component/s: API
• Epic Link: GC-free
• Assignee: Remko Popma
• Reporter: Remko Popma
• Created: 02/Apr/16 00:34
• Updated: 03/Nov/16 05:19
• Resolved: 11/Sep/16 06:55

Description

The current ThreadContext map and stack implementations allocate temporary objects. This ticket is to investigate and track the work for alternative implementations that are garbage-free.

Both DefaultThreadContextMap and DefaultThreadContextStack are copy-on-write data structures: each modification replaces the ThreadLocal object with a modified copy. The advantage of this approach is that there is no need to make a copy for each LogEvent.

Also, DefaultThreadContextMap uses a JDK map, the JDK collections tend to allocate a lot of temporary objects.

Issue Links

• is depended upon by: LOG4J2-1401 Support changing the log level for all messages related to some domain object
• is related to: LOG4J2-1648 Allow non-String values in the ThreadContext
• is related to: LOG4J2-1607 Improve performance of SortedArrayStringMap data structure
• relates to: LOG4J2-1516 Add ThreadContextMap.putAll(Map<String, String>)
• relates to: LOG4J2-1517 Add ThreadContext.setContext(Map<String, String>)
• relates to: LOG4J2-1519 Add ThreadContext.putAll(Map<String, String>)
• relates to: LOG4J2-1010 Injectable context properties
• relates to: LOG4J2-1447 Garbage-free data structure for LogEvent's context map data
• relates to: LOG4J2-1660 ThreadContext to expose ReadOnlyThreadContextMap internal data structure
• supercedes: LOG4J2-1282 Make RingBufferLogEvent::mergePropertiesIntoContextMap allocation-free if possible