[jira] [Created] (LOG4J2-3672) Avoid invoking DateFormatSymbols.getZoneStrings() in FastDateParser

["Tristan Tarrant (Jira)" <ji...@apache.org>]

Tristan Tarrant created LOG4J2-3672:
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             Summary: Avoid invoking DateFormatSymbols.getZoneStrings() in FastDateParser
                 Key: LOG4J2-3672
                 URL: https://issues.apache.org/jira/browse/LOG4J2-3672
             Project: Log4j 2
          Issue Type: Bug
            Reporter: Tristan Tarrant


{{FastDateParser}} uses {{DateFormatSymbols.getZoneStrings()}} to construct a table of all possible timezone names to be used in parsing date patterns in pattern layouts.

Unfortunately the above call (and the equivalent call used by the JDK's {{SimpleDateFormat)}} causes initialization and caching of all timezones, resulting in a ~3MB heap overhead on x86_64. The following table summarizes the cost of triggering the caching of all timezones, including the number of instances of some related types and the amount of extra heap required.

 
|| ||LocalDateTime||LocalDate||ZoneInfo||ZoneOffset||Heap delta||
|Baseline (no TZ calls)|180|0|0| | |
|Single timezone|180|0|0|0|298|
|DateFormatSymbols.getZoneStrings()|57076|32212|602|1455|3760106|
|TimeZone.getAvailableIds() + TimeZone.getName()|36678|21674|632|1155|3024946|
|TimeZone.getAvalableIDs()|180|0|632|0|452578|

By avoiding constructions of such tables, and relying only on {{{}FastDateParser{}}}'s support for RFC-822 and GMT-style timezone names, we can avoid allocating the extra heap.

 



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