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https://issues.apache.org/jira/browse/LOG4J2-3672?focusedWorklogId=888469&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-888469
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ASF GitHub Bot logged work on LOG4J2-3672:
------------------------------------------
Author: ASF GitHub Bot
Created on: 02/Nov/23 15:56
Start Date: 02/Nov/23 15:56
Worklog Time Spent: 10m
Work Description: tristantarrant commented on PR #1848:
URL: https://github.com/apache/logging-log4j2/pull/1848#issuecomment-1791008692
Log4j does not parse dates: it parses a date formatter which is then used to
print timestamps in the logs. We use the following layout:
```xml
<PatternLayout pattern="%highlight{%d{yyyy-MM-dd HH:mm:ss,SSS} %-5p (%t)
[%c] %m%throwable}{INFO=normal, DEBUG=normal, TRACE=normal}%n"/>
```
and that `%d{....} causes all the timezone initialization.
Issue Time Tracking
-------------------
Worklog Id: (was: 888469)
Time Spent: 1h 50m (was: 1h 40m)
> 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
> Priority: Major
> Time Spent: 1h 50m
> Remaining Estimate: 0h
>
> {{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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