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https://issues.apache.org/jira/browse/LANG-1355?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16196329#comment-16196329
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Charles Honton commented on LANG-1355:
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In the JDK7 implementation, synchronized method
java.util.TimeZone.getTimeZone(String id) ultimately invokes
sun.util.calendar.ZoneInfo.getZoneInfo(String id) which consults a
ConcurrentHashMap for the zone corresponding with the id. For "custom time
zone IDs", after this call is invoked and no Olson/IANA timezone is found, the
custom TimeZone instance is created and returned. This custom TimeZone
instance is never cached.
I suggest that the logic be to first check if the timezone id is a "custom time
zone IDs". If so, create and return the custom TimeZone instance; otherwise
invoke the java.util.TimeZone.getTimeZone(String id) method. All "custom time
zone IDs" will not hold the synchronized section open.
> TimeZone.getTimeZone() in FastDateParser causes resource contention
> -------------------------------------------------------------------
>
> Key: LANG-1355
> URL: https://issues.apache.org/jira/browse/LANG-1355
> Project: Commons Lang
> Issue Type: Bug
> Components: lang.time.*
> Affects Versions: 3.6
> Environment: Windows
> Reporter: Keith Boone
> Original Estimate: 48h
> Remaining Estimate: 48h
>
> Under heavy load we are seeing contention in FastDateParser.parse() on calls
> to TimeZone.getTimeZone(). TimeZone.getTimeZone() is a synchronized static
> in the Oracle JVM.
> Our proposed solution is to add a class TimeZoneCache containing a single
> method getTimeZone() which gets the requested time zone from a ConcurrentMap,
> and if not present, looks it up via TimeZone.getTimeZone() and caches it
> before returning it.
> Then replace calls to TimeZone.getTimeZone() in FastDateParser ( and
> whereever else) to calls to TimeZoneCache.getTimeZone().
> The reason to add a separate class is because it can also be used by other
> applications which heavily parse or format or do other things where TimeZone
> is repeatedly needed.
> Under extreme load we have seen an 50:1 improvement in calls to
> FastDateParser.parse(). This saves about a ms/call in our test environment,
> and reduces contention.
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