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https://issues.apache.org/jira/browse/MYFACES-3705?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Leonardo Uribe resolved MYFACES-3705.
-------------------------------------
Resolution: Fixed
Fix Version/s: 2.1.12
> Concurrency "feature" in FaceletCacheImpl
> -----------------------------------------
>
> Key: MYFACES-3705
> URL: https://issues.apache.org/jira/browse/MYFACES-3705
> Project: MyFaces Core
> Issue Type: Bug
> Components: General
> Affects Versions: 2.1.0
> Environment: All
> Reporter: Pasi Salminen
> Assignee: Leonardo Uribe
> Priority: Trivial
> Fix For: 2.1.12
>
> Original Estimate: 1h
> Remaining Estimate: 1h
>
> I'm implementing my own FaceletCache which is decorating
> org.apache.myfaces.view.facelets.impl.FaceletCacheImpl by adding my own
> caching policy. When I was studying the code I'm decorating, I noticed that
> scrictly speaking it was not behaving. The problem lies in this code snippet
> (and the same for metadata facelets):
> if (_refreshPeriod != NO_CACHE_DELAY)
> {
> Map<String, DefaultFacelet> newLoc = new HashMap<String,
> DefaultFacelet>(_facelets);
> newLoc.put(key, f);
> _facelets = newLoc;
> }
> First of all, multiple concurrent modifications of _facelets map may cause
> lost updates. Think what happens when thread one copies the hashmap, updates
> local copy but before it sets the reference, thread b does the same. One
> update is now lost. In reality, the number of concurrent threads and number
> of lost updates may be much larger. The second thing is that the new
> reference set to _facelets is not quaranteed to be visible to other threads
> due to missing synchronization. To prove my concerns, I created a small test
> bench which proved my doubts and was able to show both lost updates and
> visibility problem. When I modified the map to be ConcurrentHashMap and just
> used put-method all problems vanished. So instead of
> Map<String, DefaultFacelet> newLoc = new HashMap<String,
> DefaultFacelet>(_facelets);
> newLoc.put(key, f);
> _facelets = newLoc;
> I used
> _facelets.put( key,f );
> I know it may not be a problem, possibly just causing multiple loads of same
> resource, but still I don't feel comfortable with the code behaving
> concurrency-wise incorrectly.
> BR, Paci
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