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From "Blake Sullivan (JIRA)" <>
Subject [jira] Created: (TRINIDAD-1594) FileSystemStyleCache doesn't scale due to over-synchronization
Date Mon, 12 Oct 2009 18:16:31 GMT
FileSystemStyleCache doesn't scale due to over-synchronization

                 Key: TRINIDAD-1594
             Project: MyFaces Trinidad
          Issue Type: Bug
          Components: Skinning
    Affects Versions:  1.2.12-core,  1.2.11-core
         Environment: All
            Reporter: Blake Sullivan

FileSystemStyleCache doesn't scale under load due to the use of Hashtables for _cache and
_entryCache fields.  Since Hashtables are implicitly synchronized and these objects are shared
across the entire application.  Access to these objects is shared across all users.  In addition,
there is synchronization in the remove case when modification checking is enabled in _getEntry().
 The best fix is to replace these with ConcurrentMaps (which also support an atomic remove
to handle the _getEntry() case)

Other issues:

_getDerivationKey() uses a Vector as a temporary object for no apparent reason (the implicit
synchronization isn't needed in this case since the Vector never escapes the function)

The _resolver is lazily initialized but can never change, so it is better to initialize this
field in the constructor so that it can be made final
_sourceFile and _baseName never change, so they should be final.

Note that even with these fixes, there are still further synchronization issues with this
class.  However, the biggest scalability issue is that _getEntry() still contains a synchronized
block in order to deal with the case where modification checking is enabled.  There are also
some safe publication problems, but the most important issue in the future would be getting
rid of the synchronization, at least when modification checking is off

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