Changes for page Building Concurrent Applications with WebObjects and Scala

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1		-Given that todays processors ship with dual or quad cores and server processors ship with between 8 to 32 cores, languages like Java, Ruby, Groovy and Python are struggling to keep up.
	1	+Given that processors today ship with dual or quad cores and server processors ship with between 8 to 32 cores, programs developed in languages like Java, Ruby, Groovy, Python and Perl are struggling to exploit all that power. On the other hand, Scala, as its name suggests is built from the ground-up for [[concurrent programming>>http://en.wikipedia.org/wiki/Concurrent_computing]] - a methodology that can take advantage of these modern multi-core processors.
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3		-Scala, as its name suggests is built from the ground-up for concurrent programming - a methodology that can take advantage of these modern multi-core processors.
	3	+If you use Scala for a concurrent programming application, the chances are that you're using Scala [[Actors>>http://en.wikipedia.org/wiki/Actor_model]] to do that.
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5		-If you use Scala for a concurrent programming, the chances are that you're using Scala Actor to do that.
	5	+{{info title="Scala Actors"}}
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	7	+Concurrent programming in Scala is based on *Actors* (with an inbox) - a simple metaphor that is analogous to *Message Queues*.
	8	+
	9	+{{/info}}
	10	+
7	7	== Using Scala Actors with EOF ==
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9		-EOF being notoriously single-threaded, is incredibly unsuitable for use by Scala Actors.
	13	+EOF being notoriously single-threaded, is incredibly unsuitable for use with Scala Actors:
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	15	+* EOs are mutable objects and as such they cannot be passed safely to Scala Actors
	16	+* Fetching and updating EOs from within Scala Actors can cause [[deadlocks>>http://en.wikipedia.org/wiki/Deadlock]] with the WebObjects application
	17	+
	18	+Instead you can still use EOF but in a limited fashion - only to execute SQL.
	19	+
11	11	=== Using EOAccess to execute SQL ===
	21	+
	22	+Use Wonder API: [[ERXEOAccessUtilities.evaluateSQLWithEntityNamed()>>http://webobjects.mdimension.com/hudson/job/Wonder53/javadoc/er/extensions/eof/ERXEOAccessUtilities.html#evaluateSQLWithEntity(com.webobjects.eocontrol.EOEditingContext,%20com.webobjects.eoaccess.EOEntity,%20java.lang.String)]]
	23	+
	24	+==== Caveats ====
	25	+
	26	+If you're updating the state of EOs directly in the database using SQL from Scala Actors, you will subsequently need to refresh/refetch these EOs for the WebObjects application to see those changes.
	27	+
	28	+== EOF Alternatives ==
	29	+
	30	+You may also manipulate the database from outside the EOF stack.
	31	+
	32	+=== Squeryl ===
	33	+
	34	+[[Squeryl>>http://max-l.github.com/Squeryl/index.html]] is a strongly typed and declarative [[Domain-specific language>>http://en.wikipedia.org/wiki/Domain-specific_language]] for manipulating database objects from within the Scala language.{{quote}}{{/quote}}
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	36	+You may update the database from Scala Actors using Squeryl instead of using EOF. The advantage here is that you may access the database concurrently avoiding the single-threaded EOF bottleneck in your application.
	37	+
	38	+However the same caveat applies - you will need to refresh EOs in the EOF stack for the WebObjects application to reflect the changes made by Squeryl.