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Version 144.1 by Ravi Mendis on 2010/03/24 23:36
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Ravi Mendis 141.1 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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Ravi Mendis 141.1 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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Ravi Mendis 141.1 5 {{info title="Scala Actors"}}
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Ravi Mendis 141.1 7 Concurrent programming in Scala is based on *Actors* (with an inbox) - a simple metaphor that is analogous to *Message Queues*.
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9 {{/info}}
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Ravi Mendis 50.1 11 == Using Scala Actors with EOF ==
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Ravi Mendis 141.1 13 EOF being notoriously single-threaded, is incredibly unsuitable for use with Scala Actors:
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Ravi Mendis 143.1 15 * EOs are mutable objects and as such they cannot be passed safely into Scala Actors
Ravi Mendis 141.1 16 * Fetching and updating EOs from within Scala Actors can cause [[deadlocks>>http://en.wikipedia.org/wiki/Deadlock]] with the WebObjects application
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18 Instead you can still use EOF but in a limited fashion - only to execute SQL.
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Ravi Mendis 73.1 20 === Using EOAccess to execute SQL ===
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Ravi Mendis 141.1 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)]]
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24 ==== Caveats ====
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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.
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28 == EOF Alternatives ==
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30 You may also manipulate the database from outside the EOF stack.
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32 === Squeryl ===
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Ravi Mendis 143.1 34 [[Squeryl>>http://max-l.github.com/Squeryl/index.html]] is a Scala internal [[Domain-specific language>>http://en.wikipedia.org/wiki/Domain-specific_language]] for database access (via SQL).
Ravi Mendis 141.1 35 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.
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37 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.