So why do we recommend initialize the runners in a singleton object and
having custom logic to clean them up when the test finishes? Why not
just put them in the class and let them be cleaned up by the GC when the
test finishes?

On 10/7/20 6:11 PM, Beckerle, Mike wrote:
> The Runner objects are normally members of a scala singleton object. That way 
> they are constructed once and shared by all the tests.
> 
> My understanding is once a singleton object is required, it is constructed, 
> and then never goes away for the life of the JVM (actually the class loader, 
> but those aren't released typically either, so life of the JVM) (per 
> https://stackoverflow.com/questions/3956652/when-are-scala-objects-garbage-collected)
> 
> So as Runners are usually val or lazy val of these singletons, they will 
> never go out of scope.
> 
> 
> 
> 
> 
> 
> 
> 
> ________________________________
> From: Carlson, Ian <icarl...@owlcyberdefense.com>
> Sent: Wednesday, October 7, 2020 5:51 PM
> To: dev@daffodil.apache.org <dev@daffodil.apache.org>
> Subject: RE: Daffodil-1300
> 
> 
> A conversation with Steve Lawrence, and digging deeper into the ThreadLocal 
> aspect of the Runner and DFDLTestSuite objects has called into question 
> whether the shutdown routines are still needed or not. My understanding is 
> that Scala is a garbage collected language, and should dump objects and 
> classes which are no longer in use – so long as references to them are not 
> being held by still-existing objects.
> 
> 
> 
> The shutdown routine called by the Runner class simply invokes 
> ts_ts.set(null), where tl_ts is of type ThreadLocal[DFDLTestSuite]. 
> Presumably this removes the reference to the DFDLTestSuite and allows it to 
> be garbage collected, but in current cases, the Runner  containing the 
> DFDLTestSuite will simply go out of scope once the block of tests is 
> completed.
> 
> 
> 
> The Runner objects are constructed as lazy val types, so it is my expectation 
> that they will be constructed only when used – as in the TresysTests.scala 
> file – lines 108-181 – and then be released at the end of that scope.
> 
> 
> 
> So is the invocation of .set(null) on the ThreadLocal[DFDLTestSuite] objects 
> still actually necessary?
> 
> 
> 
> [A picture containing object, clock  Description automatically generated]     
>      Ian Carlson | Software Engineer
> 
> [Owl Cyber Defense]
> 
> W  icarl...@owlcyberdefense.com<https://owlcyberdefense.com/>
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> 
> From: Beckerle, Mike<mailto:mbecke...@owlcyberdefense.com>
> Sent: Thursday, October 1, 2020 4:03 PM
> To: dev@daffodil.apache.org<mailto:dev@daffodil.apache.org>
> Subject: Re: Daffodil-1300
> 
> 
> 
> I think the DFDLTestSuite constructor can't stay deprecated. We still need to 
> construct them.
> 
> It can become package private I think, so not usable outside the package.  I 
> think the scala syntax for that is:
> 
> class Foo private[pkgName] (arg1: Type1, arg2: Type2) { ...
> }
> 
> The deprecation was just to help in hunting down the usages.
> 
> If we need more Runner functions that's ok. But probably we can just depend 
> on Scala's ability to pass arguments by specifying the argument names 
> explicitly and getting defaults for the rest.  I think calls to Runner 
> already do this in many cases.
> 
> 
> 
> 
> 
> ________________________________
> From: Carlson, Ian <icarl...@owlcyberdefense.com>
> Sent: Thursday, October 1, 2020 4:14 PM
> To: dev@daffodil.apache.org <dev@daffodil.apache.org>
> Subject: Daffodil-1300
> 
> 
> Regarding DAFFODIL-1300, I’m hunting down usage of “new DFDLTestSuite” and 
> replacing them with usage of the “Runner” object. In order to help identify 
> where the DFDLTestSuite was being invoked, I un-commented:
> 
> 
> 
> daffodil-tdml-lib/src/main/scala/org/apache/daffodil/tdml/TDMLRunner.scala 
> line 198
> 
> @deprecated("2016-12-30", "Use Runner(...) instead."
> 
> 
> 
> This revealed that the Runner object itself invokes “new DFDLTestSuite” when 
> the runOneTest function is called. This seems to defeat the purpose of this 
> task. I’m hoping for some guidance or opinions on when, if ever, it’s 
> appropriate to invoke the DFDLTestSuite constructor.
> 
> 
> 
> Related to this – I believe I’ll need to create more constructors for the 
> Runner object in order to preserve the argument combinations currently 
> invoked by some of the new DFDLTestSuite calls – in particular when 
> compileAllTopLevel must be provided as true when paired with an xml node 
> instead of a file name.
> 
> 
> 
> Is deprecating the DFDLTestSuite constructor still appropriate, or since this 
> ticket was written have we changed or strategy such that it shouldn’t be 
> called directly, but will need to be used by the Runner object?
> 
> 
> 
> [A picture containing object, clock  Description automatically generated]     
>      Ian Carlson | Software Engineer
> 
> [Owl Cyber Defense]
> 
> W  icarl...@owlcyberdefense.com<https://owlcyberdefense.com/>
> 
> Connect with us!
> 
> Facebook<https://www.facebook.com/owlcyberdefense/> | 
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> 
> The information contained in this transmission is for the personal and 
> confidential use of the individual or entity to which it is addressed.
> 
> If the reader is not the intended recipient, you are hereby notified that any 
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