[rules-dev] Issue with ResourceChangeScanner

[Steve Ronderos]

Michael,

In this exact case I am not expecting the scanner to ever find an updated 
resource; however, the changeset is configured to read one resource from a 
URL and another from the classpath.  The resource from the URL is expected 
to change, but the one from the classpath is not.  We have a use case 
where we may need classpath resources to be scanned, but I'm not sure it 
will ever come up. 

Unfortunately I don't think that we can reference that resource any way 
other than the classpath at this moment, but we do have another 
workaround.  Previous to Drools 5 we had a custom way of refreshing our 
resources which I think we will go back to for now. 

Should I log a feature request for this change?

Steve Ronderos

rules-dev-bounces at lists.jboss.org wrote on 10/07/2009 05:29:56 PM:

> [image removed] 
> 
> Re: [rules-dev] Issue with ResourceChangeScanner
> 
> Michael Neale 
> 
> to:
> 
> Rules Dev List
> 
> 10/07/2009 05:31 PM
> 
> Sent by:
> 
> rules-dev-bounces at lists.jboss.org
> 
> Please respond to Rules Dev List
> 
> Hi Steve - I have seen that issue before reported by others. But you
> just explained the cause ! - I don't often use the classpath scanner
> myself, so never thought of that.
> 
> Yes the lastModified being zero is a problem...
> 
> OK, well I think perhaps the solution would be if lastModified is not
> a valid value, to NOT use that to decide availablility.
> 
> I think using a scanner on  a classpath resource is a bit unusual to
> start with, but it is possible in various containers to dynamically
> change the classpath, so it kind of technically makes sense.
> 
> If I had things in the classpath, I would assume they are constant -
> but I assume you are actually expecting the scan to pick up changes in
> a future ?
> 
> (in the meantime, if you can avoid the classpath one that problem
> should go away).
> 
> On Thu, Oct 8, 2009 at 5:53 AM, Steve Ronderos <steve.ronderos at ni.com> 
wrote:
> >
> > Hello Dev List,
> >
> > I encountered an issue today with my KnowledgeAgent removing resources 
from
> > its RuleBase shortly after creating it.  I have the 
ResourceChangeScanner
> > running in my application.
> >
> > I tracked the issue back to the scan() method in 
ResourceChangeScannerImpl.
> >  It appears that the method is trying to identify resources that are 
no
> > longer available and remove them from both the RuleBase and future 
scans.
> >  To do this it is checking lastModified on the resource and on a 
result of 0
> > removing the resource.  The resources that I configured in my 
change-set
> > definitely still exist, but due to URL handler implementation provided 
by my
> > classloader, getLastModified always returns 0.  (The resource I'm 
retrieving
> > is coming from a jar that is in my application's classpath and the URL
> > handler implementation is oracle.classloader.SharedCodeSourceURL)
> >
> > Do you think it would be possible for the scan to identify unavailable
> > resources some other way than with the lastModified? and then if
> > lastModified is 0 maybe always or never update the resource? I'm not 
sure
> > what the best approach to that would be, but removing resources when 
their
> > lastModified is 0 seems incorrect to me.
> >
> > Thanks,
> >
> > Steve Ronderos
> > _______________________________________________
> > rules-dev mailing list
> > rules-dev at lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/rules-dev
> >
> >
> 
> 
> 
> -- 
> Michael D Neale
> home: www.michaelneale.net
> blog: michaelneale.blogspot.com
> 
> _______________________________________________
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> rules-dev at lists.jboss.org
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