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From "John Ross (JIRA)" <>
Subject [jira] [Commented] (ARIES-952) Break dependency of Aries Subsystems on Aries Blueprint
Date Mon, 01 Jul 2013 17:24:23 GMT


John Ross commented on ARIES-952:


Right, I just wanted to get a sense of where "gembin" was at. I still think the original requirement
deserves attention but it's quite a bit more work, from both a design and implementation perspective.
I think the latter could be addressed quickly by simply making the dependency on ApplicationModeller
optional. You would lose service dependency resolution at subsystem install time, of course.
But since that requires Blueprint anyway, it makes no difference to someone without any blueprint.xml.

For the former, I see the following options.

(1) Have Subsystems use the application-modeller-standalone distribution (if possible). This
removes the Blueprint implementation dependency.

(2) Have Subsystems use the blueprint-parser standalone distribution (if possible). This removes
the Blueprint implementation dependency but would require abandoning the modeller and going
to the parser directly. This isn't necessarily bad since Subsystems only needs the service
dependency info from the modeller. The rest (e.g., package, bundle, host, and generic requirements/capabilities)
it calculates itself. This eliminates the possibility of eventually integrating fully with
the modeller, however.

Both (1) and (2) allow for the possibility of using Blueprint implementations other then Aries;
however, I'm not sure if the Aries Blueprint Parser was written for standard blueprint xml
or requires certain Aries specific constructs.

(3) Define a service that Subsystems would use to get the service capabilities and requirements
of not-yet-installed bundles. The core subsystems implementation would have an optional dependency
on these services. Any present in the registry would be used to compute service capabilities
and requirements for subsystem resolution. This would make integration with other blueprint
providers straightforward, as well as additional service technologies such DS.
> Break dependency of Aries Subsystems on Aries Blueprint
> -------------------------------------------------------
>                 Key: ARIES-952
>                 URL:
>             Project: Aries
>          Issue Type: Improvement
>          Components: Application, Subsystem
>            Reporter: Glyn Normington
> Aries Subsystems currently has a hard dependency on Aries Blueprint (AB).
> When running Aries Subsystems in an environment where there is already a Blueprint implementation,
we end up with duplicate Blueprint extenders, which is of course a recipe for disaster.
> One such environment is the Virgo kernel. Virgo depends on Gemini Blueprint (GB) because
it uses the Spring DM function provided by GB. So it's not possible to substitute AB for GB.
> So the requirement is to make it possible to run Aries Subsystems with GB. Admittedly
this may involve adding some GB code to support resource modelling for Blueprint, but that
should be separated from the AB implementation.
> To reproduce the problematic environment, see
and follow the instructions in The web admin console can then be used to observe
both GB and AB extenders running in the Virgo user region. Also, the nature of the hard dependency
can be observed by deleting the Aries Blueprint core bundle from the Virgo kernel's repository/usr
directory and restarting Virgo - the modeller no longer resolves:
> missing constraint in bundle <org.apache.aries.application.modeller_1.0.1.SNAPSHOT>
>              constraint: <Import-Package:;

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