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From: Geoff Macartney <geoff.macartney@cloudsoftcorp.com>
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Subject: Re: [PROPOSAL] Class loading fallback in Karaf
Date: Tue, 5 Jul 2016 14:30:24 +0100
References: <2E942F22-058C-4ED1-AF3A-A61A70E060E6@cloudsoftcorp.com>
To: dev@brooklyn.apache.org
In-Reply-To: <2E942F22-058C-4ED1-AF3A-A61A70E060E6@cloudsoftcorp.com>
archived-at: Tue, 05 Jul 2016 13:30:39 -0000

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+ 1 both for the longer term plan and the short term proposal


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Gnu PGP key - http://is.gd/TTTTuI


> On 5 Jul 2016, at 13:56, Svetoslav Neykov =
<svetoslav.neykov@cloudsoftcorp.com> wrote:
>=20
> Brooklyn has a number of places where it will try to load a class by =
name. It's either using Class.forName(..) or at best =
mgmt.getCatalogClassLoader().loadClass(...). This is highly likely to =
fail when run in Karaf.
> Some examples of this behaviour:
>  * configuring entitlements implementation in brooklyn.properties (or =
configuring any other class name for that matter)
>  * initializers/enrichers in yaml
>  * objects passed as config keys/sensors to an entity, with the entity =
not knowing how to load the classes - can't rebind. For example Brooklyn =
DSL deferred objects / SpecialFlagsTransformer passed as config
>  * PolicyResource trying to attach a policy by class name
>=20
> Longer term we should introduce bundle knowledge in all of those =
places. There are various ways to do that - ether by explicitly passing =
bundle symbolycName + version, loading through a catalog item or another =
OSGi mechanism altogether.
> Shorter term I suggest we go for the following workaround, giving us =
time to introduce proper OSGi behaviour for each of the the above cases:
>  * Pull the class loading logic in a single place. Same as =
ResourceUtils, but for classes.
>  * Support bundle symbolic name + version embedded in the class name - =
for example =
org.apache.brooklyn.policy:0.10.0.SNAPSHOT:org.apache.brooklyn.policy.ha.S=
erviceFailureDetector. That will allow us to use the existing code paths =
to pass classes, but be able to resolve them.
>  * Fall back to a white list of bundles to scan for the class name. =
For example "org.apache.brooklyn.*:0.10.0.SNAPSHOT". This will help in =
parsing existing yaml plans, using stock enrichers, rebinding.
>=20
> Svet.


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