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From Frank_S <frank.sjeg...@ikan.be>
Subject Re: Problems after removing a feature repository in Karaf 4.0
Date Mon, 12 Dec 2016 16:14:12 GMT
The features are installed programmatically, by a separate "installer"
bundle. The karaf feature repo file is generated and saved in the persistent
storage area of that installer bundle. 
In our application, it's possible that a bundle with the same name and
version, but with different content gets re-installed. Currently, this is
not a problem, since we find the bundle, uninstall it, and re-install it
using feature:install and a “disposable” feature repository.

If we can't remove the feature repo, then if we need to reinstall a bundle,
we need to find the feature repo that was used to install it, and remove
that repo. If we wouldn't, then we would have 2 feature repos which contain
the same feature, which doesn't seem like a good idea. While this is not
impossible, it's more complicated than our current solution.

The point is that we don't really “need” a persistent feature repository, we
can easily regenerate the feature repository file when we need to reinstall
a bundle. A system that can regenerate data is usually simpler than a system
that needs to keep track of that data, making sure it stays in synch, is
backed up, doesn't get removed etc...

Using Karaf features to install bundles is very convenient for us. We have
URLStreamHandlers in place to handle file:, ftp:, and scp: protocols, which
means we can easily install bundles from remote locations.

The bundles that need to be installed are very light-weight, they are not
much more than a wrapper around an Ant script, with a blueprint descriptor
that registers it as an OSGi service. This allows us to run a reusable,
versioned Ant script on a remote system.While this Ant script is in
development, it will be repackaged into a bundle and redeployed to the
remote systems. Hence the need to re-install a bundle with the same name and
version.

I can see the need for tighter rules on features, certainly for
consistency’s sake, but we were happier with the more “relaxed” approach. I
don't have enough knowledge of Karaf or OSGi to propose a solution, but I
hope to make the case to allow less strict rules in certain cases.

Thank you very much for your swift reply,
Frank 'S Jegers.




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