So if you consider an OBR as being a collection of resources, each resource having capabilities and requirements, then a feature repository is an OBR repository, it's just the syntax is more concise. If you want to look at what the repository look like, you can launch the following command in karaf: > feature:install --store resolution.json --verbose --simulate scr
Then, look at the resolution.json file, it will contain the OBR repository used by the resolver in a json format. The xml syntax would be slightly different of course, and a bit more verbose too, but roughly the same data. I do think the features syntax is a bit more understandable. But you do not want to compare OBR and features. I haven't seen any OBR repository used which would contain other things than just OSGi bundles. Features is more a deployment artifact than an OSGi bundle, so it's more to be compared with OSGi subsystems. With pure OBR, you can't group bundles together, you usually don't want to edit such a repository file manually, so at the end, you can never really hack the content. It has to be generated, and is mostly generated only from a set of OSGi bundles. You can't capture all the constraints by using bundles only. 2017-06-14 7:49 GMT+02:00 David Leangen <[email protected]>: > > Hi! > > I am trying to wrap my head around the differences between an OBR and a > Karaf Feature. The concepts seem to be overlapping. > > An OBR has an index of the contained bundles, as well as meta information, > which includes requirements and capabilities. An OBR is therefore very > useful for resolving bundles, and partitioning bundles into some kind of > category. It can also be versioned, and can contained different versions of > bundles. An OBR could potentially be used to keep snapshots of system > releases. I believe that this is somewhat how Apache ACE works. (A > Distribution can be rolled back by simply referring to a different OBR and > allowing the system to re-resolve.) The actual bundles need to be stored > somewhere. The OBR index needs to provide links to that storage. > > A Karaf Feature is basically an index of bundles (and configurations), > too. I think that it can also be versioned, and can contain different > versions of bundles. Like an OBR, it is very useful for partitioning > bundles into some kind of category, so the groups of bundles can be > manipulated as a single unit. Just like an OBR, the Karaf Feature also > needs to provide a link to the bundles. AFAIU, resolution is done somehow > in Karaf, based on the bundles available via the Features, so in the end > the entire mechanism seems almost identical to what the OBR is doing. > > > So many similarities! > > > I understand that a Feature can include configurations, which is nice, but > why have a competing non-official standard against an official standard? If > configurations is the only problem, then why not build it on top of OBRs, > rather than creating something completely new and different and competing? > > Is it to try to force lock-in to Karaf? Or am I completely missing > something? > > > Thanks for explaining! :-) > > > Cheers, > =David > > > -- ------------------------ Guillaume Nodet
