Thanks Guillaume. A lot of good food for thought. > Again, I'm not sure why you see features competing with OBR.
Coming from bnd/EnRoute, in my build environment I can create different OBRs, and “release" to them. I can use a different OBR per workspace, which means that I can develop each “feature" separately, and release it to its own OBR. Thus, an OBR defines a “feature”. What I would like to be able to do is simply push the OBR into my container, without having any extra layer. When I tried in the past, there were some bugs and it did not work out very successfully. Maybe things have changed since then… Using Apache ACE as an example, an OBR can be used in a way that is very similar to a Feature. It works extremely well in the EnRoute environment, and cuts down a lot of noise, IMO. > A feature descriptor supports the <resource-repository> element. The content > of this element is an url to a OBR repository (eventually prefixed with json: > or xml:). All features defined in the features repository will behave as if > they have the resources defined in the OBR repository with <bundle > dependency="true">xxx</bundle>. Ok, either I did not know that, or I forgot about that. I’ll take a look. IIRC I think this is what didn’t work for me when I tried some time ago. > You can also provide a list of global repositories and configure it in > etc/org.apache.karaf.features.cfg with the resourceRepositories key (a > command separated list of urls). The problem with this approach is, unless something has changed, I have to restart my container each time there is a change. I would also have to figure out a way to push the changes to Karaf. Perhaps this is easier than I thought, but I did not find a good way last time I look into this. > Also, there's absolutely no value in the OBR bundle description compared to a > manifest. It contains the same information in a different form and is > usually generated from the manifest. Fwiw, when a feature has a reference to > a bundle, we do generate the OSGi Resource from the manifest directly without > using the OBR xml description, but it's the same. True, but then again my understanding is that a properly curated OBR should provide a set of bundles, and should not change (which is why the ID gets updated each time there is even a minor change). The information could very well come from the bundles, but if the bundles don’t change and the index is trusted, then the pre-parsed manifest info is already in the index, so it’s a duplicate effort to redo the parsing. No? Perhaps the Karaf/Maven way of thinking is very different from the bnd way? Or maybe there has been convergence over the past few years, but the tooling has not kept up? (That is what I am trying to figure out, since I don’t know Maven very deeply, and based on what I understand, I think I prefer the bnd way.) Cheers, =David > On Jun 15, 2017, at 3:27 PM, Guillaume Nodet <[email protected]> wrote: > > Again, I'm not sure why you see features competing with OBR. > We do actually leverage OBR internally, and we can also leverage it > externally though it's not much advertised, but it was hinted by > Jean-Baptiste when he talked about Cave. > > OBR is the repository specification, so it defines a Repository interface. > We do have multiple implementations of it in Karaf : the standardized XML > one, a JSON based repository implementation and an in-vm one. > > A feature descriptor supports the <resource-repository> element. The content > of this element is an url to a OBR repository (eventually prefixed with json: > or xml:). All features defined in the features repository will behave as if > they have the resources defined in the OBR repository with <bundle > dependency="true">xxx</bundle>. > > You can also provide a list of global repositories and configure it in > etc/org.apache.karaf.features.cfg with the resourceRepositories key (a > command separated list of urls). > > Also, there's absolutely no value in the OBR bundle description compared to a > manifest. It contains the same information in a different form and is > usually generated from the manifest. Fwiw, when a feature has a reference to > a bundle, we do generate the OSGi Resource from the manifest directly without > using the OBR xml description, but it's the same. > > I'm really not sure what we could do to leverage OBR more... > > > 2017-06-14 23:58 GMT+02:00 David Leangen <[email protected] > <mailto:[email protected]>>: > > Hi Guillaume, > > Thank you for this assessment. > > I agree that Features adds value. Your post explains a lot of good reasons > why this is so. > > My question is more about “why compete with OBR?”. Instead of embracing OBR > and working on top of it, it seems that Features want to replace it. This is > causing me to have to make a lot of choices in my deployment mechanism. > > Features could be really helpful for deployment by managing OBRs, > configurations, and other deployment information. They could also manage > versioning better etc. Maybe something like what Apache ACE was trying to do. > However, instead of “adding” value, currently Features are completely > replacing OBR, which I find interesting. But I understand that there is some > legacy to this. Now that it works, it would take some momentum to move to a > more standards-based approach. > > > My current issue is: how can I use Features for Continuous Deployment? I am > having trouble with automation. That is what got me interested in the idea > behind the Features… > > > Cheers, > =David > > > >> On Jun 15, 2017, at 6:38 AM, Guillaume Nodet <[email protected] >> <mailto:[email protected]>> wrote: >> >> 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] >> <mailto:[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 >> > > > > > -- > ------------------------ > Guillaume Nodet >
