hi Alex,
In general I think this is a good direction to go in, some questions and
thoughts below.
One concern is whether we are "leaking" an implementation detail (the fact
that we
use an OSGI runtime) into the specification of what Brooklyn is. I think
it is good to
aim for the improved modularity of having a bundle of catalog definitions
and related
resources, all at a given version and added or removed as a unit. I'm less
sure we
want to advertise that all Brooklyn definitions must be contained in OSGI
bundles,
even if we will wrap them for you. This seems to impose an additional
requirement
on blueprint authors (learn OSGI) that we don't really want to impose?
As an aside, I'm assuming that your proposal would rely on Brooklyn moving
exclusively to the Karaf launcher, is that the case?
Specific notes inline below.
Geoff
On Mon, 19 Jun 2017 at 17:39 Alex Heneveld <[email protected]>
wrote:
Hi All-
With bundles now being neatly supported for add and remove, I think it
makes sense to use make the "bundle" a first-class concept in managing a
brooklyn catalog (type registry).
The basic idea is that users will work with ZIPs (or directories if
using the br CLI), where a "catalog.bom" is in the root; this is a
bundle, and operations like add/remove/update apply to the bundle.
Increasingly people are doing this for additions, so it seems pretty
obvious that delete should follow suit, and something like a "/bundles"
REST endpoint is appropriate.
I do like this; as part of this we should re-instate the automatic scanning
of bundles for catalog.bom (feature FEATURE_LOAD_BUNDLE_CATALOG_BOM).
Now that catalog items can tell you their containing bundle
(getContainingBundle())
it should be possible to make this work with rebind.
You can still upload just a catalog.bom file; in this proposal it will
be wrapped in a bundle (internally, hidden from user). A bundle name
and version will have to be inferred/guessed for backwards
compatibility, and probably we should deprecate supplying a BOM which
doesn't define a bundle name and version.
+1
If a ZIP/folder is supplied, it doesn't have to contain any OSGi bundle
definition; that call all be inferred. If a MANIFEST.MF is supplied,
any bundle name/version given there must of course match that in the
catalog.bom file.
If dependent bundles are declared, they are obeyed at
runtime and can be used to find things (pretty much identically to how
we treat "libraries" in the catalog.bom.)
Not so sure about that last paragraph - again this is related to leaking
the use
of OSGI. This would allow someone to write a catalog.bom that would ONLY
work when supplied along with a related manifest (to specify certain
dependencies
and so set up the search paths). Do we want to allow that, or should all
definitions
required for entities in a catalog be supplied in the catalog.bom (or its
included
catalog definitions).
* Search Paths - Bundles fix an issue where types have implicit version
dependencies. Consider an "acme-cluster" of "acme-node" entities,
defined in a bundle. If I release a 1.0 version of this, and then a 2.0
version, I'd probably expect the 1.0 acme-cluster to load 1.0 acme-node
entities, and same for 2.0. But currently any reference to "acme-node"
takes the latest version, even if there is a different version in the
same bundle. Shifting to bundles, I think we should change this, so
that versions of items in the same bundle (or on the OSGi or library
search path for that bundle) are preferred over more recent versions in
the repository.
+1 this sounds like a better match to what blueprint authors intend
(And since we will follow OSGi loading, we can also, if
we need to, use OSGi config to say that "acme" bundle requires a given
version _range_ for some other bundle, to have more control over
dependency versions when required.)
again, how "use OSGI config" - there may be value in specifying ranges but
we wouldn't want users to have to use OSGI declarations to achieve it.
For most users and blueprints this will cause no changes. However there
are some changes to note:
* If people have been sloppy with versions or metadata, in most cases
they will get a warning
* In some cases if uploading a ZIP, the catalog.bom may need to be
edited (the upload will give a clear error, and it should not expect
rebind)
* When a type is referenced with no version, the loading semantics may
change if that type is in the same bundle (this is probably what the
user expects)
Does anyone oppose any of the above, or have further questions?
Best
Alex
[1] https://github.com/apache/brooklyn-server/pull/672
