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From Milen Dyankov <milendyan...@gmail.com>
Subject Re: Discuss: Use DS for karaf bundles
Date Fri, 18 Mar 2016 18:24:58 GMT
This is what I mean:

karaf@root()> bundle:info 44

Apache Karaf :: Shell :: Core (44)

...


karaf@root()> bundle:requirements 44 | grep blueprint
osgi.wiring.package;
(&(osgi.wiring.package=org.apache.aries.blueprint)(version>=1.5.0)(!(version>=2.0.0)))
resolved by:
   osgi.wiring.package; org.apache.aries.blueprint 1.5.0 from
org.apache.aries.blueprint.core [13]
osgi.wiring.package;
(&(osgi.wiring.package=org.apache.aries.blueprint.mutable)(version>=1.2.0)(!(version>=2.0.0)))
resolved by:
   osgi.wiring.package; org.apache.aries.blueprint.mutable 1.2.0 from
org.apache.aries.blueprint.core [13]
osgi.wiring.package;
(&(osgi.wiring.package=org.osgi.service.blueprint)(version>=1.0.0)(!(version>=2.0.0)))
resolved by:
   osgi.wiring.package; org.osgi.service.blueprint 1.0.0 from
org.apache.aries.blueprint.core [13]
osgi.wiring.package;
(&(osgi.wiring.package=org.osgi.service.blueprint.container)(version>=1.0.0)(!(version>=2.0.0)))
resolved by:
   osgi.wiring.package; org.osgi.service.blueprint.container 1.0.1 from
org.apache.aries.blueprint.api [11]
osgi.wiring.package;
(&(osgi.wiring.package=org.osgi.service.blueprint.reflect)(version>=1.0.0)(!(version>=2.0.0)))
resolved by:
   osgi.wiring.package; org.osgi.service.blueprint.reflect 1.0.1 from
org.apache.aries.blueprint.api [11]



On Fri, Mar 18, 2016 at 7:20 PM, Jean-Baptiste Onofré <jb@nanthrax.net>
wrote:

> Hi Milen,
>
> Karaf Shell Core (if you mean this bundle) doesn't depend on blueprint
> (blueprint is not defined as a <dependency/> and so not in the manifest,
> even for the command extender).
>
> Regards
> JB
>
>
> On 03/18/2016 07:14 PM, Milen Dyankov wrote:
>
>> I personally think DS is pretty much what OSGi Alliance is going to
>> promote
>> (together with the enRoute project) and from that perspective if any
>> component framework's user base is going to grow that would be DS. But if
>> you guys want to still do it the "hard way" that's fine too. It just means
>> less people will be able to contribute.
>>
>> As for things that can not be done with DS, I don't think Christian meant
>> to say everything must be rewritten! If something needs to be done
>> differently (activators/tackers/...) than it can/should be. It's not all
>> or
>> nothing scenario IMHO.
>>
>> Finally about Blueprint. I keep reading in posts that Karaf got rid of
>> Blueprint. Meanwhile in 4.0.4 the "Apache Karaf :: Shell :: Core" still
>> depends on Blueprint. So when you say "the bundles in Karaf are
>> independent"
>> what exactly do you mean?
>>
>> Best,
>> Milen
>>
>>
>>
>> On Fri, Mar 18, 2016 at 1:38 PM, Guillaume Nodet <gnodet@apache.org>
>> wrote:
>>
>> I agree with Achim and Lukasz.
>>>
>>> Here are the advantages of the current solution:
>>>
>>> 1/ No additional dependency.  One thing that I really care about is that
>>> the bundles in Karaf are independent.  I.e. they do not rely on an
>>> extender.   The benefit is that you can upgrade the bundles independently
>>> and you don't have an additional bundle which cause all the bundles to be
>>> refreshed / restarted.
>>>
>>> 2/ Very lightweight. The current framework only consist in 3 classes :
>>> BaseActivator, SingleServiceTracker,
>>> SingleServiceTracker$SingleServiceListener.
>>>   Even the annotations are not included at runtime.
>>>
>>> 3/ Very fast. No xml parsing, no reflection.  Just the
>>> OSGI-INF/karaf-tracker/ property file which is loaded by the activator.
>>> So
>>> it's really fast at startup.
>>>
>>> 4/ Very robust. Quite the contrary to what you say, I think this very
>>> small
>>> framework is way more robust than blueprint or DS.  I spent quite some
>>> time
>>> load-testing karaf 4 before the release, using the bundle:load-test
>>> command.
>>>
>>> 5/ DS exclusively uses the OSGi registry for wiring.  There's no notion
>>> of
>>> "internal" wiring, everything is exposed.  So by default, the
>>> capabilities
>>> / requirements contain much more than what is needed, with the additional
>>> semantical change where the bundle could be wired to components coming
>>> from
>>> different bundles (check the bundle manifest in your branch).
>>>
>>> So yes, the main drawback are : limited scope and not documented, but
>>> given
>>> is has never been written to be used outside karaf, I don't see those as
>>> real problems.   If the concern is users, I'm all for advertising the use
>>> of DS or Blueprint for our users, I don't think they should use our
>>> internal framework which is much more low level.
>>>
>>>
>>> 2016-03-17 16:43 GMT+01:00 Christian Schneider <chris@die-schneider.net
>>> >:
>>>
>>> We currently use some custom Activator base classes to wire the karaf
>>>> bundles. The goal of this was to avoid depending on blueprint
>>>> as it is a quite heavy dependency and makes it harder to use a different
>>>> blueprint impl or version.
>>>>
>>>> There are some problems with this approach though:
>>>> - It makes it harder for new people to understand what we are doing
>>>> - The custom code is more error prone than a proven framework
>>>>
>>>> So I propose to switch our own bundles to use DS to expose and wire
>>>> services.
>>>>
>>>> There are some advantages:
>>>> - The DS annotation approach is easier to understand and more self
>>>> documenting than the custom code
>>>> - We get rid of the classes in util for the custom code
>>>> - The scr commands help diagnose problems
>>>>
>>>> The main cost is that we need to always install the felix scr bundle.
>>>>
>>>> To prove that it can work I switched bundle core in a branch
>>>> https://github.com/apache/karaf/tree/EXPERIMENTAL_DS .
>>>> The DS based code works quite nicely.
>>>>
>>>> Btw. I found a small problem with our shell command extender. It only
>>>> seems to work on all commands or none. If there is any required service
>>>> missing then none of the commands is installed.
>>>> This made it hard for me to diagnose problems as I was missing all
>>>> bundle
>>>> commands ;-)
>>>> So while working on the switch I thought about two improvements to the
>>>> extender:
>>>> 1. Work on each command individually. So each command can activate as
>>>>
>>> soon
>>>
>>>> as the deps are met
>>>> 2. Provide a service and commands to diagnose problems like the scr
>>>> commands
>>>>
>>>> Christian
>>>>
>>>> --
>>>> Christian Schneider
>>>> http://www.liquid-reality.de
>>>>
>>>> Open Source Architect
>>>> http://www.talend.com
>>>>
>>>>
>>>>
>>>
>>> --
>>> ------------------------
>>> Guillaume Nodet
>>> ------------------------
>>> Red Hat, Open Source Integration
>>>
>>> Email: gnodet@redhat.com
>>> Web: http://fusesource.com
>>> Blog: http://gnodet.blogspot.com/
>>>
>>>
>>
>>
>>
> --
> Jean-Baptiste Onofré
> jbonofre@apache.org
> http://blog.nanthrax.net
> Talend - http://www.talend.com
>



-- 
http://about.me/milen

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