karaf-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Timothy Ward <tim.w...@paremus.com>
Subject Re: What's the recommended way of reading configuration?
Date Sun, 03 Dec 2017 15:36:49 GMT
> I didn’t mean ManagedService using DS, I meant using DS configuration (which is basically
a managed service.

Ok - but you can see the source of confusion right? Your post does not reference DS at all,
and ManagedService is an interface defined by ConfigurationAdmin. If someone looks up ManagedService
on Google then they won’d find the DS solution.

> I disagree about @Referece to ConfigurationAdmin: in some use cases, it makes sense.
Look in Karaf Cellar for instance.

I have taken a look - in most of the cases here Cellar is acting as a management agent (which
I explicitly mentioned in my first post) and is making configuration updates on behalf of
other people, or synchronising configurations, not getting its own configuration. In some
other cases it appears as though the code could be simplified and improved by not using ConfigurationAdmin
to retrieve its own configuration, but I’m not a cellar expert, and it’s possible that
these components are still acting on other bundle’s configurations not their own. The main
thing is not to confuse middleware/infrastructure with application code. The number of people
who are writing things like Cellar is very small, and the OSGi advice/best practice is pretty
clear that using ConfigurationAdmin to get your own configuration is an anti-pattern.

Regards,

Tim



> On 3 Dec 2017, at 13:55, Jean-Baptiste Onofré <jb@nanthrax.net> wrote:
> 
> I didn't mean ManagedService using DS, I meant using DS configuration (which is basically
a managed service.
> 
> When using @Component, we implicitly have a configuration link to the component injected
via activate and the ComponentContext (getProperties).
> 
> I disagree about @Referece to ConfigurationAdmin: in some use cases, it makes sense.
Look in Karaf Cellar for instance.
> 
> Regards
> JB
> 
> On 12/03/2017 01:10 PM, Timothy Ward wrote:
>>> I would more recommend a ManagedService or inject the ConfigAdmin service.
>> This is really bad advice, and Steinar should definitely not do either of these things
(nor should other readers of this mail chain).
>>  * Steinar has already indicated that he wants to use Declarative Services, so
>>    implementing ManagedService is both unnecessary and ties him to an API that
>>    he has no need to implement. It also prevents him from using Component
>>    Property Types, defaults, annotations, and forces him to use Dictionary for
>>    his configuration. Finally, it also makes his component’s lifecycle
>>    management harder, as he would have to manage all the reconfiguration
>>    dynamics himself.
>>  * Injecting the Config Admin service is inevitably the wrong way for any user
>>    to read configuration in OSGi. The only people who should ever access the
>>    ConfigurationAdmin service directly are management agents like Felix File
>>    Install and Felix Web Console (and whatever component in Karaf does the same
>>    job).
>> The correct way to consume configuration in DS is to receive it via your activate
method - if you think that you need to do something else then you have most likely got the
wrong design.
>> If you’re not using DS then most component frameworks still provide you with configuration
in a similar way (injection of a map). If you’re determined to do things the hard way (without
a framework) then, and only then, should you implement ManagedService or ManagedServiceFactory,
and you should absolutely never try to consume your configuration directly from the Configuration
Admin service (it’s simply not designed to be used this way).
>> Regards,
>> Tim
>>> On 3 Dec 2017, at 10:41, Jean-Baptiste Onofré <jb@nanthrax.net <mailto:jb@nanthrax.net>
<mailto:jb@nanthrax.net <mailto:jb@nanthrax.net>>> wrote:
>>> 
>>> I would more recommend a ManagedService or inject the ConfigAdmin service.
>>> 
>>> Regards
>>> JB
>>> 
>>> On 12/03/2017 09:41 AM, Steinar Bang wrote:
>>>> What's the recommended way for an OSGi bundle running inside karaf to
>>>> access its configuration?
>>>> Get an OSGi service of type ConfigMBean[1]?
>>>> Get an OSGi servie of type ConfigRepository[2]?
>>>> Or maybe avoid karaf dependencies, and get an OSGi service of type
>>>> ConfigurationAdmin[3]...?
>>>> Does anyone know of code examples of any of the three approaches?
>>>> Preferrably DS w/annotation based code examples?
>>>> Thanks!
>>>> - Steinar
>>>> References:
>>>> [1] <https://github.com/apache/karaf/blob/master/config/src/main/java/org/apache/karaf/config/core/ConfigMBean.java>
>>>> [2] <https://github.com/apache/karaf/blob/master/config/src/main/java/org/apache/karaf/config/core/ConfigRepository.java>
>>>> [3] <https://osgi.org/javadoc/r4v42/org/osgi/service/cm/ConfigurationAdmin.html>
>>> 
>>> -- 
>>> Jean-Baptiste Onofré
>>> jbonofre@apache.org <mailto:jbonofre@apache.org> <mailto:jbonofre@apache.org
<mailto:jbonofre@apache.org>>
>>> http://blog.nanthrax.net <http://blog.nanthrax.net/>
>>> Talend - http://www.talend.com <http://www.talend.com/>
> 
> -- 
> Jean-Baptiste Onofré
> jbonofre@apache.org <mailto:jbonofre@apache.org>
> http://blog.nanthrax.net <http://blog.nanthrax.net/>
> Talend - http://www.talend.com <http://www.talend.com/>

Mime
View raw message