Hi all,
Thanks for the feedback. Sorry that I didn't formulate my question
precise enough.
I got things working with a separate class that implements the
ManagedService which only gets used if the class is there available
(optional cm import).
The main question I'm still a little struggeling with is: how long do I
wait. As Per says, if the CA service is present I will get called with
updated() no matter what. But how long do I wait before deciding that
the CA service is not present? Especially during startup this could
depend on the bundle ordering and considering the machine capabilities
and the number of bundles this could take either a long time or a fairly
short amount of time. I'm not particularly a fan of arbitrary timeouts
so I was thinking is there some other mechanism? I also don't want to
use the defaults if typically in the next second the real values become
available...
Maybe something like this:
* every second look at all the installed bundles
(BundleContext.getBundles())
* if this information doesn't change (no extra bundles and all the
bundles remain in their previous state) assume that the system has
started up
* now check whether the CA service is there, if not use the defaults...
Or would using the StartLevel service be an alternative? Or does that
merely move the problem?
David
Per Gustafson wrote:
I think the general approach BJ describes is good. But in case (2) the
MS will get called with a null dictionary (see 104.5.3 of the
Compendium spec) so you don't have to bother with a timeout.
/Per
On Nov 13, 2009, at 08:36 AM, BJ Hargrave wrote:
I think your question is: How long do I wait for my ManagedService to
be called with my configuration before I decide I need to use some
defaults?
There are 2 reasons why your MS may not get called. (1) There is no
ConfigAdmin running (yet). (2) Your MS does not have a configuration.
(1) Can be detected because there is no ConfigAdmin service
registered. If this is the case, use your defaults but still register
the MS because the ConfigAdmin service may get started shortly.
(2) If there is a ConfigAdmin service, then you may want some timeout
before you give up waiting for some configuration and using your
defaults. In this case still leave your MS registered.
In all cases, register the MS and respond to update.
--
BJ Hargrave
Senior Technical Staff Member, IBM
OSGi Fellow and CTO of the OSGi Alliance
[email protected]
office: +1 386 848 1781
mobile: +1 386 848 3788
From:
David Bosschaert <[email protected]>
To:
OSGi Developer Mail List <[email protected]>
Date:
2009/11/12 23:22
Subject:
[osgi-dev] How to reliably detect that Configuration Admin is
*not* present?
Sent by:
[email protected]
Hi all,
I have a bundle that can be configured through Configuration Admin.
However when CA is *not* present it can still function using default
behaviour.
Question 1: What would be the best way to let it check that the
Configuration Admin service is not present, so that it can proceed with
its default behaviour?
Question 2: I would really like it to have an *optional* dependency on
org.osgi.service.cm. but still my code provides a class that implements
org.osgi.service.cm.ManagedService I guess this should be possible,
right? I was thinking of the following algorithm:
If Not Config Admin Present then
default behaviour
else
register MyManagedService // only at this point the ManagedService
class gets loaded
... handle configuration as soon as updated() gets called.
Is this a feasible approach?
Thanks,
David
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