Niclas Hedhman wrote:
On Sunday 02 October 2005 00:40, Daniel Fagerstrom wrote:
The metatype service in R4 is schema driven like the Knopflerfish one,
don't know if there are any open source implementations yet.
Ok. Then I need to take a look at that.
For server use it is impractical with interactive parameter
modification. Here we could develop a configuration file driven
configuration service implementation. That either use a large
configuration file that configures everything in the app or a set of
configuration snippets, for making configuration less monolithic.
This is an area I am struggling with conviction at the moment.
OSGi is built on the premise that a platform restart will bring back the last
"known state", including the Configuration set for a ManagedService.
The key issue is the form of the "known state". If it is in some obscure
binary format, I wouldn't trust it for my interactvely added data. If it
instead was in some explicit and readable form, like XML. Then I might
belive that I could restart the framework from an inconsistent state
after having tweaked the state description, or after having resumed an
earlier one from backup.
I think this is an important point for the Felix project to find a way
to handle persistance that we can use in enterprise systems.
If I dared to make this a reality, the interactive config actually makes
sense;
1. The ManagedService exposes its expected configuration in its registration,
by publishing the defaults for everything.
2. The Config service manages the persistence.
3. One or many Config Admin services can be created to modify the
configuration in runtime, and the Config service will track it correctly.
I guess a "Export" functionality in the Config Admin service would be needed
to allow to restore the configuration after a real "cold start" (removal of
OSGi cache directories).
Exactly!
I am just not comfortable at the moment to let OSGi start from 'previously
known state'... Guess I don't have faith in my own bundles. :o)
Neither have I, yet. And if I had to put faith in that all third party
bundles are good citisens as well for being able to restart the system,
it rather shows that the mechanism is to fragile. So we need explicit
state as discussed above.
/Daniel
