I have the following case in ops4j pax-jdbc-config
https://github.com/ops4j/org.ops4j.pax.jdbc/tree/master/pax-jdbc-config
I have a ManagesServiceFactory that watches for configs (representing
desired datasources) being created and destroyed.
For each config I select a DataSourceFactory service by properties
specified in the config. I then create DataSource and publish it as a
service.
When the config disappears I have to remove the service again.
The difficult thing here is that at the moment when the "updated" for
the config comes in there may not yet be a suitable DataSourceFactory
service. In my first prototype I then just do not create the DataSource.
The problem with this is of course that at startup it is very probable
that the configs come in before the DataSourceFactories are up. So my
current approach leads to the problem that the DataSources are not
created at all in some cases.
So are there any best practices or patterns how to handle this? I think
it is a bit similar to blueprint that needs to wait for namespace
handlers. I am not sure though if the timeout approach blueprint uses is
a good way to approach this. On the other hand you have to report back
to the user that his config might be wrong at some point.
Christian
--
Christian Schneider
http://www.liquid-reality.de
Open Source Architect
http://www.talend.com
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