Dominik Smogór created SLING-6852:
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Summary: A question about reliability of keeping non DS tracked
references
Key: SLING-6852
URL: https://issues.apache.org/jira/browse/SLING-6852
Project: Sling
Issue Type: Task
Components: Best practices
Affects Versions: Sling Models Impl 1.2.0
Reporter: Dominik Smogór
Priority: Minor
It's a generic best practice question but illustrated on an example within
sling models.
We have 2 kind osgi services being in parent - child
1. a factory service that programmatically registers number listener services
2. the listener services.
The listener services are called asynchronously (usually in a white board
manner) by some 3rd party components.
Now, the listener services implementations are keeping a simple object
references to the parent service. Osgi is not aware of this link and is not
tracking it in any way.
An example of such a relation is here
http://grepcode.com/file/repo1.maven.org/maven2/org.apache.sling/org.apache.sling.models.impl/1.2.0/org/apache/sling/models/impl/ModelAdapterFactory.java#900:
with the ModelAdapterFactory creating instances of ModelPackageBundleListener
which self register themselves with BundleTracker.
No the question is: what guarantee do we have that the child services will
never use defunct instances of parent objects after they have been deactivated
by OSGI (for whatever reason)?
Isn't it a potential for race conditions (that partner is used frequently
throughout sling code base) during after related to bundle / component restarts?
(disclaimer: I've used the highest sling models version that's there on
grepcode)
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