[
https://issues.apache.org/jira/browse/SLING-6852?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16007947#comment-16007947
]
Justin Edelson commented on SLING-6852:
---------------------------------------
it would be best to ask generic OSGi questions on the osgi-dev mailing list.
In this specific example, I'm not sure what you mean by "listener services".
ModelAdapterFactory creates a BundleListener *object* whose lifecycle it
controls. In turn, the BundleListener registers a number of services, but again
it controls their lifecycle. So you could say that ModelAdapterFactory is
responsible for the lifecycle of those services, but there's no "listener
services" per se.
I should note that while this pattern is relatively common in Sling, it isn't
something recommended for "normal" users of OSGi. Sling is a provider of
infrastructure and so ends up using more low-level features than normal
applications.
> 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)
--
This message was sent by Atlassian JIRA
(v6.3.15#6346)
