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https://issues.apache.org/jira/browse/GEODE-8142?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Darrel Schneider resolved GEODE-8142.
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Resolution: Won't Do
I looked into doing this but a couple of things about the callback arg makes it
less than ideal for this solution.
# Callback args are themselves distributed so we could end up transmitting it
once as the Delta and once as the callback arg.
# In some cases the implementation may not make the callback arg available in
which case it would be null.
> Enhance the Delta interface to support callbackArgs
> ---------------------------------------------------
>
> Key: GEODE-8142
> URL: https://issues.apache.org/jira/browse/GEODE-8142
> Project: Geode
> Issue Type: Improvement
> Components: core
> Reporter: Darrel Schneider
> Assignee: Darrel Schneider
> Priority: Major
>
> The Geode Delta interface allows for a subset of the actual data to
> distributed to redundant copies when storing data in a Geode region. It
> requires you to implement hasDelta, toDelta, and fromDelta on your domain
> class. In most cases when you implement these methods you find you need to
> add some additional instance variables to your domain class just for hasDelta
> and toDelta to read. So Delta saves you in how much data needs to be
> serialized for distribution, but it may hurt you in how much memory your
> domain object uses.
> Geode has another concept call a "callbackArg". It is an extra parameter that
> can be passed to the Region methods, that will in turn be given to various
> callbacks that the user has installed.
> I propose we enhance hasDelta and toDelta to have a form of the method that
> is given the callback argument. The default implementation of this method
> would just be to ignore the callback arg and call the old method. But this
> would allow users to to override the new methods and have all the delta
> information passed to them as a callback argument. Since the callback arg is
> garbage collected after the operation it was given to completes, this would
> allow Delta to be implemented without introducing extra long lived memory
> overhead.
> I have looked at the places Geode currently calls hasDelta and toDelta
> internally, and the callback argument is available in those contexts so this
> would be a rather easy feature to add.
> I know that the Geode Redis API project could benefit from it.
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