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https://issues.apache.org/jira/browse/GEODE-707?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Anthony Baker updated GEODE-707:
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Fix Version/s: 1.0.0-alpha1
> Concurrent cache-load doesn't invoke loader multiple times if there is an
> exception in the first load
> -----------------------------------------------------------------------------------------------------
>
> Key: GEODE-707
> URL: https://issues.apache.org/jira/browse/GEODE-707
> Project: Geode
> Issue Type: Bug
> Components: core
> Reporter: Bruce Schuchardt
> Assignee: Bruce Schuchardt
> Fix For: 1.0.0-alpha1
>
>
> This is from an old Pivotal ticket that was fixed in bugfix branches but
> never made it to develop. The ticket text follows:
> I see following behavior when we have a condition where 2 get() calls are
> sent concurrently for the same key in which Loader is called,
> If the first call is sent to Loader we create a Future.
> For second call we wait on this Future.
> Before first call is finished we check second call its a cache miss here
> as well(which we have checked before) we have isCreate=true.
> In case when isCreate is true in that flow we actually return null if we
> can't see the value(which can be true in case we got an exception on the
> first Loader call).
> Now from customer point of view this is inconsistent, as they except GemFire?
> to try again with the Loader and return exception as that is the true state
> here.
> [Darrel's reply]
> The first get creates a future and when it completes sets the future. If the
> first get fails with an exception (like a CacheLoaderException?) it still
> sets the future with this code in a finally block:
> VersionTag? tag = (clientEvent==null)? null : clientEvent.getVersionTag();
> thisFuture.set(new Object[]{result, tag});
> In the case of the first get failing with an exception "result" will be null
> so it sets the future to an array whose first element is null.
> The second get is waiting on the future. It returns this array and sees the
> first element as null which causes it to just return null. I think what it
> used to do was see Future.get return null (instead of an array with null in
> it) and this caused it to fall through and attempt to do the load itself
> which I think is what the customer also expects. You can see in the code this
> was what was intended by this comment that still remains:
> if value == null, try our own search/load
> Also if you look at the code in PartitionedRegion? that overrides this
> LocalRegion? code you will see that it does exactly this; if an exception is
> thrown the future is set to null and the second get see null returned from
> the future, falls through, and attempts the load itself.
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