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https://issues.apache.org/jira/browse/GEODE-9033?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17300600#comment-17300600
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Darrel Schneider commented on GEODE-9033:
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Another idea is to have the read do multiple reads if it detects that the
version changed between reads of the version and value. It could eventually
(after doing multiple reads) stop spinning and drop into synchronization. This
would prevent a read from being blocked behind a blocked writer (since in that
case the version and value are not changing) and also prevent a reader from
spinning forever if the writers are constantly changing the version and value.
> client read operations should not be blocked by a write operation
> -----------------------------------------------------------------
>
> Key: GEODE-9033
> URL: https://issues.apache.org/jira/browse/GEODE-9033
> Project: Geode
> Issue Type: Improvement
> Components: client/server
> Reporter: Darrel Schneider
> Priority: Major
>
> Client read operations currently will be blocked by a write operation that is
> in progress.
> This is caused by the write operation holding a synchronization on the
> RegionEntry and LocalRegion.getDeserializedValue synchronizing the
> RegionEntry with clientEvent is not null in order to atomically obtain both
> the entry's value and version.
> The read code in LocalRegion that causes this is:
> {code:java}
> synchronized (regionEntry) {
> // value & version must be obtained atomically
>
> clientEvent.setVersionTag(regionEntry.getVersionStamp().asVersionTag());
> value = getDeserialized(regionEntry, updateStats,
> disableCopyOnRead,
> preferCachedDeserializable, retainResult);
> }
> {code}
> To fix this it may be possible to change the write operations to synchronize
> on something else while changing both the value and version (but not while
> doing anything else). Then the read code can sync on that new Object and not
> the RegionEntry instance.
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