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https://issues.apache.org/jira/browse/OPENJPA-1967?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Rick Curtis updated OPENJPA-1967:
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Attachment: (was: OPENJPA-1967.ut.patch)
> Got stale data from cache in multi threaded application
> -------------------------------------------------------
>
> Key: OPENJPA-1967
> URL: https://issues.apache.org/jira/browse/OPENJPA-1967
> Project: OpenJPA
> Issue Type: Bug
> Components: datacache
> Affects Versions: 1.2.2, 2.1.0
> Reporter: Noriyuki Kajitani
> Priority: Minor
> Attachments: OPENJPA-1867.ut.patch, OpenJPA-1967_UT.zip
>
>
> In multi threaded application, I experienced getting a stale data from
> OpenJPA even right after updating it. Let's say a thread (named T1)
> updates a data with a value (V0) to (V1), then retrieves it from
> OpenJPA. An another thread also retrieves it in a same time. Here,
> it is expected that T1 retrieves a value V1, but it may get old value
> V0, which is not expected behavior.
> The cause seems OpenJPA's putting a stale data in its cache. It could
> occur in the following three cases in both OpenJPA 1.2.2 and 2.1.0.
> case 1:
> See org.apache.openjpa.datacache.DataCacheStoreManager.java#load method.
> Let's say a thread is going to acquire write lock at the Line 402. At the
> same time, the other thread can cached the data out during its operation. In
> such case, the data becomes null when it reaches the Line 404.
> 404:data = cache.get(sm.getObjectId());
> It does not compare the data version, so stale data is cached in the
> following part even if data has been updated in other threads.
> 405:if (data != null && compareVersion(sm, sm.getVersion(),
> 406: data.getVersion()) == VERSION_EARLIER)
> ....
> 410: boolean isNew = data == null;
> 411: if (isNew)
> 412: data = newPCData(sm);
> 413: data.store(sm, fields);
> 414: if (isNew)
> 415: cache.put(data);
> case 2:
> See org.apache.openjpa.datacache.DataCacheStoreManager.java#initialize method.
> Let's say a thread is going to acquire write lock at the Line 358. At the
> same time, the other thread can cached the data out during its operation. In
> such case, the data becomes null when it reaches the Line 360.
> 360:data = cache.get(sm.getObjectId());
> It does not compare the data version, so stale data is cached in the
> following part even if data has been updated in other threads.
> 361:if (data != null && compareVersion(sm, sm.getVersion(),
> 362: data.getVersion()) == VERSION_EARLIER)
> ....
> 368: if (data == null)
> 369: data = newPCData(sm);
> 370: data.store(sm);
> 371: cache.put(data);
> case 3:
> See org.apache.openjpa.datacache.DataCacheStoreManager.java#updateCaches.
> The cache was not locked during its access. So it could cache a stale data
> in multithreaded application. Here's a case:
> The thread1 gets the data from OpenJPA.
> The thread2 updates and gets the data from OpenJPA.
> thread2:gets the data from cache.
> thread2:sets something value to column.
> thread2:updates to database.
> thread2:flush
> thread2:gets data from cache.
> thread1:OpenJPA expires the cached data.
> thread1:creates cache data.
> thread2:sets something value different from previous set value to column.
> thread2:puts data in cache.
> thread1:puts data in cache. <= override by stale data.
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