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https://issues.apache.org/jira/browse/JCS-158?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15103763#comment-15103763
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Wiktor N commented on JCS-158:
------------------------------
Great, thanks for quick fix
> NullPointerException in IndexedDiskCache.addToRecycleBin(...)
> -------------------------------------------------------------
>
> Key: JCS-158
> URL: https://issues.apache.org/jira/browse/JCS-158
> Project: Commons JCS
> Issue Type: Bug
> Components: Indexed Disk Cache
> Affects Versions: jcs-2.0-beta-1
> Reporter: Wiktor N
> Assignee: Thomas Vandahl
> Fix For: jcs-2.0-beta-2
>
>
> One of our users got the following exception:
> java.lang.NullPointerException
> at
> org.apache.commons.jcs.auxiliary.disk.indexed.IndexedDiskCache.addToRecycleBin(IndexedDiskCache.java:1181)
> at
> org.apache.commons.jcs.auxiliary.disk.indexed.IndexedDiskCache$LRUMapSizeLimited.processRemovedLRU(IndexedDiskCache.java:1785)
> at
> org.apache.commons.jcs.auxiliary.disk.indexed.IndexedDiskCache$LRUMapSizeLimited.processRemovedLRU(IndexedDiskCache.java:1684)
> at
> org.apache.commons.jcs.utils.struct.AbstractLRUMap.put(AbstractLRUMap.java:344)
> at
> org.apache.commons.jcs.auxiliary.disk.indexed.IndexedDiskCache$LRUMapSizeLimited.put(IndexedDiskCache.java:1732)
> at
> org.apache.commons.jcs.auxiliary.disk.indexed.IndexedDiskCache$LRUMapSizeLimited.put(IndexedDiskCache.java:1684)
> at
> org.apache.commons.jcs.utils.struct.AbstractLRUMap.putAll(AbstractLRUMap.java:187)
> at
> org.apache.commons.jcs.auxiliary.disk.indexed.IndexedDiskCache.loadKeys(IndexedDiskCache.java:343)
> at
> org.apache.commons.jcs.auxiliary.disk.indexed.IndexedDiskCache.initializeStoreFromPersistedData(IndexedDiskCache.java:286)
> at
> org.apache.commons.jcs.auxiliary.disk.indexed.IndexedDiskCache.initializeKeysAndData(IndexedDiskCache.java:250)
> at
> org.apache.commons.jcs.auxiliary.disk.indexed.IndexedDiskCache.<init>(IndexedDiskCache.java:182)
> at
> org.apache.commons.jcs.auxiliary.disk.indexed.IndexedDiskCacheFactory.createCache(IndexedDiskCacheFactory.java:60)
> at
> org.apache.commons.jcs.auxiliary.disk.indexed.IndexedDiskCacheFactory.createCache(IndexedDiskCacheFactory.java:33)
> My guess is, that during cache initialization doOptimizeRealTime() spawned a
> new thread calling optimizeFile().
> optimizeFile() does all actions governed by storageLock.writeLock(), but
> there are no guarantees, in which order addToRecycleBin() will see changes
> done by optimizeFile.
> I see two solutions to this problem:
> 1. Protect addToRecycleBin using storageLock.readLock() to ensure the same
> order of reads and writes with optimizeFile
> 2. Use volatile keyword on doRecycle / recycle objects and use Java Memory
> Model guarantees to order writes and reads in this two methods
> My feeling is that 1st solution is more coherent with current approach within
> JCS.
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