Wiktor N created JCS-158:
----------------------------
Summary: 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
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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