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https://issues.apache.org/jira/browse/OFBIZ-2186?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12680015#action_12680015
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Benoit Wiart commented on OFBIZ-2186:
-------------------------------------
M. Jones,
CacheLineTable and LRUMap do not synchronize on the same lock
- CacheLineTable synchronization use the CacheLineTable instance monitor
- LRUMap synchronization use the LRUMap instance monitor
the LRUMap (memoryTable) can be updated concurrently by 2 differents threads
(or more than 2)
- one in the CacheLineTable #put or CacheLineTable#remove
- another in the CacheLineTable#get
this leads to the corrupton of the LRUMap which is not thread-safe
the CacheLineTable#get should be synchronized or the LRUMap should be replaced
by a thead safe collection
Benoit Wiart
www.ubik-ingenierie.com
> OutOfMemory provoked by Cache overflow
> --------------------------------------
>
> Key: OFBIZ-2186
> URL: https://issues.apache.org/jira/browse/OFBIZ-2186
> Project: OFBiz
> Issue Type: Bug
> Components: framework
> Affects Versions: SVN trunk, Release Branch 4.0
> Environment: Linux, JDK 1.5_15, Xmx set to 1156Mo
> Reporter: Philippe Mouawad
> Priority: Critical
> Attachments: CacheLineTable-patch.txt, OfbizBug.zip
>
>
> In our production system, we had an OutOfMemoryError.
> I analyzed the generated Heap Dump and found the following:
> The cache entitycache.entity-list.default.ProductCategoryMember retains a
> heap of 369314128 Bytes.
> The LRUMap hold by this object is occupying this space (369314128) and this
> object has a stange state:
> - maxSize is set to 5000 (as set in the cache.properties)
> - size is 128930 => PROBLEM
> IN cache.properties:
> entitycache.entity-list.default.ProductCategoryMember.expireTime=3600000
> entitycache.entity-list.default.ProductCategoryMember.useSoftReference=true
> entitycache.entity-list.default.ProductCategoryMember.maxInMemory=5000
> entitycache.entity-list.default.ProductCategoryMember.maxSize=7500
> I analyzed the code of LRUMap and its usage in CacheLineTable and IMHO the
> bug is a missing synchonized in get():
> public CacheLine<V> get(Object key) {
> if (key == null) {
> if (Debug.verboseOn()) Debug.logVerbose("In CacheLineTable tried
> to get with null key, using NullObject" + this.cacheName, module);
> }
> return getNoCheck(key);
> }
> Since LRUMap extends LinkedHashMap, if you look at get method, it changes the
> state of the Map by calling e.recordAccess(this):
> public V get(Object key) {
> Entry<K,V> e = (Entry<K,V>)getEntry(key);
> if (e == null)
> return null;
> e.recordAccess(this);
> return e.value;
> }
> So the default of synchronization corrupts the state of LRUMap which grows
> indefinitely
> I will submit a patch for this on the trunk.
> Philippe
> www.ubik-ingenierie.com
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