Seb Mo created OPENJPA-2470:
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Summary: DataCacheManagerImpl infinite loop for checking if
classes are cachable
Key: OPENJPA-2470
URL: https://issues.apache.org/jira/browse/OPENJPA-2470
Project: OpenJPA
Issue Type: Bug
Components: datacache
Affects Versions: 2.2.1
Environment: linux 64
Reporter: Seb Mo
Priority: Critical
We're integrated openjpa into our latest software delivery and in the last
three months we're ran two times into this issue. First time it was not
investigated at all, but the last time we've had the chance to grab extra
information out of the system.
At that point in time, we've had one of our processes not getting response back
from the application that was using openjpa.
All the connection threads were running the same calls:
2014-01-07 07:21:37,716 - INFO "ClientConnection - 9" prio=10
tid=0x00007f33d400e000 nid=0x8d9 runnable [0x00007f32db1ef000]
2014-01-07 07:21:37,716 - INFO java.lang.Thread.State: RUNNABLE
2014-01-07 07:21:37,716 - INFO at java.util.HashMap.getEntry(Unknown
Source)
2014-01-07 07:21:37,716 - INFO at java.util.HashMap.get(Unknown Source)
2014-01-07 07:21:37,716 - INFO at
org.apache.openjpa.datacache.DataCacheManagerImpl.isCachable(DataCacheManagerImpl.java:145)
2014-01-07 07:21:37,716 - INFO at
org.apache.openjpa.datacache.DataCacheManagerImpl.selectCache(DataCacheManagerImpl.java:128)
2014-01-07 07:21:37,716 - INFO at
org.apache.openjpa.datacache.DataCacheStoreManager.initialize(DataCacheStoreManager.java:358)
2014-01-07 07:21:37,716 - INFO at
org.apache.openjpa.kernel.DelegatingStoreManager.initialize(DelegatingStoreManager.java:112)
2014-01-07 07:21:37,716 - INFO at
org.apache.openjpa.kernel.ROPStoreManager.initialize(ROPStoreManager.java:57)
2014-01-07 07:21:37,716 - INFO at
org.apache.openjpa.kernel.BrokerImpl.initialize(BrokerImpl.java:1027)
2014-01-07 07:21:37,716 - INFO at
org.apache.openjpa.kernel.BrokerImpl.find(BrokerImpl.java:985)
2014-01-07 07:21:37,716 - INFO at
org.apache.openjpa.kernel.BrokerImpl.find(BrokerImpl.java:907)
2014-01-07 07:21:37,716 - INFO at
org.apache.openjpa.jdbc.kernel.JDBCStoreManager.load(JDBCStoreManager.java:1041)
2014-01-07 07:21:37,716 - INFO at
org.apache.openjpa.jdbc.sql.AbstractResult.load(AbstractResult.java:280)
2014-01-07 07:21:37,716 - INFO at
org.apache.openjpa.jdbc.sql.SelectImpl$SelectResult.load(SelectImpl.java:2381)
2014-01-07 07:21:37,716 - INFO at
org.apache.openjpa.jdbc.meta.strats.RelationToManyInverseKeyFieldStrategy.loadElement(RelationToManyInverseKeyFieldStrategy.java:90)
2014-01-07 07:21:37,716 - INFO at
org.apache.openjpa.jdbc.meta.strats.RelationCollectionInverseKeyFieldStrategy.loadElement(RelationCollectionInverseKeyFieldStrategy.java:76)
2014-01-07 07:21:37,716 - INFO at
org.apache.openjpa.jdbc.meta.strats.StoreCollectionFieldStrategy.load(StoreCollectionFieldStrategy.java:558)
2014-01-07 07:21:37,716 - INFO at
org.apache.openjpa.jdbc.meta.FieldMapping.load(FieldMapping.java:934)
2014-01-07 07:21:37,717 - INFO at
org.apache.openjpa.jdbc.kernel.JDBCStoreManager.load(JDBCStoreManager.java:702)
2014-01-07 07:21:37,717 - INFO at
org.apache.openjpa.kernel.DelegatingStoreManager.load(DelegatingStoreManager.java:117)
2014-01-07 07:21:37,717 - INFO at
org.apache.openjpa.datacache.DataCacheStoreManager.load(DataCacheStoreManager.java:461)
2014-01-07 07:21:37,717 - INFO at
org.apache.openjpa.kernel.DelegatingStoreManager.load(DelegatingStoreManager.java:117)
2014-01-07 07:21:37,717 - INFO at
org.apache.openjpa.kernel.ROPStoreManager.load(ROPStoreManager.java:78)
2014-01-07 07:21:37,717 - INFO at
org.apache.openjpa.kernel.StateManagerImpl.loadFields(StateManagerImpl.java:3061)
2014-01-07 07:21:37,717 - INFO at
org.apache.openjpa.kernel.StateManagerImpl.loadField(StateManagerImpl.java:3136)
2014-01-07 07:21:37,717 - INFO at
org.apache.openjpa.kernel.StateManagerImpl.beforeAccessField(StateManagerImpl.java:1606)
2014-01-07 07:21:37,717 - INFO at
org.apache.openjpa.kernel.StateManagerImpl.accessingField(StateManagerImpl.java:1591)
....
We've narrowed this down to the fact that a HashMap is used in the
org.apache.openjpa.datacache.DataCacheManagerImpl to globally serv our all the
threads. So multiple threads can add and get information from the _cacheable at
the same time.
HashMaps are not thread safe and can get corrupted with eating the entire CPU.
The problem is better described here (but you can find it in a lot of places):
http://mailinator.blogspot.com/2009/06/beautiful-race-condition.html
I could not find this bug logged yet and I'm surprised that nobody has ran into
this yet.
Our plan for now is to just switch to ConcurrentHashMap instantiation for the
_cacheable Map.
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