ConcurrentModificationException during logout
---------------------------------------------
Key: JCR-798
URL: https://issues.apache.org/jira/browse/JCR-798
Project: Jackrabbit
Issue Type: Bug
Components: core
Environment: Jackrabbit 1.2.1
Reporter: Martijn Hendriks
We regularly get the following exception:
java.util.ConcurrentModificationException
at
org.apache.commons.collections.map.AbstractReferenceMap$ReferenceEntrySetIterator.checkMod(AbstractReferenceMap.java:761)
at
org.apache.commons.collections.map.AbstractReferenceMap$ReferenceEntrySetIterator.hasNext(AbstractReferenceMap.java:735)
at
java.util.Collections$UnmodifiableCollection$1.hasNext(Collections.java:1009)
at
java.util.Collections$UnmodifiableCollection$1.hasNext(Collections.java:1009)
at
org.apache.jackrabbit.core.state.LocalItemStateManager.dispose(LocalItemStateManager.java:341)
at
org.apache.jackrabbit.core.WorkspaceImpl.dispose(WorkspaceImpl.java:170)
at org.apache.jackrabbit.core.SessionImpl.logout(SessionImpl.java:1225)
at
org.apache.jackrabbit.core.XASessionImpl.logout(XASessionImpl.java:379)
Two causes for this exception have been identified:
(Taken from an email to the dev-list from Marcel Reutegger):
> - session A reads some items I
> - session B transiently removes items in I
> - session A logs out and starts to iterate over I in LocalItemStateManager
> (LISM)
> - session B saves changes and removed items are evicted from A's LISM
> - session A gets concurrent modification exception
Another scenario is the following:
- Session A gets the iterator of the values of (the primary cache of) an
ItemStateReferenceCache in LocalItemStateManager.dispose.
- Session B then does something that triggers the CacheManager.
- The CacheManager then calls resizeAll, and evicts some items from the
secondary cache of the ItemStateReferenceCache of which the
LocalItemStateManager has a values iterator.
- The garbage collector then runs and evicts the removed items also from the
primary cache, which effectively modifies the set over which is iterated.
Regards,
Martijn Hendriks
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