[jboss-jira] [JBoss JIRA] Updated: (JBRULES-2651) Concurrency issue in NamedEntryPoint.insert leads to occasional hanging in Drools

Concurrency issue in NamedEntryPoint.insert leads to occasional hanging in Drools --------------------------------------------------------------------------------- Key: JBRULES-2651 URL: https://jira.jboss.org/browse/JBRULES-2651 Project: Drools Issue Type: Bug Security Level: Public(Everyone can see) Components: drools-core (expert) Affects Versions: 5.0.1.FINAL Reporter: Norman Chan Assignee: Mark Proctor Fix For: 5.2.0.M1 I found this issue when my server stopped processing new requests and I did a thread dump. In examining the dump, I found that all of the processing threads, save two, were blocking while trying to acquire the lock in NamedEntryPoint.insert. Both of the other two threads appeared to be infinitely looping in the NamedEntryPoint.insert method. Here are snippets of their stack traces: ActiveMQ Session Task" prio=10 tid=0x00002aab0003b000 nid=0x7b98 runnable [0x000000004c086000..0x000000004c087c90] java.lang.Thread.State: RUNNABLE at org.drools.util.ObjectHashMap.remove(ObjectHashMap.java:121) at org.drools.common.SingleThreadedObjectStore.removeHandle(SingleThreadedObjectStore.java:150) at org.drools.common.NamedEntryPoint.retract(NamedEntryPoint.java:296) at org.drools.common.NamedEntryPoint.retract(NamedEntryPoint.java:245) at org.drools.reteoo.ReteooWorkingMemory$WorkingMemoryReteExpireAction.execute(ReteooWorkingMemory.java:350) at org.drools.common.AbstractWorkingMemory.executeQueuedActions(AbstractWorkingMemory.java:1488) at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:158) at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:122) at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:80) at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:28) at ActiveMQ Session Task" prio=10 tid=0x000000005a35cc00 nid=0xdf6 runnable [0x000000004a268000..0x000000004a269a90] java.lang.Thread.State: RUNNABLE at org.drools.util.AbstractHashTable.resize(AbstractHashTable.java:115) at org.drools.util.ObjectHashMap.put(ObjectHashMap.java:78) at org.drools.common.SingleThreadedObjectStore.addHandle(SingleThreadedObjectStore.java:136) at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:113) at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:80) at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:28) at So it seems like while the first thread is holding the lock and attempting to remove an object handle from the object store in NamedEntryPoint, the other thread is trying to resize that same object store in response to an addHandle call that puts it over the threshold. I haven't worked out exactly how these concurrent accesses to the same object store by two different threads causes an infinite loop in both threads, but it seems like the call to SingleThreadedObjectStore.addHandle should be preceded by acquiring the lock.