[jboss-jira] [JBoss JIRA] Updated: (JGRP-891) ConcurrentModificationException during JBoss AS 5.0.0.GA startup

ConcurrentModificationException during JBoss AS 5.0.0.GA startup ---------------------------------------------------------------- Key: JGRP-891 URL: https://jira.jboss.org/jira/browse/JGRP-891 Project: JGroups Issue Type: Bug Affects Versions: 2.6.7 Reporter: Paul Ferraro Assignee: Bela Ban Priority: Minor Fix For: 2.6.8, 2.8 17:31:01,970 ERROR [UDP] failed handling incoming message java.util.ConcurrentModificationException at java.util.LinkedHashMap$LinkedHashIterator.nextEntry(LinkedHashMap.java:365) at java.util.LinkedHashMap$KeyIterator.next(LinkedHashMap.java:376) at java.util.AbstractCollection.containsAll(AbstractCollection.java:285) at java.util.AbstractSet.equals(AbstractSet.java:76) at org.jgroups.protocols.pbcast.STABLE.allVotesReceived(STABLE.java:428) at org.jgroups.protocols.pbcast.STABLE.addVote(STABLE.java:423) at org.jgroups.protocols.pbcast.STABLE.handleStableMessage(STABLE.java:554) at org.jgroups.protocols.pbcast.STABLE.up(STABLE.java:238) at org.jgroups.protocols.UNICAST.up(UNICAST.java:299) at org.jgroups.protocols.pbcast.NAKACK.handleMessage(NAKACK.java:842) at org.jgroups.protocols.pbcast.NAKACK.up(NAKACK.java:705) at org.jgroups.protocols.VERIFY_SUSPECT.up(VERIFY_SUSPECT.java:167) at org.jgroups.protocols.FD.up(FD.java:284) at org.jgroups.protocols.FD_SOCK.up(FD_SOCK.java:308) at org.jgroups.protocols.MERGE2.up(MERGE2.java:144) at org.jgroups.protocols.Discovery.up(Discovery.java:263) at org.jgroups.protocols.PING.up(PING.java:270) at org.jgroups.protocols.TP$ProtocolAdapter.up(TP.java:2319) at org.jgroups.protocols.TP.passMessageUp(TP.java:1253) at org.jgroups.protocols.TP.access$100(TP.java:49) at org.jgroups.protocols.TP$IncomingPacket.handleMyMessage(TP.java:1830) at org.jgroups.protocols.TP$IncomingPacket.run(TP.java:1809) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:650) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:675) at java.lang.Thread.run(Thread.java:595) Here are the problematic lines in STABLE.java: 427: private boolean allVotesReceived(Set<Address> votes) { 428: return votes.equals(mbrs); // compares identity, size and element-wise (if needed) 429: } Internally, the Set.equals(...) method will iterate over the mbrs set. The concurrent update is coming from the following code in STABLE.java: 330: private void handleViewChange(View v) { 331: Vector<Address> tmp=v.getMembers(); 332: synchronized(mbrs) { 333: mbrs.clear(); 334: mbrs.addAll(tmp); 335: } There are several ways fix this, including, but not limited to: * Wrap line 428 in a synchronized(mbrs) block * Make mbrs volatile instead of final, and create a new LinkedHashSet in handleViewChange(...) i.e. Replace 332-335 with: mbrs = new LinkedHashSet<Address>(tmp); * Make mbrs a CopyOnWriteArraySet<Address>