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

[Bela Ban (JIRA)]

     [ https://jira.jboss.org/jira/browse/JGRP-891?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Bela Ban resolved JGRP-891.
---------------------------

    Resolution: Done


wrapped 428 in synchronized statement, no issue for perf because this method is not called a lot

> 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>

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