[jboss-jira] [JBoss JIRA] Commented: (JGRP-664) CopyOnWrite collections should be synchronized

CopyOnWrite collections should be synchronized ---------------------------------------------- Key: JGRP-664 URL: http://jira.jboss.com/jira/browse/JGRP-664 Project: JGroups Issue Type: Bug Reporter: Bela Ban Assigned To: Bela Ban Fix For: 2.7, 2.4.2, 2.6.2 [email from Rick Pike] Sometimes when we have nodes start suspecting each other we see intermittent: 2008-01-14 06:49:37,464 [ERROR] UDP failed handling incoming message java.lang.IndexOutOfBoundsException: Index: 0, Size: 0 at java.util.concurrent.CopyOnWriteArrayList.rangeCheck(CopyOnWriteArrayList.java:708) at java.util.concurrent.CopyOnWriteArrayList.get(CopyOnWriteArrayList.java:328) at org.jgroups.protocols.FD.getPingDest(FD.java:151) at org.jgroups.protocols.FD.up(FD.java:305) at org.jgroups.protocols.FD_ICMP.up(FD_ICMP.java:108) at org.jgroups.protocols.MERGE3.up(MERGE3.java:126) at org.jgroups.protocols.Discovery.up(Discovery.java:246) at org.jgroups.protocols.TP$IncomingPacket.handleMyMessage(TP.java:1535) at org.jgroups.protocols.TP$IncomingPacket.run(TP.java:1484) 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) It looks like there's 4 places in FD that modify the pingable_mbrs list: 1. up(HEARTBEAT_ACK) 2. up(SUSPECT) 3. down(VIEW_CHANGE) 4. down(UNSUSPECT) Only #1 and #3 appear to synchronize{} around the edits, and I believe that a concurrent (UN)SUSPECT message is emptying that list whille the HEARTBEAT_ACK is looping and repeatedly reading - inside getPingDest(). Every so often, it calls get(0) on an empty list. We just started seeing this when we started testing with FD_ICMP, but I imagine this would happen with any flavor, and we're seeing it due to the high volume of SUSPECT messages happening in our tests.