[jbosscache-issues] [JBoss JIRA] Commented: (JBCACHE-1580) Type safety problem with dead member buddy backup region

Type safety problem with dead member buddy backup region -------------------------------------------------------- Key: JBCACHE-1580 URL: https://jira.jboss.org/jira/browse/JBCACHE-1580 Project: JBoss Cache Issue Type: Bug Security Level: Public(Everyone can see) Components: Buddy Replication, Cache loaders Affects Versions: 3.2.4.GA Reporter: Brian Stansberry Assignee: Manik Surtani Priority: Critical Attachments: JBCACHE-1580.patch I'm seeing problems with data gravitation when testing JBC 3.2.4 against JBoss AS trunk and the current EAP branch. I think the problem I describe here goes back a long way; nothing new in 3.2.4, but for some reason it's popping up now.[1] The problem is that when a :DEAD member region is created, it gets a child node whose name is of type Integer. There is code in JBC that assumes names for all children of these :DEAD nodes will be of type Integer. But CacheLoaders, particularly FileCacheLoader, cannot make such a guarantee. If the attempt to determine the children of the :DEAD node results in a call to CacheLoader.getChildrenNames(), there are type safety problems, e.g. this failure when a cache get() for a non-existent Fqn is invoked: java.lang.ArrayStoreException: java.lang.String at java.util.AbstractCollection.toArray(AbstractCollection.java:171) at org.jboss.cache.commands.read.GravitateDataCommand.perform(GravitateDataCommand.java:135) at org.jboss.cache.interceptors.CallInterceptor.invokeCommand(CallInterceptor.java:108) at org.jboss.cache.interceptors.CallInterceptor.handleDefault(CallInterceptor.java:99) at org.jboss.cache.commands.AbstractVisitor.visitGravitateDataCommand(AbstractVisitor.java:135) You can see the problem in this snippet from GravitateDataCommand.perform(): if (buddyFqnTransformer.isDeadBackupRoot(backupRoot)) { Set<Integer> deadChildNames = new TreeSet<Integer>(spi.getChildrenNames(backupRoot)); Integer[] elems = deadChildNames.toArray(new Integer[deadChildNames.size()]); spi.getChildrenNames() is not guaranteed to return a Set<Integer>, and definitely will not if it calls FileCacheLoader.getChildrenNames(). I've also seen ClassCastException in that same area in a compareTo() method being invoked by TreeSet. I'll attach a patch that makes the problem go away (i.e. allows the failing AS test to pass.) Basically adds a utility method to BuddyFqnTransformer that does a conversion of the return value from CacheLoader.getChildrenNames() to Set<Integer>. Then changes the 3 places that use the contents of the CacheLoader.getChildrenNames() to have them use this utility method. Another approach would be to change the return type of FileCacheLoader.getChildrenNames() to Set<?> (same as the interface) and call the new BuddyFqnTransformer utility method from there. But that changes the API of FileCacheLoader, plus requires injecting BuddyFqnTransformer into FileCacheLoader. Sorry; I don't have a proper unit test for this. :-( I thought this was an AS bug (there was a related one -- JBCLUSTER-269) and used all my time trying to fix it at the wrong level. [1] I only saw the problem when I started testing AS + 3.2.4 + JGroups 2.6.15. With 2.6.13 it didn't happen. I think the JGroups change must have for some reason resulted in :DEAD member regions being created that weren't before; the test that's failing involves stopping and starting caches. Perhaps a timing thing. There was a flaw in an AS class that should have resulted in the test failing if :DEAD member regions were being created before, so the fact that the test has been passing tells me they weren't.