So using concurrent classes does not work? On Friday, August 28, 2015, Lewis John McGibbney (JIRA) <j...@apache.org> wrote:
> > [ > https://issues.apache.org/jira/browse/GORA-228?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel > ] > > Lewis John McGibbney reopened GORA-228: > --------------------------------------- > Assignee: Lewis John McGibbney (was: Yasin Kılınç) > > This is not fixed. > I've reverted the commit, as I stupidly tested it against Nutch and not > against Gora tests. Doh. Sorry folks. > > > java.util.ConcurrentModificationException when using MemStore for > concurrent tests > > > ---------------------------------------------------------------------------------- > > > > Key: GORA-228 > > URL: https://issues.apache.org/jira/browse/GORA-228 > > Project: Apache Gora > > Issue Type: Sub-task > > Components: gora-core > > Affects Versions: 0.3 > > Reporter: Lewis John McGibbney > > Assignee: Lewis John McGibbney > > Fix For: 0.7 > > > > Attachments: GORA-228.patch, GORA-228v2.patch > > > > > > Finally, a multithreaded test in [3] fails with the following > > {code} > > java.util.ConcurrentModificationException > > at > java.util.TreeMap$NavigableSubMap$SubMapIterator.nextEntry(TreeMap.java:1594) > > at > java.util.TreeMap$NavigableSubMap$SubMapKeyIterator.next(TreeMap.java:1655) > > at > org.apache.gora.memory.store.MemStore$MemResult.nextInner(MemStore.java:81) > > at org.apache.gora.query.impl.ResultBase.next(ResultBase.java:112) > > at > org.apache.nutch.storage.TestGoraStorage.readWrite(TestGoraStorage.java:74) > > at > org.apache.nutch.storage.TestGoraStorage.access$100(TestGoraStorage.java:41) > > at > org.apache.nutch.storage.TestGoraStorage$1.call(TestGoraStorage.java:107) > > at > org.apache.nutch.storage.TestGoraStorage$1.call(TestGoraStorage.java:102) > > at > java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334) > > at java.util.concurrent.FutureTask.run(FutureTask.java:166) > > at > java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) > > at > java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) > > at java.lang.Thread.run(Thread.java:722) > > {code} > > I believe that the final failure is due to to the use of TreeMap [5] as > a private object in MemStore. TreeMap implementations are not synchronized. > If multiple threads access a map concurrently, and at least one of the > threads modifies the map structurally, it must be synchronized externally. > (A structural modification is any operation that adds or deletes one or > more mappings; merely changing the value associated with an existing key is > not a structural modification.) This is typically accomplished by > synchronizing on some object that naturally encapsulates the map. If no > such object exists, the map should be "wrapped" using the > Collections.synchronizedSortedMap method. This is best done at creation > time, to prevent accidental unsynchronized access to the map e.g. > > SortedMap m = Collections.synchronizedSortedMap(new TreeMap(...)); > > N.B. The NOTE on TreeMap's come right from the Oracle JavaDoc. > > [3] > http://svn.apache.org/viewvc/nutch/branches/2.x/src/test/org/apache/nutch/storage/TestGoraStorage.java?view=markup > > [4] > http://svn.apache.org/viewvc/nutch/branches/2.x/src/test/org/apache/nutch/util/AbstractNutchTest.java?view=markup > > [5] http://docs.oracle.com/javase/6/docs/api/java/util/TreeMap.html > > > > -- > This message was sent by Atlassian JIRA > (v6.3.4#6332) >
