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Eshcar Hillel commented on HBASE-15991: --------------------------------------- Some comments: 1. The exception is due to StealJobQueue extending PriorityBlockingQueue which throws the exception when it cannot determine the position of the item in the queue. I agree there is no need in a priority queue for the in-memory flush, at least for now. If it is required in the future the attribute for comparison will become obvious as well. 2. We should consider the pros/cons of LinkedBlockingQueue vs other queue such as ConcurrentLinkedQueue. see in http://stackoverflow.com/questions/1301691/java-queue-implementations-which-one "The most important difference between LinkedBlockingQueue and ConcurrentLinkedQueue is that if you request an element from a LinkedBlockingQueue and the queue is empty, your thread will wait until there is something there. A ConcurrentLinkedQueue will return right away with the behavior of an empty queue." on the other hand in ConcurrentLinkedQueue "Beware that, unlike in most collections, the size method is NOT a constant-time operation. Because of the asynchronous nature of these queues, determining the current number of elements requires a traversal of the elements." So we need to consider what is more important having a size method with constant time, or making sure retrieving an element never blocks. > CompactingMemstore#InMemoryFlushRunnable should implement > Comparable/Comparator > ------------------------------------------------------------------------------- > > Key: HBASE-15991 > URL: https://issues.apache.org/jira/browse/HBASE-15991 > Project: HBase > Issue Type: Sub-task > Affects Versions: 2.0.0 > Reporter: ramkrishna.s.vasudevan > Assignee: ramkrishna.s.vasudevan > Priority: Critical > Fix For: 2.0.0 > > Attachments: HBASE-15991.patch, HBASE-15991_test.patch > > > Configuring CompactingMemstore for a table fails due to the following error > {code} > 2016-06-08 23:27:03,761 ERROR [B.defaultRpcServer.handler... > 2016-06-08 23:27:03,761 ERROR > [B.defaultRpcServer.handler=38,queue=8,port=16041] ipc.RpcServer: Unexpected > throwable object > java.lang.ClassCastException: > org.apache.hadoop.hbase.regionserver.CompactingMemStore$InMemoryFlushRunnable > cannot be cast to java.lang.Comparable > at > java.util.concurrent.PriorityBlockingQueue.siftUpComparable(PriorityBlockingQueue.java:357) > at > java.util.concurrent.PriorityBlockingQueue.offer(PriorityBlockingQueue.java:489) > at > org.apache.hadoop.hbase.util.StealJobQueue$1.offer(StealJobQueue.java:56) > at > java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1361) > at > org.apache.hadoop.hbase.regionserver.CompactingMemStore.checkActiveSize(CompactingMemStore.java:258) > at > org.apache.hadoop.hbase.regionserver.AbstractMemStore.internalAdd(AbstractMemStore.java:403) > at > org.apache.hadoop.hbase.regionserver.AbstractMemStore.add(AbstractMemStore.java:113) > at org.apache.hadoop.hbase.regionserver.HStore.add(HStore.java:630) > at > org.apache.hadoop.hbase.regionserver.HRegion.applyToMemstore(HRegion.java:3769) > at > org.apache.hadoop.hbase.regionserver.HRegion.applyFamilyMapToMemstore(HRegion.java:3740) > at > org.apache.hadoop.hbase.regionserver.HRegion.doMiniBatchMutate(HRegion.java:3222) > at > org.apache.hadoop.hbase.regionserver.HRegion.batchMutate(HRegion.java:2954) > at > org.apache.hadoop.hbase.regionserver.HRegion.batchMutate(HRegion.java:2896) > at > org.apache.hadoop.hbase.regionserver.RSRpcServices.doBatchOp(RSRpcServices.java:868) > at > org.apache.hadoop.hbase.regionserver.RSRpcServices.doNonAtomicRegionMutation(RSRpcServices.java:830) > at > org.apache.hadoop.hbase.regionserver.RSRpcServices.multi(RSRpcServices.java:2307) > at > org.apache.hadoop.hbase.protobuf.generated.ClientProtos$ClientService$2.callBlockingMethod(ClientProtos.java:34826) > > {code} > It is a straight forward fix. But If we implement the Comparable the > compareTo() should be based on what attribute? Should be based on the time? -- This message was sent by Atlassian JIRA (v6.3.4#6332)