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HBase, mail # user - The Exceptions When Concurrently Writing and Reading


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The Exceptions When Concurrently Writing and Reading
Bing Li 2013-02-05, 18:39
Dear all,

To raise the performance of writing data into HBase, the
"synchronized" is removed from the writing method.

But after "synchronized" is removed from the method of writing, I get
the following exceptions when reading. Before the removal, no such
exceptions.

Could you help me how to solve it?

Thanks so much!

Best wishes,
Bing

      Feb 6, 2013 12:21:31 AM
org.apache.hadoop.hbase.ipc.HBaseClient$Connection run
      WARNING: Unexpected exception receiving call responses
java.lang.NullPointerException
          at org.apache.hadoop.hbase.io.HbaseObjectWritable.readObject(HbaseObjectWritable.java:521)
          at org.apache.hadoop.hbase.io.HbaseObjectWritable.readFields(HbaseObjectWritable.java:297)
          at org.apache.hadoop.hbase.ipc.HBaseClient$Connection.receiveResponse(HBaseClient.java:593)
          at org.apache.hadoop.hbase.ipc.HBaseClient$Connection.run(HBaseClient.java:505)
      Feb 6, 2013 12:21:31 AM
org.apache.hadoop.hbase.client.ScannerCallable close
      WARNING: Ignore, probably already closed
      java.io.IOException: Call to greatfreeweb/127.0.1.1:60020
failed on local exception: java.io.IOException: Unexpected exception
receiving call responses
          at org.apache.hadoop.hbase.ipc.HBaseClient.wrapException(HBaseClient.java:934)
          at org.apache.hadoop.hbase.ipc.HBaseClient.call(HBaseClient.java:903)
          at org.apache.hadoop.hbase.ipc.WritableRpcEngine$Invoker.invoke(WritableRpcEngine.java:150)
          at $Proxy6.close(Unknown Source)
          at org.apache.hadoop.hbase.client.ScannerCallable.close(ScannerCallable.java:112)
          at org.apache.hadoop.hbase.client.ScannerCallable.call(ScannerCallable.java:74)
          at org.apache.hadoop.hbase.client.ScannerCallable.call(ScannerCallable.java:39)
          at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.getRegionServerWithRetries(HConnectionManager.java:1325)
          at org.apache.hadoop.hbase.client.HTable$ClientScanner.nextScanner(HTable.java:1167)
          at org.apache.hadoop.hbase.client.HTable$ClientScanner.next(HTable.java:1296)
          at org.apache.hadoop.hbase.client.HTable$ClientScanner$1.hasNext(HTable.java:1356)
          at com.greatfree.hbase.rank.NodeRankRetriever.LoadNodeGroupNodeRankRowKeys(NodeRankRetriever.java:348)
          at com.greatfree.ranking.PersistNodeGroupNodeRanksThread.run(PersistNodeGroupNodeRanksThread.java:29)
          at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
          at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
          at java.lang.Thread.run(Thread.java:662) Caused by:
java.io.IOException: Unexpected exception receiving call responses
          at org.apache.hadoop.hbase.ipc.HBaseClient$Connection.run(HBaseClient.java:509)
      Caused by: java.lang.NullPointerException
          at org.apache.hadoop.hbase.io.HbaseObjectWritable.readObject(HbaseObjectWritable.java:521)
          at org.apache.hadoop.hbase.io.HbaseObjectWritable.readFields(HbaseObjectWritable.java:297)
          at org.apache.hadoop.hbase.ipc.HBaseClient$Connection.receiveResponse(HBaseClient.java:593)
          at org.apache.hadoop.hbase.ipc.HBaseClient$Connection.run(HBaseClient.java:505)

The writing method is as follows.
// The "synchronized" is removed to raise the performance.
// public synchronized void AddNodeViewGroupNodeRanks(String
hostNodeKey, String groupKey, int timingScale, Map<String, Double>
groupNodeRankMap)

public void AddNodeViewGroupNodeRanks(String hostNodeKey, String
groupKey, int timingScale, Map<String, Double> groupNodeRankMap)
{
        List<Put> puts = new ArrayList<Put>();
        Put hostNodeKeyPut;
        Put groupKeyPut;
        Put timingScalePut;
        Put nodeKeyPut;
        Put rankPut;

        byte[] groupNodeRankRowKey;

        for (Map.Entry<String, Double> nodeRankEntry :
groupNodeRankMap.entrySet())
        {
               groupNodeRankRowKey = Bytes.toBytes(...);

               hostNodeKeyPut = new Put(groupNodeRankRowKey);
               hostNodeKeyPut.add(...);
                puts.add(hostNodeKeyPut);
               ......

                rankPut = new Put(groupNodeRankRowKey);
               rankPut.add(...);
                puts.add(rankPut);
        }

        try
        {
                this.rankTable.put(puts);
        }
        catch (IOException e)
        {
                e.printStackTrace();
        }
}
The reading method that causes the exceptions is as follows.

        public Set<String> LoadNodeGroupNodeRankRowKeys(String
hostNodeKey, String groupKey, int timingScale)
        {
                List<Filter> nodeGroupFilterList = new ArrayList<Filter>();

                SingleColumnValueFilter hostNodeKeyFilter = new
SingleColumnValueFilter(...);
                hostNodeKeyFilter.setFilterIfMissing(true);
                nodeGroupFilterList.add(hostNodeKeyFilter);

                ......

                FilterList nodeGroupFilter = new
FilterList(nodeGroupFilterList);
                Scan scan = new Scan();
                scan.setFilter(nodeGroupFilter);
                scan.setCaching(Parameters.CACHING_SIZE);
                scan.setBatch(Parameters.BATCHING_SIZE);

                Set<String> rowKeySet = Sets.newHashSet();
                try
                {
                        ResultScanner scanner = this.rankTable.getScanner(scan);

                        // EXCEPTIONS are raised at the following line.
                        for (Result result : scanner)
                        {
                                for (KeyValue kv : result.raw())
                                {
rowKeySet.add(Bytes.toString(kv.getRow()));
                                        break;
                                }
                        }
                        scanner.close();
                }
                catch (IOException e)
                {
                        e.pri
+
Ted Yu 2013-02-05, 18:45
+
Bing Li 2013-02-05, 18:46
+
Ted Yu 2013-02-05, 18:49
+
Bing Li 2013-02-05, 19:00
+
Bing Li 2013-02-05, 19:20