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From bhupeshchawda <...@git.apache.org>
Subject [GitHub] apex-malhar pull request #292: APEXMALHAR-1957: Updated HBase Input Operator
Date Thu, 23 Jun 2016 04:00:59 GMT
Github user bhupeshchawda commented on a diff in the pull request:

    https://github.com/apache/apex-malhar/pull/292#discussion_r68172749
  
    --- Diff: contrib/src/main/java/com/datatorrent/contrib/hbase/HBaseScanOperator.java ---
    @@ -40,27 +51,107 @@
      * @tags hbase, scan, input operator
      * @since 0.3.2
      */
    -public abstract class HBaseScanOperator<T> extends HBaseInputOperator<T>
    +public abstract class HBaseScanOperator<T> extends HBaseInputOperator<T>
implements Operator.ActivationListener<Context>
     {
    +  public static final int DEF_HINT_SCAN_LOOKAHEAD = 2;
    +  public static final int DEF_QUEUE_SIZE = 1000;
    +  public static final int DEF_SLEEP_MILLIS = 10;
    +
    +  private String startRow;
    +  private String endRow;
    +  private String lastReadRow;
    +  private int hintScanLookahead = DEF_HINT_SCAN_LOOKAHEAD;
    +  private int queueSize = DEF_QUEUE_SIZE;
    +  private int sleepMillis = DEF_SLEEP_MILLIS;
    +  private Queue<Result> resultQueue;
    +  private boolean threadFailed = false;
    +
    +  @AutoMetric
    +  protected long tuplesRead;
    +
    +  // Transients
    +  protected transient Scan scan;
    +  protected transient ResultScanner scanner;
    +  protected transient Thread readThread;
    +
    +  @Override
    +  public void setup(OperatorContext context)
    +  {
    +    super.setup(context);
    +    resultQueue = Queues.newLinkedBlockingQueue(queueSize);
    +  }
    +
    +  @Override
    +  public void activate(Context context)
    +  {
    +    startReadThread();
    +  }
    +
    +  protected void startReadThread()
    +  {
    +    try {
    +      scan = operationScan();
    +      scanner = getStore().getTable().getScanner(scan);
    +    } catch (IOException e) {
    +      throw new RuntimeException(e);
    +    }
    +    readThread = new Thread(new Runnable() {
    +      @Override
    +      public void run()
    +      {
    +        try {
    +          Result result;
    +          while ((result = scanner.next()) != null) {
    +            while (!resultQueue.offer(result)) {
    +              Thread.sleep(sleepMillis);
    +            }
    +          }
    +        } catch (Exception e) {
    +          logger.debug("Exception in fetching results {}", e.getMessage());
    +          threadFailed = true;
    +          throw new RuntimeException(e);
    +        } finally {
    +          scanner.close();
    +        }
    +      }
    +    });
    +    readThread.start();
    +  }
    +
    +  @Override
    +  public void beginWindow(long windowId)
    +  {
    +    super.beginWindow(windowId);
    +    tuplesRead = 0;
    +  }
     
       @Override
       public void emitTuples()
       {
    +    if (!readThread.isAlive() && threadFailed) {
    +      throw new RuntimeException("Exception in scan thread");
    --- End diff --
    
    I think if we should not just restart the thread without understanding what the issue
was. In any case, this exception will ultimately kill the operator and restart it from a consistent
state instead.


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