content: /**
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */
  package org.apache.apex.examples.exactlyonce;
  
  import org.apache.apex.examples.exactlyonce.ExactlyOnceJdbcOutputApp.KafkaSinglePortStringInputOperator;
  import org.apache.apex.malhar.lib.io.ConsoleOutputOperator;
  import org.apache.apex.malhar.lib.io.fs.AbstractFileOutputOperator;
  import org.apache.apex.malhar.lib.util.KeyValPair;
  import org.apache.apex.malhar.lib.wal.FSWindowDataManager;
  import org.apache.hadoop.conf.Configuration;
  
  import com.datatorrent.api.Context;
  import com.datatorrent.api.DAG;
  import com.datatorrent.api.StreamingApplication;
  import com.datatorrent.api.annotation.ApplicationAnnotation;
  
  @ApplicationAnnotation(name = "ExactlyOnceFileOutput")
  /**
   * @since 3.8.0
   */
  public class ExactlyOnceFileOutputApp implements StreamingApplication
  {
    @Override
    public void populateDAG(DAG dag, Configuration configuration)
    {
      KafkaSinglePortStringInputOperator kafkaInput = dag.addOperator("kafkaInput",
          new KafkaSinglePortStringInputOperator());
      kafkaInput.setWindowDataManager(new FSWindowDataManager());
  
      ExactlyOnceJdbcOutputApp.UniqueCounterFlat count = dag.addOperator("count",
          new ExactlyOnceJdbcOutputApp.UniqueCounterFlat());
  
      FileWriter fileWriter = dag.addOperator("fileWriter", new FileWriter());
  
      ConsoleOutputOperator cons = dag.addOperator("console", new ConsoleOutputOperator());
      dag.addStream("words", kafkaInput.outputPort, count.data);
      dag.addStream("counts", count.counts, fileWriter.input, cons.input);
    }
  
    /**
     * This implementation of {@link AbstractFileOutputOperator} writes to a single file. However when it doesn't
     * receive any tuples in an application window then it finalizes the file, i.e., the file is completed and will not
     * be opened again.
     * <p/>
     * If more tuples are received after a hiatus then they will be written to a part file -
     * {@link #FILE_NAME_PREFIX}.{@link #part}
     */
    public static class FileWriter extends AbstractFileOutputOperator<KeyValPair<String, Integer>>
    {
      static final String FILE_NAME_PREFIX = "filestore";
  
      private int part;
      private transient String currentFileName;
  
      private transient boolean receivedTuples;
  
      @Override
      public void setup(Context.OperatorContext context)
      {
        currentFileName = (part == 0) ? FILE_NAME_PREFIX : FILE_NAME_PREFIX + "." + part;
        super.setup(context);
      }
  
      @Override
      protected String getFileName(KeyValPair<String, Integer> keyValPair)
      {
        return currentFileName;
      }
  
      @Override
      protected byte[] getBytesForTuple(KeyValPair<String, Integer> keyValPair)
      {
        return (keyValPair.toString() + "\n").getBytes();
      }
  
      @Override
      public void beginWindow(long windowId)
      {
        super.beginWindow(windowId);
        receivedTuples = false;
      }
  
      @Override
      protected void processTuple(KeyValPair<String, Integer> tuple)
      {
        super.processTuple(tuple);
        receivedTuples = true;
      }
  
      @Override
      public void endWindow()
      {
        super.endWindow();
        //request for finalization if there is no input. This is done automatically if the file is rotated periodically
        // or has a size threshold.
        if (!receivedTuples && !endOffsets.isEmpty()) {
          requestFinalize(currentFileName);
          part++;
          currentFileName = FILE_NAME_PREFIX + "." + part;
        }
      }
    }
  }
  