DatumOutputEmitter.java

/*
 * Copyright © 2014 Cask Data, Inc.
 *
 * Licensed 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 co.cask.cdap.internal.app.runtime.flow;

import co.cask.cdap.api.data.schema.Schema;
import co.cask.cdap.api.flow.flowlet.OutputEmitter;
import co.cask.cdap.common.io.BinaryEncoder;
import co.cask.cdap.data2.queue.QueueEntry;
import co.cask.cdap.data2.queue.QueueProducer;
import co.cask.cdap.internal.io.DatumWriter;
import com.google.common.base.Function;
import com.google.common.base.Supplier;
import com.google.common.base.Throwables;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Maps;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.Map;
import javax.annotation.Nullable;

/**
 * @param <T>
 */
public final class DatumOutputEmitter<T> implements OutputEmitter<T> {

  public static final Function<Object, Integer> PARTITION_MAP_TRANSFORMER = new PartitionMapTransformer();

  private final Supplier<QueueProducer> producerSupplier;
  private final byte[] schemaHash;
  private final DatumWriter<T> writer;

  public DatumOutputEmitter(Supplier<QueueProducer> producerSupplier, Schema schema, DatumWriter<T> writer) {
    this.producerSupplier = producerSupplier;
    this.schemaHash = schema.getSchemaHash().toByteArray();
    this.writer = writer;
  }

  @Override
  public void emit(T data) {
    emit(data, ImmutableMap.<String, Object>of());
  }

  @Override
  public void emit(T data, String partitionKey, Object partitionValue) {
    emit(data, ImmutableMap.of(partitionKey, partitionValue));
  }

  @Override
  public void emit(T data, Map<String, Object> partitions) {
    try {
      ByteArrayOutputStream output = new ByteArrayOutputStream();
      output.write(schemaHash);
      writer.encode(data, new BinaryEncoder(output));
      producerSupplier.get().enqueue(new QueueEntry(Maps.transformValues(partitions, PARTITION_MAP_TRANSFORMER),
                                                    output.toByteArray()));
    } catch (IOException e) {
      throw Throwables.propagate(e);
    }
  }

  private static final class PartitionMapTransformer implements Function<Object, Integer> {
    @Override
    public Integer apply(@Nullable Object input) {
      return input == null ? 0 : input.hashCode();
    }
  }
}