SpoutOutputCollector.java

// Copyright 2016 Twitter. All rights reserved.
//
// 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 com.twitter.heron.api.spout;

import java.util.List;

import com.twitter.heron.api.utils.Utils;

/**
 * This output collector exposes the API for emitting tuples from an
 * {@link com.twitter.heron.api.spout.IRichSpout}.
 * The main difference between this output collector and
 * {@link com.twitter.heron.api.bolt.OutputCollector}
 * for {@link com.twitter.heron.api.bolt.IRichBolt} is that spouts
 * can tag messages with ids so that they can be
 * acked or failed later on. This is the Spout portion of Heron's API to
 * guarantee that each message is fully processed at least once.
 */
public class SpoutOutputCollector implements ISpoutOutputCollector {
  private ISpoutOutputCollector delegate;

  public SpoutOutputCollector(ISpoutOutputCollector aDelegate) {
    delegate = aDelegate;
  }

  /**
   * Emits a new tuple to the specified output stream with the given message ID.
   * When Heron detects that this tuple has been fully processed, or has failed
   * to be fully processed, the spout will receive an ack or fail callback respectively
   * with the messageId as long as the messageId was not null. If the messageId was null,
   * Heron will not track the tuple and no callback will be received. The emitted values must be
   * immutable.
   *
   * @return the list of task ids that this tuple was sent to
   */
  public List<Integer> emit(String streamId, List<Object> tuple, Object messageId) {
    return delegate.emit(streamId, tuple, messageId);
  }

  /**
   * Emits a new tuple to the default output stream with the given message ID.
   * When Heron detects that this tuple has been fully processed, or has failed
   * to be fully processed, the spout will receive an ack or fail callback respectively
   * with the messageId as long as the messageId was not null. If the messageId was null,
   * Heron will not track the tuple and no callback will be received. The emitted values must be
   * immutable.
   *
   * @return the list of task ids that this tuple was sent to
   */
  public List<Integer> emit(List<Object> tuple, Object messageId) {
    return emit(Utils.DEFAULT_STREAM_ID, tuple, messageId);
  }

  /**
   * Emits a tuple to the default output stream with a null message id. Heron will
   * not track this message so ack and fail will never be called for this tuple. The
   * emitted values must be immutable.
   */
  public List<Integer> emit(List<Object> tuple) {
    return emit(tuple, null);
  }

  /**
   * Emits a tuple to the specified output stream with a null message id. Heron will
   * not track this message so ack and fail will never be called for this tuple. The
   * emitted values must be immutable.
   */
  public List<Integer> emit(String streamId, List<Object> tuple) {
    return emit(streamId, tuple, null);
  }

  /**
   * Emits a tuple to the specified task on the specified output stream. This output
   * stream must have been declared as a direct stream, and the specified task must
   * use a direct grouping on this stream to receive the message. The emitted values must be
   * immutable.
   */
  public void emitDirect(int taskId, String streamId, List<Object> tuple, Object messageId) {
    delegate.emitDirect(taskId, streamId, tuple, messageId);
  }

  /**
   * Emits a tuple to the specified task on the default output stream. This output
   * stream must have been declared as a direct stream, and the specified task must
   * use a direct grouping on this stream to receive the message. The emitted values must be
   * immutable.
   */
  public void emitDirect(int taskId, List<Object> tuple, Object messageId) {
    emitDirect(taskId, Utils.DEFAULT_STREAM_ID, tuple, messageId);
  }

  /**
   * Emits a tuple to the specified task on the specified output stream. This output
   * stream must have been declared as a direct stream, and the specified task must
   * use a direct grouping on this stream to receive the message. The emitted values must be
   * immutable.
   * <p>
   * <p> Because no message id is specified, Heron will not track this message
   * so ack and fail will never be called for this tuple.</p>
   */
  public void emitDirect(int taskId, String streamId, List<Object> tuple) {
    emitDirect(taskId, streamId, tuple, null);
  }

  /**
   * Emits a tuple to the specified task on the default output stream. This output
   * stream must have been declared as a direct stream, and the specified task must
   * use a direct grouping on this stream to receive the message. The emitted values must be
   * immutable.
   * <p>
   * <p> Because no message id is specified, Heron will not track this message
   * so ack and fail will never be called for this tuple.</p>
   */
  public void emitDirect(int taskId, List<Object> tuple) {
    emitDirect(taskId, tuple, null);
  }

  @Override
  public void reportError(Throwable error) {
    delegate.reportError(error);
  }
}