IComponent.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.topology;

import java.io.Serializable;
import java.util.Map;

/**
 * Common methods for all possible components in a topology. This interface is used
 * when defining topologies using the Java API.
 */
public interface IComponent extends Serializable {

  /**
   * Declare the output schema for all the streams of this topology.
   *
   * @param declarer this is used to declare output stream ids, output fields, and whether or not each output stream is a direct stream
   */
  void declareOutputFields(OutputFieldsDeclarer declarer);

  /**
   * Declare configuration specific to this component. Only a subset of the "topology.*" configs can
   * be overridden. The component configuration can be further overridden when constructing the
   * topology using {@link TopologyBuilder}
   */
  Map<String, Object> getComponentConfiguration();

}