com.datatorrent.api.InputOperator Maven / Gradle / Ivy
/**
* 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 com.datatorrent.api;
/**
* Input operators ie operators which do not consume payload from other operators but are able
* to generate the payload for other operators must implement this interface.
*
* It's an error to provide input ports on operators which implement this interface since existence
* of ports contradicts with the purpose of the interface.
*
* @since 0.3.2
*/
public interface InputOperator extends Operator
{
/**
* The input operators are given an opportunity to emit the tuples which will be marked
* as belonging to the windowId identified by immediately preceding beginWindow call.
*
* emitTuples can implement one or more tuples. Ideally it should emit as many tuples as
* possible without going over the streaming window width boundary. Since operators can
* easily spend too much time making that check, when not convenient they should emit
* only as many tuples as they can confidently within the current window. The streaming
* engine will make sure to call emitTuples multiple times within a giving streaming
* window if it can. When it cannot, it will call endWindow.
*/
public void emitTuples();
}