| /** |
| * 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. |
| */ |
| void emitTuples(); |
| |
| } |