| /* |
| * 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 org.apache.nemo.runtime.executor.task; |
| |
| import org.apache.nemo.common.ir.OutputCollector; |
| import org.apache.nemo.common.ir.vertex.IRVertex; |
| |
| import java.io.IOException; |
| import java.util.NoSuchElementException; |
| |
| /** |
| * An abstraction for fetching data from task-external sources. |
| */ |
| abstract class DataFetcher implements AutoCloseable { |
| private final IRVertex dataSource; |
| private final OutputCollector outputCollector; |
| |
| /** |
| * @param dataSource to fetch from. |
| * @param outputCollector for the data fetched. |
| */ |
| DataFetcher(final IRVertex dataSource, |
| final OutputCollector outputCollector) { |
| this.dataSource = dataSource; |
| this.outputCollector = outputCollector; |
| } |
| |
| /** |
| * Can block until the next data element becomes available. |
| * |
| * @return data element |
| * @throws IOException upon I/O error |
| * @throws java.util.NoSuchElementException if no more element is available |
| */ |
| abstract Object fetchDataElement() throws IOException, NoSuchElementException; |
| |
| OutputCollector getOutputCollector() { |
| return outputCollector; |
| } |
| |
| IRVertex getDataSource() { |
| return dataSource; |
| } |
| } |