org.apache.hadoop.mapred.pipes.DownwardProtocol Maven / Gradle / Ivy
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* 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.hadoop.mapred.pipes;
import java.io.IOException;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.mapred.InputSplit;
import org.apache.hadoop.mapred.JobConf;
/**
* The abstract description of the downward (from Java to C++) Pipes protocol.
* All of these calls are asynchronous and return before the message has been
* processed.
*/
interface DownwardProtocol {
/**
* request authentication
* @throws IOException
*/
void authenticate(String digest, String challenge) throws IOException;
/**
* Start communication
* @throws IOException
*/
void start() throws IOException;
/**
* Set the JobConf for the task.
* @param conf
* @throws IOException
*/
void setJobConf(JobConf conf) throws IOException;
/**
* Set the input types for Maps.
* @param keyType the name of the key's type
* @param valueType the name of the value's type
* @throws IOException
*/
void setInputTypes(String keyType, String valueType) throws IOException;
/**
* Run a map task in the child.
* @param split The input split for this map.
* @param numReduces The number of reduces for this job.
* @param pipedInput Is the input coming from Java?
* @throws IOException
*/
void runMap(InputSplit split, int numReduces,
boolean pipedInput) throws IOException;
/**
* For maps with pipedInput, the key/value pairs are sent via this messaage.
* @param key The record's key
* @param value The record's value
* @throws IOException
*/
void mapItem(K key, V value) throws IOException;
/**
* Run a reduce task in the child
* @param reduce the index of the reduce (0 .. numReduces - 1)
* @param pipedOutput is the output being sent to Java?
* @throws IOException
*/
void runReduce(int reduce, boolean pipedOutput) throws IOException;
/**
* The reduce should be given a new key
* @param key the new key
* @throws IOException
*/
void reduceKey(K key) throws IOException;
/**
* The reduce should be given a new value
* @param value the new value
* @throws IOException
*/
void reduceValue(V value) throws IOException;
/**
* The task has no more input coming, but it should finish processing it's
* input.
* @throws IOException
*/
void endOfInput() throws IOException;
/**
* The task should stop as soon as possible, because something has gone wrong.
* @throws IOException
*/
void abort() throws IOException;
/**
* Flush the data through any buffers.
*/
void flush() throws IOException;
/**
* Close the connection.
*/
void close() throws IOException, InterruptedException;
}