org.apache.hadoop.mapreduce.OutputFormat 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 org.apache.hadoop.mapreduce;
import java.io.IOException;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.fs.FileSystem;
/**
* OutputFormat describes the output-specification for a
* Map-Reduce job.
*
* The Map-Reduce framework relies on the OutputFormat of the
* job to:
*
* -
* Validate the output-specification of the job. For e.g. check that the
* output directory doesn't already exist.
*
-
* Provide the {@link RecordWriter} implementation to be used to write out
* the output files of the job. Output files are stored in a
* {@link FileSystem}.
*
*
*
* @see RecordWriter
*/
@InterfaceAudience.Public
@InterfaceStability.Stable
public abstract class OutputFormat {
/**
* Get the {@link RecordWriter} for the given task.
*
* @param context the information about the current task.
* @return a {@link RecordWriter} to write the output for the job.
* @throws IOException
*/
public abstract RecordWriter
getRecordWriter(TaskAttemptContext context
) throws IOException, InterruptedException;
/**
* Check for validity of the output-specification for the job.
*
* This is to validate the output specification for the job when it is
* a job is submitted. Typically checks that it does not already exist,
* throwing an exception when it already exists, so that output is not
* overwritten.
*
* @param context information about the job
* @throws IOException when output should not be attempted
*/
public abstract void checkOutputSpecs(JobContext context
) throws IOException,
InterruptedException;
/**
* Get the output committer for this output format. This is responsible
* for ensuring the output is committed correctly.
* @param context the task context
* @return an output committer
* @throws IOException
* @throws InterruptedException
*/
public abstract
OutputCommitter getOutputCommitter(TaskAttemptContext context
) throws IOException, InterruptedException;
}