/**
* 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.avro.mapreduce;
import org.apache.avro.Schema;
import org.apache.avro.generic.GenericData;
import org.apache.avro.hadoop.io.AvroKeyComparator;
import org.apache.avro.hadoop.io.AvroSerialization;
import org.apache.avro.mapred.AvroKey;
import org.apache.avro.mapred.AvroValue;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.mapreduce.Job;
/**
* Utility methods for configuring jobs that work with Avro.
*
* <p>When using Avro data as MapReduce keys and values, data must be wrapped in a
* suitable AvroWrapper implementation. MapReduce keys must be wrapped in an AvroKey
* object, and MapReduce values must be wrapped in an AvroValue object.</p>
*
* <p>Suppose you would like to write a line count mapper that reads from a text file. If
* instead of using a Text and IntWritable output value, you would like to use Avro data
* with a schema of <i>"string"</i> and <i>"int"</i>, respectively, you may parameterize
* your mapper with {@code AvroKey<CharSequence>} and {@code AvroValue<Integer>}
* types. Then, use the <code>setMapOutputKeySchema()</code> and
* <code>setMapOutputValueSchema()</code> methods to set writer schemas for the records
* you will generate.</p>
*/
public final class AvroJob {
/** Disable the constructor for this utility class. */
private AvroJob() {}
/** Configuration key for the input key schema. */
private static final String CONF_INPUT_KEY_SCHEMA = "avro.schema.input.key";
/** Configuration key for the input value schema. */
private static final String CONF_INPUT_VALUE_SCHEMA = "avro.schema.input.value";
/** Configuration key for the output key schema. */
private static final String CONF_OUTPUT_KEY_SCHEMA = "avro.schema.output.key";
/** Configuration key for the output value schema. */
private static final String CONF_OUTPUT_VALUE_SCHEMA = "avro.schema.output.value";
/** The configuration key for a job's output compression codec.
* This takes one of the strings registered in {@link org.apache.avro.file.CodecFactory} */
public static final String CONF_OUTPUT_CODEC = "avro.output.codec";
/**
* Sets the job input key schema.
*
* @param job The job to configure.
* @param schema The input key schema.
*/
public static void setInputKeySchema(Job job, Schema schema) {
job.getConfiguration().set(CONF_INPUT_KEY_SCHEMA, schema.toString());
}
/**
* Sets the job input value schema.
*
* @param job The job to configure.
* @param schema The input value schema.
*/
public static void setInputValueSchema(Job job, Schema schema) {
job.getConfiguration().set(CONF_INPUT_VALUE_SCHEMA, schema.toString());
}
/**
* Sets the map output key schema.
*
* @param job The job to configure.
* @param schema The map output key schema.
*/
public static void setMapOutputKeySchema(Job job, Schema schema) {
job.setMapOutputKeyClass(AvroKey.class);
job.setGroupingComparatorClass(AvroKeyComparator.class);
job.setSortComparatorClass(AvroKeyComparator.class);
AvroSerialization.setKeyWriterSchema(job.getConfiguration(), schema);
AvroSerialization.setKeyReaderSchema(job.getConfiguration(), schema);
AvroSerialization.addToConfiguration(job.getConfiguration());
}
/**
* Sets the map output value schema.
*
* @param job The job to configure.
* @param schema The map output value schema.
*/
public static void setMapOutputValueSchema(Job job, Schema schema) {
job.setMapOutputValueClass(AvroValue.class);
AvroSerialization.setValueWriterSchema(job.getConfiguration(), schema);
AvroSerialization.setValueReaderSchema(job.getConfiguration(), schema);
AvroSerialization.addToConfiguration(job.getConfiguration());
}
/**
* Sets the job output key schema.
*
* @param job The job to configure.
* @param schema The job output key schema.
*/
public static void setOutputKeySchema(Job job, Schema schema) {
job.setOutputKeyClass(AvroKey.class);
job.getConfiguration().set(CONF_OUTPUT_KEY_SCHEMA, schema.toString());
}
/**
* Sets the job output value schema.
*
* @param job The job to configure.
* @param schema The job output value schema.
*/
public static void setOutputValueSchema(Job job, Schema schema) {
job.setOutputValueClass(AvroValue.class);
job.getConfiguration().set(CONF_OUTPUT_VALUE_SCHEMA, schema.toString());
}
/**
* Sets the job data model class.
*
* @param job The job to configure.
* @param modelClass The job data model class.
*/
public static void setDataModelClass(Job job, Class<? extends GenericData> modelClass) {
AvroSerialization.setDataModelClass(job.getConfiguration(), modelClass);
}
/**
* Gets the job input key schema.
*
* @param conf The job configuration.
* @return The job input key schema, or null if not set.
*/
public static Schema getInputKeySchema(Configuration conf) {
String schemaString = conf.get(CONF_INPUT_KEY_SCHEMA);
return schemaString != null ? Schema.parse(schemaString) : null;
}
/**
* Gets the job input value schema.
*
* @param conf The job configuration.
* @return The job input value schema, or null if not set.
*/
public static Schema getInputValueSchema(Configuration conf) {
String schemaString = conf.get(CONF_INPUT_VALUE_SCHEMA);
return schemaString != null ? Schema.parse(schemaString) : null;
}
/**
* Gets the map output key schema.
*
* @param conf The job configuration.
* @return The map output key schema, or null if not set.
*/
public static Schema getMapOutputKeySchema(Configuration conf) {
return AvroSerialization.getKeyWriterSchema(conf);
}
/**
* Gets the map output value schema.
*
* @param conf The job configuration.
* @return The map output value schema, or null if not set.
*/
public static Schema getMapOutputValueSchema(Configuration conf) {
return AvroSerialization.getValueWriterSchema(conf);
}
/**
* Gets the job output key schema.
*
* @param conf The job configuration.
* @return The job output key schema, or null if not set.
*/
public static Schema getOutputKeySchema(Configuration conf) {
String schemaString = conf.get(CONF_OUTPUT_KEY_SCHEMA);
return schemaString != null ? Schema.parse(schemaString) : null;
}
/**
* Gets the job output value schema.
*
* @param conf The job configuration.
* @return The job output value schema, or null if not set.
*/
public static Schema getOutputValueSchema(Configuration conf) {
String schemaString = conf.get(CONF_OUTPUT_VALUE_SCHEMA);
return schemaString != null ? Schema.parse(schemaString) : null;
}
}