org.apache.mahout.cf.taste.hadoop.als.MultithreadedSharingMapper 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.mahout.cf.taste.hadoop.als;
import com.google.common.base.Preconditions;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.mapreduce.JobContext;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.lib.map.MultithreadedMapper;
import org.apache.hadoop.util.ReflectionUtils;
import java.io.IOException;
/**
* Multithreaded Mapper for {@link SharingMapper}s. Will call setupSharedInstance() once in the controlling thread
* before executing the mappers using a thread pool.
*
* @param
* @param
* @param
* @param
*/
public class MultithreadedSharingMapper extends MultithreadedMapper {
@Override
public void run(Context ctx) throws IOException, InterruptedException {
Class> mapperClass =
MultithreadedSharingMapper.getMapperClass((JobContext) ctx);
Preconditions.checkNotNull(mapperClass, "Could not find Multithreaded Mapper class.");
Configuration conf = ctx.getConfiguration();
// instantiate the mapper
Mapper mapper1 = ReflectionUtils.newInstance(mapperClass, conf);
SharingMapper mapper = null;
if (mapper1 instanceof SharingMapper) {
mapper = (SharingMapper) mapper1;
}
Preconditions.checkNotNull(mapper, "Could not instantiate SharingMapper. Class was: %s",
mapper1.getClass().getName());
// single threaded call to setup the sharing mapper
mapper.setupSharedInstance(ctx);
// multithreaded execution
super.run(ctx);
}
}