/*
* Copyright 2010-2013 10gen Inc.
*
* Licensed 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 com.mongodb.hadoop.splitter;
import com.mongodb.MongoClientURI;
import com.mongodb.hadoop.input.MongoInputSplit;
import com.mongodb.hadoop.util.MongoConfigUtil;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.mapreduce.InputSplit;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
/**
* This implementation of MongoSplitter can be used for sharded systems. It treats each shard as a single split, by reading all of the data
* on each shard for that split. This should be used with caution as the input splits could contain duplicate data from ongoing, or aborted
* migrations.
*/
public class ShardMongoSplitter extends MongoCollectionSplitter {
public ShardMongoSplitter() {
}
public ShardMongoSplitter(final Configuration conf) {
super(conf);
}
// Treat each shard as one split.
@Override
public List<InputSplit> calculateSplits() throws SplitFailedException {
this.init();
final ArrayList<InputSplit> returnVal = new ArrayList<InputSplit>();
MongoClientURI inputURI = MongoConfigUtil.getInputURI(getConfiguration());
Map<String, String> shardsMap;
shardsMap = this.getShardsMap();
for (Map.Entry<String, String> entry : shardsMap.entrySet()) {
String shardHosts = entry.getValue();
MongoInputSplit chunkSplit = createSplitFromBounds(null, null);
chunkSplit.setInputURI(rewriteURI(inputURI, shardHosts));
returnVal.add(chunkSplit);
}
return returnVal;
}
}