org.apache.crunch.impl.spark.fn.CombineMapsideFunction.java Source code

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Here is the source code for org.apache.crunch.impl.spark.fn.CombineMapsideFunction.java

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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.crunch.impl.spark.fn;

import com.google.common.base.Function;
import com.google.common.collect.HashMultimap;
import com.google.common.collect.Iterables;
import com.google.common.collect.Maps;
import com.google.common.collect.Multimap;
import org.apache.crunch.CombineFn;
import org.apache.crunch.Pair;
import org.apache.crunch.impl.mem.emit.InMemoryEmitter;
import org.apache.crunch.impl.spark.SparkRuntimeContext;
import org.apache.spark.api.java.function.FlatMapFunction;
import org.apache.spark.api.java.function.PairFlatMapFunction;
import scala.Tuple2;

import javax.annotation.Nullable;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class CombineMapsideFunction<K, V> extends PairFlatMapFunction<Iterator<Tuple2<K, V>>, K, V> {

    private static final int REDUCE_EVERY_N = 50000;

    private final CombineFn<K, V> combineFn;
    private final SparkRuntimeContext ctxt;

    public CombineMapsideFunction(CombineFn<K, V> combineFn, SparkRuntimeContext ctxt) {
        this.combineFn = combineFn;
        this.ctxt = ctxt;
    }

    @Override
    public Iterable<Tuple2<K, V>> call(Iterator<Tuple2<K, V>> iter) throws Exception {
        ctxt.initialize(combineFn);
        Multimap<K, V> cache = HashMultimap.create();
        int cnt = 0;
        while (iter.hasNext()) {
            Tuple2<K, V> t = iter.next();
            cache.put(t._1, t._2);
            cnt++;
            if (cnt % REDUCE_EVERY_N == 0) {
                cache = reduce(cache);
            }
        }

        return Iterables.transform(reduce(cache).entries(), new Function<Map.Entry<K, V>, Tuple2<K, V>>() {
            @Override
            public Tuple2<K, V> apply(Map.Entry<K, V> input) {
                return new Tuple2<K, V>(input.getKey(), input.getValue());
            }
        });
    }

    private Multimap<K, V> reduce(Multimap<K, V> cache) {
        Set<K> keys = cache.keySet();
        Multimap<K, V> res = HashMultimap.create(keys.size(), keys.size());
        for (K key : keys) {
            for (Pair<K, V> p : reduce(key, cache.get(key))) {
                res.put(p.first(), p.second());
            }
        }
        return res;
    }

    private List<Pair<K, V>> reduce(K key, Iterable<V> values) {
        InMemoryEmitter<Pair<K, V>> emitter = new InMemoryEmitter<Pair<K, V>>();
        combineFn.process(Pair.of(key, values), emitter);
        combineFn.cleanup(emitter);
        return emitter.getOutput();
    }
}