org.apache.flink.streaming.runtime.partitioner.PartialPartitioner.java Source code

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Here is the source code for org.apache.flink.streaming.runtime.partitioner.PartialPartitioner.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.flink.streaming.runtime.partitioner;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;

import org.apache.flink.api.java.functions.KeySelector;
import org.apache.flink.runtime.plugable.SerializationDelegate;
import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
import com.google.common.hash.HashFunction;
import com.google.common.hash.Hashing;

/**
 * Partial Key Grouping maps each message to two of the n possible channels
 * (round robin maps to n channels, field grouping maps to 1 channel). Among the
 * two possible channels it forwards the key to least loaded (each source
 * maintains the list of past messages) of two channels.
 * 
 * @param <T>
 *            Type of the Tuple
 */

public class PartialPartitioner<T> extends StreamPartitioner<T> {
    private static final long serialVersionUID = 1L;
    private long[] targetChannelStats;
    KeySelector<T, ?> keySelector;
    private int[] returnArray = new int[1];
    private boolean initializedStats;
    private HashFunction[] h;
    private int workersPerKey = 2;
    private int currentPrime = 2;

    public PartialPartitioner(KeySelector<T, ?> keySelector) {
        this.initializedStats = false;
        this.keySelector = keySelector;
    }

    public PartialPartitioner(KeySelector<T, ?> keySelector, int numWorkersPerKey) {
        this.initializedStats = false;
        this.keySelector = keySelector;
        this.workersPerKey = numWorkersPerKey;
    }

    @Override
    public StreamPartitioner<T> copy() {
        return this;
    }

    private int getNextPrime(int x) {
        int num = x + 1;
        while (!isPrime(num)) {
            num++;
        }
        return num;
    }

    private boolean isPrime(int num) {
        for (int i = 2; i < num; i++) {
            if (num % i == 0) {
                return false;
            }
        }
        return true;
    }

    @Override
    public int[] selectChannels(SerializationDelegate<StreamRecord<T>> record, int numChannels) {
        if (!initializedStats) {
            this.targetChannelStats = new long[numChannels];
            this.initializedStats = true;
            h = new HashFunction[this.workersPerKey];
            for (int i = 0; i < this.workersPerKey; i++) {
                currentPrime = getNextPrime(currentPrime);
                h[i] = Hashing.murmur3_128(currentPrime);
            }
        }
        int[] choices;
        Object key;
        try {
            key = keySelector.getKey(record.getInstance().getValue());
            int counter = 0;
            choices = new int[this.workersPerKey];
            if (this.workersPerKey == numChannels) {
                while (counter < this.workersPerKey) {
                    choices[counter] = counter;
                    counter++;
                }
            } else {
                while (counter < this.workersPerKey) {
                    choices[counter] = (int) (Math.abs(h[counter].hashBytes(serialize(key)).asLong())
                            % numChannels);
                    counter++;
                }
            }
        } catch (Exception e) {
            throw new RuntimeException("Could not extract key from " + record.getInstance().getValue(), e);
        }
        int selected = selectMinWorker(targetChannelStats, choices);
        targetChannelStats[selected]++;

        returnArray[0] = selected;
        return returnArray;
    }

    private int selectMinWorker(long[] loadVector, int[] choice) {
        int index = choice[0];
        for (int i = 0; i < choice.length; i++) {
            if (loadVector[choice[i]] < loadVector[index]) {
                index = choice[i];
            }
        }
        return index;
    }

    private byte[] serialize(Object obj) throws IOException {
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        ObjectOutputStream os = new ObjectOutputStream(out);
        os.writeObject(obj);
        return out.toByteArray();
    }

    @Override
    public String toString() {
        return "PARTIAL";
    }
}