Giraph源碼分析（七）—— 添加消息統計功能

做者|白松

一、 添加類，把每一個超步發送的消息量大小寫入Hadoop的Counter中。在org.apache.giraph.counters包下新建GiraphMessages類，來統計消息量。

源代碼以下：

package org.apache.giraph.counters;

import java.util.Iterator;
import java.util.Map;

import org.apache.hadoop.mapreduce.Mapper.Context;
import com.google.common.collect.Maps;

/**
 * Hadoop Counters in group "Giraph Messages" for counting every superstep
 * message count.
 */
public class GiraphMessages extends HadoopCountersBase {
    /** Counter group name for the giraph Messages */
    public static final String GROUP_NAME = "Giraph Messages";

    /** Singleton instance for everyone to use */
    private static GiraphMessages INSTANCE;

    /** superstep time in msec */
    private final Map superstepMessages;

    private GiraphMessages(Context context) {
        super(context, GROUP_NAME);
        superstepMessages = Maps.newHashMap();
    }

    /**
     * Instantiate with Hadoop Context.
     * 
     * @param context
     *            Hadoop Context to use.
     */
    public static void init(Context context) {
        INSTANCE = new GiraphMessages(context);
    }

    /**
     * Get singleton instance.
     * 
     * @return singleton GiraphTimers instance.
     */
    public static GiraphMessages getInstance() {
        return INSTANCE;
    }

    /**
     * Get counter for superstep messages
     * 
     * @param superstep
     * @return
     */
    public GiraphHadoopCounter getSuperstepMessages(long superstep) {
        GiraphHadoopCounter counter = superstepMessages.get(superstep);
        if (counter == null) {
            String counterPrefix = "Superstep- " + superstep+" ";
            counter = getCounter(counterPrefix);
            superstepMessages.put(superstep, counter);
        }
        return counter;
    }

    @Override
    public Iterator iterator() {
        return superstepMessages.values().iterator();
    }
}

二、在BspServiceMaster類中添加統計功能。Master在每次同步時候，會彙集每一個Worker發送的消息量大小（求和），存儲於GlobalStats中。所以只須要在每次同步後，從GlobalStats對象中取出總的通訊量大小，而後寫入GiraphMessages中。格式爲<SuperStep-Number，TotalMessagesCount>，實際存儲於上步GiraphMessages類中定義的Map<Long, GiraphHadoopCounter> superstepMessages 對象中。 在BspServiceMaster的構造方法中，最後面追加一行代碼，對GiraphMessages進行初始化。

GiraphMessages.init(context);

在BspServiceMaster類的SuperstepState coordinateSuperstep()方法中，添加記錄功能。片斷代碼以下：

……
// If the master is halted or all the vertices voted to halt and there
// are no more messages in the system, stop the computation
GlobalStats globalStats = aggregateWorkerStats(getSuperstep());  

LOG.info("D-globalStats: "+globalStats+"\n\n");
//添加下面語句。從第0個超步起開始記錄。
if(getSuperstep() != INPUT_SUPERSTEP) {
    GiraphMessages.getInstance().getSuperstepMessages(getSuperstep()).increment(globalStats.getMessageCount());
}
……

三、實驗結果以下：

完！