Giraph源码分析（七）—— 添加消息统计功能

作者|白松

1、 添加类，把每个超步发送的消息量大小写入Hadoop的Counter中。在org.apache.giraph.counters包下新建GiraphMessages类，来统计消息量。

源代码如下：

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();
    }
}

2、在BspServiceMaster类中添加统计功能。Master在每次同步时候，会聚集每个Worker发送的消息量大小（求和），存储于GlobalStats中。因此只需要在每次同步后，从GlobalStats对象中取出总的通信量大小，然后写入GiraphMessages中。格式为<SuperStep-Number，TotalMessagesCount>，实际存储于上步GiraphMessages类中定义的Map<Long, GiraphHadoopCounter> superstepMessages 对象中。 在BspServiceMaster的构造方法中，最后面追加一行代码，对GiraphMessages进行初始化。

GiraphMessages.init(context);

在BspServiceMaster类的SuperstepState coordinateSuperstep()方法中，添加记录功能。片段代码如下：

……
// 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");
//添加下面语句。从第0个超步起开始记录。
if(getSuperstep() != INPUT_SUPERSTEP) {
    GiraphMessages.getInstance().getSuperstepMessages(getSuperstep()).increment(globalStats.getMessageCount());
}
……

3、实验结果如下：

完！