Hadoop Counter

忘是亡心i 2022-08-23 01:22 166阅读 0赞

Hadoop Counte是Hadoop自带的一个很实用的功能，它可以统计全局某个量的数量，如，MR中用Kafka发送消息，就可以用Hadoop Counter统计发送成功信息的条数、发送失败信息的条数，以及发送信息的总条数。其实我们每个MapReduce Job跑完都有Counter打印：

16/06/05 00:25:19 INFO mapreduce.Job: Counters: 50
    File System Counters
    	FILE: Number of bytes read=42
    	FILE: Number of bytes written=185609
    	FILE: Number of read operations=0
    	FILE: Number of large read operations=0
    	FILE: Number of write operations=0
    	HDFS: Number of bytes read=139
    	HDFS: Number of bytes written=8
    	HDFS: Number of read operations=6
    	HDFS: Number of large read operations=0
    	HDFS: Number of write operations=2
    Job Counters 
    	Launched map tasks=1
    	Launched reduce tasks=1
    	Data-local map tasks=1
    	Total time spent by all maps in occupied slots (ms)=3585
    	Total time spent by all reduces in occupied slots (ms)=3174
    	Total time spent by all map tasks (ms)=3585
    	Total time spent by all reduce tasks (ms)=3174
    	Total vcore-seconds taken by all map tasks=3585
    	Total vcore-seconds taken by all reduce tasks=3174
    	Total megabyte-seconds taken by all map tasks=3671040
    	Total megabyte-seconds taken by all reduce tasks=3250176
    Map-Reduce Framework
    	Map input records=3
    	Map output records=3
    	Map output bytes=30
    	Map output materialized bytes=42
    	Input split bytes=102
    	Combine input records=0
    	Combine output records=0
    	Reduce input groups=1
    	Reduce shuffle bytes=42
    	Reduce input records=3
    	Reduce output records=1
    	Spilled Records=6
    	Shuffled Maps =1
    	Failed Shuffles=0
    	Merged Map outputs=1
    	GC time elapsed (ms)=190
    	CPU time spent (ms)=1310
    	Physical memory (bytes) snapshot=218619904
    	Virtual memory (bytes) snapshot=725868544
    	Total committed heap usage (bytes)=136908800
    Hello_Counter
    	Number=3
    Shuffle Errors
    	BAD_ID=0
    	CONNECTION=0
    	IO_ERROR=0
    	WRONG_LENGTH=0
    	WRONG_MAP=0
    	WRONG_REDUCE=0
    File Input Format Counters 
    	Bytes Read=37
    File Output Format Counters 
    	Bytes Written=8

而每个Counter又属于一个Counter Group。如上：

1.  16/06/05 00:25:19 INFO mapreduce.Job: Counters: 50：表示一共有50个Counter。
2.  File System Counters、Job Counters、Map-Reduce Framework等就是Counter Group。
3.  FILE: Number of bytes read=42、Launched map tasks=1等这些分布于每个Counter Group下的就是该Group中的Counter。

下面就用简单的WordCount作为例子，统计“Hello”的个数：

import java.io.IOException;
    import java.util.StringTokenizer;
     
    import org.apache.hadoop.conf.Configuration;
    import org.apache.hadoop.fs.Path;
    import org.apache.hadoop.io.IntWritable;
    import org.apache.hadoop.io.Text;
    import org.apache.hadoop.mapreduce.Counter;
    import org.apache.hadoop.mapreduce.Job;
    import org.apache.hadoop.mapreduce.Mapper;
    import org.apache.hadoop.mapreduce.Reducer;
    import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
    import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
    import org.apache.hadoop.util.GenericOptionsParser;
    
    public class WordCount
    {
    
    	public static class TokenizerMapper 
    		extends Mapper<Object, Text, Text, IntWritable>
    	{
    
    		private final static IntWritable one = new IntWritable(1);
    		private Text word = new Text();
            public static String COUNT = "Hello_Counter";
            public static String NUMB = "Number";
    
            public void map(Object key, Text value, Context context
    			) throws IOException, InterruptedException
    		{
    			String[] line = value.toString().trim().split(" ");
    			for(String itr : line){
    				word.set(itr);
                    if(itr.trim().equals("hello")){
                        context.getCounter(COUNT, NUMB).increment(1);
                        context.write(word, one);
                    }
                }
    		}
    	}
    
    	public static class IntSumReducer 
    		extends Reducer<Text,IntWritable,Text,IntWritable> 
    	{
    		private IntWritable result = new IntWritable();
    
    
    		public void reduce(Text key, Iterable<IntWritable> values, 
    			Context context) throws IOException, InterruptedException
    		{
    			int sum = 0;
    			for (IntWritable val : values) 
    			{
    				sum += val.get();
    			}
    
    			result.set(sum);
    			context.write(key, result);
    		}
    	}
    
    	public static void main(String[] args) throws Exception {
    		Configuration conf = new Configuration();
    		String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
    		if (otherArgs.length != 2) {
    			System.err.println("Usage: wordcount <in> <out>");
    			System.exit(2);
    		}
    		@SuppressWarnings("deprecation")
    		Job job = new Job(conf, "word count");
    		job.setJarByClass(WordCount.class);
    		job.setMapperClass(TokenizerMapper.class);
    		job.setReducerClass(IntSumReducer.class);
    		job.setOutputKeyClass(Text.class);
    		job.setOutputValueClass(IntWritable.class);
    		FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
    		FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));
            job.waitForCompletion(true);
    
    //        Counter count = job.getCounters().findCounter(TokenizerMapper.COUNT, TokenizerMapper.NUMB);
            Counter count = job.getCounters().getGroup(TokenizerMapper.COUNT).findCounter(TokenizerMapper.NUMB);
            System.out.println("==============" + count.getValue());
        }
    }

至于Counter更多API的使用请参考 [Hadoop Javadoc][]。

输出：

16/06/05 00:24:55 INFO client.RMProxy: Connecting to ResourceManager at slave-1/192.168.253.11:8032
    16/06/05 00:24:56 INFO input.FileInputFormat: Total input paths to process : 1
    16/06/05 00:24:56 INFO mapreduce.JobSubmitter: number of splits:1
    16/06/05 00:24:56 INFO mapreduce.JobSubmitter: Submitting tokens for job: job_1465111446224_0001
    16/06/05 00:24:57 INFO impl.YarnClientImpl: Submitted application application_1465111446224_0001
    16/06/05 00:24:58 INFO mapreduce.Job: The url to track the job: http://slave-1:8088/proxy/application_1465111446224_0001/
    16/06/05 00:24:58 INFO mapreduce.Job: Running job: job_1465111446224_0001
    16/06/05 00:25:08 INFO mapreduce.Job: Job job_1465111446224_0001 running in uber mode : false
    16/06/05 00:25:08 INFO mapreduce.Job:  map 0% reduce 0%
    16/06/05 00:25:14 INFO mapreduce.Job:  map 100% reduce 0%
    16/06/05 00:25:19 INFO mapreduce.Job:  map 100% reduce 100%
    16/06/05 00:25:19 INFO mapreduce.Job: Job job_1465111446224_0001 completed successfully
    16/06/05 00:25:19 INFO mapreduce.Job: Counters: 50
    File System Counters
    	FILE: Number of bytes read=42
    	FILE: Number of bytes written=185609
    	FILE: Number of read operations=0
    	FILE: Number of large read operations=0
    	FILE: Number of write operations=0
    	HDFS: Number of bytes read=139
    	HDFS: Number of bytes written=8
    	HDFS: Number of read operations=6
    	HDFS: Number of large read operations=0
    	HDFS: Number of write operations=2
    Job Counters 
    	Launched map tasks=1
    	Launched reduce tasks=1
    	Data-local map tasks=1
    	Total time spent by all maps in occupied slots (ms)=3585
    	Total time spent by all reduces in occupied slots (ms)=3174
    	Total time spent by all map tasks (ms)=3585
    	Total time spent by all reduce tasks (ms)=3174
    	Total vcore-seconds taken by all map tasks=3585
    	Total vcore-seconds taken by all reduce tasks=3174
    	Total megabyte-seconds taken by all map tasks=3671040
    	Total megabyte-seconds taken by all reduce tasks=3250176
    Map-Reduce Framework
    	Map input records=3
    	Map output records=3
    	Map output bytes=30
    	Map output materialized bytes=42
    	Input split bytes=102
    	Combine input records=0
    	Combine output records=0
    	Reduce input groups=1
    	Reduce shuffle bytes=42
    	Reduce input records=3
    	Reduce output records=1
    	Spilled Records=6
    	Shuffled Maps =1
    	Failed Shuffles=0
    	Merged Map outputs=1
    	GC time elapsed (ms)=190
    	CPU time spent (ms)=1310
    	Physical memory (bytes) snapshot=218619904
    	Virtual memory (bytes) snapshot=725868544
    	Total committed heap usage (bytes)=136908800
    Hello_Counter
    	Number=3
    Shuffle Errors
    	BAD_ID=0
    	CONNECTION=0
    	IO_ERROR=0
    	WRONG_LENGTH=0
    	WRONG_MAP=0
    	WRONG_REDUCE=0
    File Input Format Counters 
    	Bytes Read=37
    File Output Format Counters 
    	Bytes Written=8
    ==============3

如输出中的Counter Group：Hello\_Counter，Counter：Number=3

**注意：有些Hadoop版本不会把自定义的Counter和File System Counters、Job Counters并列地列在一起，所以建议最后还是自己打印出来比较好。**

[Hadoop Javadoc]: https://hadoop.apache.org/docs/r2.6.3/api/org/apache/hadoop/mapred/Counters.Counter.html