Hadoop快速入门

WordContent简单应用

Hadoop的HelloWorld程序

创建HDFS目录

hdfs命令位于bin目录下，通过hdfs dfs -mkdir命令可以创建一个目录。

[[email protected] hadoop-2.7.3]# bin/hdfs dfs -mkdir -p input

dfs创建的目录默认会放到/user/{username}/目录下面，其中{username}是当前用户名。所以input目录应该在/user/root/下面。

下面通过｀hdfs dfs -ls｀命令可以查看HDFS目录文件

[[email protected] hadoop-2.7.3]# bin/hdfs dfs -ls /

上传文件到HDFS

在本地新建一个文本文件

vi /root/words.txt

将本地文件/root/words.txt上传到HDFS

bin/hdfs dfs -put /root/words.txt input
bin/hdfs dfs -ls input

运行WordContent

执行下面命令：

bin/hadoop jar share/hadoop/mapreduce/hadoop-mapreduce-examples-2.7.3.jar wordcount input output

[[email protected] hadoop-2.7.3]# bin/hadoop jar share/hadoop/mapreduce/hadoop-mapreduce-examples-2.7.3.jar wordcount input output
18/11/22 08:37:53 INFO client.RMProxy: Connecting to ResourceManager at /0.0.0.0:8032
18/11/22 08:37:55 INFO input.FileInputFormat: Total input paths to process : 1
18/11/22 08:37:56 INFO mapreduce.JobSubmitter: number of splits:1
18/11/22 08:37:56 INFO mapreduce.JobSubmitter: Submitting tokens for job: job_1542892421463_0001
18/11/22 08:37:57 INFO impl.YarnClientImpl: Submitted application application_1542892421463_0001
18/11/22 08:37:57 INFO mapreduce.Job: The url to track the job: http://node1:8088/proxy/application_1542892421463_0001/
18/11/22 08:37:57 INFO mapreduce.Job: Running job: job_1542892421463_0001
18/11/22 08:39:05 INFO mapreduce.Job: Job job_1542892421463_0001 running in uber mode : false
18/11/22 08:39:05 INFO mapreduce.Job:  map 0% reduce 0%
18/11/22 08:39:53 INFO mapreduce.Job:  map 100% reduce 0%
18/11/22 08:40:27 INFO mapreduce.Job:  map 100% reduce 100%
18/11/22 08:40:30 INFO mapreduce.Job: Job job_1542892421463_0001 completed successfully
18/11/22 08:40:35 INFO mapreduce.Job: Counters: 49
        File System Counters
                FILE: Number of bytes read=51
                FILE: Number of bytes written=237319
                FILE: Number of read operations=0
                FILE: Number of large read operations=0
                FILE: Number of write operations=0
                HDFS: Number of bytes read=150
                HDFS: Number of bytes written=29
                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)=43701
                Total time spent by all reduces in occupied slots (ms)=28714
                Total time spent by all map tasks (ms)=43701
                Total time spent by all reduce tasks (ms)=28714
                Total vcore-milliseconds taken by all map tasks=43701
                Total vcore-milliseconds taken by all reduce tasks=28714
                Total megabyte-milliseconds taken by all map tasks=44749824
                Total megabyte-milliseconds taken by all reduce tasks=29403136
        Map-Reduce Framework
                Map input records=3
                Map output records=8
                Map output bytes=74
                Map output materialized bytes=51
                Input split bytes=108
                Combine input records=8
                Combine output records=4
                Reduce input groups=4
                Reduce shuffle bytes=51
                Reduce input records=4
                Reduce output records=4
                Spilled Records=8
                Shuffled Maps =1
                Failed Shuffles=0
                Merged Map outputs=1
                GC time elapsed (ms)=342
                CPU time spent (ms)=3420
                Physical memory (bytes) snapshot=283492352
                Virtual memory (bytes) snapshot=4202385408
                Total committed heap usage (bytes)=138788864
        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=42
        File Output Format Counters
                Bytes Written=29

查看结果

bin/hdfs dfs -ls output

bin/hdfs dfs -cat output/part-r-00000

[[email protected] hadoop-2.7.3]# bin/hdfs dfs -ls output
Found 2 items
-rw-r--r--   1 root supergroup          0 2018-11-22 08:40 output/_SUCCESS
-rw-r--r--   1 root supergroup         29 2018-11-22 08:40 output/part-r-00000
[[email protected] hadoop-2.7.3]# bin/hdfs dfs -cat output/part-r-00000
Hello   2
Java    2
World   2
dtt     2
[[email protected] hadoop-2.7.3]#

原文地址：https://www.cnblogs.com/mtime2004/p/10004164.html