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。
[root@node1 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
[root@node1 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
[root@node1 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
[root@node1 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 [root@node1 hadoop-2.7.3]# bin/hdfs dfs -cat output/part-r-00000 Hello 2 Java 2 World 2 dtt 2 [root@node1 hadoop-2.7.3]#
