1. hadoop checknative 可以查看hadoop 支持的压缩算法
image.png2. 启用压缩算法总体来说 节省了 磁盘IO和网络宽带资源 ,但是加重了CPU 负担。
image.png image.pngMR支持的压缩编码
image.png为了支持多种压缩/解压缩算法,Hadoop引入了编码/解码器,如下表所示。
image.png压缩格式 对应的编码/解码器
DEFLATE org.apache.hadoop.io.compress.DefaultCodec
gzip org.apache.hadoop.io.compress.GzipCodec
bzip2 org.apache.hadoop.io.compress.BZip2Codec
LZO com.hadoop.compression.lzo.LzopCodec
Snappy org.apache.hadoop.io.compress.SnappyCodec
压缩性能的比较
image.pngsnappy 介绍
http://google.github.io/snappy/
On a single core of a Core i7 processor in 64-bit mode, Snappy compresses at about 250 MB/sec or more and decompresses at about 500 MB/sec or more.
压缩位置选择
压缩可以在MapReduce作用的任意阶段启用
image.png压缩参数配置
要在Hadoop中启用压缩,可以配置如下参数 (mapred-site.xml文件中)
image.png
项目经验之支持LZO压缩配置
1.hadoop本身并不支持lzo压缩,故需要使用twitter提供的hadoop-lzo开源组件。hadoop-lzo需依赖hadoop和lzo进行编译.
步骤参考
Hadoop支持LZO
0. 环境准备
maven(下载安装,配置环境变量,修改sitting.xml加阿里云镜像)
gcc-c++
zlib-devel
autoconf
automake
libtool
通过yum安装即可,yum -y install gcc-c++ lzo-devel zlib-devel autoconf automake libtool
1. 下载、安装并编译LZO
wget http://www.oberhumer.com/opensource/lzo/download/lzo-2.10.tar.gz
tar -zxvf lzo-2.10.tar.gz
cd lzo-2.10
./configure -prefix=/usr/local/hadoop/lzo/
make
make install
2. 编译hadoop-lzo源码
2.1 下载hadoop-lzo的源码,下载地址:https://github.com/twitter/hadoop-lzo/archive/master.zip
2.2 解压之后,修改pom.xml
<hadoop.current.version>3.1.3</hadoop.current.version>
2.3 声明两个临时环境变量
export C_INCLUDE_PATH=/usr/local/hadoop/lzo/include
export LIBRARY_PATH=/usr/local/hadoop/lzo/lib
2.4 编译
进入hadoop-lzo-master,执行maven编译命令
mvn package -Dmaven.test.skip=true
2.5 进入target,hadoop-lzo-0.4.21-SNAPSHOT.jar 即编译成功的hadoop-lzo组件
- 将编译好后的hadoop-lzo-0.4.20.jar 放入hadoop-3.1.3/share/hadoop/common/
[root@hadoop102 common]$ pwd
/opt/module/hadoop-3.1.3/share/hadoop/common
[atguigu@hadoop102 common]$ ls
hadoop-lzo-0.4.20.jar
3.同步hadoop-lzo-0.4.20.jar到hadoop103、hadoop104
[root@hadoop102 common]$ xsync hadoop-lzo-0.4.20.jar
- core-site.xml增加配置支持LZO压缩
<property>
<name>io.compression.codecs</name>
<value>
org.apache.hadoop.io.compress.GzipCodec,
org.apache.hadoop.io.compress.DefaultCodec,
org.apache.hadoop.io.compress.BZip2Codec,
org.apache.hadoop.io.compress.SnappyCodec,
com.hadoop.compression.lzo.LzoCodec,
com.hadoop.compression.lzo.LzopCodec
</value>
</property>
<property>
<name>io.compression.codec.lzo.class</name>
<value>com.hadoop.compression.lzo.LzoCodec</value>
</property>
- 同步core-site.xml到hadoop103、hadoop104
[root@hadoop102 hadoop]$ xsync core-site.xml
6.启动及查看集群
[root@hadoop102 hadoop-3.1.3]$ sbin/start-dfs.sh
[root@hadoop103 hadoop-3.1.3]$ sbin/start-yarn.sh
项目经验之LZO创建索引
1. 创建LZO文件的索引,LZO压缩文件的可切片特性依赖于其索引,故我们需要手动为LZO压缩文件创建索引。若无索引,则LZO文件的切片只有一个。
案例: big_file.lzo 你自己要压缩的lzo格式的文件
hadoop jar /opt/module/hadoop-3.1.3/share/hadoop/common/hadoop-lzo-0.4.20.jar
com.hadoop.compression.lzo.DistributedLzoIndexer big_file.lzo
2. 测试
(1)将bigtable.lzo(150M)上传到集群的根目录
[root@hadoop102 module]$ hadoop fs -mkdir /input
[root@hadoop102 module]$ hadoop fs -put bigtable.lzo /input
(2) 执行wordcount程序
[root@hadoop102 module]$ hadoop jar
/opt/module/hadoop-3.1.3/share/hadoop/mapreduce/hadoop-mapreduce-examples-3.1.3.jar wordcount /input /output1
image.png
(3) 对上传的LZO文件建索引
[root@hadoop102 module]$ hadoop jar
/opt/module/hadoop-3.1.3/share/hadoop/common/hadoop-lzo-0.4.20.jar
com.hadoop.compression.lzo.DistributedLzoIndexer /input/bigtable.lzo
4)再次执行WordCount程序
[root@hadoop102 module]$ hadoop jar
/opt/module/hadoop-3.1.3/share/hadoop/mapreduce/hadoop-mapreduce-examples-3.1.3.jar
wordcount /input /output2
image.png
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