Spark 下载版本间的区别
困惑于Spark官网的Pre-built for Apache Hadoop和Pre-built with user-provided Apache Hadoop的区别。
为何下载个Spark还搞那么多的版本？？？本文以2.1.1版作为测试。
Pre-built for Apache Hadoop
在一台安装了Java的机器上执行以下命令
# 0. 进入测试目录
cd /tmp
# 1. 下载Spark 并解压
wget https://archive.apache.org/dist/spark/spark-2.1.1/spark-2.1.1-bin-hadoop2.7.tgz
tar -xf spark-2.1.1-bin-hadoop2.7.tgz
# 2. 运行Spark
cd /tmp/spark-2.1.1-bin-hadoop2.7 &&\
./bin/spark-submit \
--class org.apache.spark.examples.SparkPi \
./examples/jars/spark-examples_2.11-2.1.1.jar \
100
# 程序是可以正常运行的且可以看到
# 类似于Pi is roughly 3.1408123140812316 的字样
Pre-built with user-provided Apache Hadoop
在一台安装了Java的机器上执行以下命令
# 0. 进入测试目录
cd /tmp
# 1. 下载Spark 并解压
wget https://archive.apache.org/dist/spark/spark-2.1.1/spark-2.1.1-bin-without-hadoop.tgz
tar -xf spark-2.1.1-bin-without-hadoop.tgz
# 2. 运行Spark
cd /tmp/spark-2.1.1-bin-without-hadoop &&\
./bin/spark-submit \
--class org.apache.spark.examples.SparkPi \
./examples/jars/spark-examples_2.11-2.1.1.jar \
100
# 直接报错，java.lang.ClassNotFoundException: org.apache.hadoop.fs.FSDataInputStream
# 3. 与之前的spark-2.1.1-bin-hadoop2.7.tgz 对比以下jar 包
ls spark-2.1.1-bin-hadoop2.7/jars/ > h.txt
ls spark-2.1.1-bin-without-hadoop/jars/ > w.txt
diff -y -W 50 h.txt w.txt # -y 并排对比，-W 列宽
# 看到右边的w.txt 内容中少了很多Hadoop 的包
# 4. 下载Hadoop 并解压
cd /tmp && wget https://archive.apache.org/dist/hadoop/common/hadoop-2.7.2/hadoop-2.7.2.tar.gz
tar -xf hadoop-2.7.2.tar.gz
# 5. 确认Hadoop 的版本
/tmp/hadoop-2.7.2/bin/hadoop version
# 6. 关联Spark-Without-Hadoop 和Hadoop
cat > /tmp/spark-2.1.1-bin-without-hadoop/conf/spark-env.sh << 'EOF'
#!/usr/bin/env bash
export SPARK_DIST_CLASSPATH=$(/tmp/hadoop-2.7.2/bin/hadoop classpath)
EOF
# 7. 再次运行Spark
cd /tmp/spark-2.1.1-bin-without-hadoop &&\
./bin/spark-submit \
--class org.apache.spark.examples.SparkPi \
./examples/jars/spark-examples_2.11-2.1.1.jar \
100 2>&1 | grep 'Pi is'
# 成功显示Pi is roughly 3.1424395142439514
总结
由上实验可见，[Pre-built with user-provided Apache Hadoop](#Pre-built with user-provided Apache Hadoop)版需要自己修改配置文件去适配Hadoop，实际就是执行时在CLASSPATH中加入Hadoop的Jar包，而[Pre-built for Apache Hadoop](#Pre-built for Apache Hadoop)则是做到了开箱即用，将提前对应的Hadoop Jar包捆绑在其中，同时因为Hadoop 2.6和Hadoop 2.7的HDFS等接口不一样，所以Pre-built for Apache Hadoop分了两个版本。
参考
Using Spark’s “Hadoop Free” Build
What is the difference between the package types of Spark on the download page?
