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Spark On Yarn中spark.yarn.jar属性的使用
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今天在测试spark-sql运行在yarn上的过程中，无意间从日志中发现了一个问题：
spark-sql --master yarn
// :: INFO Client: Requesting a new application from cluster with NodeManagers
// :: INFO Client: Verifying our application has not requested more than the maximum memory capability of the cluster ( MB per container)
// :: INFO Client: Will allocate AM container, with MB memory including MB overhead
// :: INFO Client: Setting up container launch context for our AM
// :: INFO Client: Preparing resources for our AM container
// :: INFO Client: Uploading resource file:/home/spark/software/source/compile/deploy_spark/assembly/target/scala-2.10/spark-assembly-1.3.0-SNAPSHOT-hadoop2.3.0-cdh5.0.0.jar -> hdfs://hadoop000:8020/user/spark/.sparkStaging/application_1416381870014_0093/spark-assembly-1.3.0-SNAPSHOT-hadoop2.3.0-cdh5.0.0.jar
// :: INFO Client: Setting up the launch environment for our AM container
再开启一个spark-sql命令行，从日志中再次发现：
// :: INFO Client: Requesting a new application from cluster with NodeManagers
// :: INFO Client: Verifying our application has not requested more than the maximum memory capability of the cluster ( MB per container)
// :: INFO Client: Will allocate AM container, with MB memory including MB overhead
// :: INFO Client: Setting up container launch context for our AM
// :: INFO Client: Preparing resources for our AM container
// :: INFO Client: Uploading resource file:/home/spark/software/source/compile/deploy_spark/assembly/target/scala-2.10/spark-assembly-1.3.0-SNAPSHOT-hadoop2.3.0-cdh5.0.0.jar -> hdfs://hadoop000:8020/user/spark/.sparkStaging/application_1416381870014_0094/spark-assembly-1.3.0-SNAPSHOT-hadoop2.3.0-cdh5.0.0.jar
// :: INFO Client: Setting up the launch environment for our AM container
然后查看HDFS上的文件：
hadoop fs -ls hdfs://hadoop000:8020/user/spark/.sparkStaging/
drwx------ - spark supergroup -- : hdfs://hadoop000:8020/user/spark/.sparkStaging/application_1416381870014_0093
drwx------ - spark supergroup -- : hdfs://hadoop000:8020/user/spark/.sparkStaging/application_1416381870014_0094
每个Application都会上传一个spark-assembly-x.x.x-SNAPSHOT-hadoopx.x.x-cdhx.x.x.jar的jar包，影响HDFS的性能以及占用HDFS的空间。
在Spark文档(http://spark.apache.org/docs/latest/running-on-yarn.html)中发现spark.yarn.jar属性，将spark-assembly-xxxxx.jar存放在hdfs://hadoop000:8020/spark_lib/下
在spark-defaults.conf添加属性配置：
spark.yarn.jar hdfs://hadoop000:8020/spark_lib/spark-assembly-1.3.0-SNAPSHOT-hadoop2.3.0-cdh5.0.0.jar
再次启动spark-sql --master yarn观察日志：
14/12/29 15:39:02 INFO Client: Requesting a new application from cluster with 1 NodeManagers
14/12/29 15:39:02 INFO Client: Verifying our application has not requested more than the maximum memory capability of the cluster (8192 MB per container)
14/12/29 15:39:02 INFO Client: Will allocate AM container, with 896 MB memory including 384 MB overhead
14/12/29 15:39:02 INFO Client: Setting up container launch context for our AM
14/12/29 15:39:02 INFO Client: Preparing resources for our AM container
14/12/29 15:39:02 INFO Client: Source and destination file systems are the same. Not copying hdfs://hadoop000:8020/spark_lib/spark-assembly-1.3.0-SNAPSHOT-hadoop2.3.0-cdh5.0.0.jar
14/12/29 15:39:02 INFO Client: Setting up the launch environment for our AM container
观察HDFS上文件
hadoop fs -ls hdfs://hadoop000:8020/user/spark/.sparkStaging/application_1416381870014_0097
该Application对应的目录下没有spark-assembly-xxxxx.jar了，从而节省assembly包上传的过程以及HDFS空间占用。
我在测试过程中遇到了类似如下的错误：
Application application_xxxxxxxxx_yyyy failed 2 times due to AM Container for application_xxxxxxxxx_yyyy exited with exitCode: -1000 due to: java.io.FileNotFoundException: File /tmp/hadoop-spark/nm-local-dir/filecache does not exist
在/tmp/hadoop-spark/nm-local-dir路径下创建filecache文件夹即可解决报错问题。
