Hadoop | 易学教程

NameNode: Failed to start namenode in windows 7

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问题 I am trying to install Hadoop in windows machine, in middle I got the below error. Logs 17/11/28 16:31:48 ERROR namenode.NameNode: Failed to start namenode. java.lang.UnsatisfiedLinkError: org.apache.hadoop.io.nativeio.NativeIO$Windows.access0(Ljava/lang/String;I)Z at org.apache.hadoop.io.nativeio.NativeIO$Windows.access0(Native Method) at org.apache.hadoop.io.nativeio.NativeIO$Windows.access(NativeIO.java:609) at org.apache.hadoop.fs.FileUtil.canWrite(FileUtil.java:996) at org.apache.hadoop

set HBase properties for Spark Job using spark-submit

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问题 During Hbase data migration I have encountered a java.lang.IllegalArgumentException: KeyValue size too large In long term : I need to increase the properties hbase.client.keyvalue.maxsize (from 1048576 to 10485760) in the /etc/hbase/conf/hbase-site.xml but I can't change this file now (I need validation). In short term : I have success to import data using command : hbase org.apache.hadoop.hbase.mapreduce.Import \ -Dhbase.client.keyvalue.maxsize=10485760 \ myTable \ myBackupFile Now I need to

What will happen if Hive number of reducers is different to number of keys?

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问题 In Hive I ofter do queries like: select columnA, sum(columnB) from ... group by ... I read some mapreduce example and one reducer can only produce one key. It seems the number of reducers completely depends on number of keys in columnA. Therefore, why could hive set number of reducers manully? If there are 10 different values in columnA and I set number of reducers to 2 , what will happen? Each reducers will be reused 5 times? If there are 10 different values in columnA and I set number of

How to run Spark locally on Windows using eclipse in java

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问题 I'm trying to test Mllib's implementation of SVM. I want to run their java example locally on windows, using eclipse. I've downloaded Spark 1.3.1 pre-built for Hadoop 2.6 . When i try to run the example code, i get: 15/06/11 16:17:09 ERROR Shell: Failed to locate the winutils binary in the hadoop binary path java.io.IOException: Could not locate executable null\bin\winutils.exe in the Hadoop binaries. What should i change in order to be able to run the example code in this setup? 回答1: Create

What will happen if Hive number of reducers is different to number of keys?

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Spark on Windows 10. 'Files\Spark\bin\..\jars“”\' is not recognized as an internal or external command

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问题 I am very frustrated by Spark. An evening wasted thinking that I was doing something wrong but I have uninstalled and reinstalled several times, following multiple guides that all indicate a very similar path. On cmd prompt, I am trying to run: pyspark or spark-shell The steps I followed include downloading a pre-built package from: https://spark.apache.org/downloads.html including spark 2.0.2 with hadoop 2.3 and spark 2.1.0 with hadoop 2.7. Neither work and I get this error: 'Files\Spark\bin

恒讯科技分析裸金属服务器的应用场景及优势

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裸金属服务器是云计算背景下的更优产物，不仅拥有云计算虚拟化的特点，更能兼顾虚拟机无法支撑的应用。为让大家对裸金属服务器有更透彻的理解，我们总结了它可能应用到的一些场景及优势： 1.Hadoop及其分析环境 Hadoop是一种分布式系统基础架构，其环境的配置、部署和管理非常复杂。大数据应用程序对性能有要求，而激增往往又是零星和不可预测的。实际应用中，用户数量和接收数据量的增长速度远远超过了硬件的扩展速度，造成对现有基础设施的工作量激增，进而导致用户体验和数据处理整体退化。许多企业最初在虚拟云平台上托管此类应用，之后随着性能需求和定价的变化，虚拟云平台基本上已经不堪重负。裸金属服务器方案专门针对大数据应用工作负载，为用户提供快速扩展现有环境或托管解决方案的服务。通过开放的Api接口，可以快速配置和获取管理物理机的能力，用户也可以设计并增长集群，以满足数据增长的业务需求。在诸如超算中心、云游戏、基因测序、机器学习和欺诈检测等高性能计算场景，其数据处理量极大，要求服务器具备极高的计算性能、稳定性、实时性等。裸金属服务器的优势之一便在于无损性能，能够满足这类高性能计算的苛刻需求。 2.容器+裸金属起初，iaas公司从基于虚拟机的重型环境转向了这样一种模式，即：应用程序位于部署在裸金属服务器上的容器中，通过Api进行资源调配，并获取统一平台的自动化运维管理功能

Not able to delete the data from hdfs, even after leaving safemode?

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问题 I used this command to leave the safe mode hdfs dfsadmin -safemode leave But even then, when I use this command to delete files hdfs dfs -rm -r /user/amandeep/share/ It shows the following error 15/06/18 23:35:05 INFO fs.TrashPolicyDefault: Namenode trash configuration: Deletion interval = 0 minutes, Emptier interval = 0 minutes. rm: Cannot delete /user/amandeep/share/lib/lib_20150615024237. Name node is in safe mode. 来源： https://stackoverflow.com/questions/30922639/not-able-to-delete-the

Could not run jar file in hadoop3.1.3

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问题 I tried this command in command prompt (run as administrator): hadoop jar C:\Users\tejashri\Desktop\Hadoopproject\WordCount.jar WordcountDemo.WordCount /work /out but i got this error message: my application got stopped. 2020-04-04 23:53:27,918 INFO client.RMProxy: Connecting to ResourceManager at /0.0.0.0:8032 2020-04-04 23:53:28,881 WARN mapreduce.JobResourceUploader: Hadoop command-line option parsing not performed. Implement the Tool interface and execute your application with ToolRunner

What does checkpointing do on Apache Spark?

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问题 What does checkpointing do for Apache Spark, and does it take any hits on RAM or CPU? 回答1: From Apache Streaming Documentation - Hope it helps: A streaming application must operate 24/7 and hence must be resilient to failures unrelated to the application logic (e.g., system failures, JVM crashes, etc.). For this to be possible, Spark Streaming needs to checkpoint enough information to a fault- tolerant storage system such that it can recover from failures. There are two types of data that are