MapReduce

mapreduce on yarn的工作流程

由 假装没事ソ 提交于 2020-01-16 17:13:37
　　 当client提交一个任务后,首先resourceManger(RM)来调度出一个container,这个container是在nodeManger(NM)运作的, 　client直接和这个container所在的NM进行通信,在这个container中启动applicationMaster(AM),启动成功之后,这个AM将全权负责此次任务的进度,失败原因( 在一次job中只有一个AM ). 　AM会计算此次任务所需的资源,然后向RM申请资源,得到一组供map/reduce task运行的container,然后协同NM一起对每个container执行一些必要的任务,在任务执行 　过程中,AM会一直监视着任务的运行进度,若中间某个NM上的container中的任务失败,那么AM会重新找一台节点来运行此任务. 流程如下: MRv2运行流程： MR JobClient向resourceManager(RM)提交一个job RM向Scheduler请求一个供MR AM运行的container，然后启动它 MR AM启动起来后向RM注册 MR JobClient向RM获取到MR AM相关的信息，然后直接与MR AM进行通信 MR AM计算splits并为所有的map构造资源请求 MR AM做一些必要的MR OutputCommitter的准备工作 MR AM向RM(Scheduler

Save and read complicated Writable value in Hadoop job

由 生来就可爱ヽ(ⅴ＜●) 提交于 2020-01-16 14:47:42
问题 I need to move complicated value (implements Writable) from output of 1st map-reduce job to input of other map-reduce job. Results of 1st job saved to file. File can store Text data or BytesWritable (with default output \ input formats). So I need some simple way to convert my Writable to Text or To BytesWritable and from it. Does it exists? Any alternative way to do this? Thanks a lot 回答1: User irW is correct, use SequenceFileOutputFormat. SequenceFile solves this exact problem, without

Hadoop Adding More Than 1 Core Per Container on Hadoop 2.7

由 左心房为你撑大大i 提交于 2020-01-16 11:58:07
问题 I hear there is a way to add 32 cores or which ever you have for cores to 1 container in Hadoop 2.7 yarn. Would this be possible and does someone have a sample configuration of what I need to change to achieve this? The test would be terasort, adding my 40 cores to 1 container job. 回答1: For vCores following are the configurations: yarn.scheduler.maximum-allocation-vcores - Specifies maximum allocation of vCores for every container request Typically in yarn-site.xml , you set this value to 32.

Hadoop Adding More Than 1 Core Per Container on Hadoop 2.7

由 最后都变了- 提交于 2020-01-16 11:57:10
问题 I hear there is a way to add 32 cores or which ever you have for cores to 1 container in Hadoop 2.7 yarn. Would this be possible and does someone have a sample configuration of what I need to change to achieve this? The test would be terasort, adding my 40 cores to 1 container job. 回答1: For vCores following are the configurations: yarn.scheduler.maximum-allocation-vcores - Specifies maximum allocation of vCores for every container request Typically in yarn-site.xml , you set this value to 32.

【Hive】Hive基础知识

由 我怕爱的太早我们不能终老 提交于 2020-01-16 08:18:10
文章目录 1. hive产生背景 2. hive是什么 3. hive的特点 3.1优点： 3.2 缺点： 4. Hive 和 RDBMS 的对比 5. hive架构 5.1 用户接口层 5.2 Thrift Server层 5.3 元数据库层 5.4 Driver核心驱动层 6. hive的数据存储（整理一） 7. hive的数据组织形式（整理二） 7.1 库 7.2 表 7.2.1 从数据的管理权限分 7.2.1.1 内部表(管理表、managed_table) 7.2.1.2 外部表(external_table) 7.2.2 从功能上分 7.2.2.1 分区表 7.2.2.2 分桶表 7.3 视图 7.4 数据存储 7.4.1 元数据 7.4.2 表数据(原始数据) 1. hive产生背景 先分析mapreduce: mapreduce主要用于数据清洗或统计分析工作 并且绝大多数的场景都是针对的结构化数据的分析 而对于结构化的数据处理我们想到sql 但数据量非常大时，没办法使用mysql等，只能使用mapreduce 可是 mapreduce 的 缺点 是： 编程不便、成本太高 hive的诞生： 如果有一个组件可以针对大数据量的结构化数据进行数据分析，但是又不用写mapreduce，直接用sql语句实现就完美了 所以hive就诞生了 直接使用 MapReduce

What are the main differences between KeyValueTextInputFormat and TextInputFormat in hadoop?

由 痴心易碎 提交于 2020-01-16 01:13:17
问题 Can somebody give me one practical scenario where we have to use KeyValueTextInputFormat and TextInputFormat ?? 回答1: The TextInputFormat class converts every row of the source file into key/value types where the BytesWritable key represents the offset of the record and the Text value represents the entire record itself. The KeyValueTextInputFormat is an extended version of TextInputFormat , which is useful when we have to fetch every source record as Text/Text pair where the key/value were

Processing paraphragraphs in text files as single records with Hadoop

由 天大地大妈咪最大 提交于 2020-01-15 15:36:25
问题 Simplifying my problem a bit, I have a set of text files with "records" that are delimited by double newline characters. Like 'multiline text' 'empty line' 'multiline text' 'empty line' and so forth. I need to transform each multiline unit separately and then perform mapreduce on them. However, I am aware that with the default wordcount setting in the hadoop code boilerplate, the input to the value variable in the following function is just a single line and there are no guarantees that the

MapReduce

由 て烟熏妆下的殇ゞ 提交于 2020-01-15 14:01:24
MapReduce采用的是“分而治之”的思想，把对大规模数据集的操作，分发给一个主节点管理下的各个从节点共同完成，然后通过整合各个节点的中间结果，得到最终结果。简单来说，MapReduce就是“任务的分解与结果的汇总”。 一、 MapReduce的工作原理 在分布式计算中，MapReduce框架负责处理了并行编程里分布式存储、工作调度，负载均衡、容错处理以及网络通信等复杂问题，现在我们把处理过程高度抽象为Map与Reduce两个部分来进行阐述，其中Map部分负责把任务分解成多个子任务，Reduce部分负责把分解后多个子任务的处理结果汇总起来，具体设计思路如下。 （1）Map过程需要继承org.apache.hadoop.mapreduce包中Mapper类，并重写其map方法。通过在map方法中添加两句把key值和value值输出到控制台的代码，可以发现map方法中输入的value值存储的是文本文件中的一行（以回车符为行结束标记），而输入的key值存储的是该行的首字母相对于文本文件的首地址的偏移量。然后用StringTokenizer类将每一行拆分成为一个个的字段，把截取出需要的字段（本实验为买家id字段）设置为key，并将其作为map方法的结果输出。 （2）Reduce过程需要继承org.apache.hadoop.mapreduce包中Reducer类，并重写其reduce方法

Counter is not working in reducer code

由 限于喜欢 提交于 2020-01-15 11:07:27
问题 I am working on a Big hadoop project and there is a small KPI, where I have to write only the top 10 values in reduces output. To complete this requirement, I have used a counter and break the loop when counter is equal to 11, but still reducer writes all of the values to HDFS. This is a pretty simple java code, but I am stuck :( For testing, I have created one stand alone class (java application) to do this and this is working there; I'm wondering why it is not working in reducer code.

How to specify the partitioner for hadoop streaming

由 可紊 提交于 2020-01-15 09:55:21
问题 I have a custom partitioner like below: import java.util.*; import org.apache.hadoop.mapreduce.*; public static class SignaturePartitioner extends Partitioner<Text,Text> { @Override public int getPartition(Text key,Text value,int numReduceTasks) { return (key.toString().Split(' ')[0].hashCode() & Integer.MAX_VALUE) % numReduceTasks; } } I set the hadoop streaming parameter like below -file SignaturePartitioner.java \ -partitioner SignaturePartitioner \ Then I get an error: Class Not Found. Do
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