MapReduce

mapreduce job submission through java Processbuilder do not ending

由 戏子无情 提交于 2019-12-08 08:20:00
问题 I have a mareduce job as jar file , say 'mapred.jar'.Actually Jobtracker is running in a remote linux machine. I run the jar file from local machine, job in the jar file is submitted to the remote jobtracker and it works fine as below: java -jar F:/hadoop/mapred.jar 13/12/19 12:40:27 WARN mapred.JobClient: Use GenericOptionsParser for parsing th e arguments. Applications should implement Tool for the same. 13/12/19 12:40:27 INFO input.FileInputFormat: Total input paths to process : 49 13/12

“Java Heap space Out Of Memory Error” while running a mapreduce program

由 本小妞迷上赌 提交于 2019-12-08 08:19:21
问题 I'm facing Out Of Memory error while running a mapreduce program.If I keep 260 files in one folder and give as input to the mapreduce program,it is showing Java Heap space Out of Memory error.If I give only 100 files as input the mapreduce,it is running fine.Then how can I limit the mapreduce program to take only 100 files (~50MB) at a time. Can anyone please suggest on this issue ... No of files:318 ,No of blocks:1(blocksize:128MB), Hadoop is running on 32 bit system My StackTrace: =========

How do I count the number of files in HDFS from an MR job?

由 纵饮孤独 提交于 2019-12-08 08:05:54
问题 I'm new to Hadoop and Java for that matter. I'm trying to count the number of files in a folder on HDFS from the MapReduce driver I'm writing. I'd like to do this without calling the HDFS Shell as I want to be able to pass in the directory I use when I run the MapReduce job. I've tried a number of methods but have had no success in implementation due to my inexperience with Java. Any help would be greatly appreciated. Thanks, Nomad. 回答1: You can just use the FileSystem and iterate over the

Hadoop MapReduce sort reduce output using the key

由 ≡放荡痞女 提交于 2019-12-08 07:53:07
问题 down below there is a map-reduce program counting words of several text files. My aim is to have the result in a descending order regarding the amount of appearences. Unfortunately the program sorts the output lexicographically by the key. I want a natural order of the integer value. So I added a custom comparator with job.setSortComparatorClass(IntComparator.class) . But this doesn't work as expected. I'm getting the following exception: java.lang.Exception: java.nio.BufferUnderflowException

the IBM_JAVA error for running jobs in Hadoop 2.2.0

由 馋奶兔 提交于 2019-12-08 07:50:30
问题 Exception in thread "main" java.lang.NoSuchFieldError: IBM_JAVA at org.apache.hadoop.security.UserGroupInformation.getOSLoginModuleName(UserGroupInformation.java:303) at org.apache.hadoop.security.UserGroupInformation.<clinit>(UserGroupInformation.java:348) at org.apache.hadoop.mapreduce.task.JobContextImpl.<init>(JobContextImpl.java:72) at org.apache.hadoop.mapreduce.Job.<init>(Job.java:133) at org.apache.hadoop.mapreduce.Job.<init>(Job.java:123) at org.apache.hadoop.mapreduce.Job.<init>(Job

Hadoop HDFS MapReduce output into MongoDb

由 感情迁移 提交于 2019-12-08 07:34:28
I want to write Java program which reads input from HDFS, processes it using MapReduce and writes the output into a MongoDb. Here is the scenario: I have a Hadoop Cluster which has 3 datanodes. A java program reads the input from the HDFS, processes it using MapReduce. Finally, write the result into a MongoDb. Actually, reading from HDFS and processing it with MapReduce are simple. But I gets stuck about writing the result into a MongoDb. Is there any Java API supported to write the result into MongoDB? Another question is that since it is a Hadoop Cluster, so we don't know which datanode will

Grouping documents in pairs using mongo aggregation

由 只愿长相守 提交于 2019-12-08 07:26:58
问题 I have a collection of items, [ a, b, c, d ] And I want to group them in pairs such as, [ [ a, b ], [ b, c ], [ c, d ] ] This will be used in calculating the differences between each item in the original collection, but that part is solved using several techniques such as the one in this question. I know that this is possible with map reduce, but I want to know if it's possible with aggregation. Edit: Here's an example, The collection of items; each item is an actual document. [ { val: 1 }, {

Hadoop, MapReduce: how to add second node to mapReduce?

由 柔情痞子 提交于 2019-12-08 07:23:07
问题 I have a Hadoop 0.2.2 cluster of 2 nodes. On the first machine I start: namenode datanode NodeManager ResourceManager JobHistoryServer On the second I start all those as well, except for namenode: datanode NodeManager ResourceManager JobHistoryServer My mapred-site.xml on both machines contains: <property> <name>mapred.job.tracker</name> <value>firstMachine:54311</value> </property> My core-site.xml on both machines contains: <property> <name>fs.default.name</name> <value>hdfs://firstMachine

Distinct values of a key in a sub-document MongoDB (100 million records)

由 怎甘沉沦 提交于 2019-12-08 07:02:26
问题 I have 100 million records in my "sample" collection. I want to have another collection with all of the distinct user names "user.screen_name" I have the following structure in my mongodb database "sample" collection: { "_id" : ObjectId("515af34297c2f607b822a54b"), "text" : "random text goes here", "user" : { "id" : 972863366, "screen_name" : "xname", "verified" : false, "time_zone" : "Amsterdam", } } When I try things like "distinct('user.id).length" I get the following error: "errmsg" :

Hadoop/Elastic Map Reduce with binary executable?

由 ╄→гoц情女王★ 提交于 2019-12-08 06:50:58
问题 I am writing and distributed image processing application using hadoop streaming, python, matlab, and elastic map reduce. I have compiled a binary executable of my matlab code using the matlab compiler. I am wondering how I can incorporate this into my workflow so the binary is part of the processing on Amazon's elastic map reduce? It looks like I have to use the Hadoop Distributed Cache? The code is very complicated (and not written by me) so porting it to another language is not possible
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