MapReduce

问题 I have a number of bags and I want to compute the pairwise similarities between the bags. sequences = FOREACH raw GENERATE gen_bag(logs); The relation is described as follows: sequences: {t: (type: chararray, value:charray)} The similarity is computed by a Python UDF that takes two bags as arguments. I have tried to do a nested foreach over the sequences variable, but I cant loop over the same relation twice. I've also tried to define the sequences twice, but I cant access the copy in the

问题 Are there any reliable techniques for storing prototype-based libraries/frameworks in mongoDB's system.js? I came across this issue when trying to use dateJS formats within a map-reduce. JIRA #SERVER-770 explains that objects' closures - including their prototypes - are lost when serialized to the system.js collection, and that this is the expected behavior. Unfortunately, this excludes a lot of great frameworks such as dojo, Google Closure, and jQuery. Is there a way to somehow convert or

问题 I am doing twitter sentiment analysis using hadoop, flume and hive. I have created the table using hive -f tweets.sql tweets.sql --create the tweets_raw table containing the records as received from Twitter SET hive.support.sql11.reserved.keywords=false; CREATE EXTERNAL TABLE Mytweets_raw ( id BIGINT, created_at STRING, source STRING, favorited BOOLEAN, retweet_count INT, retweeted_status STRUCT< text:STRING, user:STRUCT<screen_name:STRING,name:STRING>>, entities STRUCT< urls:ARRAY<STRUCT

问题 I have installed Hadoop 2.3.0 in windows and able to execute MR jobs successfully. But while trying with streaming sample in C# [with HadoopSDK's .Net assemblies] the app ends with the following exception 14/05/16 18:21:06 INFO mapreduce.Job: Task Id : attempt_1400239892040_0003_r_000000_0, Status : FAILED Error: java.lang.NullPointerException at org.apache.hadoop.mapred.Task.getFsStatistics(Task.java:347) at org.apache.hadoop.mapred.ReduceTask$OldTrackingRecordWriter.<init>(ReduceTask.java

问题 I am coding a MapReduce job for finding the occurrence of a search string (passed through Command Line argument) in an input file stored in HDFS using old API. Below is my Driver class - public class StringSearchDriver { public static void main(String[] args) throws IOException { JobConf jc = new JobConf(StringSearchDriver.class); jc.set("SearchWord", args[2]); jc.setJobName("String Search"); FileInputFormat.addInputPath(jc, new Path(args[0])); FileOutputFormat.setOutputPath(jc, new Path(args

问题 I am writing an indexing app for MapReduce. I was able to split inputs with NLineInputFormat, and now I've got few hundred mappers in my app. However, only 2/mashine of those are active at the same time, the rest are "PENDING". I believe that such a behavior slows the app significantly. How do I make hadoop run at least 100 of those at the same time per machine? I am using the old hadoop api syntax. Here's what I've tried so far: conf.setNumMapTasks(1000); conf.setNumTasksToExecutePerJvm(500)

问题 I am writing an indexing app for MapReduce. I was able to split inputs with NLineInputFormat, and now I've got few hundred mappers in my app. However, only 2/mashine of those are active at the same time, the rest are "PENDING". I believe that such a behavior slows the app significantly. How do I make hadoop run at least 100 of those at the same time per machine? I am using the old hadoop api syntax. Here's what I've tried so far: conf.setNumMapTasks(1000); conf.setNumTasksToExecutePerJvm(500)

问题 15/06/11 10:31:51 INFO mapreduce.Job: map 100% reduce 0% I am trying to run open source kNN join MapReduce hbrj algorithm on a Hadoop 2.6.0 for single node cluster - pseudo-distributed operation installed on my laptop (OSX). (The source can be found here: http://www.cs.utah.edu/~lifeifei/knnj/). This algorithm is comprised of two MapReduce phases where the second phase uses the first phase's output files as its input. The first phase maps and reduces successfully - I can also look into the

问题 New user of hadoop and mapreduce, i would like to create a mapreduce job to do some measure on images. this why i would like to know if i can passe an image as input to mapreduce?if yes? any kind of example thanks 回答1: No.. you cannot pass an image directly to a MapReduce job as it uses specific types of datatypes optimized for network serialization. I am not an image processing expert but I would recommend to have a look at HIPI framework. It allows image processing on top of MapReduce

问题 I am running two map-reduce pairs. The output of first map-reduce is being used as the input for the next map-reduce. In order to do that I have given the job.setOutputFormatClass(SequenceFileOutputFormat.class). While running the following Driver class: package org; import org.apache.commons.configuration.ConfigurationFactory; import org.apache.hadoop.conf.Configured; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Job; import org.apache