MapReduce

问题 I have written mapper and reducer in python for word count program that works fine. Here is a sample: echo "hello hello world here hello here world here hello" | wordmapper.py | sort -k1,1 | wordreducer.py hello 4 here 3 world 2 Now when i try to submit a hadoop job for a large file, I get errors hadoop jar share/hadoop/tools/sources/hadoop-*streaming*.jar -file wordmapper.py -mapper wordmapper.py -file wordreducer.py -reducer wordreducer.py -input /data/1jrl.pdb -output /output/py_jrl

问题 My data format uses \0 instead of new line. So default hadoop textLine reader dosn't work. How can I configure it to read lines separated by special character? If it is impossible to configure LineReader, Maybe it is possible to apply specic stream processor(tr "\0" "\n") not sure how to do this. 回答1: You can write your own InputFormat class that splits data on \0 instead of \n . For a walkthrough on how to do that, check here: http://developer.yahoo.com/hadoop/tutorial/module5.html

问题 My collection has the following simplified (booking) schema: { name: "room 1", from: ISODate("2014-06-10T12:00:00Z"), to: ISODate("2014-06-14T12:00:00Z") }, { name: "room 1", from: ISODate("2014-06-25T12:00:00Z"), to: ISODate("2014-06-27T12:00:00Z") }, { name: "room 2", from: ISODate("2014-06-12T12:00:00Z"), to: ISODate("2014-06-26T12:00:00Z") } I'd like to query, if a room is available in a given range. For example I'd like to know if room 1 is available FROM 2014-06-11 TO 2014-06-13 room 1

问题 I am testing my MR jobs under a single node cluster. Once I installed mahout 9 version Mapreduce jobs stopped showing the progress in jobtracker.(Dont know if that happened after mahout installation) When ever I run a job in my hadoop cluster it wont show the status in job tacker UI as previous and the execution log displaying in the console is also different (similar to mahout logs) Why is it so? Thanks In Advance. 回答1: Most probably you job might be running using LocalJobRunner. If your job

问题 It shows that it created cached files. But, when I go and look at the location the file is not present and when I am trying to read from my mapper it shows the File Not Found Exception. This is the code that I am trying to run: JobConf conf2 = new JobConf(getConf(), CorpusCalculator.class); conf2.setJobName("CorpusCalculator2"); //Distributed Caching of the file emitted by the reducer2 is done here conf2.addResource(new Path("/opt/hadoop1/conf/core-site.xml")); conf2.addResource(new Path("

问题 Update 1 , following Ayende's answer This is my first journey into RavenDb and to experiment with it I wrote a small map/ reduce, but unfortunately the result is empty? I have around 1.6 million documents loaded into RavenDb A document: public class Tick { public DateTime Time; public decimal Ask; public decimal Bid; public double AskVolume; public double BidVolume; } and wanted to get Min and Max of Ask over a specific period of Time. The collection by Time is defined as: var ticks = session

问题 I have created a Map/Reduce script which will fetch customer invoices and delete it. If I am creating saved search in UI based on the below criteria, it shows 4 million records. Now, if I run the script, execution stops before completing the "getInputData" stage as maximum storage limit of this stage is 200Mb. So, I want to fetch first 4000 records out of 4 million and execute it and schedule the script for every 15 mins. Here is the code of first stage (getInputData) - var count=0; var

问题 I have a view in my django project that fires off a celery task. The celery task itself triggers a few map/reduce jobs via subprocess/fabric and the results of the hadoop job are stored on disk --- nothing is actually stored in the database. After the hadoop job has been completed, the celery task sends a django signal that it is done, something like this: # tasks.py from models import MyModel import signals from fabric.operations import local from celery.task import Task class

问题 So I'm switching to NoSQL from SQL background. So I know I should be 'denormalizing' here.. So basically I have a simplified idea of what i have to do; Users These documents hold authentication info, maybe payment method, username and all kinds of details Posts These posts are made by users, and in each post, we have to display the username and email of a user. So by method of 'denormalizing', I would put the username and the email of the user into each post s/he makes. But doesn't this

问题 I'm using hive over hbase to make some BI. i have already configured hive and hbase but when i run that query "select count(*) from hbase_table_2 " on Hive hbase_table_2 is a table in hive which refer to a table in Hbase This exception occurred: # of failed Map Tasks exceeded allowed limit. FailedCount: 1. LastFailedTask: task_201212171838_0009_m_000000" java.io.IOException: java.io.IOException: org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation@7d858aa0 closed at org