MapReduce

问题 I ran Giraph 1.0.0 with hadoop 2.2.0 using the PageRank Benchmark example here. Suddenly I got this error result: Exception in thread "main" java.lang.IllegalArgumentException: checkLocalJobRunnerConfiguration: When using LocalJobRunner, must have only one worker since only 1 task at a time! at org.apache.giraph.job.GiraphJob.checkLocalJobRunnerConfiguration(GiraphJob.java:151) at org.apache.giraph.job.GiraphJob.run(GiraphJob.java:225) at org.apache.giraph.benchmark.GiraphBenchmark.run

问题 I have started a maven project trying to implement the MapReduce algorithm in java 1.5.0_14. I have chosen the 0.20.2 API hadoop version. In the pom.xml i'm using thus the following dependency: < dependency> < groupId>org.apache.hadoop< /groupId> < artifactId>hadoop-core< /artifactId> < version>0.20.2< /version> < /dependency> But when I'm using an import to the org.apache.hadoop classes, I get the following error: bad class file: ${HOME_DIR}\repository\org\apache\hadoop\hadoop-core\0.20.2

问题 I am new to hadoop and here is my problem. I have configured hadoop 2.4.0 with jdk1.7.60 on cluster of 3 machine. I am able to execute all the commands of hadoop. Now I have modified wordcount example and created jar file. I have already executed with this jar file on hadoop 1.2.1 and got the result. But now on hadoop 2.4.0 I am not getting any result. Command used for execution $hadoop jar WordCount.jar WordCount /data/webdocs.dat /output I am getting following message from the setup: 14/06

问题 Is it possible to calculate a first order derivative using the aggregate framework? For example, I have the data : {time_series : [10,20,40,70,110]} I'm trying to obtain an output like: {derivative : [10,20,30,40]} 回答1: db.collection.aggregate( [ { "$addFields": { "indexes": { "$range": [ 0, { "$size": "$time_series" } ] }, "reversedSeries": { "$reverseArray": "$time_series" } } }, { "$project": { "derivatives": { "$reverseArray": { "$slice": [ { "$map": { "input": { "$zip": { "inputs": [ "

问题 Being new to mapreduce & hadoop world, after trying out basic mapreduce programs, I wanted to try compositekey sample code. Input dataset is as follows: Country,State,County,populationinmillions USA,CA,alameda,100 USA,CA,losangels,200 USA,CA,Sacramento,100 USA,FL,xxx, 10 USA,FL,yyy,12 Desired output data should be like this: USA,CA,500 USA,FL,22 Here instead Country+State fields form the composite key. I am getting the following output. The population is not getting added for some reason. Can

问题 In Big Data the code is pushed towards the data for execution. This makes sense, since data is huge and the code for execution is relatively small. Coming to AWS EMR, the data can be either in HDFS or in S3. In case of S3, the data has to be pulled to the core/task nodes for execution from some other nodes. This might be a bit of overhead when compared to the data in HDFS. Recently, I noticed that when the MR job was executing there was huge latency getting the log files into S3. Sometimes it

问题 In Big Data the code is pushed towards the data for execution. This makes sense, since data is huge and the code for execution is relatively small. Coming to AWS EMR, the data can be either in HDFS or in S3. In case of S3, the data has to be pulled to the core/task nodes for execution from some other nodes. This might be a bit of overhead when compared to the data in HDFS. Recently, I noticed that when the MR job was executing there was huge latency getting the log files into S3. Sometimes it

问题 I have tried the following combinations of bootstrap actions to increase the heap size of my job but none of them seem to work: --mapred-key-value mapred.child.java.opts=-Xmx1024m --mapred-key-value mapred.child.ulimit=unlimited --mapred-key-value mapred.map.child.java.opts=-Xmx1024m --mapred-key-value mapred.map.child.ulimit=unlimited -m mapred.map.child.java.opts=-Xmx1024m -m mapred.map.child.ulimit=unlimited -m mapred.child.java.opts=-Xmx1024m -m mapred.child.ulimit=unlimited What is the

问题 I recently read this great article which succinctly explains the power of Google's MapReduce: http://www.joelonsoftware.com/items/2006/08/01.html In Mastering Delphi 2009, Marco Cantu shows a multi-threaded for loop using Anonymous functions, which is basically the Map part of MapReduce, but said it wasn't complete and there were other samples out there. I'm also vaguely aware of someone at Embarcadero working on a DTL library but I haven't seen much on it lately. So, are there solid

问题 I am new to MongoDB, I am using map/reduce. Can somebody tell me how to debug while using map/reduce? I used "print()" function but on MongoDB shell, nothing is printed. Following is my reduce function: var reduce = function(key, values){ var result = {count: 0, host: ""}; for(var i in values){ result.count++; result.host = values[i].host; print(key+" : "+values[i]); } return result; } when I write the above function on shell and the press Enter after completing, nothing gets printed on the