MapReduce

问题 I want to execute python file which is related to machine learning and as you know there are two files as inputs (train and test) which are important to make learning process. Also I have no reduce file. I have three doubts to run my command: Using two input files, I used -input file1 -input file2 according to Using multiple mapper inputs in one streaming job on hadoop? Turn off reduce, I used -D mapred.reduce.tasks=0 according to How to write 'map only' hadoop jobs? how to make flush my "sys

问题 we're trying to heavily use MapReduce in our project. Now we have this problem, there is a lots of ' DeadlineExceededError ' errors in the log... One example of it ( traceback differs each time a bit ) : Traceback (most recent call last): File "/base/python27_runtime/python27_lib/versions/1/google/appengine/runtime/wsgi.py", line 207, in Handle result = handler(dict(self._environ), self._StartResponse) File "/base/python27_runtime/python27_lib/versions/third_party/webapp2-2.3/webapp2.py",

问题 I've developed a custom InputFormat for Hadoop (including a custom InputSplit and a custom RecordReader ) and I'm experiencing a rare NullPointerException . These classes are going to be used for querying a third-party system which exposes a REST API for records retrieving. Thus, I got inspiration in DBInputFormat, which is a non-HDFS InputFormat as well. The error I get is the following: Error: java.lang.NullPointerException at org.apache.hadoop.mapred.MapTask$NewTrackingRecordReader

问题 I have the following dataset. I need to group them by Account, and then turn the Element_Fieldname into a column. var collection = [ { Account:12345, Element_Fieldname:"cars", Element_Value:true }, { Account:12345, Element_Fieldname:"boats", Element_Value:false } ] This was my attempt to convert rows to columns, but its not working. db.getCollection('my_collection').aggregate([{ $match : { Element_Fieldname : { $in : ["cars", "boats"] } } }, { $group : { _id : "$Account", values : { $addToSet

问题 I recently installed/configured hadoop and curently trying to run some tests. My problem is with copying local data to hdfs: When I try to run hdfs dfs -copyFromLocal /home/develop/test/ test or any similar command, all i get is: copyFromLocal: `test': No such file or directory if I run ls , i get the same output: develop@ubuntu:~$ hdfs dfs -ls ls: `.': No such file or directory I also tried to create the directory test with hdfs dfs -mkdir , but unsuccessful, what exactly am I missing ? 回答1:

问题 I have some documents like following structure, userid in doc1 is not existed in doc2, doc1: userid='abc', probNumber='123', status='OPEN',... doc2: probNumber='123', status='CLOSE'..... I want to get the latest status document according with the given doc.probNumber , But the key of the view would be doc.userid Or use doc.userid with doc.probNumber combination to achieve on that following userid='abc', probNumber='123', status='CLOSE',... Here is the view and reduce if I used probNumber as

问题 I'm trying to run a Python program on Hadoop. The program involves the NLTK library. The program also utilizes the Hadoop Streaming API, as described here. mapper.py: #!/usr/bin/env python import sys import nltk from nltk.corpus import stopwords #print stopwords.words('english') for line in sys.stdin: print line, reducer.py: #!/usr/bin/env python import sys for line in sys.stdin: print line, Console command: bin/hadoop jar contrib/streaming/hadoop-streaming.jar \ -file /hadoop/mapper.py

问题 I have multiple compressed files and each compressed file contains 8 xml files of size 5-10kb. I took this data for testing purpose otherwise live data has 1000s of xml files. I wrote map only program to uncompress the compressed file for(FileStatus status : status_list){ this.unzip(status.getPath().toString() , DestPath, fs); } This method will create file and read uncompressed data FSDataOutputStream out = fs.create(new Path(filePath)); byte[] bytesIn = new byte[BUFFER_SIZE]; int read = 0;

问题 I was trying to programmatically Load a dynamodb table into HDFS (via java, and not hive), I couldnt find examples online on how to do it, so thought I'd download the jar containing org.apache.hadoop.hive.dynamodb and reverse engineer the process. Unfortunately, I couldn't find the file as well :(. Could someone answer the following questions for me (listed in order of priority). Java example that loads a dynamodb table into HDFS (that can be passed to a mapper as a table input format). the

问题 Can somebody give one good example link for mapreduce with Hbase? My requirement is run mapreduce on hdfs file and store reducer output to hbase table. Mapper input will be hdfs file and output will be Text,IntWritable key value pairs. Reducers output will be Put object ie add reducer Iterable IntWritable values and store in hbase table. 回答1: Here is the code which will solve your problem Driver HBaseConfiguration conf = HBaseConfiguration.create(); Job job = new Job(conf,"JOB_NAME"); job