I am trying to insert header.txt as first line into data.txt without using getmerge. Getmerge copies to local and inserts into third file. But I want in HDFS only
Header.txt
Head1,Head2,Head3
Data.txt
100,John,28
101,Gill,25
102,James,29
I want output in Data.txt file only like below :
Data.txt
Head1,Head2,Head3
100,John,28
101,Gill,25
102,James,29
Please suggest me whether can we implement in HDFS only ?
HDFS supports a concat (short for concatenate) operation in which two files are merged together into one without any data transfer. It will do exactly what you are looking for. Judging by the file system shell guide documentation, it is not currently supported from the command line, so you will need to implement this in Java:
FileSystem fs = ...
Path data = new Path("Data.txt");
Path header = new Path("Header.txt");
Path dataWithHeader = new Path("DataWithHeader.txt");
fs.concat(dataWithHeader, header, data);
After this, Data.txt and Header.txt both cease to exist, replaced by DataWithHeader.txt.
Thanks for your reply.
I got other way like :
Hadoop fs cat hdfs_path/header.txt hdfs_path/data.txt | Hadoop fs -put - hdfs_path/Merged.txt
This is having drawback as cat command reads complete data which impacts performance.
Related
I have a text file in HDFS which would have records like below. The number of lines in file may vary every time.
hdfs://myfile.txt
file_name_1
file_name_2
file_name_3
I have the below hdfs directory and file structure like below.
hdfs://myfolder/
hdfs://myfolder/file1.csv
hdfs://myfolder/file2.csv
hdfs://myfolder/file3.csv
Using shell script I am able to count the number of files in HDFS directory and number of lines available in my HDFS text file. Only if the count matches between the number of files in directory and number of records in my text file, I am going to proceed further with the process.
Now, i am trying to rename hdfs://myfolder/file1.csv to hdfs://myfolder/file_name_1.csv using the first record from my text file.
Second file should be renamed to hdfs://myfolder/file_name_2.csv and third file to hdfs://myfolder/file_name_3.csv
I have difficulty in looping through both the text file and also the files in HDFS directory.
Is there an optimal way to achieve this using shell script.
You cannot do this directly from HDFS, you'd need to stream the file contents, then issue individual move commands.
e.g.
#!/bin/sh
COUNTER = 0
for file in $(hdfs dfs -cat file.txt)
do
NAME = $(sed $file ...) # replace text, as needed. TODO: extract the extension
hdfs dfs -mv file "$NAME_${COUNTER}.csv" # 'csv' for example - make sure the extension isn't duplicated!!
COUNTER = $((COUNTER + 1)
done
I have a file that is about 1gb in size and about 19955931 line long, when I pipe it into hadoop it returns empty data.
However if I created a new file using head with the same amount of line
head -19955931 my.log > my_new_copy.log
Hadoop returns the correct non empty data.
I am completely perplexed by this behavior, is hadoop expecting a specific meta file format?
I am trying to find the files which are less than block size in HDFS.
By using OIV i converted the fsimage into text file with delimiters like below.
hdfs oiv_legacy -i /tmp/fsimage -o /tmp/fsimage_$RUNDATE/fsimage.txt -p Delimited -delimiter '#'
Since fsimage has lot of data. From this how to find the file name and file size of each and every file in HDFS.
Can anyone please help.
Thanks in advance....
Take a look at scripts at the end of this documentation.
Starting from:
A = LOAD '$inputFile' USING PigStorage('\t') AS (path:chararray,
replication:int,
modTime:chararray,
accessTime:chararray,
blockSize:long,
numBlocks:int,
fileSize:long,
NamespaceQuota:int,
DiskspaceQuota:int,
perms:chararray,
username:chararray,
groupname:chararray);
-- Grab the pathname and filesize
B = FOREACH A generate path, fileSize;
-- Save results
STORE B INTO '$outputFile';
hadoop fs -find /tmp/fsimage size 64 -print
Note:I am using MapR Hadoop.The syntax might wary if its Cloudera,Hortonworks.
I have two MapReduce jobs which produce files in two separate directories which look like so:
Directory output1:
------------------
/output/20140102-r-00000.txt
/output/20140102-r-00000.txt
/output/20140103-r-00000.txt
/output/20140104-r-00000.txt
Directory output2:
------------------
/output-update/20140102-r-00000.txt
I want to merge these two directories together in a new directory /output-complete/ where the 20140102-r-00000.txt replaces the original file in the /output directory and all of the "-r-0000x" is removed from the file name. The two original directories will now be empty and the resulting directory should look as follows:
Directory output3:
-------------------
/output-complete/20140102.txt
/output-complete/20140102.txt
/output-complete/20140103.txt
/output-complete/20140104.txt
What is the best way to do this? Can I use only HDFS shell commands? Do I need to create a java program to traverse both directories and do the logic?
you can use pig ...
get_data = load '/output*/20140102*.txt' using Loader()
store get_data into "/output-complete/20140102.txt"
or HDFS Command...
hadoop fs -cat '/output*/20140102*.txt' > output-complete/20140102.txt
single qoutes may not work, then try with double quotes
You can use hdfs command -getMerge for merging hdfs files.
I tried deploying 20- news group example with mahout, it seems working fine. Out of curiosity I would like to dig deep into the model statistics,
for example: bayes-model directory contains the following sub directories,
trainer-tfIdf trainer-thetaNormalizer trainer-weights
which contains part-0000 files. I would like to read the contents of the file for better understanding, cat command doesnt seems to work, it prints some garbage.
Any help is appreciated.
Thanks
The 'part-00000' files are created by Hadoop, and are in Hadoop's SequenceFile format, containing values specific to Mahout. You can't open them as text files, no. You can find the utility class SequenceFileDumper in Mahout that will try to output the content as text to stdout.
As to what those values are to begin with, they're intermediate results of the multi-stage Hadoop-based computation performed by Mahout. You can read the code to get a better sense of what these are. The "tfidf" directory for example contains intermediate calculations related to term frequency.
You can read part-0000 files using hadoop's filesystem -text option. Just get into the hadoop directory and type the following
`bin/hadoop dfs -text /Path-to-part-file/part-m-00000`
part-m-00000 will be printed to STDOUT.
If it gives you an error, you might need to add the HADOOP_CLASSPATH variable to your path. For example, if after running it gives you
text: java.io.IOException: WritableName can't load class: org.apache.mahout.math.VectorWritable
then add the corresponding class to the HADOOP_CLASSPATH variable
export HADOOP_CLASSPATH=/src/mahout/trunk/math/target/mahout-math-0.6-SNAPSHOT.jar
That worked for me ;)
In order to read part-00000 (sequence files) you need to use the "seqdumper" utility. Here's an example I used for my experiments:
MAHOUT_HOME$: bin/mahout seqdumper -s
~/clustering/experiments-v1/t14/tfidf-vectors/part-r-00000
-o ~/vectors-v2-1010
-s is the sequence file you want to convert to plain text
-o is the output file