MapReduce-Tutorial

This tutorial bases on Dr. Middelkoop’s scripts to introduce how to run MapReduce job on MRI system of University of Missouri, Columbia. The system is a high-performance computational infrastructure for inter-campus research collaboration.

1. Cluster configuration

This Hadoop cluster includes 10 nodes: 10 * 128 Gb (72 vcores), Dell R730 with 2 x E5-2660v3 (2.6Ghz 10-Core), CentOS 5

First, you use Putty to connect to Linux Server, and logon with your mri account and your private key. (http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html)

After you log on, you change directory to Hadoop folder and list its content.

$ cd Hadoop
$ ls

There are three necessary files to initialize Hadoop cluster:

env.sh: contains environmental variables
dfs.sh: contains configuration of name node (to store data on Hadoop file system)
yarn.sh: contains configuration of computational node (YARN is MapReduce 2.0)

Support file:

Readme.md: includes scripts to execute tasks

MapReduce 2.0 (YARN)

Before setting configuration, if you want to learn more about MapReduce 2.0 (YARN), you can follow this link: http://ercoppa.github.io/HadoopInternals/AnatomyMapReduceJob.html

Instead of changing directly Hadoop cluster’s configuration, we use these files to set configuration parameters each time we initialize the system.

env.sh

env.sh sets path to JAVA HOME, HADOOP HOME And HEAPSIZE memory for HADOOP. This number must be consistent with values of HEAPSIZE in file dfs.sh and yarn.sh

dfs.sh

dfs.sh configures how to run data node for Hadoop cluster. The HEAPSIZE here equals previous value in env.sh.

dfs.sh also configures block size of Hadoop file system (default value is 128mb). This size will decide how many parts each input file will be split to handle in parallel.

yarn.sh

yarn.sh sets configuration for computational node.

HEAPSIZE: 65000 mb (larger 1000 mb than node memory for safety)
    |____ Node manager memory: 64000 mb (each node can have many computational containers)
                        |____ (Computational) container memory: from 8000 mb to 16000 mb (must be larger than Map + Reduce memory)
                                        |____ Map: 7000 mb
                                                        |____ Java virtual machine memory (opts): 3000 mb
                                                        |____ Memory for computational data: 4000 mb
                                        |____ Reduce: 9000 mb
                                                        |____ Java virtual machine memory (opts): 3000 mb
                                                        |____ Memory for computational data: 6000 mb 

Depend on job requirements, we need to set up appropriate memory. Otherwise, the tasks or containers can be crashed, made the job killed or looped.

2. Turn on cluster

a. Name node

Form the current Putty windows, open Readme.md file to view instruction and initialize name node

$ cat Readme.md
$ . env.sh
$ srun -p GPU -N 10 ./dfs.sh

b. Computational node

Now open another Putty window for computational node

$ cat Readme.md
$ . env.sh
$ srun -p GPU -N 10 ./yarn.sh

3. Forward port to monitor remote job on local machine (by web browser)

a. On Windows

Open the third Putty window for proxy to monitor Hadoop jobs

Input port 8088 you want to forward on local computer, and remote server

b. On Linux

Open Terminal and use this command:

$ slogin -L 8088:c11u21:8088 mri1.rnet.missouri.edu

4. Prepare data and run MapReduce job

Open the last Putty window for you to work

You create input, output folder on hdfs system. And then copy your local data on Linux server to name node (data node - hdfs).

# Create input and output folder
$ hadoop fs -mkdir /input
$ hadoop fs -mkdir /output
$ hadoop fs -mkdir /output/cloth_output_sample

# Copy data to input folder
$ hadoop fs -copyFromLocal cloth_train_sample1.txt /input
$ hadoop fs -copyFromLocal cloth_train_sample2.txt /input
$ hadoop fs -copyFromLocal cloth_test_sample.txt /input

Clone your code on Github to build MapReduce program.

# Clone
$ git clone git@github.com:nguyen14ck/neuro_classifier

# Build
$ mvn clean dependency:copy-dependencies package

To run MapReduce, use this command: yarn jar jar_path input_paht output_path

jar file should be on local system, input and output files should be on hdfs

# Run job
$ yarn jar senti_classify.jar neuro.mre.senti_classify 2 /input/cloth_train_sample1.txt /input/cloth_train_sample2.txt /input/cloth_test_sample.txt /output/cloth_output_sample

5. Monitor MapReduce job and result

After input and excute job on master node, the console screen displays job id, number of splits, and progress as following image:

Open your browser and use the local address: http://127.0.0.1:8088/cluster/apps

In this example, input file was split into 24 parts. So we have 24 containers for computation, and 1 container for management (AM containter, or Application Master container). These 25 containers are still smaller than the max allowance (72). So all tasks were run completely in parallel.

Each container took 1 vcore and 8000 mb. And 24 * 8000 = 192000 mb are used. The AM container used less memory than other computational container (worker container). The memory used is about 195 Gb.

Finally, the job completed successfully after 50 minutes 07 seconds.