In a previous post I demonstrated a method to deploy a multi-node Hadoop cluster using Vagrant and Ansible. This post builds on that and shows how to deploy a Hadoop cluster with an arbitrary number of slave nodes in minutes on OpenStack. This process makes use of the OpenStack orchestration layer HEAT to provision the resources, after which Ansible use used to configure those resources. All the scripts to do this yourself is available on github to clone and fork: https://github.com/dwatrous/hadoop-multi-server-ansible I have recorded a video demonstrating the entire process, including scaling the......
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I’ve recently been involved with several groups interested in using Hadoop to process large sets of data, including use of higher level abstractions on top of Hadoop like Pig and Hive. What has surprised me most is that no one is automating their installation of Hadoop. In each case that I’ve observed they start by manually provisioning some servers and then follow a series of tutorials to manually install and configure a cluster. The typical experience seems to take about a week to setup a cluster. There is often a lot of wasted......
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In a previous post I illustrated the use of Hadoop to analyze Apache Tomcat log files (catalina.out). Below I perform the same Tomcat log analysis using PIG. The motivation behind PIG is the ability us a descriptive language to analyze large sets of data rather than writing code to process it, using Java or Python for example. PIG latin is the descriptive query language and has some similarities with SQL. These include grouping and filtering. Load in the data First I launch into the interactive local PIG command line, grunt. Commands are not......
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I read that Hadoop supports scripts written in various languages other than Java, such as Python. Since I’m a fan of python, I wanted to prove this out. It was my good fortune to find an excellent post by Michael Noll that walked me through the entire process of scripting in Python for Hadoop. It’s an excellent post and worked as written for me in Hadoop 2.2.0. How hadoop processes scripts from other languages (stdin/stdout) In order to accommodate scripts from other languages, hadoop focuses on standard in (stdin) and standard out (stdout).......
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The log rotation mechanism on my servers automatically compresses (gzip) the rotated log file to save on disk space. I discovered that Hadoop is already designed to deal with compressed files using gzip, bzip2 and LZO out of the box. This means that no additional work is required in the Mapper class to decompress. Here’s a snippet from the MapReduce output that shows 13/11/15 22:01:46 INFO mapred.MapTask: Processing split: hdfs://localhost/user/watrous/log_myhost.com/catalina.out-20131103.gz:0+3058954 13/11/15 22:01:46 INFO mapred.MapTask: Map output collector class = org.apache.hadoop.mapred.MapTask$MapOutputBuffer 13/11/15 22:01:46 INFO mapred.MapTask: (EQUATOR) 0 kvi 26214396(104857584) 13/11/15 22:01:46 INFO mapred.MapTask: mapreduce.task.io.sort.mb:......
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My previous hadoop example operated against the local filesystem, in spite of the fact that I formatted a local HDFS partition. In order to operate against the local HDFS partition it’s necessary to first start the namenode and datanode. I mostly followed these instructions to start those processes. Here’s the most relevant part that I hadn’t done yet. # Format the namenode hdfs namenode -format # Start the namenode hdfs namenode # Start a datanode hdfs datanode# Format the namenode hdfs namenode -format # Start the namenode hdfs namenode # Start a datanode......
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One of the Java applications I develop deploys in Tomcat and is load-balanced across a couple dozen servers. Each server can produce gigabytes of log output daily due to the high volume. This post demonstrates simple use of hadoop to quickly extract useful and relevant information from catalina.out files using Map Reduce. I followed Hadoop: The Definitive Guide for setup and example code. Installing Hadoop Hadoop in standalone mode was the most convenient for initial development of the Map Reduce classes. The following commands were executed on a virtual server running RedHat Enterprise......
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