Tag Archives: java

Database Access with Apache Hadoop

Categories: General Hadoop MapReduce

Editor’s note (added Nov. 9. 2013): Valuable data in an organization is often stored in relational database systems. To access that data, you could use external APIs as detailed in this blog post below, or you could use Apache Sqoop, an open source tool (packaged inside CDH) that allows users to import data from a relational database into Apache Hadoop for further processing. Sqoop can also export those results back to the database for consumption by other clients.

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The Small Files Problem

Categories: General Hadoop

Small files are a big problem in Hadoop — or, at least, they are if the number of questions on the user list on this topic is anything to go by. In this post I’ll look at the problem, and examine some common solutions.

Problems with small files and HDFS

A small file is one which is significantly smaller than the HDFS block size (default 64MB). If you’re storing small files,

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Securing an Apache Hadoop Cluster Through a Gateway

Categories: General Hadoop

(Added 6/4/2013) Please note the instructions below are deprecated. Please refer to the CDH4 Security Guide for up-to-date procedures.

A few weeks ago we ran an Apache Hadoop hackathon. ApacheCon participants were invited to use our 10-node Hadoop cluster to explore Hadoop and play with some datasets that we had loaded on in advance. One challenge we had to face was, how do we do this in a secure way?

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Configuring and Using Scribe for Hadoop Log Collection

Categories: Data Ingestion

As promised in my post about installing Scribe for log collection, I’m going to cover how to configure and use Scribe for the purpose of collecting Hadoop logs.  In this post I’ll describe how to create the Scribe Thrift client for use in Java, add a new log4j Appender to Hadoop, configure Scribe, and collect logs from each node in a Hadoop cluster. At the end of the post, I will link to all source and configuration files mentioned in this guide.

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