Connect to HDFS Data in Ruby

The CData ODBC Driver for HDFS makes it easy to integrate connectivity to live HDFS data in Ruby. This article shows how to create a simple Ruby app that connects to HDFS data, executes a query, and displays the results.

Create an ODBC Connection to HDFS Data

If you have not already, first specify connection properties in an ODBC DSN (data source name). This is the last step of the driver installation. You can use the Microsoft ODBC Data Source Administrator to create and configure ODBC DSNs.

In order to authenticate, set the following connection properties:

• Host: Set this value to the host of your HDFS installation.
• Port: Set this value to the port of your HDFS installation. Default port: 50070

Installing Ruby and Necessary Gems

If you do not have Ruby installed, refer to the Ruby installation page. With Ruby installed, you will need to install the ruby-dbi, dbd-odbc, and ruby-odbc gems:

gem install dbi
gem install dbd-odbc
gem install ruby-odbc

Create a Ruby App with Connectivity to HDFS Data

Create a new Ruby file (for example: HDFSSelect.rb) and open it in a text editor. Copy the following code into your file:

#connect to the DSN
require 'dbi'
cnxn = DBI.connect('DBI:ODBC:CData HDFS Source','','')

#execute a SELECT query and store the result set
resultSet = cnxn.execute("SELECT FileId, ChildrenNum FROM Files WHERE FileId = '119116'")

#display the names of the columns
resultSet.column_names.each do |name|
 print name, "\t"
end
puts

#display the results
while row = resultSet.fetch do
 (0..resultSet.column_names.size - 1).each do |n|
 print row[n], "\t"
 end
 puts
end
resultSet.finish

#close the connection
cnxn.disconnect if cnxn

With the file completed, you are ready to display your HDFS data with Ruby. To do so, simply run your file from the command line:

ruby HDFSSelect.rb

Writing SQL-92 queries to HDFS allows you to quickly and easily incorporate HDFS data into your own Ruby applications. Download a free trial today!