HDFS Regular Expression File Reader Input Adapter Sample

About This Sample

This sample demonstrates the use of the StreamBase® Regular Expression File Reader for Apache Hadoop Distributed File System (HDFS) in a StreamBase application that processes a text log file, storing the information extracted from the log in a query table. The log file is typical of a server log: it contains information about user logins, as well as other, spurious information. The format of the log file means it is not particularly suited to direct use in an application. It does not, for example, consist of CSV records that are ready to be turned into tuples; it must be parsed first and useful information extracted. Because the log file is text- and line-oriented, it is well suited to parsing using regular expressions.

Keep in mind that it is difficult to observe all log reading activities. The input adapter begins reading the input file and outputting tuples as soon as the application starts, before StreamBase Studio or external dequeuers have time to connect to the output of the reader. However, the application itself is fully functional, and all tuples read from the input file will be present in the query table.

Initial Setup

You must open the RegexReader.sbapp file in the src/main/eventflow/packageName folder. Select the Parameters tab and edit the value to represent both your current HDFS setup and where you would like to store the sample data.

The samplelog.txt file used in the sample must be placed on your HDFS file system in the location you specified in the Parameters tab before this sample can run.

Importing This Sample into StreamBase Studio

In StreamBase Studio, import this sample with the following steps:

  • From the top-level menu, click File>Import Samples and Community Content.

  • Enter hdfs to narrow the list of options.

  • Select HDFS Regular expression file input adapter from the Large Data Storage and Analysis category.

  • Click Import Now.

StreamBase Studio creates a project for the sample.

Running This Sample in StreamBase Studio

  1. In the Project Explorer view, open the sample you just loaded.

    If you see red marks on a project folder, wait a moment for the project to load its features.

    If the red marks do not resolve themselves after a minute, select the project, right-click, and select Maven>Update Project from the context menu.

  2. Open the src/main/eventflow/packageName folder.

  3. Open the RegexReader.sbapp file and click the Run button. This opens the SB Test/Debug perspective and starts the module.

  4. Select the Manual Input tab.

  5. Enter joe, fred, bob, or max for Username, and click Send Data.

  6. The Output Streams view shows the time and IP address for the last queried user, according to the log.

  7. When done, press F9 or click the Terminate EventFlow Fragment button.

Sample Location

When you load the sample into StreamBase® Studio, Studio copies the sample project's files to your Studio workspace, which is normally part of your home directory, with full access rights.


Load this sample in StreamBase® Studio, and thereafter use the Studio workspace copy of the sample to run and test it, even when running from the command prompt.

Using the workspace copy of the sample avoids permission problems. The default workspace location for this sample is:


See Default Installation Directories for the default location of studio-workspace on your system.