Go back —> Tutorials

How to use Topologies in an experiment script

This feature is only available in NodeHandler v4 and above.

Before going through this tutorial, you should know how to install a disk image.

You should also have installed a disk image with Node Agent v4 on the nodes of the testbed you are using (e.g. "baseline-7.11.ndz").

Goal

In this tutorial, you will learn a simple way to define and use topology in your experiments.

As explained here, after installing an image on all the nodes of a testbed, 3 default topologies will be generated. One of them (system:topo:active) defines all the nodes that were correctly imaged. In other words, it contains a list of all nodes on the testbed that are currently working and have the requested disk image.

In this tutorial experiment, you will use this default active topology to create your own topologies to use in your experiments.

This experiment is given in the attached script tut_topo_1.rb​.

This file contains extensive comments that should help you understand the different steps involved in defining and using topologies. For more information on the basics of writing and using an experiment script, please refer to the previous tutorials, here and here.

Detailed information on the available commands to define a topology in an experiment script can be found here.

To run this example script, use the following command:

 nodehandler4 tut_topo_1

(This assumes that you previously logged in to the 'grid' testbed, and imaged its nodes with the "baseline-7.11.ndz" image, thus you should have a "system_topo_active_grid.rb" file in your home directory.)

The experiment screen output should then look like this​. And the experiment log file should look like this​.

You can also access the results of this particular experiment example in the MySQL database, using the experiment ID: "grid_2007_08_27_20_45_37" (please refer to this page for more information on accessing the results).

More…

This other script tut_topo_1_more.rb​ contains a version of the above script with more optional features.