JMeter for Scalability Testing

Question:

In on of your own blog post, you have indicated the use of JMeter for Stress Testing a Game Application. I have a web application to be tested for its scalability. Do you recommend using JMeter for simulating load? You may also share some thoughts on its ease of setting up and usage and generally about Scalability testing. You may also recommend using any other tools together with JMeter.

Question By: Natarajan Ganesh

Response:

Scalability testing is about testing how the application scales in or out under different load conditions, and yes we need tools to simulate the load. It is about specifically testing the deployment model of the application as to how it makes use of additional computing resources when the load increases. Needless to mention, it involves testing both scale up and scale down. The actual test cases for scalability testing depend on the application design and architecture as to how it is expected to scale.

For example, in case of a cluster of application servers used, the test case should be to verify that the load on all the servers in the cluster are evenly distributed or as designed and that no server in the cluster is idles out when one or more other servers are peaking beyond a threshold. Another related test case could be to examine the application behavior when one of the server in the cluster is pulled out.

Thus scalability testing involves in addition to simulating required load or stress on the application, examining whether the scale up or down happens as designed or architected.

Yes, JMeter is a good tool for simulating the necessary load or stress on the application. Setting up JMeter and using it is easy and intuitive. The following simple steps would help you to get JMeter up and running the tests on a Windows box:

1. Make sure that you have JRE or JDK installed the bin folder is included in the system path.
2. Navigate to the bin folder of the JMeter installation folder and run the JMeter.bat. Just in case if it errors out, view or edit the JMeter.bat file to see if there is any other settings that need to be modified.
3. Right Click on the Test Plan in the vertical explorer pane on the left and add a Thread Group (Add -> Threads -> Thread Group).
4. Right Click on the newly added thread group and add a Sampler -> HTTP Request. In the resulting window make sure that you fill out appropriate vaules. Repeat this step to add as many HTTP Requests to be sampled.
5. Use an appropriate Listener to gather the data. This can be done again by adding a Listener to the Thread Group.

You could observe from the Add menu that you have options to add configuration elements, pre and post processors, assertions and logic controllers. Depending on your test scenario, use a combination of these components an build your test plan accordingly. Consult the JMeter documentation to to know more about effectively using JMeter.

While JMeter is just a tool simulate the stress or load, you need tools to gather server perormance data and as well as the application performance. While the native performance monitoring tools on Windows could b very useful, for Linux, you can try out NewRelic, a hosted remote monitoring tool. As I have described in one of my blog post, the application should have been designed to generate necessary data for further review and examination to spot probable or potential bottlenecks that need to be further tweaked.

Good luck with your testing.