Using JMeter

Using JMeter effectively consists of the following activities

Choosing A SamplerController

JMeter has two tabs - setup and run . Within setup , the default SamplerController is initially displayed. You will find a drop down select box that allows you to select any SamplerController you wish to use. When you make this selection, the appropriate GUI will be displayed.

The SamplerController determines the basic kind of sampling you will do. Choose the "Advanced HTTP tester" for advanced web page sampling, and the "Simple HTTP Tester" for testing single web pages quickly, and choose the "JDBC Base Sampler" to sample your database.

The available SamplerControllers are (Click links for more detailed information):

Creating Test Samples

A test sample represents an entry to be sampled. It holds all the information needed about conducting a sample. For instance, an HTTPTestSample might hold information about the URL to be hit, whether POST or GET is to be used, and what argument name-value pairs should be passed on. The Test Sample will present a GUI for the user to enter this information.

Creating test samples is dictated by the workings of the SamplerController you chose. In general, the SamplerController will display a list of test samples you've created, and you will be able to create more, and there may be different kinds of test samples you can create. See the link for the SamplerController you are using to find out what test samples are available to you and how to use them.

Choosing a delay

Delay represents the number of milliseconds JMeter pauses between samples in each sampling thread. There are a number of delay modules you can choose from on the setup panel, and they should be mostly self-explanatory. You may choose a timer for each thread group (actually, you must, or each thread group will use the default timer).

Managing Thread Groups

Thread groups are managed in the run panel.

By default, there is only one thread group to start. It is called "Group 1". You may simply use this one group, or you can add more groups by typing in the name of the group you wish to add above the list and hitting Enter . For each thread group, you can choose a number of threads from 1 to 20 (this can be changed in jmeter.properties). There is no limit on the number of thread groups you can have, except for the limitations of your machine, and how many threads it can handle.

The thread groups you add also become available as choices within your test samples you create. If you add a thread group (say "Group 2"), and then, from the setup panel, you create a new test sample, you will notice that both Group 1 and Group 2 show up in your list of thread groups to choose from. A particular test sample may be part of one or more thread groups. This allows you to set up two parallel groups of test samples that will execute simultaneously. The two test groups could, however, share a common test sample, such as a one-time login sample.

Thread groups are also important to visualizers, since you may choose a different visualizer for each thread group.

Note: if you are not clear on what "threadgroup" is referring to exactly, don't worry - you aren't alone. JMeter is no less powerful a tool if you only ever use the single default threadgroup. You may use any number of threads in your default threadgroup (by modifying jmeter.properties). Each thread represents a different "user" hitting your site. All test samples will be assigned to the single default thread group automatically if you never create an additional thread group. JMeter 1.6 will hopefull deal with this issue better.

Choosing a Visualizer

Visualizers are managed in the run panel in the section labeled Actions .

For each thread group, you may select a different visualizer. Visualizers show the timing data that JMeter collects during sampling. As you select different thread groups, the visualizer display switches to the visualizer you selected for that thread group. In this way, you can keep an eye on all your visualizers while JMeter runs.

Running the test script

Once you have chosen your sampler controller, created all your test samples, selected a delay, added any thread groups, and selected your visualizers, you simply choose "start" from the "Run" menu, or hit ctrl-s . To stop, choose "Stop" from the "Run" menu, or hit ctrl-. . Switch to the run panel to watch it run.




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