Loop Controller

Part of the Logic Controllers category. Also documented in context in the full Component Reference.

TL;DR: the Loop Controller repeats its children a fixed number of times (or forever) within a single thread iteration — the basic building block for “do this sequence N times” inside a larger test plan.

If you add Generative or Logic Controllers to a Loop Controller, JMeter will loop through them a certain number of times, in addition to the loop value you specified for the Thread Group. For example, if you add one HTTP Request to a Loop Controller with a loop count of two, and configure the Thread Group loop count to three, JMeter will send a total of 2 * 3 = 6 HTTP Requests.

Note

JMeter will expose the looping index as a variable named __jm__<Name of your element>__idx. So for example, if your Loop Controller is named LC, then you can access the looping index through \${__jm__LC__idx}. Index starts at 0

Name	Required	Description
Name	No	Descriptive name for this controller that is shown in the tree.
Loop Count	Yes, unless “Forever” is checked	The number of times the subelements of this controller will be iterated each time through a test run. The value -1 is equivalent to checking the Forever toggle. Special Case: The Loop Controller embedded in the Thread Group element behaves slightly different. Unless set to forever, it stops the test after the given number of iterations have been done. :::note When using a function in this field, be aware it may be evaluated multiple times. Example using [__Random](/functions/random/) will evaluate it to a different value for each child samplers of Loop Controller and result into unwanted behaviour. :::

Looping Example

Download this example (see Figure 4). In this example, we created a Test Plan that sends a particular HTTP Request only once and sends another HTTP Request five times.

Figure 4 - Loop Controller Example

We configured the Thread Group for a single thread and a loop count value of one. Instead of letting the Thread Group control the looping, we used a Loop Controller. You can see that we added one HTTP Request to the Thread Group and another HTTP Request to a Loop Controller. We configured the Loop Controller with a loop count value of five.

JMeter will send the requests in the following order: Home Page, News Page, News Page, News Page, News Page, and News Page.

Note

Note, the File Reporter is configured to store the results in a file named “loop-test.dat” in the current directory.

Common gotchas

• “Forever” here means “forever within this thread’s iteration,” not “forever for the whole test” — the enclosing Thread Group’s loop count still governs the outer repetition.
• Nesting a Loop Controller inside another Loop Controller multiplies iterations (outer × inner) — a common source of accidentally-huge request counts when someone forgets an existing outer loop.
• For conditional repetition instead of a fixed count, use While Controller; for a single conditional branch, use If Controller.
• See Logic Controllers & Flow Control for how loop, branch, and grouping controllers combine in a realistic test plan.

Related

• Logic Controllers & Flow Control
• Full Component Reference
• Functions and Variables