Execution context variables

In some cases, it's really useful to have information about the script's current test-execution state. For example, you might want to

• Have different VUs run different test logic
• Use different data for each VU and iteration
• Figure out the stage that a test is in

To solve these issues, you can use execution context variables.

k6/execution

The k6/execution module exposes details about the current execution state, such as the name of the currently executed scenario, how many VUs are currently active, and more. The module provides test-execution information via three properties:

k6 v0.34.0 introduced the k6/execution module. If you are using a version k6 that does not have this module, refer to the __VU and __ITER section.

Example: log all context variables

If you want to experiment with what each context variable looks like as a test runs, you can copy this template literal into one of your test scripts.

Note that this omits the abort variable, since that function would abort the test.

1import exec from 'k6/execution';
2
3export default function () {
4  console.log(`Execution context
5
6Instance info
7-------------
8Vus active: ${exec.instance.vusActive}
9Iterations completed: ${exec.instance.iterationsCompleted}
10Iterations interrupted:  ${exec.instance.iterationsInterrupted}
11Iterations completed:  ${exec.instance.iterationsCompleted}
12Iterations active:  ${exec.instance.vusActive}
13Initialized vus:  ${exec.instance.vusInitialized}
14Time passed from start of run(ms):  ${exec.instance.currentTestRunDuration}
15
16Scenario info
17-------------
18Name of the running scenario: ${exec.scenario.name}
19Executor type: ${exec.scenario.executor}
20Scenario start timestamp: ${exec.scenario.startTime}
21Percenatage complete: ${exec.scenario.progress}
22Iteration in instance: ${exec.scenario.iterationInInstance}
23Iteration in test: ${exec.scenario.iterationInTest}
24
25Test info
26---------
27All test options: ${exec.test.options}
28
29VU info
30-------
31Iteration id: ${exec.vu.iterationInInstance}
32Iteration in scenario: ${exec.vu.iterationInScenario}
33VU ID in instance: ${exec.vu.idInInstance}
34VU ID in test: ${exec.vu.idInTest}
35VU tags: ${exec.vu.tags}`);
36}

For detailed reference, refer to the k6/execution module.

Examples and use cases

• Getting unique data once
• Timing operations
• Executing different code blocks

1import http from 'k6/http';
2import { sleep } from 'k6';
3export default function () {
4  http.get('http://test.k6.io');
5  console.log(`VU: ${__VU}  -  ITER: ${__ITER}`);
6  sleep(1);
7}

1import http from 'k6/http';
2import { sleep } from 'k6';
3export default function () {
4  const email = `user+${__VU}@mail.com`;
5  const payload = JSON.stringify({ email: email, password: 'test' });
6  const params = { headers: { 'Content-Type': 'application/json' } };
7  http.post('http://test.k6.io/login', payload, params);
8  console.log(email);
9  // .. continue the user flow
10  sleep(1);
11}

k6 Cloud environment variables

If you run tests in k6 Cloud, you have additional environment variables that tell you the server, load zone, and distribution of the currently running test. Read about cloud environment variables.