4. Immersion test

Soak Test

and The load test Mainly related to performance evaluation , and Pressure test Involving system stability under extreme conditions , Immersion testing involves reliability for a long time .

The immersion test revealed the performance and reliability problems caused by the system under pressure for a long time .

Reliability problems are often associated with errors 、 Memory leak 、 Insufficient storage quota 、 Incorrect configuration or infrastructure failure . Performance problems are often associated with incorrect database tuning 、 Memory leak 、 Resource leaks or large amounts of data .

Pass the immersion test , You can simulate traffic for a few days in just a few hours .

You usually run this test to ：

• Verify that your system is not affected by errors or memory leaks , These errors or memory leaks can cause crashes or restarts after running for hours .
• Verify that the expected application restart does not lose requests .
• Look for errors related to occasional competitive conditions .
• Make sure your database does not run out of allocated storage space and stop .
• Make sure that your logs do not run out of allocated disk storage space .
• Make sure that the external service you rely on does not stop working after executing a certain number of requests .

You may find that , Compared with the end of the test , Your application performs much better at the beginning of the test . If your database is not adjusted correctly , This usually happens . Adding indexes or allocating additional memory may help .

stay k6 Immersion test

We recommend that you configure the soaking test to be of the system capacity 80% about . If your system can process at most 500 Users , Then the soak test should be configured as 400 individual VU.

The duration of the soak test shall be in hours . We suggest you start with 1 The hour test begins , After success, extend it to a few hours . Some mistakes are related to time , Independent of the total number of requests executed .

sample-soak-test.js

import http from 'k6/http';
import {
     sleep } from 'k6';

export let options = {
    
  stages: [
    {
     duration: '2m', target: 400 }, // ramp up to 400 users
    {
     duration: '3h56m', target: 400 }, // stay at 400 for ~4 hours
    {
     duration: '2m', target: 0 }, // scale down. (optional)
  ],
};

const API_BASE_URL = 'https://test-api.k6.io';

export default function () {
    
  http.batch([
    ['GET', `${
      API_BASE_URL}/public/crocodiles/1/`],
    ['GET', `${
      API_BASE_URL}/public/crocodiles/2/`],
    ['GET', `${
      API_BASE_URL}/public/crocodiles/3/`],
    ['GET', `${
      API_BASE_URL}/public/crocodiles/4/`],
  ]);

  sleep(1);
}

Soaking test VU The chart should be as follows ：

Warning ！

Cost estimate before starting the soaking test

The soak test can simulate normal flow for days or weeks in a few hours . This means that your infrastructure and supplier costs can be high .

If you are testing the website , Then we should consider CDN Excluded from the test .

If your system uses external services , You may need to calculate the cost before starting the test .

When to do the soaking test ？

Immersion testing can help you find long-term errors and reliability problems . Many complex systems have errors of this nature .

You should perform the soak test after the standard load test is successful , And when you perform the stress test, you find that your system is stable .

Immersion testing is the last step in building a reliable system .

Refer to official documentation

Official document address : https://k6.io/docs/