tests/stress_tests/file_uploads.js

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

// 1. Open the file as binary outside the default function
const testFile = open('./small_file.pdf', 'b'); 

export const options = {
  scenarios: {
    my_spike_test: {
      executor: 'per-vu-iterations',
      vus: 80,
      iterations: 1,
    },
  },
};

export default function () {
  sleep(Math.random() * 10);
  const url = __ENV.URL;

  for (let i = 0; i < 3; i++) {
    // 2. Construct Multipart Form Data
    // We wrap the file and the JSON fields into a single data object
    const data = {
      file: http.file(testFile, 'small_file.pdf', 'application/pdf'), // The file
      session_id: `VU${__VU}_${i}`,
    };

    // 3. Remove 'Content-Type': 'application/json'
    // k6 will automatically set the correct 'multipart/form-data' header with a boundary
    const res = http.put(url, data);

    check(res, { 'status is 200': (r) => r.status === 200 });
  }
}

// TEST RESULT ANALYSIS

// The average HTTP request duration varies greatly with the size of the uploaded file.
// The system supports very easily small uploaded files (15 KB for example). For that
// scenario, the average HTTP request duration was about 40ms

// However, the system cannot support 80 users sending 3 large files (8.5 MB). The
// requests simply timeout.

// SMALL FILES
//   █ TOTAL RESULTS

//     checks_total.......: 240     14.904509/s
//     checks_succeeded...: 100.00% 240 out of 240
//     checks_failed......: 0.00%   0 out of 240

//     ✓ status is 200

//     HTTP
//     http_req_duration..............: avg=43.66ms min=21.72ms med=36.84ms max=304.38ms p(90)=74.06ms p(95)=79.16ms
//       { expected_response:true }...: avg=43.66ms min=21.72ms med=36.84ms max=304.38ms p(90)=74.06ms p(95)=79.16ms
//     http_req_failed................: 0.00%  0 out of 240
//     http_reqs......................: 240    14.904509/s

//     EXECUTION
//     iteration_duration.............: avg=11.33s  min=6.22s   med=11.38s  max=16.1s    p(90)=15.18s  p(95)=15.8s
//     iterations.....................: 80     4.96817/s
//     vus............................: 3      min=3        max=80
//     vus_max........................: 80     min=80       max=80

//     NETWORK
//     data_received..................: 446 kB 28 kB/s
//     data_sent......................: 3.8 MB 234 kB/s




// running (00m16.1s), 00/80 VUs, 80 complete and 0 interrupted iterations
// my_spike_test ✓ [======================================] 80 VUs  00m16.1s/10m0s  80/80 iters, 1 per VU


// LARGE FILES
// A list of error messages (request timeout) appears.