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k6-docs

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SKILL.md

Grafana k6 Documentation Access

Overview

This skill enables access to the latest official Grafana k6 documentation for writing and debugging load testing scripts. k6 is a modern load testing tool built for performance testing APIs, microservices, and websites.

When to Use This Skill

Use this skill when:

  • Writing new k6 load testing scripts
  • Debugging existing k6 test code
  • Looking up k6 API methods and their parameters
  • Understanding k6 test lifecycle hooks
  • Learning about k6 metrics and thresholds
  • Implementing k6 checks and custom metrics
  • Using k6 extensions or modules
  • Troubleshooting k6 test execution issues

Core Capabilities

1. Documentation Access

Access the latest k6 documentation using the WebFetch tool:

Primary documentation URLs:

Common API reference URLs:

Usage pattern:

Use WebFetch with the appropriate documentation URL and a focused prompt like:
- "Show me the API reference for http.post method"
- "Explain how to use checks in k6"
- "Show examples of custom metrics"

2. Common k6 Patterns

Basic HTTP GET test:

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

export const options = {
  vus: 10,
  duration: '30s',
};

export default function () {
  const res = http.get('https://test.k6.io');
  check(res, {
    'status is 200': (r) => r.status === 200,
  });
  sleep(1);
}

HTTP POST with JSON:

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

export default function () {
  const url = 'https://httpbin.test.k6.io/post';
  const payload = JSON.stringify({
    name: 'test',
  });
  const params = {
    headers: {
      'Content-Type': 'application/json',
    },
  };

  const res = http.post(url, payload, params);
  check(res, {
    'status is 200': (r) => r.status === 200,
  });
}

Ramp-up + steady + ramp-down stages with thresholds:

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

export const options = {
  stages: [
    { duration: '1m', target: 100 }, // ramp up to 100 VUs
    { duration: '3m', target: 100 }, // steady at 100 VUs
    { duration: '1m', target: 0 },   // ramp down to 0
  ],
  thresholds: {
    http_req_duration: ['p(95)<500'], // p95 latency < 500ms
    http_req_failed: ['rate<0.01'],   // error rate < 1%
    checks: ['rate>0.99'],            // 99%+ checks pass
  },
};

export default function () {
  const res = http.get(`${__ENV.BASE_URL || 'https://test.k6.io'}/api/users`);
  check(res, { 'status is 200': (r) => r.status === 200 });
  sleep(1);
}

Threshold syntax cheatsheet (the most-used metrics):

  • http_req_duration: ['p(95)<500'] — 95th percentile under 500ms
  • http_req_failed: ['rate<0.01'] — failure rate under 1%
  • checks: ['rate>0.99'] — at least 99% of check() calls pass
  • iteration_duration: ['avg<1000'] — average iteration under 1s

Failed check() calls do NOT increment http_req_failed; that metric only tracks HTTP-level failures (network errors, 5xx). Use checks threshold to enforce assertion success rate.

3. Documentation Search Strategy

When searching for specific k6 functionality:

  1. Start broad: Use WebSearch to find relevant documentation pages

    • Example: "k6 load testing custom metrics documentation"

  2. Then go specific: Use WebFetch on the most relevant documentation URL

  3. For API methods: Navigate to the JavaScript API section

  4. For how-to guides: Check the "Using k6" section

4. Key k6 Concepts

Test lifecycle:

  • init context: Load-time code (imports, options)
  • setup(): Runs once before tests
  • default function(): VU code, runs repeatedly
  • teardown(): Runs once after tests

Load options:

  • vus: Number of virtual users
  • duration: Test duration
  • iterations: Total iterations across all VUs
  • stages: Ramping pattern
  • thresholds: Pass/fail criteria

HTTP methods:

  • http.get(), http.post(), http.put(), http.delete()
  • http.batch() for parallel requests

Checks vs Thresholds:

  • check(): Validates conditions, doesn't stop test
  • thresholds: Define pass/fail criteria, can abort test

Workflow

  1. Identify the need: Determine what k6 functionality is required
  2. Search documentation: Use WebSearch or directly access known doc URLs
  3. Fetch specific pages: Use WebFetch to get detailed information
  4. Implement code: Write k6 test code based on documentation
  5. Validate: Check against examples and best practices in docs

Best Practices

  • Always check the latest documentation URL structure (grafana.com/docs/k6/latest/)
  • For complex scenarios, look for examples in the Examples section
  • When troubleshooting, check both the API reference and the Using k6 guides
  • Use WebSearch first if unsure which documentation page to fetch
  • Reference multiple documentation pages if implementing complex features

Common Documentation Sections

Topic URL Pattern
Main docs https://grafana.com/docs/k6/latest/
JavaScript API https://grafana.com/docs/k6/latest/javascript-api/{module}/
HTTP module https://grafana.com/docs/k6/latest/javascript-api/k6-http/
Examples https://grafana.com/docs/k6/latest/examples/
Test lifecycle https://grafana.com/docs/k6/latest/using-k6/test-lifecycle/
Thresholds https://grafana.com/docs/k6/latest/using-k6/thresholds/
Options https://grafana.com/docs/k6/latest/using-k6/k6-options/
Metrics https://grafana.com/docs/k6/latest/using-k6/metrics/
Checks https://grafana.com/docs/k6/latest/javascript-api/k6/check/

Notes

  • This skill does not bundle k6 documentation locally; it fetches the latest version online
  • Always verify that fetched documentation is current by checking the URL includes /latest/
  • For version-specific documentation, replace /latest/ with the specific version number
  • k6 documentation is comprehensive and well-organized; use the table of contents for navigation
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