Performance Monitoring

Performance monitoring with k6 enables continuous validation of your applications in production environments. By running lightweight synthetic tests, you can proactively detect issues before they impact users.

Synthetic Monitoring Overview

Synthetic monitoring runs automated tests against your production systems at regular intervals to:

Validate Availability

Ensure your services are accessible and responding correctly

Monitor Performance

Track response times and performance metrics over time

Detect Regressions

Identify performance degradation after deployments

Test Critical Flows

Verify key user journeys work as expected

Creating Synthetic Tests

Synthetic tests should be lightweight and focused on critical functionality:

Basic Health Check

health-check.js

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

export const options = {
  vus: 1,
  duration: '30s',
  thresholds: {
    http_req_failed: ['rate<0.01'],
    http_req_duration: ['p(95)<1000'],
  },
};

export default function () {
  const res = http.get('https://api.example.com/health');
  
  check(res, {
    'API is available': (r) => r.status === 200,
    'Response time acceptable': (r) => r.timings.duration < 500,
    'Health status OK': (r) => r.json('status') === 'healthy',
  });
  
  sleep(5);
}

API Endpoint Monitoring

api-monitor.js

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

const errorRate = new Rate('api_errors');
const apiLatency = new Trend('api_latency');

export const options = {
  vus: 1,
  duration: '1m',
  thresholds: {
    'api_errors': ['rate<0.05'],
    'api_latency': ['p(95)<500'],
  },
};

const endpoints = [
  '/api/users',
  '/api/products',
  '/api/orders',
];

export default function () {
  for (const endpoint of endpoints) {
    const start = Date.now();
    const res = http.get(`https://api.example.com${endpoint}`);
    const duration = Date.now() - start;
    
    const success = check(res, {
      [`${endpoint} status 200`]: (r) => r.status === 200,
      [`${endpoint} has data`]: (r) => r.json().length > 0,
    });
    
    errorRate.add(!success, { endpoint });
    apiLatency.add(duration, { endpoint });
    
    sleep(1);
  }
}

Critical User Journey

user-journey-monitor.js

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

export const options = {
  vus: 1,
  duration: '1m',
  thresholds: {
    'checks{journey:login}': ['rate>0.95'],
    'checks{journey:browse}': ['rate>0.95'],
    'checks{journey:purchase}': ['rate>0.95'],
    'http_req_duration{journey:purchase}': ['p(95)<3000'],
  },
};

export default function () {
  let authToken;
  
  // Login
  group('User Login', function () {
    const loginRes = http.post('https://api.example.com/auth/login',
      JSON.stringify({ username: '[email protected]', password: 'secret' }),
      { 
        headers: { 'Content-Type': 'application/json' },
        tags: { journey: 'login' },
      }
    );
    
    check(loginRes, {
      'login successful': (r) => r.status === 200,
      'token received': (r) => r.json('token') !== undefined,
    }, { journey: 'login' });
    
    authToken = loginRes.json('token');
    sleep(1);
  });
  
  if (!authToken) return;
  
  const headers = {
    'Authorization': `Bearer ${authToken}`,
    'Content-Type': 'application/json',
  };
  
  // Browse products
  group('Browse Products', function () {
    const productsRes = http.get('https://api.example.com/products',
      { headers, tags: { journey: 'browse' } });
    
    check(productsRes, {
      'products loaded': (r) => r.status === 200,
      'has products': (r) => r.json('products').length > 0,
    }, { journey: 'browse' });
    
    sleep(2);
  });
  
  // Add to cart and purchase
  group('Purchase Flow', function () {
    const cartRes = http.post('https://api.example.com/cart',
      JSON.stringify({ productId: 123, quantity: 1 }),
      { headers, tags: { journey: 'purchase' } });
    
    check(cartRes, {
      'added to cart': (r) => r.status === 200,
    }, { journey: 'purchase' });
    
    sleep(1);
    
    const checkoutRes = http.post('https://api.example.com/checkout',
      JSON.stringify({ cartId: cartRes.json('cartId') }),
      { headers, tags: { journey: 'purchase' } });
    
    check(checkoutRes, {
      'checkout successful': (r) => r.status === 200,
      'order created': (r) => r.json('orderId') !== undefined,
    }, { journey: 'purchase' });
    
    sleep(1);
  });
}

Using Grafana Cloud Synthetic Monitoring

Grafana Cloud provides managed synthetic monitoring with k6:

Create a k6 test

Write a simple k6 test script focusing on critical functionality

Configure the check

Set up the check in Grafana Cloud with:

Check frequency (1-60 minutes)
Probe locations (multiple regions)
Alert thresholds

Set up alerts

Configure notifications for:

Availability issues
Performance degradation
Failed checks

Monitor dashboards

Use built-in dashboards to track:

Response times
Success rates
Geographic performance

Example Synthetic Monitoring Script

synthetic-check.js

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

export const options = {
  thresholds: {
    // Fail if more than 1% of requests fail
    http_req_failed: ['rate<0.01'],
    // Fail if 95% of requests take longer than 2 seconds
    http_req_duration: ['p(95)<2000'],
  },
};

export default function () {
  // Test homepage
  const homeRes = http.get('https://example.com');
  check(homeRes, {
    'homepage available': (r) => r.status === 200,
    'homepage loads fast': (r) => r.timings.duration < 1000,
  });
  
  // Test API
  const apiRes = http.get('https://api.example.com/health');
  check(apiRes, {
    'API available': (r) => r.status === 200,
    'API healthy': (r) => r.json('status') === 'ok',
  });
}

Scheduling Synthetic Tests

Cron Jobs
Kubernetes CronJob
GitHub Actions

# /etc/crontab
# Run every 5 minutes
*/5 * * * * k6 run --out influxdb=http://localhost:8086/k6 /path/to/health-check.js

apiVersion: batch/v1
kind: CronJob
metadata:
  name: k6-synthetic-monitor
spec:
  schedule: "*/5 * * * *"
  jobTemplate:
    spec:
      template:
        spec:
          containers:
          - name: k6
            image: grafana/k6:latest
            args:
            - run
            - --out
            - experimental-prometheus-rw
            - /scripts/health-check.js
            env:
            - name: K6_PROMETHEUS_RW_SERVER_URL
              value: "http://prometheus:9090/api/v1/write"
            volumeMounts:
            - name: scripts
              mountPath: /scripts
          restartPolicy: OnFailure
          volumes:
          - name: scripts
            configMap:
              name: k6-scripts

name: Synthetic Monitoring
on:
  schedule:
    - cron: '*/15 * * * *'  # Every 15 minutes
  workflow_dispatch:

jobs:
  synthetic-test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      
      - name: Run synthetic test
        uses: grafana/[email protected]
        env:
          K6_CLOUD_TOKEN: ${{ secrets.K6_CLOUD_TOKEN }}
        with:
          filename: tests/synthetic-check.js
          flags: --out cloud
      
      - name: Alert on failure
        if: failure()
        uses: dawidd6/action-send-mail@v3
        with:
          server_address: smtp.gmail.com
          server_port: 465
          username: ${{ secrets.MAIL_USERNAME }}
          password: ${{ secrets.MAIL_PASSWORD }}
          subject: Synthetic test failed
          body: The synthetic monitoring test has failed. Check the workflow for details.
          to: [email protected]

Monitoring Best Practices

Use Minimal Load

// Keep VUs low for production monitoring
export const options = {
  vus: 1,  // Single virtual user
  duration: '30s',
};

Synthetic monitoring should use minimal load to avoid impacting production users.

Set Realistic Thresholds

export const options = {
  thresholds: {
    // Allow some failures for transient issues
    http_req_failed: ['rate<0.05'],  // 5% error tolerance
    
    // Use percentiles, not averages
    http_req_duration: ['p(95)<1000', 'p(99)<2000'],
    
    // Monitor specific endpoints critically
    'http_req_duration{endpoint:critical}': ['p(95)<500'],
  },
};

Tag for Better Analysis

import http from 'k6/http';

export default function () {
  // Tag requests for filtering
  http.get('https://api.example.com/users', {
    tags: { 
      endpoint: 'users',
      criticality: 'high',
      region: 'us-east',
    },
  });
}

Monitor Multiple Regions

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

const regions = [
  { name: 'us-east', url: 'https://us-east.api.example.com' },
  { name: 'eu-west', url: 'https://eu-west.api.example.com' },
  { name: 'ap-south', url: 'https://ap-south.api.example.com' },
];

export default function () {
  for (const region of regions) {
    const res = http.get(`${region.url}/health`, {
      tags: { region: region.name },
    });
    
    check(res, {
      [`${region.name} available`]: (r) => r.status === 200,
    });
  }
}

Alerting Strategies

Threshold-Based Alerts

export const options = {
  thresholds: {
    // Alert if error rate exceeds 5%
    http_req_failed: [
      { threshold: 'rate<0.05', abortOnFail: false },
    ],
    
    // Alert if p95 latency exceeds 2 seconds
    http_req_duration: [
      { threshold: 'p(95)<2000', abortOnFail: false },
    ],
  },
};

Consecutive Failure Alerts

#!/bin/bash
# run-with-retry.sh

MAX_FAILURES=3
FAILURE_COUNT=0

while true; do
  if k6 run health-check.js; then
    FAILURE_COUNT=0
  else
    FAILURE_COUNT=$((FAILURE_COUNT + 1))
    
    if [ $FAILURE_COUNT -ge $MAX_FAILURES ]; then
      echo "ALERT: $MAX_FAILURES consecutive failures detected"
      # Send alert
      curl -X POST https://alerts.example.com/webhook \
        -H 'Content-Type: application/json' \
        -d '{"message": "Synthetic monitoring failed 3 times"}'
      FAILURE_COUNT=0
    fi
  fi
  
  sleep 300  # Wait 5 minutes
done

Visualization and Analysis

Grafana Dashboard Example

{
  "dashboard": {
    "title": "k6 Synthetic Monitoring",
    "panels": [
      {
        "title": "Availability",
        "targets": [
          {
            "expr": "1 - rate(k6_http_req_failed{job=\"synthetic-monitoring\"}[5m])"
          }
        ]
      },
      {
        "title": "Response Time (P95)",
        "targets": [
          {
            "expr": "histogram_quantile(0.95, k6_http_req_duration_bucket{job=\"synthetic-monitoring\"})"
          }
        ]
      },
      {
        "title": "Requests Per Minute",
        "targets": [
          {
            "expr": "rate(k6_http_reqs{job=\"synthetic-monitoring\"}[1m]) * 60"
          }
        ]
      }
    ]
  }
}

Prometheus Queries

# Availability percentage
100 * (1 - rate(k6_http_req_failed[5m]))

# P95 response time
histogram_quantile(0.95, rate(k6_http_req_duration_bucket[5m]))

# Error rate by endpoint
sum by (endpoint) (rate(k6_http_req_failed[5m]))

# Request duration trend
avg_over_time(k6_http_req_duration[1h])

Complete Monitoring Setup

production-monitor.js

import http from 'k6/http';
import { check, group, sleep } from 'k6';
import { Rate, Trend, Counter } from 'k6/metrics';

const availability = new Rate('availability');
const responseTime = new Trend('response_time');
const healthChecks = new Counter('health_checks');

export const options = {
  vus: 1,
  duration: '1m',
  thresholds: {
    'availability': ['rate>0.99'],
    'response_time': ['p(95)<1000', 'p(99)<2000'],
    'http_req_duration{check:critical}': ['p(95)<500'],
  },
};

const BASE_URL = __ENV.BASE_URL || 'https://api.example.com';

export default function () {
  // Infrastructure health
  group('Infrastructure Health', function () {
    const healthRes = http.get(`${BASE_URL}/health`, {
      tags: { check: 'infrastructure' },
    });
    
    const healthy = check(healthRes, {
      'infrastructure healthy': (r) => r.status === 200 && r.json('status') === 'healthy',
    });
    
    availability.add(healthy);
    healthChecks.add(1, { component: 'infrastructure' });
  });
  
  sleep(1);
  
  // API endpoints
  group('API Endpoints', function () {
    const endpoints = [
      { path: '/api/users', critical: true },
      { path: '/api/products', critical: true },
      { path: '/api/orders', critical: false },
    ];
    
    for (const endpoint of endpoints) {
      const start = Date.now();
      const res = http.get(`${BASE_URL}${endpoint.path}`, {
        tags: { 
          check: endpoint.critical ? 'critical' : 'standard',
          endpoint: endpoint.path,
        },
      });
      const duration = Date.now() - start;
      
      const success = check(res, {
        [`${endpoint.path} available`]: (r) => r.status === 200,
      });
      
      availability.add(success, { endpoint: endpoint.path });
      responseTime.add(duration, { endpoint: endpoint.path });
      healthChecks.add(1, { component: 'api', endpoint: endpoint.path });
      
      sleep(0.5);
    }
  });
  
  sleep(2);
  
  // Critical user flow
  group('Critical User Flow', function () {
    const loginRes = http.post(`${BASE_URL}/auth/login`,
      JSON.stringify({ username: '[email protected]', password: 'secret' }),
      { 
        headers: { 'Content-Type': 'application/json' },
        tags: { check: 'critical', flow: 'authentication' },
      }
    );
    
    const authenticated = check(loginRes, {
      'login successful': (r) => r.status === 200,
      'token received': (r) => r.json('token') !== undefined,
    });
    
    availability.add(authenticated, { flow: 'authentication' });
    healthChecks.add(1, { component: 'auth' });
  });
  
  sleep(1);
}

export function handleSummary(data) {
  return {
    'stdout': textSummary(data, { indent: ' ', enableColors: true }),
    'summary.json': JSON.stringify(data),
  };
}

This monitoring setup provides comprehensive coverage of infrastructure, APIs, and critical user flows with detailed metrics and alerting.

Next Steps

Learn about test automation for comprehensive CI/CD integration
Explore Grafana Cloud Synthetic Monitoring for managed monitoring
Set up alerting in Grafana for proactive notifications
Review k6 metrics for detailed performance tracking

Using k6

Testing Guides

Browser Testing

Results & Visualization

Performance Monitoring

Synthetic Monitoring Overview

Validate Availability

Monitor Performance

Detect Regressions

Test Critical Flows

Creating Synthetic Tests

Basic Health Check

API Endpoint Monitoring

Critical User Journey

Using Grafana Cloud Synthetic Monitoring

Example Synthetic Monitoring Script

Scheduling Synthetic Tests

Monitoring Best Practices

Use Minimal Load

Set Realistic Thresholds

Tag for Better Analysis

Monitor Multiple Regions

Alerting Strategies

Threshold-Based Alerts

Consecutive Failure Alerts

Visualization and Analysis

Grafana Dashboard Example

Prometheus Queries

Complete Monitoring Setup

Next Steps

Build docs developers (and LLMs) love

Using k6

Testing Guides

Browser Testing

Results & Visualization

​Synthetic Monitoring Overview

Validate Availability

Monitor Performance

Detect Regressions

Test Critical Flows

​Creating Synthetic Tests

​Basic Health Check

​API Endpoint Monitoring

​Critical User Journey

​Using Grafana Cloud Synthetic Monitoring

​Example Synthetic Monitoring Script

​Scheduling Synthetic Tests

​Monitoring Best Practices

​Use Minimal Load

​Set Realistic Thresholds

​Tag for Better Analysis

​Monitor Multiple Regions

​Alerting Strategies

​Threshold-Based Alerts

​Consecutive Failure Alerts

​Visualization and Analysis

​Grafana Dashboard Example

​Prometheus Queries

​Complete Monitoring Setup

​Next Steps

Build docs developers (and LLMs) love

Synthetic Monitoring Overview

Creating Synthetic Tests

Basic Health Check

API Endpoint Monitoring

Critical User Journey

Using Grafana Cloud Synthetic Monitoring

Example Synthetic Monitoring Script

Scheduling Synthetic Tests

Monitoring Best Practices

Use Minimal Load

Set Realistic Thresholds

Tag for Better Analysis

Monitor Multiple Regions

Alerting Strategies

Threshold-Based Alerts

Consecutive Failure Alerts

Visualization and Analysis

Grafana Dashboard Example

Prometheus Queries

Complete Monitoring Setup

Next Steps