JMeter & Locust

Understand JMeter test plans and Locust Python scripts for HTTP load testing.

JMeter Overview

Apache JMeter is the industry-standard Java-based load testing tool. Used widely in enterprise environments. GUI for test design, CLI for CI execution.

# Install
brew install jmeter             # macOS
# Or: download from jmeter.apache.org

# GUI mode (test design)
jmeter

# CLI mode (CI execution — headless)
jmeter -n -t test-plan.jmx -l results.jtl -e -o report/

JMeter Test Plan Structure

Test Plan
├── Thread Group (users × ramp-up × duration)
│   ├── HTTP Request Defaults (base URL)
│   ├── HTTP Cookie Manager
│   ├── CSV Data Set Config (test data from file)
│   ├── HTTP Request (GET /api/bookings)
│   ├── HTTP Request (POST /api/login)
│   ├── Response Assertion (status = 200)
│   ├── Duration Assertion (< 500ms)
│   └── View Results Tree (debug — remove in CI)
└── Listeners (results, graphs — use CLI flags in CI)

JMeter Thread Group Configuration

<!-- thread-group.jmx excerpt -->
<ThreadGroup>
  <stringProp name="ThreadGroup.num_threads">100</stringProp>  <!-- users -->
  <stringProp name="ThreadGroup.ramp_time">60</stringProp>     <!-- ramp seconds -->
  <stringProp name="ThreadGroup.duration">300</stringProp>     <!-- test duration -->
  <stringProp name="ThreadGroup.scheduler">true</stringProp>   <!-- use duration -->
</ThreadGroup>

JMeter in CI

# Run in headless mode + generate HTML report
jmeter -n \
  -t tests/booking-load.jmx \
  -l results/results.jtl \
  -e -o results/html-report/ \
  -Jbase_url=https://staging.example.com \
  -Jusers=50 \
  -Jramp=30

# Check pass/fail by error rate (no built-in threshold like k6)
# Parse results.jtl and fail CI if error rate > 1%
python3 scripts/check-jmeter-results.py results/results.jtl

JMeter with Jenkins

// Jenkinsfile
stage('Performance') {
  steps {
    sh 'jmeter -n -t tests/load.jmx -l results.jtl -e -o html-report/'
    perfReport sourceDataFiles: 'results.jtl'  // Performance Plugin
    publishHTML(target: [reportDir: 'html-report', reportFiles: 'index.html'])
  }
}

Locust Overview

Locust is a Python-based load testing tool. Tests are pure Python — no XML, no GUI required. Easy to extend with custom behaviour.

# Install
pip install locust

# Run headless
locust -f locustfile.py --headless -u 100 -r 10 -t 2m --host https://staging.example.com

# Run with web UI
locust -f locustfile.py --host https://staging.example.com

Locust Test File

# locustfile.py
from locust import HttpUser, task, between

class BookingUser(HttpUser):
    wait_time = between(1, 3)  # think time: 1-3 seconds between tasks
    token = None

    def on_start(self):
        # Authenticate before running tasks
        res = self.client.post('/auth', json={
            'username': 'admin',
            'password': 'password123',
        })
        self.token = res.json()['token']

    @task(3)       # weight: called 3× more than @task(1)
    def list_bookings(self):
        self.client.get('/booking', name='GET /booking')

    @task(1)
    def get_booking(self):
        self.client.get('/booking/1', name='GET /booking/:id')

    @task(1)
    def create_booking(self):
        self.client.post('/booking', json={
            'firstname': 'Load',
            'lastname': 'Test',
            'totalprice': 100,
            'depositpaid': True,
            'bookingdates': {'checkin': '2025-01-01', 'checkout': '2025-01-02'},
        }, name='POST /booking')

Locust in CI

# Headless with exit code on failure
locust -f locustfile.py \
  --headless \
  --users 100 \
  --spawn-rate 10 \
  --run-time 2m \
  --host $BASE_URL \
  --html locust-report.html \
  --csv locust-results \
  --exit-code-on-error 1

JMeter vs Locust vs k6