Distributed Load Testing with Locust & Docker

Overview

This guide walks you through setting up and running Locust in a distributed master-worker architecture using Docker.

When testing high-throughput APIs or simulating massive user traffic, a single machine often becomes the bottleneck. Distributed load testing solves this by splitting the workload. In this setup, a single Master node coordinates the test execution and aggregates real-time metrics, while multiple Worker nodes simulate concurrent users and execute the actual API requests.

Architecture

┌─────────────────────────────────────────┐
│       Locust Master (Web UI)            │
│       ├─ Coordinates test execution     │
│       ├─ Aggregates metrics             │
│       └─ Provides web dashboard (8089)  │
└────────────┬────────────────────────────┘
             │
    ┌────────┼────────┐
    │        │        │
┌───▼───┐┌───▼───┐┌───▼───┐
│Worker ││Worker ││Worker │ (Multiple containers)
│  1-5  ││ 6-10  ││  ...  │ Each with concurrent users
└───────┘└───────┘└───────┘