Loadly ⚡

Modern, lightweight API load testing with a local React UI. Install globally, run a single command, configure endpoints in the browser, and watch live analytics stream in.

• Install: npm i -g loadly (or npm i -g @sudoDevesh/loadly if using a scoped name)
• Run: loadly run
• UI: http://localhost:3000 (auto-opens)
• Requires: Node.js 18+

📽️ Demo Video

Why Loadly?

Most load-testing tools force a choice:

• Powerful but config-heavy scripts and CLIs
• Or pretty UIs that are slow to set up and hard to automate

Loadly blends both:

• Single command startup
• Zero config to get going
• Intuitive UI for defining scenarios
• Real-time metrics without cloud accounts or agents
• 100% local: data never leaves the machine

Think “Postman + k6, but simpler, prettier, and developer-friendly.” Define endpoints and headers like in Postman; hit Run and get live charts and percentiles like k6—without a learning curve.

What You Get

• One command to launch: loadly run
• Local web UI for configuration and dashboards
• Multiple endpoints per test with weights and JSON bodies
• Simple templating: {{uuid}}, {{timestamp}}, {{randint:min,max}}
• Live metrics: RPS, success/failure, p95 latency, memory usage, status code breakdown
• Final JSON summary for copy/paste or export
• Runs entirely on the local machine (no external services)

Target Audience

• Solo devs / indie hackers who want quick API load tests
• Startups / small teams who don’t want to set up JMeter/k6
• Open-source developers who value a simple, pretty, developer-first tool

Quick Start

1. Install (Node 18+)

• npm i -g loadly

2. Run

• loadly run

3. Configure in UI

• Concurrency: number of virtual users (e.g., 20)
• Duration: seconds to run (e.g., 30)
• Headers (JSON): e.g., { "Content-Type": "application/json" }
• Endpoints (JSON array), example: [ { "url": "https://httpbin.org/get", "method": "GET", "weight": 2 }, { "url": "https://httpbin.org/post", "method": "POST", "body": { "id": "{{uuid}}", "ts": "{{timestamp}}" } } ]

4. Click “Start Testing” and watch live metrics. A final summary appears when complete.

Tip: Test a local API at http://localhost:4000 and mix fast, slow, flaky, and 404 endpoints to exercise the dashboard.

How Loadly Calculates “How Many Requests?”

Loadly is time-bound, not count-bound:

• Concurrency sets parallel workers
• Duration sets how long they run
• Throughput emerges from endpoint latency, failures, and network conditions

Total requests ≈ throughput (RPS) × duration. Increase concurrency for more pressure; increase duration for steadier percentile estimates.

Feature Highlights

• Multiple endpoints with weights

• JSON bodies + templating:

  • {{uuid}} — random UUID per request
  • {{timestamp}} — epoch ms at send time
  • {{randint:a,b}} — integer within [a, b]

• Live dashboard:

  • Total, Success, Failures
  • RPS (requests per second)
  • Avg and p95 latency (ms)
  • Memory (RSS/Heap)
  • Status code distribution

• Abort on UI close (tests stop when the tab/socket closes)

• Final JSON summary for logs or export

Architecture Overview

• CLI: launches a local server and opens the browser
• Backend: Express + WebSocket for control and telemetry
• Engine: Node-based HTTP runner with templating and weighted endpoint selection
• Frontend: React app served statically; connects via WebSocket for live updates

Everything is self-contained and local—no databases or external services.

Developer Ergonomics

• One-command start, zero boilerplate
• JSON-based configuration with live feedback
• Clear error messages on invalid input
• Works with any HTTP API—REST, JSON-RPC, GraphQL over HTTP, internal services
• Port override: set PORT=8080 loadly run

Install and Run

• Global install:

  • npm i -g loadly

• Launch:

  • loadly run

• Custom port:

  • PORT=8080 loadly run

• Health check:

  • http://localhost:3000/health → { "ok": true }

Requires Node.js 18+.

Troubleshooting

• “Cannot GET /”

  • Build artifacts missing: ensure the UI is being served from ui/dist. If developing from source, rebuild the UI.

• WebSocket not updating

  • Ensure the CLI is running and the UI is opened from the same host/port (localhost:3000). If using a separate UI dev server, point WS to the backend port or open the built UI.

• fetch is not defined

  • Requires Node 18+ (engine uses global fetch).

Contributing

• Fork the repo and clone locally

• Install root and UI dependencies, then build the UI

• Start in dev:

  • npm run dev

• UI live dev:

  • cd ui && npm run dev (Vite @ 5173)

Please open issues for bugs, feature requests, or ideas. PRs welcome.

License

MIT

Philosophy

• Minimal setup, maximal feedback
• Local-first by default (privacy-friendly)
• Human-friendly UI with developer-focused power
• Designed to scale with the developer’s needs—from a smoke test to iterative performance tuning

Loadly replaces “spin up a toolchain” friction with a simple flow: run a command, paste endpoints, click Run, and learn fast.