load-shedder

load-shedder

⚡️ Framework-agnostic load shedding middleware for Node.js servers

load-shedder is a lightweight middleware that protects your Node.js app from overload by shedding traffic under high load conditions.

It works with any HTTP framework (Express, Koa, Fastify, or native http.createServer) and uses key system signals like event loop delay, memory usage, and active request count to make real-time shedding decisions.

🚀 Features

• ✅ Framework agnostic – works with Express, Koa, Fastify, or native HTTP
• ⚙️ Configurable thresholds (event loop lag, memory, concurrency)
• 🚫 Graceful traffic rejection (custom 503/429 responses)
• 🧠 Adaptive: shed only when needed, exempt important routes
• 📊 Optional metrics & logging support
• 🔌 Extensible: hook into your own system pressure indicators

📦 Installation

npm install load-shedder
# or
yarn add load-shedder

🛠 Usage

With Express

import express from 'express';
import { createShedder } from 'load-shedder';

const app = express();

const shedder = createShedder({
  maxEventLoopDelay: 100, // ms
  maxConcurrentRequests: 100,
  maxMemoryUsage: 0.8, // 80% heap
});

app.use(shedder.expressMiddleware());

app.get('/', (req, res) => {
  res.send('All good!');
});

app.listen(3000);

With Native HTTP

import http from 'http';
import { createShedder } from 'load-shedder';

const shedder = createShedder({ maxEventLoopDelay: 120 });

const server = http.createServer((req, res) => {
  if (shedder.shouldShed(req)) {
    shedder.handleShed(req, res);
    return;
  }

  res.writeHead(200);
  res.end('OK');
});

server.listen(3000);

⚙️ API

createShedder(options)