Building an Advanced API Gateway in Node.js, A Step-by-Step Guide with Examples of Rate Limiting and Statistics

First, set up your Node.js project with the Express framework and create a basic API endpoint for handling incoming requests.

const express = require('express');
const app = express();

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

app.listen(3000, () => {
  console.log('Server running on port 3000');
});

Implement rate limiting by using a middleware function that checks the number of requests made by a specific IP address within a certain timeframe. You can use a package like express-rate-limit to handle this.

const rateLimit = require('express-rate-limit');

const limiter = rateLimit({
  windowMs: 15 * 60 * 1000, // 15 minutes
  max: 100, // limit each IP to 100 requests per windowMs
  message: 'Too many requests, please try again later'
});

// apply the limiter to all requests
app.use(limiter);

Collect statistics on your API's usage by using a middleware function that logs the request method, endpoint, and response status code for each incoming request. You can use a package like morgan to handle this.

const morgan = require('morgan');

app.use(morgan('combined'));

To keep track of all the statistics and also to show the statistics to the client, you can use a package like winston to log all the statistics, which can be saved to a file or a database.

const winston = require('winston');

const logger = winston.createLogger({
  transports: [
    new winston.transports.File({
      filename: './logs/api.log',
      level: 'info'
    }),
    new winston.transports.Console({
      level: 'debug'
    })
  ]
});

app.use(morgan('combined', { stream: { write: (message) => logger.info(message) } }));

To display the statistics, you can create an endpoint that retrieves the statistics from the file or the database and returns them in a JSON format.

app.get('/stats', (req, res) => {
  // read statistics from file or database
  const stats = {
    requests: 1000,
    success: 800,
    errors: 200
  };

  res.json(stats);
});

You now have an advanced API gateway that implements rate limiting, collects statistics, and allows clients to view these statistics.