NodeJs: Rate Limiter

The task is to implement a custom rate limiter middleware that limits the number of API requests allowed from a client within a specified time window. You are given a RateLimiterMiddleware class which implements the custom rate limiter middleware. Complete the middleware method which returns a middleware function that limits the number of requests from each client IP address based on the provided options: rateLimiterOptions. Also, complete the rateLimiterOptions which should define the maximum requests limit and a specified time window.

RateLimiterMiddleware

• The constructor accepts an options object with the properties maxRequests and timeWindow.

  • Initializes an empty Map instance as rateLimitStore to store the client IP addresses and their corresponding request data.

• middleware method should:

  • Keep track of the request count and the timestamp of the first request for each client IP address.

  • Limit the number of requests based on the provided maxRequests and timeWindow options.

  • Retrieves the client's IP address from the request.

  • Retrieve the client's request data from rateLimitStore or initialize a new request data object with requestCount set to 0 and firstRequestTime set to the current timestamp.

  • If the client has exceeded the rate limit:

    • Reset the X-RateLimit-Remaining header to 0
    • Return a 429 status code and a JSON message "You have exceeded the rate limit. Please try again later."

  • If the client has not exceeded the rate limit:

    • Increment the requestCount by 1
    • Update the client's request data in the rateLimitStore
    • If the difference between the current timestamp and firstRequestTime is greater than or equal to timeWindow, reset the requestCount to 1 and update firstRequestTime to the current timestamp.
    • Set the X-RateLimit-Remaining header to the difference between maxRequests and the updated requestCount.

  • Include the following headers in the responses:

    • X-RateLimit-Limit: The maximum number of requests allowed within the time window.
      • Set the X-RateLimit-Limit header to the maxRequests value.
    • X-RateLimit-Remaining: The number of requests remaining within the current time window.
      • Set the X-RateLimit-Reset header to the sum of firstRequestTime and timeWindow.
    • X-RateLimit-Reset: The timestamp when the rate limit will be reset.
      • Set the X-RateLimit-Remaining header to the difference between maxRequests and the updated requestCount

• reset():

  • Clears the rateLimitStore by calling its clear() method, effectively resetting the rate limit data for all clients.

options.js

• Define an object rateLimiterOptions with the properties maxRequests and timeWindow.
  • The maxRequests property should be a number representing the maximum number of requests allowed within the time window.
  • Set maxRequests to be 5
  • The timeWindow property should be a number representing the time window duration (in milliseconds) to limit requests within.
  • Set timeWindow to be 1000 (1 second).

Read Only Files

• test/*.spec.js

Environment

• Node Version: v14(LTS)
• Default Port: 8000

Commands

• run:

npm start

• install:

npm install

• test:

npm test