Sliding Window Counter Approximate

Parameters

• Parameters: maxRequests, windowSize.

Description

• Utilizes current and previous window counts with a weighting system based on time elapsed in the current window.
• Offers a balance between accuracy and efficiency, smoothing out traffic spikes with minimal memory usage.
• Suitable for use cases where an exact count is less critical.

Example: windowSize = 1 min, requestLimit = 7

• T0 (01:00:00): Window starts, 0 requests counted.
• T1 (01:01:10): Previous window had 5 requests, current window has 2.
• T2 (01:01:15): New request evaluated with weighted count: 2 (current) + 5 * 0.75 (previous weighted) = 5.75, rounded down to 5, request allowed.
• T3 (01:02:00): Window resets, counting starts afresh for the new minute.

How to use

When creating your API, you can use the RateLimitFactory to create a leaking bucket rate limit.

Api.create(8080)
      .rateLimit(RateLimitFactory.customSlidingWindowCounterApproximate(4, Duration.ofSeconds(1)))
      .addRoute(Route.builder("/"),
      .path(RouteMethod.GET, "/", controller::handler))
      .start();
          

Factory

The RateLimitFactory provides a default and a custom method for this rate limiter.

• For more details on the check the source code of the RateLimitFactory

See more in our blog post about Rate Limiters