Rate represents token bucket parameters.

mkRate creates a Rate given the burst amount, and the number of operations (must be > 0) to allow per number of seconds given.

infRate creates a Rate whose limit can never be exceeded. Useful to never limit an operation.

RateLimitSetings holds settings for the rate limiting middleware.

Create new rate limit settings by providing a function to map a request to a key and a Rate. It sets up a default response for requests that exceed the rate limit that returns a 429 status code with a simple error message.

Set a custom error response.

setResetInterval starts a thread to reset (clear) the token buckets map after every given interval period of time (expressed in seconds). This is useful if your webserver generates a lot of request keys that go idle after some activity. In this situation the token bucket cache memory usage grows as it contains an entry every key seen. When the cache is reset, the memory can be garbage collected. Though this will cause all rate limit token buckets to go "full" (i.e. allow the full burst of requests immediately), this solution is acceptable as this is the case when the webserver is restarted as well. By default, there is no reset thread launched (unless this function is called).

rateLimitMiddleware performs rate limiting according to the given settings.

stopResetThread stops the thread launched by setResetInterval and is provided for completeness. If your application automatically restarts the web-server using the rate limit middleware, call this function in your web server's shutdown handler to ensure that the reset thread is killed (and does not leak).

A cache that maps request keys to a TokenBucket.

tryAllocate attempts to allocate the given amount from the TokenBucket corresponding to the given key and Rate in the Cache. On success it returns Nothing, otherwise it returns the minimum time (in nanoseconds) to wait after which the allocation can succeed.