com.tomtom.speedtools.ratelimiter

Class RateLimiter

java.lang.Object

com.tomtom.speedtools.ratelimiter.RateLimiter

Direct Known Subclasses:

ThreadSafeRateLimiter

public class RateLimiter
extends Object

This class is used to rate limit writes to, say, MongoDB reads/writes. It's handy if the calling code can do bulk write operations through the limiter, which rate-limits how fast they happen. Note you can disable the rate limiter by setting the frequency to 0. The math is as follows (mod some conversions between seconds and nano-seconds):

  After n samples, we can computer Ri as the "immediate rate" like:
      Ri = (n-1) / (timestamp - timestamp(0))
  which is essentially the 1/average interval.

  Given a target rate, Rt ("maxFreqHz"), we can compute it like:
      Rt = n / (S + (timestamp - timestamp(0))

  S here is how long to sleep before we invoke the next operation.  Solving for S:
      S = n / Rt - (timestamp - timestamp(0))
 

Original author of Scala version: Eric Bowman (2012-05-16) Rewritten to Java by: Rijn Buve (2012-07-24).

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	RateLimiter.WorkFunction Interface for worker function, passed as an argument to limit() function below.

Constructor Summary

Constructors

Constructor and Description
RateLimiter(int maxFreqHz)
RateLimiter(int maxFreqHz, int burstFreqHz) Create a rate limiter that will limit calls to 'maxFreqHz' in bursts which occur approximately every 'burstFreqHz'.

Method Summary

Modifier and Type	Method and Description
void	limit(RateLimiter.WorkFunction workFunction) Limit the execution of a work function to the frequency set in this limiter.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

RateLimiter

public RateLimiter(int maxFreqHz,
                   int burstFreqHz)

Create a rate limiter that will limit calls to 'maxFreqHz' in bursts which occur approximately every 'burstFreqHz'. For example, if maxFreqHz = 100 and burstFreqHz = 2, the limiter will allow no more than 100 calls per second, but will burst them into 2 batches of 50 calls each, per second. For a more evenly distributed burst pattern, increase burstFreqHz. It's best to keep burstFreqHz reasonably low, say below 100. Note that the implementation of the limiter does not guarantee that the frequency is reached (or that calls may have been scheduled slightly faster than the frequency, even). On average, it does a pretty good job though.

Parameters:

maxFreqHz - Max. frequency.

burstFreqHz - Burts frequency.

RateLimiter

public RateLimiter(int maxFreqHz)

Method Detail

limit

public void limit(RateLimiter.WorkFunction workFunction)

Limit the execution of a work function to the frequency set in this limiter.

Parameters:

workFunction - Work function (interface, see below).