rate limiter

Enterprise ready rate limiter.

Some implementations:

• rate-limiter-annotation.

• rate-limiter-web-core.

• rate-limiter-spring.

• rate-limiter-javaee.

To add a dependency on rate-limiter using Maven, use the following:

        <dependency>
            <groupId>io.github.poshjosh</groupId>
            <artifactId>rate-limiter</artifactId>
            <version>0.8.0</version>
        </dependency>

RateLimiter

RateLimiter rateLimiter = RateLimiter.of(Bandwidths.ofSeconds(1));

Usage

We want rate limiting to be adjusted dynamically based on specific conditions. See rate condition expression language

import io.github.poshjosh.ratelimiter.RateLimiter;
import io.github.poshjosh.ratelimiter.bandwidths.Bandwidths;
import io.github.poshjosh.ratelimiter.matcher.Matcher;
import io.github.poshjosh.ratelimiter.matcher.Matchers;

class DynamicRateLimiting {

    static RateLimiter rateLimiter = RateLimiter.of(Bandwidths.ofSeconds(1));

    static Matcher matchAfter2Seconds = Matchers.ofExpression("sys.time.elapsed > PT2S");

    public static void main(String[] args) throws Exception {

        final long startTime = System.currentTimeMillis();

        for (int i = 0; i < 5; i++) {

            final boolean matches = matchAfter2Seconds.matches(startTime);
            System.out.println("Matches: " + matchesCondition + ", elapsed time: " + elapsedTime);

            if (matchesCondition) {
                final boolean acquired = rateLimiter.tryAcquire(1);
                System.out.println("Within limit: " + acquired);
            }

            Thread.sleep(500);
        }
    }
}

// Output
//        Matches: false, elapsed time: 0
//        Matches: false, elapsed time: 504
//        Matches: true, elapsed time: 1004
//        Within limit: true
//        Matches: true, elapsed time: 1505
//        Within limit: true
//        Matches: true, elapsed time: 2008
//        Within limit: false

We have a flexible expression language for example:

jvm.memory.available < 500MB && sys.time.elapsed > PT1S

We have a list of tasks to execute, but we don't want to submit more than 2 per second.

class Throttling {
  final RateLimiter rateLimiter = RateLimiter.of(Bandwidths.bursty(2.0)); // 2 permits per second
  void submitTasks(List<Runnable> tasks, Executor executor) {
    for (Runnable task : tasks) {
      rateLimiter.acquire(); // may wait
      executor.execute(task);
    }
  }
}

We produce a stream of data, and we want to cap it at 5kb per second. This could be accomplished by requiring a permit per byte, and specifying a rate of 5000 permits per second.

class DataCap {
  final RateLimiter rateLimiter = RateLimiter.of(Bandwidths.bursty(5000.0)); // 5000 permits per second
  void submitPacket(byte[] packet) {
    rateLimiter.acquire(packet.length);
    networkService.send(packet);
  }
}

Performance

Performance statistics

Build

This is a maven based java project, so:

To package a jar file

mvn clean package

To install, thus making it referencable in other project's pom.xm

mvn clean install

Enjoy! 😉

Dependents

The following depend on this library:

• rate-limiter-annotation.

• rate-limiter-web-core.

• rate-limiter-spring.

• rate-limiter-javaee.