RateLimiting Comparision

RateLimiting Comparision

Why Custom Rate-limiter?

A. Usecase: Per second rate-limiting not satisfied by Guava-RateLimiter
(1) Guava RateLimiter: For X permits: it releases X/1000 permits every msec. therefore, for permits=2/sec => 
it release 1st permit on first 500msec and 2nd permit on next 500ms. therfore, if 2 request comes with in 500msec duration then 
2nd request fails to acquire permit though we have configured 2 permits/second.
https://github.com/google/guava/blob/v15.0/guava/src/com/google/common/util/concurrent/RateLimiter.java#L102
(2) Custon RateLimiter: it releases X permits every second. so, in above usecase: if 2 requests comes at the same time then both will 
acquire the permit.

B. Custom-RateLimiter is light-weight and faster than Guava-RateLimiter


    @Test
    public void compareRateLimiter() {
        final int permitsPerSecond = 1000;
        com.google.common.util.concurrent.RateLimiter guavaRateLimiter = com.google.common.util.concurrent.RateLimiter
                .create(permitsPerSecond);
        org.apache.pulsar.common.util.RateLimiter rateLimiter = new org.apache.pulsar.common.util.RateLimiter(
                permitsPerSecond, 1, TimeUnit.SECONDS);
        Assert.assertTrue(rateLimiter.tryAcquire());
        Assert.assertTrue(guavaRateLimiter.tryAcquire());

        final int totalRound = 50;
        long totalGavaRateLimiterTime = 0;
        long totalCustomRateLimiterTime = 0;
        for (int i = 0; i < totalRound; i++) {
            long time = runGuavaRateLimiter(guavaRateLimiter, permitsPerSecond);
            System.out.println("Guava rate-limiter = " + time);
            totalGavaRateLimiterTime+=time;
        }
        System.out.println("*****************************");
        for (int i = 0; i < totalRound; i++) {
            long time = runCustomRateLimiter(rateLimiter, permitsPerSecond);
            System.out.println("Custom rate-limiter= " + time);
            totalCustomRateLimiterTime+=time;
        }
        System.out.println("*****************************");
        System.out.println("Avg-Guava ="+(totalGavaRateLimiterTime/totalRound));
        System.out.println("Avg-Custom="+(totalCustomRateLimiterTime/totalRound));

    }

    private long runCustomRateLimiter(org.apache.pulsar.common.util.RateLimiter rateLimiter,
            int permitsPerSecond) {
        long start = System.nanoTime();
        for (int i = 0; i < permitsPerSecond; i++) {
            rateLimiter.tryAcquire();
        }
        return System.nanoTime() - start;
    }

    private long runGuavaRateLimiter(com.google.common.util.concurrent.RateLimiter rateLimiter,
            int permitsPerSecond) {
        long start = System.nanoTime();
        for (int i = 0; i < permitsPerSecond; i++) {
            rateLimiter.tryAcquire();
        }
        return System.nanoTime() - start;
    }
       
    
Output:

Guava rate-limiter = 816142
Guava rate-limiter = 390226
Guava rate-limiter = 181257
Guava rate-limiter = 203298
Guava rate-limiter = 135213
Guava rate-limiter = 117949
Guava rate-limiter = 151119
Guava rate-limiter = 155849
Guava rate-limiter = 136992
Guava rate-limiter = 255227
Guava rate-limiter = 159248
Guava rate-limiter = 148158
Guava rate-limiter = 180691
Guava rate-limiter = 135304
Guava rate-limiter = 147782
Guava rate-limiter = 138417
Guava rate-limiter = 121818
Guava rate-limiter = 115644
Guava rate-limiter = 104803
Guava rate-limiter = 155415
Guava rate-limiter = 156300
Guava rate-limiter = 138936
Guava rate-limiter = 116146
Guava rate-limiter = 103286
Guava rate-limiter = 110809
Guava rate-limiter = 74366
Guava rate-limiter = 70510
Guava rate-limiter = 79539
Guava rate-limiter = 77491
Guava rate-limiter = 76157
Guava rate-limiter = 111347
Guava rate-limiter = 69286
Guava rate-limiter = 67669
Guava rate-limiter = 71077
Guava rate-limiter = 74837
Guava rate-limiter = 67403
Guava rate-limiter = 67240
Guava rate-limiter = 67441
Guava rate-limiter = 74310
Guava rate-limiter = 125629
Guava rate-limiter = 89536
Guava rate-limiter = 99363
Guava rate-limiter = 93774
Guava rate-limiter = 126160
Guava rate-limiter = 101278
Guava rate-limiter = 93005
Guava rate-limiter = 71114
Guava rate-limiter = 92420
Guava rate-limiter = 71865
Guava rate-limiter = 68615
*****************************
Custom rate-limiter= 432327
Custom rate-limiter= 213219
Custom rate-limiter= 246625
Custom rate-limiter= 74359
Custom rate-limiter= 66935
Custom rate-limiter= 79609
Custom rate-limiter= 76600
Custom rate-limiter= 84380
Custom rate-limiter= 98325
Custom rate-limiter= 91005
Custom rate-limiter= 106330
Custom rate-limiter= 89921
Custom rate-limiter= 83557
Custom rate-limiter= 146340
Custom rate-limiter= 90749
Custom rate-limiter= 97285
Custom rate-limiter= 89704
Custom rate-limiter= 92439
Custom rate-limiter= 90426
Custom rate-limiter= 90035
Custom rate-limiter= 91065
Custom rate-limiter= 92197
Custom rate-limiter= 76730
Custom rate-limiter= 49499
Custom rate-limiter= 46078
Custom rate-limiter= 44608
Custom rate-limiter= 43051
Custom rate-limiter= 43037
Custom rate-limiter= 52295
Custom rate-limiter= 33088
Custom rate-limiter= 144337
Custom rate-limiter= 50498
Custom rate-limiter= 57400
Custom rate-limiter= 47586
Custom rate-limiter= 47072
Custom rate-limiter= 47211
Custom rate-limiter= 46658
Custom rate-limiter= 45878
Custom rate-limiter= 46090
Custom rate-limiter= 56782
Custom rate-limiter= 48696
Custom rate-limiter= 45281
Custom rate-limiter= 44289
Custom rate-limiter= 39502
Custom rate-limiter= 45452
Custom rate-limiter= 43763
Custom rate-limiter= 88435
Custom rate-limiter= 45413
Custom rate-limiter= 47739
Custom rate-limiter= 47027
*****************************
Avg-Guava =133149
Avg-Custom=81938