RateLimiter: changeLimitForPeriod does not work

[rvit34]

Resilience4j version: 1.5.0

Java version: 1.8

This test reproduces the issue:

    @Test
    public void changeLimitForPeriodTest() {
        // create limiter with rate 10 rps
        final RateLimiterConfig config = RateLimiterConfig.custom()
                .limitRefreshPeriod(Duration.ofSeconds(1))
                .limitForPeriod(10)
                .timeoutDuration(Duration.ofMillis(0))
                .build();

        final RateLimiterRegistry registry = RateLimiterRegistry.of(config);
        final RateLimiter limiter = registry.rateLimiter("test");

        long t1 = System.currentTimeMillis();
        Assert.assertTrue(limiter.acquirePermission());
        Assert.assertTrue(limiter.acquirePermission());
        Assert.assertTrue(limiter.acquirePermission());

        // change limit up to 5 rps
        limiter.changeLimitForPeriod(5);

        Assert.assertTrue(limiter.acquirePermission()); 
        Assert.assertTrue(limiter.acquirePermission());
        Assert.assertTrue(limiter.acquirePermission()); // should be false?
        Assert.assertTrue(limiter.acquirePermission());
        Assert.assertTrue(limiter.acquirePermission());

        long t2 = System.currentTimeMillis();
        System.out.println("time spent(millis): " + (t2-t1));
        Assert.assertFalse(limiter.acquirePermission()); // fails here
    }

[storozhukBM]

Hi @rvit34 Thank you for listing this case for us, but I'm afraid this is expected behaviour. The documentation for changeLimitForPeriod method provides an explanation: NOTE! New limit won't affect current period permissions and will apply only from next one.

    /**
     * Dynamic rate limiter configuration change. This method allows to change count of permissions
     * available during refresh period. NOTE! New limit won't affect current period permissions and
     * will apply only from next one.
     *
     * @param limitForPeriod new permissions limit
     */
    void changeLimitForPeriod(int limitForPeriod);

[rvit34]

It would be useful, especially in tests, to don't wait for the next period. Is it possible to add optional argument to the method to apply new limit immediately?

[storozhukBM]

@rvit34 I agree, this would be a convenient feature. Would you like to create PR?