RedissonRateLimiter discards permits returned by release() when it recalculates the currently available permits #7342

import org.redisson.Redisson;
import org.redisson.api.RedissonClient;
import org.redisson.config.Config;

public class RedissonConfig {

    public static final RedissonClient REDISSON = new RedissonConfig().create();

    private RedissonClient create() {
        Config config = new Config();
        config.useSingleServer().setAddress("redis://127.0.0.1:6379");
        return Redisson.create(config);
    }
}

public class SimulationConfig {

    public static final int RATE = 10;

    public static final int INTERVAL_MS = 1000;

    /** Interval between permit consumption and release (ms) */
    public static final int RELEASE_DELAY_MS = 100;

    /** Total execution time (sec) */
    public static final int DURATION_SEC = 30;

    private SimulationConfig() {}
}

public class Simulator {

    public void run() throws InterruptedException {
        RateLimiterConfig config = new RateLimiterConfig();
        RRateLimiter limiter = config.create();

        long startNano = System.nanoTime();
        long endAt = System.nanoTime() + SimulationConfig.DURATION_SEC * 1_000_000_000L;

        List<long[]> samples = new ArrayList<>();

        while (System.nanoTime() < endAt) {
            limiter.tryAcquire(1);
            Thread.sleep(SimulationConfig.RELEASE_DELAY_MS);
            limiter.release(1);
            long permits = getPermit();
            long tMs = (System.nanoTime() - startNano) / 1_000_000;
            long history = config.historySize();
            samples.add(new long[]{tMs, permits, history});
            Thread.sleep(10);
        }

        writeJson(samples);
    }

    private long getPermit() {
        String valueKey = RateLimiterConfig.valueKey();
        RedissonClient redisson = RedissonConfig.REDISSON;
        RBucket<Long> value = redisson.getBucket(valueKey, LongCodec.INSTANCE);
        return value.get();
    }
}

+ "if released > 0 then "
    + "redis.call('zremrangebyscore', permitsName, 0, tonumber(ARGV[2]) - interval); "
    + "if tonumber(currentValue) + released > tonumber(rate) then "
        + "local values = redis.call('zrange', permitsName, 0, -1); "
        + "local used = 0; "
        + "for i, v in ipairs(values) do "
            + "local random, permits = struct.unpack('Bc0I', v);"
            + "used = used + permits;"
        + "end; "
        // currentValue is recalculated here
        + "currentValue = tonumber(rate) - used; "
    + "else "
        + "currentValue = tonumber(currentValue) + released; "
    + "end; "
    + "redis.call('set', valueName, currentValue);"
+ "end;"

+ "if released > 0 then "
    + "redis.call('zremrangebyscore', permitsName, 0, tonumber(ARGV[2]) - interval); "
    + "if tonumber(currentValue) + released > tonumber(rate) then "
        + "local values = redis.call('zrange', permitsName, 0, -1); "
        + "local used = 0; "
        + "for i, v in ipairs(values) do "
            + "local random, permits = struct.unpack('Bc0I', v);"
            + "used = used + permits;"
        + "end; "
        // changed here
        + "if used + tonumber(currentValue) <= tonumber(rate) then "
            + "currentValue = tonumber(rate) - used; "
        + "end; "
    + "else "
        + "currentValue = tonumber(currentValue) + released; "
    + "end; "
    + "redis.call('set', valueName, currentValue);"
+ "end;"