RateLimiterConfig.java

/*
 *
 *  Copyright 2016 Robert Winkler and Bohdan Storozhuk
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *
 */
package io.github.resilience4j.ratelimiter;

import java.time.Duration;

import static java.util.Objects.requireNonNull;

public class RateLimiterConfig {
    private static final String TIMEOUT_DURATION_MUST_NOT_BE_NULL = "TimeoutDuration must not be null";
    private static final String LIMIT_REFRESH_PERIOD_MUST_NOT_BE_NULL = "LimitRefreshPeriod must not be null";
    private static final Duration ACCEPTABLE_REFRESH_PERIOD = Duration.ofNanos(1L);

    private Duration timeoutDuration =  Duration.ofSeconds(5);
    private Duration limitRefreshPeriod = Duration.ofNanos(500);
    private int limitForPeriod = 50;

    private RateLimiterConfig() {
    }

    /**
     * Returns a builder to create a custom RateLimiterConfig.
     *
     * @return a {@link RateLimiterConfig.Builder}
     */
    public static Builder custom() {
        return new Builder();
    }

    /**
     * Creates a default RateLimiter configuration.
     *
     * @return a default RateLimiter configuration.
     */
    public static RateLimiterConfig ofDefaults(){
        return new Builder().build();
    }

    public Duration getTimeoutDuration() {
        return timeoutDuration;
    }

    public Duration getLimitRefreshPeriod() {
        return limitRefreshPeriod;
    }

    public int getLimitForPeriod() {
        return limitForPeriod;
    }

    @Override public String toString() {
        return "RateLimiterConfig{" +
            "timeoutDuration=" + timeoutDuration +
            ", limitRefreshPeriod=" + limitRefreshPeriod +
            ", limitForPeriod=" + limitForPeriod +
            '}';
    }

    public static class Builder {

        private RateLimiterConfig config = new RateLimiterConfig();

        /**
         * Builds a RateLimiterConfig
         *
         * @return the RateLimiterConfig
         */
        public RateLimiterConfig build() {
            return config;
        }

        /**
         * Configures the default wait for permission duration.
         * Default value is 5 seconds.
         *
         * @param timeoutDuration the default wait for permission duration
         * @return the RateLimiterConfig.Builder
         */
        public Builder timeoutDuration(final Duration timeoutDuration) {
            config.timeoutDuration = checkTimeoutDuration(timeoutDuration);
            return this;
        }

        /**
         * Configures the period of limit refresh.
         * After each period rate limiter sets its permissions
         * count to {@link RateLimiterConfig#limitForPeriod} value.
         * Default value is 500 nanoseconds.
         *
         * @param limitRefreshPeriod the period of limit refresh
         * @return the RateLimiterConfig.Builder
         */
        public Builder limitRefreshPeriod(final Duration limitRefreshPeriod) {
            config.limitRefreshPeriod = checkLimitRefreshPeriod(limitRefreshPeriod);
            return this;
        }

        /**
         * Configures the permissions limit for refresh period.
         * Count of permissions available during one rate limiter period
         * specified by {@link RateLimiterConfig#limitRefreshPeriod} value.
         * Default value is 50.
         *
         * @param limitForPeriod the permissions limit for refresh period
         * @return the RateLimiterConfig.Builder
         */
        public Builder limitForPeriod(final int limitForPeriod) {
            config.limitForPeriod = checkLimitForPeriod(limitForPeriod);
            return this;
        }

    }

    private static Duration checkTimeoutDuration(final Duration timeoutDuration) {
        return requireNonNull(timeoutDuration, TIMEOUT_DURATION_MUST_NOT_BE_NULL);
    }

    private static Duration checkLimitRefreshPeriod(Duration limitRefreshPeriod) {
        requireNonNull(limitRefreshPeriod, LIMIT_REFRESH_PERIOD_MUST_NOT_BE_NULL);
        boolean refreshPeriodIsTooShort = limitRefreshPeriod.compareTo(ACCEPTABLE_REFRESH_PERIOD) < 0;
        if (refreshPeriodIsTooShort) {
            throw new IllegalArgumentException("LimitRefreshPeriod is too short");
        }
        return limitRefreshPeriod;
    }

    private static int checkLimitForPeriod(final int limitForPeriod) {
        if (limitForPeriod < 1) {
            throw new IllegalArgumentException("LimitForPeriod should be greater than 0");
        }
        return limitForPeriod;
    }
}