【Springboot starter 组件开发】限流组件 RateLimiter

一、摘要
二、基于guava实现
- [2.1 核心依赖](#2.1 核心依赖)
- [2.2 核心逻辑](#2.2 核心逻辑)
[三、基于Redis + lua脚本实现](#三、基于Redis + lua脚本实现)
- [3.1 核心依赖](#3.1 核心依赖)
- [3.2 核心逻辑](#3.2 核心逻辑)

一、摘要

基于guava的RateLimiter，实现限流
基于redis + lua脚本(推荐，准确性高)，实现限流
掌握springboot starter的开发流程
源码地址：ratelimiter-spring-boot-starter

二、基于guava实现

2.1 核心依赖

xml 复制代码

<dependency>
    <groupId>com.google.guava</groupId>
    <artifactId>guava</artifactId>
    <version>23.5-jre</version>
</dependency>

2.2 核心逻辑

java 复制代码

@Slf4j
public class GuavaLimiter implements LimiterManager {

    private final Map<String, RateLimiter> limiterMap = Maps.newConcurrentMap();

    @Override
    public boolean tryAccess(LimiterEntity entity) {
        if (StringUtils.isBlank(entity.getKey())) {
            throw new LimiterException("Guava limiter key cannot be empty");
        }
        RateLimiter rateLimiter = getRateLimiter(entity);
        if (rateLimiter == null) {
            return false;
        }
        boolean result = rateLimiter.tryAcquire(entity.getPermitsPerSecond(), entity.getTimeout(), TimeUnit.SECONDS);
        log.info("Guava limiter tryAccess, key={}, result={}", entity.getKey(), result);
        return result;
    }

    private RateLimiter getRateLimiter(LimiterEntity entity) {
        String key = entity.getKey();
        // 先看缓存中是否存在
        if (!limiterMap.containsKey(key)) {
            // 缓存中不存在，则创建令牌桶，预热时间设置为1s
            RateLimiter rateLimiter = RateLimiter.create(entity.getPermitsPerSecond(), 1, TimeUnit.SECONDS);
            limiterMap.put(key, rateLimiter);
            log.info("Guava limiter new bucket, key={}, permits={}", key, entity.getPermitsPerSecond());
            return rateLimiter;
        }
        return limiterMap.get(key);
    }
}

三、基于Redis + lua脚本实现

3.1 核心依赖

xml 复制代码

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-redis</artifactId>
    <scope>provided</scope>
</dependency>

3.2 核心逻辑

java 复制代码

@Slf4j
public class RedisLimiter implements LimiterManager {

    private final StringRedisTemplate stringRedisTemplate;

    public RedisLimiter(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    @Override
    public boolean tryAccess(LimiterEntity entity) {

        if (StringUtils.isBlank(entity.getKey())) {
            throw new LimiterException("Redis limiter key cannot be empty");
        }
        List<String> keys = Collections.singletonList(entity.getKey());

        double permitsPerSecond = entity.getPermitsPerSecond();
        long timeout = entity.getTimeout();

        RedisScript<Long> redisScript = new DefaultRedisScript<>(buildLuaScript(), Long.class);

        Long count = stringRedisTemplate.execute(redisScript, keys, "" + permitsPerSecond, "" + timeout);

        log.info("Redis limiter tryAccess, key={}, count={} ", entity.getKey(), count);

        return count != null && count != 0;
    }

    private String buildLuaScript() {
        return "--获取KEY\n" +
                "local key = KEYS[1]\n" +
                "\n" +
                "local limit = tonumber(ARGV[1])\n" +
                "\n" +
                "local curentLimit = tonumber(redis.call('get', key) or \"0\")\n" +
                "\n" +
                "if curentLimit + 1 > limit\n" +
                "    then return 0\n" +
                "else\n" +
                "    -- 自增长 1\n" +
                "    redis.call('INCRBY', key, 1)\n" +
                "    -- 设置过期时间\n" +
                "    redis.call('EXPIRE', key, ARGV[2])\n" +
                "    return curentLimit + 1\n" +
                "end";
    }
}