一、摘要

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

二、基于guava实现

2.1 核心依赖

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

2.2 核心逻辑

@Slf4j
public class GuavaLimiter implements LimiterManager {private final Map<String, RateLimiter> limiterMap = Maps.newConcurrentMap();@Overridepublic 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1sRateLimiter 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

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

3.2 核心逻辑

@Slf4j
public class RedisLimiter implements LimiterManager {private final StringRedisTemplate stringRedisTemplate;public RedisLimiter(StringRedisTemplate stringRedisTemplate) {this.stringRedisTemplate = stringRedisTemplate;}@Overridepublic 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";}
}