如何理解spring-cloud-gateway自带redis限流脚本
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filter入口: org.springframework.cloud.gateway.filter.factory.RequestRateLimiterGatewayFilterFactory#apply
限流判断入口: org.springframework.cloud.gateway.filter.ratelimit.RedisRateLimiter#isAllowed
@Override @SuppressWarnings("unchecked") public MonoisAllowed(String routeId, String id) { if (!this.initialized.get()) { throw new IllegalStateException("RedisRateLimiter is not initialized"); } Config routeConfig = loadConfiguration(routeId); // How many requests per second do you want a user to be allowed to do? int replenishRate = routeConfig.getReplenishRate(); // How much bursting do you want to allow? int burstCapacity = routeConfig.getBurstCapacity(); try { List keys = getKeys(id); // The arguments to the LUA script. time() returns unixtime in seconds. List scriptArgs = Arrays.asList(replenishRate + "", burstCapacity + "", Instant.now().getEpochSecond() + "", "1"); // allowed, tokens_left = redis.eval(SCRIPT, keys, args) Flux > flux = this.redisTemplate.execute(this.script, keys, scriptArgs); // .log("redisratelimiter", Level.FINER); return flux.onErrorResume(throwable -> Flux.just(Arrays.asList(1L, -1L))) .reduce(new ArrayList
(), (longs, l) -> { longs.addAll(l); return longs; }).map(results -> { boolean allowed = results.get(0) == 1L; Long tokensLeft = results.get(1); Response response = new Response(allowed, getHeaders(routeConfig, tokensLeft)); if (log.isDebugEnabled()) { log.debug("response: " + response); } return response; }); } catch (Exception e) { /* * We don't want a hard dependency on Redis to allow traffic. Make sure to set * an alert so you know if this is happening too much. Stripe's observed * failure rate is 0.01%. */ log.error("Error determining if user allowed from redis", e); } return Mono.just(new Response(true, getHeaders(routeConfig, -1L))); }
lua脚本加载入口: org.springframework.cloud.gateway.config.GatewayRedisAutoConfiguration#redisRequestRateLimiterScript
@Bean @SuppressWarnings("unchecked") public RedisScript redisRequestRateLimiterScript() { DefaultRedisScript redisScript = new DefaultRedisScript<>(); redisScript.setScriptSource(new ResourceScriptSource( new ClassPathResource("META-INF/scripts/request_rate_limiter.lua"))); redisScript.setResultType(List.class); return redisScript; }
request_rate_limiter.lua脚本
local tokens_key = KEYS[1] local timestamp_key = KEYS[2] --redis.log(redis.LOG_WARNING, "tokens_key " .. tokens_key) local rate = tonumber(ARGV[1]) local capacity = tonumber(ARGV[2]) local now = tonumber(ARGV[3]) local requested = tonumber(ARGV[4]) local fill_time = capacity/rate local ttl = math.floor(fill_time*2) --redis.log(redis.LOG_WARNING, "rate " .. ARGV[1]) --redis.log(redis.LOG_WARNING, "capacity " .. ARGV[2]) --redis.log(redis.LOG_WARNING, "now " .. ARGV[3]) --redis.log(redis.LOG_WARNING, "requested " .. ARGV[4]) --redis.log(redis.LOG_WARNING, "filltime " .. fill_time) --redis.log(redis.LOG_WARNING, "ttl " .. ttl) local last_tokens = tonumber(redis.call("get", tokens_key)) if last_tokens == nil then last_tokens = capacity end --redis.log(redis.LOG_WARNING, "last_tokens " .. last_tokens) local last_refreshed = tonumber(redis.call("get", timestamp_key)) if last_refreshed == nil then last_refreshed = 0 end --redis.log(redis.LOG_WARNING, "last_refreshed " .. last_refreshed) local delta = math.max(0, now-last_refreshed) --重点是这里,rate是相对于capacity而言,如果大于等于capacity,那么每秒的并发量就是capacity, --如果小于capacity,那么才会每秒固定添加rate个令牌到桶中。 --正常限流建议设置小于capacity,否则当capacity瞬间用完,这个时候说明已经达到了系统最大并发阀值, --下一秒瞬间又恢复最大令牌桶阀值,速率过大反而起不到限流作用。 local filled_tokens = math.min(capacity, last_tokens+(delta*rate)) local allowed = filled_tokens >= requested local new_tokens = filled_tokens local allowed_num = 0 if allowed then new_tokens = filled_tokens - requested allowed_num = 1 end --redis.log(redis.LOG_WARNING, "delta " .. delta) --redis.log(redis.LOG_WARNING, "filled_tokens " .. filled_tokens) --redis.log(redis.LOG_WARNING, "allowed_num " .. allowed_num) --redis.log(redis.LOG_WARNING, "new_tokens " .. new_tokens) redis.call("setex", tokens_key, ttl, new_tokens) redis.call("setex", timestamp_key, ttl, now) return { allowed_num, new_tokens }
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