-- rateLimiter.lua
local key = KEYS[1]
local requests = tonumber(redis.call('GET', key) or '-1')
local max_requests = tonumber(ARGV[1])
local expiry = tonumber(ARGV[2])
if (requests == -1) or (requests < max_requests) then
redis.call('INCR', key)
redis.call('EXPIRE', key, expiry)
return false
else
return true
end@Bean
public RedisScript<Boolean> script() {
return RedisScript.of(new ClassPathResource("scripts/rateLimiter.lua"), Boolean.class);
}class RateLimiterHandlerFilterFunction implements HandlerFilterFunction<ServerResponse, ServerResponse> {
private ReactiveRedisTemplate<String, Long> redisTemplate;
private RedisScript<Boolean> script;
private Long maxRequestPerMinute;
public RateLimiterHandlerFilterFunction(ReactiveRedisTemplate<String, Long> redisTemplate,
RedisScript<Boolean> script, Long maxRequestPerMinute) {
this.redisTemplate = redisTemplate;
this.script = script;
this.maxRequestPerMinute = maxRequestPerMinute;
}@Override
public Mono<ServerResponse> filter(ServerRequest request, HandlerFunction<ServerResponse> next) {
int currentMinute = LocalTime.now().getMinute();
String key = String.format("rl_%s:%s", requestAddress(request.remoteAddress()), currentMinute);
return redisTemplate //
.execute(script, List.of(key), List.of(maxRequestPerMinute, 59)) //
.single(false) //
.flatMap(value -> value ? //
ServerResponse.status(TOO_MANY_REQUESTS).build() : //
next.handle(request));
}@Value("${MAX_REQUESTS_PER_MINUTE}")
Long maxRequestPerMinute;MAX_REQUESTS_PER_MINUTE=20@Bean
RouterFunction<ServerResponse> routes() {
return route() //
.GET("/api/ping", r -> ok() //
.contentType(TEXT_PLAIN) //
.body(BodyInserters.fromValue("PONG")) //
).filter(new RateLimiterHandlerFilterFunction(redisTemplate, script(), maxRequestPerMinute)).build();
}for n in {1..22}; do echo $(curl -s -w " :: HTTP %{http_code}, %{size_download} bytes, %{time_total} s" -X GET http://localhost:8080/api/ping); sleep 0.5; done➜ for n in {1..22}; do echo $(curl -s -w " :: HTTP %{http_code}, %{size_download} bytes, %{time_total} s" -X GET http://localhost:8080/api/ping); sleep 0.5; done
PONG :: HTTP 200, 4 bytes, 0.173759 s
PONG :: HTTP 200, 4 bytes, 0.008903 s
PONG :: HTTP 200, 4 bytes, 0.008796 s
PONG :: HTTP 200, 4 bytes, 0.009625 s
PONG :: HTTP 200, 4 bytes, 0.007604 s
PONG :: HTTP 200, 4 bytes, 0.008052 s
PONG :: HTTP 200, 4 bytes, 0.011364 s
PONG :: HTTP 200, 4 bytes, 0.012158 s
PONG :: HTTP 200, 4 bytes, 0.010415 s
PONG :: HTTP 200, 4 bytes, 0.010373 s
PONG :: HTTP 200, 4 bytes, 0.010009 s
PONG :: HTTP 200, 4 bytes, 0.006587 s
PONG :: HTTP 200, 4 bytes, 0.006807 s
PONG :: HTTP 200, 4 bytes, 0.006970 s
PONG :: HTTP 200, 4 bytes, 0.007948 s
PONG :: HTTP 200, 4 bytes, 0.007949 s
PONG :: HTTP 200, 4 bytes, 0.006606 s
PONG :: HTTP 200, 4 bytes, 0.006336 s
PONG :: HTTP 200, 4 bytes, 0.007855 s
PONG :: HTTP 200, 4 bytes, 0.006515 s
:: HTTP 429, 0 bytes, 0.006633 s
:: HTTP 429, 0 bytes, 0.008264 s1630342834.878972 [0 172.17.0.1:65008] "EVALSHA" "16832548450a4b1c5e23ffab55bddefe972fecd2" "1" "rl_localhost:0" "20" "59"
1630342834.879044 [0 lua] "GET" "rl_localhost:0"
1630342834.879091 [0 lua] "INCR" "rl_localhost:0"
1630342834.879141 [0 lua] "EXPIRE" "rl_localhost:0" "59"
1630342835.401937 [0 172.17.0.1:65008] "EVALSHA" "16832548450a4b1c5e23ffab55bddefe972fecd2" "1" "rl_localhost:0" "20" "59"
1630342835.402009 [0 lua] "GET" "rl_localhost:0"One way to improve our implementation is by moving the responsibility of
performing the INCR and EXPIRE operations from the incrAndExpireKey
method, to a Lua script.
Redis has the ability to execute Lua scripts on the server side. Lua scripts
are executed atomically, that is, no other script or command will run
while a script is running, which gives us the same transactional semantics as MULTI / EXEC.
Below is a simple Lua script to encapsulate the rate limiting logic. The script returns true
if the request is to be rejected or false otherwise:
Place the script under src/main/resources/scripts. Now, Let's break it down:
KEYS[]) and arguments (ARGV[]) in our case
we are expecting one key in KEYS[1] (Lua arrays are 1-based)requests by making a call to the GET command,
returning -1 if the key does not exist, and converting the value to a number.ARGV[1]) and stored in max_requests, the
expiry in seconds is the second argument and stored in expiryif statement checks whether the request is the first request in the time window or
if the number of requests have not exceeded the quota, in which case we run the INCR-EXPIRE
commands and retunr false (meaning we are not rate limiting and allowing the request through).trueIf you want to learn more about Lua, see Programming in Lua.
Spring Data Redis supports Lua scripting via the class RedisScript. It handles serialization and intelligently
uses the Redis script cache. The cache is populated using the SCRIPT LOAD command. The default ScriptExecutor
uses EVALSHA using the SHA1 of the script and falling back to
EVAL if the script has not yet been loaded into the cache.
Let's add the bean annotated method script() to load our script from the classpath:
Next, we'll modify the filter to include the script as well as the quota; the value that we need to pass to the script:
Now we can modify the filter method to use the script. Scripts are run using the execute methods of
RedisTemplate or ReactiveRedisTemplate. The execute methods use a configurable ScriptExecutor/ReactiveScriptExecutor
that inherits the key and value serialization setting of the template to run the scripts:
Let's break down the method additions:
filter method uses the template execute method passing the script, keys and arguments.single result (true or false). The single method takes a default value to
be returned in case we get an empty result.flatMap method to grab the value:true we reject the request with an HTTP 429.false we handle the requestLet's add a configurable @Value annotated Long value to the FixedWindowRateLimiterApplication to
hold the request quota.
In our application.properties we'll set it to a max of 20 request per minute:
To invoke the filter we use the newly modified constructor, passing the template, the script, and the
maxRequestPerMinute value:
Using our trusty curl loop:
You should see the 21st request being rejected:
If we run Redis in monitor mode, we should see the Lua calls to EVALSHA, followed by the call to GET for a rejected
request, and the same plus calls to INCR and EXPIRE for an allowed request:
The complete code for this implementation is under the branch
with_lua.