Guava中的RateLimiter可以限制单进程中某个方法的速率，本文主要介绍如何使用，实现原理请参考文档：推荐：超详细的Guava RateLimiter限流原理解析和推荐：RateLimiter 源码分析(Guava 和 Sentinel 实现)。
1 基于spring-mvc的controller测试限流
完整代码可参考：https://github.com/sxpujs/spring-cloud-examples/tree/master/rest-service
1.1 增加Maven依赖：
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>29.0-jre</version>
</dependency>
1.2 AccessLimitService 限流Service类
@Service
public class AccessLimitService {
// 每秒发出5个令牌
RateLimiter rateLimiter = RateLimiter.create(5.0);
/**
* 尝试获取令牌
*/
public boolean tryAcquire() {
return rateLimiter.tryAcquire();
}
}
1.3 控制器类
@RestController
@Slf4j
public class HelloController {
@Autowired
private AccessLimitService accessLimitService;
@RequestMapping("/access")
public String access() {
if (accessLimitService.tryAcquire()) {
log.info("start");
// 模拟业务执行500毫秒
try {
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
}
return "access success [" + LocalDateTime.now() + "]";
} else {
//log.warn("限流");
return "access limit [" + LocalDateTime.now() + "]";
}
}
}
1.4 使用wrk工具模拟客户端发起多个请求
我们使用HTTP基准工具wrk来生成大量HTTP请求。在终端输入如下命令来测试：
wrk -t1 -c10 -d2s http://127.0.0.1:8080/access
服务端日志如下所示（稍做简化），可以看出前6行的执行时间是一样的，这是因为RateLimiter的默认实现SmoothBursty会缓存1秒的许可，在定义RateLimiter实例时，每秒5个许可，加上新占用的1个许可，一共有6个。从第7行开始，每0.2秒执行1次，符合预期。
2020-07-05 15:46:16.605 INFO --- [nio-8080-exec-2] HelloController : start
2020-07-05 15:46:16.605 INFO --- [nio-8080-exec-3] HelloController : start
2020-07-05 15:46:16.605 INFO --- [nio-8080-exec-7] HelloController : start
2020-07-05 15:46:16.605 INFO --- [nio-8080-exec-8] HelloController : start
2020-07-05 15:46:16.605 INFO --- [nio-8080-exec-9] HelloController : start
2020-07-05 15:46:16.605 INFO --- [nio-8080-exec-4] HelloController : start
2020-07-05 15:46:16.804 INFO --- [nio-8080-exec-1] HelloController : start
2020-07-05 15:46:17.005 INFO --- [io-8080-exec-11] HelloController : start
2020-07-05 15:46:17.204 INFO --- [nio-8080-exec-9] HelloController : start
2020-07-05 15:46:17.404 INFO --- [nio-8080-exec-5] HelloController : start
2020-07-05 15:46:17.604 INFO --- [nio-8080-exec-8] HelloController : start
2020-07-05 15:46:17.804 INFO --- [nio-8080-exec-2] HelloController : start
2020-07-05 15:46:18.004 INFO --- [nio-8080-exec-7] HelloController : start
2020-07-05 15:46:18.204 INFO --- [nio-8080-exec-6] HelloController : start
2020-07-05 15:46:18.404 INFO --- [nio-8080-exec-5] HelloController : start
2 基于单个类的main方法测试限流
package com.demo.guava;
import com.google.common.util.concurrent.RateLimiter;
import lombok.extern.slf4j.Slf4j;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.stream.IntStream;
@Slf4j
public class RateLimiterDemo {
static void submitTasks1() {
ExecutorService pool = Executors.newFixedThreadPool(10);
RateLimiter rateLimiter = RateLimiter.create(5); // rate is "5 permits per second"
IntStream.range(0, 10).forEach(i -> pool.submit(() -> {
if (rateLimiter.tryAcquire()) {
try {
log.info("start");
Thread.sleep(500);
} catch (InterruptedException e) {
}
} else {
log.warn("限流");
}
}));
pool.shutdown();
/*
16:18:18.784 [pool-1-thread-1] INFO RateLimiterDemo - start
16:18:18.784 [pool-1-thread-7] WARN RateLimiterDemo - 限流
16:18:18.784 [pool-1-thread-2] WARN RateLimiterDemo - 限流
16:18:18.784 [pool-1-thread-4] WARN RateLimiterDemo - 限流
16:18:18.784 [pool-1-thread-5] WARN RateLimiterDemo - 限流
16:18:18.784 [pool-1-thread-6] WARN RateLimiterDemo - 限流
16:18:18.784 [pool-1-thread-9] WARN RateLimiterDemo - 限流
16:18:18.784 [pool-1-thread-3] WARN RateLimiterDemo - 限流
16:18:18.784 [pool-1-thread-10] WARN RateLimiterDemo - 限流
16:18:18.784 [pool-1-thread-8] WARN RateLimiterDemo - 限流
*/
}
static void submitTasks2() {
ExecutorService pool = Executors.newFixedThreadPool(10);
RateLimiter rateLimiter = RateLimiter.create(5); // rate is "5 permits per second"
IntStream.range(0, 10).forEach(i -> pool.submit(() -> {
rateLimiter.acquire();
log.info("start");
try {
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
}
}));
pool.shutdown();
/*
16:18:56.030 [pool-1-thread-1] INFO RateLimiterDemo - start
16:18:56.227 [pool-1-thread-10] INFO RateLimiterDemo - start
16:18:56.428 [pool-1-thread-9] INFO RateLimiterDemo - start
16:18:56.627 [pool-1-thread-8] INFO RateLimiterDemo - start
16:18:56.827 [pool-1-thread-7] INFO RateLimiterDemo - start
16:18:57.028 [pool-1-thread-6] INFO RateLimiterDemo - start
16:18:57.226 [pool-1-thread-5] INFO RateLimiterDemo - start
16:18:57.426 [pool-1-thread-4] INFO RateLimiterDemo - start
16:18:57.629 [pool-1-thread-3] INFO RateLimiterDemo - start
16:18:57.826 [pool-1-thread-2] INFO RateLimiterDemo - start
*/
}
static void submitTasks3() {
RateLimiter r = RateLimiter.create(5);
log.info("start");
for (;;) {
log.info("get 1 tokens: " + r.acquire() + "s");
}
/*
16:15:46.310 [main] INFO RateLimiterDemo - start
16:15:46.315 [main] INFO RateLimiterDemo - get 1 tokens: 0.0s
16:15:46.513 [main] INFO RateLimiterDemo - get 1 tokens: 0.193752s
16:15:46.709 [main] INFO RateLimiterDemo - get 1 tokens: 0.194875s
16:15:46.911 [main] INFO RateLimiterDemo - get 1 tokens: 0.199033s
16:15:47.113 [main] INFO RateLimiterDemo - get 1 tokens: 0.197833s
16:15:47.312 [main] INFO RateLimiterDemo - get 1 tokens: 0.195898s
*/
}
static void submitTasks4() {
RateLimiter r = RateLimiter.create(5);
log.info("start");
for (;;) {
if (r.tryAcquire()) {
log.info("run");
}
}
/*
16:17:17.098 [main] INFO RateLimiterDemo - start
16:17:17.100 [main] INFO RateLimiterDemo - run
16:17:17.296 [main] INFO RateLimiterDemo - run
16:17:17.496 [main] INFO RateLimiterDemo - run
16:17:17.696 [main] INFO RateLimiterDemo - run
*/
}
public static void main(String[] args) throws InterruptedException {
//submitTasks1();
submitTasks2();
//submitTasks3();
//submitTasks4();
}
}
参考文档：
- 官方API：Class RateLimiter
- Baeldung: Quick Guide to the Guava RateLimiter
- Guava-RateLimiter详解
- 并发编程网：Guava官方文档-RateLimiter类
- 推荐：超详细的Guava RateLimiter限流原理解析
- 推荐：RateLimiter 源码分析(Guava 和 Sentinel 实现)
- 阿里巴巴Sentinel框架
来源：oschina
链接：https://my.oschina.net/u/4409634/blog/4336749