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Spring Cloud 使用 Resilience4j 实现服务熔断的方法

作者:dk168

服务熔断是为了保护我们的服务,比如当某个服务出现问题的时候,控制打向它的流量,让它有时间去恢复,或者限制一段时间只能有固定数量的请求打向这个服务,这篇文章主要介绍了Spring Cloud 使用 Resilience4j 实现服务熔断,需要的朋友可以参考下

CircuitBreaker 断路器

服务熔断是为了保护我们的服务,比如当某个服务出现问题的时候,控制打向它的流量,让它有时间去恢复,或者限制一段时间只能有固定数量的请求打向这个服务。这些都是保护措施。我在实际工作中也确实遇到过,数据库出现问题了,进而导致Web服务出现问题了,导致不依赖数据库的服务也出现问题了,出现一连串问题。 这次学习《玩转 Spring 全家桶》,丁雪丰老师给了使用resilience4j的例子。 丁老师的例子是2019年的,这个框架已经修改了些方法,所以我自己也花了些时间来理解了它的用法。现将过程记录下来。
首先POM文件引入

<dependency>
    <groupId>io.github.resilience4j</groupId>
    <artifactId>resilience4j-spring-boot2</artifactId>
    <version>2.0.2</version>
</dependency>

接着改造之前的Controller方法

@RestController
@RequestMapping("/customer")
@Slf4j
public class BookController {

    @Autowired
    private BookService bookService;

    private CircuitBreaker circuitBreaker;

    public BookController(CircuitBreakerRegistry registry) {
        circuitBreaker = registry.circuitBreaker("menu");
    }

    @GetMapping("/menu")
    public List<Book> readMenu() {
        Supplier<List<Book>> supplier = () -> bookService.getAll();
        circuitBreaker.getEventPublisher()
                .onEvent(event -> log.info(event.toString()));
        try{
            return circuitBreaker.executeSupplier(supplier);
        }
        catch (Exception ex)
        {
            log.error(ex.getMessage());
            return Collections.emptyList();
        }
    }
}

不同的地方就是引入了CircuitBreaker, 然后使用它将我们的方法“bookService.getAll()”包起来了。
然后在配置文件中添加如下的配置

resilience4j.circuitbreaker.backends.menu.failure-rate-threshold=50
resilience4j.circuitbreaker.backends.menu.wait-duration-in-open-state=60000
resilience4j.circuitbreaker.backends.menu.sliding-window-size=5
resilience4j.circuitbreaker.backends.menu.permitted-number-of-calls-in-half-open-state=2
resilience4j.circuitbreaker.backends.menu.minimum-number-of-calls=2

稍微解释一下这里的配置
failure-rate-threshold=50是说失败率超过50%就熔断,
wait-duration-in-open-state= 60000,是说熔断后等待60S才允许再次调用。
sliding-window-size =5 可以理解为5个请求统计一次,
permitted-number-of-calls-in-half-open-state = 2是说进入半开的状态的时候,还允许请求多少个。
minimum-number-of-calls=2是说最少有多少个请求才开始统计。 这里的参数都是我为了实验设置的,实际情况根据需要进行调整。参数比较多,具体可以参加官方文档
https://resilience4j.readme.io/docs/circuitbreaker

我们来看下实际的效果通过浏览器访问,
首先我们现打开BookService,让它有一次成功的请求,日志会输出
CircuitBreaker 'menu' recorded a successful call.
然后我们将BookService关闭,让它请求失败,日志会输出如下
CircuitBreaker 'menu' recorded an error: 'feign.RetryableException: Connection refused: no further information executing GET http://bookshop-service/book/getAll'. Elapsed time: 2050 ms
CircuitBreaker 'menu' exceeded failure rate threshold. Current failure rate: 50.0
CircuitBreaker 'menu' changed state from CLOSED to OPEN
可以看到断路器已经打开了,
接着我们继续访问会出现,
CircuitBreaker 'menu' recorded a call which was not permitted.
这个时候请求不会打到BookService上面了。就算这个时候我们的BookService恢复正常。
等待60s后进入半Open的状态
CircuitBreaker 'menu' changed state from OPEN to HALF_OPEN
这个时候恢复BookService正常,我们请求也会正常响应了
CircuitBreaker 'menu' recorded a successful call
多请求几次,断路器就从HALF_OPEN变成了CLOSED
CircuitBreaker 'menu' changed state from HALF_OPEN to CLOSED

这里给一个官方的状态图来说明

断路器有三个状态: CLOSED, OPEN, HALF_OPEN。

CLOSED是最开始的状态,也就是关闭状态,流量可以正常通过,当失败比率超过threshold后,断路器打开, 变成OPEN 打开后流量不可以通过;等待一定的时间后,断路器进入半开状态 HALF_OPEN, 这个时候如果失败率低于阈值,断路器进入CLOSED状态,如果超过阈值,断路器继续保证OPEN,再等待,如此往复。

断路器现在还支持设置慢请求,使用起来还是比较方便。对于参数的设置如果不是很理解,可以通过单元测试的方法来加深对它的理解。这里参考https://github.com/eugenp/tutorials/blob/master/libraries-6/src/test/java/com/baeldung/resilence4j/Resilience4jUnitTest.java 上面的例子,给出来个单元测试

    interface RemoteService {

        int process(int i);
    }

    private RemoteService service;

    @Test
    public void whenCircuitBreakerIsUsed_thenItWorksAsExpected() {
        service = mock(RemoteService.class);
        CircuitBreakerConfig config = CircuitBreakerConfig.custom()
                // Percentage of failures to start short-circuit
                .failureRateThreshold(20)
                .minimumNumberOfCalls(5)
                .build();
        CircuitBreakerRegistry registry = CircuitBreakerRegistry.of(config);
        CircuitBreaker circuitBreaker = registry.circuitBreaker("my");
        Function<Integer, Integer> decorated = CircuitBreaker.decorateFunction(circuitBreaker, service::process);

        when(service.process(anyInt())).thenThrow(new RuntimeException());
        circuitBreaker.getEventPublisher()
                .onEvent(event ->
                {
                    log.info(event.toString());
                });

        for (int i = 0; i < 10; i++) {
            try {
                decorated.apply(i);
            } catch (Exception ignore) {
            }
        }

        verify(service, times(5)).process(any(Integer.class));
    }

这里设置最少请求5次,失败率超过20%就熔断,然后我们请求了10次,实际上只调用了Service5次。
对于其它参数,你可以调整后,根据需要来验证是否符合预期。它的日志输出如下

CircuitBreaker 'my' recorded an error: 'java.lang.RuntimeException'. Elapsed time: 2 ms
CircuitBreaker 'my' recorded an error: 'java.lang.RuntimeException'. Elapsed time: 0 ms
CircuitBreaker 'my' recorded an error: 'java.lang.RuntimeException'. Elapsed time: 0 ms
CircuitBreaker 'my' recorded an error: 'java.lang.RuntimeException'. Elapsed time: 0 ms
CircuitBreaker 'my' recorded an error: 'java.lang.RuntimeException'. Elapsed time: 0 ms
CircuitBreaker 'my' exceeded failure rate threshold. Current failure rate: 100.0
CircuitBreaker 'my' changed state from CLOSED to OPEN
CircuitBreaker 'my' recorded a call which was not permitted.
CircuitBreaker 'my' recorded a call which was not permitted.
CircuitBreaker 'my' recorded a call which was not permitted.
CircuitBreaker 'my' recorded a call which was not permitted.
CircuitBreaker 'my' recorded a call which was not permitted.  

可以看到5次过后,就开始打开断路器,后面的call就不被允许了。

隔舱Bulkhead

Resilience4j 里面的Bulkhead可以简单的理解为允许多少个并发访问。我们这里还是通过单元测试的方法来演示它的功能

    @Test
    public void whenBulkheadIsUsed_thenItWorksAsExpected() throws InterruptedException {
        service = mock(RemoteService.class);
        BulkheadConfig config = BulkheadConfig.custom().maxConcurrentCalls(2).build();
        BulkheadRegistry registry = BulkheadRegistry.of(config);
        Bulkhead bulkhead = registry.bulkhead("my");
        Function<Integer, Integer> decorated = Bulkhead.decorateFunction(bulkhead, service::process);

       try {
            callAndBlock(decorated);
        }
       catch(BulkheadFullException ex)
        {
            log.error("isfull");
        }
        finally
        {
           verify(service, times(2)).process(any(Integer.class));
        }

    }

    private void callAndBlock(Function<Integer, Integer> decoratedService) throws InterruptedException {
        when(service.process(anyInt())).thenAnswer(invocation -> {
            log.info("service called");
            return null;
        });

        ArrayList<Integer> numberList = new ArrayList<Integer>();
        for(int i = 0;i<10;i++)
        {
            numberList.add(i);
        }

        numberList.parallelStream().forEach((i)->{
            try {
                decoratedService.apply(i);
            }
            catch (Exception ex)
            {
                log.error("meet error " + ex.getMessage());
            } catch (Throwable e) {
                throw new RuntimeException(e);
            }
        });
    }

首先我们解读一下callAndBlock, 它会并发的去执行一个function. 如果我们不用隔舱,它的输出会是这样。

2022-12-28T15:22:52.010+08:00  INFO 37276 --- [onPool-worker-4] c.k.r.bookcustomer.Resilience4jUnitTest  : service called
2022-12-28T15:22:52.010+08:00  INFO 37276 --- [onPool-worker-9] c.k.r.bookcustomer.Resilience4jUnitTest  : service called
2022-12-28T15:22:52.010+08:00  INFO 37276 --- [onPool-worker-5] c.k.r.bookcustomer.Resilience4jUnitTest  : service called
2022-12-28T15:22:52.010+08:00  INFO 37276 --- [onPool-worker-3] c.k.r.bookcustomer.Resilience4jUnitTest  : service called
2022-12-28T15:22:52.010+08:00  INFO 37276 --- [onPool-worker-1] c.k.r.bookcustomer.Resilience4jUnitTest  : service called
2022-12-28T15:22:52.010+08:00  INFO 37276 --- [onPool-worker-6] c.k.r.bookcustomer.Resilience4jUnitTest  : service called
2022-12-28T15:22:52.010+08:00  INFO 37276 --- [onPool-worker-7] c.k.r.bookcustomer.Resilience4jUnitTest  : service called
2022-12-28T15:22:52.010+08:00  INFO 37276 --- [onPool-worker-8] c.k.r.bookcustomer.Resilience4jUnitTest  : service called
2022-12-28T15:22:52.010+08:00  INFO 37276 --- [onPool-worker-2] c.k.r.bookcustomer.Resilience4jUnitTest  : service called
2022-12-28T15:22:52.011+08:00  INFO 37276 --- [           main] c.k.r.bookcustomer.Resilience4jUnitTest  : service called

可以看到启动了10个线程去访问方法。加了隔舱后,隔舱限定了一次只能两个,输出如下

2022-12-28T15:33:48.648+08:00 ERROR 32256 --- [onPool-worker-4] c.k.r.bookcustomer.Resilience4jUnitTest  : meet error Bulkhead 'my' is full and does not permit further calls
2022-12-28T15:33:48.648+08:00 ERROR 32256 --- [onPool-worker-6] c.k.r.bookcustomer.Resilience4jUnitTest  : meet error Bulkhead 'my' is full and does not permit further calls
2022-12-28T15:33:48.648+08:00 ERROR 32256 --- [onPool-worker-7] c.k.r.bookcustomer.Resilience4jUnitTest  : meet error Bulkhead 'my' is full and does not permit further calls
2022-12-28T15:33:48.648+08:00 ERROR 32256 --- [onPool-worker-4] c.k.r.bookcustomer.Resilience4jUnitTest  : meet error Bulkhead 'my' is full and does not permit further calls
2022-12-28T15:33:48.648+08:00 ERROR 32256 --- [onPool-worker-8] c.k.r.bookcustomer.Resilience4jUnitTest  : meet error Bulkhead 'my' is full and does not permit further calls
2022-12-28T15:33:48.648+08:00 ERROR 32256 --- [onPool-worker-5] c.k.r.bookcustomer.Resilience4jUnitTest  : meet error Bulkhead 'my' is full and does not permit further calls
2022-12-28T15:33:48.648+08:00 ERROR 32256 --- [onPool-worker-2] c.k.r.bookcustomer.Resilience4jUnitTest  : meet error Bulkhead 'my' is full and does not permit further calls
2022-12-28T15:33:48.648+08:00 ERROR 32256 --- [onPool-worker-3] c.k.r.bookcustomer.Resilience4jUnitTest  : meet error Bulkhead 'my' is full and does not permit further calls
2022-12-28T15:33:48.650+08:00  INFO 32256 --- [onPool-worker-1] c.k.r.bookcustomer.Resilience4jUnitTest  : service called
2022-12-28T15:33:48.650+08:00  INFO 32256 --- [           main] c.k.r.bookcustomer.Resilience4jUnitTest  : service called

可以看到只有两次成功的访问,其它的访问都被block了。

限速器RateLimiter

RateLimiter的功能是限定一段时间内允许多少次访问,还是使用和Bulkhead一样的例子一样

 @Test
    public void whenRateLimiterInUse_thenItWorksAsExpected() throws InterruptedException {
        service = mock(RemoteService.class);

        RateLimiterConfig config = RateLimiterConfig.custom()
                .limitRefreshPeriod(Duration.ofMillis(1000))
                .limitForPeriod(4)
                .timeoutDuration(Duration.ofMillis(25))
                .build();

        RateLimiterRegistry rateLimiterRegistry = RateLimiterRegistry.of(config);

        RateLimiter rateLimiter = rateLimiterRegistry
                .rateLimiter("name1");

        CheckedFunction<Integer, Integer> decorated = RateLimiter
                .decorateCheckedFunction(rateLimiter, service::process);

        try {
            callAndBlock(decorated);
        }
        catch(Exception ex)
        {
            log.error("isfull");
        }
        finally
        {
            verify(service, times(4)).process(any(Integer.class));
        }

    }

    private void callAndBlock(CheckedFunction<Integer, Integer> decoratedService) throws InterruptedException {
        when(service.process(anyInt())).thenAnswer(invocation -> {
            log.info("service called");
            return null;
        });

        ArrayList<Integer> numberList = new ArrayList<Integer>();
        for(int i = 0;i<10;i++)
        {
            numberList.add(i);
        }

        numberList.parallelStream().forEach((i)->{
            try {
                decoratedService.apply(i);
            }
            catch (Exception ex)
            {
                log.error("meet error " + ex.getMessage());
            } catch (Throwable e) {
                throw new RuntimeException(e);
            }
        });
    }

我们这里故意设置1S中允许访问4次,实际的运行情况也是只允许了4次。日志输出如下

2022-12-28T15:39:52.027+08:00  INFO 35236 --- [onPool-worker-2] c.k.r.bookcustomer.Resilience4jUnitTest  : service called
2022-12-28T15:39:52.027+08:00  INFO 35236 --- [onPool-worker-5] c.k.r.bookcustomer.Resilience4jUnitTest  : service called
2022-12-28T15:39:52.027+08:00  INFO 35236 --- [           main] c.k.r.bookcustomer.Resilience4jUnitTest  : service called
2022-12-28T15:39:52.027+08:00  INFO 35236 --- [onPool-worker-7] c.k.r.bookcustomer.Resilience4jUnitTest  : service called
2022-12-28T15:39:52.053+08:00 ERROR 35236 --- [onPool-worker-6] c.k.r.bookcustomer.Resilience4jUnitTest  : meet error RateLimiter 'name1' does not permit further calls
2022-12-28T15:39:52.060+08:00 ERROR 35236 --- [onPool-worker-3] c.k.r.bookcustomer.Resilience4jUnitTest  : meet error RateLimiter 'name1' does not permit further calls
2022-12-28T15:39:52.060+08:00 ERROR 35236 --- [onPool-worker-9] c.k.r.bookcustomer.Resilience4jUnitTest  : meet error RateLimiter 'name1' does not permit further calls
2022-12-28T15:39:52.060+08:00 ERROR 35236 --- [onPool-worker-1] c.k.r.bookcustomer.Resilience4jUnitTest  : meet error RateLimiter 'name1' does not permit further calls
2022-12-28T15:39:52.060+08:00 ERROR 35236 --- [onPool-worker-8] c.k.r.bookcustomer.Resilience4jUnitTest  : meet error RateLimiter 'name1' does not permit further calls
2022-12-28T15:39:52.075+08:00 ERROR 35236 --- [onPool-worker-4] c.k.r.bookcustomer.Resilience4jUnitTest  : meet error RateLimiter 'name1' does not permit further calls

限速器这个功能只能限制在整体性能上面,如果要限制某个用户,只能某段时间访问多少次,它就做不到了。

Relilience4j 里面还提供了Retry,TimeLimiter,Cache. 感觉不是很有必要的功能, Retry在spring里面有相应的功能了,没有必要专门为了使用它而多加个包。 TimeLimiter,Cache 我感觉不是很受重视的功能,连例子文档都懒得提供,可见意义不大。

到此这篇关于Spring Cloud 使用 Resilience4j 实现服务熔断的方法的文章就介绍到这了,更多相关Spring Cloud 服务熔断内容请搜索脚本之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持脚本之家!

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