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本文主要研究下resilience4j的基本功能

maven

        <dependency><groupId>io.github.resilience4j</groupId><artifactId>resilience4j-circuitbreaker</artifactId><version>0.13.0</version></dependency><dependency><groupId>io.github.resilience4j</groupId><artifactId>resilience4j-ratelimiter</artifactId><version>0.13.0</version></dependency><dependency><groupId>io.github.resilience4j</groupId><artifactId>resilience4j-retry</artifactId><version>0.13.0</version></dependency><dependency><groupId>io.github.resilience4j</groupId><artifactId>resilience4j-bulkhead</artifactId><version>0.13.0</version></dependency><dependency><groupId>io.github.resilience4j</groupId><artifactId>resilience4j-circularbuffer</artifactId><version>0.13.0</version></dependency><dependency><groupId>io.github.resilience4j</groupId><artifactId>resilience4j-timelimiter</artifactId><version>0.13.0</version></dependency>

CircuitBreaker

    @Testpublic void testCircuitBreaker(){// Create a CircuitBreaker (use default configuration)CircuitBreakerConfig circuitBreakerConfig = CircuitBreakerConfig.custom().enableAutomaticTransitionFromOpenToHalfOpen().build();CircuitBreaker circuitBreaker = CircuitBreaker.of("backendName",circuitBreakerConfig);String result = circuitBreaker.executeSupplier(() -> backendService.doSomethingWithArgs("world"));System.out.println(result);}

CircuitBreaker主要是实现针对接口异常的断路统计以及断路处理

Timelimiter

    @Testpublic void testTimelimiter(){ExecutorService executorService = Executors.newSingleThreadExecutor();TimeLimiterConfig config = TimeLimiterConfig.custom().timeoutDuration(Duration.ofMillis(600)).cancelRunningFuture(true).build();TimeLimiter timeLimiter = TimeLimiter.of(config);Supplier<Future<String>> futureSupplier = () -> {return executorService.submit(backendService::doSomethingThrowException);};Callable<String> restrictedCall = TimeLimiter.decorateFutureSupplier(timeLimiter,futureSupplier);Try.of(restrictedCall::call).onFailure(throwable -> System.out.println("We might have timed out or the circuit breaker has opened."));}

主要是实现超时的控制

Bulkhead

    /*** A Bulkhead can be used to limit the amount of parallel executions*/@Testpublic void testBulkhead(){Bulkhead bulkhead = Bulkhead.of("test", BulkheadConfig.custom().maxConcurrentCalls(1).build());Supplier<String> decoratedSupplier = Bulkhead.decorateSupplier(bulkhead, backendService::doSomethingSlowly);IntStream.rangeClosed(1,2).parallel().forEach(i -> {String result = Try.ofSupplier(decoratedSupplier).recover(throwable -> "Hello from Recovery").get();System.out.println(result);});}

Bulkhead目前来看是用来控制并行(parallel)调用的次数

RateLimiter

    @Testpublic void testRateLimiter(){// Create a custom RateLimiter configurationRateLimiterConfig config = RateLimiterConfig.custom().timeoutDuration(Duration.ofMillis(100)).limitRefreshPeriod(Duration.ofSeconds(1)).limitForPeriod(1).build();// Create a RateLimiterRateLimiter rateLimiter = RateLimiter.of("backendName", config);// Decorate your call to BackendService.doSomething()Supplier<String> restrictedSupplier = RateLimiter.decorateSupplier(rateLimiter, backendService::doSomething);IntStream.rangeClosed(1,5).parallel().forEach(i -> {Try<String> aTry = Try.ofSupplier(restrictedSupplier);System.out.println(aTry.isSuccess());});}

用来做流控

Fallback

    @Testpublic void testFallback(){// Execute the decorated supplier and recover from any exceptionString result = Try.ofSupplier(() -> backendService.doSomethingThrowException()).recover(throwable -> "Hello from Recovery").get();System.out.println(result);}@Testpublic void testCircuitBreakerAndFallback(){CircuitBreaker circuitBreaker = CircuitBreaker.ofDefaults("backendName");Supplier<String> decoratedSupplier = CircuitBreaker.decorateSupplier(circuitBreaker, backendService::doSomethingThrowException);String result = Try.ofSupplier(decoratedSupplier).recover(throwable -> "Hello from Recovery").get();System.out.println(result);}

fallback基本上是高可用操作的标配

Retry

    @Testpublic void testRetry(){CircuitBreaker circuitBreaker = CircuitBreaker.ofDefaults("backendName");// Create a Retry with at most 3 retries and a fixed time interval between retries of 500msRetry retry = Retry.ofDefaults("backendName");// Decorate your call to BackendService.doSomething() with a CircuitBreakerSupplier<String> decoratedSupplier = CircuitBreaker.decorateSupplier(circuitBreaker, backendService::doSomething);// Decorate your call with automatic retrydecoratedSupplier = Retry.decorateSupplier(retry, decoratedSupplier);// Execute the decorated supplier and recover from any exceptionString result = Try.ofSupplier(decoratedSupplier).recover(throwable -> "Hello from Recovery").get();System.out.println(result);}

retry用来控制重试

小结

resilience4j是一款受hystrix启发的容错组件，提供了如下几款核心组件：

• resilience4j-circuitbreaker: Circuit breaking
• resilience4j-ratelimiter: Rate limiting
• resilience4j-bulkhead: Bulkheading
• resilience4j-retry: Automatic retrying (sync and async)
• resilience4j-cache: Response caching 这里主要演示了关于circuitbreaker、ratelimiter、bulkhead、retry以及timelimiter。其特色就是使用装饰者模式，可以多个功能组合在一起。其他的话，timelimiter的使用比起hystrix稍微费劲些。

doc

• Fault tolerance library designed for functional programming