服務治理-Resilience4j（限流）

Bulkhead

Bulkhead一般用於服務調用客戶端，用於限定對特定的服務的併發請求數量，起到一下作用：
1、防⽌下游依賴被併發請求衝擊
2、防⽌發⽣連環故障

1、配置規則“order”

//允許最大的併發數量
resilience4j.bulkhead.backends.order.max-concurrent-call=1
//阻塞線程的最大時間量
resilience4j.bulkhead.backends.order.max-wait-time=5

2、註解方式使用

@PostMapping("/order")
    @io.github.resilience4j.circuitbreaker.annotation.CircuitBreaker(name = "order")
    @io.github.resilience4j.bulkhead.annotation.Bulkhead(name = "order")
    public CoffeeOrder createOrder() {
        NewOrderRequest orderRequest = NewOrderRequest.builder()
                .customer("Li Lei")
                .items(Arrays.asList("capuccino"))
                .build();
        CoffeeOrder order = coffeeOrderService.create(orderRequest);
        log.info("Order ID: {}", order != null ? order.getId() : "-");
        return order;
    }

3、使用配置註冊方式

        private CircuitBreaker circuitBreaker;
    private Bulkhead bulkhead;

      //構造方法
    public CustomerController(CircuitBreakerRegistry circuitBreakerRegistry,
                              BulkheadRegistry bulkheadRegistry) {
        circuitBreaker = circuitBreakerRegistry.circuitBreaker("order");
        bulkhead = bulkheadRegistry.bulkhead("order");
    }

    @GetMapping("/menu")
    public List<Coffee> readMenu() {
        return Try.ofSupplier(
                Bulkhead.decorateSupplier(bulkhead,
                        CircuitBreaker.decorateSupplier(circuitBreaker,
                                () -> coffeeService.getAll())))
                .recover(CircuitBreakerOpenException.class, Collections.emptyList())
                .recover(BulkheadFullException.class, Collections.emptyList())
                .get();
    }

RateLimiter

RateLimiter用於限制特定時間段內的執⾏次數，一般用於服務提供方，保護自己不受到衝擊。

1、配置限流策略-“order”

//一個限制週期內可訪問次數
resilience4j.ratelimiter.limiters.order.limit-for-period=3
//限制週期,每個週期之後，速率限制器將重置回limitForPeriod值
resilience4j.ratelimiter.limiters.order.limit-refresh-period-in-millis=30000
//線程等待允許執行時間
resilience4j.ratelimiter.limiters.order.timeout-in-millis=1000
//開啓時間訂閱
resilience4j.ratelimiter.limiters.order.subscribe-for-events=true
//開啓監控監控
resilience4j.ratelimiter.limiters.order.register-health-indicator=true

2、使用註解方式

@PostMapping(path = "/", consumes = MediaType.APPLICATION_JSON_VALUE,
            produces = MediaType.APPLICATION_JSON_UTF8_VALUE)
    @ResponseStatus(HttpStatus.CREATED)
    @io.github.resilience4j.ratelimiter.annotation.RateLimiter(name = "order")
    public CoffeeOrder create(@RequestBody NewOrderRequest newOrder) {
        log.info("Receive new Order {}", newOrder);
        Coffee[] coffeeList = coffeeService.getCoffeeByName(newOrder.getItems())
                .toArray(new Coffee[]{});
        return orderService.createOrder(newOrder.getCustomer(), coffeeList);
    }

3、使用配置註冊方式

    private RateLimiter rateLimiter;
    //構造方法
    public CoffeeOrderController(RateLimiterRegistry rateLimiterRegistry) {
        rateLimiter = rateLimiterRegistry.rateLimiter("order");
    }

    @GetMapping("/{id}")
    public CoffeeOrder getOrder(@PathVariable("id") Long id) {
        CoffeeOrder order = null;
        try {
            order = rateLimiter.executeSupplier(() -> orderService.get(id));
            log.info("Get Order: {}", order);
        } catch (RequestNotPermitted e) {
            log.warn("Request Not Permitted! {}", e.getMessage());
        }
        return order;
    }