Bulkhead

Bulkhead is generally used for service calling clients to limit the number of concurrent requests for a specific service. It has the following functions:
1. Prevent downstream dependency from being impacted by concurrent requests
2. Prevention of continuous failure

1. Configure rule "order"

//Maximum number of concurrent allowed
resilience4j.bulkhead.backends.order.max-concurrent-call=1
//Maximum amount of time to block a thread
resilience4j.bulkhead.backends.order.max-wait-time=5

2. Use of annotation

@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. Use configuration registration method

        private CircuitBreaker circuitBreaker;
    private Bulkhead bulkhead;

      //Construction method
    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 is used to limit the number of executions in a specific period of time. It is generally used by service providers to protect themselves from impact.

1. Configure current limiting strategy - "order"

//Access times in a limited period
resilience4j.ratelimiter.limiters.order.limit-for-period=3
//Limit period, after each period, the rate limiter will reset back to the limitForPeriod value
resilience4j.ratelimiter.limiters.order.limit-refresh-period-in-millis=30000
//Thread wait allowed execution time
resilience4j.ratelimiter.limiters.order.timeout-in-millis=1000
//Open time subscription
resilience4j.ratelimiter.limiters.order.subscribe-for-events=true
//Turn on monitoring
resilience4j.ratelimiter.limiters.order.register-health-indicator=true

2. Use annotation method

@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. Use configuration registration method

    private RateLimiter rateLimiter;
    //Construction method
    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;
    }