Spring Netflix Hystrix 请求合并

在默认情况下，每次请求会占用一次线程和一次网络请求，在高并发的场景下效率不高，Hystrix请求合并就是将多个请求合并为一个请求，提高服务并发能力，适用场景，单个对象的查询并发数很高，服务提供方负载比较大的时候。

两种实现方式：

1.编码

/**
 * <h1>请求合并器</h1>
 * */
@Slf4j
public class NacosClientCollapseCommand
        extends HystrixCollapser<List<List<ServiceInstance>>, List<ServiceInstance>, String> {

    private final NacosClientService nacosClientService;
    private final String serviceId;

    public NacosClientCollapseCommand(NacosClientService nacosClientService, String serviceId) {

        super(
                HystrixCollapser.Setter.withCollapserKey(
                        HystrixCollapserKey.Factory.asKey("NacosClientCollapseCommand")
                ).andCollapserPropertiesDefaults(
                        HystrixCollapserProperties.Setter().withTimerDelayInMilliseconds(300)
                )
        );

        this.nacosClientService = nacosClientService;
        this.serviceId = serviceId;
    }

    /**
     * <h2>获取请求中的参数</h2>
     * */
    @Override
    public String getRequestArgument() {
        return this.serviceId;
    }

    /**
     * <h2>创建批量请求 Hystrix Command</h2>
     * */
    @Override
    protected HystrixCommand<List<List<ServiceInstance>>> createCommand(
            Collection<CollapsedRequest<List<ServiceInstance>, String>> collapsedRequests) {

        List<String> serviceIds = new ArrayList<>(collapsedRequests.size());
        serviceIds.addAll(
                collapsedRequests.stream()
                        .map(CollapsedRequest::getArgument)
                        .collect(Collectors.toList())
        );

        return new NacosClientBatchCommand(nacosClientService, serviceIds);
    }

    /**
     * <h2>响应分发给单独的请求</h2>
     * */
    @Override
    protected void mapResponseToRequests(List<List<ServiceInstance>> batchResponse,
                                         Collection<CollapsedRequest<List<ServiceInstance>,
                                                 String>> collapsedRequests) {

        int count = 0;

        for (CollapsedRequest<List<ServiceInstance>, String> collapsedRequest : collapsedRequests) {

            // 从批量响应集合中按顺序取出结果
            List<ServiceInstance> instances = batchResponse.get(count++);
            // 将结果返回原 Response 中
            collapsedRequest.setResponse(instances);
        }
    }
}

/**
 * <h1>批量请求 Hystrix Command</h1>
 * */
@Slf4j
public class NacosClientBatchCommand extends HystrixCommand<List<List<ServiceInstance>>> {

    private final NacosClientService nacosClientService;
    private final List<String> serviceIds;

    protected NacosClientBatchCommand(
            NacosClientService nacosClientService, List<String> serviceIds
    ) {

        super(
                HystrixCommand.Setter.withGroupKey(
                        HystrixCommandGroupKey.Factory.asKey("NacosClientBatchCommand")
                )
        );

        this.nacosClientService = nacosClientService;
        this.serviceIds = serviceIds;
    }

    @Override
    protected List<List<ServiceInstance>> run() throws Exception {

        log.info("use nacos client batch command to get result: [{}]",
                JSON.toJSONString(serviceIds));
        return nacosClientService.getNacosClientInfos(serviceIds);
    }

    @Override
    protected List<List<ServiceInstance>> getFallback() {

        log.warn("nacos client batch command failure, use fallback");
        return Collections.emptyList();
    }
}

2.注解

// 使用注解实现 Hystrix 请求合并

    @HystrixCollapser(
            batchMethod = "findNacosClientInfos",
            scope = com.netflix.hystrix.HystrixCollapser.Scope.GLOBAL,
            collapserProperties = {
                    @HystrixProperty(name = "timerDelayInMilliseconds", value = "300")
            }
    )
    public Future<List<ServiceInstance>> findNacosClientInfo(String serviceId) {

        // 系统运行正常, 不会走这个方法
        throw new RuntimeException("This method body should not be executed!");
    }

    @HystrixCommand
    public List<List<ServiceInstance>> findNacosClientInfos(List<String> serviceIds) {

        log.info("coming in find nacos client infos: [{}]", JSON.toJSONString(serviceIds));
        return getNacosClientInfos(serviceIds);
    }

 /**
     * <h2>注解的方式实现请求合并</h2>
     * */
    @GetMapping("/request-merge-annotation")
    public void requestMergeAnnotation() throws Exception {

        Future<List<ServiceInstance>> future01 = nacosClientService.findNacosClientInfo(
                "e-commerce-nacos-client1"
        );
        Future<List<ServiceInstance>> future02 = nacosClientService.findNacosClientInfo(
                "e-commerce-nacos-client2"
        );
        Future<List<ServiceInstance>> future03 = nacosClientService.findNacosClientInfo(
                "e-commerce-nacos-client3"
        );

        future01.get();
        future02.get();
        future03.get();

        Thread.sleep(2000);

        Future<List<ServiceInstance>> future04 = nacosClientService.findNacosClientInfo(
                "e-commerce-nacos-client4"
        );
        future04.get();
    }