使用java框架构建分布式系统时如何确保高可用性

import java.time.Duration;

public class RetryableServiceClient {

    public static void main(String[] args) {
        // 创建一个重试器，最大重试次数为 5，重试间隔为 100 毫秒
        Retryer<String> retryer = RetryerBuilder.<String>newBuilder()
            .retryIfException()
            .withBackoffStrategy(ExponentialBackoffStrategy.of(Duration.ofMillis(100), 5))
            .build();

        // 执行可重试的调用，如果失败则重试
        String result = retryer.call(() -> invokeService());
        System.out.println("Service response: " + result);
    }

    private static String invokeService() {
        // 调用远程服务，可能会失败
        // ...
    }
}

import com.netflix.discovery.EurekaClient;
import com.netflix.discovery.shared.Application;
import com.netflix.discovery.shared.Applications;

public class EurekaDiscoveryClient {

    public static void main(String[] args) {
        // 创建 Eureka 客户端
        EurekaClient eurekaClient = EurekaClientFactory.create();

        // 获取所有可用的应用程序
        Applications applications = eurekaClient.getApplications();

        // 遍历应用程序并获取实际服务实例
        for (Application application : applications) {
            for (Instance instance : application.getInstances()) {
                System.out.println("Found service: " + instance.getHostName() + ":" + instance.getPort());
            }
        }
    }
}

import com.google.cloud.servicedirectory.v1.Endpoint;
import com.google.cloud.servicedirectory.v1.LookupServiceClient;
import com.google.cloud.servicedirectory.v1.ResolveServiceRequest;
import com.google.cloud.servicedirectory.v1.ResolveServiceResponse;

public class ServiceDirectoryLoadBalancing {

    public static void main(String[] args) {
        // 创建 Service Directory 客户端
        try (LookupServiceClient lookupServiceClient = LookupServiceClient.create()) {

            // 从 Service Directory 中解析服务
            ResolveServiceRequest request = ResolveServiceRequest.newBuilder()
                .setServiceName("my-service")
                .build();
            ResolveServiceResponse response = lookupServiceClient.resolveService(request);

            // 从解析的结果中选择一个服务实例
            Endpoint endpoint = chooseEndpoint(response.getEndpointsList());

            // 调用选定的服务实例
            // ...
        }
    }

    private static Endpoint chooseEndpoint(List<Endpoint> endpoints) {
        // 使用轮询或加权随机算法选择一个服务实例
        // ...
    }
}

import com.google.cloud.functions.BackgroundFunction;
import com.google.cloud.functions.Context;

public class AutoScalingFunction implements BackgroundFunction<Data> {

    @Override
    public void accept(Data data, Context context) {
        try {
            // 处理请求
            // ...
        } catch (Exception e) {
            // 如果处理失败，将事件置为死信，以便重新尝试
            context.setDeadLetterPolicy(DeadLetterPolicy.newBuilder()
                .setDestination("my-dead-letter-topic")
                .build());
        }
    }
}