nacos——01

nacos starter

pom依赖

<!-- nacos starter -->
<dependency>
  <groupId>com.alibaba.cloud</groupId>
  <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
  <version>2021.0.4.0-SNAPSHOT</version>
</dependency>

spring.factories

这里主要看  ​​NacosServiceRegistryAutoConfiguration、NacosDiscoveryClientConfiguration、LoadBalancerNacosAutoConfiguration​​

​​NacosServiceRegistryAutoConfiguration​​

Spring Cloud Commons 中通过三个接口，定义了实现注册中心的一套规范，这三接口在 org.springframework.cloud.client.serviceregistry 下

• AutoServiceRegistration 负责服务自动注册
• Registration 用于存储服务信息,规范注册到注册中心的信息
• ServiceRegistry 定义服务注册接口，用来向注册中心注册服务

nacos分别有对应的具体实现类，就是 NacosServiceRegistryAutoConfiguration 中 @Bean 注解的那三个类

package com.alibaba.cloud.nacos.registry;
/**
 * Spring Cloud Commons 中通过三个接口，定义了实现注册中心的一套规范
 * org.springframework.cloud.client.serviceregistry
 * AutoServiceRegistration 服务自动注册
 * Registration 存储服务信息,规范注册到注册中心的信息
 * ServiceRegistry 服务注册接口，用来向注册中心注册服务
 */
@Configuration(proxyBeanMethods = false)
@EnableConfigurationProperties
@ConditionalOnNacosDiscoveryEnabled
@ConditionalOnProperty(value = "spring.cloud.service-registry.auto-registration.enabled",
  matchIfMissing = true)
@AutoConfigureAfter({ AutoServiceRegistrationConfiguration.class,
  AutoServiceRegistrationAutoConfiguration.class,
  NacosDiscoveryAutoConfiguration.class })
public class NacosServiceRegistryAutoConfiguration {
  /**
  * 向注册中心注册服务
  */
  @Bean
  public NacosServiceRegistry nacosServiceRegistry(
    NacosServiceManager nacosServiceManager,
    NacosDiscoveryProperties nacosDiscoveryProperties) {
  return new NacosServiceRegistry(nacosServiceManager, nacosDiscoveryProperties);
  }

  /**
  * 规范注册到注册中心的信息
  */
  @Bean
  @ConditionalOnBean(AutoServiceRegistrationProperties.class)
  public NacosRegistration nacosRegistration(
    ObjectProvider<List<NacosRegistrationCustomizer>> registrationCustomizers,
    NacosDiscoveryProperties nacosDiscoveryProperties,
    ApplicationContext context) {
  return new NacosRegistration(registrationCustomizers.getIfAvailable(),
    nacosDiscoveryProperties, context);
  }

  /**
  * 服务启动后自动注册到注册中心
  * 继承 AbstractAutoServiceRegistration，
  * 
  * 
  */
  @Bean
  @ConditionalOnBean(AutoServiceRegistrationProperties.class)
  public NacosAutoServiceRegistration nacosAutoServiceRegistration(
    NacosServiceRegistry registry,
    AutoServiceRegistrationProperties autoServiceRegistrationProperties,
    NacosRegistration registration) {
  return new NacosAutoServiceRegistration(registry,
    autoServiceRegistrationProperties, registration);
  }

}

​​NacosAutoServiceRegistration​​

package com.alibaba.cloud.nacos.registry;
/**
 * 服务启动后自动注册到注册中心
 */
public class NacosAutoServiceRegistration
    extends AbstractAutoServiceRegistration<Registration> {

  private static final Logger log = LoggerFactory
      .getLogger(NacosAutoServiceRegistration.class);

  private NacosRegistration registration;

  public NacosAutoServiceRegistration(ServiceRegistry<Registration> serviceRegistry,
      AutoServiceRegistrationProperties autoServiceRegistrationProperties,
      NacosRegistration registration) {
    super(serviceRegistry, autoServiceRegistrationProperties);
    this.registration = registration;
  }

  @Override
  protected NacosRegistration getRegistration() {
    if (this.registration.getPort() < 0 && this.getPort().get() > 0) {
      this.registration.setPort(this.getPort().get());
    }
    Assert.isTrue(this.registration.getPort() > 0, "service.port has not been set");
    return this.registration;
  }

  @Override
  protected NacosRegistration getManagementRegistration() {
    return null;
  }
  /**
   * 注册，最终调用父类中注册方法
   */
  @Override
  protected void register() {
    if (!this.registration.getNacosDiscoveryProperties().isRegisterEnabled()) {
      log.debug("Registration disabled.");
      return;
    }
    if (this.registration.getPort() < 0) {
      this.registration.setPort(getPort().get());
    }
    super.register();
  }

  /**
   * 
   */
  @Override
  protected void registerManagement() {
    if (!this.registration.getNacosDiscoveryProperties().isRegisterEnabled()) {
      return;
    }
    super.registerManagement();

  }

  @Override
  protected Object getConfiguration() {
    return this.registration.getNacosDiscoveryProperties();
  }

  @Override
  protected boolean isEnabled() {
    return this.registration.getNacosDiscoveryProperties().isRegisterEnabled();
  }

  @Override
  @SuppressWarnings("deprecation")
  protected String getAppName() {
    String appName = registration.getNacosDiscoveryProperties().getService();
    return StringUtils.isEmpty(appName) ? super.getAppName() : appName;
  }

  @EventListener
  public void onNacosDiscoveryInfoChangedEvent(NacosDiscoveryInfoChangedEvent event) {
    restart();
  }

  private void restart() {
    this.stop();
    this.start();
  }

}

具体自动注册流程如下

​​NacosRegistration​​

package com.alibaba.cloud.nacos.registry;

/**
 * Registration 是一个空接口没有任何方法
 * ServiceInstance 中定义了服务实例的各种方法
 * 主要是通过 @PostConstruct 注解的 init 方法，初始化后调用
 */
public class NacosRegistration implements Registration, ServiceInstance {

   /**
    * The metadata key of management port.
    */
   public static final String MANAGEMENT_PORT = "management.port";

   /**
    * The metadata key of management context-path.
    */
   public static final String MANAGEMENT_CONTEXT_PATH = "management.context-path";

   /**
    * The metadata key of management address.
    */
   public static final String MANAGEMENT_ADDRESS = "management.address";

   /**
    * The metadata key of management endpoints web base path.
    */
   public static final String MANAGEMENT_ENDPOINT_BASE_PATH = "management.endpoints.web.base-path";

   private List<NacosRegistrationCustomizer> registrationCustomizers;

   private NacosDiscoveryProperties nacosDiscoveryProperties;

   private ApplicationContext context;

   public NacosRegistration(List<NacosRegistrationCustomizer> registrationCustomizers,
         NacosDiscoveryProperties nacosDiscoveryProperties,
         ApplicationContext context) {
      this.registrationCustomizers = registrationCustomizers;
      this.nacosDiscoveryProperties = nacosDiscoveryProperties;
      this.context = context;
   }

   @PostConstruct
   public void init() {

      Map<String, String> metadata = nacosDiscoveryProperties.getMetadata();
      Environment env = context.getEnvironment();

      String endpointBasePath = env.getProperty(MANAGEMENT_ENDPOINT_BASE_PATH);
      if (StringUtils.hasLength(endpointBasePath)) {
         metadata.put(MANAGEMENT_ENDPOINT_BASE_PATH, endpointBasePath);
      }

      Integer managementPort = ManagementServerPortUtils.getPort(context);
      if (null != managementPort) {
         metadata.put(MANAGEMENT_PORT, managementPort.toString());
         String contextPath = env
               .getProperty("management.server.servlet.context-path");
         String address = env.getProperty("management.server.address");
         if (StringUtils.hasLength(contextPath)) {
            metadata.put(MANAGEMENT_CONTEXT_PATH, contextPath);
         }
         if (StringUtils.hasLength(address)) {
            metadata.put(MANAGEMENT_ADDRESS, address);
         }
      }

      if (null != nacosDiscoveryProperties.getHeartBeatInterval()) {
         metadata.put(PreservedMetadataKeys.HEART_BEAT_INTERVAL,
               nacosDiscoveryProperties.getHeartBeatInterval().toString());
      }
      if (null != nacosDiscoveryProperties.getHeartBeatTimeout()) {
         metadata.put(PreservedMetadataKeys.HEART_BEAT_TIMEOUT,
               nacosDiscoveryProperties.getHeartBeatTimeout().toString());
      }
      if (null != nacosDiscoveryProperties.getIpDeleteTimeout()) {
         metadata.put(PreservedMetadataKeys.IP_DELETE_TIMEOUT,
               nacosDiscoveryProperties.getIpDeleteTimeout().toString());
      }
      customize(registrationCustomizers);
   }
    /**
     * 这里可以实现 NacosRegistrationCustomizer 来实现定制化
     */   
   protected void customize(
         List<NacosRegistrationCustomizer> registrationCustomizers) {
      if (registrationCustomizers != null) {
         for (NacosRegistrationCustomizer customizer : registrationCustomizers) {
            customizer.customize(this);
         }
      }
   }

   @Override
   public String getServiceId() {
      return nacosDiscoveryProperties.getService();
   }

   @Override
   public String getHost() {
      return nacosDiscoveryProperties.getIp();
   }

   @Override
   public int getPort() {
      return nacosDiscoveryProperties.getPort();
   }

   public void setPort(int port) {
      this.nacosDiscoveryProperties.setPort(port);
   }

   @Override
   public boolean isSecure() {
      return nacosDiscoveryProperties.isSecure();
   }

   @Override
   public URI getUri() {
      return DefaultServiceInstance.getUri(this);
   }

   @Override
   public Map<String, String> getMetadata() {
      return nacosDiscoveryProperties.getMetadata();
   }

   public boolean isRegisterEnabled() {
      return nacosDiscoveryProperties.isRegisterEnabled();
   }

   public String getCluster() {
      return nacosDiscoveryProperties.getClusterName();
   }

   public float getRegisterWeight() {
      return nacosDiscoveryProperties.getWeight();
   }

   public NacosDiscoveryProperties getNacosDiscoveryProperties() {
      return nacosDiscoveryProperties;
   }

   @Override
   public String toString() {
      return "NacosRegistration{" + "nacosDiscoveryProperties="
            + nacosDiscoveryProperties + '}';
   }

}

​​NacosServiceRegistry​​

package com.alibaba.cloud.nacos.registry;

/**
 * 向注册中心注册/反注册服务，设置/获取服务状态，关闭服务
 * ServiceRegistry 中定义了注册、注销、关闭、设置服务状态、获取服务状态
 */
public class NacosServiceRegistry implements ServiceRegistry<Registration> {

   private static final String STATUS_UP = "UP";

   private static final String STATUS_DOWN = "DOWN";

   private static final Logger log = LoggerFactory.getLogger(NacosServiceRegistry.class);

   private final NacosDiscoveryProperties nacosDiscoveryProperties;

   private final NacosServiceManager nacosServiceManager;

   public NacosServiceRegistry(NacosServiceManager nacosServiceManager,
         NacosDiscoveryProperties nacosDiscoveryProperties) {
      this.nacosDiscoveryProperties = nacosDiscoveryProperties;
      this.nacosServiceManager = nacosServiceManager;
   }

   @Override
   public void register(Registration registration) {

      if (StringUtils.isEmpty(registration.getServiceId())) {
         log.warn("No service to register for nacos client...");
         return;
      }

      NamingService namingService = namingService();
      String serviceId = registration.getServiceId();
      String group = nacosDiscoveryProperties.getGroup();

      Instance instance = getNacosInstanceFromRegistration(registration);

      try {
         namingService.registerInstance(serviceId, group, instance);
         log.info("nacos registry, {} {} {}:{} register finished", group, serviceId,
               instance.getIp(), instance.getPort());
      }
      catch (Exception e) {
         if (nacosDiscoveryProperties.isFailFast()) {
            log.error("nacos registry, {} register failed...{},", serviceId,
                  registration.toString(), e);
            rethrowRuntimeException(e);
         }
         else {
            log.warn("Failfast is false. {} register failed...{},", serviceId,
                  registration.toString(), e);
         }
      }
   }

   @Override
   public void deregister(Registration registration) {

      log.info("De-registering from Nacos Server now...");

      if (StringUtils.isEmpty(registration.getServiceId())) {
         log.warn("No dom to de-register for nacos client...");
         return;
      }

      NamingService namingService = namingService();
      String serviceId = registration.getServiceId();
      String group = nacosDiscoveryProperties.getGroup();

      try {
         namingService.deregisterInstance(serviceId, group, registration.getHost(),
               registration.getPort(), nacosDiscoveryProperties.getClusterName());
      }
      catch (Exception e) {
         log.error("ERR_NACOS_DEREGISTER, de-register failed...{},",
               registration.toString(), e);
      }

      log.info("De-registration finished.");
   }

   @Override
   public void close() {
      try {
         nacosServiceManager.nacosServiceShutDown();
      }
      catch (NacosException e) {
         log.error("Nacos namingService shutDown failed", e);
      }
   }

   @Override
   public void setStatus(Registration registration, String status) {

      if (!STATUS_UP.equalsIgnoreCase(status)
            && !STATUS_DOWN.equalsIgnoreCase(status)) {
         log.warn("can't support status {},please choose UP or DOWN", status);
         return;
      }

      String serviceId = registration.getServiceId();

      Instance instance = getNacosInstanceFromRegistration(registration);

      if (STATUS_DOWN.equalsIgnoreCase(status)) {
         instance.setEnabled(false);
      }
      else {
         instance.setEnabled(true);
      }

      try {
         Properties nacosProperties = nacosDiscoveryProperties.getNacosProperties();
         nacosServiceManager.getNamingMaintainService(nacosProperties).updateInstance(
               serviceId, nacosDiscoveryProperties.getGroup(), instance);
      }
      catch (Exception e) {
         throw new RuntimeException("update nacos instance status fail", e);
      }

   }

   @Override
   public Object getStatus(Registration registration) {

      String serviceName = registration.getServiceId();
      String group = nacosDiscoveryProperties.getGroup();
      try {
         List<Instance> instances = namingService().getAllInstances(serviceName,
               group);
         for (Instance instance : instances) {
            if (instance.getIp().equalsIgnoreCase(nacosDiscoveryProperties.getIp())
                  && instance.getPort() == nacosDiscoveryProperties.getPort()) {
               return instance.isEnabled() ? "UP" : "DOWN";
            }
         }
      }
      catch (Exception e) {
         log.error("get all instance of {} error,", serviceName, e);
      }
      return null;
   }

   private Instance getNacosInstanceFromRegistration(Registration registration) {
      Instance instance = new Instance();
      instance.setIp(registration.getHost());
      instance.setPort(registration.getPort());
      instance.setWeight(nacosDiscoveryProperties.getWeight());
      instance.setClusterName(nacosDiscoveryProperties.getClusterName());
      instance.setEnabled(nacosDiscoveryProperties.isInstanceEnabled());
      instance.setMetadata(registration.getMetadata());
      instance.setEphemeral(nacosDiscoveryProperties.isEphemeral());
      return instance;
   }

   private NamingService namingService() {
      return nacosServiceManager.getNamingService();
   }

}

客户端服务发现流程

​​NacosDiscoveryClientConfiguration​​

package com.alibaba.cloud.nacos.discovery;

/**
 * 注意这里 DiscoveryClient 的子类 NacosDiscoveryClient，用于服务发现
 * 依赖入参为 NacosServiceDiscovery
 * @author xiaojing
 * @author echooymxq
 */
@Configuration(proxyBeanMethods = false)
@ConditionalOnDiscoveryEnabled
@ConditionalOnBlockingDiscoveryEnabled
@ConditionalOnNacosDiscoveryEnabled
@AutoConfigureBefore({ SimpleDiscoveryClientAutoConfiguration.class,
      CommonsClientAutoConfiguration.class })
@AutoConfigureAfter(NacosDiscoveryAutoConfiguration.class)
public class NacosDiscoveryClientConfiguration {

   @Bean
   public DiscoveryClient nacosDiscoveryClient(
         NacosServiceDiscovery nacosServiceDiscovery) {
      return new NacosDiscoveryClient(nacosServiceDiscovery);
   }

   @Bean
   @ConditionalOnMissingBean
   @ConditionalOnProperty(value = "spring.cloud.nacos.discovery.watch.enabled", matchIfMissing = true)
   public NacosWatch nacosWatch(NacosServiceManager nacosServiceManager,
         NacosDiscoveryProperties nacosDiscoveryProperties) {
      return new NacosWatch(nacosServiceManager, nacosDiscoveryProperties);
   }

}

​​NacosServiceDiscovery​​

package com.alibaba.cloud.nacos.discovery;
/**
 * 两个重要方法 getServices、getInstances
 * 前者从nacos获取服务，后者获取服务下实例集合
 **/
public class NacosServiceDiscovery {

  private NacosDiscoveryProperties discoveryProperties;

  private NacosServiceManager nacosServiceManager;

  public NacosServiceDiscovery(NacosDiscoveryProperties discoveryProperties,
      NacosServiceManager nacosServiceManager) {
    this.discoveryProperties = discoveryProperties;
    this.nacosServiceManager = nacosServiceManager;
  }

  /**
   * Return all instances for the given service.
   * @param serviceId id of service
   * @return list of instances
   * @throws NacosException nacosException
   */
  public List<ServiceInstance> getInstances(String serviceId) throws NacosException {
    String group = discoveryProperties.getGroup();
    List<Instance> instances = namingService().selectInstances(serviceId, group,
        true);
    return hostToServiceInstanceList(instances, serviceId);
  }

  /**
   * Return the names of all services.
   * @return list of service names
   * @throws NacosException nacosException
   */
  public List<String> getServices() throws NacosException {
    String group = discoveryProperties.getGroup();
    ListView<String> services = namingService().getServicesOfServer(1,
        Integer.MAX_VALUE, group);
    return services.getData();
  }

  public static List<ServiceInstance> hostToServiceInstanceList(
      List<Instance> instances, String serviceId) {
    List<ServiceInstance> result = new ArrayList<>(instances.size());
    for (Instance instance : instances) {
      ServiceInstance serviceInstance = hostToServiceInstance(instance, serviceId);
      if (serviceInstance != null) {
        result.add(serviceInstance);
      }
    }
    return result;
  }

  public static ServiceInstance hostToServiceInstance(Instance instance,
      String serviceId) {
    if (instance == null || !instance.isEnabled() || !instance.isHealthy()) {
      return null;
    }
    NacosServiceInstance nacosServiceInstance = new NacosServiceInstance();
    nacosServiceInstance.setHost(instance.getIp());
    nacosServiceInstance.setPort(instance.getPort());
    nacosServiceInstance.setServiceId(serviceId);
    nacosServiceInstance.setInstanceId(instance.getInstanceId());

    Map<String, String> metadata = new HashMap<>();
    metadata.put("nacos.instanceId", instance.getInstanceId());
    metadata.put("nacos.weight", instance.getWeight() + "");
    metadata.put("nacos.healthy", instance.isHealthy() + "");
    metadata.put("nacos.cluster", instance.getClusterName() + "");
    if (instance.getMetadata() != null) {
      metadata.putAll(instance.getMetadata());
    }
    metadata.put("nacos.ephemeral", String.valueOf(instance.isEphemeral()));
    nacosServiceInstance.setMetadata(metadata);

    if (metadata.containsKey("secure")) {
      boolean secure = Boolean.parseBoolean(metadata.get("secure"));
      nacosServiceInstance.setSecure(secure);
    }
    return nacosServiceInstance;
  }

  private NamingService namingService() {
    return nacosServiceManager.getNamingService();
  }

}

​​NacosDiscoveryClient​​

package com.alibaba.cloud.nacos.discovery;
/**
 * 实现 org.springframework.cloud.client.discovery.DiscoveryClient，客户端获取服务及对应实例
 * 主要这俩方法：getServices/getInstances ，内部均是调用上面 NacosServiceDiscovery 的对应方法
 */
public class NacosDiscoveryClient implements DiscoveryClient {
  /**
   * Nacos Discovery Client Description.
   */
  public static final String DESCRIPTION = "Spring Cloud Nacos Discovery Client";

  private NacosServiceDiscovery serviceDiscovery;

  @Value("${spring.cloud.nacos.discovery.failure-tolerance-enabled:false}")
  private boolean failureToleranceEnabled;

  public NacosDiscoveryClient(NacosServiceDiscovery nacosServiceDiscovery) {
    this.serviceDiscovery = nacosServiceDiscovery;
  }

  @Override
  public String description() {
    return DESCRIPTION;
  }

  @Override
  public List<ServiceInstance> getInstances(String serviceId) {
    try {
      return Optional.of(serviceDiscovery.getInstances(serviceId))
          .map(instances -> {
            ServiceCache.setInstances(serviceId, instances);
            return instances;
          }).get();
    }
    catch (Exception e) {
      if (failureToleranceEnabled) {
        return ServiceCache.getInstances(serviceId);
      }
      throw new RuntimeException(
          "Can not get hosts from nacos server. serviceId: " + serviceId, e);
    }
  }

  @Override
  public List<String> getServices() {
    try {
      return Optional.of(serviceDiscovery.getServices()).map(services -> {
        ServiceCache.setServiceIds(services);
        return services;
      }).get();
    }
    catch (Exception e) {
      log.error("get service name from nacos server failed.", e);
      return failureToleranceEnabled ? ServiceCache.getServiceIds()
          : Collections.emptyList();
    }
  }

}

​​LoadBalancerNacosAutoConfiguration​​

package com.alibaba.cloud.nacos.loadbalancer;
/**
 * 关键类是 NacosLoadBalancerClientConfiguration
 * {@link org.springframework.boot.autoconfigure.EnableAutoConfiguration
 * Auto-configuration} that sets up LoadBalancer for Nacos.
 */
@Configuration(proxyBeanMethods = false)
@EnableConfigurationProperties
@ConditionalOnLoadBalancerNacos
@ConditionalOnNacosDiscoveryEnabled
@LoadBalancerClients(defaultConfiguration = NacosLoadBalancerClientConfiguration.class)
public class LoadBalancerNacosAutoConfiguration {

}

​​NacosLoadBalancerClientConfiguration​​

package com.alibaba.cloud.nacos.loadbalancer;
/**
 * NacosLoadBalancer nacos负载均衡核心注解，被其修饰的 RestTempate 才会有负载均衡功能
 * 有两组配置：reactor及blocking，前者order优先级更高
 * ServiceInstanceListSupplier 提供符合条件的实例列表，类似工厂类，这里通过
 * ServiceInstanceListSupplierBuilder 这个final类的方法进行build，生成两组
 * 
 * DiscoveryClientServiceInstanceListSupplier 基于客户端发现
 * ZonePreferenceServiceInstanceListSupplier 按区域筛选委托检索的实例
 * {@link ServiceInstanceListSupplier} don't use cache.<br>
 * <br>
 * 1. LoadBalancerCache causes information such as the weight of the service instance to
 * be changed without immediate effect.<br>
 * 2. Nacos itself supports caching.
 */
@Configuration(proxyBeanMethods = false)
@ConditionalOnDiscoveryEnabled
public class NacosLoadBalancerClientConfiguration {

   private static final int REACTIVE_SERVICE_INSTANCE_SUPPLIER_ORDER = 183827465;

   @Bean
   @ConditionalOnMissingBean
   public ReactorLoadBalancer<ServiceInstance> nacosLoadBalancer(Environment environment,
         LoadBalancerClientFactory loadBalancerClientFactory,
         NacosDiscoveryProperties nacosDiscoveryProperties) {
      String name = environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME);
      return new NacosLoadBalancer(
            loadBalancerClientFactory.getLazyProvider(name,
                  ServiceInstanceListSupplier.class),
            name, nacosDiscoveryProperties);
   }

   @Configuration(proxyBeanMethods = false)
   @ConditionalOnReactiveDiscoveryEnabled
   @Order(REACTIVE_SERVICE_INSTANCE_SUPPLIER_ORDER)
   public static class ReactiveSupportConfiguration {

      @Bean
      @ConditionalOnBean(ReactiveDiscoveryClient.class)
      @ConditionalOnMissingBean
      @ConditionalOnProperty(value = "spring.cloud.loadbalancer.configurations", havingValue = "default", matchIfMissing = true)
      public ServiceInstanceListSupplier discoveryClientServiceInstanceListSupplier(
            ConfigurableApplicationContext context) {
         return ServiceInstanceListSupplier.builder().withDiscoveryClient()
               .build(context);
      }

      @Bean
      @ConditionalOnBean(ReactiveDiscoveryClient.class)
      @ConditionalOnMissingBean
      @ConditionalOnProperty(value = "spring.cloud.loadbalancer.configurations", havingValue = "zone-preference")
      public ServiceInstanceListSupplier zonePreferenceDiscoveryClientServiceInstanceListSupplier(
            ConfigurableApplicationContext context) {
         return ServiceInstanceListSupplier.builder().withDiscoveryClient()
               .withZonePreference().build(context);
      }

   }

   @Configuration(proxyBeanMethods = false)
   @ConditionalOnBlockingDiscoveryEnabled
   @Order(REACTIVE_SERVICE_INSTANCE_SUPPLIER_ORDER + 1)
   public static class BlockingSupportConfiguration {

      @Bean
      @ConditionalOnBean(DiscoveryClient.class)
      @ConditionalOnMissingBean
      @ConditionalOnProperty(value = "spring.cloud.loadbalancer.configurations", havingValue = "default", matchIfMissing = true)
      public ServiceInstanceListSupplier discoveryClientServiceInstanceListSupplier(
            ConfigurableApplicationContext context) {
         return ServiceInstanceListSupplier.builder().withBlockingDiscoveryClient()
               .build(context);
      }

      @Bean
      @ConditionalOnBean(DiscoveryClient.class)
      @ConditionalOnMissingBean
      @ConditionalOnProperty(value = "spring.cloud.loadbalancer.configurations", havingValue = "zone-preference")
      public ServiceInstanceListSupplier zonePreferenceDiscoveryClientServiceInstanceListSupplier(
            ConfigurableApplicationContext context) {
         return ServiceInstanceListSupplier.builder().withBlockingDiscoveryClient()
               .withZonePreference().build(context);
      }

   }

}