Eureka Client源码解析回顾

Dear 丶 2023-01-07 10:05 200阅读 0赞

## 一 概述 ##

**Eureka Client通过Starter的方式引入依赖，Spring Boot将会为项目使不同的注解进行自动配置。**

*  EurekaClientAutoConfiguration：Eureka Client自动配置类，负责Eureka Client中关键Beans的配置和初始化，如ApplicationInfoManager和EurekaClientConfig等。
 *  RibbonEurekaAutoConfiguration：Ribbon负载均衡相关配置。
 *  EurekaDiscoveryClientConfiguratino：配置自动注册和应用的健康检查器。

## 二 Eureka Client的完整工作流程 ##

**应用启动阶段**

1.  **读取与Eureka Server交互的配置信息，封装成EurekaClientConfig。**
2.  **读取自身服务实例配置信息，封装成EurekaInstanceConfig。**
3.  **从Eureka Server中拉取注册表信息并缓存到本地。**
4.  **服务注册。**
5.  **初始化发送心跳，缓存刷新(拉取注册表信息更新本地缓存)和按需注册(监控服务实例信息变化，决定是否重新发起注册，更新注册表中的服务实例元数据）定时任务。**

**应用执行阶段**

1.  **定时发送心跳到Eureka Server中，维持在注册表的租约**。
2.  **定时从Eureka Server中拉取注册表信息，更新本地注册表缓存。**
3.  **监控一个用自身信息变化，若发生变化，需要重新发起服务注册。**

**应用销毁阶段**

1.  **从Eureka Server注销自身服务实例。**

## **三 配置类EurekaDiscoveryClientConfiguration** ##

**源码**

@Configuration(proxyBeanMethods = false)
    @EnableConfigurationProperties
    @ConditionalOnClass(EurekaClientConfig.class)
    @ConditionalOnProperty(value = "eureka.client.enabled", matchIfMissing = true)
    @ConditionalOnDiscoveryEnabled
    @ConditionalOnBlockingDiscoveryEnabled
    public class EurekaDiscoveryClientConfiguration {
    
    	@Bean
    	@ConditionalOnMissingBean
    	public EurekaDiscoveryClient discoveryClient(EurekaClient client, EurekaClientConfig clientConfig) {
    		return new EurekaDiscoveryClient(client, clientConfig);
    	}
    
    	@Configuration(proxyBeanMethods = false)
    	@ConditionalOnProperty(value = "eureka.client.healthcheck.enabled", matchIfMissing = false)
    	protected static class EurekaHealthCheckHandlerConfiguration {
    
    		@Autowired(required = false)
    		private StatusAggregator statusAggregator = new SimpleStatusAggregator();
    
    		@Bean
    		@ConditionalOnMissingBean(HealthCheckHandler.class)
    		public EurekaHealthCheckHandler eurekaHealthCheckHandler() {
    			return new EurekaHealthCheckHandler(this.statusAggregator);
    		}
    	}
    
    	@Configuration(proxyBeanMethods = false)
    	@ConditionalOnClass(RefreshScopeRefreshedEvent.class)
    	protected static class EurekaClientConfigurationRefresher
    			implements ApplicationListener<RefreshScopeRefreshedEvent> {
    
    		@Autowired(required = false)
    		private EurekaClient eurekaClient;
    
    		@Autowired(required = false)
    		private EurekaAutoServiceRegistration autoRegistration;
    
    		public void onApplicationEvent(RefreshScopeRefreshedEvent event) {
    			// This will force the creation of the EurkaClient bean if not already created
    			// to make sure the client will be reregistered after a refresh event
    			if (eurekaClient != null) {
    				eurekaClient.getApplications();
    			}
    			if (autoRegistration != null) {
    				// register in case meta data changed
    				this.autoRegistration.stop();
    				this.autoRegistration.start();
    			}
    		}
    	}
    }

**EurekaDiscoveryClientConfiguration中属性读取和配置类**

<table> 
 <tbody> 
  <tr> 
   <td>类名</td> 
   <td>作用和介绍</td> 
  </tr> 
  <tr> 
   <td>EurekaClientConfig</td> 
   <td>封装Eureka Client与Eureka Server交互所需要的配置信息。Spring Cloud为其提供了一个默认配置Eureka的配置类EurekaClientConfigBean，可以在配置文件中通过前缀eureka.client + 属性名进行属性覆盖。</td> 
  </tr> 
  <tr> 
   <td>ApplicationInfoManager</td> 
   <td>作为应用信息管理，管理服务实例的信息类InstanceInfo和服务实例的配置信息类EurekaInstanceConfig。</td> 
  </tr> 
  <tr> 
   <td>InstanceInfo</td> 
   <td>封装将被发送到Eureka Server进行服务注册和服务实例元数据。它在Eureka Server的注册表中代表一个服务实例，其他服务实例可以通过InstanceInfo了解该服务实例的相关信息从而发起服务请求。</td> 
  </tr> 
  <tr> 
   <td>EurekaInstanceConfig</td> 
   <td>封装Eureka Client自身服务实例的配置信息，主要用于构建InstanceInfo，通常这些信息在配置文件中的eureka.instance前缀下进行设置，Spring Cloud通过EurekaInstanceConfigBean配置类提供了默认配置。</td> 
  </tr> 
  <tr> 
   <td>DiscoveryClient</td> 
   <td>Spring Cloud中定义用来服务发现的客户端接口。</td> 
  </tr> 
 </tbody> 
</table>

**默认配置类EurekaClientConfigBean的部分信息源码**

@ConfigurationProperties(EurekaClientConfigBean.PREFIX)
    public class EurekaClientConfigBean implements EurekaClientConfig, Ordered {
    
    	public static final String PREFIX = "eureka.client";
    
    	public static final String DEFAULT_URL = "http://localhost:8761" + DEFAULT_PREFIX + "/";
    
    	public static final String DEFAULT_ZONE = "defaultZone";
    
    	private static final int MINUTES = 60;
    
    	@Autowired(required = false)
    	PropertyResolver propertyResolver;
    
    	private boolean enabled = true;
    
    	@NestedConfigurationProperty
    	private EurekaTransportConfig transport = new CloudEurekaTransportConfig();
    
    	private int registryFetchIntervalSeconds = 30;
    
    	private int instanceInfoReplicationIntervalSeconds = 30;
    
    	private int initialInstanceInfoReplicationIntervalSeconds = 40;
    
    	private int eurekaServiceUrlPollIntervalSeconds = 5 * MINUTES;
    
    	private String proxyPort;
    
    	private String proxyHost;
    
    	private String proxyUserName;
    
    	private String proxyPassword;
    
    	private int eurekaServerReadTimeoutSeconds = 8;
    
    	private int eurekaServerConnectTimeoutSeconds = 5;
    
    	private String backupRegistryImpl;
    
    	private int eurekaServerTotalConnections = 200;
    
    	private int eurekaServerTotalConnectionsPerHost = 50;
    
    	private String eurekaServerURLContext;
    
    	private String eurekaServerPort;
    
    	private String eurekaServerDNSName;
    
    	private String region = "us-east-1";
    
    	private int eurekaConnectionIdleTimeoutSeconds = 30;
    
    	private String registryRefreshSingleVipAddress;
    
    	private int heartbeatExecutorThreadPoolSize = 2;
    
    	private int heartbeatExecutorExponentialBackOffBound = 10;
    
    	private int cacheRefreshExecutorThreadPoolSize = 2;
    
    	private int cacheRefreshExecutorExponentialBackOffBound = 10;
    
    	private Map<String, String> serviceUrl = new HashMap<>();
    
    	{
    		this.serviceUrl.put(DEFAULT_ZONE, DEFAULT_URL);
    	}
    
    	private boolean gZipContent = true;
    
    	private boolean useDnsForFetchingServiceUrls = false;
    
    	private boolean registerWithEureka = true;
    
    	private boolean preferSameZoneEureka = true;
    
    	private boolean logDeltaDiff;
    
    	private boolean disableDelta;
    
    	private String fetchRemoteRegionsRegistry;
    
    	private Map<String, String> availabilityZones = new HashMap<>();
    
    	private boolean filterOnlyUpInstances = true;
    
    	private boolean fetchRegistry = true;
    
    	private String dollarReplacement = "_-";
    
    	private String escapeCharReplacement = "__";
    
    	private boolean allowRedirects = false;
    
    	private boolean onDemandUpdateStatusChange = true;
    
    	private String encoderName;
    
    	private String decoderName;
    
    	private String clientDataAccept = EurekaAccept.full.name();
    
    	private boolean shouldUnregisterOnShutdown = true;
    
    	private boolean shouldEnforceRegistrationAtInit = false;
    
    	private int order = 0;
    }

继续复习总结中，待续！