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地址 : https://mp.weixin.qq.com/s/FfJrAGQuHyVrsedtbr0Ihw
簡介
上一篇文章《Eureka 原始碼分析之 Eureka Client》 通過原始碼知道 ,eureka Client 是通過 http rest來 與 eureka server 互動,實現 註冊服務,續約服務,服務下線 等。本篇探究下eureka server。
原始碼分析
從 @EnableEurekaServer 註解為入口分析,通過原始碼可以看出他是一個標記註解:
/**
* Annotation to activate Eureka Server related configuration {@link
*/
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(EurekaServerMarkerConfiguration.class)
public @interface EnableEurekaServer {
}
從註釋可以知道,用來啟用 eureka server 的 配置類 EurekaServerAutoConfiguration 中相關配置,EurekaServerAutoConfiguration 的關鍵程式碼如下:
@Configuration
@Import(EurekaServerInitializerConfiguration.class)
@ConditionalOnBean(EurekaServerMarkerConfiguration.Marker.class)
@EnableConfigurationProperties({ EurekaDashboardProperties.class,
InstanceRegistryProperties.class })
@PropertySource("classpath:/eureka/server.properties")
public class EurekaServerAutoConfiguration extends WebMvcConfigurerAdapter {
/**
* List of packages containing Jersey resources required by the Eureka server
*/
private static final String[] EUREKA_PACKAGES = new String[] { "com.netflix.discovery",
"com.netflix.eureka" };
@Autowired
private ApplicationInfoManager applicationInfoManager;
@Autowired
private EurekaServerConfig eurekaServerConfig;
@Autowired
private EurekaClientConfig eurekaClientConfig;
@Autowired
private EurekaClient eurekaClient;
@Autowired
private InstanceRegistryProperties instanceRegistryProperties;
public static final CloudJacksonJson JACKSON_JSON = new CloudJacksonJson();
@Bean
public HasFeatures eurekaServerFeature() {
return HasFeatures.namedFeature("Eureka Server",
EurekaServerAutoConfiguration.class);
}
@Configuration
protected static class EurekaServerConfigBeanConfiguration {
// 建立並載入EurekaServerConfig的實現類,主要是Eureka-server的配置資訊
@Bean
@ConditionalOnMissingBean
public EurekaServerConfig eurekaServerConfig(EurekaClientConfig clientConfig) {
EurekaServerConfigBean server = new EurekaServerConfigBean();
if (clientConfig.shouldRegisterWithEureka()) {
// Set a sensible default if we are supposed to replicate
server.setRegistrySyncRetries(5);
}
return server;
}
}
//載入EurekaController,SpringCloud 提供了一些額外的介面,用來獲取eurekaServer的資訊
@Bean
@ConditionalOnProperty(prefix = "eureka.dashboard", name = "enabled", matchIfMissing = true)
public EurekaController eurekaController() {
return new EurekaController(this.applicationInfoManager);
}
//省略 ...
// 接收客戶端的註冊等請求就是通過InstanceRegistry來處理的,是真正處理業務的類,接下來會詳細分析
@Bean
public PeerAwareInstanceRegistry peerAwareInstanceRegistry(
ServerCodecs serverCodecs) {
this.eurekaClient.getApplications(); // force initialization
return new InstanceRegistry(this.eurekaServerConfig, this.eurekaClientConfig,
serverCodecs, this.eurekaClient,
this.instanceRegistryProperties.getExpectedNumberOfRenewsPerMin(),
this.instanceRegistryProperties.getDefaultOpenForTrafficCount());
}
//配置服務節點資訊,這裡的作用主要是為了配置Eureka的peer節點,也就是說當有收到有節點註冊上來的時候,需要通知給哪些節點
@Bean
@ConditionalOnMissingBean
public PeerEurekaNodes peerEurekaNodes(PeerAwareInstanceRegistry registry,
ServerCodecs serverCodecs) {
return new RefreshablePeerEurekaNodes(registry, this.eurekaServerConfig,
this.eurekaClientConfig, serverCodecs, this.applicationInfoManager);
}
//省略 ...
//EurekaServer的上下文
@Bean
public EurekaServerContext eurekaServerContext(ServerCodecs serverCodecs,
PeerAwareInstanceRegistry registry, PeerEurekaNodes peerEurekaNodes) {
return new DefaultEurekaServerContext(this.eurekaServerConfig, serverCodecs,
registry, peerEurekaNodes, this.applicationInfoManager);
}
// 初始化Eureka-server,會同步其他註冊中心的資料到當前註冊中心
@Bean
public EurekaServerBootstrap eurekaServerBootstrap(PeerAwareInstanceRegistry registry,
EurekaServerContext serverContext) {
return new EurekaServerBootstrap(this.applicationInfoManager,
this.eurekaClientConfig, this.eurekaServerConfig, registry,
serverContext);
}
// 配置攔截器,ServletContainer裡面實現了jersey框架,通過他來實現eurekaServer對外的restFull介面
@Bean
public FilterRegistrationBean jerseyFilterRegistration(
javax.ws.rs.core.Application eurekaJerseyApp) {
FilterRegistrationBean bean = new FilterRegistrationBean();
bean.setFilter(new ServletContainer(eurekaJerseyApp));
bean.setOrder(Ordered.LOWEST_PRECEDENCE);
bean.setUrlPatterns(
Collections.singletonList(EurekaConstants.DEFAULT_PREFIX + "/*"));
return bean;
}
//省略 ...
}
從EurekaServerAutoConfiguration 類上的註解@Import(EurekaServerInitializerConfiguration.class) 可以到,例項化類EurekaServerAutoConfiguration之前,已經例項化了EurekaServerInitializerConfiguration類,程式碼如下:
@Configuration
@CommonsLog
public class EurekaServerInitializerConfiguration
implements ServletContextAware, SmartLifecycle, Ordered {
// 此處省略部分程式碼
@Override
public void start() {
// 啟動一個執行緒
new Thread(new Runnable() {
@Override
public void run() {
try {
//初始化EurekaServer,同時啟動Eureka Server ,後面著重講這裡
eurekaServerBootstrap.contextInitialized(EurekaServerInitializerConfiguration.this.servletContext);
log.info("Started Eureka Server");
// 釋出EurekaServer的註冊事件
publish(new EurekaRegistryAvailableEvent(getEurekaServerConfig()));
// 設定啟動的狀態為true
EurekaServerInitializerConfiguration.this.running = true;
// 傳送Eureka Start 事件 , 其他還有各種事件,我們可以監聽這種時間,然後做一些特定的業務需求,後面會講到。
publish(new EurekaServerStartedEvent(getEurekaServerConfig()));
}
catch (Exception ex) {
// Help!
log.error("Could not initialize Eureka servlet context", ex);
}
}
}).start();
}
// 此處省略部分程式碼
}
這個start方法中開啟了一個新的執行緒,然後進行一些Eureka Server的初始化工作,比如呼叫eurekaServerBootstrap的contextInitialized方法,EurekaServerBootstrap程式碼如下:
public class EurekaServerBootstrap {
// 此處省略部分程式碼
public void contextInitialized(ServletContext context) {
try {
// 初始化Eureka的環境變數
initEurekaEnvironment();
// 初始化Eureka的上下文
initEurekaServerContext();
context.setAttribute(EurekaServerContext.class.getName(), this.serverContext);
}
catch (Throwable e) {
log.error("Cannot bootstrap eureka server :", e);
throw new RuntimeException("Cannot bootstrap eureka server :", e);
}
}
protected void initEurekaEnvironment() throws Exception {
log.info("Setting the eureka configuration..");
String dataCenter = ConfigurationManager.getConfigInstance()
.getString(EUREKA_DATACENTER);
if (dataCenter == null) {
log.info(
"Eureka data center value eureka.datacenter is not set, defaulting to default");
ConfigurationManager.getConfigInstance()
.setProperty(ARCHAIUS_DEPLOYMENT_DATACENTER, DEFAULT);
}
else {
ConfigurationManager.getConfigInstance()
.setProperty(ARCHAIUS_DEPLOYMENT_DATACENTER, dataCenter);
}
String environment = ConfigurationManager.getConfigInstance()
.getString(EUREKA_ENVIRONMENT);
if (environment == null) {
ConfigurationManager.getConfigInstance()
.setProperty(ARCHAIUS_DEPLOYMENT_ENVIRONMENT, TEST);
log.info(
"Eureka environment value eureka.environment is not set, defaulting to test");
}
else {
ConfigurationManager.getConfigInstance()
.setProperty(ARCHAIUS_DEPLOYMENT_ENVIRONMENT, environment);
}
}
protected void initEurekaServerContext() throws Exception {
// For backward compatibility
JsonXStream.getInstance().registerConverter(new V1AwareInstanceInfoConverter(),
XStream.PRIORITY_VERY_HIGH);
XmlXStream.getInstance().registerConverter(new V1AwareInstanceInfoConverter(),
XStream.PRIORITY_VERY_HIGH);
if (isAws(this.applicationInfoManager.getInfo())) {
this.awsBinder = new AwsBinderDelegate(this.eurekaServerConfig,
this.eurekaClientConfig, this.registry, this.applicationInfoManager);
this.awsBinder.start();
}
//初始化eureka server上下文
EurekaServerContextHolder.initialize(this.serverContext);
log.info("Initialized server context");
// Copy registry from neighboring eureka node
// 從相鄰的eureka節點複製登錄檔
int registryCount = this.registry.syncUp();
// 預設每30秒傳送心跳,1分鐘就是2次
// 修改eureka狀態為up
// 同時,這裡面會開啟一個定時任務,用於清理 60秒沒有心跳的客戶端。自動下線
this.registry.openForTraffic(this.applicationInfoManager, registryCount);
// Register all monitoring statistics.
EurekaMonitors.registerAllStats();
}
public void contextDestroyed(ServletContext context) {
try {
log.info("Shutting down Eureka Server..");
context.removeAttribute(EurekaServerContext.class.getName());
destroyEurekaServerContext();
destroyEurekaEnvironment();
}
catch (Throwable e) {
log.error("Error shutting down eureka", e);
}
log.info("Eureka Service is now shutdown...");
}
}
在初始化Eureka Server上下文環境後,就會繼續執行openForTraffic方法,這個方法主要是設定了期望每分鐘接收到的心跳次數,並將服務例項的狀態設定為UP,最後又通過方法postInit來開啟一個定時任務,用於每隔一段時間(預設60秒)將沒有續約的服務例項(預設90秒沒有續約)清理掉。openForTraffic的方法程式碼如下:
@Override
public void openForTraffic(ApplicationInfoManager applicationInfoManager, int count) {
// Renewals happen every 30 seconds and for a minute it should be a factor of 2.
// 計算每分鐘最大續約數
this.expectedNumberOfRenewsPerMin = count * 2;
// 計算每分鐘最小續約數
this.numberOfRenewsPerMinThreshold =
(int) (this.expectedNumberOfRenewsPerMin * serverConfig.getRenewalPercentThreshold());
logger.info("Got {} instances from neighboring DS node", count);
logger.info("Renew threshold is: {}", numberOfRenewsPerMinThreshold);
this.startupTime = System.currentTimeMillis();
if (count > 0) {
this.peerInstancesTransferEmptyOnStartup = false;
}
DataCenterInfo.Name selfName = applicationInfoManager.getInfo().getDataCenterInfo().getName();
boolean isAws = Name.Amazon == selfName;
if (isAws && serverConfig.shouldPrimeAwsReplicaConnections()) {
logger.info("Priming AWS connections for all replicas..");
primeAwsReplicas(applicationInfoManager);
}
logger.info("Changing status to UP");
// 修改服務例項的狀態為UP
applicationInfoManager.setInstanceStatus(InstanceStatus.UP);
// 開啟定時任務,每隔一段時間(預設60秒)將沒有續約的服務例項(預設90秒沒有續約)清理掉
super.postInit();
}
postInit方法開啟了一個新的定時任務,程式碼如下:
protected void postInit() {
renewsLastMin.start();
if (evictionTaskRef.get() != null) {
evictionTaskRef.get().cancel();
}
evictionTaskRef.set(new EvictionTask());
evictionTimer.schedule(evictionTaskRef.get(),
serverConfig.getEvictionIntervalTimerInMs(),
serverConfig.getEvictionIntervalTimerInMs());
}
這裡的時間間隔都來自於EurekaServerConfigBean類,可以在配置檔案中以eureka.server開頭的配置來進行設定。
參考
https://www.e-learn.cn/content/qita/775244/
https://nobodyiam.com/2016/06/25/dive-into-eureka/
https://blog.csdn.net/Lammonpeter/article/details/84330900
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