eureka server源代码目结构
├── spring-cloud-netflix-eureka-server
│ ├── pom.xml
│ ├── src
│ │ ├── main
│ │ │ ├── java
│ │ │ │ └── org
│ │ │ │ └── springframework
│ │ │ │ └── cloud
│ │ │ │ └── netflix
│ │ │ │ └── eureka
│ │ │ │ └── server
│ │ │ │ ├── CloudJacksonJson.java
│ │ │ │ ├── EnableEurekaServer.java
│ │ │ │ ├── EurekaController.java
│ │ │ │ ├── EurekaDashboardProperties.java
│ │ │ │ ├── EurekaServerAutoConfiguration.java
│ │ │ │ ├── EurekaServerBootstrap.java
│ │ │ │ ├── EurekaServerConfigBean.java
│ │ │ │ ├── EurekaServerInitializerConfiguration.java
│ │ │ │ ├── EurekaServerMarkerConfiguration.java
│ │ │ │ ├── InstanceRegistry.java
│ │ │ │ ├── InstanceRegistryProperties.java
│ │ │ │ ├── ReplicationClientAdditionalFilters.java
│ │ │ │ └── event
│ │ │ │ ├── EurekaInstanceCanceledEvent.java
│ │ │ │ ├── EurekaInstanceRegisteredEvent.java
│ │ │ │ ├── EurekaInstanceRenewedEvent.java
│ │ │ │ ├── EurekaRegistryAvailableEvent.java
│ │ │ │ └── EurekaServerStartedEvent.java
│ │ │ ├── resources
│ │ │ │ ├── META-INF
│ │ │ │ │ └── spring.factories
│ │ │ │ ├── eureka
│ │ │ │ │ └── server.properties
启动过程分析
1. @EnableEurekaServer
在spring-cloud项目中，启动eureka server需要添加一个@EnableEurekaServer注解。
2.@ConditionalOnBean
spring-boot基于spring-framework的@Conditional提供了提一套条件注解，其中@ConditionalOnBean会根据当前BeanFactory中是否存在某个类的bean实例决定是否创建注解标识的类实例，而spring-cloud-netflix-eureka-server的判断条件则是@EnableEurekaServer中通过@Import导入的EurekaServerMarkerConfiguration内部类Marker。启动时spring扫描到Marker类的bean后，EurekaServerMarkerConfiguration中的eureka所需的bean便开始创建了。
3.创建eureka-server所需的类实例
3.1 eureka相关配置
- 控制面板配置
@Bean
@ConditionalOnProperty(prefix = "eureka.dashboard", name = "enabled", matchIfMissing = true)
public EurekaController eurekaController() {
return new EurekaController(this.applicationInfoManager);
}
用户启用了dashboard后，会创建EurekaController的bean，并注入ApplicationInfoManager实例供控制面板所需功能使用。
- 编码器配置
@Bean
public ServerCodecs serverCodecs() {
return new CloudServerCodecs(this.eurekaServerConfig);
}
spring cloud的CloudServerCodecs重写了eureka编码器DefaultServerCodecs的构造函数，目的是替换eureka的json序列化实现。相类似的，json序列化是通过spring cloud的CloudJacksonCodec重写eureka的EurekaJacksonCodec的构造函数。
CloudJacksonCodec() {
super();
ObjectMapper mapper = new ObjectMapper();
mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
SimpleModule module = new SimpleModule("eureka1.x", VERSION);
module.addSerializer(DataCenterInfo.class, new DataCenterInfoSerializer());
module.addSerializer(InstanceInfo.class, new CloudInstanceInfoSerializer());
module.addSerializer(Application.class, new ApplicationSerializer());
module.addSerializer(Applications.class,
new ApplicationsSerializer(this.getVersionDeltaKey(), this.getAppHashCodeKey()));
// TODO: Watch if this causes problems
// module.addDeserializer(DataCenterInfo.class,
// new DataCenterInfoDeserializer());
module.addDeserializer(LeaseInfo.class, new LeaseInfoDeserializer());
module.addDeserializer(InstanceInfo.class, new CloudInstanceInfoDeserializer(mapper));
module.addDeserializer(Application.class, new ApplicationDeserializer(mapper));
module.addDeserializer(Applications.class,
new ApplicationsDeserializer(mapper, this.getVersionDeltaKey(), this.getAppHashCodeKey()));
mapper.registerModule(module);
HashMap<Class<?>, Supplier<ObjectReader>> readers = new HashMap<>();
readers.put(InstanceInfo.class,
() -> mapper.reader().withType(InstanceInfo.class).withRootName("instance"));
readers.put(Application.class,
() -> mapper.reader().withType(Application.class).withRootName("application"));
readers.put(Applications.class,
() -> mapper.reader().withType(Applications.class).withRootName("applications"));
setField("objectReaderByClass", readers);
HashMap<Class<?>, ObjectWriter> writers = new HashMap<>();
writers.put(InstanceInfo.class, mapper.writer().withType(InstanceInfo.class).withRootName("instance"));
writers.put(Application.class, mapper.writer().withType(Application.class).withRootName("application"));
writers.put(Applications.class, mapper.writer().withType(Applications.class).withRootName("applications"));
setField("objectWriterByClass", writers);
setField("mapper", mapper);
}
核心是使用反射能力，替换父类成员变量中的jackson实现。
void setField(String name, Object value) {
Field field = ReflectionUtils.findField(EurekaJacksonCodec.class, name);
ReflectionUtils.makeAccessible(field);
ReflectionUtils.setField(field, this, value);
}
- 注册中心实例创建
@Bean
public PeerAwareInstanceRegistry peerAwareInstanceRegistry(ServerCodecs serverCodecs) {
this.eurekaClient.getApplications(); // force initialization
return new InstanceRegistry(this.eurekaServerConfig, this.eurekaClientConfig, serverCodecs, this.eurekaClient,
this.instanceRegistryProperties.getExpectedNumberOfClientsSendingRenews(),
this.instanceRegistryProperties.getDefaultOpenForTrafficCount());
}
spring cloud的InstanceRegistry继承了eureka的PeerAwareInstanceRegistryImpl，并接入了spring的ApplicationContextAware，将spring的context注入到了注册中心。
@Override
public void register(InstanceInfo info, int leaseDuration, boolean isReplication) {
handleRegistration(info, leaseDuration, isReplication);
super.register(info, leaseDuration, isReplication);
}
@Override
public void register(final InstanceInfo info, final boolean isReplication) {
handleRegistration(info, resolveInstanceLeaseDuration(info), isReplication);
super.register(info, isReplication);
}
@Override
public boolean cancel(String appName, String serverId, boolean isReplication) {
handleCancelation(appName, serverId, isReplication);
return super.cancel(appName, serverId, isReplication);
}
@Override
public boolean renew(final String appName, final String serverId, boolean isReplication) {
log("renew " + appName + " serverId " + serverId + ", isReplication {}" + isReplication);
List<Application> applications = getSortedApplications();
for (Application input : applications) {
if (input.getName().equals(appName)) {
InstanceInfo instance = null;
for (InstanceInfo info : input.getInstances()) {
if (info.getId().equals(serverId)) {
instance = info;
break;
}
}
publishEvent(new EurekaInstanceRenewedEvent(this, appName, serverId, instance, isReplication));
break;
}
}
return super.renew(appName, serverId, isReplication);
}
@Override
protected boolean internalCancel(String appName, String id, boolean isReplication) {
handleCancelation(appName, id, isReplication);
return super.internalCancel(appName, id, isReplication);
}
通过重写PeerAwareInstanceRegistryImpl，提供了eureka-client的注册、取消、续约事件订阅功能。
- eureka的context创建
@Bean
@ConditionalOnMissingBean
public EurekaServerContext eurekaServerContext(ServerCodecs serverCodecs, PeerAwareInstanceRegistry registry,
PeerEurekaNodes peerEurekaNodes) {
return new DefaultEurekaServerContext(this.eurekaServerConfig, serverCodecs, registry, peerEurekaNodes,
this.applicationInfoManager);
}
此处就是eureka默认的实现，未做修改。
- eureka启动器配置
@Bean
public EurekaServerBootstrap eurekaServerBootstrap(PeerAwareInstanceRegistry registry,
EurekaServerContext serverContext) {
return new EurekaServerBootstrap(this.applicationInfoManager, this.eurekaClientConfig, this.eurekaServerConfig,
registry, serverContext);
}
- jersey过滤器配置
@Bean
@ConditionalOnMissingBean
public ReplicationClientAdditionalFilters replicationClientAdditionalFilters() {
return new ReplicationClientAdditionalFilters(Collections.emptySet());
}
- jersey过滤器注册器配置
/**
* Register the Jersey filter.
* @param eurekaJerseyApp an {@link Application} for the filter to be registered
* @return a jersey {@link FilterRegistrationBean}
*/
@Bean
public FilterRegistrationBean<?> jerseyFilterRegistration(javax.ws.rs.core.Application eurekaJerseyApp) {
FilterRegistrationBean<Filter> bean = new FilterRegistrationBean<Filter>();
bean.setFilter(new ServletContainer(eurekaJerseyApp));
bean.setOrder(Ordered.LOWEST_PRECEDENCE);
bean.setUrlPatterns(Collections.singletonList(EurekaConstants.DEFAULT_PREFIX + "/*"));
return bean;
}
- eureka-server节点实例配置
@Bean
@ConditionalOnMissingBean
public PeerEurekaNodes peerEurekaNodes(PeerAwareInstanceRegistry registry, ServerCodecs serverCodecs,
ReplicationClientAdditionalFilters replicationClientAdditionalFilters) {
return new RefreshablePeerEurekaNodes(registry, this.eurekaServerConfig, this.eurekaClientConfig, serverCodecs,
this.applicationInfoManager, replicationClientAdditionalFilters);
}
spring-cloud的RefreshablePeerEurekaNodes继承了eureka的PeerEurekaNodes，新增了一个构造方法，将ReplicationClientAdditionalFilters注入到当前实例成员变量中。
private ReplicationClientAdditionalFilters replicationClientAdditionalFilters;
RefreshablePeerEurekaNodes(final PeerAwareInstanceRegistry registry, final EurekaServerConfig serverConfig,
final EurekaClientConfig clientConfig, final ServerCodecs serverCodecs,
final ApplicationInfoManager applicationInfoManager,
final ReplicationClientAdditionalFilters replicationClientAdditionalFilters) {
super(registry, serverConfig, clientConfig, serverCodecs, applicationInfoManager);
this.replicationClientAdditionalFilters = replicationClientAdditionalFilters;
}
@Override
protected PeerEurekaNode createPeerEurekaNode(String peerEurekaNodeUrl) {
JerseyReplicationClient replicationClient = JerseyReplicationClient.createReplicationClient(serverConfig,
serverCodecs, peerEurekaNodeUrl);
this.replicationClientAdditionalFilters.getFilters().forEach(replicationClient::addReplicationClientFilter);
String targetHost = hostFromUrl(peerEurekaNodeUrl);
if (targetHost == null) {
targetHost = "host";
}
return new PeerEurekaNode(registry, targetHost, peerEurekaNodeUrl, replicationClient, serverConfig);
}
作用是通过重写eureka节点创建方法(createPeerEurekaNode)，将spring-cloud中配置的replicationClientAdditionalFilters(jersey的ClientFilter集)过滤器添加到jersey的client实例中(eureka接口基于JAX-RS，所以用的jersey)。
@Override
public void onApplicationEvent(final EnvironmentChangeEvent event) {
if (shouldUpdate(event.getKeys())) {
updatePeerEurekaNodes(resolvePeerUrls());
}
}
另外RefreshablePeerEurekaNodes实现了spring的ApplicationListener<EnvironmentChangeEvent>接口，在收到spring事件回调时，会触发eureka-server节点更新；
- eureka配置类实例
@Configuration(proxyBeanMethods = false)
protected static class EurekaServerConfigBeanConfiguration {
@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;
}
}
此处利用spring-boot的@ConfigurationProperties注解，将配置文件(application.properties)中的eureka配置信息同步到EurekaServerConfigBean类实例中，因EurekaServerConfigBean实现了EurekaServerConfig接口，故可供eureka-server启动时读取。
3.2 spring相关配置
- spring-boot端点配置
@Bean
public HasFeatures eurekaServerFeature() {
return HasFeatures.namedFeature("Eureka Server", EurekaServerAutoConfiguration.class);
}
- JAX-RS配置
/**
* Construct a Jersey {@link javax.ws.rs.core.Application} with all the resources
* required by the Eureka server.
* @param environment an {@link Environment} instance to retrieve classpath resources
* @param resourceLoader a {@link ResourceLoader} instance to get classloader from
* @return created {@link Application} object
*/
@Bean
public javax.ws.rs.core.Application jerseyApplication(Environment environment, ResourceLoader resourceLoader) {
ClassPathScanningCandidateComponentProvider provider = new ClassPathScanningCandidateComponentProvider(false,
environment);
// Filter to include only classes that have a particular annotation.
//
provider.addIncludeFilter(new AnnotationTypeFilter(Path.class));
provider.addIncludeFilter(new AnnotationTypeFilter(Provider.class));
// Find classes in Eureka packages (or subpackages)
//
Set<Class<?>> classes = new HashSet<>();
for (String basePackage : EUREKA_PACKAGES) {
Set<BeanDefinition> beans = provider.findCandidateComponents(basePackage);
for (BeanDefinition bd : beans) {
Class<?> cls = ClassUtils.resolveClassName(bd.getBeanClassName(), resourceLoader.getClassLoader());
classes.add(cls);
}
}
// Construct the Jersey ResourceConfig
Map<String, Object> propsAndFeatures = new HashMap<>();
propsAndFeatures.put(
// Skip static content used by the webapp
ServletContainer.PROPERTY_WEB_PAGE_CONTENT_REGEX,
EurekaConstants.DEFAULT_PREFIX + "/(fonts|images|css|js)/.*");
DefaultResourceConfig rc = new DefaultResourceConfig(classes);
rc.setPropertiesAndFeatures(propsAndFeatures);
return rc;
}
- servlet过滤器配置
@Bean
@ConditionalOnBean(name = "httpTraceFilter")
public FilterRegistrationBean<?> traceFilterRegistration(@Qualifier("httpTraceFilter") Filter filter) {
FilterRegistrationBean<Filter> bean = new FilterRegistrationBean<Filter>();
bean.setFilter(filter);
bean.setOrder(Ordered.LOWEST_PRECEDENCE - 10);
return bean;
}
4. 启动eureka-server
EurekaServerInitializerConfiguration类实现了spring的SmartLifecycle接口，并且order值为1(bean创建优先级高)，在spring生命周期开始时，就开始启动eureka-server。
@Autowired
private EurekaServerBootstrap eurekaServerBootstrap;
@Override
public void start() {
new Thread(() -> {
try {
// TODO: is this class even needed now?
eurekaServerBootstrap.contextInitialized(EurekaServerInitializerConfiguration.this.servletContext);
log.info("Started Eureka Server");
publish(new EurekaRegistryAvailableEvent(getEurekaServerConfig()));
EurekaServerInitializerConfiguration.this.running = true;
publish(new EurekaServerStartedEvent(getEurekaServerConfig()));
}
catch (Exception ex) {
// Help!
log.error("Could not initialize Eureka servlet context", ex);
}
}).start();
}
创建一个新的线程，调用注入进来的成员变量eurekaServerBootstrap的contextInitialized方法开始启动，启动成功后发布eureka允许注册事件和eureka-server已启动事件。
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