SpringCloud eureka服务端启动过程解析
版本
springCloud:Finchley
springboot:2.0.3
####标题
查看spring-cloud-netflix-eureka-server-2.0.0.jar下面的META-INF/spring-factories,查看项目启动时的自动配置类（参考SpringBoot自动配置分析文章）
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
org.springframework.cloud.netflix.eureka.server.EurekaServerAutoConfiguration
所以Springboot项目启动时会自动初始化EurekaServerAutoConfiguration.java这个配置类:
@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 {
@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;
}
}
@Bean
@ConditionalOnProperty(prefix = "eureka.dashboard", name = "enabled", matchIfMissing = true)
public EurekaController eurekaController() {
return new EurekaController(this.applicationInfoManager);
}
static {
CodecWrappers.registerWrapper(JACKSON_JSON);
EurekaJacksonCodec.setInstance(JACKSON_JSON.getCodec());
}
@Bean
public ServerCodecs serverCodecs() {
return new CloudServerCodecs(this.eurekaServerConfig);
}
private static CodecWrapper getFullJson(EurekaServerConfig serverConfig) {
CodecWrapper codec = CodecWrappers.getCodec(serverConfig.getJsonCodecName());
return codec == null ? CodecWrappers.getCodec(JACKSON_JSON.codecName()) : codec;
}
private static CodecWrapper getFullXml(EurekaServerConfig serverConfig) {
CodecWrapper codec = CodecWrappers.getCodec(serverConfig.getXmlCodecName());
return codec == null ? CodecWrappers.getCodec(CodecWrappers.XStreamXml.class)
: codec;
}
class CloudServerCodecs extends DefaultServerCodecs {
public CloudServerCodecs(EurekaServerConfig serverConfig) {
super(getFullJson(serverConfig),
CodecWrappers.getCodec(CodecWrappers.JacksonJsonMini.class),
getFullXml(serverConfig),
CodecWrappers.getCodec(CodecWrappers.JacksonXmlMini.class));
}
}
@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());
}
@Bean
@ConditionalOnMissingBean
public PeerEurekaNodes peerEurekaNodes(PeerAwareInstanceRegistry registry,
ServerCodecs serverCodecs) {
return new RefreshablePeerEurekaNodes(registry, this.eurekaServerConfig,
this.eurekaClientConfig, serverCodecs, this.applicationInfoManager);
}
/**
* {@link PeerEurekaNodes} which updates peers when /refresh is invoked.
* Peers are updated only if
* eureka.client.use-dns-for-fetching-service-urls is
* false and one of following properties have changed.
*
*
* eureka.client.availability-zoneseureka.client.regioneureka.client.service-url.<zone>
*/
static class RefreshablePeerEurekaNodes extends PeerEurekaNodes
implements ApplicationListener {
public RefreshablePeerEurekaNodes(
final PeerAwareInstanceRegistry registry,
final EurekaServerConfig serverConfig,
final EurekaClientConfig clientConfig,
final ServerCodecs serverCodecs,
final ApplicationInfoManager applicationInfoManager) {
super(registry, serverConfig, clientConfig, serverCodecs, applicationInfoManager);
}
@Override
public void onApplicationEvent(final EnvironmentChangeEvent event) {
if (shouldUpdate(event.getKeys())) {
updatePeerEurekaNodes(resolvePeerUrls());
}
}
/*
* Check whether specific properties have changed.
*/
protected boolean shouldUpdate(final Set changedKeys) {
assert changedKeys != null;
// if eureka.client.use-dns-for-fetching-service-urls is true, then
// service-url will not be fetched from environment.
if (clientConfig.shouldUseDnsForFetchingServiceUrls()) {
return false;
}
if (changedKeys.contains("eureka.client.region")) {
return true;
}
for (final String key : changedKeys) {
// property keys are not expected to be null.
if (key.startsWith("eureka.client.service-url.") ||
key.startsWith("eureka.client.availability-zones.")) {
return true;
}
}
return false;
}
}
@Bean
public EurekaServerContext eurekaServerContext(ServerCodecs serverCodecs,
PeerAwareInstanceRegistry registry, PeerEurekaNodes peerEurekaNodes) {
return new DefaultEurekaServerContext(this.eurekaServerConfig, serverCodecs,
registry, peerEurekaNodes, this.applicationInfoManager);
}
@Bean
public EurekaServerBootstrap eurekaServerBootstrap(PeerAwareInstanceRegistry registry,
EurekaServerContext serverContext) {
return new EurekaServerBootstrap(this.applicationInfoManager,
this.eurekaClientConfig, this.eurekaServerConfig, registry,
serverContext);
}
/**
* Register the Jersey filter
*/
@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;
}
/**
* Construct a Jersey {@link javax.ws.rs.core.Application} with all the resources
* required by the Eureka server.
*/
@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> classes = new HashSet<>();
for (String basePackage : EUREKA_PACKAGES) {
Set beans = provider.findCandidateComponents(basePackage);
for (BeanDefinition bd : beans) {
Class cls = ClassUtils.resolveClassName(bd.getBeanClassName(),
resourceLoader.getClassLoader());
classes.add(cls);
}
}
// Construct the Jersey ResourceConfig
//
Map 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;
}
@Bean
public FilterRegistrationBean traceFilterRegistration(
@Qualifier("httpTraceFilter") Filter filter) {
FilterRegistrationBean bean = new FilterRegistrationBean();
bean.setFilter(filter);
bean.setOrder(Ordered.LOWEST_PRECEDENCE - 10);
return bean;
}
}
@EnableEurekaServer开启
我们可以看到这个类上面使用了
@ConditionalOnBean(EurekaServerMarkerConfiguration.Marker.class)，表明只有当EurekaServerMarkerConfiguration.Marker.class这个bean存在时才会真正的加载这些配置。该bean是在哪里初始化的呢?我们记得在搭建eureka项目是需要在启动器上面加注解@EnableEurekaServer吗，现在看一下源码。
这是一个空的注解,引用EurekaServerMarkerConfiguration这个类
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(EurekaServerMarkerConfiguration.class)
public @interface EnableEurekaServer {
}
EurekaServerMarkerConfiguration.java中配置了一个bean,正是EurekaServerMarkerConfiguration.Marker.class
@Configuration
public class EurekaServerMarkerConfiguration {
@Bean
public Marker eurekaServerMarkerBean() {
return new Marker();
}
class Marker {
}
}
@Import(EurekaServerInitializerConfiguration.class
表明EurekaServerAutoConfiguration.java配置完成后会加载该配置，调用EurekaServerBootstrap的contextInitialized方法启动eureka server
我们继续看EurekaServerAutoConfiguration.java配置了如下几个bean.
EurekaServerConfigBean: 封装eureka.server为前缀的配置
EurekaController：一个控制器，就是我们通常访问的cloud-eureka后台的，查看注册中心信息，这是springcloud添加的不是 netflix-eureka原生的。
主要代码：
我们平时访问的htt://localhost:8761其实就是这个接口
@RequestMapping(method = RequestMethod.GET)
public String status(HttpServletRequest request, Map model) {
populateBase(request, model);
populateApps(model);
StatusInfo statusInfo;
try {
statusInfo = new StatusResource().getStatusInfo();
}
catch (Exception e) {
statusInfo = StatusInfo.Builder.newBuilder().isHealthy(false).build();
}
model.put("statusInfo", statusInfo);
populateInstanceInfo(model, statusInfo);
filterReplicas(model, statusInfo);
return "eureka/status";
}
@RequestMapping(value = "/lastn", method = RequestMethod.GET)
public String lastn(HttpServletRequest request, Map model) {
populateBase(request, model);
PeerAwareInstanceRegistryImpl registry = (PeerAwareInstanceRegistryImpl) getRegistry();
ArrayList> lastNCanceled = new ArrayList<>();
List> list = registry.getLastNCanceledInstances();
for (Pair entry : list) {
lastNCanceled.add(registeredInstance(entry.second(), entry.first()));
}
model.put("lastNCanceled", lastNCanceled);
list = registry.getLastNRegisteredInstances();
ArrayList> lastNRegistered = new ArrayList<>();
for (Pair entry : list) {
lastNRegistered.add(registeredInstance(entry.second(), entry.first()));
}
model.put("lastNRegistered", lastNRegistered);
return "eureka/lastn";
}
ServerCodecs：配置数据传输的格式的帮助类，支持JSON和XML两种格式
class CloudServerCodecs extends DefaultServerCodecs {
public CloudServerCodecs(EurekaServerConfig serverConfig) {
super(getFullJson(serverConfig),
CodecWrappers.getCodec(CodecWrappers.JacksonJsonMini.class),
getFullXml(serverConfig),
CodecWrappers.getCodec(CodecWrappers.JacksonXmlMini.class));
}
}
PeerAwareInstanceRegistry： eureka-server集群节点中的信息同步接口是eureka原生,可能为了扩展，在这springcloud做了一层封装即org.springframework.cloud.netflix.eureka.server.InstanceRegistry,实际上还是交给PeerAwareInstanceRegistry的原生实现类com.netflix.eureka.registry.PeerAwareInstanceRegistryImpl去做的,InstanceRegistry继承了PeerAwareInstanceRegistryImpl
。
public interface PeerAwareInstanceRegistry extends InstanceRegistry {
void init(PeerEurekaNodes peerEurekaNodes) throws Exception;
/**
* 从其他节点同步注册信息，如果失败就从下一个节点同步
*/
int syncUp();
/**
* Checks to see if the registry access is allowed or the server is in a
* situation where it does not all getting registry information. The server
* does not return registry information for a period specified in
* {@link com.netflix.eureka.EurekaServerConfig#getWaitTimeInMsWhenSyncEmpty()}, if it cannot
* get the registry information from the peer eureka nodes at start up.
*
* @return false - if the instances count from a replica transfer returned
* zero and if the wait time has not elapsed, otherwise returns true
*/
boolean shouldAllowAccess(boolean remoteRegionRequired);
//注册接口,真正处理注册流程
void register(InstanceInfo info, boolean isReplication);
//状态更新
void statusUpdate(final String asgName, final ASGResource.ASGStatus newStatus, final boolean isReplication);
}
PeerEurekaNodes集群节点信息，管理节点（如添加、减少时）
EurekaServerContext：EurekaServerContext上下文
EurekaServerBootstrap：初始化eureka server的启动，EurekaServerInitializerConfiguration的start方法调用
Application：创建一个jersey应用。构建RESTful服务
扫描com.netflix.discovery，com.netflix.eureka包下所有被@Path和@Provider修饰的资源，封装成Jersey ResourceConfig
private static final String[] EUREKA_PACKAGES = new String[] { "com.netflix.discovery",
"com.netflix.eureka" };
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> classes = new HashSet<>();
for (String basePackage : EUREKA_PACKAGES) {
Set beans = provider.findCandidateComponents(basePackage);
for (BeanDefinition bd : beans) {
Class cls = ClassUtils.resolveClassName(bd.getBeanClassName(),
resourceLoader.getClassLoader());
classes.add(cls);
}
}
// Construct the Jersey ResourceConfig
//
Map 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;
}
FilterRegistrationBean：注册过滤器,将 jersey application资源封装成ServletContainer（实现了Filter接口）