先从github上github.com/Netflix/eur…把eureka的源码导到idea上
<listener>
<listener-class>com.netflix.eureka.EurekaBootStrap</listener-class>
</listener>
监听器会随着web应用的启动而启动,随web应用的停止而销毁。一般做一些初始化工作。
下面来看看这个EurekaBootStrap:
/**
* Initializes Eureka, including syncing up with other Eureka peers and publishing the registry.
*
* @see
* javax.servlet.ServletContextListener#contextInitialized(javax.servlet.ServletContextEvent)
*/
@Override
public void contextInitialized(ServletContextEvent event) {
try {
//初始化eureka环境
initEurekaEnvironment();
//初始化eureka上下文
initEurekaServerContext();
ServletContext sc = event.getServletContext();
sc.setAttribute(EurekaServerContext.class.getName(), serverContext);
} catch (Throwable e) {
logger.error("Cannot bootstrap eureka server :", e);
throw new RuntimeException("Cannot bootstrap eureka server :", e);
}
}
启动的入口就是这个contextInitialized()方法了。
来看看initEurekaEnvironment()
protected void initEurekaEnvironment() throws Exception {
logger.info("Setting the eureka configuration..");
String dataCenter = ConfigurationManager.getConfigInstance().getString(EUREKA_DATACENTER);
if (dataCenter == null) {
logger.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);
logger.info("Eureka environment value eureka.environment is not set, defaulting to test");
}
}
主要创建了配置管理器ConfigurationManager，初始化了数据中心(默认default)和环境(默认Test)。
//用了double-check+volatile来实现实现线程安全的单例模式来创建ConfigurationManager
public static AbstractConfiguration getConfigInstance() {
if (instance == null) {
synchronized (ConfigurationManager.class) {
if (instance == null) {
instance = getConfigInstance(Boolean.getBoolean(DynamicPropertyFactory.DISABLE_DEFAULT_CONFIG));
}
}
}
return instance;
}
private static AbstractConfiguration createDefaultConfigInstance() {
ConcurrentCompositeConfiguration config = new ConcurrentCompositeConfiguration();
try {
DynamicURLConfiguration defaultURLConfig = new DynamicURLConfiguration();
config.addConfiguration(defaultURLConfig, URL_CONFIG_NAME);
} catch (Throwable e) {
logger.warn("Failed to create default dynamic configuration", e);
}
if (!Boolean.getBoolean(DISABLE_DEFAULT_SYS_CONFIG)) {
SystemConfiguration sysConfig = new SystemConfiguration();
config.addConfiguration(sysConfig, SYS_CONFIG_NAME);
}
if (!Boolean.getBoolean(DISABLE_DEFAULT_ENV_CONFIG)) {
EnvironmentConfiguration envConfig = new EnvironmentConfiguration();
config.addConfiguration(envConfig, ENV_CONFIG_NAME);
}
ConcurrentCompositeConfiguration appOverrideConfig = new ConcurrentCompositeConfiguration();
config.addConfiguration(appOverrideConfig, APPLICATION_PROPERTIES);
config.setContainerConfigurationIndex(config.getIndexOfConfiguration(appOverrideConfig));
return config;
}
ConfigurationManager初始化过程无非就是创建一个ConcurrentCompositeConfiguration实例，然后往里面加了一堆config，然后返回
总结:
eureka-server初始化环境：
1.创建单例ConfigurationManager来管理eureka-server的配置信息，double-check+volatile单例模式。
2.初始化dataCenter,没配置的话，设default
3.初始化environment,没配置的话，设test
下面来看eureka-server初始化上下文:initEurekaServerContext()
protected void initEurekaServerContext() throws Exception {
//加载eureka-server.properties配置文件，将配置项加载到ConfigurationManager中
EurekaServerConfig eurekaServerConfig = new DefaultEurekaServerConfig();
// For backward compatibility
JsonXStream.getInstance().registerConverter(new V1AwareInstanceInfoConverter(), XStream.PRIORITY_VERY_HIGH);
XmlXStream.getInstance().registerConverter(new V1AwareInstanceInfoConverter(), XStream.PRIORITY_VERY_HIGH);
logger.info("Initializing the eureka client...");
logger.info(eurekaServerConfig.getJsonCodecName());
ServerCodecs serverCodecs = new DefaultServerCodecs(eurekaServerConfig);
ApplicationInfoManager applicationInfoManager = null;
//初始化eureka-server内部的eureka-client用来与其他eureka-server节点进行注册和通信
if (eurekaClient == null) {
EurekaInstanceConfig instanceConfig = isCloud(ConfigurationManager.getDeploymentContext())
? new CloudInstanceConfig()
: new MyDataCenterInstanceConfig();
applicationInfoManager = new ApplicationInfoManager(
instanceConfig, new EurekaConfigBasedInstanceInfoProvider(instanceConfig).get());
EurekaClientConfig eurekaClientConfig = new DefaultEurekaClientConfig();
eurekaClient = new DiscoveryClient(applicationInfoManager, eurekaClientConfig);
} else {
applicationInfoManager = eurekaClient.getApplicationInfoManager();
}
//处理注册相关事情
//服务实例注册表
PeerAwareInstanceRegistry registry;
if (isAws(applicationInfoManager.getInfo())) {
registry = new AwsInstanceRegistry(
eurekaServerConfig,
eurekaClient.getEurekaClientConfig(),
serverCodecs,
eurekaClient
);
awsBinder = new AwsBinderDelegate(eurekaServerConfig, eurekaClient.getEurekaClientConfig(), registry, applicationInfoManager);
awsBinder.start();
} else {
registry = new PeerAwareInstanceRegistryImpl(
eurekaServerConfig,
eurekaClient.getEurekaClientConfig(),
serverCodecs,
eurekaClient
);
}
//eureka-server集群
PeerEurekaNodes peerEurekaNodes = getPeerEurekaNodes(
registry,
eurekaServerConfig,
eurekaClient.getEurekaClientConfig(),
serverCodecs,
applicationInfoManager
);
//Eureka-server上下文构建
serverContext = new DefaultEurekaServerContext(
eurekaServerConfig,
serverCodecs,
registry,
peerEurekaNodes,
applicationInfoManager
);
//将serverContext放到holder中，可以从holder中获取serverContext
EurekaServerContextHolder.initialize(serverContext);
//更新集群信息
serverContext.initialize();
logger.info("Initialized server context");
// Copy registry from neighboring eureka node
//从相邻eureka-server节点同步注册信息
int registryCount = registry.syncUp();
registry.openForTraffic(applicationInfoManager, registryCount);
// Register all monitoring statistics.
//注册所有的监控统计
EurekaMonitors.registerAllStats();
}
1.EurekaServerConfig eurekaServerConfig = new DefaultEurekaServerConfig(); 将eureka-server.properties文件的配置信息加载到ConfigurationManager中，并将配置信息通过EurekaServerConfig这个接口暴露出来。一般我们加载获取配置文件的信息，都会把信息放到Properties对象中去，然后通过prop.get("KEY")这种方式获取。这里eureka优雅的通过接口方法getXxx()方式来获取配置信息，值得学习
EurekaInstanceConfig instanceConfig = isCloud(ConfigurationManager.getDeploymentContext())
? new CloudInstanceConfig()
: new MyDataCenterInstanceConfig();
3.基于构造器模式构建出InstanceInfo(服务实例信息)，eureka server同时也是一个eureka client，因为他可能要向其他的eureka server去进行注册，eureka server也就是一个Instance实例
builder.setNamespace(config.getNamespace())
.setInstanceId(instanceId)
.setAppName(config.getAppname())
.setAppGroupName(config.getAppGroupName())
.setDataCenterInfo(config.getDataCenterInfo())
.setIPAddr(config.getIpAddress())
.setHostName(defaultAddress)
.setPort(config.getNonSecurePort())
.enablePort(PortType.UNSECURE, config.isNonSecurePortEnabled())
.setSecurePort(config.getSecurePort())
.enablePort(PortType.SECURE, config.getSecurePortEnabled())
.setVIPAddress(config.getVirtualHostName())
.setSecureVIPAddress(config.getSecureVirtualHostName())
.setHomePageUrl(config.getHomePageUrlPath(), config.getHomePageUrl())
.setStatusPageUrl(config.getStatusPageUrlPath(), config.getStatusPageUrl())
.setASGName(config.getASGName())
.setHealthCheckUrls(config.getHealthCheckUrlPath(),
config.getHealthCheckUrl(), config.getSecureHealthCheckUrl());
4.基于instanceConfig(实例配置)和instanceInfo(实例信息)，创建了applicationInfoManager(服务实例管理器)
public ApplicationInfoManager(EurekaInstanceConfig config, InstanceInfo instanceInfo) {
this(config, instanceInfo, null);
}
applicationInfoManager = new ApplicationInfoManager(
instanceConfig, new EurekaConfigBasedInstanceInfoProvider(instanceConfig).get());
下面来看看eureka client的初始化过程:
1.获取EurekaClientConfig,InstanceInfo,并保存
2.处理是否要拉取注册表和向其他实例注册，不需要的话就释放一些资源
3.创建支持调度的线程池，支持心跳的线程池，支持缓存刷新的线程池
4.创建EurekaTransport，用于eureka-server和eureka-client网络通信的组件
5.如果要拉取注册表，就拉取注册表
6.初始化调度任务:如果要拉取注册表就创建一个cacheRefreshTask，每隔一段时间(默认30s),更新缓存。如果要向eureka server注册的话，就创建一个heartbeatTask，每隔一段时间发送心跳。创建实例信息副本，创建实例状态监听器
eurekaClient = new DiscoveryClient(applicationInfoManager, eurekaClientConfig);
@Inject
DiscoveryClient(ApplicationInfoManager applicationInfoManager, EurekaClientConfig config, AbstractDiscoveryClientOptionalArgs args,
Provider<BackupRegistry> backupRegistryProvider, EndpointRandomizer endpointRandomizer) {
if (args != null) {
this.healthCheckHandlerProvider = args.healthCheckHandlerProvider;
this.healthCheckCallbackProvider = args.healthCheckCallbackProvider;
this.eventListeners.addAll(args.getEventListeners());
this.preRegistrationHandler = args.preRegistrationHandler;
} else {
this.healthCheckCallbackProvider = null;
this.healthCheckHandlerProvider = null;
this.preRegistrationHandler = null;
}
this.applicationInfoManager = applicationInfoManager;
InstanceInfo myInfo = applicationInfoManager.getInfo();
clientConfig = config;
staticClientConfig = clientConfig;
transportConfig = config.getTransportConfig();
instanceInfo = myInfo;
if (myInfo != null) {
//例如 orderService/001
appPathIdentifier = instanceInfo.getAppName() + "/" + instanceInfo.getId();
} else {
logger.warn("Setting instanceInfo to a passed in null value");
}
this.backupRegistryProvider = backupRegistryProvider;
this.endpointRandomizer = endpointRandomizer;
this.urlRandomizer = new EndpointUtils.InstanceInfoBasedUrlRandomizer(instanceInfo);
localRegionApps.set(new Applications());
fetchRegistryGeneration = new AtomicLong(0);
remoteRegionsToFetch = new AtomicReference<String>(clientConfig.fetchRegistryForRemoteRegions());
remoteRegionsRef = new AtomicReference<>(remoteRegionsToFetch.get() == null ? null : remoteRegionsToFetch.get().split(","));
if (config.shouldFetchRegistry()) {
this.registryStalenessMonitor = new ThresholdLevelsMetric(this, METRIC_REGISTRY_PREFIX + "lastUpdateSec_", new long[]{15L, 30L, 60L, 120L, 240L, 480L});
} else {
this.registryStalenessMonitor = ThresholdLevelsMetric.NO_OP_METRIC;
}
if (config.shouldRegisterWithEureka()) {
this.heartbeatStalenessMonitor = new ThresholdLevelsMetric(this, METRIC_REGISTRATION_PREFIX + "lastHeartbeatSec_", new long[]{15L, 30L, 60L, 120L, 240L, 480L});
} else {
this.heartbeatStalenessMonitor = ThresholdLevelsMetric.NO_OP_METRIC;
}
logger.info("Initializing Eureka in region {}", clientConfig.getRegion());
//如果不需要拉取注册表和向其他实例注册的话，就释放一些资源
if (!config.shouldRegisterWithEureka() && !config.shouldFetchRegistry()) {
logger.info("Client configured to neither register nor query for data.");
scheduler = null;
heartbeatExecutor = null;
cacheRefreshExecutor = null;
eurekaTransport = null;
instanceRegionChecker = new InstanceRegionChecker(new PropertyBasedAzToRegionMapper(config), clientConfig.getRegion());
// This is a bit of hack to allow for existing code using DiscoveryManager.getInstance()
// to work with DI'd DiscoveryClient
DiscoveryManager.getInstance().setDiscoveryClient(this);
DiscoveryManager.getInstance().setEurekaClientConfig(config);
initTimestampMs = System.currentTimeMillis();
logger.info("Discovery Client initialized at timestamp {} with initial instances count: {}",
initTimestampMs, this.getApplications().size());
return; // no need to setup up an network tasks and we are done
}
try {
// default size of 2 - 1 each for heartbeat and cacheRefresh
scheduler = Executors.newScheduledThreadPool(2,
new ThreadFactoryBuilder()
.setNameFormat("DiscoveryClient-%d")
.setDaemon(true)
.build());
heartbeatExecutor = new ThreadPoolExecutor(
1, clientConfig.getHeartbeatExecutorThreadPoolSize(), 0, TimeUnit.SECONDS,
new SynchronousQueue<Runnable>(),
new ThreadFactoryBuilder()
.setNameFormat("DiscoveryClient-HeartbeatExecutor-%d")
.setDaemon(true)
.build()
); // use direct handoff
cacheRefreshExecutor = new ThreadPoolExecutor(
1, clientConfig.getCacheRefreshExecutorThreadPoolSize(), 0, TimeUnit.SECONDS,
new SynchronousQueue<Runnable>(),
new ThreadFactoryBuilder()
.setNameFormat("DiscoveryClient-CacheRefreshExecutor-%d")
.setDaemon(true)
.build()
); // use direct handoff
eurekaTransport = new EurekaTransport();
scheduleServerEndpointTask(eurekaTransport, args);
AzToRegionMapper azToRegionMapper;
if (clientConfig.shouldUseDnsForFetchingServiceUrls()) {
azToRegionMapper = new DNSBasedAzToRegionMapper(clientConfig);
} else {
azToRegionMapper = new PropertyBasedAzToRegionMapper(clientConfig);
}
if (null != remoteRegionsToFetch.get()) {
azToRegionMapper.setRegionsToFetch(remoteRegionsToFetch.get().split(","));
}
instanceRegionChecker = new InstanceRegionChecker(azToRegionMapper, clientConfig.getRegion());
} catch (Throwable e) {
throw new RuntimeException("Failed to initialize DiscoveryClient!", e);
}
//抓取注册表
if (clientConfig.shouldFetchRegistry() && !fetchRegistry(false)) {
fetchRegistryFromBackup();
}
// call and execute the pre registration handler before all background tasks (inc registration) is started
if (this.preRegistrationHandler != null) {
this.preRegistrationHandler.beforeRegistration();
}
if (clientConfig.shouldRegisterWithEureka() && clientConfig.shouldEnforceRegistrationAtInit()) {
try {
if (!register() ) {
throw new IllegalStateException("Registration error at startup. Invalid server response.");
}
} catch (Throwable th) {
logger.error("Registration error at startup: {}", th.getMessage());
throw new IllegalStateException(th);
}
}
// finally, init the schedule tasks (e.g. cluster resolvers, heartbeat, instanceInfo replicator, fetch
//初始化调度任务
initScheduledTasks();
try {
Monitors.registerObject(this);
} catch (Throwable e) {
logger.warn("Cannot register timers", e);
}
// This is a bit of hack to allow for existing code using DiscoveryManager.getInstance()
// to work with DI'd DiscoveryClient
DiscoveryManager.getInstance().setDiscoveryClient(this);
DiscoveryManager.getInstance().setEurekaClientConfig(config);
initTimestampMs = System.currentTimeMillis();
logger.info("Discovery Client initialized at timestamp {} with initial instances count: {}",
initTimestampMs, this.getApplications().size());
}
最后总结:
Eureka-server启动初始化步骤:
1.构建Eureka-server环境(dataCenter和environment)
2.构建Eureka-server上下文
2.1 加载eureka-server.properties配置
2.2 把自己当作一个服务实例，加载eureka-client.properties配置，构建InstanceInfo,基于InstanceInfo和EurekaInstanceConfig构建ApplicationManager
2.3 把自己当作一个eureka client,由eureka-client.properties的client配置和ApplicationManager构建EurekaClient(DiscoveryClient)
2.4 构建感知eureka-server集群的注册表 PeerAwareInstanceRegistry
2.5 构建eureka-server集群信息 PeerEurekaNodes
2.6 基于eureka server配置，注册表，eureka server集群，服务实例构建eureka server上下文 EurekaServerContext
2.7 EurekaServerContext初始化 更新eureka server集群信息和初始化注册表
2.8 从相邻节点同步注册表
2.9 注册监控
