pom依赖
服务端
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
</dependency>
客户端
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>
服务注册
EurekaClientAutoConfiguration客户端自动装配
@Bean
@ConditionalOnBean(AutoServiceRegistrationProperties.class)
@ConditionalOnProperty(
value = "spring.cloud.service-registry.auto-registration.enabled",
matchIfMissing = true)
public EurekaAutoServiceRegistration eurekaAutoServiceRegistration(
ApplicationContext context, EurekaServiceRegistry registry,
EurekaRegistration registration) {
return new EurekaAutoServiceRegistration(context, registry, registration);
}
@Configuration(proxyBeanMethods = false)
@ConditionalOnMissingRefreshScope
protected static class EurekaClientConfiguration {
@Autowired
private ApplicationContext context;
@Autowired
private AbstractDiscoveryClientOptionalArgs<?> optionalArgs;
@Bean(destroyMethod = "shutdown")
@ConditionalOnMissingBean(value = EurekaClient.class,
search = SearchStrategy.CURRENT)
public EurekaClient eurekaClient(ApplicationInfoManager manager,
EurekaClientConfig config) {
return new CloudEurekaClient(manager, config, this.optionalArgs,
this.context);
}
@Bean
@ConditionalOnMissingBean(value = ApplicationInfoManager.class,
search = SearchStrategy.CURRENT)
public ApplicationInfoManager eurekaApplicationInfoManager(
EurekaInstanceConfig config) {
InstanceInfo instanceInfo = new InstanceInfoFactory().create(config);
return new ApplicationInfoManager(config, instanceInfo);
}
@Bean
@ConditionalOnBean(AutoServiceRegistrationProperties.class)
@ConditionalOnProperty(
value = "spring.cloud.service-registry.auto-registration.enabled",
matchIfMissing = true)
public EurekaRegistration eurekaRegistration(EurekaClient eurekaClient,
CloudEurekaInstanceConfig instanceConfig,
ApplicationInfoManager applicationInfoManager, @Autowired(
required = false) ObjectProvider<HealthCheckHandler> healthCheckHandler) {
return EurekaRegistration.builder(instanceConfig).with(applicationInfoManager)
.with(eurekaClient).with(healthCheckHandler).build();
}
}
EurekaAutoServiceRegistration这个先不讲埋个伏笔，CloudEurekaClient见名知意，eureka的客户端，那么看一下初始化过程。
public CloudEurekaClient(ApplicationInfoManager applicationInfoManager,
EurekaClientConfig config, AbstractDiscoveryClientOptionalArgs<?> args,
ApplicationEventPublisher publisher) {
super(applicationInfoManager, config, args);
this.applicationInfoManager = applicationInfoManager;
this.publisher = publisher;
this.eurekaTransportField = ReflectionUtils.findField(DiscoveryClient.class,
"eurekaTransport");
ReflectionUtils.makeAccessible(this.eurekaTransportField);
}
super(applicationInfoManager, config, args);调用父类的构造方法，而CloudEurekaClient的父类是 DiscoveryClient.
DiscoveryClient的最终构造方法有很长的初始化代码，其实很多代码可以不需要关心， 大部分都是一些初始化工作，比如初始化了几个定时任务。
重点步骤：
- scheduler
- heartbeatExecutor 心跳定时任务
- cacheRefreshExecutor 定时去同步服务端的实例列表
DiscoveryClient(ApplicationInfoManager applicationInfoManager, EurekaClientConfig config, AbstractDiscoveryClientOptionalArgs args,
Provider<BackupRegistry> backupRegistryProvider, EndpointRandomizer endpointRandomizer) {
//省略部分代码......
//是否要从eureka server上获取服务地址信息
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;
}
//是否要注册到eureka server上
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());
//如果不需要注册，并且不需要更新服务地址
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
//初始化scheduler
scheduler = Executors.newScheduledThreadPool(2,
new ThreadFactoryBuilder()
.setNameFormat("DiscoveryClient-%d")
.setDaemon(true)
.build());
//初始化心跳线程池
heartbeatExecutor = new ThreadPoolExecutor(
1, clientConfig.getHeartbeatExecutorThreadPoolSize(), 0, TimeUnit.SECONDS,
new SynchronousQueue<Runnable>(),
new ThreadFactoryBuilder()
.setNameFormat("DiscoveryClient-HeartbeatExecutor-%d")
.setDaemon(true)
.build()
); // use direct handoff
//初始化缓存刷新线程池
cacheRefreshExecutor = new ThreadPoolExecutor(
1, clientConfig.getCacheRefreshExecutorThreadPoolSize(), 0, TimeUnit.SECONDS,
new SynchronousQueue<Runnable>(),
new ThreadFactoryBuilder()
.setNameFormat("DiscoveryClient-CacheRefreshExecutor-%d")
.setDaemon(true)
.build()
); // use direct handoff
//创建通信连接
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);
}
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();
}
//如果需要注册到eureka server并且开启了初始化时强制注册，则调用register注册。
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schedule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());
}
initScheduledTasks去启动定时任务
private void initScheduledTasks() {
//如果配置了开启从注册中心刷新服务列表，则会开启cacheRefreshExecutor这个定时任务
if (clientConfig.shouldFetchRegistry()) {
// registry cache refresh timer
int registryFetchIntervalSeconds = clientConfig.getRegistryFetchIntervalSeconds();
int expBackOffBound = clientConfig.getCacheRefreshExecutorExponentialBackOffBound();
cacheRefreshTask = new TimedSupervisorTask(
"cacheRefresh",
scheduler,
cacheRefreshExecutor,
registryFetchIntervalSeconds,
TimeUnit.SECONDS,
expBackOffBound,
new CacheRefreshThread()
);
scheduler.schedule(
cacheRefreshTask,
registryFetchIntervalSeconds, TimeUnit.SECONDS);
}
//如果开启了服务注册到Eureka，则需要做几个事情
if (clientConfig.shouldRegisterWithEureka()) {
int renewalIntervalInSecs = instanceInfo.getLeaseInfo().getRenewalIntervalInSecs();
int expBackOffBound = clientConfig.getHeartbeatExecutorExponentialBackOffBound();
logger.info("Starting heartbeat executor: " + "renew interval is: {}", renewalIntervalInSecs);
// Heartbeat timer
//心跳任务
heartbeatTask = new TimedSupervisorTask(
"heartbeat",
scheduler,
heartbeatExecutor,
renewalIntervalInSecs,
TimeUnit.SECONDS,
expBackOffBound,
new HeartbeatThread()
);
scheduler.schedule(
heartbeatTask,
renewalIntervalInSecs, TimeUnit.SECONDS);
// InstanceInfo replicator
//初始化一个:instanceInfoReplicator
instanceInfoReplicator = new InstanceInfoReplicator(
this,
instanceInfo,
clientConfig.getInstanceInfoReplicationIntervalSeconds(),
2); // burstSize
statusChangeListener = new ApplicationInfoManager.StatusChangeListener() {
@Override
public String getId() {
return "statusChangeListener";
}
@Override
public void notify(StatusChangeEvent statusChangeEvent) {
if (InstanceStatus.DOWN == statusChangeEvent.getStatus() ||
InstanceStatus.DOWN == statusChangeEvent.getPreviousStatus()) {
// log at warn level if DOWN was involved
logger.warn("Saw local status change event {}", statusChangeEvent);
} else {
logger.info("Saw local status change event {}", statusChangeEvent);
}
instanceInfoReplicator.onDemandUpdate();
}
};
//注册实例状态变化的监听，伏笔中
if (clientConfig.shouldOnDemandUpdateStatusChange()) {
applicationInfoManager.registerStatusChangeListener(statusChangeListener);
}
//启动一个实例信息复制器，主要就是为了开启一个定时线程，每30秒判断实例信息是否变更，如果变更了则重新注册
instanceInfoReplicator.start(clientConfig.getInitialInstanceInfoReplicationIntervalSeconds());
} else {
logger.info("Not registering with Eureka server per configuration");
}
}
首先设置instanceInfo为脏数据，然后提交任务，在run中进行注册，并设置下次运行时间。
public void start(int initialDelayMs) {
if (started.compareAndSet(false, true)) {
instanceInfo.setIsDirty(); // for initial register
Future next = scheduler.schedule(this, initialDelayMs, TimeUnit.SECONDS);
scheduledPeriodicRef.set(next);
}
}
public void run() {
try {
discoveryClient.refreshInstanceInfo();
Long dirtyTimestamp = instanceInfo.isDirtyWithTime();
if (dirtyTimestamp != null) {
discoveryClient.register();
instanceInfo.unsetIsDirty(dirtyTimestamp);
}
} catch (Throwable t) {
logger.warn("There was a problem with the instance info replicator", t);
} finally {
Future next = scheduler.schedule(this, replicationIntervalSeconds, TimeUnit.SECONDS);
scheduledPeriodicRef.set(next);
}
}
DiscoveryClient.register
最终，我们终于找到服务注册的入口了， 最终调 用的是 AbstractJerseyEurekaHttpClient#register(...)
boolean register() throws Throwable {
logger.info(PREFIX + "{}: registering service...", appPathIdentifier);
EurekaHttpResponse<Void> httpResponse;
try {
httpResponse = eurekaTransport.registrationClient.register(instanceInfo);
} catch (Exception e) {
logger.warn(PREFIX + "{} - registration failed {}", appPathIdentifier, e.getMessage(), e);
throw e;
}
if (logger.isInfoEnabled()) {
logger.info(PREFIX + "{} - registration status: {}", appPathIdentifier, httpResponse.getStatusCode());
}
return httpResponse.getStatusCode() == Status.NO_CONTENT.getStatusCode();
}
AbstractJerseyEurekaHttpClient#register
很显然，这里是发起了一次http请求，访问Eureka-Server的apps/${APP_NAME}接口，将当前服务实 例的信息发送到Eureka Server进行保存。
至此，我们基本上已经知道Spring Cloud Eureka 是如何在启动的时候把服务信息注册到Eureka Server 上的了
public EurekaHttpResponse<Void> register(InstanceInfo info) {
String urlPath = "apps/" + info.getAppName();
ClientResponse response = null;
try {
Builder resourceBuilder = jerseyClient.resource(serviceUrl).path(urlPath).getRequestBuilder();
addExtraHeaders(resourceBuilder);
response = resourceBuilder
.header("Accept-Encoding", "gzip")
.type(MediaType.APPLICATION_JSON_TYPE)
.accept(MediaType.APPLICATION_JSON)
.post(ClientResponse.class, info);
return anEurekaHttpResponse(response.getStatus()).headers(headersOf(response)).build();
} finally {
if (logger.isDebugEnabled()) {
logger.debug("Jersey HTTP POST {}/{} with instance {}; statusCode={}", serviceUrl, urlPath, info.getId(),
response == null ? "N/A" : response.getStatus());
}
if (response != null) {
response.close();
}
}
}
目前来看服务注册的流程应该差不多完结了，但是伏笔呢，在哪里解开？
EurekaAutoServiceRegistration经过自动注册，注册到了Spring容器中，而这个EurekaAutoServiceRegistration实现了SmartLifecycle接口，针对这个借口，Spring启动时会调用该接口的start方法。
SpringApplication.run() -> this.refreshContext(context);-
>this.refresh(context);->ServletWebServerApplicationContext.refresh()-
>this.finishRefresh();->AbstractApplicationContext.finishRefresh-
>DefaultLifecycleProcessor.onRefresh()-> this.startBeans->this.start()-
>this.doStart()->
我们观察一下finishRefresh这个方法，从名字上可以看到它是用来体现完成刷新的操作，也就是刷新完 成之后要做的后置的操作。它主要做几个事情
- 清空缓存
- 初始化一个LifecycleProcessor，在Spring启动的时候启动bean，在spring结束的时候销毁bean
- 调用LifecycleProcessor的onRefresh方法，启动实现了Lifecycle接口的bean
- 发布ContextRefreshedEvent
- 注册MBean，通过JMX进行监控和管理
protected void finishRefresh() {
// Clear context-level resource caches (such as ASM metadata from scanning).
clearResourceCaches();
// Initialize lifecycle processor for this context.
initLifecycleProcessor();
// Propagate refresh to lifecycle processor first.
getLifecycleProcessor().onRefresh();
// Publish the final event.
publishEvent(new ContextRefreshedEvent(this));
// Participate in LiveBeansView MBean, if active.
LiveBeansView.registerApplicationContext(this);
}
在这个方法中，我们重点关注 getLifecycleProcessor().onRefresh() ，它是调用生命周期处理器 的onrefresh方法，找到SmartLifecycle接口的所有实现类并调用start方法。
后续的调用链路为:DefaultLifecycleProcessor.startBean -> start() -> doStart() -> bean.start()
EurekaAutoServiceRegistration
public void start() {
// only set the port if the nonSecurePort or securePort is 0 and this.port != 0
if (this.port.get() != 0) {
if (this.registration.getNonSecurePort() == 0) {
this.registration.setNonSecurePort(this.port.get());
}
if (this.registration.getSecurePort() == 0 && this.registration.isSecure()) {
this.registration.setSecurePort(this.port.get());
}
}
// only initialize if nonSecurePort is greater than 0 and it isn't already running
// because of containerPortInitializer below
if (!this.running.get() && this.registration.getNonSecurePort() > 0) {
this.serviceRegistry.register(this.registration);
this.context.publishEvent(new InstanceRegisteredEvent<>(this,
this.registration.getInstanceConfig()));
this.running.set(true);
}
}
在start方法中，我们可以看到 this.serviceRegistry.register 这个方法，它实际上就是发起服务 注册的机制。
此时this.serviceRegistry的实例，应该是 EurekaServiceRegistry ， 原因是 EurekaAutoServiceRegistration的构造方法中，会有一个赋值操作，而这个构造方法是在EurekaClientAutoConfiguration 这个自动装配类中被装配和初始化的
this.serviceRegistry.register(this.registration); 方法最终会调用 EurekaServiceRegistry 类中的 register 方法来实现服务注册。
public void register(EurekaRegistration reg) {
maybeInitializeClient(reg);
if (log.isInfoEnabled()) {
log.info("Registering application "
+ reg.getApplicationInfoManager().getInfo().getAppName()
+ " with eureka with status "
+ reg.getInstanceConfig().getInitialStatus());
}
//设置当前实例的状态，一旦这个实例的状态发生变化，只要状态不是DOWN，那么就会被监听器监听并 且执行服务注册。
reg.getApplicationInfoManager()
.setInstanceStatus(reg.getInstanceConfig().getInitialStatus());
//设置健康检查的处理
reg.getHealthCheckHandler().ifAvailable(healthCheckHandler -> reg
.getEurekaClient().registerHealthCheck(healthCheckHandler));
}
从上述代码来看，注册方法中并没有真正调用Eureka的方法去执行注册，而是仅仅设置了一个状态以及 设置健康检查处理器。我们继续看一下reg.getApplicationInfoManager().setInstanceStatus方法。
public synchronized void setInstanceStatus(InstanceStatus status) {
InstanceStatus next = instanceStatusMapper.map(status);
if (next == null) {
return;
}
InstanceStatus prev = instanceInfo.setStatus(next);
if (prev != null) {
for (StatusChangeListener listener : listeners.values()) {
try {
listener.notify(new StatusChangeEvent(prev, next));
} catch (Exception e) {
logger.warn("failed to notify listener: {}", listener.getId(), e);
}
}
}
}
在这个方法中，它会通过监听器来发布一个状态变更事件。ok，此时listener的实例是 StatusChangeListener ，也就是调用 StatusChangeListener 的notify方法。这个事件是触发一个服
务状态变更，那么我们在DiscoveryClient中初始化的匿名内部类statusChangeListener就会被调动。
statusChangeListener = new ApplicationInfoManager.StatusChangeListener() {
@Override
public String getId() {
return "statusChangeListener";
}
@Override
public void notify(StatusChangeEvent statusChangeEvent) {
if (InstanceStatus.DOWN == statusChangeEvent.getStatus() ||
InstanceStatus.DOWN == statusChangeEvent.getPreviousStatus()) {
// log at warn level if DOWN was involved
logger.warn("Saw local status change event {}", statusChangeEvent);
} else {
logger.info("Saw local status change event {}", statusChangeEvent);
}
instanceInfoReplicator.onDemandUpdate();
}
};
那么实例信息复制器instanceInfoReplicator会调用onDemandUpdate方法。
public boolean onDemandUpdate() {
if (rateLimiter.acquire(burstSize, allowedRatePerMinute)) {
if (!scheduler.isShutdown()) {
scheduler.submit(new Runnable() {
@Override
public void run() {
logger.debug("Executing on-demand update of local InstanceInfo");
//取出之前已经提交的任务，也就是在start方法中提交的更新任务，如果任务还 没有执行完成，则取消之前的任务。
Future latestPeriodic = scheduledPeriodicRef.get();
if (latestPeriodic != null && !latestPeriodic.isDone()) {
logger.debug("Canceling the latest scheduled update, it will be rescheduled at the end of on demand update");
latestPeriodic.cancel(false);//如果此任务未完成，就立即取消
}
//通过调用run方法，令任务在延时后执行，相当于周期性任务中的一次
InstanceInfoReplicator.this.run();
}
});
return true;
} else {
logger.warn("Ignoring onDemand update due to stopped scheduler");
return false;
}
} else {
logger.warn("Ignoring onDemand update due to rate limiter");
return false;
}
}
最终依然时调用run方法，进行实例信息注册
public void run() {
try {
discoveryClient.refreshInstanceInfo();
Long dirtyTimestamp = instanceInfo.isDirtyWithTime();
if (dirtyTimestamp != null) {
discoveryClient.register();
instanceInfo.unsetIsDirty(dirtyTimestamp);
}
} catch (Throwable t) {
logger.warn("There was a problem with the instance info replicator", t);
} finally {
Future next = scheduler.schedule(this, replicationIntervalSeconds, TimeUnit.SECONDS);
scheduledPeriodicRef.set(next);
}
}
注册总结：
至此，我们知道Eureka Client发起服务注册时，有两个地方会执行服务注册的任务
1.至此，我们知道Eureka Client发起服务注册时，有两个地方会执行服务注册的任务
2.在Spring Boot启动时，通过refresh方法，最终调用StatusChangeListener.notify进行服务状态变 更的监听，而这个监听的方法受到事件之后会去执行服务注册。
eureka收到请求后的处理
在没分析源码实现之前，我们一定知道它肯定对请求过来的服务实例数据进行了存储。那么我们去
Eureka Server端看一下处理流程。
请求入口在: com.netflix.eureka.resources.ApplicationResource.addInstance() 。
大家可以发现，这里所提供的REST服务，采用的是jersey来实现的。Jersey是基于JAX-RS标准，提供 REST的实现的支持，这里就不展开分析了。
ApplicationResource.addInstance()
@POST
@Consumes({"application/json", "application/xml"})
public Response addInstance(InstanceInfo info,
@HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication) {
logger.debug("Registering instance {} (replication={})", info.getId(), isReplication);
// validate that the instanceinfo contains all the necessary required fields
if (isBlank(info.getId())) {
return Response.status(400).entity("Missing instanceId").build();
} else if (isBlank(info.getHostName())) {
return Response.status(400).entity("Missing hostname").build();
} else if (isBlank(info.getIPAddr())) {
return Response.status(400).entity("Missing ip address").build();
} else if (isBlank(info.getAppName())) {
return Response.status(400).entity("Missing appName").build();
} else if (!appName.equals(info.getAppName())) {
return Response.status(400).entity("Mismatched appName, expecting " + appName + " but was " + info.getAppName()).build();
} else if (info.getDataCenterInfo() == null) {
return Response.status(400).entity("Missing dataCenterInfo").build();
} else if (info.getDataCenterInfo().getName() == null) {
return Response.status(400).entity("Missing dataCenterInfo Name").build();
}
// handle cases where clients may be registering with bad DataCenterInfo with missing data
DataCenterInfo dataCenterInfo = info.getDataCenterInfo();
if (dataCenterInfo instanceof UniqueIdentifier) {
String dataCenterInfoId = ((UniqueIdentifier) dataCenterInfo).getId();
if (isBlank(dataCenterInfoId)) {
boolean experimental = "true".equalsIgnoreCase(serverConfig.getExperimental("registration.validation.dataCenterInfoId"));
if (experimental) {
String entity = "DataCenterInfo of type " + dataCenterInfo.getClass() + " must contain a valid id";
return Response.status(400).entity(entity).build();
} else if (dataCenterInfo instanceof AmazonInfo) {
AmazonInfo amazonInfo = (AmazonInfo) dataCenterInfo;
String effectiveId = amazonInfo.get(AmazonInfo.MetaDataKey.instanceId);
if (effectiveId == null) {
amazonInfo.getMetadata().put(AmazonInfo.MetaDataKey.instanceId.getName(), info.getId());
}
} else {
logger.warn("Registering DataCenterInfo of type {} without an appropriate id", dataCenterInfo.getClass());
}
}
}
registry.register(info, "true".equals(isReplication));
return Response.status(204).build(); // 204 to be backwards compatible
}
PeerAwareInstanceRegistryImpl.register
我们先来看PeerAwareInstanceRegistryImpl的类关系图，从类关系图可以看出， PeerAwareInstanceRegistry的最顶层接口为LeaseManager与LookupService
eurekaserver.jpg
- 其中LookupService定义了最基本的发现示例的行为
- LeaseManager定义了处理客户端注册，续约，注销等操作
在 addInstance 方法中，最终调用的是 PeerAwareInstanceRegistryImpl.register 方法。
- leaseDuration 表示租约过期时间，默认是90s，也就是当服务端超过90s没有收到客户端的心 跳，则主动剔除该节点
- 调用super.register发起节点注册
- 将信息复制到Eureka Server集群中的其他机器上，同步的实现也很简单，就是获得集群中的所有 节点，然后逐个发起注册
public void register(final InstanceInfo info, final boolean isReplication) {
int leaseDuration = Lease.DEFAULT_DURATION_IN_SECS;
if (info.getLeaseInfo() != null && info.getLeaseInfo().getDurationInSecs() > 0) {
leaseDuration = info.getLeaseInfo().getDurationInSecs();//如果客户端有自己 定义心跳超时时间，则采用客户端的时间
}
super.register(info, leaseDuration, isReplication);//节点注册
//复制到Eureka Server集群中的其他节点
replicateToPeers(Action.Register, info.getAppName(), info.getId(), info, null, isReplication);
}
AbstractInstanceRegistry.register
简单来说，Eureka-Server的服务注册，实际上是将客户端传递过来的实例数据保存到Eureka-Server中 的ConcurrentHashMap中。
public void register(InstanceInfo registrant, int leaseDuration, boolean isReplication) {
try {
read.lock();
//从registry中获得当前实例信息，根据appName
Map<String, Lease<InstanceInfo>> gMap = registry.get(registrant.getAppName());
REGISTER.increment(isReplication);//增加注册次数到监控信息中
if (gMap == null) {//如果当前appName是第一次注册，则初始化一个 ConcurrentHashMap
final ConcurrentHashMap<String, Lease<InstanceInfo>> gNewMap = new ConcurrentHashMap<String, Lease<InstanceInfo>>();
gMap = registry.putIfAbsent(registrant.getAppName(), gNewMap);
if (gMap == null) {
gMap = gNewMap;
}
}
//从gMap中查询已经存在的Lease信息，Lease中文翻译为租约，实际上它把服务提供者的实例信 息包装成了一个lease，里面提供了对于改服务实例的租约管理
Lease<InstanceInfo> existingLease = gMap.get(registrant.getId());
// Retain the last dirty timestamp without overwriting it, if there is already a lease
// 当instance已经存在是，和客户端的instance的信息做比较，时间最新的那个，为有效 instance信息
if (existingLease != null && (existingLease.getHolder() != null)) {
Long existingLastDirtyTimestamp = existingLease.getHolder().getLastDirtyTimestamp();
Long registrationLastDirtyTimestamp = registrant.getLastDirtyTimestamp();
logger.debug("Existing lease found (existing={}, provided={}", existingLastDirtyTimestamp, registrationLastDirtyTimestamp);
// this is a > instead of a >= because if the timestamps are equal, we still take the remote transmitted
// InstanceInfo instead of the server local copy.
if (existingLastDirtyTimestamp > registrationLastDirtyTimestamp) {
logger.warn("There is an existing lease and the existing lease's dirty timestamp {} is greater" +
" than the one that is being registered {}", existingLastDirtyTimestamp, registrationLastDirtyTimestamp);
logger.warn("Using the existing instanceInfo instead of the new instanceInfo as the registrant");
registrant = existingLease.getHolder();
}
} else {
// The lease does not exist and hence it is a new registration
//当lease不存在时，进入到这段代码
synchronized (lock) {
if (this.expectedNumberOfClientsSendingRenews > 0) {
// Since the client wants to register it, increase the number of clients sending renews
this.expectedNumberOfClientsSendingRenews = this.expectedNumberOfClientsSendingRenews + 1;
updateRenewsPerMinThreshold();
}
}
logger.debug("No previous lease information found; it is new registration");
}
//构建一个lease
Lease<InstanceInfo> lease = new Lease<InstanceInfo>(registrant, leaseDuration);
// 当原来存在Lease的信息时，设置serviceUpTimestamp, 保证服务启动的时间一直是
第一次注册的那个
if (existingLease != null) {
lease.setServiceUpTimestamp(existingLease.getServiceUpTimestamp());
}
gMap.put(registrant.getId(), lease);
recentRegisteredQueue.add(new Pair<Long, String>(//添加到最近注册的队列中
System.currentTimeMillis(),
registrant.getAppName() + "(" + registrant.getId() + ")"));
// This is where the initial state transfer of overridden status happens
//// 检查实例状态是否发生变化，如果是并且存在，则覆盖原来的状态
if (!InstanceStatus.UNKNOWN.equals(registrant.getOverriddenStatus())) {
logger.debug("Found overridden status {} for instance {}. Checking to see if needs to be add to the "
+ "overrides", registrant.getOverriddenStatus(), registrant.getId());
if (!overriddenInstanceStatusMap.containsKey(registrant.getId())) {
logger.info("Not found overridden id {} and hence adding it", registrant.getId());
overriddenInstanceStatusMap.put(registrant.getId(), registrant.getOverriddenStatus());
}
}
InstanceStatus overriddenStatusFromMap = overriddenInstanceStatusMap.get(registrant.getId());
if (overriddenStatusFromMap != null) {
logger.info("Storing overridden status {} from map", overriddenStatusFromMap);
registrant.setOverriddenStatus(overriddenStatusFromMap);
}
// Set the status based on the overridden status rules
InstanceStatus overriddenInstanceStatus = getOverriddenInstanceStatus(registrant, existingLease, isReplication);
registrant.setStatusWithoutDirty(overriddenInstanceStatus);
// If the lease is registered with UP status, set lease service up timestamp
// 得到instanceStatus，判断是否是UP状态，
if (InstanceStatus.UP.equals(registrant.getStatus())) {
lease.serviceUp();
}
// 设置注册类型为添加
registrant.setActionType(ActionType.ADDED);
// 租约变更记录队列，记录了实例的每次变化， 用于注册信息的增量获取
recentlyChangedQueue.add(new RecentlyChangedItem(lease));
registrant.setLastUpdatedTimestamp();
//让缓存失效
invalidateCache(registrant.getAppName(), registrant.getVIPAddress(), registrant.getSecureVipAddress());
logger.info("Registered instance {}/{} with status {} (replication={})",
registrant.getAppName(), registrant.getId(), registrant.getStatus(), isReplication);
} finally {
read.unlock();
}
}
至此，我们就把服务注册在客户端和服务端的处理过程做了一个详细的分析，实际上在Eureka Server 端，会把客户端的地址信息保存到ConcurrentHashMap中存储。并且服务提供者和注册中心之间，会 建立一个心跳检测机制。
用于监控服务提供者的健康状态。
Eureka 的多级缓存设计
Eureka Server存在三个变量:(registry、readWriteCacheMap、readOnlyCacheMap)保存服务注 册信息，默认情况下定时任务每30s将readWriteCacheMap同步至readOnlyCacheMap，每60s清理超 过90s未续约的节点，Eureka Client每30s从readOnlyCacheMap更新服务注册信息，而客户端服务的 注册则从registry更新服务注册信息。
多级缓存的意义
这里为什么要设计多级缓存呢?原因很简单，就是当存在大规模的服务注册和更新时，如果只是修改一 个ConcurrentHashMap数据，那么势必因为锁的存在导致竞争，影响性能。
而Eureka又是AP模型，只需要满足最终可用就行。所以它在这里用到多级缓存来实现读写分离。注册方法写的时候直接写内存注册表，写完表之后主动失效读写缓存。
获取注册信息接口先从只读缓存取，只读缓存没有再去读写缓存取，读写缓存没有再去内存注册表里取
(不只是取，此处较复杂)。并且，读写缓存会更新回写只读缓存
- responseCacheUpdateIntervalMs : readOnlyCacheMap 缓存更新的定时器时间间隔，默认为 30秒
- responseCacheAutoExpirationInSeconds : readWriteCacheMap 缓存过期时间，默认为 180 秒 。
服务注册的缓存失效
在AbstractInstanceRegistry.register方法的最后，会调用 方法invalidateCache(registrant.getAppName(), registrant.getVIPAddress(), registrant.getSecureVipAddress());使得读写缓存失效。
public void invalidate(String appName, @Nullable String vipAddress, @Nullable String secureVipAddress) {
for (Key.KeyType type : Key.KeyType.values()) {
for (Version v : Version.values()) {
invalidate(
new Key(Key.EntityType.Application, appName, type, v, EurekaAccept.full),
new Key(Key.EntityType.Application, appName, type, v, EurekaAccept.compact),
new Key(Key.EntityType.Application, ALL_APPS, type, v, EurekaAccept.full),
new Key(Key.EntityType.Application, ALL_APPS, type, v, EurekaAccept.compact),
new Key(Key.EntityType.Application, ALL_APPS_DELTA, type, v, EurekaAccept.full),
new Key(Key.EntityType.Application, ALL_APPS_DELTA, type, v, EurekaAccept.compact)
);
if (null != vipAddress) {
invalidate(new Key(Key.EntityType.VIP, vipAddress, type, v, EurekaAccept.full));
}
if (null != secureVipAddress) {
invalidate(new Key(Key.EntityType.SVIP, secureVipAddress, type, v, EurekaAccept.full));
}
}
}
}
定时同步缓存
ResponseCacheImpl的构造方法中，会启动一个定时任务，这个任务会定时检查写缓存中的数据变 化，进行更新和同步。
private TimerTask getCacheUpdateTask() {
return new TimerTask() {
@Override
public void run() {
logger.debug("Updating the client cache from response cache");
for (Key key : readOnlyCacheMap.keySet()) {
if (logger.isDebugEnabled()) {
logger.debug("Updating the client cache from response cache for key : {} {} {} {}",
key.getEntityType(), key.getName(), key.getVersion(), key.getType());
}
try {
CurrentRequestVersion.set(key.getVersion());
Value cacheValue = readWriteCacheMap.get(key);
Value currentCacheValue = readOnlyCacheMap.get(key);
if (cacheValue != currentCacheValue) {
readOnlyCacheMap.put(key, cacheValue);
}
} catch (Throwable th) {
logger.error("Error while updating the client cache from response cache for key {}", key.toStringCompact(), th);
} finally {
CurrentRequestVersion.remove();
}
}
}
};
服务续约
所谓的服务续约，其实就是一种心跳检查机制。客户端会定期发送心跳来续约。那么简单给大家看一下
代码的实现
DiscoveryClient.initScheduledTasks
客户端会在 initScheduledTasks 中，创建一个心跳检测的定时任务
// Heartbeat timer
heartbeatTask = new TimedSupervisorTask(
"heartbeat",
scheduler,
heartbeatExecutor,
renewalIntervalInSecs,
TimeUnit.SECONDS,
expBackOffBound,
new HeartbeatThread()
);
scheduler.schedule(
heartbeatTask,
renewalIntervalInSecs, TimeUnit.SECONDS);
HeartbeatThread
然后这个定时任务中，会执行一个 HearbeatThread 的线程，这个线程会定时调用renew()来做续约。
private class HeartbeatThread implements Runnable {
public void run() {
if (renew()) {
lastSuccessfulHeartbeatTimestamp = System.currentTimeMillis();
}
}
}
后续就是发送http请求，很简单不赘述。
服务端收到心跳请求的处理
在ApplicationResource.getInstanceInfo这个接口中，会返回一个InstanceResource的实例，在该实例下，定义了一个statusUpdate的接口来更新状态
@Path("{id}")
public InstanceResource getInstanceInfo(@PathParam("id") String id) {
return new InstanceResource(this, id, serverConfig, registry);
}
InstanceResource.statusUpdate()
在该方法中，我们重点关注这个方法，它会调用 AbstractInstanceRegistry.statusUpdate来更新指定服务提供者在服务端存储的信息中的变化。
@PUT
@Path("status")
public Response statusUpdate(
@QueryParam("value") String newStatus,
@HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication,
@QueryParam("lastDirtyTimestamp") String lastDirtyTimestamp) {
try {
if (registry.getInstanceByAppAndId(app.getName(), id) == null) {
logger.warn("Instance not found: {}/{}", app.getName(), id);
return Response.status(Status.NOT_FOUND).build();
}
boolean isSuccess = registry.statusUpdate(app.getName(), id,
InstanceStatus.valueOf(newStatus), lastDirtyTimestamp,
"true".equals(isReplication));
if (isSuccess) {
logger.info("Status updated: {} - {} - {}", app.getName(), id, newStatus);
return Response.ok().build();
} else {
logger.warn("Unable to update status: {} - {} - {}", app.getName(), id, newStatus);
return Response.serverError().build();
}
} catch (Throwable e) {
logger.error("Error updating instance {} for status {}", id,
newStatus);
return Response.serverError().build();
}
}
AbstractInstanceRegistry.statusUpdate
在这个方法中，会拿到应用对应的实例列表，然后调用Lease.renew()去进行心跳续约。
public boolean statusUpdate(String appName, String id,
InstanceStatus newStatus, String lastDirtyTimestamp,
boolean isReplication) {
try {
read.lock();
// 更新状态的次数 状态统计
STATUS_UPDATE.increment(isReplication);
// 从本地数据里面获取实例信息，
Map<String, Lease<InstanceInfo>> gMap = registry.get(appName);
Lease<InstanceInfo> lease = null;
if (gMap != null) {
lease = gMap.get(id);
}
// 实例不存在，则直接返回，表示失败
if (lease == null) {
return false;
} else {
// 执行一下lease的renew方法，里面主要是更新了这个instance的最后更新时间。
lease.renew();
// 获取instance实例信息
InstanceInfo info = lease.getHolder();
// Lease is always created with its instance info object.
// This log statement is provided as a safeguard, in case this invariant is violated.
if (info == null) {
logger.error("Found Lease without a holder for instance id {}", id);
}
// 当instance信息不为空时，并且实例状态发生了变化
if ((info != null) && !(info.getStatus().equals(newStatus))) {
// Mark service as UP if needed
// 如果新状态是UP的状态，那么启动一下serviceUp() , 主要是更新服务的注册时间
if (InstanceStatus.UP.equals(newStatus)) {
lease.serviceUp();
}
// This is NAC overriden status
// 将instance Id 和这个状态的映射信息放入覆盖缓存MAP里面去
overriddenInstanceStatusMap.put(id, newStatus);
// Set it for transfer of overridden status to replica on
// replica start up
// 设置覆盖状态到实例信息里面去
info.setOverriddenStatus(newStatus);
long replicaDirtyTimestamp = 0;
info.setStatusWithoutDirty(newStatus);
if (lastDirtyTimestamp != null) {
replicaDirtyTimestamp = Long.valueOf(lastDirtyTimestamp);
}
// If the replication's dirty timestamp is more than the existing one, just update
// it to the replica's.
// 如果replicaDirtyTimestamp 的时间大于instance的 getLastDirtyTimestamp() ,则更新
if (replicaDirtyTimestamp > info.getLastDirtyTimestamp()) {
info.setLastDirtyTimestamp(replicaDirtyTimestamp);
}
info.setActionType(ActionType.MODIFIED);
recentlyChangedQueue.add(new RecentlyChangedItem(lease));
info.setLastUpdatedTimestamp();
//更新写缓存
invalidateCache(appName, info.getVIPAddress(), info.getSecureVipAddress());
}
return true;
}
} finally {
read.unlock();
}
}
至此，心跳续约功能就分析完成了。
服务发现
我们继续来研究服务的发现过程，就是客户端需要能够满足两个功能
- 在启动的时候获取指定服务提供者的地址列表
- Eureka server端地址发生变化时，需要动态感知
DiscoveryClient构造时进行查询
构造方法中，如果当前的客户端默认开启了fetchRegistry，则会从eureka-server中拉取数据。
if (clientConfig.shouldFetchRegistry() && !fetchRegistry(false)) {
fetchRegistryFromBackup();
}
DiscoveryClient.fetchRegistry
private boolean fetchRegistry(boolean forceFullRegistryFetch) {
Stopwatch tracer = FETCH_REGISTRY_TIMER.start();
try {
// If the delta is disabled or if it is the first time, get all
// applications
Applications applications = getApplications();
if (clientConfig.shouldDisableDelta()
|| (!Strings.isNullOrEmpty(clientConfig.getRegistryRefreshSingleVipAddress()))
|| forceFullRegistryFetch
|| (applications == null)
|| (applications.getRegisteredApplications().size() == 0)
|| (applications.getVersion() == -1)) //Client application does not have latest library supporting delta
{
logger.info("Disable delta property : {}", clientConfig.shouldDisableDelta());
logger.info("Single vip registry refresh property : {}", clientConfig.getRegistryRefreshSingleVipAddress());
logger.info("Force full registry fetch : {}", forceFullRegistryFetch);
logger.info("Application is null : {}", (applications == null));
logger.info("Registered Applications size is zero : {}",
(applications.getRegisteredApplications().size() == 0));
logger.info("Application version is -1: {}", (applications.getVersion() == -1));
getAndStoreFullRegistry();
} else {
getAndUpdateDelta(applications);
}
applications.setAppsHashCode(applications.getReconcileHashCode());
logTotalInstances();
} catch (Throwable e) {
logger.error(PREFIX + "{} - was unable to refresh its cache! status = {}", appPathIdentifier, e.getMessage(), e);
return false;
} finally {
if (tracer != null) {
tracer.stop();
}
}
// Notify about cache refresh before updating the instance remote status
onCacheRefreshed();
// Update remote status based on refreshed data held in the cache
updateInstanceRemoteStatus();
// registry was fetched successfully, so return true
return true;
}
定时任务每隔30s更新一次本地地址列表
在DiscoveryClient构造的时候，会初始化一些任务，这个在前面咱们分析过了。其中有一个任务动态
更新本地服务地址列表，叫 cacheRefreshTask 。 这个任务最终执行的是CacheRefreshThread这个线程。它是一个周期性执行的任务，具体我们来看一
下。
cacheRefreshTask = new TimedSupervisorTask(
"cacheRefresh",
scheduler,
cacheRefreshExecutor,
registryFetchIntervalSeconds,
TimeUnit.SECONDS,
expBackOffBound,
new CacheRefreshThread()
);
scheduler.schedule(
cacheRefreshTask,
registryFetchIntervalSeconds, TimeUnit.SECONDS);
TimedSupervisorTask
从整体上看，TimedSupervisorTask是固定间隔的周期性任务，一旦遇到超时就会将下一个周期的间隔 时间调大，如果连续超时，那么每次间隔时间都会增大一倍，一直到达外部参数设定的上限为止，一旦 新任务不再超时，间隔时间又会自动恢复为初始值。这种设计还是值得学习的。
@Override
public void run() {
Future<?> future = null;
try {
//使用Future，可以设定子线程的超时时间，这样当前线程就不用无限等待了
future = executor.submit(task);
threadPoolLevelGauge.set((long) executor.getActiveCount());
//指定等待子线程的最长时间
future.get(timeoutMillis, TimeUnit.MILLISECONDS); // block until done or timeout
//delay是个很有用的变量，后面会用到，这里记得每次执行任务成功都会将delay重置
delay.set(timeoutMillis);
threadPoolLevelGauge.set((long) executor.getActiveCount());
successCounter.increment();
} catch (TimeoutException e) {
logger.warn("task supervisor timed out", e);
timeoutCounter.increment();
long currentDelay = delay.get();
//任务线程超时的时候，就把delay变量翻倍，但不会超过外部调用时设定的最大延时时间
long newDelay = Math.min(maxDelay, currentDelay * 2);
//设置为最新的值，考虑到多线程，所以用了CAS
delay.compareAndSet(currentDelay, newDelay);
} catch (RejectedExecutionException e) {
//一旦线程池的阻塞队列中放满了待处理任务，触发了拒绝策略，就会将调度器停掉
if (executor.isShutdown() || scheduler.isShutdown()) {
logger.warn("task supervisor shutting down, reject the task", e);
} else {
logger.warn("task supervisor rejected the task", e);
}
rejectedCounter.increment();
} catch (Throwable e) {
//一旦出现未知的异常，就停掉调度器
if (executor.isShutdown() || scheduler.isShutdown()) {
logger.warn("task supervisor shutting down, can't accept the task");
} else {
logger.warn("task supervisor threw an exception", e);
}
throwableCounter.increment();
} finally {
//这里任务要么执行完毕，要么发生异常，都用cancel方法来清理任务
if (future != null) {
future.cancel(true);
}
//只要调度器没有停止，就再指定等待时间之后在执行一次同样的任务
if (!scheduler.isShutdown()) {
//这里就是周期性任务的原因:只要没有停止调度器，就再创建一次性任务，执行时间时dealy的值，
//假设外部调用时传入的超时时间为30秒(构造方法的入参timeout)，最大间隔时间为50 秒(构造方法的入参expBackOffBound)
//如果最近一次任务没有超时，那么就在30秒后开始新任务，
//如果最近一次任务超时了，那么就在50秒后开始新任务(异常处理中有个乘以二的操作， 乘以二后的60秒超过了最大间隔50秒)
scheduler.schedule(this, delay.get(), TimeUnit.MILLISECONDS);
}
}
}
CacheRefreshThread.refreshRegistry
这段代码主要两个逻辑
- 判断remoteRegions是否发生了变化
- 调用fetchRegistry获取本地服务地址缓存
void refreshRegistry() {
try {
boolean isFetchingRemoteRegionRegistries = isFetchingRemoteRegionRegistries();
boolean remoteRegionsModified = false;
// This makes sure that a dynamic change to remote regions to fetch is honored.
//如果部署在aws环境上，会判断最后一次远程区域更新的信息和当前远程区域信息进行比 较，如果不想等，则更新
String latestRemoteRegions = clientConfig.fetchRegistryForRemoteRegions();
if (null != latestRemoteRegions) {
String currentRemoteRegions = remoteRegionsToFetch.get();
if (!latestRemoteRegions.equals(currentRemoteRegions)) {
//判断最后一次
// Both remoteRegionsToFetch and AzToRegionMapper.regionsToFetch need to be in sync
synchronized (instanceRegionChecker.getAzToRegionMapper()) {
if (remoteRegionsToFetch.compareAndSet(currentRemoteRegions, latestRemoteRegions)) {
String[] remoteRegions = latestRemoteRegions.split(",");
remoteRegionsRef.set(remoteRegions);
instanceRegionChecker.getAzToRegionMapper().setRegionsToFetch(remoteRegions);
remoteRegionsModified = true;
} else {
logger.info("Remote regions to fetch modified concurrently," +
" ignoring change from {} to {}", currentRemoteRegions, latestRemoteRegions);
}
}
} else {
// Just refresh mapping to reflect any DNS/Property change
instanceRegionChecker.getAzToRegionMapper().refreshMapping();
}
}
boolean success = fetchRegistry(remoteRegionsModified);
if (success) {
registrySize = localRegionApps.get().size();
lastSuccessfulRegistryFetchTimestamp = System.currentTimeMillis();
}
if (logger.isDebugEnabled()) {
StringBuilder allAppsHashCodes = new StringBuilder();
allAppsHashCodes.append("Local region apps hashcode: ");
allAppsHashCodes.append(localRegionApps.get().getAppsHashCode());
allAppsHashCodes.append(", is fetching remote regions? ");
allAppsHashCodes.append(isFetchingRemoteRegionRegistries);
for (Map.Entry<String, Applications> entry : remoteRegionVsApps.entrySet()) {
allAppsHashCodes.append(", Remote region: ");
allAppsHashCodes.append(entry.getKey());
allAppsHashCodes.append(" , apps hashcode: ");
allAppsHashCodes.append(entry.getValue().getAppsHashCode());
}
logger.debug("Completed cache refresh task for discovery. All Apps hash code is {} ",
allAppsHashCodes);
}
} catch (Throwable e) {
logger.error("Cannot fetch registry from server", e);
}
}
DisccoveryClient.fetchRegistry
private boolean fetchRegistry(boolean forceFullRegistryFetch) {
Stopwatch tracer = FETCH_REGISTRY_TIMER.start();
try {
// If the delta is disabled or if it is the first time, get all
// applications
// 取出本地缓存的服务列表信息
Applications applications = getApplications();
//判断多个条件，确定是否触发全量更新，如下任一个满足都会全量更新: //1. 是否禁用增量更新;
//2. 是否对某个region特别关注;
//3. 外部调用时是否通过入参指定全量更新;
//4. 本地还未缓存有效的服务列表信息
if (clientConfig.shouldDisableDelta()
|| (!Strings.isNullOrEmpty(clientConfig.getRegistryRefreshSingleVipAddress()))
|| forceFullRegistryFetch
|| (applications == null)
|| (applications.getRegisteredApplications().size() == 0)
|| (applications.getVersion() == -1)) //Client application does not have latest library supporting delta
{
logger.info("Disable delta property : {}", clientConfig.shouldDisableDelta());
logger.info("Single vip registry refresh property : {}", clientConfig.getRegistryRefreshSingleVipAddress());
logger.info("Force full registry fetch : {}", forceFullRegistryFetch);
logger.info("Application is null : {}", (applications == null));
logger.info("Registered Applications size is zero : {}",
(applications.getRegisteredApplications().size() == 0));
logger.info("Application version is -1: {}", (applications.getVersion() == -1));
//调用全量更新
getAndStoreFullRegistry();
} else {
//调用增量更新
getAndUpdateDelta(applications);
}
//重新计算和设置一致性hash码
applications.setAppsHashCode(applications.getReconcileHashCode());
logTotalInstances();//日志打印所有应用的所有实例数之和
} catch (Throwable e) {
logger.error(PREFIX + "{} - was unable to refresh its cache! status = {}", appPathIdentifier, e.getMessage(), e);
return false;
} finally {
if (tracer != null) {
tracer.stop();
}
}
// Notify about cache refresh before updating the instance remote status
//将本地缓存更新的事件广播给所有已注册的监听器，注意该方法已被CloudEurekaClient类重写
onCacheRefreshed();
// Update remote status based on refreshed data held in the cache
// Update remote status based on refreshed data held in the cache //检查刚刚更新的缓存中，有来自Eureka server的服务列表，其中包含了当前应用的状态， //当前实例的成员变量lastRemoteInstanceStatus，记录的是最后一次更新的当前应用状态， //上述两种状态在updateInstanceRemoteStatus方法中作比较 ，如果不一致，就更新
lastRemoteInstanceStatus，并且广播对应的事件
updateInstanceRemoteStatus();
// registry was fetched successfully, so return true
return true;
}
DiscoveryClient.getAndStoreFullRegistry
从eureka server端获取服务注册中心的地址信息，然后更新并设置到本地缓存 localRegionApps 。
private void getAndStoreFullRegistry() throws Throwable {
long currentUpdateGeneration = fetchRegistryGeneration.get();
logger.info("Getting all instance registry info from the eureka server");
Applications apps = null;
EurekaHttpResponse<Applications> httpResponse = clientConfig.getRegistryRefreshSingleVipAddress() == null
? eurekaTransport.queryClient.getApplications(remoteRegionsRef.get())
: eurekaTransport.queryClient.getVip(clientConfig.getRegistryRefreshSingleVipAddress(), remoteRegionsRef.get());
if (httpResponse.getStatusCode() == Status.OK.getStatusCode()) {
apps = httpResponse.getEntity();
}
logger.info("The response status is {}", httpResponse.getStatusCode());
if (apps == null) {
logger.error("The application is null for some reason. Not storing this information");
} else if (fetchRegistryGeneration.compareAndSet(currentUpdateGeneration, currentUpdateGeneration + 1)) {
localRegionApps.set(this.filterAndShuffle(apps));
logger.debug("Got full registry with apps hashcode {}", apps.getAppsHashCode());
} else {
logger.warn("Not updating applications as another thread is updating it already");
}
}
服务端查询服务地址流程
前面我们知道，客户端发起服务地址的查询有两种，一种是全量、另一种是增量。对于全量查询请求， 会调用Eureka-server的ApplicationsResource的getContainers方法。
而对于增量请求，会调用ApplicationsResource.getContainerDifferential。
ApplicationsResource.getContainers
接收客户端发送的获取全量注册信息请求。
@GET
public Response getContainers(@PathParam("version") String version,
@HeaderParam(HEADER_ACCEPT) String acceptHeader,
@HeaderParam(HEADER_ACCEPT_ENCODING) String acceptEncoding,
@HeaderParam(EurekaAccept.HTTP_X_EUREKA_ACCEPT) String eurekaAccept,
@Context UriInfo uriInfo,
@Nullable @QueryParam("regions") String regionsStr) {
boolean isRemoteRegionRequested = null != regionsStr && !regionsStr.isEmpty();
String[] regions = null;
if (!isRemoteRegionRequested) {
EurekaMonitors.GET_ALL.increment();
} else {
regions = regionsStr.toLowerCase().split(",");
Arrays.sort(regions); // So we don't have different caches for same regions queried in different order.
EurekaMonitors.GET_ALL_WITH_REMOTE_REGIONS.increment();
}
// Check if the server allows the access to the registry. The server can
// restrict access if it is not
// ready to serve traffic depending on various reasons.
// EurekaServer无法提供服务，返回403
if (!registry.shouldAllowAccess(isRemoteRegionRequested)) {
return Response.status(Status.FORBIDDEN).build();
}
CurrentRequestVersion.set(Version.toEnum(version));
KeyType keyType = Key.KeyType.JSON;/ 设置返回数据格式，默认JSON
String returnMediaType = MediaType.APPLICATION_JSON;
if (acceptHeader == null || !acceptHeader.contains(HEADER_JSON_VALUE)) {
// 如果接收到的请求头部没有具体格式信息，则返回格式为XML
keyType = Key.KeyType.XML;
returnMediaType = MediaType.APPLICATION_XML;
}
// 构建缓存键
Key cacheKey = new Key(Key.EntityType.Application,
ResponseCacheImpl.ALL_APPS,
keyType, CurrentRequestVersion.get(), EurekaAccept.fromString(eurekaAccept), regions
);
// 返回不同的编码类型的数据，去缓存中取数据的方法基本一致
Response response;
if (acceptEncoding != null && acceptEncoding.contains(HEADER_GZIP_VALUE)) {
response = Response.ok(responseCache.getGZIP(cacheKey))
.header(HEADER_CONTENT_ENCODING, HEADER_GZIP_VALUE)
.header(HEADER_CONTENT_TYPE, returnMediaType)
.build();
} else {
response = Response.ok(responseCache.get(cacheKey))
.build();
}
CurrentRequestVersion.remove();
return response;
}
responseCache.getGZIP
从缓存中读取数据。
public byte[] getGZIP(Key key) {
Value payload = getValue(key, shouldUseReadOnlyResponseCache);
if (payload == null) {
return null;
}
return payload.getGzipped();
}
@VisibleForTesting
Value getValue(final Key key, boolean useReadOnlyCache) {
Value payload = null;
try {
if (useReadOnlyCache) {
final Value currentPayload = readOnlyCacheMap.get(key);
if (currentPayload != null) {
payload = currentPayload;
} else {
payload = readWriteCacheMap.get(key);
readOnlyCacheMap.put(key, payload);
}
} else {
payload = readWriteCacheMap.get(key);
}
} catch (Throwable t) {
logger.error("Cannot get value for key : {}", key, t);
}
return payload;
}
与ribbon结合
DynamicServerListLoadBalancer
public void updateListOfServers() {
List<T> servers = new ArrayList<T>();
if (serverListImpl != null) {
servers = serverListImpl.getUpdatedListOfServers();
LOGGER.debug("List of Servers for {} obtained from Discovery client: {}",
getIdentifier(), servers);
if (filter != null) {
servers = filter.getFilteredListOfServers(servers);
LOGGER.debug("Filtered List of Servers for {} obtained from Discovery client: {}",
getIdentifier(), servers);
}
}
updateAllServerList(servers);
}
serverListImpl使用eureka的实现DiscoveryEnabledNIWSServerList
public List<DiscoveryEnabledServer> getUpdatedListOfServers() {
return this.obtainServersViaDiscovery();
}
private List<DiscoveryEnabledServer> obtainServersViaDiscovery() {
List<DiscoveryEnabledServer> serverList = new ArrayList();
if (this.eurekaClientProvider != null && this.eurekaClientProvider.get() != null) {
EurekaClient eurekaClient = (EurekaClient)this.eurekaClientProvider.get();
if (this.vipAddresses != null) {
String[] var3 = this.vipAddresses.split(",");
int var4 = var3.length;
for(int var5 = 0; var5 < var4; ++var5) {
String vipAddress = var3[var5];
List<InstanceInfo> listOfInstanceInfo = eurekaClient.getInstancesByVipAddress(vipAddress, this.isSecure, this.targetRegion);
Iterator var8 = listOfInstanceInfo.iterator();
while(var8.hasNext()) {
InstanceInfo ii = (InstanceInfo)var8.next();
if (ii.getStatus().equals(InstanceStatus.UP)) {
if (this.shouldUseOverridePort) {
if (logger.isDebugEnabled()) {
logger.debug("Overriding port on client name: " + this.clientName + " to " + this.overridePort);
}
InstanceInfo copy = new InstanceInfo(ii);
if (this.isSecure) {
ii = (new Builder(copy)).setSecurePort(this.overridePort).build();
} else {
ii = (new Builder(copy)).setPort(this.overridePort).build();
}
}
DiscoveryEnabledServer des = this.createServer(ii, this.isSecure, this.shouldUseIpAddr);
serverList.add(des);
}
}
if (serverList.size() > 0 && this.prioritizeVipAddressBasedServers) {
break;
}
}
}
return serverList;
} else {
logger.warn("EurekaClient has not been initialized yet, returning an empty list");
return new ArrayList();
}
}
eurekaClient.getInstancesByVipAddress(vipAddress, this.isSecure, this.targetRegion);将从eurekaclient本地的服务缓存获取数据来更新自己的缓存。
private List<DiscoveryEnabledServer> obtainServersViaDiscovery() {
List<DiscoveryEnabledServer> serverList = new ArrayList();
if (this.eurekaClientProvider != null && this.eurekaClientProvider.get() != null) {
EurekaClient eurekaClient = (EurekaClient)this.eurekaClientProvider.get();
if (this.vipAddresses != null) {
String[] var3 = this.vipAddresses.split(",");
int var4 = var3.length;
for(int var5 = 0; var5 < var4; ++var5) {
String vipAddress = var3[var5];
List<InstanceInfo> listOfInstanceInfo = eurekaClient.getInstancesByVipAddress(vipAddress, this.isSecure, this.targetRegion);
Iterator var8 = listOfInstanceInfo.iterator();
while(var8.hasNext()) {
InstanceInfo ii = (InstanceInfo)var8.next();
if (ii.getStatus().equals(InstanceStatus.UP)) {
if (this.shouldUseOverridePort) {
if (logger.isDebugEnabled()) {
logger.debug("Overriding port on client name: " + this.clientName + " to " + this.overridePort);
}
InstanceInfo copy = new InstanceInfo(ii);
if (this.isSecure) {
ii = (new Builder(copy)).setSecurePort(this.overridePort).build();
} else {
ii = (new Builder(copy)).setPort(this.overridePort).build();
}
}
DiscoveryEnabledServer des = this.createServer(ii, this.isSecure, this.shouldUseIpAddr);
serverList.add(des);
}
}
if (serverList.size() > 0 && this.prioritizeVipAddressBasedServers) {
break;
}
}
}
return serverList;
} else {
logger.warn("EurekaClient has not been initialized yet, returning an empty list");
return new ArrayList();
}
}
