EurekaClient源码分析
EurekaClient 源码分析
eureka 源码地址: https://github.com/Netflix/eureka
eureka 项目整合地址: https://github.com/TongBlackLittle/springCloud
以下内容 参照 SpringCloud 微服务实战,进行学习记录的,我在这里根据个人理解进行了记录,欢迎大家一起交流
EurekaClient 的实现关系
- 通过注解 @EnableDiscoveryClient 进入到类内部
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@Import({EnableDiscoveryClientImportSelector.class})
public @interface EnableDiscoveryClient {
boolean autoRegister() default true;
}
// 同级目录可以看到 discoveryClient
package org.springframework.cloud.client.discovery;
import java.util.List;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.core.Ordered;
public interface DiscoveryClient extends Ordered {
int DEFAULT_ORDER = 0;
String description();
List getInstances(String serviceId);
List getServices();
default int getOrder() {
return 0;
}
}
discoverClient 该接口为 springCloud 提供的接口 定义发现服务的抽象方法.通过搜索可以发现,EurekaDiscouveryClient 是对该接口的实现
import com.netflix.discovery.EurekaClient;
public class EurekaDiscoveryClient implements DiscoveryClient {
public static final String DESCRIPTION = "Spring Cloud Eureka Discovery Client";
private final EurekaClient eurekaClient;
private final EurekaClientConfig clientConfig;
}
实现类依赖了 netflix.discovery.EurekaClient 而 EurekaClient 继承了 LookupService 类,而真正的实现类是 erureka 包下的 DiscveryClient
EurekaClient 负责的任务
- 向 Eureka Server 注册服务示例
- 向 Eureka Servier 服务租约
- 当服务关闭期间, 向Eureka Server 取消租约
- 查询Eureka Server 中的服务示例列表
Eureka Client 还需要配置一个Eureka Server 的 URL 列表
EurekaClient 配置的服务列表如何配置的
- 配置的名称 : eureka.client.serviceUrl.defaultZone
通过 serviceUrl 我们可以在 EurekaDiiscoveryClient 中发现 getServiceUrlsFromConfig 方法 但是 该方法是被 @Deprecated 声明的 说明该方法已经被弃用了(如果对源码好奇,可以在 github 上边下载 eureka 的源码进行查看了解具体细节)
看源码 发现 该方法被连接 @link 到 EndpointUriles ,所以我们到 EndpointUrils中去查看
public static List getServiceUrlsFromConfig(EurekaClientConfig clientConfig, String instanceZone, boolean preferSameZone) {
List orderedUrls = new ArrayList();
String region = getRegion(clientConfig);
String[] availZones = clientConfig.getAvailabilityZones(clientConfig.getRegion());
if (availZones == null || availZones.length == 0) {
availZones = new String[1];
availZones[0] = DEFAULT_ZONE;
}
logger.debug("The availability zone for the given region {} are {}", region, availZones);
int myZoneOffset = getZoneOffset(instanceZone, preferSameZone, availZones);
List serviceUrls = clientConfig.getEurekaServerServiceUrls(availZones[myZoneOffset]);
if (serviceUrls != null) {
orderedUrls.addAll(serviceUrls);
}
int currentOffset = myZoneOffset == (availZones.length - 1) ? 0 : (myZoneOffset + 1);
while (currentOffset != myZoneOffset) {
serviceUrls = clientConfig.getEurekaServerServiceUrls(availZones[currentOffset]);
if (serviceUrls != null) {
orderedUrls.addAll(serviceUrls);
}
if (currentOffset == (availZones.length - 1)) {
currentOffset = 0;
} else {
currentOffset++;
}
}
if (orderedUrls.size() < 1) {
throw new IllegalArgumentException("DiscoveryClient: invalid serviceUrl specified!");
}
return orderedUrls;
}
public static String getRegion(EurekaClientConfig clientConfig) {
String region = clientConfig.getRegion();
if (region == null) {
region = DEFAULT_REGION;
}
region = region.trim().toLowerCase();
return region;
}
public String[] getAvailabilityZones(String region) {
String value = (String)this.availabilityZones.get(region);
if (value == null) {
value = "defaultZone";
}
return value.split(",");
}
可以看到 该方法一次加载了 getRegion() 和 getAvailabilityZones() 来获取配置,也就是 说明 一个微服务只对应了一个 Region 和 多个 Zones 他们之间是 一对多的关系 (这个配置是在区分物理机位置时来进行配置,当发生服务宕机时可以根据 region 来快速进行定位)
eurekaClient 默认加载 defaultZone 获取 AvaliableilityZones() 时 可以看到 他是 ‘,’ 进行区分的,defaultZone 可以加载多个
加载了 Region 和 Zone 之后 开始真正的加载 EurekaServer 的地址
int myZoneOffset = getZoneOffset(instanceZone, preferSameZone, availZones);
List serviceUrls = clientConfig.getEurekaServerServiceUrls(availZones[myZoneOffset]);
if (serviceUrls != null) {
orderedUrls.addAll(serviceUrls);
}
通过上边的 getEurekaServerServiceUrls () 可以看一下具体的实现
public List getEurekaServerServiceUrls(String myZone) {
String serviceUrls = (String)this.serviceUrl.get(myZone);
if (serviceUrls == null || serviceUrls.isEmpty()) {
serviceUrls = (String)this.serviceUrl.get("defaultZone");
}
if (!StringUtils.isEmpty(serviceUrls)) {
String[] serviceUrlsSplit = StringUtils.commaDelimitedListToStringArray(serviceUrls);
List eurekaServiceUrls = new ArrayList(serviceUrlsSplit.length);
String[] var5 = serviceUrlsSplit;
int var6 = serviceUrlsSplit.length;
for(int var7 = 0; var7 < var6; ++var7) {
String eurekaServiceUrl = var5[var7];
if (!this.endsWithSlash(eurekaServiceUrl)) {
eurekaServiceUrl = eurekaServiceUrl + "/";
}
eurekaServiceUrls.add(eurekaServiceUrl.trim());
}
return eurekaServiceUrls;
} else {
return new ArrayList();
}
}
通过 Ribbon 来获取服务调用时 先访问 一个 Zone 中的服务端实例, 当这个实例为 null 时 在去访问其他的Zone 中的实例 Eureka 在进行高可用时 进行的多节点配置,就是这个时候用的
服务注册
- 通过 DiscoverClient 的构造方法 可以找到该方法 initScheduledTasks();
private void initScheduledTasks() {
int renewalIntervalInSecs;
int expBackOffBound;
if (this.clientConfig.shouldFetchRegistry()) {
renewalIntervalInSecs = this.clientConfig.getRegistryFetchIntervalSeconds();
expBackOffBound = this.clientConfig.getCacheRefreshExecutorExponentialBackOffBound();
this.cacheRefreshTask = new TimedSupervisorTask("cacheRefresh", this.scheduler, this.cacheRefreshExecutor, renewalIntervalInSecs, TimeUnit.SECONDS, expBackOffBound, new DiscoveryClient.CacheRefreshThread());
this.scheduler.schedule(this.cacheRefreshTask, (long)renewalIntervalInSecs, TimeUnit.SECONDS);
}
if (this.clientConfig.shouldRegisterWithEureka()) {
renewalIntervalInSecs = this.instanceInfo.getLeaseInfo().getRenewalIntervalInSecs();
expBackOffBound = this.clientConfig.getHeartbeatExecutorExponentialBackOffBound();
logger.info("Starting heartbeat executor: renew interval is: {}", renewalIntervalInSecs);
this.heartbeatTask = new TimedSupervisorTask("heartbeat", this.scheduler, this.heartbeatExecutor, renewalIntervalInSecs, TimeUnit.SECONDS, expBackOffBound, new DiscoveryClient.HeartbeatThread());
this.scheduler.schedule(this.heartbeatTask, (long)renewalIntervalInSecs, TimeUnit.SECONDS);
this.instanceInfoReplicator = new InstanceInfoReplicator(this, this.instanceInfo, this.clientConfig.getInstanceInfoReplicationIntervalSeconds(), 2);
this.statusChangeListener = new StatusChangeListener() {
public String getId() {
return "statusChangeListener";
}
public void notify(StatusChangeEvent statusChangeEvent) {
if (InstanceStatus.DOWN != statusChangeEvent.getStatus() && InstanceStatus.DOWN != statusChangeEvent.getPreviousStatus()) {
DiscoveryClient.logger.info("Saw local status change event {}", statusChangeEvent);
} else {
DiscoveryClient.logger.warn("Saw local status change event {}", statusChangeEvent);
}
DiscoveryClient.this.instanceInfoReplicator.onDemandUpdate();
}
};
if (this.clientConfig.shouldOnDemandUpdateStatusChange()) {
this.applicationInfoManager.registerStatusChangeListener(this.statusChangeListener);
}
this.instanceInfoReplicator.start(this.clientConfig.getInitialInstanceInfoReplicationIntervalSeconds());
} else {
logger.info("Not registering with Eureka server per configuration");
}
}
该方法中提供了
服务注册服务续约服务获取的具体内容
this.heartbeatTask = new TimedSupervisorTask(“heartbeat”, this.scheduler, this.heartbeatExecutor, renewalIntervalInSecs, TimeUnit.SECONDS, expBackOffBound, new DiscoveryClient.HeartbeatThread());
this.instanceInfoReplicator = new InstanceInfoReplicator(this, this.instanceInfo, this.clientConfig.getInstanceInfoReplicationIntervalSeconds(), 2);
heartbeatTask 开启了心跳进行服务续约 instanceInfoReplicator 进行服务注册
new InstanceInfoReplicator() 方法我们可以看到 该类实现了 Runable 接口 通过该类启动了一个定时任务,在 该 run 方法中 .register() 方法来真正的执行服务注册的
public void run() {
boolean var6 = false;
ScheduledFuture next;
label53: {
try {
var6 = true;
this.discoveryClient.refreshInstanceInfo();
Long dirtyTimestamp = this.instanceInfo.isDirtyWithTime();
if (dirtyTimestamp != null) {
this.discoveryClient.register();
this.instanceInfo.unsetIsDirty(dirtyTimestamp);
var6 = false;
} else {
var6 = false;
}
break label53;
} catch (Throwable var7) {
logger.warn("There was a problem with the instance info replicator", var7);
var6 = false;
} finally {
if (var6) {
ScheduledFuture next = this.scheduler.schedule(this, (long)this.replicationIntervalSeconds, TimeUnit.SECONDS);
this.scheduledPeriodicRef.set(next);
}
}
next = this.scheduler.schedule(this, (long)this.replicationIntervalSeconds, TimeUnit.SECONDS);
this.scheduledPeriodicRef.set(next);
return;
}
next = this.scheduler.schedule(this, (long)this.replicationIntervalSeconds, TimeUnit.SECONDS);
this.scheduledPeriodicRef.set(next);
}
boolean renew() {
try {
EurekaHttpResponse httpResponse = this.eurekaTransport.registrationClient.sendHeartBeat(this.instanceInfo.getAppName(), this.instanceInfo.getId(), this.instanceInfo, (InstanceStatus)null);
logger.debug("DiscoveryClient_{} - Heartbeat status: {}", this.appPathIdentifier, httpResponse.getStatusCode());
if (httpResponse.getStatusCode() == Status.NOT_FOUND.getStatusCode()) {
this.REREGISTER_COUNTER.increment();
logger.info("DiscoveryClient_{} - Re-registering apps/{}", this.appPathIdentifier, this.instanceInfo.getAppName());
long timestamp = this.instanceInfo.setIsDirtyWithTime();
boolean success = this.register();
if (success) {
this.instanceInfo.unsetIsDirty(timestamp);
}
return success;
} else {
return httpResponse.getStatusCode() == Status.OK.getStatusCode();
}
} catch (Throwable var5) {
logger.error("DiscoveryClient_{} - was unable to send heartbeat!", this.appPathIdentifier, var5);
return false;
}
}
boolean renew() {
try {
EurekaHttpResponse httpResponse = this.eurekaTransport.registrationClient.sendHeartBeat(this.instanceInfo.getAppName(), this.instanceInfo.getId(), this.instanceInfo, (InstanceStatus)null);
logger.debug("DiscoveryClient_{} - Heartbeat status: {}", this.appPathIdentifier, httpResponse.getStatusCode());
if (httpResponse.getStatusCode() == Status.NOT_FOUND.getStatusCode()) {
this.REREGISTER_COUNTER.increment();
logger.info("DiscoveryClient_{} - Re-registering apps/{}", this.appPathIdentifier, this.instanceInfo.getAppName());
long timestamp = this.instanceInfo.setIsDirtyWithTime();
boolean success = this.register();
if (success) {
this.instanceInfo.unsetIsDirty(timestamp);
}
return success;
} else {
return httpResponse.getStatusCode() == Status.OK.getStatusCode();
}
} catch (Throwable var5) {
logger.error("DiscoveryClient_{} - was unable to send heartbeat!", this.appPathIdentifier, var5);
return false;
}
}
进入到 register 方法中 我们可以看到 该方法 通过发送 http 请求来进行服务注册 其中 注册信息为 InstanceInfo (保存服务实例的相关信息)
同理 进入到 renew 方法中 this.instanceInfo.getAppName(), this.instanceInfo.getId(), this.instanceInfo, (InstanceStatus)null 将这些数据定时发送给 server 端进行 服务续约
服务获取
在上边的源码中 我们可以看到 this.cacheRefreshTask = new TimedSupervisorTask(“cacheRefresh”, this.scheduler, this.cacheRefreshExecutor, renewalIntervalInSecs, TimeUnit.SECONDS, expBackOffBound, new DiscoveryClient.CacheRefreshThread());
服务获取和服务续约 服务注册是分开放在不同的 if 判断中的 (可以理解 注册之后 需要对服务进行续约)
服务获取和服务续约查看逻辑类似,当时比较复杂
TO-DO