本文作者：陈刚，叩丁狼高级讲师。原创文章，转载请注明出处。
我们在分析eureka-client的时候发现他是通过Http Rest 的方式做请求的，那么eureka-server一定是基于Rest风格 类似SpringMvc一样的模式接受处理请求。在 EurekaServerAutoConfiguration 自动配置类中有一个 jerseyFilterRegistration方法，这个方法表明eureka-server使用了Jersey实现Rest
/**
* 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;
}
这里在注册一个 Jersey 的 filter ，配置好相应的Filter 和 url映射等
处理服务注册
Eureka Server对于Eureka client的REST请求的定义都位于com.netflix.eureka.resources包下，我们先来看
com.netflix.eureka.resources.ApplicationResource下面的addInstance方法，看名字就知道是添加服务实例
@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
InstanceInfo 参数就是客户端提交的服务元配置信息，
做了一大堆判断后调用了com.netflix.eureka.registry.PeerAwareInstanceRegistryImpl.register： 进行注册，我们跟踪进去
@Override
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();
}
super.register(info, leaseDuration, isReplication);
replicateToPeers(Action.Register, info.getAppName(), info.getId(), info, null, isReplication);
}
继续跟踪 super.register ：调用了父类的注册方法。
/**
* Registers a new instance with a given duration.
*
* @see com.netflix.eureka.lease.LeaseManager#register(java.lang.Object, int, boolean)
*/
public void register(InstanceInfo registrant, int leaseDuration, boolean isReplication) {
try {
read.lock();
Map> gMap = registry.get(registrant.getAppName());
REGISTER.increment(isReplication);
if (gMap == null) {
final ConcurrentHashMap> gNewMap = new ConcurrentHashMap>();
gMap = registry.putIfAbsent(registrant.getAppName(), gNewMap);
if (gMap == null) {
gMap = gNewMap;
}
}
这里我们看到 ConcurrentHashMap
它是一个两层Map结构，第一层的key存储服务名：InstanceInfo中的appName属性，第二层的key存储实例名：InstanceInfo中的instanceId属性。
服务的续约（心跳）
服务续约在 com.netflix.eureka.resources.InstanceResource#renewLease方法中
@PUT
public Response renewLease(
@HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication,
@QueryParam("overriddenstatus") String overriddenStatus,
@QueryParam("status") String status,
@QueryParam("lastDirtyTimestamp") String lastDirtyTimestamp) {
boolean isFromReplicaNode = "true".equals(isReplication);
boolean isSuccess = registry.renew(app.getName(), id, isFromReplicaNode);
获取到客户端服务名字 调用registry.renew实现续约 ，我们跟踪进去最终会调用 com.netflix.eureka.registry.AbstractInstanceRegistry#renew方法
public boolean renew(String appName, String id, boolean isReplication) {
RENEW.increment(isReplication);
Map> gMap = registry.get(appName);
Lease leaseToRenew = null;
if (gMap != null) {
leaseToRenew = gMap.get(id);
}
if (leaseToRenew == null) {
RENEW_NOT_FOUND.increment(isReplication);
logger.warn("DS: Registry: lease doesn't exist, registering resource: {} - {}", appName, id);
return false;
} else {
InstanceInfo instanceInfo = leaseToRenew.getHolder();
if (instanceInfo != null) {
// touchASGCache(instanceInfo.getASGName());
InstanceStatus overriddenInstanceStatus = this.getOverriddenInstanceStatus(
instanceInfo, leaseToRenew, isReplication);
if (overriddenInstanceStatus == InstanceStatus.UNKNOWN) {
logger.info("Instance status UNKNOWN possibly due to deleted override for instance {}"
+ "; re-register required", instanceInfo.getId());
RENEW_NOT_FOUND.increment(isReplication);
return false;
}
if (!instanceInfo.getStatus().equals(overriddenInstanceStatus)) {
logger.info(
"The instance status {} is different from overridden instance status {} for instance {}. "
+ "Hence setting the status to overridden status", instanceInfo.getStatus().name(),
instanceInfo.getOverriddenStatus().name(),
instanceInfo.getId());
instanceInfo.setStatusWithoutDirty(overriddenInstanceStatus);
}
}
renewsLastMin.increment();
leaseToRenew.renew();
return true;
}
Map
leaseToRenew = gMap.get(id); 在获取注册的服务实例
instanceInfo.setStatusWithoutDirty(overriddenInstanceStatus); 在修改服务实例的状态
leaseToRenew.renew(); 在增加租约时间
public void renew() {
lastUpdateTimestamp = System.currentTimeMillis() + duration;
}
取消租约:客户端线下
追踪 InstanceResource#cancelLease() 方法,最终会调用 com.netflix.eureka.registry.AbstractInstanceRegistry#internalCancel
protected boolean internalCancel(String appName, String id, boolean isReplication) {
boolean var7;
try {
this.read.lock();
EurekaMonitors.CANCEL.increment(isReplication);
Map> gMap = (Map)this.registry.get(appName);
Lease leaseToCancel = null;
if (gMap != null) {
leaseToCancel = (Lease)gMap.remove(id);
}
......
gMap.remove(id); 就是获取当前要下线的服务id，然后从注册的map中移除掉
服务端的请求接收差不多，对于其他的服务端处理这里就不在多说，可执行断点跟踪。
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