前言

本片文章的目的是分析Eureka Server的注册流程，您可以结合《Eureka Client服务注册》更容易理解

Eureka Server服务注册流程

在《Eureka Server初始化流程》文章中我们知道，在EurekaServerAutoConfiguration中注册了JerseyFilter用来处理所有的/eureka开头的请求,当Eureka Client客户端发起注册请求，请求被该Filter接待

/*** Register the Jersey filter* 注册Jersey filter*/@BeanpublicFilterRegistrationBeanjerseyFilterRegistration(
javax.ws.rs.core.ApplicationeurekaJerseyApp) {
FilterRegistrationBeanbean=newFilterRegistrationBean();
//ServletContainer 是核心处理类bean.setFilter(newServletContainer(eurekaJerseyApp));
bean.setOrder(Ordered.LOWEST_PRECEDENCE);
//处理的请求/eureka/**bean.setUrlPatterns(
Collections.singletonList(EurekaConstants.DEFAULT_PREFIX+"/*"));
returnbean;
}

具体的实现是在ServletContainer中完成

//处理请求privatevoiddoFilter(HttpServletRequestrequest, HttpServletResponseresponse, FilterChainchain, StringrequestURI, StringservletPath, StringqueryString) throwsIOException, ServletException {
Patternp=this.getStaticContentPattern();
//处理 ContextPath 上下文路径if (p!=null&&p.matcher(servletPath).matches()) {
chain.doFilter(request, response);
    } else {
if (this.filterContextPath!=null) {
if (!servletPath.startsWith(this.filterContextPath)) {
thrownewContainerException("The servlet path, \""+servletPath+"\", does not start with the filter context path, \""+this.filterContextPath+"\"");
            }
if (servletPath.length() ==this.filterContextPath.length()) {
if (this.webComponent.getResourceConfig().getFeature("com.sun.jersey.config.feature.Redirect")) {
URIl=UriBuilder.fromUri(request.getRequestURL().toString()).path("/").replaceQuery(queryString).build(newObject[0]);
response.setStatus(307);
response.setHeader("Location", l.toASCIIString());
return;
                }
requestURI=requestURI+"/";
            }
        }
UriBuilderabsoluteUriBuilder=UriBuilder.fromUri(request.getRequestURL().toString());
URIbaseUri=this.filterContextPath==null?absoluteUriBuilder.replacePath(request.getContextPath()).path("/").build(newObject[0]) : absoluteUriBuilder.replacePath(request.getContextPath()).path(this.filterContextPath).path("/").build(newObject[0]);
URIrequestUri=absoluteUriBuilder.replacePath(requestURI).replaceQuery(queryString).build(newObject[0]);
//这里调用service方法intstatus=this.service(baseUri, requestUri, request, response);
if (this.forwardOn404&&status==404&&!response.isCommitted()) {
response.setStatus(200);
chain.doFilter(request, response);
        }
    }
}
// 处理请求，调用WebComponent的service方法publicintservice(URIbaseUri, URIrequestUri, HttpServletRequestrequest, HttpServletResponseresponse) throwsServletException, IOException {
returnthis.webComponent.service(baseUri, requestUri, request, response);
}

最终会调用ApplicationResource实现服务注册， Eureka Server对于Eureka client注册服务实例，获取服务实例的的REST请求的都交给ApplicationResource处理，其中用来服务注册的方法是addInstance,我们来看一下他的源码

/**服务实例注册,InstanceInfo是服务注册信息，isReplicationd为true代表是从其他Eureka Server节点复制实例，如果是isReplication为false，代表是Eureka Client 注册的* Registers information about a particular instance for an* {@link com.netflix.discovery.shared.Application}.** @param info*            {@link InstanceInfo} information of the instance.* @param isReplication*            a header parameter containing information whether this is*            replicated from other nodes.*/@POST@Consumes({"application/json", "application/xml"})
publicResponseaddInstance(InstanceInfoinfo,
@HeaderParam(PeerEurekaNode.HEADER_REPLICATION) StringisReplication) {
logger.debug("Registering instance {} (replication={})", info.getId(), isReplication);
//验证instanceinfo包含所有必需的必填字段// validate that the instanceinfo contains all the necessary required fieldsif (isBlank(info.getId())) {
returnResponse.status(400).entity("Missing instanceId").build();
    } elseif (isBlank(info.getHostName())) {
returnResponse.status(400).entity("Missing hostname").build();
    } elseif (isBlank(info.getIPAddr())) {
returnResponse.status(400).entity("Missing ip address").build();
    } elseif (isBlank(info.getAppName())) {
returnResponse.status(400).entity("Missing appName").build();
    } elseif (!appName.equals(info.getAppName())) {
returnResponse.status(400).entity("Mismatched appName, expecting "+appName+" but was "+info.getAppName()).build();
    } elseif (info.getDataCenterInfo() ==null) {
returnResponse.status(400).entity("Missing dataCenterInfo").build();
    } elseif (info.getDataCenterInfo().getName() ==null) {
returnResponse.status(400).entity("Missing dataCenterInfo Name").build();
    }
//处理客户端可能在数据缺失的情况下向错误的DataCenterInfo注册的情况// handle cases where clients may be registering with bad DataCenterInfo with missing dataDataCenterInfodataCenterInfo=info.getDataCenterInfo();
if (dataCenterInfoinstanceofUniqueIdentifier) {
StringdataCenterInfoId= ((UniqueIdentifier) dataCenterInfo).getId();
if (isBlank(dataCenterInfoId)) {
booleanexperimental="true".equalsIgnoreCase(serverConfig.getExperimental("registration.validation.dataCenterInfoId"));
if (experimental) {
Stringentity="DataCenterInfo of type "+dataCenterInfo.getClass() +" must contain a valid id";
returnResponse.status(400).entity(entity).build();
            } elseif (dataCenterInfoinstanceofAmazonInfo) {
AmazonInfoamazonInfo= (AmazonInfo) dataCenterInfo;
StringeffectiveId=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());
            }
        }
    }
//【重要】：这里在调用PeerAwareInstanceRegistry的register注册服务，使用的是实现类：InstanceRegistryregistry.register(info, "true".equals(isReplication));
returnResponse.status(204).build();  // 204 to be backwards compatible}

ApplicationResource.addInstance看方法名就能推测出他是用来注册实例的方法，其中参数InstanceInfo 是客户端提交的注册信息，请求头中isReplicationd为true代表是从其他Eureka Server节点复制实例，如果是isReplication为false，代表是Eureka Client 注册的

在做了一些列参数判断之后，这里在调用PeerAwareInstanceRegistry的register注册服务，使用的是实现类：InstanceRegistry，这个类在之前有介绍过，就是Eureak Server用来实现服务注册，服务发现，服务续约，取消注册等的具体实现，他的继承关系如下：

跟踪下去，InstanceRegistry .register方法源码如下

publicclassInstanceRegistryextendsPeerAwareInstanceRegistryImplimplementsApplicationContextAware {
publicvoidregister(finalInstanceInfoinfo, finalbooleanisReplication) {
//调用handleRegistration方法，抛出事件：EurekaInstanceRegisteredEventthis.handleRegistration(info, this.resolveInstanceLeaseDuration(info), isReplication);
//调用父类PeerAwareInstanceRegistryImpl的register方法super.register(info, isReplication);
    }
//服务注册，抛出EurekaInstanceRegisteredEvent事件privatevoidhandleRegistration(InstanceInfoinfo, intleaseDuration, booleanisReplication) {
this.log("register "+info.getAppName() +", vip "+info.getVIPAddress() +", leaseDuration "+leaseDuration+", isReplication "+isReplication);
this.publishEvent(newEurekaInstanceRegisteredEvent(this, info, leaseDuration, isReplication));
    }
  ...省略...  
  }

这里在调用handleRegistration方法，抛出事件：EurekaInstanceRegisteredEvent后继续调用了super.register方法，即：PeerAwareInstanceRegistryImpl.register，继续跟踪下去：

@SingletonpublicclassPeerAwareInstanceRegistryImplextendsAbstractInstanceRegistryimplementsPeerAwareInstanceRegistry {
/**注册服务信息 InstanceInfo，并将此信息InstanceInfo复制到所有对等的eureka server节点。如果这是来自其他副本节点的复制事件，则不会复制它。* Registers the information about the {@link InstanceInfo} and replicates* this information to all peer eureka nodes. If this is replication event* from other replica nodes then it is not replicated.** @param info*            the {@link InstanceInfo} to be registered and replicated.* @param isReplication*            true if this is a replication event from other replica nodes,*            false otherwise.*/@Overridepublicvoidregister(finalInstanceInfoinfo, finalbooleanisReplication) {
//租期失效时间 90 sintleaseDuration=Lease.DEFAULT_DURATION_IN_SECS;
if (info.getLeaseInfo() !=null&&info.getLeaseInfo().getDurationInSecs() >0) {
//如果服务的租期失效时间大于默认的90s，则重新赋值租期时间leaseDuration=info.getLeaseInfo().getDurationInSecs();
        }
//服务注册super.register(info, leaseDuration, isReplication);
//把注册的服务信息复制到其他的Eureka Server 节点，注意这里是Action.RegisterreplicateToPeers(Action.Register, info.getAppName(), info.getId(), info, null, isReplication);
    }
}

该方法做了3个事情，

1是更新租期失效时间，
2是调用super.register服务注册(AbstractInstanceRegistry.register)
3是调用replicateToPeers把服务实例拷贝到其他的Eureak Server节点

我们先看下super.register方法即：AbstractInstanceRegistry.register方法的源码

/*** Registers a new instance with a given duration.** @see com.netflix.eureka.lease.LeaseManager#register(java.lang.Object, int, boolean)*/publicvoidregister(InstanceInforegistrant, intleaseDuration, booleanisReplication) {
try {
//获取锁：ReentrantReadWriteLock.lock()read.lock();
//根据注册的服务的名字取本地服务注册表中获取服务注册信息，如果该服务已经被注册了，那么registry中将会存在它Map<String, Lease<InstanceInfo>>gMap=registry.get(registrant.getAppName());
REGISTER.increment(isReplication);
if (gMap==null) {
//如果该服务实例没被注册，就把服务实例注册到本地的registry中，本质是一个MapfinalConcurrentHashMap<String, Lease<InstanceInfo>>gNewMap=newConcurrentHashMap<String, Lease<InstanceInfo>>();
//没有的话就添加到registry中gMap=registry.putIfAbsent(registrant.getAppName(), gNewMap);
if (gMap==null) {
gMap=gNewMap;
            }
        }
//根据服务实例id获取服务的租约对象Lease<InstanceInfo>existingLease=gMap.get(registrant.getId());
// Retain the last dirty timestamp without overwriting it, if there is already a lease//如果已经有租约，则保留最后的脏时间戳而不覆盖它if (existingLease!=null&& (existingLease.getHolder() !=null)) {
//registry中已经存在的当前服务的最后修改时间的时间戳LongexistingLastDirtyTimestamp=existingLease.getHolder().getLastDirtyTimestamp();
//提交注册的当前服务的最后修改时间LongregistrationLastDirtyTimestamp=registrant.getLastDirtyTimestamp();
logger.debug("Existing lease found (existing={}, provided={}", existingLastDirtyTimestamp, registrationLastDirtyTimestamp);
//因为如果时间戳相等，我们仍然采用远程传输的InstanceInfo而不是服务器本地副本// 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.//如果已存在的该服务的修改时间 大于 当前提交注册的该服务的最后修改时间，//则采用registy中已存在的服务为准,因为要选择修改时间靠后的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");
//使用现有的instanceInfo代替新的instanceInfo作为注册者registrant=existingLease.getHolder();
            }
        } else {
//执行到这里，说明该服务是新注册// The lease does not exist and hence it is a new registrationsynchronized (lock) {
//这里在计算服务的续约频率值if (this.expectedNumberOfRenewsPerMin>0) {
// Since the client wants to cancel it, reduce the threshold// (1// for 30 seconds, 2 for a minute)//(expectedNumberOfRenewsPerMin)期待的每分钟续订次数,默认是30s/个，给他增加到2，每分钟2个请求this.expectedNumberOfRenewsPerMin=this.expectedNumberOfRenewsPerMin+2;
//修改numberOfRenewsPerMinThreshold每分钟续约阀值 = 2 *（85%），//RenewalPercentThreshold是获取续订阈值百分比         this.numberOfRenewsPerMinThreshold=                        (int) (this.expectedNumberOfRenewsPerMin*serverConfig.getRenewalPercentThreshold());
                }
            }
logger.debug("No previous lease information found; it is new registration");
        }
//创建租约对象，把注册实例和租期放进去Lease<InstanceInfo>lease=newLease<InstanceInfo>(registrant, leaseDuration);
if (existingLease!=null) {
//设置服务上线时间lease.setServiceUpTimestamp(existingLease.getServiceUpTimestamp());
        }
//以注册的实例的ID为key把服务实例存封装到 MapgMap.put(registrant.getId(), lease);
//添加到注册队列synchronized (recentRegisteredQueue) {
recentRegisteredQueue.add(newPair<Long, String>(
System.currentTimeMillis(),
registrant.getAppName() +"("+registrant.getId() +")"));
        }
// This is where the initial state transfer of overridden status happensif (!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());
//添加服务的OverriddenStatusoverriddenInstanceStatusMap.put(registrant.getId(), registrant.getOverriddenStatus());
            }
        }
InstanceStatusoverriddenStatusFromMap=overriddenInstanceStatusMap.get(registrant.getId());
if (overriddenStatusFromMap!=null) {
logger.info("Storing overridden status {} from map", overriddenStatusFromMap);
registrant.setOverriddenStatus(overriddenStatusFromMap);
        }
//根据覆盖的状态规则设置状态// Set the status based on the overridden status rulesInstanceStatusoverriddenInstanceStatus=getOverriddenInstanceStatus(registrant, existingLease, isReplication);
registrant.setStatusWithoutDirty(overriddenInstanceStatus);
// If the lease is registered with UP status, set lease service up timestamp//如果租约已注册为UP状态，请设置租约服务启动时间戳记if (InstanceStatus.UP.equals(registrant.getStatus())) {
//更新服务上线时间戳lease.serviceUp();
        }
//服务动作：ADDED添加，MODIFIED修改，DELETED删除registrant.setActionType(ActionType.ADDED);
//添加到最近更改的队列recentlyChangedQueue.add(newRecentlyChangedItem(lease));
//最后更新时间registrant.setLastUpdatedTimestamp();
//使当前应用的ResponseCache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();
    }
}

总结一下，这个方法做了什么呢

判断当前服务是否已经被注册，如果是，则以最后更新时间为准，选择更新时间靠后的服务实例进行注册
维护实例的租约信息Lease，并放到Eureka Server本地维护维护的registry注册表中，本质是一个Map（ConcurrentHashMap<String, Map<String, Lease>>）
如果是服务是新注册的，把注册的实例封装成Leaset存储到registry注册表中，并更新每分钟续约阀值numberOfRenewsPerMinThreshold
维护了两个队列，recentRegisteredQueue最近注册队列，recentlyChangedQueue最近更改队列，这个队列可以用来获取最近操作的信息。
维护当前实例的OverriddenStatus
更新服务实例的最后更新时间戳
使ResponseCache缓存失效

该方法结束，我们回到PeerAwareInstanceRegistryImpl.register方法中，继续跟踪replicateToPeers 方法

@SingletonpublicclassPeerAwareInstanceRegistryImplextendsAbstractInstanceRegistryimplementsPeerAwareInstanceRegistry {
/*** Replicates all eureka actions to peer eureka nodes except for replication* traffic to this node.* 将所有eureka操作复制到对等eureka节点*/privatevoidreplicateToPeers(Actionaction, StringappName, Stringid,
InstanceInfoinfo/* optional */,
InstanceStatusnewStatus/* optional */, booleanisReplication) {
//开始计时Stopwatchtracer=action.getTimer().start();
try {
//是否是其他节点复制过来的if (isReplication) {
//最后一分钟的复制次数+1numberOfReplicationsLastMin.increment();
            }
// If it is a replication already, do not replicate again as this will create a poison replication//如果已经是复制，则不要再次复制if (peerEurekaNodes==Collections.EMPTY_LIST||isReplication) {
return;
            }
//遍历集群所有节点for (finalPeerEurekaNodenode : peerEurekaNodes.getPeerEurekaNodes()) {
// If the url represents this host, do not replicate to yourself.//如果该URL代表此主机，请不要复制到您自己，当前节点不复制if (peerEurekaNodes.isThisMyUrl(node.getServiceUrl())) {
continue;
                }
//复制实例到其他某个EurekareplicateInstanceActionsToPeers(action, appName, id, info, newStatus, node);
            }
        } finally {
tracer.stop();
        }
    }

继续跟踪replicateInstanceActionsToPeers的源码

/*** Replicates all instance changes to peer eureka nodes except for* replication traffic to this node.**/privatevoidreplicateInstanceActionsToPeers(Actionaction, StringappName,
Stringid, InstanceInfoinfo, InstanceStatusnewStatus,
PeerEurekaNodenode) {
try {
InstanceInfoinfoFromRegistry=null;
CurrentRequestVersion.set(Version.V2);
//判断请求的是什么操作switch (action) {
//取消注册，调用 PeerEurekaNode.cancelcaseCancel:
node.cancel(appName, id);
break;
//心跳请求，调用PeerEurekaNode.heartbeatcaseHeartbeat:
InstanceStatusoverriddenStatus=overriddenInstanceStatusMap.get(id);
infoFromRegistry=getInstanceByAppAndId(appName, id, false);
node.heartbeat(appName, id, infoFromRegistry, overriddenStatus, false);
break;
//服务注册调用PeerEurekaNode.registercaseRegister:
node.register(info);
break;
//状态修改调用PeerEurekaNode.statusUpdatecaseStatusUpdate:
infoFromRegistry=getInstanceByAppAndId(appName, id, false);
node.statusUpdate(appName, id, newStatus, infoFromRegistry);
break;
//状态删除调用PeerEurekaNode.deleteStatusOverridecaseDeleteStatusOverride:
infoFromRegistry=getInstanceByAppAndId(appName, id, false);
node.deleteStatusOverride(appName, id, infoFromRegistry);
break;
        }
    } catch (Throwablet) {
logger.error("Cannot replicate information to {} for action {}", node.getServiceUrl(), action.name(), t);
    }
}

这里在根据请求的动作类型选择PeerEurekaNode的不同方法，我们这里是服务注册.register，调用的是 PeerEurekaNode.register ，源码如下：

/*** Sends the registration information of {@link InstanceInfo} receiving by* this node to the peer node represented by this class.** @param info*            the instance information {@link InstanceInfo} of any instance*            that is send to this instance.* @throws Exception*/publicvoidregister(finalInstanceInfoinfo) throwsException {
//到期时间当，前时间加上30s过期longexpiryTime=System.currentTimeMillis() +getLeaseRenewalOf(info);
//封装InstanceReplicationTask 实例赋值任务到调度器中batchingDispatcher.process(
taskId("register", info),
newInstanceReplicationTask(targetHost, Action.Register, info, null, true) {                
publicEurekaHttpResponse<Void>execute() {
//复制器客户端 HttpReplicationClient(JerseyReplicationClient)，执行注册//调用AbstractJerseyEurekaHttpClient#registerreturnreplicationClient.register(info);
            }
        },
expiryTime    );
}

把InstanceInfo注册实例封装成InstanceReplicationTask实例复制任务，交给batchingDispatcher批量任务调度器去执行，replicationClient是HttpReplicationClient它的默认实现是JerseyEurekaHttpClient，底层会调用AbstractJerseyEurekaHttpClient#register的方法完成实例的注册，这里其实就和当时我们分析Eureka Client 服务注册的最后注册请求一样了

publicabstractclassAbstractJerseyEurekaHttpClientimplementsEurekaHttpClient {
publicEurekaHttpResponse<Void>register(InstanceInfoinfo) {
//请求地址StringurlPath="apps/"+info.getAppName();
ClientResponseresponse=null;
EurekaHttpResponsevar5;
try {
BuilderresourceBuilder=this.jerseyClient.resource(this.serviceUrl).path(urlPath).getRequestBuilder();
this.addExtraHeaders(resourceBuilder);
//把InstanceInfo作为参数，发送post请求提交服务注册response= (ClientResponse)((Builder)((Builder)((Builder)resourceBuilder.header("Accept-Encoding", "gzip")).type(MediaType.APPLICATION_JSON_TYPE)).accept(newString[]{"application/json"})).post(ClientResponse.class, info);
var5=EurekaHttpResponse.anEurekaHttpResponse(response.getStatus()).headers(headersOf(response)).build();
        } finally {
if (logger.isDebugEnabled()) {
logger.debug("Jersey HTTP POST {}/{} with instance {}; statusCode={}", newObject[]{this.serviceUrl, urlPath, info.getId(), response==null?"N/A" : response.getStatus()});
            }
if (response!=null) {
response.close();
            }
        }
returnvar5;
    }

到这里就结束了，在PeerEurekaNode中封装InstanceReplicationTask实例服务任务，通过EurekaHttpClient去发起请求(JerseyEurekaHttpClient)，最终通过JerseyEurekaHttpClient父类AbstractJerseyEurekaHttpClient#register方法注册，方法中把InstanceInfo作为参数使用POST提交请求。

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