续约
续约的时候，调用的是服务端的InstanceResource#renewLease办法。调用的是InstanceRegistry.renew办法。
@PUTpublic 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); //其余略 return response;}InstanceRegistry.renew会发一个EventPublish的续约监听（代码略），而后调用PeerAwareInstanceRegistryImpl#renew。PeerAwareInstanceRegistryImpl#renew。会调用AbstractInstanceRegistry#renew，如果胜利，会进行节点间的复制。
public boolean renew(final String appName, final String id, final boolean isReplication) { if (super.renew(appName, id, isReplication)) { replicateToPeers(Action.Heartbeat, appName, id, null, null, isReplication); return true; } return false;}AbstractInstanceRegistry#renew，获取续约，如果有的话。
public boolean renew(String appName, String id, boolean isReplication) { RENEW.increment(isReplication); Map<String, Lease<InstanceInfo>> gMap = registry.get(appName); Lease<InstanceInfo> 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 { // 其余略 renewsLastMin.increment(); leaseToRenew.renew(); return true; }}Lease#renew，更新lastUpdateTimestamp工夫。
public void renew() { lastUpdateTimestamp = System.currentTimeMillis() + duration;}综上，续约就是更改lastUpdateTimestamp的工夫。
注册
注册调用的是server的ApplicationResource#addInstance，他调用InstanceRegistry#register，和下面一样，这个会公布注册监听。
public Response addInstance(InstanceInfo info, @HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication) { //其余略 registry.register(info, "true".equals(isReplication)); return Response.status(204).build(); // 204 to be backwards compatible}InstanceRegistry#register会调用PeerAwareInstanceRegistryImpl#register，理论的注册是AbstractInstanceRegistry#register办法，这个办法在Eureka - Server服务启动曾经提过了，这里略。注册胜利后，会进行节点间的复制。
@Overridepublic 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);}下线
下线调用的是InstanceResource#cancelLease，而后他会调用InstanceRegistry#cancel（代码略）公布下线监听。
@DELETEpublic Response cancelLease( @HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication) { //其余略 boolean isSuccess = registry.cancel(app.getName(), id, "true".equals(isReplication)); //其余略}InstanceRegistry#cancel调用PeerAwareInstanceRegistryImpl#cancel，下线胜利后，会进行节点间的复制。
@Overridepublic boolean cancel(final String appName, final String id, final boolean isReplication) { if (super.cancel(appName, id, isReplication)) { replicateToPeers(Action.Cancel, appName, id, null, null, isReplication); return true; } return false;}AbstractInstanceRegistry#cancel会调用AbstractInstanceRegistry#internalCancel，这个是外围代码。这里会设置勾销工夫戳，并过期读写缓存。
@Overridepublic boolean cancel(String appName, String id, boolean isReplication) { return internalCancel(appName, id, isReplication);}protected boolean internalCancel(String appName, String id, boolean isReplication) { read.lock(); try { //其余略 // 设置勾销的工夫戳 leaseToCancel.cancel(); //其余略 // 过期缓存，这里是读写缓存 invalidateCache(appName, vip, svip); } } finally { read.unlock(); } // 用于自我爱护 synchronized (lock) { if (this.expectedNumberOfClientsSendingRenews > 0) { // Since the client wants to cancel it, reduce the number of clients to send renews. this.expectedNumberOfClientsSendingRenews = this.expectedNumberOfClientsSendingRenews - 1; updateRenewsPerMinThreshold(); } } return true;}另外，Eureka - Server服务启动提到了EvictionTask#run，他会革除过期的实例，他也会调用AbstractInstanceRegistry#internalCancel办法，所以读写缓存的图更改为：
bug
咱们看到，续约的时候lastUpdateTimestamp = System.currentTimeMillis() + duration;，判断是否过期的时候，又加了一个duration，所以他剔除的并不是90秒没有心跳的，而是180秒没有心跳的。
public boolean isExpired(long additionalLeaseMs) { return (evictionTimestamp > 0 || System.currentTimeMillis() > (lastUpdateTimestamp + duration + additionalLeaseMs));}