上面第二段super.register()
public void register(InstanceInfo info, boolean isReplication) {
    int leaseDuration = 90;
    if (info.getLeaseInfo() != null && info.getLeaseInfo().getDurationInSecs() > 0) {
        leaseDuration = info.getLeaseInfo().getDurationInSecs();
    }
  //真正注册自己
    super.register(info, leaseDuration, isReplication);
    this.replicateToPeers(PeerAwareInstanceRegistryImpl.Action.Register, info.getAppName(), info.getId(), info, (InstanceStatus)null, isReplication);
}

public void register(InstanceInfo registrant, int leaseDuration, boolean isReplication) {
        this.read.lock();
        try {
            //通过服务名称得到注册的实例
            Map<String, Lease<InstanceInfo>> gMap = (Map)this.registry.get(registrant.getAppName());
            EurekaMonitors.REGISTER.increment(isReplication);
            //因为之前没有实例，肯定为 null
            if (gMap == null) {
                //新建一个集合来存放实例
                ConcurrentHashMap<String, Lease<InstanceInfo>> gNewMap = new ConcurrentHashMap();
                gMap = (Map)this.registry.putIfAbsent(registrant.getAppName(), gNewMap);
                if (gMap == null) {
                    gMap = gNewMap;
                }
            }
            //gMap 就是该服务的实例
            Lease<InstanceInfo> existingLease = (Lease)((Map)gMap).get(registrant.getId());
            if (existingLease != null && existingLease.getHolder() != null) {
                Long existingLastDirtyTimestamp = ((InstanceInfo)existingLease.getHolder()).getLastDirtyTimestamp();
                Long registrationLastDirtyTimestamp = registrant.getLastDirtyTimestamp();
                logger.debug("Existing lease found (existing={}, provided={}", existingLastDirtyTimestamp, registrationLastDirtyTimestamp);
                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 = (InstanceInfo)existingLease.getHolder();
                }
            } else {
                synchronized(this.lock) {
                    if (this.expectedNumberOfClientsSendingRenews > 0) {
                        ++this.expectedNumberOfClientsSendingRenews;
                        this.updateRenewsPerMinThreshold();
                    }
                }
                logger.debug("No previous lease information found; it is new registration");
            }
    //新建一个服务的实例节点
            Lease<InstanceInfo> lease = new Lease(registrant, leaseDuration);
            if (existingLease != null) {
                lease.setServiceUpTimestamp(existingLease.getServiceUpTimestamp());
            }
    //放到注册 map 的列表里
            ((Map)gMap).put(registrant.getId(), lease);
            this.recentRegisteredQueue.add(new Pair(System.currentTimeMillis(), registrant.getAppName() + "(" + registrant.getId() + ")"));
            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 (!this.overriddenInstanceStatusMap.containsKey(registrant.getId())) {
                    logger.info("Not found overridden id {} and hence adding it", registrant.getId());
                    this.overriddenInstanceStatusMap.put(registrant.getId(), registrant.getOverriddenStatus());
                }
            }
            InstanceStatus overriddenStatusFromMap = (InstanceStatus)this.overriddenInstanceStatusMap.get(registrant.getId());
            if (overriddenStatusFromMap != null) {
                logger.info("Storing overridden status {} from map", overriddenStatusFromMap);
                registrant.setOverriddenStatus(overriddenStatusFromMap);
            }
            InstanceStatus overriddenInstanceStatus = this.getOverriddenInstanceStatus(registrant, existingLease, isReplication);
            registrant.setStatusWithoutDirty(overriddenInstanceStatus);
            if (InstanceStatus.UP.equals(registrant.getStatus())) {
                lease.serviceUp();
            }
    //设置心跳时间等参数
            registrant.setActionType(ActionType.ADDED);
            this.recentlyChangedQueue.add(new AbstractInstanceRegistry.RecentlyChangedItem(lease));
            registrant.setLastUpdatedTimestamp();
            this.invalidateCache(registrant.getAppName(), registrant.getVIPAddress(), registrant.getSecureVipAddress());
            logger.info("Registered instance {}/{} with status {} (replication={})", new Object[]{registrant.getAppName(), registrant.getId(), registrant.getStatus(), isReplication});
        } finally {
            this.read.unlock();
        }
    }

第一个 key 是应用名称（全大写） spring.application.name
Value 中的 key 是应用的实例 id eureka.instance.instance-id
Value 中的 value 是 具体的服务节点信息
private final ConcurrentHashMap<String, Map<String, Lease<InstanceInfo>>> registry = new ConcurrentHashMap<String, Map<String, Lease<InstanceInfo>>>();

package com.changlu.eurekaclienta.controller;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import java.util.List;
/**
 * @Description: 我的服务注册发现
 * @Author: changlu
 * @Date: 10:04 PM
 */
@RestController
public class MyDiscoveryController {
    @Autowired
    private DiscoveryClient discoveryClient;//这个接口是springcloud提供的，然后eureka提供了对应的实现类
    @GetMapping("/find")
    public String find(String serviceId) {
        //调用服务发现
        List<ServiceInstance> instances = discoveryClient.getInstances(serviceId);
        instances.forEach(System.out::println);
        return instances.toString();
    }
}