SpringCloud源码阅读1-EurekaServer源码的秘密（下）

public void evict(long additionalLeaseMs) {
        // 判断是否开启自我保护，自我保护期间不剔除任何任务
        if (!isLeaseExpirationEnabled()) {
            logger.debug("DS: lease expiration is currently disabled.");
            return;
        }
        List<Lease<InstanceInfo>> expiredLeases = new ArrayList<>();
        //循环获得 所有过期的租约
        for (Entry<String, Map<String, Lease<InstanceInfo>>> groupEntry : registry.entrySet()) {
            Map<String, Lease<InstanceInfo>> leaseMap = groupEntry.getValue();
            if (leaseMap != null) {
                for (Entry<String, Lease<InstanceInfo>> leaseEntry : leaseMap.entrySet()) {
                    Lease<InstanceInfo> lease = leaseEntry.getValue();
                     // 判断是否过期
                    if (lease.isExpired(additionalLeaseMs) && lease.getHolder() != null) {
                        expiredLeases.add(lease);
                    }
                }
            }
        }
    // 计算 最大允许清理租约数量
        int registrySize = (int) getLocalRegistrySize();
        int registrySizeThreshold = (int) (registrySize * serverConfig.getRenewalPercentThreshold());
        int evictionLimit = registrySize - registrySizeThreshold;
    // 计算 清理租约数量
        int toEvict = Math.min(expiredLeases.size(), evictionLimit);
        if (toEvict > 0) {
            Random random = new Random(System.currentTimeMillis());
            // 遍历清理。
            for (int i = 0; i < toEvict; i++) { 
                int next = i + random.nextInt(expiredLeases.size() - i);
                Collections.swap(expiredLeases, i, next);
                Lease<InstanceInfo> lease = expiredLeases.get(i);
                String appName = lease.getHolder().getAppName();
                String id = lease.getHolder().getId();
                EXPIRED.increment();
                internalCancel(appName, id, false);
            }
        }
    }

public boolean isExpired(long additionalLeaseMs) {
        return (
        //或者明确实例下线时间。
        evictionTimestamp > 0 
        //或者距离最后更新时间已经过去至少3分钟
        || System.currentTimeMillis() > (lastUpdateTimestamp + duration + additionalLeaseMs));
    }

//续约时更新lastUpdateTimestamp，加上了过期间隔？
public void renew() {
        lastUpdateTimestamp = System.currentTimeMillis() + duration;
}

@POST
    @Consumes({"application/json", "application/xml"})
    public Response addInstance(InstanceInfo info,
                                @HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication) {
    ....
    //使用PeerAwareInstanceRegistryImpl#register() 注册实例信息。
        registry.register(info, "true".equals(isReplication));
        return Response.status(204).build();  // 204 to be backwards compatible
    }

InstanceRegistry
@Override
  public void register(final InstanceInfo info, final boolean isReplication) {
    //发布注册事件，
    handleRegistration(info, resolveInstanceLeaseDuration(info), isReplication);
    super.register(info, isReplication);
}
PeerAwareInstanceRegistryImpl
@Override
    public void register(final InstanceInfo info, final boolean isReplication) {
        //租期90s
        int leaseDuration = Lease.DEFAULT_DURATION_IN_SECS;
        if (info.getLeaseInfo() != null && info.getLeaseInfo().getDurationInSecs() > 0) {
            leaseDuration = info.getLeaseInfo().getDurationInSecs();
        }
        //注册实例
        super.register(info, leaseDuration, isReplication);
        //复制到其他节点。
        replicateToPeers(Action.Register, info.getAppName(), info.getId(), info, null, isReplication);
    }

AbstractInstanceRegistry
public void register(InstanceInfo registrant, int leaseDuration, boolean isReplication) {
  read.lock()读锁
  1.从缓存中获取实例名称对应的租约信息
  Map<String, Lease<InstanceInfo>> gMap = registry.get(registrant.getAppName());
            REGISTER.increment(isReplication);
    2.统计数+1
    REGISTER.increment(isReplication); 
    //gmap为null.则创建一个Map。
  3.租约的处理分两种情况：
  租约已经存在：
      比较新租约与旧租约的LastDirtyTimestamp，使用LastDirtyTimestamp最晚的租约
  租约不存在，即新注册：        
      synchronized (lock) {
        更新期待每分钟续约数
        更新续约阈值
      }
  将租约放入appname对应的map中。
  4.在最近注册队(recentRegisteredQueue)里添加一个当前注册信息
  5.状态的处理：
    将当前实例的OverriddenStatus状态，放到Eureka Server的overriddenInstanceStatusMap；
    根据OverriddenStatus状态，设置状态
  7.实例actionType=ADDED
  registrant.setActionType(ActionType.ADDED);
    8. 维护recentlyChangedQueue，保存最近操作
    recentlyChangedQueue.add(new RecentlyChangedItem(lease));
    9.更新最后更新时间
    registrant.setLastUpdatedTimestamp();
    10.使当前实例的结果缓存ResponseCache失效()
    invalidateCache(registrant.getAppName(), registrant.getVIPAddress(), registrant.getSecureVipAddress());
}

@GET
    public Response getApplication(@PathParam("version") String version,
                                   @HeaderParam("Accept") final String acceptHeader,
                                   @HeaderParam(EurekaAccept.HTTP_X_EUREKA_ACCEPT) String eurekaAccept) {
        if (!registry.shouldAllowAccess(false)) {
            return Response.status(Status.FORBIDDEN).build();
        }
        EurekaMonitors.GET_APPLICATION.increment();
        CurrentRequestVersion.set(Version.toEnum(version));
        KeyType keyType = Key.KeyType.JSON;
        if (acceptHeader == null || !acceptHeader.contains("json")) {
            keyType = Key.KeyType.XML;
        }
        Key cacheKey = new Key(
                Key.EntityType.Application,
                appName,
                keyType,
                CurrentRequestVersion.get(),
                EurekaAccept.fromString(eurekaAccept)
        );
        String payLoad = responseCache.get(cacheKey);
        if (payLoad != null) {
            logger.debug("Found: {}", appName);
            return Response.ok(payLoad).build();
        } else {
            logger.debug("Not Found: {}", appName);
            return Response.status(Status.NOT_FOUND).build();
        }
    }