SpringCloud源码剖析-Eureka Server服务剔除

publicabstractclassAbstractInstanceRegistryimplementsInstanceRegistry {
protectedvoidpostInit() {
renewsLastMin.start();
if (evictionTaskRef.get() !=null) {
//如果服务剔除任务不为空，就执行cancel方法，该方法把任务的状态修改为了cancel任务取消evictionTaskRef.get().cancel();
        }
//创建新的服务剔除任务evictionTaskRef.set(newEvictionTask());
//交给调度器去执行，延迟60s,每60s执行一次驱逐任务evictionTimer.schedule(evictionTaskRef.get(),
serverConfig.getEvictionIntervalTimerInMs(), //60s 逐出间隔计时器serverConfig.getEvictionIntervalTimerInMs());    
    }
/* visible for testing */classEvictionTaskextendsTimerTask {
privatefinalAtomicLonglastExecutionNanosRef=newAtomicLong(0l);
@Overridepublicvoidrun() {
try {
//计算任务执行的时间偏差：补偿时间longcompensationTimeMs=getCompensationTimeMs();
logger.info("Running the evict task with compensationTime {}ms", compensationTimeMs);
//执行驱逐evict(compensationTimeMs);
            } catch (Throwablee) {
logger.error("Could not run the evict task", e);
            }
        }

publicvoidevict(longadditionalLeaseMs) {
logger.debug("Running the evict task");
if (!isLeaseExpirationEnabled()) {
//如果没启用租约到期，直接返回logger.debug("DS: lease expiration is currently disabled.");
return;
    }
//首先收集所有过期的服务，以随机顺序将其逐出// We collect first all expired items, to evict them in random order. For large eviction sets,// if we do not that, we might wipe out whole apps before self preservation kicks in. By randomizing it,// the impact should be evenly distributed across all applications.List<Lease<InstanceInfo>>expiredLeases=newArrayList<>();
//循环注册表中的所有的服务for (Entry<String, Map<String, Lease<InstanceInfo>>>groupEntry : registry.entrySet()) {
Map<String, Lease<InstanceInfo>>leaseMap=groupEntry.getValue();
if (leaseMap!=null) {
//获取到租约for (Entry<String, Lease<InstanceInfo>>leaseEntry : leaseMap.entrySet()) {
Lease<InstanceInfo>lease=leaseEntry.getValue();
//如果服务过期，就把服务添加到expiredLeases map中if (lease.isExpired(additionalLeaseMs) &&lease.getHolder() !=null) {
expiredLeases.add(lease);
                }
            }
        }
    }
//为了补偿GC暂停或本地时间差异导致的剔除任务执行时间差异，使用当前注册表大小作为触发自我保存的基础//否则，将清除完整的注册表。// To compensate for GC pauses or drifting local time, we need to use current registry size as a base for// triggering self-preservation. Without that we would wipe out full registry.//注册表大小intregistrySize= (int) getLocalRegistrySize();
//注册表中服务的续约阈值 = 注册大小 * 0.85intregistrySizeThreshold= (int) (registrySize*serverConfig.getRenewalPercentThreshold());
//驱逐极限 = 注册表大小 - 注册表续约阈值 intevictionLimit=registrySize-registrySizeThreshold;
//过期的服务数 和 evictionLimit  取最小 ，如果大于 0 说明需要有服务要剔除inttoEvict=Math.min(expiredLeases.size(), evictionLimit);
if (toEvict>0) {
//剔除 toEvict 个logger.info("Evicting {} items (expired={}, evictionLimit={})", toEvict, expiredLeases.size(), evictionLimit);
//取随机值Randomrandom=newRandom(System.currentTimeMillis());
for (inti=0; i<toEvict; i++) {
//选择一个随机项目（Knuth随机算法），随机剔除// Pick a random item (Knuth shuffle algorithm)intnext=i+random.nextInt(expiredLeases.size() -i);
Collections.swap(expiredLeases, i, next);
//获取剔除服务的LeaseLease<InstanceInfo>lease=expiredLeases.get(i);
//应用名StringappName=lease.getHolder().getAppName();
//实例IDStringid=lease.getHolder().getId();
//expired Counter 过期计数增加EXPIRED.increment();
logger.warn("DS: Registry: expired lease for {}/{}", appName, id);          //内部取消internalCancel(appName, id, false);
        }
    }
}

/*** Checks if the lease of a given {@link com.netflix.appinfo.InstanceInfo} has expired or not.** Note that due to renew() doing the 'wrong" thing and setting lastUpdateTimestamp to +duration more than* what it should be, the expiry will actually be 2 * duration. This is a minor bug and should only affect* instances that ungracefully shutdown. Due to possible wide ranging impact to existing usage, this will* not be fixed.** @param additionalLeaseMs any additional lease time to add to the lease evaluation in ms.*/publicbooleanisExpired(longadditionalLeaseMs) {
return (evictionTimestamp>0||System.currentTimeMillis() > (lastUpdateTimestamp+duration+additionalLeaseMs));
}

publicvoidrenew() {
lastUpdateTimestamp=System.currentTimeMillis() +duration;
}

/*** {@link #cancel(String, String, boolean)} method is overridden by {@link PeerAwareInstanceRegistry}, so each* cancel request is replicated to the peers. This is however not desired for expires which would be counted* in the remote peers as valid cancellations, so self preservation mode would not kick-in.*/protectedbooleaninternalCancel(StringappName, Stringid, booleanisReplication) {
try {
//上锁read.lock();
//服务取消数增加CANCEL.increment(isReplication);
//获取当前提出的服务Map<String, Lease<InstanceInfo>>gMap=registry.get(appName);
Lease<InstanceInfo>leaseToCancel=null;
if (gMap!=null) {
//从服务注册的map中移除掉当前服务leaseToCancel=gMap.remove(id);
        }
//添加到最近取消队列synchronized (recentCanceledQueue) {
recentCanceledQueue.add(newPair<Long, String>(System.currentTimeMillis(), appName+"("+id+")"));
        }
//overriddenInstanceStatusMap 服务状态map中移除当前服务InstanceStatusinstanceStatus=overriddenInstanceStatusMap.remove(id);
if (instanceStatus!=null) {
logger.debug("Removed instance id {} from the overridden map which has value {}", id, instanceStatus.name());
        }
if (leaseToCancel==null) {
//没找到服务CANCEL_NOT_FOUND.increment(isReplication);
logger.warn("DS: Registry: cancel failed because Lease is not registered for: {}/{}", appName, id);
returnfalse;
        } else {
//调用Lease.cancel方法leaseToCancel.cancel();
//获取服务实例信息InstanceInfoinstanceInfo=leaseToCancel.getHolder();
Stringvip=null;
Stringsvip=null;
if (instanceInfo!=null) {
//实例状态修改为删除instanceInfo.setActionType(ActionType.DELETED);
//添加最近修改队列recentlyChangedQueue.add(newRecentlyChangedItem(leaseToCancel));
//实例信息对象修改最后修改时间instanceInfo.setLastUpdatedTimestamp();
vip=instanceInfo.getVIPAddress();
svip=instanceInfo.getSecureVipAddress();
            }
//使缓存无效,调用responseCache.invalidate让服务在缓存中失效invalidateCache(appName, vip, svip);
logger.info("Cancelled instance {}/{} (replication={})", appName, id, isReplication);
returntrue;
        }
    } finally {
read.unlock();
    }
}