SpringCloud源码剖析-Eureka Server服务下线-阿里云开发者社区

SpringCloud源码剖析-Eureka Server服务下线

2023-07-29 58

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简介： 1.从registry中移除服务，2.从overriddenInstanceStatusMap状态map中移除服务状态3.添加到最近取消队列4.调用Lease.cancel方法，将租约对象中的逐出时间修改为当前时间5.修改服务的InstanceInfo的状态为DELETE6.添加到最近修改队列7.更新服务最后修改时间8.使ReponseCache缓存无

Eureka Server 服务下线

在《Eureka Client取消注册》中我们有分析到，当Eureka Client 客户端当服务关闭，触发客户端服务下线方法，客户端执行一系列下线逻辑后会向Eureka Server服务端发送服务下线请求，服务端处理下线的请求是在com.netflix.eureka.resources.InstanceResource#cancelLease方法中

/**处理此特定实例的租赁取消* Handles cancellation of leases for this particular instance.** @param isReplication*            a header parameter containing information whether this is*            replicated from other nodes.* @return response indicating whether the operation was a success or*         failure.*/@DELETEpublicResponsecancelLease(
@HeaderParam(PeerEurekaNode.HEADER_REPLICATION) StringisReplication) {
try {
//调用 InstanceRegistry的 cancel 方法下线服务booleanisSuccess=registry.cancel(app.getName(), id,
"true".equals(isReplication));
if (isSuccess) {
logger.debug("Found (Cancel): {} - {}", app.getName(), id);
returnResponse.ok().build();
        } else {
logger.info("Not Found (Cancel): {} - {}", app.getName(), id);
returnResponse.status(Status.NOT_FOUND).build();
        }
    } catch (Throwablee) {
logger.error("Error (cancel): {} - {}", app.getName(), id, e);
returnResponse.serverError().build();
    }
}

InstanceRegistry的 cancel 方法

publicclassInstanceRegistryextendsPeerAwareInstanceRegistryImplimplementsApplicationContextAware {
@Overridepublicbooleancancel(StringappName, StringserverId, booleanisReplication) {
//抛出EurekaInstanceCanceledEvent取消事件handleCancelation(appName, serverId, isReplication);
//调用PeerAwareInstanceRegistryImpl#cancelreturnsuper.cancel(appName, serverId, isReplication);
   }
//抛出EurekaInstanceCanceledEvent取消事件privatevoidhandleCancelation(StringappName, Stringid, booleanisReplication) {
log("cancel "+appName+", serverId "+id+", isReplication "+isReplication);
publishEvent(newEurekaInstanceCanceledEvent(this, appName, id, isReplication));
   }

这里比较简单，抛出EurekaInstanceCanceledEvent时间后调用super(PeerAwareInstanceRegistryImpl)的下线方法

/** (non-Javadoc)** @see com.netflix.eureka.registry.InstanceRegistry#cancel(java.lang.String,* java.lang.String, long, boolean)*/@Overridepublicbooleancancel(finalStringappName, finalStringid,
finalbooleanisReplication) {
//调用super.cancel下线方法：com.netflix.eureka.registry.AbstractInstanceRegistry#cancelif (super.cancel(appName, id, isReplication)) {
//复制到其他的Eureka节点replicateToPeers(Action.Cancel, appName, id, null, null, isReplication);
synchronized (lock) {
if (this.expectedNumberOfRenewsPerMin>0) {
//如果每分钟的预期续订次数大于0//由于客户想取消该阈值，因此降低阈值（1次 30秒，2次 1分钟）// Since the client wants to cancel it, reduce the threshold (1 for 30 seconds, 2 for a minute)//预期续订次数 = 预期续订次数 -2 （2次 1分钟 ， 1次 30）this.expectedNumberOfRenewsPerMin=this.expectedNumberOfRenewsPerMin-2;
//续订次数阈值  = 预期续订次数  * 0.85this.numberOfRenewsPerMinThreshold=                    (int) (this.expectedNumberOfRenewsPerMin*serverConfig.getRenewalPercentThreshold());
            }
        }
returntrue;
    }
returnfalse;
}

这里继续调用super.cancel（AbstractInstanceRegistry#cancel），完成下线后重新计算了续约阈值，继续看AbstractInstanceRegistry#cancel方法

publicabstractclassAbstractInstanceRegistryimplementsInstanceRegistry {
/**//取消实例注册//这通常是由客户端调用时关闭通知服务器从流量中除去实例* Cancels the registration of an instance.** <p>* This is normally invoked by a client when it shuts down informing the* server to remove the instance from traffic.* </p>** @param appName the application name of the application.* @param id the unique identifier of the instance.* @param isReplication true if this is a replication event from other nodes, false*                      otherwise.* @return true if the instance was removed from the {@link AbstractInstanceRegistry} successfully, false otherwise.*/@Overridepublicbooleancancel(StringappName, Stringid, booleanisReplication) {
returninternalCancel(appName, id, isReplication);
    }
/**内部取消服务注册* {@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();
        }
    }
}