程序入口
com.netflix.discovery.DiscoverClient
@PreDestroy
@Override
public synchronized void shutdown() {
if (isShutdown.compareAndSet(false, true)) {
logger.info("Shutting down DiscoveryClient ...");
if (statusChangeListener != null && applicationInfoManager != null) {
applicationInfoManager.unregisterStatusChangeListener(statusChangeListener.getId());
}
// 取消定时任务（心跳，缓存刷新等）
cancelScheduledTasks();
// 如果app注册过，那么需要取消注册，也就说需要主动下线
if (applicationInfoManager != null && clientConfig.shouldRegisterWithEureka()) {
// 设置实例的状态为DOWN
applicationInfoManager.setInstanceStatus(InstanceStatus.DOWN);
// 执行下线
unregister();
}
if (eurekaTransport != null) {
eurekaTransport.shutdown();
}
heartbeatStalenessMonitor.shutdown();
registryStalenessMonitor.shutdown();
logger.info("Completed shut down of DiscoveryClient");
}
}
在这个类被容器销毁的时候，会执行这个方法，执行主动下线的代码
unregister()
void unregister() {
// 如果是非注册的实例，那么eurekaTransport可能是为空的，所以做一下判断
if(eurekaTransport != null && eurekaTransport.registrationClient != null) {
try {
logger.info("Unregistering ...");
// 发送HTTP请求，到服务端，请求下线 ， 接口地址： "apps/" + appName + '/' + id;
EurekaHttpResponse<Void> httpResponse = eurekaTransport.registrationClient.cancel(instanceInfo.getAppName(), instanceInfo.getId());
logger.info(PREFIX + appPathIdentifier + " - deregister status: " + httpResponse.getStatusCode());
} catch (Exception e) {
logger.error(PREFIX + appPathIdentifier + " - de-registration failed" + e.getMessage(), e);
}
}
}
Eureka-Server
InstanceResource
com.netflix.eureka.resources.InstanceResource
@DELETE
public Response cancelLease(
@HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication) {
//执行下线请求
boolean isSuccess = registry.cancel(app.getName(), id,
"true".equals(isReplication));
if (isSuccess) {
logger.debug("Found (Cancel): " + app.getName() + " - " + id);
return Response.ok().build();
} else {
logger.info("Not Found (Cancel): " + app.getName() + " - " + id);
return Response.status(Status.NOT_FOUND).build();
}
}
InstanceRegistry
org.springframework.cloud.netflix.eureka.server.InstanceRegistry
@Override
public boolean cancel(String appName, String serverId, boolean isReplication) {
//发布取消事件
handleCancelation(appName, serverId, isReplication);
// 调用父类的取消方法
return super.cancel(appName, serverId, isReplication);
}
private void handleCancelation(String appName, String id, boolean isReplication) {
log("cancel " + appName + ", serverId " + id + ", isReplication " + isReplication);
publishEvent(new EurekaInstanceCanceledEvent(this, appName, id, isReplication));
}
父类PeerAwareInstanceRegistryImpl
@Override
public boolean cancel(final String appName, final String id,
final boolean isReplication) {
// 执行父类的取消方法
if (super.cancel(appName, id, isReplication)) {
//集群同步信息
replicateToPeers(Action.Cancel, appName, id, null, null, isReplication);
// Eureka-Server的保护机制
synchronized (lock) {
if (this.expectedNumberOfRenewsPerMin > 0) {
// Since the client wants to cancel it, reduce the threshold (1 for 30 seconds, 2 for a minute)
this.expectedNumberOfRenewsPerMin = this.expectedNumberOfRenewsPerMin - 2;
this.numberOfRenewsPerMinThreshold =
(int) (this.expectedNumberOfRenewsPerMin * serverConfig.getRenewalPercentThreshold());
}
}
return true;
}
return false;
}
PeerAwareInstanceRegistryImpl 的父类AbstractInstanceRegistry中是
取消下线的主要逻辑。
@Override
public boolean cancel(String appName, String id, boolean isReplication) {
return internalCancel(appName, id, isReplication);
}
/**
* {@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.
*/
protected boolean internalCancel(String appName, String id, boolean isReplication) {
try {
// 读锁
read.lock();
// 添加取消次数给监控信息，这里是个枚举类，收集了取消次数
CANCEL.increment(isReplication);
// 从本地的CurrentHashMap中，获取当前实例对应的Lease信息
Map<String, Lease<InstanceInfo>> gMap = registry.get(appName);
Lease<InstanceInfo> leaseToCancel = null;
if (gMap != null) {
// 移除信息 ， 如果客户端是集群模式，此处仅移除这个实例ID对应的信息
leaseToCancel = gMap.remove(id);
}
// 添加取消信息到取消队列，主要用于运维界面的信息统计
synchronized (recentCanceledQueue) {
recentCanceledQueue.add(new Pair<Long, String>(System.currentTimeMillis(), appName + "(" + id + ")"));
}
//移除这个实例ID对应的instance状态
InstanceStatus instanceStatus = overriddenInstanceStatusMap.remove(id);
if (instanceStatus != null) {
logger.debug("Removed instance id {} from the overridden map which has value {}", id, instanceStatus.name());
}
if (leaseToCancel == null) {
// 如果信息不存在，则说明这个实例从来没有注册过来，或者已经下线了。
CANCEL_NOT_FOUND.increment(isReplication);
logger.warn("DS: Registry: cancel failed because Lease is not registered for: {}/{}", appName, id);
return false;
} else {
// 更新Lease实例信息里面的evictionTimestamp这个时间戳，标明下线时间
leaseToCancel.cancel();
InstanceInfo instanceInfo = leaseToCancel.getHolder();
String vip = null;
String svip = null;
// 获取VIP，SVIP，然后把instance的变化加入实例变化队列中
if (instanceInfo != null) {
instanceInfo.setActionType(ActionType.DELETED);
recentlyChangedQueue.add(new RecentlyChangedItem(leaseToCancel));
instanceInfo.setLastUpdatedTimestamp();
vip = instanceInfo.getVIPAddress();
svip = instanceInfo.getSecureVipAddress();
}
// 显示的清楚缓存 ， guava的API
invalidateCache(appName, vip, svip);
logger.info("Cancelled instance {}/{} (replication={})", appName, id, isReplication);
return true;
}
} finally {
read.unlock();
}
}
综上可以看到，首先是从本地的CurrentHashMap中获取当前appName对应的的Map信息，最后通过机器ID，获取要下线的机器
对应的Lease，修改Lease的evictionTimestamp ， 也就是设置下线时间为当前时间点。
public void cancel() {
if (evictionTimestamp <= 0) {
evictionTimestamp = System.currentTimeMillis();
}
}
主动下线还是比较简单的
