1. 概述
本文主要分享 Eureka-Client 向 Eureka-Server 下线应用实例的过程。
FROM 《深度剖析服务发现组件Netflix Eureka》 二次编辑
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应用实例关闭时,Eureka-Client 向 Eureka-Server 发起下线应用实例。需要满足如下条件才可发起:
eureka.registration.enabled = true
,应用实例开启注册开关。默认为 false
。eureka.shouldUnregisterOnShutdown = true
,应用实例开启关闭时下线开关。默认为 true
。实现代码如下:
// DiscoveryClient.java
public synchronized void shutdown() {
// ... 省略无关代码
// If APPINFO was registered
if (applicationInfoManager != null
&& clientConfig.shouldRegisterWithEureka() // eureka.registration.enabled = true
&& clientConfig.shouldUnregisterOnShutdown()) { // eureka.shouldUnregisterOnShutdown = true
applicationInfoManager.setInstanceStatus(InstanceStatus.DOWN);
unregister();
}
}
ApplicationInfoManager#setInstanceStatus(...)
方法,设置应用实例为关闭( DOWN )。#unregister()
方法,实现代码如下:
// DiscoveryClient.java void unregister() { // It can be null if shouldRegisterWithEureka == false if(eurekaTransport != null && eurekaTransport.registrationClient != null) { try { logger.info("Unregistering ..."); 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); } } } // AbstractJerseyEurekaHttpClient.java @Override public EurekaHttpResponse<Void> cancel(String appName, String id) { String urlPath = "apps/" + appName + '/' + id; ClientResponse response = null; try { Builder resourceBuilder = jerseyClient.resource(serviceUrl).path(urlPath).getRequestBuilder(); addExtraHeaders(resourceBuilder); response = resourceBuilder.delete(ClientResponse.class); return anEurekaHttpResponse(response.getStatus()).headers(headersOf(response)).build(); } finally { if (logger.isDebugEnabled()) { logger.debug("Jersey HTTP DELETE {}/{}; statusCode={}", serviceUrl, urlPath, response == null ? "N/A" : response.getStatus()); } if (response != null) { response.close(); } } }AbstractJerseyEurekaHttpClient#cancel(...)
方法,DELETE
请求 Eureka-Server 的 apps/${APP_NAME}/${INSTANCE_INFO_ID}
接口,实现应用实例信息的下线。com.netflix.eureka.resources.InstanceResource
,处理单个应用实例信息的请求操作的 Resource ( Controller )。
下线应用实例信息的请求,映射 InstanceResource#cancelLease()
方法,实现代码如下:
@DELETE
public Response cancelLease(
@HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication) {
// 下线
boolean isSuccess = registry.cancel(app.getName(), id, "true".equals(isReplication));
if (isSuccess) { // 下线成功
logger.debug("Found (Cancel): " + app.getName() + " - " + id);
return Response.ok().build();
} else { // 下线成功
logger.info("Not Found (Cancel): " + app.getName() + " - " + id);
return Response.status(Status.NOT_FOUND).build();
}
}
PeerAwareInstanceRegistryImpl#cancel(...)
方法,下线应用实例。实现代码如下:
1: @Override 2: public boolean cancel(final String appName, final String id, 3: final boolean isReplication) { 4: if (super.cancel(appName, id, isReplication)) { // 下线 5: // Eureka-Server 复制 6: replicateToPeers(Action.Cancel, appName, id, null, null, isReplication); 7: // 减少 `numberOfRenewsPerMinThreshold` 、`expectedNumberOfRenewsPerMin` 8: synchronized (lock) { 9: if (this.expectedNumberOfRenewsPerMin > 0) { 10: // Since the client wants to cancel it, reduce the threshold (1 for 30 seconds, 2 for a minute) 11: this.expectedNumberOfRenewsPerMin = this.expectedNumberOfRenewsPerMin - 2; 12: this.numberOfRenewsPerMinThreshold = (int) (this.expectedNumberOfRenewsPerMin * serverConfig.getRenewalPercentThreshold()); 13: } 14: } 15: return true; 16: } 17: return false; 18: }AbstractInstanceRegistry#cancel(...)
方法,下线应用实例信息。numberOfRenewsPerMinThreshold
、expectedNumberOfRenewsPerMin
,自我保护机制相关,在 《Eureka 源码解析 —— 应用实例注册发现(四)之自我保护机制》 有详细解析。调用 AbstractInstanceRegistry#cancel(...)
方法,下线应用实例信息,实现代码如下:
1: @Override
2: public boolean cancel(String appName, String id, boolean isReplication) {
3: return internalCancel(appName, id, isReplication);
4: }
5:
6: protected boolean internalCancel(String appName, String id, boolean isReplication) {
7: try {
8: // 获得读锁
9: read.lock();
10: // 增加 取消注册次数 到 监控
11: CANCEL.increment(isReplication);
12: // 移除 租约映射
13: Map<String, Lease<InstanceInfo>> gMap = registry.get(appName);
14: Lease<InstanceInfo> leaseToCancel = null;
15: if (gMap != null) {
16: leaseToCancel = gMap.remove(id);
17: }
18: // 添加到 最近取消注册的调试队列
19: synchronized (recentCanceledQueue) {
20: recentCanceledQueue.add(new Pair<Long, String>(System.currentTimeMillis(), appName + "(" + id + ")"));
21: }
22: // 移除 应用实例覆盖状态映射
23: InstanceStatus instanceStatus = overriddenInstanceStatusMap.remove(id);
24: if (instanceStatus != null) {
25: logger.debug("Removed instance id {} from the overridden map which has value {}", id, instanceStatus.name());
26: }
27: // 租约不存在
28: if (leaseToCancel == null) {
29: CANCEL_NOT_FOUND.increment(isReplication); // 添加 取消注册不存在 到 监控
30: logger.warn("DS: Registry: cancel failed because Lease is not registered for: {}/{}", appName, id);
31: return false; // 失败
32: } else {
33: // 设置 租约的取消注册时间戳
34: leaseToCancel.cancel();
35: // 添加到 最近租约变更记录队列
36: InstanceInfo instanceInfo = leaseToCancel.getHolder();
37: String vip = null;
38: String svip = null;
39: if (instanceInfo != null) {
40: instanceInfo.setActionType(ActionType.DELETED);
41: recentlyChangedQueue.add(new RecentlyChangedItem(leaseToCancel));
42: instanceInfo.setLastUpdatedTimestamp();
43: vip = instanceInfo.getVIPAddress();
44: svip = instanceInfo.getSecureVipAddress();
45: }
46: // 设置 响应缓存 过期
47: invalidateCache(appName, vip, svip);
48: logger.info("Cancelled instance {}/{} (replication={})", appName, id, isReplication);
49: return true; // 成功
50: }
51: } finally {
52: // 释放锁
53: read.unlock();
54: }
55: }
registry
)。recentCanceledQueue
),用于 Eureka-Server 运维界面的显示,无实际业务逻辑使用。实现代码如下:
/** * 最近取消注册的调试队列 * key :添加时的时间戳 * value :字符串 = 应用名(应用实例信息编号) */ private final CircularQueue<Pair<Long, String>> recentCanceledQueue;false
)。Lease#cancel()
方法,取消租约。实现代码如下:
// Lease.java public void cancel() { if (evictionTimestamp <= 0) { evictionTimestamp = System.currentTimeMillis(); } }recentlyChangedQueue
)。recentlyChangedQueue
用于注册信息的增量获取,在《应用实例注册发现 (七)之增量获取》详细解析。实现代码如下:
/** * 最近租约变更记录队列 */ private ConcurrentLinkedQueue<RecentlyChangedItem> recentlyChangedQueue = new ConcurrentLinkedQueue<RecentlyChangedItem>();false
)。