Eureka服务下线源码解析

我们知道，在Eureka中，可以使用如下方法使Eureka主动下线，那么本篇文章就来分析一下子这个下线的流程

主要做了这么几件事：

1. 解除状态监听器

2. 取消心跳、刷新线程

3. private void cancelScheduledTasks() {	
        if (instanceInfoReplicator != null) {	
            instanceInfoReplicator.stop();	
        }	
        if (heartbeatExecutor != null) {	
            heartbeatExecutor.shutdownNow();	
        }	
        if (cacheRefreshExecutor != null) {	
            cacheRefreshExecutor.shutdownNow();	
        }	
        if (scheduler != null) {	
            scheduler.shutdownNow();	
        }	
    }

4. 向服务端发起下线通知

void unregister() {	
        // It can be null if shouldRegisterWithEureka == false	
        if(eurekaTransport != null && eurekaTransport.registrationClient != null) {	
            try {	
                logger.info("Unregistering ...");	
                EurekaHttpResponse httpResponse = eurekaTransport.registrationClient.cancel(instanceInfo.getAppName(), instanceInfo.getId());	
                logger.info(PREFIX + "{} - deregister  status: {}", appPathIdentifier, httpResponse.getStatusCode());	
            } catch (Exception e) {	
                logger.error(PREFIX + "{} - de-registration failed{}", appPathIdentifier, e.getMessage(), e);	
            }	
        }	
    }	

	
    @Override	
    public EurekaHttpResponse 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();	
            }	
        }	
    }

4. 停止各个监听器

服务端接受下线消息

下线消息的处理在InstanceResource类中

@DELETE	
    public Response cancelLease(	
            @HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication) {	
        try {	
            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();	
            }	
        } catch (Throwable e) {	
            logger.error("Error (cancel): {} - {}", app.getName(), id, e);	
            return Response.serverError().build();	
        }	

	
    }	
 public boolean cancel(final String appName, final String id,	
                          final boolean isReplication) {	
        if (super.cancel(appName, id, isReplication)) {	
          //往集群同步下线信息	
            replicateToPeers(Action.Cancel, appName, id, null, null, isReplication);	
            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;	
    }

先看具体的下线逻辑，与租约过期清除的处理逻辑是一致的

protected boolean internalCancel(String appName, String id, boolean isReplication) {	
        try {	
            read.lock();	
            CANCEL.increment(isReplication);	
            Map> gMap = registry.get(appName);	
            Lease leaseToCancel = null;	
            if (gMap != null) {	
              //删除租约信息	
                leaseToCancel = gMap.remove(id);	
            }	
            synchronized (recentCanceledQueue) {	
                recentCanceledQueue.add(new Pair(System.currentTimeMillis(), appName + "(" + id + ")"));	
            }	
          //删除客户端状态信息	
            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) {	
                CANCEL_NOT_FOUND.increment(isReplication);	
                logger.warn("DS: Registry: cancel failed because Lease is not registered for: {}/{}", appName, id);	
                return false;	
            } else {	
                leaseToCancel.cancel();	
                InstanceInfo instanceInfo = leaseToCancel.getHolder();	
                String vip = null;	
                String svip = null;	
                if (instanceInfo != null) {	
                    instanceInfo.setActionType(ActionType.DELETED);	
                    recentlyChangedQueue.add(new RecentlyChangedItem(leaseToCancel));	
                    instanceInfo.setLastUpdatedTimestamp();	
                    vip = instanceInfo.getVIPAddress();	
                    svip = instanceInfo.getSecureVipAddress();	
                }	
                invalidateCache(appName, vip, svip);	
                logger.info("Cancelled instance {}/{} (replication={})", appName, id, isReplication);	
                return true;	
            }	
        } finally {	
            read.unlock();	
        }	
    }

其中invalidateCache则是删除当前服务中与该实例相关的缓存

集群的同步下线信息则跟集群信息注册的逻辑差不多

往期好文

 

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