Eureka服务注册过程

深碍√TFBOYSˉ_ 2022-07-12 02:13 182阅读 0赞

上篇博客《[SpringCloud——Eureka服务注册和发现][SpringCloud_Eureka]》介绍了Eureka的基本功能，这篇我们来聊聊eureka是如何实现的。

![Center][]

上图是eureka的架构图，Eureka分为Server和client，图中，蓝色为Server端，绿色为client。

基本流程：

1、最左边的client（即服务提供者）发起us-east-1c注册请求；

2、之后，Eureka Server集群中的其他两个node（us-east-1d和us-east-1e进行Replicate复制）；

3、图下放的两个client（即服务消费者）分别向三个server获取注册信息及Get Registry。

注册过程：

Eureka Client：

1、DiscoveryClient中的initScheduledTasks()以定时任务的方式执行。

private void initScheduledTasks() { 
    	instanceInfoReplicator = new InstanceInfoReplicator(
                        this,
                        instanceInfo,
                        clientConfig.getInstanceInfoReplicationIntervalSeconds(),
                        2); // burstSize            
    	instanceInfoReplicator.start(clientConfig.getInitialInstanceInfoReplicationIntervalSeconds());
    }

2、在InstanceInfoReplicator的run方法中，调用discoveryClient的注册方法。

public void run() {
    	        try {
    	            discoveryClient.refreshInstanceInfo();
    	
    	            Long dirtyTimestamp = instanceInfo.isDirtyWithTime();
    	            if (dirtyTimestamp != null) {
    	                discoveryClient.register();
    	                instanceInfo.unsetIsDirty(dirtyTimestamp);
    	            }
    	        } catch (Throwable t) {
    	            logger.warn("There was a problem with the instance info replicator", t);
    	        } finally {
    	            Future next = scheduler.schedule(this, replicationIntervalSeconds, TimeUnit.SECONDS);
    	            scheduledPeriodicRef.set(next);
    	        }
    	    }

3、DiscoveryClient，使用rest调用。

boolean register() throws Throwable {	        logger.info(PREFIX + appPathIdentifier + ": registering service...");
    	        EurekaHttpResponse<Void> httpResponse;
    	        try {
    	            httpResponse = eurekaTransport.registrationClient.register(instanceInfo);
    	        } catch (Exception e) {
    	            logger.warn("{} - registration failed {}", PREFIX + appPathIdentifier, e.getMessage(), e);
    	            throw e;
    	        }
    	        if (logger.isInfoEnabled()) {
    	            logger.info("{} - registration status: {}", PREFIX + appPathIdentifier, httpResponse.getStatusCode());
    	        }
    	        return httpResponse.getStatusCode() == 204;
    	    }

Eureka Server：

1、rest接口，即服务端rest方式调用的接口。

@POST
        @Consumes({"application/json", "application/xml"})
        public Response addInstance(InstanceInfo info,
                                    @HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication) {
            logger.debug("Registering instance {} (replication={})", info.getId(), isReplication);
            // validate that the instanceinfo contains all the necessary required fields
            if (isBlank(info.getId())) {
                return Response.status(400).entity("Missing instanceId").build();
            } else if (isBlank(info.getHostName())) {
                return Response.status(400).entity("Missing hostname").build();
            } else if (isBlank(info.getAppName())) {
                return Response.status(400).entity("Missing appName").build();
            } else if (!appName.equals(info.getAppName())) {
                return Response.status(400).entity("Mismatched appName, expecting " + appName + " but was " + info.getAppName()).build();
            } else if (info.getDataCenterInfo() == null) {
                return Response.status(400).entity("Missing dataCenterInfo").build();
            } else if (info.getDataCenterInfo().getName() == null) {
                return Response.status(400).entity("Missing dataCenterInfo Name").build();
            }
    
            // handle cases where clients may be registering with bad DataCenterInfo with missing data
            DataCenterInfo dataCenterInfo = info.getDataCenterInfo();
            if (dataCenterInfo instanceof UniqueIdentifier) {
                String dataCenterInfoId = ((UniqueIdentifier) dataCenterInfo).getId();
                if (isBlank(dataCenterInfoId)) {
                    boolean experimental = "true".equalsIgnoreCase(serverConfig.getExperimental("registration.validation.dataCenterInfoId"));
                    if (experimental) {
                        String entity = "DataCenterInfo of type " + dataCenterInfo.getClass() + " must contain a valid id";
                        return Response.status(400).entity(entity).build();
                    } else if (dataCenterInfo instanceof AmazonInfo) {
                        AmazonInfo amazonInfo = (AmazonInfo) dataCenterInfo;
                        String effectiveId = amazonInfo.get(AmazonInfo.MetaDataKey.instanceId);
                        if (effectiveId == null) {
                            amazonInfo.getMetadata().put(AmazonInfo.MetaDataKey.instanceId.getName(), info.getId());
                        }
                    } else {
                        logger.warn("Registering DataCenterInfo of type {} without an appropriate id", dataCenterInfo.getClass());
                    }
                }
            }
    
            registry.register(info, "true".equals(isReplication));
            return Response.status(204).build();  // 204 to be backwards compatible
        }

2、在PeerAwareInstanceRegistryImpl中的register方法

@Override
        public void register(final InstanceInfo info, final boolean isReplication) {
            int leaseDuration = Lease.DEFAULT_DURATION_IN_SECS;
            if (info.getLeaseInfo() != null && info.getLeaseInfo().getDurationInSecs() > 0) {
                leaseDuration = info.getLeaseInfo().getDurationInSecs();
            }
            super.register(info, leaseDuration, isReplication);
            replicateToPeers(Action.Register, info.getAppName(), info.getId(), info, null, isReplication);
        }

注册方法中，租约不存在。具体如下

if (existingLease != null && (existingLease.getHolder() != null)) { 
    	//续租
    	.......
    }else{  
           // The lease does not exist and hence it is a new registration          
    	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());
                        }
                    }
                    logger.debug("No previous lease information found; it is new registration");
    }

构造注册信息，处理缓存信息。

registrant.setActionType(ActionType.ADDED);
                recentlyChangedQueue.add(new RecentlyChangedItem(lease));
                registrant.setLastUpdatedTimestamp();
                invalidateCache(registrant.getAppName(), registrant.getVIPAddress(), registrant.getSecureVipAddress());
                logger.info("Registered instance {}/{} with status {} (replication={})",
                        registrant.getAppName(), registrant.getId(), registrant.getStatus(), isReplication);

[SpringCloud_Eureka]: http://blog.csdn.net/u010066934/article/details/54232622
[Center]: /images/20220711/df61351f6ebf460e910b6a5d559d25d7.png