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