SpringCloud学习笔记（3）----Spring Cloud Netflix之深入理解Eureka

　　

1. Eureka服务端的启动过程

　　1.1  入口类EurekaServerInitializerConfiguration类，

public void start() {
        (new Thread(new Runnable() {
            public void run() {
                try {
                    EurekaServerInitializerConfiguration.this.eurekaServerBootstrap.contextInitialized(EurekaServerInitializerConfiguration.this.servletContext);
                    EurekaServerInitializerConfiguration.log.info("Started Eureka Server");
                    EurekaServerInitializerConfiguration.this.publish(new EurekaRegistryAvailableEvent(EurekaServerInitializerConfiguration.this.getEurekaServerConfig()));
                    EurekaServerInitializerConfiguration.this.running = true;
                    EurekaServerInitializerConfiguration.this.publish(new EurekaServerStartedEvent(EurekaServerInitializerConfiguration.this.getEurekaServerConfig()));
                } catch (Exception var2) {
                    EurekaServerInitializerConfiguration.log.error("Could not initialize Eureka servlet context", var2);
                }

            }
        })).start();
    }

　通过start()方法来加载上下文和相关的Server端的配置信息，该类上面使用了@Configuration注解，会被spring bean容器感知到。

　　2. Eureka的初始化

　　EurekaServerBootstrap类的contextInitialized方法

　　

 public void contextInitialized(ServletContext context) {
        try {
            this.initEurekaEnvironment(); //环境初始化
            this.initEurekaServerContext(); //服务初始化
            context.setAttribute(EurekaServerContext.class.getName(), this.serverContext);
        } catch (Throwable var3) {
            log.error("Cannot bootstrap eureka server :", var3);
            throw new RuntimeException("Cannot bootstrap eureka server :", var3);
        }
    }

　　查找服务初始化中的Evicetion

　　

protected void initEurekaServerContext() throws Exception {
        JsonXStream.getInstance().registerConverter(new V1AwareInstanceInfoConverter(), 10000);
        XmlXStream.getInstance().registerConverter(new V1AwareInstanceInfoConverter(), 10000);
        if (this.isAws(this.applicationInfoManager.getInfo())) {
            this.awsBinder = new AwsBinderDelegate(this.eurekaServerConfig, this.eurekaClientConfig, this.registry, this.applicationInfoManager);
            this.awsBinder.start();
        }

        EurekaServerContextHolder.initialize(this.serverContext);
        log.info("Initialized server context");
        int registryCount = this.registry.syncUp();
        this.registry.openForTraffic(this.applicationInfoManager, registryCount);
        EurekaMonitors.registerAllStats();
    }

　　openForTraffic()

 public void openForTraffic(ApplicationInfoManager applicationInfoManager, int count) {
        this.expectedNumberOfRenewsPerMin = count * 2;
        this.numberOfRenewsPerMinThreshold = (int)((double)this.expectedNumberOfRenewsPerMin * this.serverConfig.getRenewalPercentThreshold());
        logger.info("Got {} instances from neighboring DS node", count);
        logger.info("Renew threshold is: {}", this.numberOfRenewsPerMinThreshold);
        this.startupTime = System.currentTimeMillis();
        if (count > 0) {
            this.peerInstancesTransferEmptyOnStartup = false;
        }

        Name selfName = applicationInfoManager.getInfo().getDataCenterInfo().getName();
        boolean isAws = Name.Amazon == selfName;
        if (isAws && this.serverConfig.shouldPrimeAwsReplicaConnections()) {
            logger.info("Priming AWS connections for all replicas..");
            this.primeAwsReplicas(applicationInfoManager);
        }

        logger.info("Changing status to UP");
        applicationInfoManager.setInstanceStatus(InstanceStatus.UP);
        super.postInit();
    }

　　

 protected void postInit() {
        this.renewsLastMin.start();
        if (this.evictionTaskRef.get() != null) {
            ((AbstractInstanceRegistry.EvictionTask)this.evictionTaskRef.get()).cancel();
        }

        this.evictionTaskRef.set(new AbstractInstanceRegistry.EvictionTask());
        this.evictionTimer.schedule((TimerTask)this.evictionTaskRef.get(), this.serverConfig.getEvictionIntervalTimerInMs(), this.serverConfig.getEvictionIntervalTimerInMs());
    }

　　

2. 客户端注册过程

　　客户端流程

　　

　　1.入口：DiscoveryClient功能描述

　　　　1）  向Eureka Server注册服务实例

　　 　2）向Eureka Server续约

　　 　3）  当服务关闭的时候向Eureka Server取消租约

　　　4）  查询注册到Eureka Server中的服务实例

　　2 实例化，调用构造方法

　　

@Inject
    DiscoveryClient(ApplicationInfoManager applicationInfoManager, EurekaClientConfig config, AbstractDiscoveryClientOptionalArgs args, Provider<BackupRegistry> backupRegistryProvider) {
        this.RECONCILE_HASH_CODES_MISMATCH = Monitors.newCounter("DiscoveryClient_ReconcileHashCodeMismatch");
        this.FETCH_REGISTRY_TIMER = Monitors.newTimer("DiscoveryClient_FetchRegistry");
        this.REREGISTER_COUNTER = Monitors.newCounter("DiscoveryClient_Reregister");
        this.localRegionApps = new AtomicReference();
        this.fetchRegistryUpdateLock = new ReentrantLock();
        this.healthCheckHandlerRef = new AtomicReference();
        this.remoteRegionVsApps = new ConcurrentHashMap();
        this.lastRemoteInstanceStatus = InstanceStatus.UNKNOWN;
        this.eventListeners = new CopyOnWriteArraySet();
        this.registrySize = 0;
        this.lastSuccessfulRegistryFetchTimestamp = -1L;
        this.lastSuccessfulHeartbeatTimestamp = -1L;
        this.isShutdown = new AtomicBoolean(false);
        if (args != null) {
            this.healthCheckHandlerProvider = args.healthCheckHandlerProvider;
            this.healthCheckCallbackProvider = args.healthCheckCallbackProvider;
            this.eventListeners.addAll(args.getEventListeners());
            this.preRegistrationHandler = args.preRegistrationHandler;
        } else {
            this.healthCheckCallbackProvider = null;
            this.healthCheckHandlerProvider = null;
            this.preRegistrationHandler = null;
        }

        this.applicationInfoManager = applicationInfoManager;
        InstanceInfo myInfo = applicationInfoManager.getInfo();
        this.clientConfig = config;
        staticClientConfig = this.clientConfig;
        this.transportConfig = config.getTransportConfig();
        this.instanceInfo = myInfo;
        if (myInfo != null) {
            this.appPathIdentifier = this.instanceInfo.getAppName() + "/" + this.instanceInfo.getId();
        } else {
            logger.warn("Setting instanceInfo to a passed in null value");
        }

        this.backupRegistryProvider = backupRegistryProvider;
        this.urlRandomizer = new InstanceInfoBasedUrlRandomizer(this.instanceInfo);
        this.localRegionApps.set(new Applications());
        this.fetchRegistryGeneration = new AtomicLong(0L);
        this.remoteRegionsToFetch = new AtomicReference(this.clientConfig.fetchRegistryForRemoteRegions());
        this.remoteRegionsRef = new AtomicReference(this.remoteRegionsToFetch.get() == null ? null : ((String)this.remoteRegionsToFetch.get()).split(","));
        if (config.shouldFetchRegistry()) {
            this.registryStalenessMonitor = new ThresholdLevelsMetric(this, "eurekaClient.registry.lastUpdateSec_", new long[]{15L, 30L, 60L, 120L, 240L, 480L});
        } else {
            this.registryStalenessMonitor = ThresholdLevelsMetric.NO_OP_METRIC;
        }

        if (config.shouldRegisterWithEureka()) {
            this.heartbeatStalenessMonitor = new ThresholdLevelsMetric(this, "eurekaClient.registration.lastHeartbeatSec_", new long[]{15L, 30L, 60L, 120L, 240L, 480L});
        } else {
            this.heartbeatStalenessMonitor = ThresholdLevelsMetric.NO_OP_METRIC;
        }

        logger.info("Initializing Eureka in region {}", this.clientConfig.getRegion());
        if (!config.shouldRegisterWithEureka() && !config.shouldFetchRegistry()) {
            logger.info("Client configured to neither register nor query for data.");
            this.scheduler = null;
            this.heartbeatExecutor = null;
            this.cacheRefreshExecutor = null;
            this.eurekaTransport = null;
            this.instanceRegionChecker = new InstanceRegionChecker(new PropertyBasedAzToRegionMapper(config), this.clientConfig.getRegion());
            DiscoveryManager.getInstance().setDiscoveryClient(this);
            DiscoveryManager.getInstance().setEurekaClientConfig(config);
            this.initTimestampMs = System.currentTimeMillis();
            logger.info("Discovery Client initialized at timestamp {} with initial instances count: {}", this.initTimestampMs, this.getApplications().size());
        } else {
            try {
                this.scheduler = Executors.newScheduledThreadPool(2, (new ThreadFactoryBuilder()).setNameFormat("DiscoveryClient-%d").setDaemon(true).build());
                this.heartbeatExecutor = new ThreadPoolExecutor(1, this.clientConfig.getHeartbeatExecutorThreadPoolSize(), 0L, TimeUnit.SECONDS, new SynchronousQueue(), (new ThreadFactoryBuilder()).setNameFormat("DiscoveryClient-HeartbeatExecutor-%d").setDaemon(true).build());
                this.cacheRefreshExecutor = new ThreadPoolExecutor(1, this.clientConfig.getCacheRefreshExecutorThreadPoolSize(), 0L, TimeUnit.SECONDS, new SynchronousQueue(), (new ThreadFactoryBuilder()).setNameFormat("DiscoveryClient-CacheRefreshExecutor-%d").setDaemon(true).build());
                this.eurekaTransport = new DiscoveryClient.EurekaTransport();
                this.scheduleServerEndpointTask(this.eurekaTransport, args);
                Object azToRegionMapper;
                if (this.clientConfig.shouldUseDnsForFetchingServiceUrls()) {
                    azToRegionMapper = new DNSBasedAzToRegionMapper(this.clientConfig);
                } else {
                    azToRegionMapper = new PropertyBasedAzToRegionMapper(this.clientConfig);
                }

                if (null != this.remoteRegionsToFetch.get()) {
                    ((AzToRegionMapper)azToRegionMapper).setRegionsToFetch(((String)this.remoteRegionsToFetch.get()).split(","));
                }

                this.instanceRegionChecker = new InstanceRegionChecker((AzToRegionMapper)azToRegionMapper, this.clientConfig.getRegion());
            } catch (Throwable var9) {
                throw new RuntimeException("Failed to initialize DiscoveryClient!", var9);
            }

            if (this.clientConfig.shouldFetchRegistry() && !this.fetchRegistry(false)) {
                this.fetchRegistryFromBackup();
            }

            if (this.preRegistrationHandler != null) {
                this.preRegistrationHandler.beforeRegistration();
            }

            if (this.clientConfig.shouldRegisterWithEureka() && this.clientConfig.shouldEnforceRegistrationAtInit()) {
                try {
                    if (!this.register()) {
                        throw new IllegalStateException("Registration error at startup. Invalid server response.");
                    }
                } catch (Throwable var8) {
                    logger.error("Registration error at startup: {}", var8.getMessage());
                    throw new IllegalStateException(var8);
                }
            }

            this.initScheduledTasks(); //注册任务主要是在这个定时任务里面实现

            try {
                Monitors.registerObject(this);
            } catch (Throwable var7) {
                logger.warn("Cannot register timers", var7);
            }

            DiscoveryManager.getInstance().setDiscoveryClient(this);
            DiscoveryManager.getInstance().setEurekaClientConfig(config);
            this.initTimestampMs = System.currentTimeMillis();
            logger.info("Discovery Client initialized at timestamp {} with initial instances count: {}", this.initTimestampMs, this.getApplications().size());
        }
    }

　　

 public boolean onDemandUpdate() {
        if (this.rateLimiter.acquire(this.burstSize, (long)this.allowedRatePerMinute)) {
            if (!this.scheduler.isShutdown()) {
                this.scheduler.submit(new Runnable() {
                    public void run() {
                        InstanceInfoReplicator.logger.debug("Executing on-demand update of local InstanceInfo");
                        Future latestPeriodic = (Future)InstanceInfoReplicator.this.scheduledPeriodicRef.get();
                        if (latestPeriodic != null && !latestPeriodic.isDone()) {
                            InstanceInfoReplicator.logger.debug("Canceling the latest scheduled update, it will be rescheduled at the end of on demand update");
                            latestPeriodic.cancel(false);
                        }

                        InstanceInfoReplicator.this.run();
                    }
                });
                return true;
            } else {
                logger.warn("Ignoring onDemand update due to stopped scheduler");
                return false;
            }
        } else {
            logger.warn("Ignoring onDemand update due to rate limiter");
            return false;
        }
    }

    public void run() {
        boolean var6 = false;

        ScheduledFuture next;
        label53: {
            try {
                var6 = true;
                this.discoveryClient.refreshInstanceInfo();
                Long dirtyTimestamp = this.instanceInfo.isDirtyWithTime();
                if (dirtyTimestamp != null) {
                    this.discoveryClient.register();
                    this.instanceInfo.unsetIsDirty(dirtyTimestamp);
                    var6 = false;
                } else {
                    var6 = false;
                }
                break label53;
            } catch (Throwable var7) {
                logger.warn("There was a problem with the instance info replicator", var7);
                var6 = false;
            } finally {
                if (var6) {
                    ScheduledFuture next = this.scheduler.schedule(this, (long)this.replicationIntervalSeconds, TimeUnit.SECONDS);
                    this.scheduledPeriodicRef.set(next);
                }
            }

            next = this.scheduler.schedule(this, (long)this.replicationIntervalSeconds, TimeUnit.SECONDS);
            this.scheduledPeriodicRef.set(next);
            return;
        }

        next = this.scheduler.schedule(this, (long)this.replicationIntervalSeconds, TimeUnit.SECONDS);
        this.scheduledPeriodicRef.set(next);
    }

　　

 boolean register() throws Throwable {
        logger.info("DiscoveryClient_{}: registering service...", this.appPathIdentifier);

        EurekaHttpResponse httpResponse;
        try {
            httpResponse = this.eurekaTransport.registrationClient.register(this.instanceInfo);
        } catch (Exception var3) {
            logger.warn("DiscoveryClient_{} - registration failed {}", new Object[]{this.appPathIdentifier, var3.getMessage(), var3});
            throw var3;
        }

        if (logger.isInfoEnabled()) {
            logger.info("DiscoveryClient_{} - registration status: {}", this.appPathIdentifier, httpResponse.getStatusCode());
        }

        return httpResponse.getStatusCode() == 204;
    }

　最后调用register方法对服务进行注册

3. 服务端接收注册的流程

　　接受注册的流程

　　

　1.入口：ApplicationResource的addInstance()方法

　　

@POST
    @Consumes({"application/json", "application/xml"})
    public Response addInstance(InstanceInfo info, @HeaderParam("x-netflix-discovery-replication") String isReplication) {
        logger.debug("Registering instance {} (replication={})", info.getId(), isReplication);
        if (this.isBlank(info.getId())) {
            return Response.status(400).entity("Missing instanceId").build();
        } else if (this.isBlank(info.getHostName())) {
            return Response.status(400).entity("Missing hostname").build();
        } else if (this.isBlank(info.getIPAddr())) {
            return Response.status(400).entity("Missing ip address").build();
        } else if (this.isBlank(info.getAppName())) {
            return Response.status(400).entity("Missing appName").build();
        } else if (!this.appName.equals(info.getAppName())) {
            return Response.status(400).entity("Mismatched appName, expecting " + this.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();
        } else {
            DataCenterInfo dataCenterInfo = info.getDataCenterInfo();
            if (dataCenterInfo instanceof UniqueIdentifier) {
                String dataCenterInfoId = ((UniqueIdentifier)dataCenterInfo).getId();
                if (this.isBlank(dataCenterInfoId)) {
                    boolean experimental = "true".equalsIgnoreCase(this.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();
                    }

                    if (dataCenterInfo instanceof AmazonInfo) {
                        AmazonInfo amazonInfo = (AmazonInfo)dataCenterInfo;
                        String effectiveId = amazonInfo.get(MetaDataKey.instanceId);
                        if (effectiveId == null) {
                            amazonInfo.getMetadata().put(MetaDataKey.instanceId.getName(), info.getId());
                        }
                    } else {
                        logger.warn("Registering DataCenterInfo of type {} without an appropriate id", dataCenterInfo.getClass());
                    }
                }
            }

            this.registry.register(info, "true".equals(isReplication));
            return Response.status(204).build();
        }
    }

　　register()方法

   public void register(final InstanceInfo info, final boolean isReplication) {
        this.handleRegistration(info, this.resolveInstanceLeaseDuration(info), isReplication);
        super.register(info, isReplication);
    }

·super.register()方法

　　

  public void register(InstanceInfo info, boolean isReplication) {
        int leaseDuration = 90;
        if (info.getLeaseInfo() != null && info.getLeaseInfo().getDurationInSecs() > 0) {
            leaseDuration = info.getLeaseInfo().getDurationInSecs();
        }

        super.register(info, leaseDuration, isReplication);
        this.replicateToPeers(PeerAwareInstanceRegistryImpl.Action.Register, info.getAppName(), info.getId(), info, (InstanceStatus)null, isReplication);
    }

　　说明：

　　1、 调用PeerAwareInstanceRegistryImpl的register方法

　　2、 完成服务注册后，调用replicateToPeers向其它Eureka Server节点（Peer）做状态同步