深入 Eureka 服务注册 源码分析(二)

Eureka-Client注册服务

啥时候会注册

在两种情况下客户端会主动向服务端发送自己的注册信息

1.当客户端的instance信息发生改变时,Eureka-Client和Server端信息不一致时

2.当客户端刚刚启动的时候。

定时器注册

com.netflix.discovery.DiscoveryClient ,使用的@Inject //google guice 注入遵循 JSR-330规范

private void initScheduledTasks() {
    //省略, 刷新缓存的定时器
    if (clientConfig.shouldRegisterWithEureka()) {
       //省略, 发送心跳的定时器
        // 监听instance的状态变更
        statusChangeListener = new ApplicationInfoManager.StatusChangeListener() {
            @Override
            public String getId() {
                return "statusChangeListener";
            }
    
            @Override
            public void notify(StatusChangeEvent statusChangeEvent) {
                if (InstanceStatus.DOWN == statusChangeEvent.getStatus() ||
                        InstanceStatus.DOWN == statusChangeEvent.getPreviousStatus()) {
                    logger.warn("Saw local status change event {}", statusChangeEvent);
                } else {
                    logger.info("Saw local status change event {}", statusChangeEvent);
                }
                instanceInfoReplicator.onDemandUpdate();
            }
        };
        // 注册监听
        if (clientConfig.shouldOnDemandUpdateStatusChange()) {
            applicationInfoManager.registerStatusChangeListener(statusChangeListener);
        }
        // 开启实例信息复制器
        instanceInfoReplicator.start(clientConfig.getInitialInstanceInfoReplicationIntervalSeconds());
    } else {
        logger.info("Not registering with Eureka server per configuration");
    }
}

initScheduledTasks() 方法是在DiscoverClient的构造函数初始化的时候被调用。

主要作用就是:

1.开启缓刷新定时器

2.开启发送心跳的定时器

3.开启实例instance状态变更监听

4.开启应用状态复制器(主要就是为了开启一个定时线程,每40秒判断实例信息是否变更,如果变更了则重新注册)

//InstanceInfoReplicator.java
class InstanceInfoReplicator implements Runnable {

    public void start(int initialDelayMs) {
        if (started.compareAndSet(false, true)) {
            // 首次进来设置一下。
            instanceInfo.setIsDirty();  // for initial register
            // 开启定时线程 , 每停顿initialDelayMs秒执行一次该任务。 服务注册也是由这个任务完成
            Future next = scheduler.schedule(this, initialDelayMs, TimeUnit.SECONDS);
            scheduledPeriodicRef.set(next);
        }
    }
    // show down
    public void stop() {
        scheduler.shutdownNow();
        started.set(false);
    }
    // 这个方法主要是在上面提到的监听器里面被调用。
    public boolean onDemandUpdate() {
        if (rateLimiter.acquire(burstSize, allowedRatePerMinute)) {
            scheduler.submit(new Runnable() {
                @Override
                public void run() {
                    logger.debug("Executing on-demand update of local InstanceInfo");
                    // 这个地方用来获取定时线程的执行Future,如果该线程还没有执行完毕,则取消掉,释放资源,因为下面也会执行run方法
                    Future latestPeriodic = scheduledPeriodicRef.get();
                    if (latestPeriodic != null && !latestPeriodic.isDone()) {
                        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 rate limiter");
            return false;
        }
    }
    
    public void run() {
        try {
            // 刷新实例信息。
            discoveryClient.refreshInstanceInfo();
            // 判断实例信息是否不一致
            Long dirtyTimestamp = instanceInfo.isDirtyWithTime();
            if (dirtyTimestamp != null) {
                // 注册自己的服务
                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);
        }
    }

从上面可以看到InstanceInfoReplicator是一个负责服务注册的线程任务, 有两个地方可以执行这个任务

1.定时线程,每40秒执行一次。

2.当instance的状态发生变更(除去DOWN这个状态)的时候,会有statusChangeListener 这个监听器监听到

去执行服务注册。

PS: 现在网上有些文章,说服务启动后,要隔40秒才会去注册自己的服务,这个说法是错误的。 当应用刚刚启动的时候,注册服务不是依赖那个定时线程去跑的,而是在EurekaAutoServiceRegistration这个类里面

自动注册

在EurekaClientAutoConfiguration这个自动配置类里面,有下面这一段代码

@Bean
@ConditionalOnBean(AutoServiceRegistrationProperties.class)
@ConditionalOnProperty(value = "spring.cloud.service-registry.auto-registration.enabled", matchIfMissing = true)
public EurekaAutoServiceRegistration eurekaAutoServiceRegistration(ApplicationContext context, EurekaServiceRegistry registry, EurekaRegistration registration) {
   return new EurekaAutoServiceRegistration(context, registry, registration);
}

上面这段代码,很简单,就是实例化了一个Bean,主要是这个Bean实现了SmartLifecycle, 有这个接口标识的在spring 容器加载完所有的Bean之后会执行该类的start方法, 下面可以详细看看这个代码。

//EurekaAutoServiceRegistration.java
public class EurekaAutoServiceRegistration implements AutoServiceRegistration, SmartLifecycle, Ordered {

   private static final Log log = LogFactory.getLog(EurekaAutoServiceRegistration.class);

   private AtomicBoolean running = new AtomicBoolean(false);

   private int order = 0;

   private AtomicInteger port = new AtomicInteger(0);

   private ApplicationContext context;

   private EurekaServiceRegistry serviceRegistry;

   private EurekaRegistration registration;

   public EurekaAutoServiceRegistration(ApplicationContext context, EurekaServiceRegistry serviceRegistry, EurekaRegistration registration) {
      this.context = context;
      this.serviceRegistry = serviceRegistry;
      this.registration = registration;
   }

   @Override
   public void start() {
      // 端口配置
      if (this.port.get() != 0 && this.registration.getNonSecurePort() == 0) {
         this.registration.setNonSecurePort(this.port.get());
      }
    
      // 没有在运行
      if (!this.running.get() && this.registration.getNonSecurePort() > 0) {
         // 重点就这这里,这里是主动去注册。
         this.serviceRegistry.register(this.registration);
        // 发布 节点注册事件
         this.context.publishEvent(
               new InstanceRegisteredEvent<>(this, this.registration.getInstanceConfig()));
         this.running.set(true);
      }
   }
// EurekaServiceRegistry.java
@Override
public void register(EurekaRegistration reg) {
   maybeInitializeClient(reg);

   if (log.isInfoEnabled()) {
      log.info("Registering application " + reg.getInstanceConfig().getAppname()
            + " with eureka with status "
            + reg.getInstanceConfig().getInitialStatus());
   }
   // 设置当前实例的instanceStatus, 一旦这个实例的状态发生改变,
   // 只要状态不是DOWN,那么就会被监听器监听到,最终执行服务注册
   reg.getApplicationInfoManager()
         .setInstanceStatus(reg.getInstanceConfig().getInitialStatus());
    // 健康检查器不为空
   if (reg.getHealthCheckHandler() != null) {
      // 设置进去
      reg.getEurekaClient().registerHealthCheck(reg.getHealthCheckHandler());
   }
}

总结: 服务注册分为两种,

第一种: 当应用启动的时候,如果应用开启了自动注册(默认开启), 那么在自动配置类加载的时候,会通过EurekaAutoServiceRegistration实例化的时候,去改变instance的status, 最终被监听器监听到,执行服务注册的代码

第二种: 主要应用于启动之后,当应用的信息发生改变之后,每40每秒执行一次的线程,检测到了,也会自动去注册一次。

DiscoveryClient.register()

//DiscoveryClient.java
boolean register() throws Throwable {
    logger.info(PREFIX + appPathIdentifier + ": registering service...");
    EurekaHttpResponse httpResponse;
    try {
        // 发起HTTP请求
        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;
}

使用的Jersey框架来完成http的请求调用

//AbstractJerseyEurekaHttpClient.java
public EurekaHttpResponse register(InstanceInfo info) {
    String urlPath = "apps/" + info.getAppName();
    ClientResponse response = null;
    try {
        Builder resourceBuilder = jerseyClient.resource(serviceUrl).path(urlPath).getRequestBuilder();
        addExtraHeaders(resourceBuilder);
        response = resourceBuilder
                .header("Accept-Encoding", "gzip")
                .type(MediaType.APPLICATION_JSON_TYPE)
                .accept(MediaType.APPLICATION_JSON)
                .post(ClientResponse.class, info);
        return anEurekaHttpResponse(response.getStatus()).headers(headersOf(response)).build();
    } finally {
        if (logger.isDebugEnabled()) {
            logger.debug("Jersey HTTP POST {}/{} with instance {}; statusCode={}", serviceUrl, urlPath, info.getId(),
                    response == null ? "N/A" : response.getStatus());
        }
        if (response != null) {
            response.close();
        }
    }
}

POST 请求 Eureka-Server 的 apps/${APP_NAME} 接口,参数为 InstanceInfo ,实现注册实例信息的注册。

Eureka-Server接收注册

ApplicationResource

接下来可以看一下,服务端是接收到请求之后是如何处理的。

程序入口: com.netflix.eureka.resources.ApplicationResource.addInstance()

//ApplicationResource.java
@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
    // 参数校验,不符合验证规则的,返回400状态码,此处不做详解
    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());
            }
        }
    }
    // 重点在这里
    registry.register(info, "true".equals(isReplication));
    return Response.status(204).build();  // 204 to be backwards compatible
}

PeerAwareInstanceRegistryImpl

上面的register方法,最终调用的是PeerAwareInstanceRegistryImpl的方法

@Override
public void register(final InstanceInfo info, final boolean isReplication) {
    // 租约的过期时间,默认90秒,也就是说当服务端超过90秒没有收到客户端的心跳,则主动剔除该节点。
    int leaseDuration = Lease.DEFAULT_DURATION_IN_SECS;
    if (info.getLeaseInfo() != null && info.getLeaseInfo().getDurationInSecs() > 0) {
        // 如果客户端自定义了,那么以客户端为准
        leaseDuration = info.getLeaseInfo().getDurationInSecs();
    }
    // 节点注册
    super.register(info, leaseDuration, isReplication);
    // 复制到同等服务节点上去
    replicateToPeers(Action.Register, info.getAppName(), info.getId(), info, null, isReplication);
}

由上面可以知道,调用的是父类的register方法, 其父类是AbstractInstanceRegistry ,在了解具体的注册方法之前,

需要先了解一下Lease这个对象,因为Eureka-Server最终处理注册信息的时候,都会转化为这个对象来处理。

Lease

public class Lease {

    enum Action {
        Register, Cancel, Renew
    };
    
    public static final int DEFAULT_DURATION_IN_SECS = 90;
    
    private T holder;
    private long evictionTimestamp;
    private long registrationTimestamp;
    private long serviceUpTimestamp;
    
    private volatile long lastUpdateTimestamp;
    private long duration;
    
    public Lease(T r, int durationInSecs) {
        holder = r;
        registrationTimestamp = System.currentTimeMillis();
        lastUpdateTimestamp = registrationTimestamp;
        //durationInSecs为秒单位, 换算成毫秒
        duration = (durationInSecs * 1000);
    
    }
    
    // 客户端续约时,更新最后的更新时间 , 用当前系统加上过期的时间
    public void renew() {
        lastUpdateTimestamp = System.currentTimeMillis() + duration;
    
    }

   // 服务下线时,更新服务下线时间
    public void cancel() {
        if (evictionTimestamp <= 0) {
            evictionTimestamp = System.currentTimeMillis();
        }
    }


    public void serviceUp() {
        if (serviceUpTimestamp == 0) {
            serviceUpTimestamp = System.currentTimeMillis();
        }
    }


    public void setServiceUpTimestamp(long serviceUpTimestamp) {
        this.serviceUpTimestamp = serviceUpTimestamp;
    }


    public boolean isExpired() {
        return isExpired(0l);
    }


    public boolean isExpired(long additionalLeaseMs) {
        return (evictionTimestamp > 0 || System.currentTimeMillis() > (lastUpdateTimestamp + duration + additionalLeaseMs));
    }
}

DEFAULT_DURATION_IN_SECS : 租约过期的时间常量,默认未90秒,也就说90秒没有心跳过来,那么这边将会自动剔除该节点holder :这个租约是属于谁的, 目前占用这个属性的是 instanceInfo,也就是客户端实例信息。evictionTimestamp : 租约是啥时候过期的,当服务下线的时候,会过来更新这个时间戳registrationTimestamp : 租约的注册时间
serviceUpTimestamp :服务启动时间 ,当客户端在注册的时候,instanceInfo的status 为UP的时候,则更新这个时间戳

public void serviceUp() {
        if (serviceUpTimestamp == 0) {
            serviceUpTimestamp = System.currentTimeMillis();
        }
}

lastUpdateTimestamp :最后更新时间,每次续约的时候,都会更新这个时间戳,在判断实例

是否过期时,需要用到这个属性。

duration:过期时间,毫秒单位

AbstractInstanceRegistry

public void register(InstanceInfo registrant, int leaseDuration, boolean isReplication) {
    try {
        // 上只读锁
        read.lock();
        // 从本地MAP里面获取当前实例的信息。
        Map> gMap = registry.get(registrant.getAppName());
        // 增加注册次数到监控信息里面去。
        REGISTER.increment(isReplication);
        if (gMap == null) {
            // 如果第一次进来,那么gMap为空,则创建一个ConcurrentHashMap放入到registry里面去
            final ConcurrentHashMap> gNewMap = new ConcurrentHashMap>();
            // putIfAbsent方法主要是在向ConcurrentHashMap中添加键—值对的时候,它会先判断该键值对是否已经存在。
            // 如果不存在(新的entry),那么会向map中添加该键值对,并返回null。
            // 如果已经存在,那么不会覆盖已有的值,直接返回已经存在的值。
            gMap = registry.putIfAbsent(registrant.getAppName(), gNewMap);
            if (gMap == null) {
                // 表明map中确实不存在,则设置gMap为最新创建的那个
                gMap = gNewMap;
            }
        }
        // 从MAP中查询已经存在的Lease信息 (比如第二次来)
        Lease existingLease = gMap.get(registrant.getId());
        // 当Lease的对象不为空时。
        if (existingLease != null && (existingLease.getHolder() != null)) {
            // 当instance已经存在是,和客户端的instance的信息做比较,时间最新的那个,为有效instance信息
            Long existingLastDirtyTimestamp = existingLease.getHolder().getLastDirtyTimestamp(); // server
            Long registrationLastDirtyTimestamp = registrant.getLastDirtyTimestamp();   // client
            logger.debug("Existing lease found (existing={}, provided={}", existingLastDirtyTimestamp, registrationLastDirtyTimestamp);
            if (existingLastDirtyTimestamp > registrationLastDirtyTimestamp) {
                logger.warn("There is an existing lease and the existing lease's dirty timestamp {} is greater" +
                        " than the one that is being registered {}", existingLastDirtyTimestamp, registrationLastDirtyTimestamp);
                logger.warn("Using the existing instanceInfo instead of the new instanceInfo as the registrant");
                registrant = existingLease.getHolder();
            }
        } else {
            // 这里只有当existinglease不存在时,才会进来。 像那种恢复心跳,信息过期的,都不会进入这里。
            //  Eureka-Server的自我保护机制做的操作,为每分钟最大续约数+2 ,同时重新计算每分钟最小续约数
            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");
        }
        // 构建一个最新的Lease信息
        Lease lease = new Lease(registrant, leaseDuration);
        if (existingLease != null) {
            // 当原来存在Lease的信息时,设置他的serviceUpTimestamp, 保证服务开启的时间一直是第一次的那个
            lease.setServiceUpTimestamp(existingLease.getServiceUpTimestamp());
        }
        // 放入本地Map中
        gMap.put(registrant.getId(), lease);
        // 添加到最近的注册队列里面去,以时间戳作为Key, 名称作为value,主要是为了运维界面的统计数据。
        synchronized (recentRegisteredQueue) {
            recentRegisteredQueue.add(new Pair(
                    System.currentTimeMillis(),
                    registrant.getAppName() + "(" + registrant.getId() + ")"));
        }
        // This is where the initial state transfer of overridden status happens
        // 分析instanceStatus
        if (!InstanceStatus.UNKNOWN.equals(registrant.getOverriddenStatus())) {
            logger.debug("Found overridden status {} for instance {}. Checking to see if needs to be add to the "
                            + "overrides", registrant.getOverriddenStatus(), registrant.getId());
            if (!overriddenInstanceStatusMap.containsKey(registrant.getId())) {
                logger.info("Not found overridden id {} and hence adding it", registrant.getId());
                overriddenInstanceStatusMap.put(registrant.getId(), registrant.getOverriddenStatus());
            }
        }
        InstanceStatus overriddenStatusFromMap = overriddenInstanceStatusMap.get(registrant.getId());
        if (overriddenStatusFromMap != null) {
            logger.info("Storing overridden status {} from map", overriddenStatusFromMap);
            registrant.setOverriddenStatus(overriddenStatusFromMap);
        }
    
        // Set the status based on the overridden status rules
        InstanceStatus overriddenInstanceStatus = getOverriddenInstanceStatus(registrant, existingLease, isReplication);
        registrant.setStatusWithoutDirty(overriddenInstanceStatus);
    
        // If the lease is registered with UP status, set lease service up timestamp
        // 得到instanceStatus,判断是否是UP状态,
        if (InstanceStatus.UP.equals(registrant.getStatus())) {
            lease.serviceUp();
        }
        // 设置注册类型为添加
        registrant.setActionType(ActionType.ADDED);
        // 租约变更记录队列,记录了实例的每次变化, 用于注册信息的增量获取、
        recentlyChangedQueue.add(new RecentlyChangedItem(lease));
        registrant.setLastUpdatedTimestamp();
        // 清理缓存 ,传入的参数为key
        invalidateCache(registrant.getAppName(), registrant.getVIPAddress(), registrant.getSecureVipAddress());
        logger.info("Registered instance {}/{} with status {} (replication={})",
                registrant.getAppName(), registrant.getId(), registrant.getStatus(), isReplication);
    } finally {
        read.unlock();
    }
}

你可能感兴趣的:(深入 Eureka 服务注册 源码分析(二))