Eureka server端服务同步与剔除(三)

• 上期

public void contextInitialized(ServletContext context) {
   try {
   //初始化eureka运行环境
      initEurekaEnvironment();
      //初始化eureka上下文
      initEurekaServerContext();
      //这是配置项可以先忽略阅读
      context.setAttribute(EurekaServerContext.class.getName(), this.serverContext);
   }
   catch (Throwable e) {
      log.error("Cannot bootstrap eureka server :", e);
      throw new RuntimeException("Cannot bootstrap eureka server :", e);
   }
}

• 继续

同步相关代码

protected void initEurekaServerContext() throws Exception {
   // For backward compatibility
   // .......去除不相干代码

   log.info("Initialized server context");
    // 服务同步
   // Copy registry from neighboring eureka node
   int registryCount = this.registry.syncUp();
   this.registry.openForTraffic(this.applicationInfoManager, registryCount);

   // Register all monitoring statistics.
   EurekaMonitors.registerAllStats();
}

registry.syncUp() 相关代码

/**
 * Populates the registry information from a peer eureka node. This
 * operation fails over to other nodes until the list is exhausted if the
 * communication fails.
 */
@Override
public int syncUp() {
    // Copy entire entry from neighboring DS node
    int count = 0;

    for (int i = 0; ((i < serverConfig.getRegistrySyncRetries()) && (count == 0)); i++) {
        if (i > 0) {
            try {
                Thread.sleep(serverConfig.getRegistrySyncRetryWaitMs());
            } catch (InterruptedException e) {
                logger.warn("Interrupted during registry transfer..");
                break;
            }
        }
        //获取注册数据
        Applications apps = eurekaClient.getApplications();
        for (Application app : apps.getRegisteredApplications()) {
            for (InstanceInfo instance : app.getInstances()) {
                try {
                //判断是否已经注册过
                    if (isRegisterable(instance)) {
                        register(instance, instance.getLeaseInfo().getDurationInSecs(), true);
                        count++;
                    }
                } catch (Throwable t) {
                    logger.error("During DS init copy", t);
                }
            }
        }
    }
    return count;
}

剔除相关代码

没有明显的找到相关剔除的代码,但是剩余的代码不多,从这里入手
this.registry.openForTraffic(this.applicationInfoManager, registryCount);

这个方法的实现类有两个,用哪个呢,除了debug?

我们可以看到,一开始注入的就是 InstanceRegistry

其中默认剔除的时间是60秒

具体方法

public void evict(long additionalLeaseMs) {
    logger.debug("Running the evict task");

    if (!isLeaseExpirationEnabled()) {
        logger.debug("DS: lease expiration is currently disabled.");
        return;
    }

    // We collect first all expired items, to evict them in random order. For large eviction sets,
    // if we do not that, we might wipe out whole apps before self preservation kicks in. By randomizing it,
    // the impact should be evenly distributed across all applications.
    List<Lease<InstanceInfo>> expiredLeases = new ArrayList<>();
    for (Entry<String, Map<String, Lease<InstanceInfo>>> groupEntry : registry.entrySet()) {
        Map<String, Lease<InstanceInfo>> leaseMap = groupEntry.getValue();
        if (leaseMap != null) {
            for (Entry<String, Lease<InstanceInfo>> leaseEntry : leaseMap.entrySet()) {
                Lease<InstanceInfo> lease = leaseEntry.getValue();
                if (lease.isExpired(additionalLeaseMs) && lease.getHolder() != null) {
                    expiredLeases.add(lease);
                }
            }
        }
    }

    // To compensate for GC pauses or drifting local time, we need to use current registry size as a base for
    // triggering self-preservation. Without that we would wipe out full registry.
    int registrySize = (int) getLocalRegistrySize();
    int registrySizeThreshold = (int) (registrySize * serverConfig.getRenewalPercentThreshold());
    int evictionLimit = registrySize - registrySizeThreshold;

    int toEvict = Math.min(expiredLeases.size(), evictionLimit);
    if (toEvict > 0) {
        logger.info("Evicting {} items (expired={}, evictionLimit={})", toEvict, expiredLeases.size(), evictionLimit);

        Random random = new Random(System.currentTimeMillis());
        for (int i = 0; i < toEvict; i++) {
            // Pick a random item (Knuth shuffle algorithm)
            int next = i + random.nextInt(expiredLeases.size() - i);
            Collections.swap(expiredLeases, i, next);
            Lease<InstanceInfo> lease = expiredLeases.get(i);

            String appName = lease.getHolder().getAppName();
            String id = lease.getHolder().getId();
            EXPIRED.increment();
            logger.warn("DS: Registry: expired lease for {}/{}", appName, id);
            internalCancel(appName, id, false);
        }
    }
}

具体剔除

protected boolean internalCancel(String appName, String id, boolean isReplication) {
    try {
        read.lock();
        CANCEL.increment(isReplication);
        Map<String, Lease<InstanceInfo>> gMap = registry.get(appName);
        Lease<InstanceInfo> leaseToCancel = null;
        if (gMap != null) {
            leaseToCancel = gMap.remove(id);
        }
        synchronized (recentCanceledQueue) {
            recentCanceledQueue.add(new Pair<Long, String>(System.currentTimeMillis(), appName + "(" + id + ")"));
        }
        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();
    }
}

• 下期预告 Eureka client 源码解析