Nacos源码分析03-服务端健康检查

文章目录

Nacos源码分析03-服务端健康检查
- 1. Nacos健康检查
- - 1.1. 1.x版本
  - 1.2. 2.x版本
  - 1.3. 《Nacos架构&原理》摘抄
- 2. ConnectionManager

Nacos源码分析03-服务端健康检查

本系列博客，采用官方源码版本为2.0.3

1. Nacos健康检查 1.1. 1.x版本

在Nacos 1.x版本中，临时实例需要客户端（服务提供者）定时向Nacos发送心跳包来维持自己的健康状态。持久化实例并不基于客户端发送心跳包，而是服务端定时探测客户端进行健康检查（TCP端口探测、HTTP返回码探测）。

1.2. 2.x版本

在Nacos 2.0版本之后持久化实例的监控检查并没有改变逻辑；但临时实例不再使用心跳包，而是通过判断gRPC长连接是否存活来判断临时实例是否健康。

1.3. 《Nacos架构&原理》摘抄

感觉此书实际攥写时间在2.0发行版本之前，部分Nacos实现细节与实际不符。

Zookeeper 和 Eureka 都实现了⼀种 TTL 的机制，就是如果客户端在⼀定时间内没有向注册中心发
送心跳，则会将这个客户端摘除。 Eureka 做的更好的⼀点在于它允许在注册服务的时候，自定义检
查自身状态的健康检查方法。这在服务实例能够保持心跳上报的场景下，是⼀种比较好的体验，在
Dubbo 和 SpringCloud 这两大体系内，也被培养成用户心智上的默认行为。 Nacos 也支持这种
TTL 机制，不过这与 ConfigServer 在阿里巴巴内部的机制又有⼀些区别。 Nacos 目前支持临时实
例使用心跳上报方式维持活性，发送心跳的周期默认是 5 秒， Nacos 服务端会在 15 秒没收到心
跳后将实例设置为不健康，在 30 秒没收到心跳时将这个临时实例摘除。

2. ConnectionManager

ConnectionManager类负责管理所有客户端的长连接。

健康检查策略：每3s检测所有超过20s没发生过通讯的客户端，向客户端发起ClientDetectionRequest探测请求，如果客户端在1s内成功响应，则检测通过，否则执行unregister方法移除Connection。

如果客户端持续与服务端通讯，服务端是不需要主动探活的。
每3秒执行是源自时设置定时任务时，初始化延迟1秒和间隔3秒的策略。
超过20s没发生过通讯，这个20秒配置在ConnectionManager.KEEP_ALIVE_TIME。

Map connections = new ConcurrentHashMap();

@PostConstruct
public void start() {

    // 启动不健康连接排除功能.
    RpcScheduledExecutor.COMMON_SERVER_EXECUTOR.scheduleWithFixedDelay(new Runnable() {
        @Override
        public void run() {
            try {

                int totalCount = connections.size();
                Loggers.REMOTE_DIGEST.info("Connection check task start");
                MetricsMonitor.getLongConnectionMonitor().set(totalCount);
                //统计过时（20s）连接
                Set> entries = connections.entrySet();
                int currentSdkClientCount = currentSdkClientCount();
                boolean isLoaderClient = loadClient >= 0;
                int currentMaxClient = isLoaderClient ? loadClient : connectionLimitRule.countLimit;
                int expelCount = currentMaxClient < 0 ? 0 : Math.max(currentSdkClientCount - currentMaxClient, 0);

                Loggers.REMOTE_DIGEST
                    .info("Total count ={}, sdkCount={},clusterCount={}, currentLimit={}, toExpelCount={}",
                          totalCount, currentSdkClientCount, (totalCount - currentSdkClientCount),
                          currentMaxClient + (isLoaderClient ? "(loaderCount)" : ""), expelCount);

                List expelClient = new linkedList<>();

                Map expelForIp = new HashMap<>(16);

                //1. calculate expel count  of ip.
                for (Map.Entry entry : entries) {

                    Connection client = entry.getValue();
                    String appName = client.getmetaInfo().getAppName();
                    String clientIp = client.getmetaInfo().getClientIp();
                    if (client.getmetaInfo().isSdkSource() && !expelForIp.containsKey(clientIp)) {
                        //get limit for current ip.
                        int countLimitOfIp = connectionLimitRule.getCountLimitOfIp(clientIp);
                        if (countLimitOfIp < 0) {
                            int countLimitOfApp = connectionLimitRule.getCountLimitOfApp(appName);
                            countLimitOfIp = countLimitOfApp < 0 ? countLimitOfIp : countLimitOfApp;
                        }
                        if (countLimitOfIp < 0) {
                            countLimitOfIp = connectionLimitRule.getCountLimitPerClientIpDefault();
                        }

                        if (countLimitOfIp >= 0 && connectionForClientIp.containsKey(clientIp)) {
                            AtomicInteger currentCountIp = connectionForClientIp.get(clientIp);
                            if (currentCountIp != null && currentCountIp.get() > countLimitOfIp) {
                                expelForIp.put(clientIp, new AtomicInteger(currentCountIp.get() - countLimitOfIp));
                            }
                        }
                    }
                }

                Loggers.REMOTE_DIGEST
                    .info("Check over limit for ip limit rule, over limit ip count={}", expelForIp.size());

                if (expelForIp.size() > 0) {
                    Loggers.REMOTE_DIGEST.info("Over limit ip expel info, {}", expelForIp);
                }

                Set outDatedConnections = new HashSet<>();
                long now = System.currentTimeMillis();
                //2.get expel connection for ip limit.
                for (Map.Entry entry : entries) {
                    Connection client = entry.getValue();
                    String clientIp = client.getmetaInfo().getClientIp();
                    AtomicInteger integer = expelForIp.get(clientIp);
                    if (integer != null && integer.intValue() > 0) {
                        integer.decrementAndGet();
                        expelClient.add(client.getmetaInfo().getConnectionId());
                        expelCount--;
                    } else if (now - client.getmetaInfo().getLastActiveTime() >= KEEP_ALIVE_TIME) {
                        outDatedConnections.add(client.getmetaInfo().getConnectionId());
                    }

                }

                //3. if total count is still over limit.
                if (expelCount > 0) {
                    for (Map.Entry entry : entries) {
                        Connection client = entry.getValue();
                        if (!expelForIp.containsKey(client.getmetaInfo().clientIp) && client.getmetaInfo()
                            .isSdkSource() && expelCount > 0) {
                            expelClient.add(client.getmetaInfo().getConnectionId());
                            expelCount--;
                            outDatedConnections.remove(client.getmetaInfo().getConnectionId());
                        }
                    }
                }

                String serverIp = null;
                String serverPort = null;
                if (StringUtils.isNotBlank(redirectAddress) && redirectAddress.contains(Constants.colon)) {
                    String[] split = redirectAddress.split(Constants.colon);
                    serverIp = split[0];
                    serverPort = split[1];
                }

                for (String expelledClientId : expelClient) {
                    try {
                        Connection connection = getConnection(expelledClientId);
                        if (connection != null) {
                            ConnectResetRequest connectResetRequest = new ConnectResetRequest();
                            connectResetRequest.setServerIp(serverIp);
                            connectResetRequest.setServerPort(serverPort);
                            connection.asyncRequest(connectResetRequest, null);
                            Loggers.REMOTE_DIGEST
                                .info("Send connection reset request , connection id = {},recommendServerIp={}, recommendServerPort={}",
                                      expelledClientId, connectResetRequest.getServerIp(),
                                      connectResetRequest.getServerPort());
                        }

                    } catch (ConnectionAlreadyClosedException e) {
                        unregister(expelledClientId);
                    } catch (Exception e) {
                        Loggers.REMOTE_DIGEST.error("Error occurs when expel connection, expelledClientId:{}", expelledClientId, e);
                    }
                }

                //4.client active detection.
                Loggers.REMOTE_DIGEST.info("Out dated connection ,size={}", outDatedConnections.size());
                //异步请求所有需要检测的连接
                if (CollectionUtils.isNotEmpty(outDatedConnections)) {
                    Set successConnections = new HashSet<>();
                    final CountDownLatch latch = new CountDownLatch(outDatedConnections.size());
                    for (String outDateConnectionId : outDatedConnections) {
                        try {
                            Connection connection = getConnection(outDateConnectionId);
                            if (connection != null) {
                                ClientDetectionRequest clientDetectionRequest = new ClientDetectionRequest();
                                connection.asyncRequest(clientDetectionRequest, new RequestCallBack() {
                                    @Override
                                    public Executor getExecutor() {
                                        return null;
                                    }

                                    @Override
                                    public long getTimeout() {
                                        return 1000L;
                                    }

                                    @Override
                                    public void onResponse(Response response) {
                                        latch.countDown();
                                        if (response != null && response.isSuccess()) {
                                            connection.freshActiveTime();
                                            successConnections.add(outDateConnectionId);
                                        }
                                    }

                                    @Override
                                    public void onException(Throwable e) {
                                        latch.countDown();
                                    }
                                });

                                Loggers.REMOTE_DIGEST
                                    .info("[{}]send connection active request ", outDateConnectionId);
                            } else {
                                latch.countDown();
                            }

                        } catch (ConnectionAlreadyClosedException e) {
                            latch.countDown();
                        } catch (Exception e) {
                            Loggers.REMOTE_DIGEST
                                .error("[{}]Error occurs when check client active detection ,error={}",
                                       outDateConnectionId, e);
                            latch.countDown();
                        }
                    }

                    latch.await(3000L, TimeUnit.MILLISECONDS);
                    Loggers.REMOTE_DIGEST
                        .info("Out dated connection check successCount={}", successConnections.size());
					// 对于没有成功响应的客户端，执行unregister移出
                    for (String outDateConnectionId : outDatedConnections) {
                        if (!successConnections.contains(outDateConnectionId)) {
                            Loggers.REMOTE_DIGEST
                                .info("[{}]Unregister Out dated connection....", outDateConnectionId);
                            unregister(outDateConnectionId);
                        }
                    }
                }

                //reset loader client

                if (isLoaderClient) {
                    loadClient = -1;
                    redirectAddress = null;
                }

                Loggers.REMOTE_DIGEST.info("Connection check task end");

            } catch (Throwable e) {
                Loggers.REMOTE.error("Error occurs during connection check... ", e);
            }
        }
    }, 1000L, 3000L, TimeUnit.MILLISECONDS);

}

//注销连接方法
public synchronized void unregister(String connectionId) {
    Connection remove = this.connections.remove(connectionId);
    if (remove != null) {
        String clientIp = remove.getmetaInfo().clientIp;
        AtomicInteger atomicInteger = connectionForClientIp.get(clientIp);
        if (atomicInteger != null) {
            int count = atomicInteger.decrementAndGet();
            if (count <= 0) {
                connectionForClientIp.remove(clientIp);
            }
        }
        remove.close();
        Loggers.REMOTE_DIGEST.info("[{}]Connection unregistered successfully. ", connectionId);
        clientConnectionEventListenerRegistry.notifyClientDisConnected(remove);
    }
}

移除connection后，继承ClientConnectionEventListener的ConnectionbasedClientManager会移除Client，发布ClientDisconnectEvent事件。

@Override
public boolean clientDisconnected(String clientId) {
    Loggers.SRV_LOG.info("Client connection {} disconnect, remove instances and subscribers", clientId);
    ConnectionbasedClient client = clients.remove(clientId);
    if (null == client) {
        return true;
    }
    client.release();
    NotifyCenter.publishEvent(new ClientEvent.ClientDisconnectEvent(client));
    return true;
}

ClientDisconnectEvent会触发几个事件：

Distro协议：同步移除的client数据
清除两个索引缓存：ClientServiceIndexesManager中Service与发布Client的关系；ServiceStorage中Service与Instance的关系
服务订阅：ClientDisconnectEvent会间接触发ServiceChangedEvent事件，将服务变更通知客户端。

Nacos源码分析03-服务端健康检查

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