Nacos2# 服务注册与发现客户端示例与源码解析（二）
引言
引言
上一篇客户端初始化没有撸完，这篇继续。Nacos从2.0以后增加了对grpc的支持，代码中HTTP的代理初始化还有保留，我们注册发现通常为临时节点，这部分已由gRPC接管。可以对比下新旧逻辑的实现差异。
一、内容提要
HTTP代理初始化
HTTP心跳检测器
- HTTP心跳检测只适用于注册的节点持久节点，临时节点会使用grpc代理（HTTP的心跳检测默认废弃由grpc替代）
- 在初始化时客户端注册代理NamingClientProxy时，初始化了一个HTTP心跳器用于向Nacos Server发起心跳
- 在注册节点时通过向心跳执行器添加心跳任务addBeatInfo触发
- 心跳执行器通过每隔五秒中向Nacos Server发起HTTP请求
- 如果返回的server not found会向Nacos Server发起注册请求重新注册
UDP接受服务端推送
- Client通过UDP接受到nacos server推动的消息
- 如果服务端推送的为服务信息通过processServiceInfo处理逻辑见上篇，主要实例变更时的通知机制
- 如果dump类型，则客户端发送服务信息serviceInfoMap的ack信息到服务端
gRPC代理初始化
gRPC初始化逻辑概览
- gRPC 客户端代理的初始化主要逻辑为创建gRPC Client并启动
- 并注册ServerRequestHandler用于处理Nacos Server推送的NotifySubscriberRequest请求
- 注册ConnectionListener用于处理gRPC建立和断开连接事件
- 请求超时时间可以通过「namingRequestTimeout」设置，默认为3秒
gRPC Client启动逻辑
- gRPC Client启动逻辑主要在于建立与nacos server的grpc连接，其中两个守护线程一直在运行
- 守护线程1用于处理grpc连接的建立和关闭事件
- 守护线程2用于与nacos server的心跳保鲜，并负责异步建立grpc连接
- 守护线程2同时负责当nacos server的地址信息发生变更时重新与新server建立连接
- nacos server的地址变更通过grpc通道由server推送ConnectResetRequest到client
- grpc client只与nacos server集群中一台建立grpc连接
二、源码分析
public NamingClientProxyDelegate(String namespace, ServiceInfoHolder serviceInfoHolder, Properties properties,
InstancesChangeNotifier changeNotifier) throws NacosException {
this.serviceInfoUpdateService = new ServiceInfoUpdateService(properties, serviceInfoHolder, this,
changeNotifier);
this.serverListManager = new ServerListManager(properties);
this.serviceInfoHolder = serviceInfoHolder;
this.securityProxy = new SecurityProxy(properties, NamingHttpClientManager.getInstance().getNacosRestTemplate());
initSecurityProxy();
// @注解7.4
this.httpClientProxy = new NamingHttpClientProxy(namespace, securityProxy, serverListManager, properties,serviceInfoHolder);
// @注解7.5
this.grpcClientProxy = new NamingGrpcClientProxy(namespace, securityProxy, serverListManager, properties,serviceInfoHolder);
}
三、HTTP代理初始化
@注解7.4 Http代理的初始化，该代理主要在nacos 2.0以前版本使用，2.0之后通过grpc与nacos server通信。
public NamingHttpClientProxy(String namespaceId, SecurityProxy securityProxy, ServerListManager serverListManager,
Properties properties, ServiceInfoHolder serviceInfoHolder) {
super(securityProxy, properties);
this.serverListManager = serverListManager;
this.setServerPort(DEFAULT_SERVER_PORT);
this.namespaceId = namespaceId;
// @注解7.4.1
this.beatReactor = new BeatReactor(this, properties);
// @注解7.4.2
this.pushReceiver = new PushReceiver(serviceInfoHolder);
// @注解7.4.3
this.maxRetry = ConvertUtils.toInt(properties.getProperty(PropertyKeyConst.NAMING_REQUEST_DOMAIN_RETRY_COUNT,
String.valueOf(UtilAndComs.REQUEST_DOMAIN_RETRY_COUNT)));
}
HTTP心跳检测器
@注解7.4.1 初始化BeatReactor，用于向nacos server发送心跳
public BeatReactor(NamingHttpClientProxy serverProxy, Properties properties) {
this.serverProxy = serverProxy;
// 心跳线程池大小，默认为核数的二分之一，最小为1，可通过properties参数「namingClientBeatThreadCount」设置
int threadCount = initClientBeatThreadCount(properties);
// 初始化线程执行器
this.executorService = new ScheduledThreadPoolExecutor(threadCount, new ThreadFactory() {
@Override
public Thread newThread(Runnable r) {
Thread thread = new Thread(r);
thread.setDaemon(true);
thread.setName("com.alibaba.nacos.naming.beat.sender");
return thread;
}
});
}
接着一下这个执行器再做什么事情。
public void addBeatInfo(String serviceName, BeatInfo beatInfo) {
NAMING_LOGGER.info("[BEAT] adding beat: {} to beat map.", beatInfo);
String key = buildKey(serviceName, beatInfo.getIp(), beatInfo.getPort());
BeatInfo existBeat = null;
//fix #1733
if ((existBeat = dom2Beat.remove(key)) != null) {
existBeat.setStopped(true);
}
dom2Beat.put(key, beatInfo);
// 默认延迟5秒
executorService.schedule(new BeatTask(beatInfo), beatInfo.getPeriod(), TimeUnit.MILLISECONDS);
MetricsMonitor.getDom2BeatSizeMonitor().set(dom2Beat.size());
}
当通过addBeatInfo增加一个心跳信息BeatInfo时，执行器会创建BeatTask（Runnable）延迟5秒运行。
class BeatTask implements Runnable {
BeatInfo beatInfo;
public BeatTask(BeatInfo beatInfo) {
this.beatInfo = beatInfo;
}
@Override
public void run() {
if (beatInfo.isStopped()) {
return;
}
long nextTime = beatInfo.getPeriod();
try {
// 向nacos server「/nacos/v1/ns/instance/beat」发送心跳
JsonNode result = serverProxy.sendBeat(beatInfo, BeatReactor.this.lightBeatEnabled);
long interval = result.get("clientBeatInterval").asLong();
boolean lightBeatEnabled = false;
if (result.has(CommonParams.LIGHT_BEAT_ENABLED)) {
lightBeatEnabled = result.get(CommonParams.LIGHT_BEAT_ENABLED).asBoolean();
}
BeatReactor.this.lightBeatEnabled = lightBeatEnabled;
if (interval > 0) {
nextTime = interval;
}
int code = NamingResponseCode.OK;
if (result.has(CommonParams.CODE)) {
code = result.get(CommonParams.CODE).asInt();
}
// 如果nacos server返回NOT FOUND则重新发起注册请求
if (code == NamingResponseCode.RESOURCE_NOT_FOUND) {
Instance instance = new Instance();
instance.setPort(beatInfo.getPort());
instance.setIp(beatInfo.getIp());
instance.setWeight(beatInfo.getWeight());
instance.setMetadata(beatInfo.getMetadata());
instance.setClusterName(beatInfo.getCluster());
instance.setServiceName(beatInfo.getServiceName());
instance.setInstanceId(instance.getInstanceId());
instance.setEphemeral(true);
try {
serverProxy.registerService(beatInfo.getServiceName(),
NamingUtils.getGroupName(beatInfo.getServiceName()), instance);
} catch (Exception ignore) {
}
}
} catch (NacosException ex) {
NAMING_LOGGER.error("[CLIENT-BEAT] failed to send beat: {}, code: {}, msg: {}",
JacksonUtils.toJson(beatInfo), ex.getErrCode(), ex.getErrMsg());
}
// 默认为5秒，可以通过PreservedMetadataKeys.HEART_BEAT_INTERVAL设置
executorService.schedule(new BeatTask(beatInfo), nextTime, TimeUnit.MILLISECONDS);
}
}
addBeatInfo调用时机，当节点在注册时如果实例为临时节点，则会创建心跳任务发起
public void registerService(String serviceName, String groupName, Instance instance) throws NacosException {
NAMING_LOGGER.info("[REGISTER-SERVICE] {} registering service {} with instance: {}", namespaceId, serviceName,instance);
String groupedServiceName = NamingUtils.getGroupedName(serviceName, groupName);
if (instance.isEphemeral()) {
BeatInfo beatInfo = beatReactor.buildBeatInfo(groupedServiceName, instance);
// 添加心跳任务
beatReactor.addBeatInfo(groupedServiceName, beatInfo);
}
final Map<String, String> params = new HashMap<String, String>(16);
params.put(CommonParams.NAMESPACE_ID, namespaceId);
params.put(CommonParams.SERVICE_NAME, groupedServiceName);
params.put(CommonParams.GROUP_NAME, groupName);
params.put(CommonParams.CLUSTER_NAME, instance.getClusterName());
params.put("ip", instance.getIp());
params.put("port", String.valueOf(instance.getPort()));
params.put("weight", String.valueOf(instance.getWeight()));
params.put("enable", String.valueOf(instance.isEnabled()));
params.put("healthy", String.valueOf(instance.isHealthy()));
params.put("ephemeral", String.valueOf(instance.isEphemeral()));
params.put("metadata", JacksonUtils.toJson(instance.getMetadata()));
reqApi(UtilAndComs.nacosUrlInstance, params, HttpMethod.POST);
}
再跟踪下注册入口，判读使用哪个ClientProxy
@Override
public void registerService(String serviceName, String groupName, Instance instance) throws NacosException {
getExecuteClientProxy(instance).registerService(serviceName, groupName, instance);
}
private NamingClientProxy getExecuteClientProxy(Instance instance) {
// 是否为临时节点，临时节点使用grpc，持久节点使用http；默认为true，也就是默认使用grpcClientProxy
return instance.isEphemeral() ? grpcClientProxy : httpClientProxy;
}
小结： HTTP心跳检测只适用于注册的节点持久节点，临时节点会使用grpc代理，即HTTP的心跳检测默认废弃由grpc替代；在初始化时客户端注册代理NamingClientProxy时，初始化了一个HTTP心跳器用于向Nacos Server发起心跳；在注册节点时通过向心跳执行器添加心跳任务addBeatInfo触发；心跳执行器通过每隔五秒中向Nacos Server发起HTTP请求，如果返回的server not found会向Nacos Server发起注册请求重新注册；
UDP接受服务端推送
@注解7.4.2 初始化PushReceiver用于接受nacos server信息推送，使用UDP协议。
public PushReceiver(ServiceInfoHolder serviceInfoHolder) {
try {
this.serviceInfoHolder = serviceInfoHolder;
this.udpSocket = new DatagramSocket();
this.executorService = new ScheduledThreadPoolExecutor(1, new ThreadFactory() {
@Override
public Thread newThread(Runnable r) {
Thread thread = new Thread(r);
thread.setDaemon(true);
thread.setName("com.alibaba.nacos.naming.push.receiver");
return thread;
}
});
this.executorService.execute(this);
} catch (Exception e) {
NAMING_LOGGER.error("[NA] init udp socket failed", e);
}
}
备注： PushReceiver实现Runnable接口，在构造方法中通过守护线程运行。
public void run() {
while (!closed) {
try {
// byte[] is initialized with 0 full filled by default
byte[] buffer = new byte[UDP_MSS];
DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
// 接受nacos server推送
udpSocket.receive(packet);
// 将推送内容转换为json字符串
String json = new String(IoUtils.tryDecompress(packet.getData()), UTF_8).trim();
NAMING_LOGGER.info("received push data: " + json + " from " + packet.getAddress().toString());
PushPacket pushPacket = JacksonUtils.toObj(json, PushPacket.class);
String ack;
// 推送类型服务信息（例如订阅实例的变更）会通知订阅者逻辑已在上篇分析
if ("dom".equals(pushPacket.type) || "service".equals(pushPacket.type)) {
serviceInfoHolder.processServiceInfo(pushPacket.data);
// send ack to server
ack = "{\"type\": \"push-ack\"" + ", \"lastRefTime\":\"" + pushPacket.lastRefTime + "\", \"data\":"
+ "\"\"}";
} else if ("dump".equals(pushPacket.type)) {
// dump data to server
ack = "{\"type\": \"dump-ack\"" + ", \"lastRefTime\": \"" + pushPacket.lastRefTime + "\", \"data\":"
+ "\"" + StringUtils.escapeJavaScript(JacksonUtils.toJson(serviceInfoHolder.getServiceInfoMap()))
+ "\"}";
} else {
// do nothing send ack only
ack = "{\"type\": \"unknown-ack\"" + ", \"lastRefTime\":\"" + pushPacket.lastRefTime
+ "\", \"data\":" + "\"\"}";
}
// 向Server发送ack消息
udpSocket.send(new DatagramPacket(ack.getBytes(UTF_8), ack.getBytes(UTF_8).length,
packet.getSocketAddress()));
} catch (Exception e) {
if (closed) {
return;
}
NAMING_LOGGER.error("[NA] error while receiving push data", e);
}
}
}
小结： Client通过UDP接受到nacos server推动的消息：@1如果推送的为服务信息通过processServiceInfo处理，逻辑见上篇；@2 如果dump类型，则客户端发送服务信息serviceInfoMap的ack信息到服务端。
HTTP重试次数
@注解7.4.3 client通过HTTP向Nacos Server请求的重试次数，默认为3次。可以通过「namingRequestDomainMaxRetryCount」指定
public String reqApi(String api, Map<String, String> params, Map<String, String> body, List<String> servers,
String method) throws NacosException {
// ...
if (serverListManager.isDomain()) {
String nacosDomain = serverListManager.getNacosDomain();
for (int i = 0; i < maxRetry; i++) { // 请求发送异常最大重试次数
try {
return callServer(api, params, body, nacosDomain, method);
} catch (NacosException e) {
exception = e;
if (NAMING_LOGGER.isDebugEnabled()) {
NAMING_LOGGER.debug("request {} failed.", nacosDomain, e);
}
}
}
}
//....
}
四、gRPC代理初始化
gRPC初始化逻辑概览
@注解7.5 下面接着gRPC 客户端代理的初始化逻辑
public NamingGrpcClientProxy(String namespaceId, SecurityProxy securityProxy, ServerListFactory serverListFactory,
Properties properties, ServiceInfoHolder serviceInfoHolder) throws NacosException {
super(securityProxy, properties);
this.namespaceId = namespaceId;
this.uuid = UUID.randomUUID().toString();
// 设置请求超时时间，默认为3秒。可以通过参数「namingRequestTimeout」设置
this.requestTimeout = Long.parseLong(properties.getProperty(CommonParams.NAMING_REQUEST_TIMEOUT, "-1"));
Map<String, String> labels = new HashMap<String, String>();
// 设置source=sdk，module=naming
labels.put(RemoteConstants.LABEL_SOURCE, RemoteConstants.LABEL_SOURCE_SDK);
labels.put(RemoteConstants.LABEL_MODULE, RemoteConstants.LABEL_MODULE_NAMING);
// 创建gRPC Client：clientName=uuid，ConnectionType=GRPC
this.rpcClient = RpcClientFactory.createClient(uuid, ConnectionType.GRPC, labels);
// 创建ConnectionEventListener用于建立和断开gRPC连接时的事件响应
this.namingGrpcConnectionEventListener = new NamingGrpcConnectionEventListener(this);
// 启动grpc client
start(serverListFactory, serviceInfoHolder);
}
private void start(ServerListFactory serverListFactory, ServiceInfoHolder serviceInfoHolder) throws NacosException {
rpcClient.serverListFactory(serverListFactory);
// @注解7.5.1 gRPC Client启动
rpcClient.start();
// 注册registerServerRequestHandler用于处理从Nacos Push到Client的请求
rpcClient.registerServerRequestHandler(new NamingPushRequestHandler(serviceInfoHolder));
// 注册连接事件Listener，当连接建立和断开时处理事件
rpcClient.registerConnectionListener(namingGrpcConnectionEventListener);
}
小结： gRPC 客户端代理的初始化主要逻辑为创建gRPC Client并启动；并注册ServerRequestHandler用于处理Nacos Server推送的NotifySubscriberRequest请求；注册ConnectionListener用于处理gRPC建立和断开连接事件；另外，请求超时时间可以通过「namingRequestTimeout」设置，默认为3秒。
gRPC Client启动逻辑
@注解7.5.1 gRPC Client启动逻辑
public final void start() throws NacosException {
// 将Client状态由INITIALIZED变更为STARTING
boolean success = rpcClientStatus.compareAndSet(RpcClientStatus.INITIALIZED, RpcClientStatus.STARTING);
if (!success) {
return;
}
// -------------------------@1 satart---------------------------------------------
// 守护线程执行器
clientEventExecutor = new ScheduledThreadPoolExecutor(2, new ThreadFactory() {
@Override
public Thread newThread(Runnable r) {
Thread t = new Thread(r);
t.setName("com.alibaba.nacos.client.remote.worker");
t.setDaemon(true);
return t;
}
});
// 从BlockingQueue中不断获取连接Event，根据事件类型回调onConnected()/onDisConnect()事件
clientEventExecutor.submit(new Runnable() {
@Override
public void run() {
while (true) {
ConnectionEvent take = null;
try {
take = eventLinkedBlockingQueue.take();
if (take.isConnected()) {
notifyConnected();
} else if (take.isDisConnected()) {
notifyDisConnected();
}
} catch (Throwable e) {
//Do nothing
}
}
}
});
// -------------------------@1 end---------------------------------------------
// -------------------------@2 start---------------------------------------------
clientEventExecutor.submit(new Runnable() {
@Override
public void run() {
while (true) {
try {
// 获取重定向连接上下文，指重新连接到其他server节点
ReconnectContext reconnectContext = reconnectionSignal
.poll(keepAliveTime, TimeUnit.MILLISECONDS);
if (reconnectContext == null) {
// check alive time.
// client活动时间超过5秒钟，向Nacos Server发起健康检测
if (System.currentTimeMillis() - lastActiveTimeStamp >= keepAliveTime) {
// 发送健康检查
boolean isHealthy = healthCheck();
// 非健康节点
if (!isHealthy) {
if (currentConnection == null) {
continue;
}
LoggerUtils.printIfInfoEnabled(LOGGER,
"[{}]Server healthy check fail,currentConnection={}", name,
currentConnection.getConnectionId());
// 标记客户端状态为unhealthy
rpcClientStatus.set(RpcClientStatus.UNHEALTHY);
// 重置ReconnectContext移除serverInfo
reconnectContext = new ReconnectContext(null, false);
} else {
// 健康连接更新时间戳
lastActiveTimeStamp = System.currentTimeMillis();
continue;
}
} else {
// 心跳保鲜未过期，跳过本次检测
continue;
}
}
if (reconnectContext.serverInfo != null) {
// clear recommend server if server is not in server list.
boolean serverExist = false;
// 判断连接上下文的reconnectContext.serverInfo是否在我们推荐设置的列表中
for (String server : getServerListFactory().getServerList()) {
ServerInfo serverInfo = resolveServerInfo(server);
if (serverInfo.getServerIp().equals(reconnectContext.serverInfo.getServerIp())) {
serverExist = true;
reconnectContext.serverInfo.serverPort = serverInfo.serverPort;
break;
}
}
// 不再推荐的列表中则移除，改为随机选择
if (!serverExist) {
LoggerUtils.printIfInfoEnabled(LOGGER,
"[{}] Recommend server is not in server list ,ignore recommend server {}", name,
reconnectContext.serverInfo.getAddress());
reconnectContext.serverInfo = null;
}
}
// 发起重新连接
reconnect(reconnectContext.serverInfo, reconnectContext.onRequestFail);
} catch (Throwable throwable) {
//Do nothing
}
}
}
});
// -------------------------@2 end---------------------------------------------
// -------------------------@3 start---------------------------------------------
// 异步连接nacos server失败，改为同步连接
//connect to server ,try to connect to server sync once, async starting if fail.
Connection connectToServer = null;
rpcClientStatus.set(RpcClientStatus.STARTING);
int startUpRetryTimes = RETRY_TIMES;
while (startUpRetryTimes > 0 && connectToServer == null) {
try {
startUpRetryTimes--;
ServerInfo serverInfo = nextRpcServer();
LoggerUtils.printIfInfoEnabled(LOGGER, "[{}] Try to connect to server on start up, server: {}", name,
serverInfo);
connectToServer = connectToServer(serverInfo);
} catch (Throwable e) {
LoggerUtils.printIfWarnEnabled(LOGGER,
"[{}]Fail to connect to server on start up, error message={}, start up retry times left: {}",
name, e.getMessage(), startUpRetryTimes);
}
}
// -------------------------@3 end---------------------------------------------
// -------------------------@4 start---------------------------------------------
if (connectToServer != null) {
LoggerUtils.printIfInfoEnabled(LOGGER, "[{}] Success to connect to server [{}] on start up,connectionId={}",name, connectToServer.serverInfo.getAddress(),connectToServer.getConnectionId());
this.currentConnection = connectToServer;
rpcClientStatus.set(RpcClientStatus.RUNNING);
// 连接成功添加ConnectionEvent
eventLinkedBlockingQueue.offer(new ConnectionEvent(ConnectionEvent.CONNECTED));
} else {
// 未成功建立连接重新发起异步建立连接需求
switchServerAsync();
}
// 注册ConnectResetRequestHandler用于处理nacos server推送的重置连接请求
registerServerRequestHandler(new ConnectResetRequestHandler());
//register client detection request.
registerServerRequestHandler(new ServerRequestHandler() {
@Override
public Response requestReply(Request request) {
if (request instanceof ClientDetectionRequest) {
return new ClientDetectionResponse();
}
return null;
}
});
Runtime.getRuntime().addShutdownHook(new Thread() {
@Override
public void run() {
try {
RpcClient.this.shutdown();
} catch (NacosException e) {
LoggerUtils.printIfErrorEnabled(LOGGER, "[{}]RpcClient shutdown exception, errorMessage ={}", name,
e.getMessage());
}
}
});
// -------------------------@4 end---------------------------------------------
}
备注： grpc client启动时的逻辑：逻辑块@1 守护线程不断从阻塞队列eventLinkedBlockingQueue获取grpc连接/断开事件，并调用上文中注册的namingGrpcConnectionEventListener回调其onConnected/onDisConnect方法。其中事件添加时机为：
grpc连接建立时，添加连接事件：
// 连接成功添加ConnectionEvent
eventLinkedBlockingQueue.offer(new ConnectionEvent(ConnectionEvent.CONNECTED));
grpc连接关闭时，添加关闭事件：
private void closeConnection(Connection connection) {
if (connection != null) {
connection.close();
// 断开连接添加DISCONNECTED事件
eventLinkedBlockingQueue.add(new ConnectionEvent(ConnectionEvent.DISCONNECTED));
}
}
逻辑块@2 守护线程不断从阻塞队列reconnectionSignal获取重新连接事件（ReconnectContext）也就是更换nacos server的连接grpc通道：
阻塞队列没有重新连接事件：则做心跳保鲜检测，心跳频率为5秒。当超过5秒时会向Nacos Server发起健康检查，当返回不健康时，将grpc client标记为unhealthy；返回健康则刷新心跳时间lastActiveTimeStamp。
阻塞队列有重新连接事件：重连事件上下文reconnectContext的的server ip在我们设置的nacos server 列表则使用，否则改为随机选择nacos server ip地址，并与新server建立连接。
protected void reconnect(final ServerInfo recommendServerInfo, boolean onRequestFail) {
try {
AtomicReference<ServerInfo> recommendServer = new AtomicReference<ServerInfo>(recommendServerInfo);
// onRequestFail=true表示当健康检查失败grpcClient被设置为unhealthy，重连时重新发起健康检查，如果检查通过则不再执行重连
if (onRequestFail && healthCheck()) {
LoggerUtils.printIfInfoEnabled(LOGGER, "[{}] Server check success,currentServer is{} ", name,
currentConnection.serverInfo.getAddress());
rpcClientStatus.set(RpcClientStatus.RUNNING);
return;
}
LoggerUtils.printIfInfoEnabled(LOGGER, "[{}] try to re connect to a new server ,server is {}", name,
recommendServerInfo == null ? " not appointed,will choose a random server."
: (recommendServerInfo.getAddress() + ", will try it once."));
// loop until start client success.
boolean switchSuccess = false;
int reConnectTimes = 0;
int retryTurns = 0;
Exception lastException = null;
// 切换nacos server没有成功则会一直重试
while (!switchSuccess && !isShutdown()) {
//1.get a new server
ServerInfo serverInfo = null;
try {
// 获取需要重新连接的server地址
serverInfo = recommendServer.get() == null ? nextRpcServer() : recommendServer.get();
//2.create a new channel to new server
// 与新的server建立grpc连接，如果连接失败返回null
Connection connectionNew = connectToServer(serverInfo);
// 关闭缓存的当前连接并重定向到新的连接
if (connectionNew != null) {
LoggerUtils.printIfInfoEnabled(LOGGER, "[{}] success to connect a server [{}],connectionId={}",
name, serverInfo.getAddress(), connectionNew.getConnectionId());
//successfully create a new connect.
if (currentConnection != null) {
LoggerUtils.printIfInfoEnabled(LOGGER,"[{}] Abandon prev connection ,server is {}, connectionId is {}", name,currentConnection.serverInfo.getAddress(), currentConnection.getConnectionId());
//set current connection to enable connection event.
currentConnection.setAbandon(true);
closeConnection(currentConnection);
}
currentConnection = connectionNew;
rpcClientStatus.set(RpcClientStatus.RUNNING);
switchSuccess = true;
// 添加连接成功时间到阻塞队列
boolean s = eventLinkedBlockingQueue.add(new ConnectionEvent(ConnectionEvent.CONNECTED));
return;
}
//close connection if client is already shutdown.
if (isShutdown()) {
closeConnection(currentConnection);
}
lastException = null;
} catch (Exception e) {
lastException = e;
} finally {
// 清理本次重连请求
recommendServer.set(null);
}
// 执行到这里表示上面没有成功建立连接，打印重试次数日志
if (reConnectTimes > 0
&& reConnectTimes % RpcClient.this.serverListFactory.getServerList().size() == 0) {
LoggerUtils.printIfInfoEnabled(LOGGER,"[{}] fail to connect server,after trying {} times, last try server is {},error={}", name,reConnectTimes, serverInfo, lastException == null ? "unknown" : lastException);
if (Integer.MAX_VALUE == retryTurns) {
retryTurns = 50;
} else {
retryTurns++;
}
}
reConnectTimes++;
// 重试时等待特定的时间
try {
//sleep x milliseconds to switch next server.
if (!isRunning()) {
// first round ,try servers at a delay 100ms;second round ,200ms; max delays 5s. to be reconsidered.
Thread.sleep(Math.min(retryTurns + 1, 50) * 100L);
}
} catch (InterruptedException e) {
// Do nothing.
}
}
if (isShutdown()) {
LoggerUtils.printIfInfoEnabled(LOGGER, "[{}] Client is shutdown ,stop reconnect to server", name);
}
} catch (Exception e) {
LoggerUtils.printIfWarnEnabled(LOGGER, "[{}] Fail to re connect to server ,error is {}", name, e);
}
}
备注： 重新切换连接server逻辑：@1当检查失败grpc client会被标记为unhealthy这类型onRequestFail为true，重连时重新发起健康检查，如果检查成功，则退出本次重连。@2 获取重连的server地址和端口，并建立grpc连接，关闭当前缓存的旧连接并重定向到新连接，同时添加连接成功时间到阻塞队列。@3 一直重试直到连接建立成功，每次重试等待一些时间（100ms,200ms...最大为5秒）。
逻辑块@3 当异步与nacos server建立失败时，改为尝试同步建立连接。
逻辑块@4 如果连接建立成功添加连接事件到阻塞队列；连接建立失败发起异步建立连接请求；注册ConnectResetRequestHandler用于处理nacos server推送的重置连接请求；jvm退出时通过hook关闭grpc client。
小结： gRPC Client启动逻辑主要在于建立与nacos server的grpc连接，其中两个守护线程一直在运行。一个用于处理grpc连接的建立和关闭事件；一个用于与nacos server的心跳保鲜，并负责异步建立grpc连接，当nacos server的地址信息发生变更时负责重新与新server建立连接；grpc client只与nacos server集群中一台建立grpc连接。
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原始发表：2021-05-23，如有侵权请联系 cloudcommunity@tencent.com 删除
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