背景
远程调用一般都会用ribbon，尽管使用feign，还是用的ribbon做的负载均衡，远程调用。但是ribbon会每隔30s刷新注册表信息，这样就会导致如果服务下线了，由于注册表没有及时更新，那远程调用就会报错。我们看下默认ribbon实现。
- com.netflix.loadbalancer.PollingServerListUpdater 这个类是ribbon更新注册表的核心类。
nacos 动态更新地址原理
Nacos客户端中有一个HostReactor类，它的功能是实现服务的动态更新，基本原理是：
- 客户端发起时间订阅后，在HostReactor中有一个UpdateTask线程，每10s发送一次Pull请求，获得服务端最新的地址列表
- 对于服务端，它和服务提供者的实例之间维持了心跳检测，一旦服务提供者出现异常，则会发送一个Push消息给Nacos客户端，也就是服务端消费者
- 服务消费者收到请求之后，使用HostReactor中提供的processServiceJSON解析消息，并更新本地服务地址列表
改造ribbon默认更新策略
基于上面的理论，是不是可以监听nacos事件更新事件，如果有更新，就重新刷新下ribbon的注册表。
- 覆盖
ServerListUpdater,自己定义一个NacosDynamicServerListUpdater代码如下；
public class NacosDynamicServerListUpdater implements ServerListUpdater {
private static Logger log = LoggerFactory.getLogger(NacosDynamicServerListUpdater.class);
private CopyOnWriteArrayList<LBUpdater> lbUpdaters = new CopyOnWriteArrayList();
private NamingService namingService;
@Value("${ribbon.PollingServerListUpdater.initial-delay:1000}")
private long initialDelay;
@Value("${ribbon.PollingServerListUpdater.refresh-interval:30000}")
private long refreshInterval;
private NacosDiscoveryProperties properties;
public NacosDynamicServerListUpdater(NamingService namingService, NacosDiscoveryProperties properties) {
this.namingService = namingService;
this.properties = properties;
}
@Override
public void start(UpdateAction updateAction) {
NacosDynamicServerListUpdater.LBUpdater lbUpdater = new NacosDynamicServerListUpdater.LBUpdater(updateAction);
this.lbUpdaters.add(lbUpdater);
lbUpdater.start();
log.info("nacos dslu-started: {}, lbUpdater: {}, PollingServerListUpdater: initialDelay={}, refreshInterval={}",
new Object[]{
this, lbUpdater.getIdentity(), this.initialDelay, this.refreshInterval});
}
@Override
public void stop() {
log.info("nacos dslu-stopped: {}", this);
Iterator iterator = this.lbUpdaters.iterator();
while (iterator.hasNext()) {
NacosDynamicServerListUpdater.LBUpdater lbUpdater = (NacosDynamicServerListUpdater.LBUpdater) iterator.next();
try {
lbUpdater.stop();
} catch (Exception var4) {
log.error("nacos dslu-stop-lbUpdater: " + lbUpdater.getIdentity(), var4);
}
}
}
@Override
public String getLastUpdate() {
return null;
}
@Override
public long getDurationSinceLastUpdateMs() {
return 0;
}
@Override
public int getNumberMissedCycles() {
return 0;
}
@Override
public int getCoreThreads() {
return 0;
}
class LBUpdater {
Logger log = LoggerFactory.getLogger(NacosDynamicServerListUpdater.LBUpdater.class);
private String serviceId;
private volatile UpdateAction updateAction;
private volatile BaseLoadBalancer lb;
private NacosDynamicServerListWatcher nacosWatcher;
private PollingServerListUpdater pollingServerListUpdater;
private String identity;
public LBUpdater(UpdateAction updateAction) {
this.updateAction = updateAction;
this.lb = this.getLoadBalancer(updateAction);
this.serviceId = this.lb.getClientConfig().getClientName();
this.pollingServerListUpdater = new PollingServerListUpdater(NacosDynamicServerListUpdater.this.initialDelay, NacosDynamicServerListUpdater.this.refreshInterval);
this.nacosWatcher = new NacosDynamicServerListWatcher(NacosDynamicServerListUpdater.this.namingService, NacosDynamicServerListUpdater.this.properties, this);
}
public void start() {
this.pollingServerListUpdater.start(this.updateAction);
this.nacosWatcher.startWatch();
}
private BaseLoadBalancer getLoadBalancer(UpdateAction updateAction) {
try {
Class<?> bc = updateAction.getClass();
Field field = bc.getDeclaredField("this$0");
field.setAccessible(true);
return (BaseLoadBalancer) field.get(updateAction);
} catch (Exception var4) {
this.log.error("nacos dslu-getlb", var4);
throw new IllegalStateException("Not supported LB used", var4);
}
}
public String getServiceId() {
return this.serviceId;
}
public UpdateAction getUpdateAction() {
return this.updateAction;
}
public BaseLoadBalancer getLb() {
return this.lb;
}
public PollingServerListUpdater getPollingServerListUpdater() {
return this.pollingServerListUpdater;
}
public NacosDynamicServerListWatcher getNacosWatcher() {
return nacosWatcher;
}
public String getIdentity() {
if (this.identity == null) {
this.identity = String.format("{serviceId: %s, lb: %s, updateAction: %s}", this.getServiceId(), this.getLb().hashCode(), this.getUpdateAction().hashCode());
}
return this.identity;
}
public void stop() {
try {
this.nacosWatcher.stop();
} catch (Exception e) {
this.log.error("nacos dslu-stop-watcher: " + this.getIdentity(), e);
}
this.pollingServerListUpdater.stop();
}
public void doUpdate() {
this.getUpdateAction().doUpdate();
this.log.info("nacos dslu-doUpdate: {}", this.getIdentity());
this.serviceLog();
}
private void serviceLog() {
List<Server> backwardList = this.getLb().getAllServers();
StringBuilder serviceLog = new StringBuilder("");
Iterator iterator = backwardList.iterator();
while (iterator.hasNext()) {
Server service = (Server) iterator.next();
serviceLog.append(service.getHost());
serviceLog.append(":");
serviceLog.append(service.getPort());
serviceLog.append(",");
}
this.log.info("[nacos dslu-LbServerList] [{}].{}", serviceLog, this.getIdentity());
}
}
}
- 定义一个nacos的监听类
NacosDynamicServerListWatcher，用于监听更新事件
public class NacosDynamicServerListWatcher {
private static Logger log = LoggerFactory.getLogger(NacosDynamicServerListWatcher.class);
private NamingService namingService;
private final NacosDiscoveryProperties properties;
private NacosDynamicServerListUpdater.LBUpdater lbUpdater;
public NacosDynamicServerListWatcher(NamingService namingService, NacosDiscoveryProperties properties, NacosDynamicServerListUpdater.LBUpdater lbUpdater) {
this.namingService = namingService;
this.properties = properties;
this.lbUpdater = lbUpdater;
}
public void startWatch() {
log.info("nacos dslw-start: {}, serviceName: {}", this.lbUpdater.getIdentity(), lbUpdater.getServiceId());
try {
namingService.subscribe(lbUpdater.getServiceId(), Arrays.asList(properties.getClusterName()), event -> {
if (event instanceof NamingEvent) {
NamingEvent namingEvent = (NamingEvent) event;
System.out.println("服务名：" + namingEvent.getServiceName());
System.out.println("实例：" + namingEvent.getInstances());
lbUpdater.doUpdate();
}
});
} catch (NacosException e) {
e.printStackTrace();
}
}
public void stop() {
}
}
- 定义配置类，让springboot启动时自动加载
@Configuration
@ConditionalOnRibbonNacos
public class NacosDynamicServerListConfiguration {
@Bean
public NacosDynamicServerListUpdater dynamicServerListUpdater(NacosDiscoveryProperties properties) throws NacosException {
return new NacosDynamicServerListUpdater(NacosFactory.createNamingService(properties.getServerAddr()), properties);
}
}
- 修改
spring.factories
测试
- 启动
service-feign、service-hi服务 - 关闭
service-hi服务可以看到如下日志：
