Service address dynamic awareness of Nacos registry

nacos The service address of the registry is dynamically aware

Service consumers not only need to get the address list of service providers , You also need to listen for changes in the service address when exceptions occur in the service instance .

First of all, how to realize the monitoring of services ？ There are two ways to implement service monitoring .

Implement monitoring

call subscribe Method

By calling subscribe Method to realize monitoring ,serviceName For service name ,EventListener For the monitored events .

NamingService Interface subscribe Method ：

void subscribe(String serviceName, EventListener listener) throws NacosException;


The specific calling method is as follows ：

NamingService naming2 = NamingFactory.createNamingService("127.0.0.1" + ":" + port);

naming2.subscribe(serviceName, new EventListener() {
 @Override
 public void onEvent(Event event) {
 System.out.println(((NamingEvent) event).getServiceName());
 System.out.println(((NamingEvent) event).getInstances());
 instances = ((NamingEvent) event).getInstances();
 }
});


call selectInstances Method

NamingService Interface selectInstances Method ：

List<Instance> selectInstances(String serviceName, String groupName, List<String> clusters, boolean healthy, boolean subscribe) throws NacosException;


If subscribe by true, Will automatically register to listen .

selectInstances(serviceName, clusters, healthy, true)


Principle of service dynamic perception

Principle of service dynamic perception ：

nacos There is HostReactor class , It is used to realize the dynamic update of services ：

• After the client initiates the event subscription ,HostReactor There is UpdateTask Threads , Every time 10s Send it once Pull request , Get the latest address list of the server

• Heartbeat detection is maintained between the server and the instance of the service provider , Once the service provider has an exception , Will send a Push A message to Nacos client , That is to serve consumers

• After the service consumer receives the request , Use HostReactor Of processServiceJSON Method parses the message , Update local service address list .

This is it. nacos The basic information of dynamic perception of registry service address , I hope that's helpful , If you have any questions, you can also leave me comments .

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